Voltage Controlled Hot Carrier Injection Enables Ohmic Contacts Using Au Island Metal Films on Ge.

PubMed

Ganti, Srinivas; King, Peter J; Arac, Erhan; Dawson, Karl; Heikkilä, Mikko J; Quilter, John H; Murdoch, Billy; Cumpson, Peter; O'Neill, Anthony

2017-08-23

We introduce a new approach to creating low-resistance metal-semiconductor ohmic contacts, illustrated using high conductivity Au island metal films (IMFs) on Ge, with hot carrier injection initiated at low applied voltage. The same metallization process simultaneously allows ohmic contact to n-Ge and p-Ge, because hot carriers circumvent the Schottky barrier formed at metal/n-Ge interfaces. A 2.5× improvement in contact resistivity is reported over previous techniques to achieve ohmic contact to both n- and p- semiconductor. Ohmic contacts at 4.2 K confirm nonequilibrium current transport. Self-assembled Au IMFs are strongly orientated to Ge by annealing near the Au/Ge eutectic temperature. Au IMF nanostructures form, provided the Au layer is below a critical thickness. We anticipate that optimized IMF contacts may have applicability to many material systems. Optimizing this new paradigm for metal-semiconductor contacts offers the prospect of improved nanoelectronic systems and the study of voltage controlled hot holes and electrons.

Seeded Growth Synthesis of Gold Nanotriangles: Size Control, SAXS Analysis, and SERS Performance.

PubMed

Kuttner, Christian; Mayer, Martin; Dulle, Martin; Moscoso, Ana; López-Romero, Juan Manuel; Förster, Stephan; Fery, Andreas; Pérez-Juste, Jorge; Contreras-Cáceres, Rafael

2018-04-04

We studied the controlled growth of triangular prismatic Au nanoparticles with different beveled sides for surface-enhanced Raman spectroscopy (SERS) applications. First, in a seedless synthesis using 3-butenoic acid (3BA) and benzyldimethylammonium chloride (BDAC), gold nanotriangles (AuNTs) were synthesized in a mixture with gold nanooctahedra (AuNOCs) and separated by depletion-induced flocculation. Here, the influence of temperature, pH, and reducing agent on the reaction kinetics was initially investigated by UV-vis and correlated to the size and yield of AuNT seeds. In a second step, the AuNT size was increased by seed-mediated overgrowth with Au. We show for the first time that preformed 3BA-synthesized AuNT seeds can be overgrown up to a final edge length of 175 nm and a thickness of 80 nm while maintaining their triangular shape and tip sharpness. The NT morphology, including edge length, thickness, and tip rounding, was precisely characterized in dispersion by small-angle X-ray scattering and in dry state by transmission electron microscopy and field-emission scanning electron microscopy. For sensor purposes, we studied the size-dependent SERS performance of AuNTs yielding analytical enhancement factors between 0.9 × 10 4 and 5.6 × 10 4 and nanomolar limit of detection (10 -8 -10 -9 M) for 4-mercaptobenzoic acid and BDAC. These results confirm that the 3BA approach allows the fabrication of AuNTs in a whole range of sizes maintaining the NT morphology. This enables tailoring of localized surface plasmon resonances between 590 and 740 nm, even in the near-infrared window of a biological tissue, for use as colloidal SERS sensing agents or for optoelectronic applications.

Dominance of Plasmonic Resonant Energy Transfer over Direct Electron Transfer in Substantially Enhanced Water Oxidation Activity of BiVO4 by Shape-Controlled Au Nanoparticles.

PubMed

Lee, Mi Gyoung; Moon, Cheon Woo; Park, Hoonkee; Sohn, Woonbae; Kang, Sung Bum; Lee, Sanghan; Choi, Kyoung Jin; Jang, Ho Won

2017-10-01

The performance of plasmonic Au nanostructure/metal oxide heterointerface shows great promise in enhancing photoactivity, due to its ability to confine light to the small volume inside the semiconductor and modify the interfacial electronic band structure. While the shape control of Au nanoparticles (NPs) is crucial for moderate bandgap semiconductors, because plasmonic resonance by interband excitations overlaps above the absorption edge of semiconductors, its critical role in water splitting is still not fully understood. Here, first, the plasmonic effects of shape-controlled Au NPs on bismuth vanadate (BiVO 4 ) are studied, and a largely enhanced photoactivity of BiVO 4 is reported by introducing the octahedral Au NPs. The octahedral Au NP/BiVO 4 achieves 2.4 mA cm -2 at the 1.23 V versus reversible hydrogen electrode, which is the threefold enhancement compared to BiVO 4 . It is the highest value among the previously reported plasmonic Au NPs/BiVO 4 . Improved photoactivity is attributed to the localized surface plasmon resonance; direct electron transfer (DET), plasmonic resonant energy transfer (PRET). The PRET can be stressed over DET when considering the moderate bandgap semiconductor. Enhanced water oxidation induced by the shape-controlled Au NPs is applicable to moderate semiconductors, and shows a systematic study to explore new efficient plasmonic solar water splitting cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Atomic force microscopy investigation of the kinetic growth mechanisms of sputtered nanostructured Au film on mica: towards a nanoscale morphology control

PubMed Central

2011-01-01

The study of surface morphology of Au deposited on mica is crucial for the fabrication of flat Au films for applications in biological, electronic, and optical devices. The understanding of the growth mechanisms of Au on mica allows to tune the process parameters to obtain ultra-flat film as suitable platform for anchoring self-assembling monolayers, molecules, nanotubes, and nanoparticles. Furthermore, atomically flat Au substrates are ideal for imaging adsorbate layers using scanning probe microscopy techniques. The control of these mechanisms is a prerequisite for control of the film nano- and micro-structure to obtain materials with desired morphological properties. We report on an atomic force microscopy (AFM) study of the morphology evolution of Au film deposited on mica by room-temperature sputtering as a function of subsequent annealing processes. Starting from an Au continuous film on the mica substrate, the AFM technique allowed us to observe nucleation and growth of Au clusters when annealing process is performed in the 573-773 K temperature range and 900-3600 s time range. The evolution of the clusters size was quantified allowing us to evaluate the growth exponent 〈z〉 = 1.88 ± 0.06. Furthermore, we observed that the late stage of cluster growth is accompanied by the formation of circular depletion zones around the largest clusters. From the quantification of the evolution of the size of these zones, the Au surface diffusion coefficient was evaluated in D(T) = [(7.42 × 10−13) ± (5.94 × 10−14) m2/s]exp(−(0.33±0.04) eVkT). These quantitative data and their correlation with existing theoretical models elucidate the kinetic growth mechanisms of the sputtered Au on mica. As a consequence we acquired a methodology to control the morphological characteristics of the Au film simply controlling the annealing temperature and time. PMID:24576328

Controlled growth of hexagonal gold nanostructures during thermally induced self-assembling on Ge(001) surface

PubMed Central

Jany, B. R.; Gauquelin, N.; Willhammar, T.; Nikiel, M.; van den Bos, K. H. W.; Janas, A.; Szajna, K.; Verbeeck, J.; Van Aert, S.; Van Tendeloo, G.; Krok, F.

2017-01-01

Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. Gold crystallizes in the face-centered cubic (fcc) phase, and its hexagonal closed packed (hcp) structure is a very unusual and rare phase. Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium. PMID:28195226

Controlled growth of hexagonal gold nanostructures during thermally induced self-assembling on Ge(001) surface

NASA Astrophysics Data System (ADS)

Jany, B. R.; Gauquelin, N.; Willhammar, T.; Nikiel, M.; van den Bos, K. H. W.; Janas, A.; Szajna, K.; Verbeeck, J.; van Aert, S.; van Tendeloo, G.; Krok, F.

2017-02-01

Nano-sized gold has become an important material in various fields of science and technology, where control over the size and crystallography is desired to tailor the functionality. Gold crystallizes in the face-centered cubic (fcc) phase, and its hexagonal closed packed (hcp) structure is a very unusual and rare phase. Stable Au hcp phase has been reported to form in nanoparticles at the tips of some Ge nanowires. It has also recently been synthesized in the form of thin graphene-supported sheets which are unstable under electron beam irradiation. Here, we show that stable hcp Au 3D nanostructures with well-defined crystallographic orientation and size can be systematically created in a process of thermally induced self-assembly of thin Au layer on Ge(001) monocrystal. The Au hcp crystallite is present in each Au nanostructure and has been characterized by different electron microscopy techniques. We report that a careful heat treatment above the eutectic melting temperature and a controlled cooling is required to form the hcp phase of Au on a Ge single crystal. This new method gives scientific prospects to obtain stable Au hcp phase for future applications in a rather simple manner as well as redefine the phase diagram of Gold with Germanium.

Gold nanoparticles-decorated fluoroalkylsilane nano-assemblies for electrocatalytic applications

NASA Astrophysics Data System (ADS)

Ballarin, Barbara; Barreca, Davide; Cassani, Maria Cristina; Carraro, Giorgio; Maccato, Chiara; Mignani, Adriana; Lazzari, Dario; Bertola, Maurizio

2016-01-01

Metal/organosilane/oxide sandwich structures were prepared via a two-step self-assembly method. First, indium tin oxide (ITO) substrates were functionalized with the following fluoroalkylsilanes (FAS): RFC(O)N(H)(CH2)3Si(OMe)3 (1, RF = C5F11), containing an embedded amide between the perfluoroalkyl chain and the syloxanic moiety, and RF(CH2)2Si(OEt)3 (2, RF = C6F13). Subsequently, Au nanoparticles (AuNPs) introduction in the obtained systems was carried out by controlled immersion into a solution of citrate-stabilized AuNPs. The physico-chemical properties of the target materials were thoroughly investigated by using various complementary techniques. Finally, the application of such systems as catalysts for methanol electro-oxidation under alkaline conditions was investigated, revealing the synergistical role played by FAS and AuNPs in promoting a remarkable electrocatalytic activity.

Vesicular gold assemblies based on host-guest inclusion and its controllable release of doxorubicin

NASA Astrophysics Data System (ADS)

Ha, Wei; Kang, Yang; Peng, Shu-Lin; Ding, Li-Sheng; Zhang, Sheng; Li, Bang-Jing

2013-12-01

We have developed a kind of gold nanoparticle (AuNP) in which polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) are attached on the surface of a gold nanocrystal through the host-guest inclusion between adamantane groups (ADA) and β-cyclodextrin (β-CD). The resulting AuNPs become amphiphilic in water above body temperature and self-assemble into vesicles. It is found that these vesicles can load doxorubicin (Dox) effectively. With a decrease in temperature, the PNIPAM shifted from hydrophobic to hydrophilic, causing Au vesicles to disassemble into stable small AuNPs, triggering the release of Dox. These hybrid vesicles, combining polymer functionality with the intriguing properties of AuNPs, can first release free Dox and AuNP/Dox at a site of a tumor through the application of either simple ice packs or deeply penetrating cryoprobes, then the AuNP/Dox can be taken in by tumor cells and destroy them like miniature munitions. Furthermore, these vesicles showed other therapeutic possibilities due to the presence of gold. We believe that the development of such multi-functional vesicles will provide new and therapeutically useful means for medical applications.

Kinetically controlled synthesis of Au102(SPh)44 nanoclusters and catalytic application.

PubMed

Chen, Yongdong; Wang, Jin; Liu, Chao; Li, Zhimin; Li, Gao

2016-05-21

We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au102(SPh)44 nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S([double bond, length as m-dash]O)-R' sulfoxides). The Au102(SPh)44/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process.

Use of structural geology in exploration for and mining of sedimentary rock-hosted Au deposits

USGS Publications Warehouse

Peters, Stephen G.

2001-01-01

Structural geology is an important component in regional-, district- and orebody-scale exploration and development of sedimentary rock-hosted Au deposits.Identification of timing of important structural events in an ore district allows analysis and classification of fluid conduits and construction of genetic models for ore formation.The most practical uses of structural geology deal with measurement and definition of various elements that comprise orebodies, which can then be directly applied to ore-reserve estimation,ground control,grade control, safety issues,and mine planning.District- and regional-scale structural studies are directly applicable to long-term strategic planning,economic analysis,and land ownership. Orebodies in sedimentary rock-hosted Au deposits are discrete, hypogene, epigenetic masses usually hosted in a fault zone,breccia mass, or lithologic bed or unit. These attributes allow structural geology to be directly applied to the mining and exploration of sedimentary rock-hosted Au deposits. Internal constituents in orebodies reflect unique episodes relating to ore formation.The main internal constituents in orebodies are ore minerals, gangue, and alteration minerals that usually are mixed with one another in complex patterns, the relations among which may be used to interpret the processes of orebody formation and control.Controls of orebody location and shape usually are due to structural dilatant zones caused by changes in attitude, splays, lithologic contacts,and intersections of the host conduit or unit.In addition,conceptual parameters such as district fabric,predictable distances, and stacking also are used to understand the geometry of orebodies.Controls in ore districts and location and geometry of orebodies in ore districts can be predicted to various degrees by using a number of qualitative concepts such as internal and external orebody plunges,district plunge, district stacking, conduit classification, geochemical, geobarometric and geothermal gradients, and tectonic warps. These concepts have practical and empirical application in most mining districts where they are of use in the exploration for ore, but are of such broad and general application that they may not represent known or inferred ore formation processes. Close spatial relation among some sedimentary rock- hosted Au deposits and their host structures suggests that the structures and the orebodies are genetically linked because they may have shared the same developmental history. Examples of probable syn-deformational genesis and structural control of sedimentary rock-hosted Au deposits are in the large Betze deposit in the Carlin trend, Nevada and in the Lannigou, Jinlongshan, and Maanqiao Au deposits, China.

A dewetting route to grow heterostructured nanoparticles based on thin film heterojunctions.

PubMed

Li, Junjie; Yin, Deqiang; Li, Qiang; Chen, Chunlin; Huang, Sumei; Wang, Zhongchang

2015-12-21

Heterostructured nanoparticles have received considerable attention for their various applications due to their unique and tunable functionalities with respect to their individual bulk constituents. However, the current wet chemical synthesis of multicomponent heterostructured nanoparticles is rather complicated. Here, we report a simple and quick method to fabricate Co-Au dumbbell arrays by dewetting Co/Au heterojunctions on a Si substrate and demonstrate that the Co-Au dumbbells vary in size from 2 to 28 nm. We further show by chemical mapping that Co bells are covered by a pseudomorphic Au wetting layer of ∼4 Å, preventing the bells from oxidation. By controlling the thickness of metal heterojunctions and the annealing time, the morphology of the Co-Au nanoparticle is found to be transformed from the dumbbell to the core shell. This facile route is demonstrated to be useful for fabricating other metal-metal and metal-oxide heterostructures and hence holds technological promise for functional applications.

Manipulation of Spin-Torque Generation Using Ultrathin Au

NASA Astrophysics Data System (ADS)

An, Hongyu; Haku, Satoshi; Kanno, Yusuke; Nakayama, Hiroyasu; Maki, Hideyuki; Shi, Ji; Ando, Kazuya

2018-06-01

The generation and the manipulation of current-induced spin-orbit torques are of essential interest in spintronics. However, in spite of the vital progress in spin orbitronics, electric control of the spin-torque generation still remains elusive and challenging. We report on electric control of the spin-torque generation using ionic-liquid gating of ultrathin Au. We show that by simply depositing a SiO2 capping layer on an ultrathin-Au /Ni81Fe19 bilayer, the spin-torque generation efficiency is drastically enhanced by a maximum of 7 times. This enhancement is verified to be originated from the rough ultrathin-Au /Ni81Fe19 interface induced by the SiO2 deposition, which results in the enhancement of the interface spin-orbit scattering. We further show that the spin-torque generation efficiency from the ultrathin Au film can be reversibly manipulated by a factor of 2 using the ionic gating with an external electric field within a small range of 1 V. These results pave a way towards the efficient control of the spin-torque generation in spintronic applications.

Multifunctional Au-Fe3O4@MOF core-shell nanocomposite catalysts with controllable reactivity and magnetic recyclability

NASA Astrophysics Data System (ADS)

Ke, Fei; Wang, Luhuan; Zhu, Junfa

2014-12-01

The recovery and reuse of expensive catalysts are important in both heterogeneous and homogeneous catalysis due to economic and environmental reasons. This work reports a novel multifunctional magnetic core-shell gold catalyst which can be easily prepared and shows remarkable catalytic properties in the reduction of 4-nitrophenol. The novel Au-Fe3O4@metal-organic framework (MOF) catalyst consists of a superparamagnetic Au-Fe3O4 core and a porous MOF shell with controllable thickness. Small Au nanoparticles (NPs) of 3-5 nm are mainly sandwiched between the Fe3O4 core and the porous MOF shell. Catalytic studies show that the core-shell structured Au-Fe3O4@MOF catalyst has a much higher catalytic activity than other reported Au-based catalysts toward the reduction of 4-nitrophenol. Moreover, this catalyst can be easily recycled due to the presence of the superparamagnetic core. Therefore, compared to conventional catalysts used in the reduction of 4-nitrophenol, this porous MOF-based magnetic catalyst is green, cheap and promising for industrial applications.The recovery and reuse of expensive catalysts are important in both heterogeneous and homogeneous catalysis due to economic and environmental reasons. This work reports a novel multifunctional magnetic core-shell gold catalyst which can be easily prepared and shows remarkable catalytic properties in the reduction of 4-nitrophenol. The novel Au-Fe3O4@metal-organic framework (MOF) catalyst consists of a superparamagnetic Au-Fe3O4 core and a porous MOF shell with controllable thickness. Small Au nanoparticles (NPs) of 3-5 nm are mainly sandwiched between the Fe3O4 core and the porous MOF shell. Catalytic studies show that the core-shell structured Au-Fe3O4@MOF catalyst has a much higher catalytic activity than other reported Au-based catalysts toward the reduction of 4-nitrophenol. Moreover, this catalyst can be easily recycled due to the presence of the superparamagnetic core. Therefore, compared to conventional catalysts used in the reduction of 4-nitrophenol, this porous MOF-based magnetic catalyst is green, cheap and promising for industrial applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr05421k

Bonding properties of FCC-like Au 44 (SR) 28 clusters from X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Rui; Chevrier, Daniel M.; Zeng, Chenjie

Thiolate-protected gold clusters with precisely controlled atomic composition have recently emerged as promising candidates for a variety of applications because of their unique optical, electronic, and catalytic properties. The recent discovery of the Au44(SR)28 total structure is considered as an interesting finding in terms of the face-centered cubic (FCC)-like core structure in small gold-thiolate clusters. Herein, the unique bonding properties of Au44(SR)28 is analyzed using temperature-dependent X-ray absorption spectroscopy (XAS) measurements at the Au L3-edge and compared with other FCC-like clusters such as Au36(SR)24 and Au28(SR)20. A negative thermal expansion was detected for the Au–Au bonds of the metal coremore » (the first Au–Au shell) and was interpreted based on the unique Au core structure consisting of the Au4 units. EXAFS fitting results from Au28(SR)20, Au36(SR)24, and Au44(SR)28 show a size-dependent negative thermal expansion behavior in the first Au–Au shell, further highlighting the importance of the Au4 units in determining the Au core bonding properties and shedding light on the growth mechanism of these FCC-like Au clusters.« less

A green chemistry approach for synthesizing biocompatible gold nanoparticles.

PubMed

Gurunathan, Sangiliyandi; Han, JaeWoong; Park, Jung Hyun; Kim, Jin-Hoi

2014-01-01

Gold nanoparticles (AuNPs) are a fascinating class of nanomaterial that can be used for a wide range of biomedical applications, including bio-imaging, lateral flow assays, environmental detection and purification, data storage, drug delivery, biomarkers, catalysis, chemical sensors, and DNA detection. Biological synthesis of nanoparticles appears to be simple, cost-effective, non-toxic, and easy to use for controlling size, shape, and stability, which is unlike the chemically synthesized nanoparticles. The aim of this study was to synthesize homogeneous AuNPs using pharmaceutically important Ganoderma spp. We developed a simple, non-toxic, and green method for water-soluble AuNP synthesis by treating gold (III) chloride trihydrate (HAuCl4) with a hot aqueous extract of the Ganoderma spp. mycelia. The formation of biologically synthesized AuNPs (bio-AuNPs) was characterized by ultraviolet (UV)-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Furthermore, the biocompatibility of as-prepared AuNPs was evaluated using a series of assays, such as cell viability, lactate dehydrogenase leakage, and reactive oxygen species generation (ROS) in human breast cancer cells (MDA-MB-231). The color change of the solution from yellow to reddish pink and strong surface plasmon resonance were observed at 520 nm using UV-visible spectroscopy, and that indicated the formation of AuNPs. DLS analysis revealed the size distribution of AuNPs in liquid solution, and the average size of AuNPs was 20 nm. The size and morphology of AuNPs were investigated using TEM. The biocompatibility effect of as-prepared AuNPs was investigated in MDA-MB-231 breast cancer cells by using various concentrations of AuNPs (10 to 100 μM) for 24 h. Our findings suggest that AuNPs are non-cytotoxic and biocompatible. To the best of our knowledge, this is the first report to describe the synthesis of monodispersed, biocompatible, and soluble AuNPs with an average size of 20 nm using Ganoderma spp. This study opens up new possibilities of using an inexpensive and non-toxic mushroom extract as a reducing and stabilizing agent for the synthesis of size-controlled, large-scale, biocompatible, and monodispersed AuNPs, which may have future diagnostic and therapeutic applications.

A green chemistry approach for synthesizing biocompatible gold nanoparticles

NASA Astrophysics Data System (ADS)

Gurunathan, Sangiliyandi; Han, JaeWoong; Park, Jung Hyun; Kim, Jin-Hoi

2014-05-01

Gold nanoparticles (AuNPs) are a fascinating class of nanomaterial that can be used for a wide range of biomedical applications, including bio-imaging, lateral flow assays, environmental detection and purification, data storage, drug delivery, biomarkers, catalysis, chemical sensors, and DNA detection. Biological synthesis of nanoparticles appears to be simple, cost-effective, non-toxic, and easy to use for controlling size, shape, and stability, which is unlike the chemically synthesized nanoparticles. The aim of this study was to synthesize homogeneous AuNPs using pharmaceutically important Ganoderma spp . We developed a simple, non-toxic, and green method for water-soluble AuNP synthesis by treating gold (III) chloride trihydrate (HAuCl4) with a hot aqueous extract of the Ganoderma spp . mycelia. The formation of biologically synthesized AuNPs (bio-AuNPs) was characterized by ultraviolet (UV)-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray (EDX), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Furthermore, the biocompatibility of as-prepared AuNPs was evaluated using a series of assays, such as cell viability, lactate dehydrogenase leakage, and reactive oxygen species generation (ROS) in human breast cancer cells (MDA-MB-231). The color change of the solution from yellow to reddish pink and strong surface plasmon resonance were observed at 520 nm using UV-visible spectroscopy, and that indicated the formation of AuNPs. DLS analysis revealed the size distribution of AuNPs in liquid solution, and the average size of AuNPs was 20 nm. The size and morphology of AuNPs were investigated using TEM. The biocompatibility effect of as-prepared AuNPs was investigated in MDA-MB-231 breast cancer cells by using various concentrations of AuNPs (10 to 100 μM) for 24 h. Our findings suggest that AuNPs are non-cytotoxic and biocompatible. To the best of our knowledge, this is the first report to describe the synthesis of monodispersed, biocompatible, and soluble AuNPs with an average size of 20 nm using Ganoderma spp. This study opens up new possibilities of using an inexpensive and non-toxic mushroom extract as a reducing and stabilizing agent for the synthesis of size-controlled, large-scale, biocompatible, and monodispersed AuNPs, which may have future diagnostic and therapeutic applications.

Multifunctional gold nanoparticles for diagnosis and therapy of disease

PubMed Central

Mieszawska, Aneta J.; Mulder, Willem J. M.; Fayad, Zahi A.

2013-01-01

Gold nanoparticles (AuNPs) have a number of physical properties that make them appealing for medical applications. For example, the attenuation of X-rays by gold nanoparticles has led to their use in computed tomography imaging and as adjuvants for radiotherapy. AuNPs have numerous other applications in imaging, therapy and diagnostic systems. The advanced state of synthetic chemistry of gold nanoparticles offers precise control over physicochemical and optical properties. Furthermore gold cores are inert and are considered to be biocompatible and non-toxic. The surface of gold nanoparticles can easily be modified for a specific application and ligands for targeting, drugs or biocompatible coatings can be introduced. AuNPs can be incorporated into larger structures such as polymeric nanoparticles or liposomes that deliver large payloads for enhanced diagnostic applications, efficiently encapsulate drugs for concurrent therapy or add additional imaging labels. This array of features has led to the afore-mentioned applications in biomedical fields, but more recently in approaches where multifunctional gold nanoparticles are used for multiple methods, such as concurrent diagnosis and therapy, so called theranostics. The following review covers basic principles and recent findings in gold nanoparticle applications for imaging, therapy and diagnostics, with a focus on reports of multifunctional AuNPs. PMID:23360440

Colloid-Interface-Assisted Laser Irradiation of Nanocrystals Superlattices to be Scalable Plasmonic Superstructures with Novel Activities.

PubMed

Huang, Liu; Wan, Xiaodong; Rong, Hongpan; Yao, Yuan; Xu, Meng; Liu, Jia; Ji, Muwei; Liu, Jiajia; Jiang, Lan; Zhang, Jiatao

2018-04-01

High-efficient charge and energy transfer between nanocrystals (NCs) in a bottom-up assembly are hard to achieve, resulting in an obstacle in application. Instead of the ligands exchange strategies, the advantage of a continuous laser is taken with optimal wavelength and power to irradiate the film-scale NCs superlattices at solid-liquid interfaces. Owing to the Au-based NCs' surface plasmon resonance (SPR) effect, the gentle laser irradiation leads the Au NCs or Au@CdS core/shell NCs to attach each other with controlled pattern at the interfaces between solid NCs phase and liquid ethanol/ethylene glycol. A continuous wave 532 nm laser (6.68-13.37 W cm -2 ), to control Au-based superlattices, is used to form the monolayer with uniformly reduced interparticle distance followed by welded superstructures. Considering the size effect to Au NCs' melting, when decreasing the Au NCs size to ≈5 nm, stronger welding nanostructures are obtained with diverse unprecedented shapes which cannot be achieved by normal colloidal synthesis. With the help of facile scale-up and formation at solid-liquid interfaces, and a good connection of crystalline between NCs, the obtained plasmonic superstructured films that could be facilely transferred onto different substrates exhibit broad SPR absorption in the visible and near-infrared regime, enhanced electric conductivities, and wide applications as surface enhanced Raman scattering (SERS)-active substrates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tunable SERS signals of Rhodamine B molecules on Fe3O4@Au nanocomposite substrates controlled by magnetic field

NASA Astrophysics Data System (ADS)

Song, Hao; Fang, Rui Yang; Li, Ling

2018-02-01

In this work, we experimentally synthesized the Fe3O4@Au nanocomposites and used them as surface-enhanced Raman scattering (SERS) substrates. The Fe3O4@Au nanocomposites retained the metallic plasmon resonant effect and possessed the magnetic field controllable characteristics. The Raman spectra of Rhodamine B (RhB) probe molecules were studied under different external magnetic field. The magnitude of external magnetic field varied from 0 Gs to 700 Gs (1 Gs = 10-4 T) with intervals of 100 Gs. When the magnetic field magnitude increased, the Raman intensity of RhB probe molecules at 1356 cm-1 increased linearly. The slope of the linear fitting curves for the Raman intensity and area were 0.118/Gs and 3.700/Gs. The Raman enhancement could raise up to 7 times for RhB probe molecules when the magnetic field magnitude increased to 700 Gs. After removing the external magnetic field, the Raman peaks returned to its original intensity in several minutes. Under the external magnetic field, the Fe3O4@Au nanocomposites were concentrated, leading to the increase number of SERS "hot spots" and the surface Au density. The results show that the magnetic field controlled Fe3O4@Au nanocomposites can realize the enhanced and controllable SERS effect, which can be used in the reversible optical sensing and bio-medical applications.

Large-area high-performance SERS substrates with deep controllable sub-10-nm gap structure fabricated by depositing Au film on the cicada wing

NASA Astrophysics Data System (ADS)

Jiwei, Qi; Yudong, Li; Ming, Yang; Qiang, Wu; Zongqiang, Chen; Wudeng, Wang; Wenqiang, Lu; Xuanyi, Yu; Jingjun, Xu; Qian, Sun

2013-10-01

Noble metal nanogap structure supports strong surface-enhanced Raman scattering (SERS) which can be used to detect single molecules. However, the lack of reproducible fabrication techniques with nanometer-level control over the gap size has limited practical applications. In this letter, by depositing the Au film onto the cicada wing, we engineer the ordered array of nanopillar structures on the wing to form large-area high-performance SERS substrates. Through the control of the thickness of the Au film deposited onto the cicada wing, the gap sizes between neighboring nanopillars are fine defined. SERS substrates with sub-10-nm gap sizes are obtained, which have the highest average Raman enhancement factor (EF) larger than 2 × 108, about 40 times as large as that of commercial Klarite® substrates. The cicada wings used as templates are natural and environment-friendly. The depositing method is low cost and high throughput so that our large-area high-performance SERS substrates have great advantage for chemical/biological sensing applications.

The Preparation of Au@TiO2 Yolk-Shell Nanostructure and its Applications for Degradation and Detection of Methylene Blue

NASA Astrophysics Data System (ADS)

Wan, Gengping; Peng, Xiange; Zeng, Min; Yu, Lei; Wang, Kan; Li, Xinyue; Wang, Guizhen

2017-09-01

This paper reports the synthesis of a new type of Au@TiO2 yolk-shell nanostructures by integrating ion sputtering method with atomic layer deposition (ALD) technique and its applications as visible light-driven photocatalyst and surface-enhanced Raman spectroscopy (SERS) substrate. Both the size and amount of gold nanoparticles confined in TiO2 nanotubes could be facilely controlled via properly adjusting the sputtering time. The unique structure and morphology of the resulting Au@TiO2 samples were investigated by using various spectroscopic and microscopic techniques in detail. It is found that all tested samples can absorb visible light with a maximum absorption at localized surface plasmon resonance (LSPR) wavelengths (550-590 nm) which are determined by the size of gold nanoparticles. The Au@TiO2 yolk-shell composites were used as the photocatalyst for the degradation of methylene blue (MB). As compared with pure TiO2 nanotubes, Au@TiO2 composites exhibit improved photocatalytic properties towards the degradation of MB. The SERS effect of Au@TiO2 yolk-shell composites was also performed to investigate the detection sensitivity of MB.

The Preparation of Au@TiO2 Yolk-Shell Nanostructure and its Applications for Degradation and Detection of Methylene Blue.

PubMed

Wan, Gengping; Peng, Xiange; Zeng, Min; Yu, Lei; Wang, Kan; Li, Xinyue; Wang, Guizhen

2017-09-18

This paper reports the synthesis of a new type of Au@TiO 2 yolk-shell nanostructures by integrating ion sputtering method with atomic layer deposition (ALD) technique and its applications as visible light-driven photocatalyst and surface-enhanced Raman spectroscopy (SERS) substrate. Both the size and amount of gold nanoparticles confined in TiO 2 nanotubes could be facilely controlled via properly adjusting the sputtering time. The unique structure and morphology of the resulting Au@TiO 2 samples were investigated by using various spectroscopic and microscopic techniques in detail. It is found that all tested samples can absorb visible light with a maximum absorption at localized surface plasmon resonance (LSPR) wavelengths (550-590 nm) which are determined by the size of gold nanoparticles. The Au@TiO 2 yolk-shell composites were used as the photocatalyst for the degradation of methylene blue (MB). As compared with pure TiO 2 nanotubes, Au@TiO 2 composites exhibit improved photocatalytic properties towards the degradation of MB. The SERS effect of Au@TiO 2 yolk-shell composites was also performed to investigate the detection sensitivity of MB.

Temperature-dependent Raman spectroscopy studies of the interface coupling effect of monolayer ReSe2 single crystals on Au foils

NASA Astrophysics Data System (ADS)

Jiang, Shaolong; Zhao, Liyun; Shi, Yuping; Xie, Chunyu; Zhang, Na; Zhang, Zhepeng; Huan, Yahuan; Yang, Pengfei; Hong, Min; Zhou, Xiebo; Shi, Jianping; Zhang, Qing; Zhang, Yanfeng

2018-05-01

Rhenium diselenide (ReSe2), which bears in-plane anisotropic optical and electrical properties, is of considerable interest for its excellent applications in novel devices, such as polarization-sensitive photodetectors and integrated polarization-controllers. However, great challenges to date in the controllable synthesis of high-quality ReSe2 have hindered its in-depth investigations and practical applications. Herein, we report a feasible synthesis of monolayer single-crystal ReSe2 flakes on the Au foil substrate by using a chemical vapor deposition route. Particularly, we focus on the temperature-dependent Raman spectroscopy investigations of monolayer ReSe2 grown on Au foils, which present concurrent red shifts of Eg-like and Ag-like modes with increasing measurement temperature from 77–290 K. Linear temperature dependences of both modes are revealed and explained from the anharmonic vibration of the ReSe2 lattice. More importantly, the strong interaction of ReSe2 with Au, with respect to that with SiO2/Si, is further confirmed by temperature-dependent Raman characterization. This work is thus proposed to shed light on the optical and thermal properties of such anisotropic two-dimensional three-atom-thick materials.

Photo-induced transformation process at gold clusters-semiconductor interface: Implications for the complexity of gold clusters-based photocatalysis

PubMed Central

Liu, Siqi; Xu, Yi-Jun

2016-01-01

The recent thrust in utilizing atomically precise organic ligands protected gold clusters (Au clusters) as photosensitizer coupled with semiconductors for nano-catalysts has led to the claims of improved efficiency in photocatalysis. Nonetheless, the influence of photo-stability of organic ligands protected-Au clusters at the Au/semiconductor interface on the photocatalytic properties remains rather elusive. Taking Au clusters–TiO2 composites as a prototype, we for the first time demonstrate the photo-induced transformation of small molecular-like Au clusters to larger metallic Au nanoparticles under different illumination conditions, which leads to the diverse photocatalytic reaction mechanism. This transformation process undergoes a diffusion/aggregation mechanism accompanied with the onslaught of Au clusters by active oxygen species and holes resulting from photo-excited TiO2 and Au clusters. However, such Au clusters aggregation can be efficiently inhibited by tuning reaction conditions. This work would trigger rational structural design and fine condition control of organic ligands protected-metal clusters-semiconductor composites for diverse photocatalytic applications with long-term photo-stability. PMID:26947754

Photo-induced transformation process at gold clusters-semiconductor interface: Implications for the complexity of gold clusters-based photocatalysis

NASA Astrophysics Data System (ADS)

Liu, Siqi; Xu, Yi-Jun

2016-03-01

The recent thrust in utilizing atomically precise organic ligands protected gold clusters (Au clusters) as photosensitizer coupled with semiconductors for nano-catalysts has led to the claims of improved efficiency in photocatalysis. Nonetheless, the influence of photo-stability of organic ligands protected-Au clusters at the Au/semiconductor interface on the photocatalytic properties remains rather elusive. Taking Au clusters-TiO2 composites as a prototype, we for the first time demonstrate the photo-induced transformation of small molecular-like Au clusters to larger metallic Au nanoparticles under different illumination conditions, which leads to the diverse photocatalytic reaction mechanism. This transformation process undergoes a diffusion/aggregation mechanism accompanied with the onslaught of Au clusters by active oxygen species and holes resulting from photo-excited TiO2 and Au clusters. However, such Au clusters aggregation can be efficiently inhibited by tuning reaction conditions. This work would trigger rational structural design and fine condition control of organic ligands protected-metal clusters-semiconductor composites for diverse photocatalytic applications with long-term photo-stability.

Fabrication of Ag-Au bimetallic nanoparticles by laser-induced dewetting of bilayer films

NASA Astrophysics Data System (ADS)

Oh, Yoonseok; Lee, Jeeyoung; Lee, Myeongkyu

2018-03-01

We here show that Ag-Au bimetallic nanoparticles (NPs) can be produced by dewetting an Ag/Au bilayer film coated on glass using a nanosecond-pulsed laser beam. Elemental analysis revealed that the obtained bimetallic NPs are Ag-Au alloys, with two elements well mixed over the whole volume of the particle. The composition of the produced particles was controllable by changing the relative thickness of each layer. The localized surface plasmon resonance (LSPR) peak was red-shifted with an increasing Au content and the LSPR wavelength could be tuned from 415 to 525 nm by varying the alloy composition. A film area of several square centimeters could be transformed into Ag-Au NPs by a single laser pulse of 6 ns duration. This study provides a facile and scalable route to prepare bimetallic NPs for plasmonic and other applications.

Induced accumulation of Au, Ag and Cu in Brassica napus grown in a mine tailings with the inoculation of Aspergillus niger and the application of two chemical compounds.

PubMed

González-Valdez, Eduardo; Alarcón, Alejandro; Ferrera-Cerrato, Ronald; Vega-Carrillo, Héctor René; Maldonado-Vega, María; Salas-Luévano, Miguel Ángel; Argumedo-Delira, Rosalba

2018-06-15

This study evaluated the ability of Brassica napus for extracting gold (Au), silver (Ag) and copper (Cu) from a mine tailings, with the inoculation of two Aspergillus niger strains, and the application of ammonium thiocyanate (NH 4 SCN) or ammonium thiosulfate [(NH 4 ) 2 S 2 O 3 ]. After seven weeks of growth inoculated or non-inoculated plants were applied with 1 or 2 g kg -1 of either NH 4 SCN or (NH 4 ) 2 S 2 O 3 , respectively. Eight days after the application of the chemical compounds, plants were harvested for determining the total dry biomass, and the content of Au, Ag, and Cu in plant organs. Application of (NH 4 ) 2 S 2 O 3 or NH 4 SCN resulted in enhanced Au-accumulation in stems (447% and 507%, respectively), while either (NH 4 ) 2 S 2 O 3 +Aspergillus, or NH 4 SCN increased the Au-accumulation in roots (198.5% and 404%, respectively) when compared to the control. Treatments with (NH 4 ) 2 S 2 O 3 or (NH 4 ) 2 S 2 O 3 +Aspergillus significantly increased (P ≤ 0.001) the accumulation of Ag in leaves (677% and 1376%, respectively), while NH 4 SCN + Aspergillus, and (NH 4 ) 2 S 2 O 3 enhanced the accumulation in stems (7153% and 6717.5%). The Ag-accumulation in roots was stimulated by NH 4 SCN+ Aspergillus, and (NH 4 ) 2 S 2 O 3 + Aspergillus (132.5% and 178%, respectively), when compared to the control. The combination of NH 4 SCN+Aspergillus significantly enhanced the Cu-accumulation in leaves (228%); whereas NH 4 SCN+ Aspergillus, or (NH 4 ) 2 S 2 O 3 + Aspergillus resulted in greater accumulation of Cu in stems (1233.5% and 1580%, respectively) than the control. Results suggest that either NH 4 SCN or (NH 4 ) 2 S 2 O 3 (with or without Aspergillus) improved the accumulation of Au and Ag by B. napus. Accumulation of Au and Ag in plant organs overpassed the hyperaccumulation criterion (> 1 mg kg -1 of plant biomass); whereas Cu-accumulation in stems and roots also overpassed such criterion (> 1000 mg kg -1 ) by applying either NH 4 SCN or (NH 4 ) 2 S 2 O 3 + A. niger. Copyright © 2018 Elsevier Inc. All rights reserved.

Fabrication of hierarchical hybrid structures using bio-enabled layer-by-layer self-assembly.

PubMed

Hnilova, Marketa; Karaca, Banu Taktak; Park, James; Jia, Carol; Wilson, Brandon R; Sarikaya, Mehmet; Tamerler, Candan

2012-05-01

Development of versatile and flexible assembly systems for fabrication of functional hybrid nanomaterials with well-defined hierarchical and spatial organization is of a significant importance in practical nanobiotechnology applications. Here we demonstrate a bio-enabled self-assembly technique for fabrication of multi-layered protein and nanometallic assemblies utilizing a modular gold-binding (AuBP1) fusion tag. To accomplish the bottom-up assembly we first genetically fused the AuBP1 peptide sequence to the C'-terminus of maltose-binding protein (MBP) using two different linkers to produce MBP-AuBP1 hetero-functional constructs. Using various spectroscopic techniques, surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), we verified the exceptional binding and self-assembly characteristics of AuBP1 peptide. The AuBP1 peptide tag can direct the organization of recombinant MBP protein on various gold surfaces through an efficient control of the organic-inorganic interface at the molecular level. Furthermore using a combination of soft-lithography, self-assembly techniques and advanced AuBP1 peptide tag technology, we produced spatially and hierarchically controlled protein multi-layered assemblies on gold nanoparticle arrays with high molecular packing density and pattering efficiency in simple, reproducible steps. This model system offers layer-by-layer assembly capability based on specific AuBP1 peptide tag and constitutes novel biological routes for biofabrication of various protein arrays, plasmon-active nanometallic assemblies and devices with controlled organization, packing density and architecture. Copyright © 2011 Wiley Periodicals, Inc.

Atomic structure of a peptide coated gold nanocluster identified using theoretical and experimental studies

NASA Astrophysics Data System (ADS)

Wang, Hui; Li, Xu; Gao, Liang; Zhai, Jiao; Liu, Ru; Gao, Xueyun; Wang, Dongqi; Zhao, Lina

2016-06-01

Peptide coated gold nanoclusters (AuNCs) have a precise molecular formula and atomic structure, which are critical for their unique applications in targeting specific proteins either for protein analysis or drug design. To date, a study of the crystal structure of peptide coated AuNCs is absent primarily due to the difficulty of obtaining their crystalline phases in an experiment. Here we study a typical peptide coated AuNC (Au24Peptide8, Peptide = H2N-CCYKKKKQAGDV-COOH, Anal. Chem., 2015, 87, 2546) to figure out its atomic structure and electronic structure using a theoretical method for the first time. In this work, we identify the explicit configuration of the essential structure of Au24Peptide8, Au24(Cys-Cys)8, using density functional theory (DFT) computations and optical spectroscopic experiments, where Cys denotes cysteine without H bonded to S. As the first multidentate ligand binding AuNC, Au24(Cys-Cys)8 is characterized as a distorted Au13 core with Oh symmetry covered by two Au(Cys-Cys) and three Au3(Cys-Cys)2 staple motifs in its atomic structure. The most stable configuration of Au24(Cys-Cys)8 is confirmed by comparing its UV-vis absorption spectrum from time-dependent density-functional theory (TDDFT) calculations with optical absorption measurements, and these results are consistent with each other. Furthermore, we carry out frontier molecular orbital (FMO) calculations to elucidate that the electronic structure of Au24(Cys-Cys)8 is different from that of Au24(SR)20 as they have a different Au/S ratio, where SR represents alkylthiolate. Importantly, the different ligand coatings, Cys-Cys and SR, in Au24(Cys-Cys)8 and Au24(SR)20 cause the different Au/S ratios in the coated Au24. The reason is that the Au/S ratio is crucial in determining the size of the Au core of the ligand protected AuNC, and the size of the Au core corresponds to a specific electronic structure. By the adjustment of ligand coatings from alkylthiolate to peptide, the Au/S ratio could be controlled to generate different AuNCs with versatile electronic structures, optical properties and reaction stabilities. Therefore, we propose a universal approach to obtain a specific Au/S ratio of ligand coated AuNCs by adjusting the ligand composition, thus controlling the chemicophysical properties of AuNCs with ultimately the same number of Au atoms.Peptide coated gold nanoclusters (AuNCs) have a precise molecular formula and atomic structure, which are critical for their unique applications in targeting specific proteins either for protein analysis or drug design. To date, a study of the crystal structure of peptide coated AuNCs is absent primarily due to the difficulty of obtaining their crystalline phases in an experiment. Here we study a typical peptide coated AuNC (Au24Peptide8, Peptide = H2N-CCYKKKKQAGDV-COOH, Anal. Chem., 2015, 87, 2546) to figure out its atomic structure and electronic structure using a theoretical method for the first time. In this work, we identify the explicit configuration of the essential structure of Au24Peptide8, Au24(Cys-Cys)8, using density functional theory (DFT) computations and optical spectroscopic experiments, where Cys denotes cysteine without H bonded to S. As the first multidentate ligand binding AuNC, Au24(Cys-Cys)8 is characterized as a distorted Au13 core with Oh symmetry covered by two Au(Cys-Cys) and three Au3(Cys-Cys)2 staple motifs in its atomic structure. The most stable configuration of Au24(Cys-Cys)8 is confirmed by comparing its UV-vis absorption spectrum from time-dependent density-functional theory (TDDFT) calculations with optical absorption measurements, and these results are consistent with each other. Furthermore, we carry out frontier molecular orbital (FMO) calculations to elucidate that the electronic structure of Au24(Cys-Cys)8 is different from that of Au24(SR)20 as they have a different Au/S ratio, where SR represents alkylthiolate. Importantly, the different ligand coatings, Cys-Cys and SR, in Au24(Cys-Cys)8 and Au24(SR)20 cause the different Au/S ratios in the coated Au24. The reason is that the Au/S ratio is crucial in determining the size of the Au core of the ligand protected AuNC, and the size of the Au core corresponds to a specific electronic structure. By the adjustment of ligand coatings from alkylthiolate to peptide, the Au/S ratio could be controlled to generate different AuNCs with versatile electronic structures, optical properties and reaction stabilities. Therefore, we propose a universal approach to obtain a specific Au/S ratio of ligand coated AuNCs by adjusting the ligand composition, thus controlling the chemicophysical properties of AuNCs with ultimately the same number of Au atoms. Electronic supplementary information (ESI) available: The MALDI-TOF-MS identification of Au24Peptide8, the structural divisions of Au24(Cys-Cys)8 obtained based on the ``divide and protect'' approach, the structure of level-1 and -3 staple motifs, the relative energies of all stable configurations of Au24(Cys-Cys)8, orbital components of Iso1 of Au24(Cys-Cys)8, electronic structure comparison between Au24(Cys-Cys)8 and Au24(SR)20, and the coordination of Iso1. See DOI: 10.1039/c5nr08727a

Midportion achilles tendon microcirculation after intermittent combined cryotherapy and compression compared with cryotherapy alone: a randomized trial.

PubMed

Knobloch, Karsten; Grasemann, Ruth; Spies, Marcus; Vogt, Peter M

2008-11-01

The effect of combined cryotherapy/compression versus cryotherapy alone on the Achilles tendon is undetermined. Standardized combined cryotherapy/compression changes in midportion Achilles tendon microcirculation are superior to those with cryotherapy during intermittent application. Controlled laboratory study. Sixty volunteers were randomized for either combined cryotherapy/compression (Cryo/Cuff, DJO Inc, Vista, California: n = 30; 32 +/- 11 years) or cryotherapy alone (KoldBlue, TLP Industries, Kent, United Kingdom: n = 30; 33 +/- 12 years) with intermittent 3 x 10-minute application. Midportion Achilles tendon microcirculation was determined (O2C, LEA Medizintechnik, Giessen, Germany). Both Cryo/Cuff and KoldBlue significantly reduced superficial and deep capillary tendon blood flow within the first minute of application (43 +/- 46 arbitrary units [AU] vs 10 +/- 19 AU and 42 +/- 46 AU vs 12 +/- 10 AU; P = .0001) without a significant difference throughout all 3 applications. However, during recovery, superficial and deep capillary blood flow was reestablished significantly faster using Cryo/Cuff (P = .023). Tendon oxygen saturation was reduced in both groups significantly (3 minutes Cryo/Cuff: 36% +/- 20% vs 16% +/- 15%; KoldBlue: 42% +/- 19% vs 28% +/- 20%; P < .05) with significantly stronger effects using Cryo/Cuff (P = .014). Cryo/Cuff led to significantly higher tendon oxygenation (Cryo/Cuff: 62% +/- 28% vs baseline 36% +/- 20%; P = .0001) in superficial and deep tissue (Cryo/Cuff: 73% +/- 14% vs baseline 65% +/- 17%; P = .0001) compared with KoldBlue during all recoveries. Postcapillary venous filling pressures were significantly reduced in both groups during application; however, Cryo/Cuff led to significantly, but marginally, lower pressures (Cryo/Cuff: 41 +/- 7 AU vs baseline 51 +/- 13 AU; P = .0001 and KoldBlue: 46 +/- 7 AU vs baseline 56 +/- 11 AU; P = .026 for Cryo/Cuff vs KoldBlue). Increased tendon oxygenation is achieved as tendon preconditioning by combined cryotherapy and compression with significantly increased tendon oxygen saturation during recovery in contrast to cryotherapy alone. Both regimens lead to a significant amelioration of tendinous venous outflow. Combined cryotherapy and compression is superior to cryotherapy alone regarding the Achilles tendon microcirculation. Further studies in tendinopathy and tendon rehabilitation are warranted to elucidate its value regarding functional issues.

Evolution of Self-Assembled Au NPs by Controlling Annealing Temperature and Dwelling Time on Sapphire (0001).

PubMed

Lee, Jihoon; Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kunwar, Sundar

2015-12-01

Au nanoparticles (NPs) have been utilized in a wide range of device applications as well as catalysts for the fabrication of nanopores and nanowires, in which the performance of the associated devices and morphology of nanopores and nanowires are strongly dependent on the size, density, and configuration of the Au NPs. In this paper, the evolution of the self-assembled Au nanostructures and NPs on sapphire (0001) is systematically investigated with the variation of annealing temperature (AT) and dwelling time (DT). At the low-temperature range between 300 and 600 °C, three distinct regimes of the Au nanostructure configuration are observed, i.e., the vermiform-like Au piles, irregular Au nano-mounds, and Au islands. Subsequently, being provided with relatively high thermal energy between 700 and 900 °C, the round dome-shaped Au NPs are fabricated based on the Volmer-Weber growth model. With the increased AT, the size of the Au NPs is gradually increased due to a more favorable surface diffusion while the density is gradually decreased as a compensation. On the other hand, with the increased DT, the size and density of Au NPs decrease due to the evaporation of Au at relatively high annealing temperature at 950 °C.

Electrophoretic build-up of alternately multilayered films and micropatterns based on graphene sheets and nanoparticles and their applications in flexible supercapacitors.

PubMed

Niu, Zhiqiang; Du, Jianjun; Cao, Xuebo; Sun, Yinghui; Zhou, Weiya; Hng, Huey Hoon; Ma, Jan; Chen, Xiaodong; Xie, Sishen

2012-10-22

Graphene nanosheets and metal nanoparticles (NPs) have been used as nano-building-blocks for assembly into macroscale hybrid structures with promising performance in electrical devices. However, in most graphene and metal NP hybrid structures, the graphene sheets and metal NPs (e.g., AuNPs) do not enable control of the reaction process, orientation of building blocks, and organization at the nanoscale. Here, an electrophoretic layer-by-layer assembly for constructing multilayered reduced graphene oxide (RGO)/AuNP films and lateral micropatterns is presented. This assembly method allows easy control of the nano-architecture of building blocks along the normal direction of the film, including the number and thickness of RGO and AuNP layers, in addition to control of the lateral orientation of the resultant multilayered structures. Conductivity of multilayered RGO/AuNP hybrid nano-architecture shows great improvement caused by a bridging effect of the AuNPs along the out-of-plane direction between the upper and lower RGO layers. The results clearly show the potential of electrophoretic build-up in the fabrication of graphene-based alternately multilayered films and patterns. Finally, flexible supercapacitors based on multilayered RGO/AuNP hybrid films are fabricated, and excellent performance, such as high energy and power densities, are achieved. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DNA Origami Directed Au Nanostar Dimers for Single-Molecule Surface-Enhanced Raman Scattering.

PubMed

Tanwar, Swati; Haldar, Krishna Kanta; Sen, Tapasi

2017-12-06

We demonstrate the synthesis of Au nanostar dimers with tunable interparticle gap and controlled stoichiometry assembled on DNA origami. Au nanostars with uniform and sharp tips were immobilized on rectangular DNA origami dimerized structures to create nanoantennas containing monomeric and dimeric Au nanostars. Single Texas red (TR) dye was specifically attached in the junction of the dimerized origami to act as a Raman reporter molecule. The SERS enhancement factors of single TR dye molecules located in the conjunction region in dimer structures having interparticle gaps of 7 and 13 nm are 2 × 10 10 and 8 × 10 9 , respectively, which are strong enough for single analyte detection. The highly enhanced electromagnetic field generated by the plasmon coupling between sharp tips and cores of two Au nanostars in the wide conjunction region allows the accommodation and specific detection of large biomolecules. Such DNA-directed assembled nanoantennas with controlled interparticle separation distance and stoichiometry, and well-defined geometry, can be used as excellent substrates in single-molecule SERS spectroscopy and will have potential applications as a reproducible platform in single-molecule sensing.

Highly conductive ribbons prepared by stick-slip assembly of organosoluble gold nanoparticles.

PubMed

Lawrence, Jimmy; Pham, Jonathan T; Lee, Dong Yun; Liu, Yujie; Crosby, Alfred J; Emrick, Todd

2014-02-25

Precisely positioning and assembling nanoparticles (NPs) into hierarchical nanostructures is opening opportunities in a wide variety of applications. Many techniques employed to produce hierarchical micrometer and nanoscale structures are limited by complex fabrication of templates and difficulties with scalability. Here we describe the fabrication and characterization of conductive nanoparticle ribbons prepared from surfactant-free organosoluble gold nanoparticles (Au NPs). We used a flow-coating technique in a controlled, stick-slip assembly to regulate the deposition of Au NPs into densely packed, multilayered structures. This affords centimeter-scale long, high-resolution Au NP ribbons with precise periodic spacing in a rapid manner, up to 2 orders-of-magnitude finer and faster than previously reported methods. These Au NP ribbons exhibit linear ohmic response, with conductivity that varies by changing the binding headgroup of the ligands. Controlling NP percolation during sintering (e.g., by adding polymer to retard rapid NP coalescence) enables the formation of highly conductive ribbons, similar to thermally sintered conductive adhesives. Hierarchical, conductive Au NP ribbons represent a promising platform to enable opportunities in sensing, optoelectronics, and electromechanical devices.

In Situ Reductive Synthesis of Structural Supported Gold Nanorods in Porous Silicon Particles for Multifunctional Nanovectors.

PubMed

Zhu, Guixian; Liu, Jen-Tsai; Wang, Yuzhen; Zhang, Dechen; Guo, Yi; Tasciotti, Ennio; Hu, Zhongbo; Liu, Xuewu

2016-05-11

Porous silicon nanodisks (PSD) were fabricated by the combination of photolithography and electrochemical etching of silicon. By using PSD as a reducing agent, gold nanorods (AuNR) were in situ synthesized in the nanopores of PSD, forming PSD-supported-AuNR (PSD/AuNR) hybrid particles. The formation mechanism of AuNR in porous silicon (pSi) was revealed by exploring the role of pSi reducibility and each chemical in the reaction. With the PSD support, AuNR exhibited a stable morphology without toxic surface ligands (CTAB). The PSD/AuNR hybrid particles showed enhanced plasmonic property compared to free AuNR. Because high-density "hot spots" can be generated by controlling the distribution of AuNR supported in PSD, surface-enhanced raman scattering (SERS) using PSD/AuNR as particle substrates was demonstrated. A multifunctional vector, PSD/AuNR/DOX, composed of doxorubicin (DOX)-loaded PSD/AuNR capped with agarose (agar), was developed for highly efficient, combinatorial cancer treatment. Their therapeutic efficacy was examined using two pancreatic cancer cell lines, PANC-1 and MIA PaCa-2. PSD/AuNR/DOX (20 μg Au and 1.25 μg DOX/mL) effectively destroyed these cells under near-IR laser irradiation (810 nm, 15 J·cm(-2) power, 90 s). Overall, we envision that PSD/AuNR may be a promising injectable, multifunctional nanovector for biomedical application.

Gold nanorod-based poly(lactic-co-glycolic acid) with manganese dioxide core-shell structured multifunctional nanoplatform for cancer theranostic applications.

PubMed

Wang, Lei; Li, Dong; Hao, Yongwei; Niu, Mengya; Hu, Yujie; Zhao, Hongjuan; Chang, Junbiao; Zhang, Zhenzhong; Zhang, Yun

2017-01-01

Recently, photothermal therapy has become a promising strategy in tumor treatment. However, the therapeutic effect was seriously hampered by the low tissue penetration of laser. Therefore, in this study, radiofrequency (RF) with better tissue penetration was used for tumor hyperthermia. First, one type of gold nanorods (AuNRs) suitable for RF hyperthermia was selected. Then, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with AuNRs and docetaxel (DTX) (PLGA/AuNR/DTX) NPs were constructed. Finally, manganese dioxide (MnO 2 ) ultrathin nanofilms were coated on the surfaces of PLGA/AuNR/DTX NPs by the reduction of KMnO 4 to construct the PLGA/AuNR/DTX@MnO 2 drug delivery system. This drug delivery system can not only be used for the combined therapy of chemotherapy and RF hyperthermia but can also produce Mn 2+ to enable magnetic resonance imaging. Furthermore, the RF hyperthermia and the degradation of MnO 2 can significantly promote the controlled drug release in a tumor region. The in vitro and in vivo results suggested that the PLGA/AuNR/DTX@MnO 2 multifunctional drug delivery system is a promising nanoplatform for effective cancer theranostic applications.

Gold nanorod–based poly(lactic-co-glycolic acid) with manganese dioxide core–shell structured multifunctional nanoplatform for cancer theranostic applications

PubMed Central

Wang, Lei; Li, Dong; Hao, Yongwei; Niu, Mengya; Hu, Yujie; Zhao, Hongjuan; Chang, Junbiao; Zhang, Zhenzhong; Zhang, Yun

2017-01-01

Recently, photothermal therapy has become a promising strategy in tumor treatment. However, the therapeutic effect was seriously hampered by the low tissue penetration of laser. Therefore, in this study, radiofrequency (RF) with better tissue penetration was used for tumor hyperthermia. First, one type of gold nanorods (AuNRs) suitable for RF hyperthermia was selected. Then, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with AuNRs and docetaxel (DTX) (PLGA/AuNR/DTX) NPs were constructed. Finally, manganese dioxide (MnO2) ultrathin nanofilms were coated on the surfaces of PLGA/AuNR/DTX NPs by the reduction of KMnO4 to construct the PLGA/AuNR/DTX@MnO2 drug delivery system. This drug delivery system can not only be used for the combined therapy of chemotherapy and RF hyperthermia but can also produce Mn2+ to enable magnetic resonance imaging. Furthermore, the RF hyperthermia and the degradation of MnO2 can significantly promote the controlled drug release in a tumor region. The in vitro and in vivo results suggested that the PLGA/AuNR/DTX@MnO2 multifunctional drug delivery system is a promising nanoplatform for effective cancer theranostic applications. PMID:28450782

Rhenium-phthalocyanine molecular nanojunction with high magnetic anisotropy and high spin filtering efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J.; Institute of Nanomaterial and Nanostructure, Changsha University of Science and Technology, Changsha 410114; Hu, J.

2015-07-20

Using the density functional and non-equilibrium Green's function approaches, we studied the magnetic anisotropy and spin-filtering properties of various transition metal-Phthalocyanine molecular junctions across two Au electrodes. Our important finding is that the Au-RePc-Au junction has both large spin filtering efficiency (>80%) and large magnetic anisotropy energy, which makes it suitable for device applications. To provide insights for the further experimental work, we discussed the correlation between the transport property, magnetic anisotropy, and wave function features of the RePc molecule, and we also illustrated the possibility of controlling its magnetic state.

Facile synthesis of gold nanomaterials with unusual crystal structures.

PubMed

Fan, Zhanxi; Huang, Xiao; Chen, Ye; Huang, Wei; Zhang, Hua

2017-11-01

Gold (Au) nanomaterials have attracted wide research attention, owing to their high chemical stability, promising catalytic properties, excellent biocompatibility, unique electronic structure and outstanding localized surface plasmon resonance (LSPR) absorption properties; all of which are closely related to their size and shape. Recently, crystal-phase-controlled synthesis of noble metal nanomaterials has emerged as a promising strategy to tune their physicochemical properties. This protocol describes the detailed experimental procedures for the crystal-phase-controlled syntheses of Au nanomaterials with unusual crystal structures under mild conditions. Briefly, pure hexagonal close-packed (hcp) Au square sheets (AuSSs) with a thickness of ∼2.4 nm are synthesized using a graphene-oxide-assisted method in which HAuCl 4 is reduced by oleylamine in a mixture of hexane and ethanol. By using pure hexane as the solvent, well-dispersed ultrathin hcp/face-centered cubic (fcc) Au nanowires with a diameter of ∼1.6 nm on graphene oxide can be obtained. Meanwhile, hcp/fcc Au square-like plates with a side length of 200-400 nm are prepared via the secondary growth of Au on the hcp AuSSs. Remarkably, hexagonal (4H) Au nanoribbons with a thickness of 2.0-6.0 nm can be synthesized with a one-pot colloidal method in which HAuCl 4 is reduced by oleylamine in a mixed solvent of hexane and 1,2-dichloropropane. It takes 17-37 h for the synthesis of these Au nanomaterials with unusual crystal structures. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) are used to characterize the resultant Au nanomaterials, which could have many promising applications, such as biosensing, near-IR photothermal therapy, catalysis and surface-enhanced Raman scattering (SERS).

Electrochemical synthesis of mesoporous Pt-Au binary alloys with tunable compositions for enhancement of electrochemical performance.

PubMed

Yamauchi, Yusuke; Tonegawa, Akihisa; Komatsu, Masaki; Wang, Hongjing; Wang, Liang; Nemoto, Yoshihiro; Suzuki, Norihiro; Kuroda, Kazuyuki

2012-03-21

Mesoporous Pt-Au binary alloys were electrochemically synthesized from lyotropic liquid crystals (LLCs) containing corresponding metal species. Two-dimensional exagonally ordered LLC templates were prepared on conductive substrates from diluted surfactant solutions including water, a nonionic surfactant, ethanol, and metal species by drop-coating. Electrochemical synthesis using such LLC templates enabled the preparation of ordered mesoporous Pt-Au binary alloys without phase segregation. The framework composition in the mesoporous Pt-Au alloy was controlled simply by changing the compositional ratios in the precursor solution. Mesoporous Pt-Au alloys with low Au content exhibited well-ordered 2D hexagonal mesostructures, reflecting those of the original templates. With increasing Au content, however, the mesostructural order gradually decreased, thereby reducing the electrochemically active surface area. Wide-angle X-ray diffraction profiles, X-ray photoelectron spectra, and elemental mapping showed that both Pt and Au were atomically distributed in the frameworks. The electrochemical stability of mesoporous Pt-Au alloys toward methanol oxidation was highly improved relative to that of nonporous Pt and mesoporous Pt films, suggesting that mesoporous Pt-Au alloy films are potentially applicable as electrocatalysts for direct methanol fuel cells. Also, mesoporous Pt-Au alloy electrodes showed a highly sensitive amperometric response for glucose molecules, which will be useful in next-generation enzyme-free glucose sensors.

Magnetic activity of surface plasmon resonance using dielectric magnetic materials fabricated on quartz glass substrate

NASA Astrophysics Data System (ADS)

Narushima, Kazuki; Ashizawa, Yoshito; Brachwitz, Kerstin; Hochmuth, Holger; Lorenz, Michael; Grundmann, Marius; Nakagawa, Katsuji

2016-07-01

The magnetic activity of surface plasmons in Au/MFe2O4 (M = Ni, Co, and Zn) polycrystalline bilayer films fabricated on a quartz glass substrate was studied for future magnetic sensor applications using surface plasmon resonance. The excitation of surface plasmons and their magnetic activity were observed in all investigated Au/MFe2O4 films. The magnetic activity of surface plasmons of the polycrystalline Au/NiFe2O4 film was larger than those of the other polycrystalline Au/MFe2O4 films, the epitaxial NiFe2O4 film, and metallic films. The large magnetic activity of surface plasmons of the polycrystalline film is controlled by manipulating surface plasmon excitation conditions and magnetic properties.

Temperature-dependent Raman spectroscopy studies of the interface coupling effect of monolayer ReSe2 single crystals on Au foils.

PubMed

Jiang, Shaolong; Zhao, Liyun; Shi, Yuping; Xie, Chunyu; Zhang, Na; Zhang, Zhepeng; Huan, Yahuan; Yang, Pengfei; Hong, Min; Zhou, Xiebo; Shi, Jianping; Zhang, Qing; Zhang, Yanfeng

2018-05-18

Rhenium diselenide (ReSe 2 ), which bears in-plane anisotropic optical and electrical properties, is of considerable interest for its excellent applications in novel devices, such as polarization-sensitive photodetectors and integrated polarization-controllers. However, great challenges to date in the controllable synthesis of high-quality ReSe 2 have hindered its in-depth investigations and practical applications. Herein, we report a feasible synthesis of monolayer single-crystal ReSe 2 flakes on the Au foil substrate by using a chemical vapor deposition route. Particularly, we focus on the temperature-dependent Raman spectroscopy investigations of monolayer ReSe 2 grown on Au foils, which present concurrent red shifts of E g -like and A g -like modes with increasing measurement temperature from 77-290 K. Linear temperature dependences of both modes are revealed and explained from the anharmonic vibration of the ReSe 2 lattice. More importantly, the strong interaction of ReSe 2 with Au, with respect to that with SiO 2 /Si, is further confirmed by temperature-dependent Raman characterization. This work is thus proposed to shed light on the optical and thermal properties of such anisotropic two-dimensional three-atom-thick materials.

Electrophoretic deposition of fluorescent Cu and Au sheets for light-emitting diodes

NASA Astrophysics Data System (ADS)

Liu, Jiale; Wu, Zhennan; Li, Tingting; Zhou, Ding; Zhang, Kai; Sheng, Yu; Cui, Jianli; Zhang, Hao; Yang, Bai

2015-12-01

Electrophoretic deposition (EPD) is a conventional method for fabricating film materials from nanometer-sized building blocks, and exhibits the advantages of low-cost, high-efficiency, wide-range thickness adjustment, and uniform deposition. Inspired by the interest in the application of two-dimensional (2D) nanomaterials, the EPD technique has been recently extended to building blocks with 2D features. However, the studies are mainly focused on simplex building blocks. The utilization of multiplex building blocks is rarely reported. In this work, we demonstrate a controlled EPD of Cu and Au sheets, which are 2D assemblies of luminescent Cu and Au nanoclusters. Systematic investigations reveal that both the deposition efficiency and the thickness are determined by the lateral size of the sheets. For Cu sheets with a large lateral size, a high ζ-potential and strong face-to-face van der Waals interactions facilitate the deposition with high efficiency. However, for Au sheets, the small lateral size and ζ-potential limit the formation of a thick film. To solve this problem, the deposition dynamics are controlled by increasing the concentration of the Au sheets and adding acetone. This understanding permits the fabrication of a binary EPD film by the stepwise deposition of Cu and Au sheets, thus producing a luminescent film with both Cu green emission and Au red emission. A white light-emitting diode prototype with color coordinates (x, y) = (0.31, 0.36) is fabricated by employing the EPD film as a color conversion layer on a 365 nm GaN clip and further tuning the amount of deposited Cu and Au sheets.Electrophoretic deposition (EPD) is a conventional method for fabricating film materials from nanometer-sized building blocks, and exhibits the advantages of low-cost, high-efficiency, wide-range thickness adjustment, and uniform deposition. Inspired by the interest in the application of two-dimensional (2D) nanomaterials, the EPD technique has been recently extended to building blocks with 2D features. However, the studies are mainly focused on simplex building blocks. The utilization of multiplex building blocks is rarely reported. In this work, we demonstrate a controlled EPD of Cu and Au sheets, which are 2D assemblies of luminescent Cu and Au nanoclusters. Systematic investigations reveal that both the deposition efficiency and the thickness are determined by the lateral size of the sheets. For Cu sheets with a large lateral size, a high ζ-potential and strong face-to-face van der Waals interactions facilitate the deposition with high efficiency. However, for Au sheets, the small lateral size and ζ-potential limit the formation of a thick film. To solve this problem, the deposition dynamics are controlled by increasing the concentration of the Au sheets and adding acetone. This understanding permits the fabrication of a binary EPD film by the stepwise deposition of Cu and Au sheets, thus producing a luminescent film with both Cu green emission and Au red emission. A white light-emitting diode prototype with color coordinates (x, y) = (0.31, 0.36) is fabricated by employing the EPD film as a color conversion layer on a 365 nm GaN clip and further tuning the amount of deposited Cu and Au sheets. Electronic supplementary information (ESI) available: Additional experimental information, and SEM images of Cu EPD films. See DOI: 10.1039/c5nr06599b

Gold nanoparticle should understand protein corona for being a clinical nanomaterial.

PubMed

Charbgoo, Fahimeh; Nejabat, Mojgan; Abnous, Khalil; Soltani, Fatemeh; Taghdisi, Seyed Mohammad; Alibolandi, Mona; Thomas Shier, W; Steele, Terry W J; Ramezani, Mohammad

2018-02-28

Gold nanoparticles (AuNPs) have attracted great attention in biomedical fields due to their unique properties. However, there are few reports on clinical trial of these nanoparticles. In vivo, AuNPs face complex biological fluids containing abundant proteins, which challenge the prediction of their fate that is known as "bio-identity". These proteins attach onto the AuNPs surface forming protein corona that makes the first step of nano-bio interface and dictates the subsequent AuNPs fate. Protein corona formation even stealth active targeting effect of AuNPs. Manipulating the protein corona identity based on the researcher goal is the way to employ corona to achieve maximum effect in therapy or other applications. In this review, we provide details on the biological identity of AuNPs under various environmental- and/or physiological conditions. We also highlight how the particular corona can direct the biodistribution of AuNPs. We further discuss the strategies available for controlling or reducing corona formation on AuNPs surface and achieving desired effects using AuNPs in vivo by engineering protein corona on their surface. Copyright © 2018 Elsevier B.V. All rights reserved.

Manipulating the architecture of bimetallic nanostructures and their plasmonic properties

NASA Astrophysics Data System (ADS)

DeSantis, Christopher John

There has been much interest in colloidal noble metal nanoparticles due to their fascinating plasmonic and catalytic properties. These properties make noble metal nanoparticles potentially useful for applications such as targeted drug delivery agents and hydrogen storage devices. Historically, shape-controlled noble metal nanoparticles have been predominantly monometallic. Recent synthetic advances provide access to bimetallic noble metal nanoparticles wherein their inherent multifunctionality and ability to fine tune or expand their surface chemistry and light scattering properties of metal nanoparticles make them popular candidates for many applications. Even so, there are currently few synthetic strategies to rationally design shape-controlled bimetallic nanocrystals; for this reason, few architectures are accessible. For example, the "seed-mediated method" is a popular means of achieving monodisperse shape-controlled bimetallic nanocrystals. In this process, small metal seeds are used as platforms for additional metal addition, allowing for conformal core shell nanostructures. However, this method has only been applied to single metal core/single metal shell structures; therefore, the surface compositions and architectures achievable are limited. This thesis expands upon the seed-mediated method by coupling it with co-reduction. In short, two metal precursors are simultaneously reduced to deposit metal onto pre-formed seeds in hopes that the interplay between two metal species facilitates bimetallic shell nanocrystals. Au/Pd was used as a test system due to favorable reduction potentials of metal precursors and good lattice match between Au and Pd. Alloyed shelled Au Au/Pd nanocrystals were achieved using this "seed-mediated co-reduction" approach. Symmetric eight-branched Au/Pd nanocrystals (octopods) are also prepared using this method. This thesis investigates many synthetic parameters that determine the shape outcome in Au/Pd nanocrystals during seed-mediated co-reduction. Plasmonic, catalytic, and assembly properties are also investigated in relation to nanocrystal shape and architecture. This work provides a foundation for the rational design of architecturally defined bimetallic nanostructures.

Colorimetric detection with aptamer-gold nanoparticle conjugates coupled to an android-based color analysis application for use in the field.

PubMed

Smith, Joshua E; Griffin, Daniel K; Leny, Juliann K; Hagen, Joshua A; Chávez, Jorge L; Kelley-Loughnane, Nancy

2014-04-01

The feasibility of using aptamer-gold nanoparticle conjugates (Apt-AuNPs) to design colorimetric assays for in the field detection of small molecules was investigated. An assay to detect cocaine was designed using two clones of a known cocaine-binding aptamer. The assay was based on the AuNPs difference in affinity for single-stranded DNA (non-binding) and double stranded DNA (target bound). In the first assay, a commonly used design was followed, in which the aptamer and target were incubated to allow binding followed by exposure to the AuNPs. Interactions between the non-bound analytes and the AuNPs surface resulted in a number of false positives. The assay was redesigned by incubating the AuNPs and the aptamer prior to target addition to passivate the AuNPs surface. The adsorbed aptamer was able to bind the target while preventing non-specific interactions. The assay was validated with a number of masking and cutting agents and other controlled substances showing minimal false positives. Studies to improve the assay performance in the field were performed, showing that assay activity could be preserved for up to 2 months. To facilitate the assay analysis, an android application for automatic colorimetric characterization was developed. The application was validated by challenging the assay with cocaine standards of different concentrations, and comparing the results to a conventional plate reader, showing outstanding agreement. Finally, the rapid identification of cocaine in mixtures mimicking street samples was demonstrated. This work established that Apt-AuNPs can be used to design robust assays to be used in the field. Copyright © 2013 Elsevier B.V. All rights reserved.

Magnetic nanomotor fabrication by plasma coating method and its biological application

NASA Astrophysics Data System (ADS)

Oksuz, Lutfi; Yurdabak Karaca, Gozde; Uygun, Emre; Uygun Oksuz, Aysegul

2017-10-01

Nano/micro scale motors are exciting research area due to a wide range of application area especially offer considerable promise for the diagnosis and treatment of the diseases. In this scope, the preparation and characterization of Gold (Au)/ Nickel (Ni) nanomotors transport and their applications based on the detection of miRNA-21 will be examined. In addition, magnetic segment Ni which was coated by RF magnetron sputter technique on to the electrochemical synthesized Au nanowire can also be used to focus on the controlled movement and target. We propose a sensitive stable plasma coated magnetic nanomotor-based approach for miRNA-21 detection for simple and cancer diagnosis.

Confined Pattern-Directed Assembly of Polymer-Grafted Nanoparticles in a Phase Separating Blend with a Homopolymer Matrix.

PubMed

Zhang, Ren; Lee, Bongjoon; Bockstaller, Michael R; Douglas, Jack F; Stafford, Christopher M; Kumar, Sanat K; Raghavan, Dharmaraj; Karim, Alamgir

The controlled organization of nanoparticle (NP) constituents into superstructures of well-defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. We show that the phase separation of polymer-tethered nanoparticles immersed in a chemically different polymer matrix provides an effective and scalable method for fabricating defined submicron-sized amorphous NP domains in melt polymer thin films. We investigate this phenomenon with a view towards understanding and controlling the phase separation process through directed nanoparticle assembly. In particular, we consider isothermally annealed thin films of polystyrene-grafted gold nanoparticles (AuPS) dispersed in a poly(methyl methacrylate) (PMMA) matrix. Classic binary polymer blend phase separation related morphology transitions, from discrete AuPS domains to bicontinuous to inverse domain structure with increasing nanoparticle composition is observed, yet the kinetics of the AuPS/PMMA polymer blends system exhibit unique features compared to the parent PS/PMMA homopolymer blend. We further illustrate how to pattern-align the phase-separated AuPS nanoparticle domain shape, size and location through the imposition of a simple and novel external symmetry-breaking perturbation via soft-lithography. Specifically, submicron-sized topographically patterned elastomer confinement is introduced to direct the nanoparticles into kinetically controlled long-range ordered domains, having a dense yet well-dispersed distribution of non-crystallizing nanoparticles. The simplicity, versatility and roll-to-roll adaptability of this novel method for controlled nanoparticle assembly should make it useful in creating desirable patterned nanoparticle domains for a variety of functional materials and applications.

Molecule-specific darkfield and multiphoton imaging using gold nanocages

NASA Astrophysics Data System (ADS)

Powless, Amy J.; Jenkins, Samir V.; McKay, Mary Lee; Chen, Jingyi; Muldoon, Timothy J.

2015-03-01

Due to their robust optical properties, biological inertness, and readily adjustable surface chemistry, gold nanostructures have been demonstrated as contrast agents in a variety of biomedical imaging applications. One application is dynamic imaging of live cells using bioconjugated gold nanoparticles to monitor molecule trafficking mechanisms within cells; for instance, the regulatory pathway of epidermal growth factor receptor (EGFR) undergoing endocytosis. In this paper, we have demonstrated a method to track endocytosis of EGFR in MDA-MB-468 breast adenocarcinoma cells using bioconjugated gold nanocages (AuNCs) and multiphoton microscopy. Dynamic imaging was performed using a time series capture of 4 images every minute for one hour. Specific binding and internalization of the bioconjugated AuNCs was observed while the two control groups showed non-specific binding at fewer surface sites, leading to fewer bound AuNCs and no internalization.

Shape-Controllable Gold Nanoparticle-MoS2 Hybrids Prepared by Tuning Edge-Active Sites and Surface Structures of MoS2 via Temporally Shaped Femtosecond Pulses.

PubMed

Zuo, Pei; Jiang, Lan; Li, Xin; Li, Bo; Xu, Yongda; Shi, Xuesong; Ran, Peng; Ma, Tianbao; Li, Dawei; Qu, Liangti; Lu, Yongfeng; Grigoropoulos, Costas P

2017-03-01

Edge-active site control of MoS 2 is crucial for applications such as chemical catalysis, synthesis of functional composites, and biochemical sensing. This work presents a novel nonthermal method to simultaneously tune surface chemical (edge-active sites) and physical (surface periodic micro/nano structures) properties of MoS 2 using temporally shaped femtosecond pulses, through which shape-controlled gold nanoparticles are in situ and self-assembly grown on MoS 2 surfaces to form Au-MoS 2 hybrids. The edge-active sites with unbound sulfurs of laser-treated MoS 2 drive the reduction of gold nanoparticles, while the surface periodic structures of laser-treated MoS 2 assist the shape-controllable growth of gold nanoparticles. The proposed novel method highlights the broad application potential of MoS 2 ; for example, these Au-MoS 2 hybrids exhibit tunable and highly sensitive SERS activity with an enhancement factor up to 1.2 × 10 7 , indicating the marked potential of MoS 2 in future chemical and biological sensing applications.

Synthesis and study of catalytic application of l-methionine protected gold nanoparticles

NASA Astrophysics Data System (ADS)

Raza, Akif; Javed, Safdar; Qureshi, Muhammad Zahid; khan, Muhammad Usman; Khan, Muhammad Saleem

2017-10-01

Gold nanoparticle is growing class of nanotechnology due to large number of uses. We synthesized stable l-methionine protected gold nanoparticles (AuNps) by in situ reduction of HAuCl4 using sodium borohydrate as reducing and l-methionine as stabilizing agent in an aqueous medium. Different parameters (pH, capping agent, precursor salt, and heating time) were optimized to see the effect on the size of particles. Double beam spectrophotometer was used to carry out the spectroscopic studies. It was observed that pH and concentration of reducing salt are deciding factors in controlling the size and morphology of AuNps. Scanning electron microscopy (SEM) verified the formation of AuNPs as predicted by UV-Vis spectra. The interaction of AuNPs with l-methionine was confirmed by Fourier Transform Infrared (FTIR). The reduction of 4-nitrophenol acted as standard of reaction to check the response of AuNps catalyst. Complete reduction of 4-nitrophenol was accomplished by AuNps sol in just 60 s. Fastest reduction rate was observed with smaller spherical particles. This study concluded that size and shape of AuNps can be monitored by controlling the pH, concentration of capping and reducing agent. It also provides an economical solution to aquatic environment in terms of time saving and use of small volume of catalytic solution for reduction of several other toxic organic pollutants.

A one-pot strategy for biomimetic synthesis and self-assembly of gold nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Yi; Chen, Li Qiang; Li, Yuan Fang; Zhao, Xi Juan; Peng, Li; Zhi Huang, Cheng

2010-07-01

A simple, one-pot and controllable strategy is reported in this contribution for biomimetic synthesis and self-assembly of gold nanoparticles (Au-NPs). It involves our synthesized polyaldehyde dextran (PAD), which has been proved to be a biomacromolecule with excellent biocompatibility and biodegradability, acting as both a reducing agent and a stabilizer. The morphology of the as-prepared Au-NP assemblies can be controlled by adjusting the reaction conditions, such as the concentration of aldehyde in PAD, the reaction time and the temperature. Investigations of the mechanism suggest that stabilizers may distribute on different crystal facets of NPs non-uniformly owing to the different binding forces, and dipole-dipole interaction of NPs could be the main driving force for the assembly of Au-NPs. In addition, intermolecular hydrogen bonding interaction of stabilizers could also act as a possible driving force. The excellent biocompatibility of the Au-NP assemblies makes them promising candidates for fabricating future optical nanodevices and application in biological systems.

A general soft-enveloping strategy in the templating synthesis of mesoporous metal nanostructures.

PubMed

Fang, Jixiang; Zhang, Lingling; Li, Jiang; Lu, Lu; Ma, Chuansheng; Cheng, Shaodong; Li, Zhiyuan; Xiong, Qihua; You, Hongjun

2018-02-06

Metal species have a relatively high mobility inside mesoporous silica; thus, it is difficult to introduce the metal precursors into silica mesopores and suppress the migration of metal species during a reduction process. Therefore, until now, the controlled growth of metal nanocrystals in a confined space, i.e., mesoporous channels, has been very challenging. Here, by using a soft-enveloping reaction at the interfaces of the solid, liquid, and solution phases, we successfully control the growth of metallic nanocrystals inside a mesoporous silica template. Diverse monodispersed nanostructures with well-defined sizes and shapes, including Ag nanowires, 3D mesoporous Au, AuAg alloys, Pt networks, and Au nanoparticle superlattices are successfully obtained. The 3D mesoporous AuAg networks exhibit enhanced catalytic activities in an electrochemical methanol oxidation reaction. The current soft-enveloping synthetic strategy offers a robust approach to synthesize diverse mesoporous metal nanostructures that can be utilized in catalysis, optics, and biomedicine applications.

Kinetically controlled synthesis of Au102(SPh)44 nanoclusters and catalytic application

NASA Astrophysics Data System (ADS)

Chen, Yongdong; Wang, Jin; Liu, Chao; Li, Zhimin; Li, Gao

2016-05-01

We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au102(SPh)44 nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S(&z.dbd;O)-R' sulfoxides). The Au102(SPh)44/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process.We here explore a kinetically controlled synthetic protocol for preparing solvent-solvable Au102(SPh)44 nanoclusters which are isolated from polydispersed gold nanoclusters by solvent extraction and size exclusion chromatography (SEC). The as-obtained Au102(SPh)44 nanoclusters are determined by matrix-assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometry, in conjunction with UV-vis spectroscopy and thermogravimetric analysis (TGA). However, Au99(SPh)42, instead of Au102(SPh)44, is yielded when the polydispersed gold nanoclusters are etched in the presence of excess thiophenol under thermal conditions (e.g., 80 °C). Interestingly, the Au102(SPh)44 nanoclusters also can convert to Au99(SPh)42 with equivalent thiophenol ligands, evidenced by the analyses of UV-vis and MALDI mass spectrometry. Finally, the TiO2-supported Au102(SPh)44 nanocluster catalyst is investigated in the selective oxidation of sulfides into sulfoxides by the PhIO oxidant and gives rise to high catalytic activity (e.g., 80-99% conversion of R-S-R' sulfides with 96-99% selectivity for R-S(&z.dbd;O)-R' sulfoxides). The Au102(SPh)44/TiO2 catalyst also shows excellent recyclability in the sulfoxidation process. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08338a

Highly sensitive and robust peroxidase-like activity of Au-Pt core/shell nanorod-antigen conjugates for measles virus diagnosis.

PubMed

Long, Lin; Liu, Jianbo; Lu, Kaishun; Zhang, Tao; Xie, Yunqing; Ji, Yinglu; Wu, Xiaochun

2018-05-02

As a promising candidate for artificial enzymes, catalytically active nanomaterials show several advantages over natural enzymes, such as controlled synthesis at low cost, tunability of catalytic activities, and high stability under stringent conditions. Rod-shaped Au-Pt core/shell nanoparticles (Au@Pt NRs), prepared by Au nanorod-mediated growth, exhibit peroxidase-like activities and could serve as an inexpensive replacement for horseradish peroxidase, with potential applications in various bio-detections. The determination of measles virus is accomplished by a capture-enzyme-linked immunosorbent assay (ELISA) using Au@Pt NR-antigen conjugates. Based on the enhanced catalytic properties of this nanozyme probe, a linear response was observed up to 10 ng/mL measles IgM antibodies in human serum, which is 1000 times more sensitive than commercial ELISA. Hence, these findings provide positive proof of concept for the potential of Au@Pt NR-antigen conjugates in the development of colorimetric biosensors that are simple, robust, and cost-effective.

Effects of Two Application Methods of Plantaricin BM-1 on Control of Listeria monocytogenes and Background Spoilage Bacteria in Sliced Vacuum-Packaged Cooked Ham Stored at 4°C.

PubMed

Zhou, Huimin; Xie, Yuanhong; Liu, Hui; Jin, Junhua; Duan, Huixia; Zhang, Hongxing

2015-10-01

Two application methods were used to investigate the effect of plantaricin BM-1 on the control of Listeria monocytogenes and background spoilage bacteria in sliced vacuum-packaged cooked ham without the addition of any chemical preservatives, including sodium nitrite, during 35 days of storage at 4°C. Regardless of the application method, plantaricin BM-1 treatment (320, 640, or 1,280 arbitrary units [AU]/g of sliced cooked ham) significantly (P < 0.05) reduced the survival of L. monocytogenes (inoculated at 4 log CFU/g of sliced ham) compared with its survival in the control during the first 21 days of storage at 4°C. The inhibitory effect of plantaricin applied to the surface of the ham was significantly better than the same concentration of plantaricin incorporated into the cooked ham (P < 0.0001) during storage. Even 320 AU/g plantaricin applied to the surface exhibited greater inhibition of L. monocytogenes than 1,280 AU/g plantaricin incorporated into the cooked ham on days 1, 14, and 28. A level of 1,280 AU/g plantaricin applied to the surface of the ham reduced L. monocytogenes counts to below the detection limit from the 1st to the 21st day of storage at 4°C. Afterwards, L. monocytogenes was able to regrow, and the viable counts of L. monocytogenes at the end of storage reached 2.76 log CFU/g (6.11 log CFU/g lower than in the control). In the control ham, the counts of background spoilage bacteria increased gradually and surpassed the microbiological spoilage limitation level on the 21st day of storage. However, plantaricin BM-1 treatment significantly (P < 0.05) reduced the survival of background spoilage bacteria in ham compared with their survival in the control from day 21 to 35 of storage at 4°C. A level of 1,280 AU/g plantaricin incorporated into cooked ham was the most effective, reducing the count of background spoilage bacteria count from an initial 2.0 log CFU/g to 1.5 log CFU/g on day 7. This was then maintained for another 14 days and finally increased to 2.76 log CFU/g at the end of the storage at 4°C (2.85 log CFU/g lower than in the control). In conclusion, plantaricin BM-1 application inhibited the growth of L. monocytogenes and background spoilage bacteria in cooked ham during storage at 4°C and could be used as an antimicrobial additive for meat preservation.

Putting gold nanocages to work for optical imaging, controlled release and cancer theranostics

PubMed Central

Pang, Bo; Yang, Xuan; Xia, Younan

2016-01-01

Gold nanocages are hollow nanostructures with ultrathin, porous walls. They are bio-inert and their surface can be readily modified with functional groups to specifically interact with the biological system of interest. They have remarkable optical properties, including localized surface plasmon resonance peaks tunable to the near-infrared region, strong absorption and scattering, as well as two- and three-photon luminescence. With the establishment of robust protocols for both synthesis and surface functionalization, Au nanocages have been extensively explored for various biomedical applications. In this review, we begin with a brief account of the synthesis and properties of Au nanocages, and then highlight some of the recent developments in applying them to an array of biomedical applications related to optical imaging, controlled release and cancer theranostics. PMID:27348546

Unconventional route to encapsulated ultrasmall gold nanoparticles for high-temperature catalysis.

PubMed

Zhang, Tingting; Zhao, Hongyu; He, Shengnan; Liu, Kai; Liu, Hongyang; Yin, Yadong; Gao, Chuanbo

2014-07-22

Ultrasmall gold nanoparticles (us-AuNPs, <3 nm) have been recently recognized as surprisingly active and extraordinarily effective green catalysts. Their stability against sintering during reactions, however, remains a serious issue for practical applications. Encapsulating such small nanoparticles in a layer of porous silica can dramatically enhance the stability, but it has been extremely difficult to achieve using conventional sol-gel coating methods due to the weak metal/oxide affinity. In this work, we address this challenge by developing an effective protocol for the synthesis of us-AuNP@SiO2 single-core/shell nanospheres. More specifically, we take an alternative route by starting with ultrasmall gold hydroxide nanoparticles, which have excellent affinity to silica, then carrying out controllable silica coating in reverse micelles, and finally converting gold hydroxide particles into well-protected us-AuNPs. With a single-core/shell configuration that prevents sintering of nearby us-AuNPs and amino group modification of the Au/SiO2 interface that provides additional coordinating interactions, the resulting us-AuNP@SiO2 nanospheres are highly stable at high temperatures and show high activity in catalytic CO oxidation reactions. A dramatic and continuous increase in the catalytic activity has been observed when the size of the us-AuNPs decreases from 2.3 to 1.5 nm, which reflects the intrinsic size effect of the Au nanoparticles on an inert support. The synthesis scheme described in this work is believed to be extendable to many other ultrasmall metal@oxide nanostructures for much broader catalytic applications.

Detection of cell surface calreticulin as a potential cancer biomarker using near-infrared emitting gold nanoclusters

NASA Astrophysics Data System (ADS)

Subramaniyam Ramesh, Bala; Giorgakis, Emmanouil; Lopez-Davila, Victor; Kamali Dashtarzheneha, Ashkan; Loizidou, Marilena

2016-07-01

Calreticulin (CRT) is a cytoplasmic calcium-binding protein. The aim of this study was to investigate CRT presence in cancer with the use of fluorescent gold nanoclusters (AuNCs) and to explore AuNC synthesis using mercaptosuccinic acid (MSA) as a coating agent. MSA-coated AuNCs conferred well-dispersed, bio-stable, water-soluble nanoparticles with bioconjugation capacity and 800-850 nm fluorescence after broad-band excitation. Cell-viability assay revealed good AuNC tolerability. A native CRT amino-terminus corresponding peptide sequence was synthesised and used to generate rabbit site-specific antibodies. Target specificity was demonstrated with antibody blocking in colorectal and breast cancer cell models; human umbilical vein endothelial cells served as controls. We demonstrated a novel route of AuNC/MSA manufacture and CRT presence on colonic and breast cancerous cell surface. AuNCs served as fluorescent bio-probes specifically recognising surface-bound CRT. These results are promising in terms of AuNC application in cancer theranostics and CRT use as surface biomarker in human cancer.

Gold nanoparticles: From nanomedicine to nanosensing

PubMed Central

Chen, Po C; Mwakwari, Sandra C; Oyelere, Adegboyega K

2008-01-01

Because of their photo-optical distinctiveness and biocompatibility, gold nanoparticles (AuNPs) have proven to be powerful tools in various nanomedicinal and nanomedical applications. In this review article, we discuss recent advances in the application of AuNPs in diagnostic imaging, biosensing and binary cancer therapeutic techniques. We also provide an eclectic collection of AuNPs delivery strategies, including assorted classes of delivery vehicles, which are showing great promise in specific targeting of AuNPs to diseased tissues. However, successful clinical implementations of the promised applications of AuNPs are still hampered by many barriers. In particular, more still needs to be done regarding our understanding of the pharmacokinetics and toxicological profiles of AuNPs and AuNPs-conjugates. PMID:24198460

Atomically Precise Metal Nanoclusters for Catalytic Application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Rongchao

2016-11-18

The central goal of this project is to explore the catalytic application of atomically precise gold nanoclusters. By solving the total structures of ligand-protected nanoclusters, we aim to correlate the catalytic properties of metal nanoclusters with their atomic/electronic structures. Such correlation unravel some fundamental aspects of nanocatalysis, such as the nature of particle size effect, origin of catalytic selectivity, particle-support interactions, the identification of catalytically active centers, etc. The well-defined nanocluster catalysts mediate the knowledge gap between single crystal model catalysts and real-world conventional nanocatalysts. These nanoclusters also hold great promise in catalyzing certain types of reactions with extraordinarily highmore » selectivity. These aims are in line with the overall goals of the catalytic science and technology of DOE and advance the BES mission “to support fundamental research to understand, predict, and ultimately control matter and energy at the level of electrons, atoms, and molecules”. Our group has successfully prepared different sized, robust gold nanoclusters protected by thiolates, such as Au 25(SR) 18, Au 28(SR) 20, Au 38(SR) 24, Au 99(SR) 42, Au 144(SR) 60, etc. Some of these nanoclusters have been crystallographically characterized through X-ray crystallography. These ultrasmall nanoclusters (< 2 nm diameter) exhibit discrete electronic structures due to quantum size effect, as opposed to quasicontinuous band structure of conventional metal nanoparticles or bulk metals. The available atomic structures (metal core plus surface ligands) of nanoclusters serve as the basis for structure-property correlations. We have investigated the unique catalytic properties of nanoclusters (i.e. not observed in conventional nanogold catalysts) and revealed the structure-selectivity relationships. Highlights of our works include: i) Effects of ligand, cluster charge state, and size on the catalytic reactivity in CO oxidation, semihydrogenation of alkynes; ii) Size-controlled synthesis of Au-n clusters and structural elucidation; iii) Catalytic mechanisms and correlation with structures of cluster catalyst; iv) Catalytic properties of Au nanorods in chemoselective hydrogenation of nitrobenzaldehyde and visible light driven photocatalytic reactions.« less

Heterojunction metal-oxide-metal Au-Fe{sub 3}O{sub 4}-Au single nanowire device for spintronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, K. M., E-mail: mrkongara@boisestate.edu; Punnoose, Alex; Hanna, Charles

2015-05-07

In this report, we present the synthesis of heterojunction magnetite nanowires in alumina template and describe magnetic and electrical properties from a single nanowire device for spintronics applications. Heterojunction Au-Fe-Au nanowire arrays were electrodeposited in porous aluminum oxide templates, and an extensive and controlled heat treatment process converted Fe segment to nanocrystalline cubic magnetite phase with well-defined Au-Fe{sub 3}O{sub 4} interfaces as confirmed by the transmission electron microscopy. Magnetic measurements revealed Verwey transition shoulder around 120 K and a room temperature coercive field of 90 Oe. Current–voltage (I-V) characteristics of a single Au-Fe{sub 3}O{sub 4}-Au nanowire have exhibited Ohmic behavior. Anomalous positivemore » magnetoresistance of about 0.5% is observed on a single nanowire, which is attributed to the high spin polarization in nanowire device with pure Fe{sub 3}O{sub 4} phase and nanocontact barrier. This work demonstrates the ability to preserve the pristine Fe{sub 3}O{sub 4} and well defined electrode contact metal (Au)–magnetite interface, which helps in attaining high spin polarized current.« less

Spatially selective Au nanoparticle growth in laser-quality glass controlled by UV-induced phosphate-chain cross-linkage

NASA Astrophysics Data System (ADS)

Sigaev, Vladimir N.; Savinkov, Vitaly I.; Lotarev, Sergey V.; Shakhgildyan, Georgiy Yu; Lorenzi, Roberto; Paleari, Alberto

2013-06-01

Herein we describe how UV excitation of localized electronic states in phosphate glasses can activate structural rearrangements that influence the kinetics of Au nanoparticle (NP) thermal growth in Au-doped glass. The results suggest a novel strategy to address the problem of controlling nano-assembly processes of metal NP patterns in fully inorganic and chemically stable hard materials, such as laser-quality glasses. We show that the mechanism is promoted by opening and subsequent cross-linkage of phosphate chains under UV excitation of non-bridging groups in the amorphous network of the glass, with a consequent modification of Au diffusion and metal NP growth. Importantly, the micro-Raman mapping of the UV-induced modifications demonstrates that the process is restricted within the beam waist region of the focused UV laser beam. This fact is consistent with the need for more than one excitation event, close in time and in space, in order to promote structural cross-linkage and Au diffusion confinement. The stability of the photo-induced modifications makes it possible to design new metal patterning approaches for the fabrication of three-dimensional metal structures in laser-quality materials for high-power nonlinear applications.

Spatially selective Au nanoparticle growth in laser-quality glass controlled by UV-induced phosphate-chain cross-linkage.

PubMed

Sigaev, Vladimir N; Savinkov, Vitaly I; Lotarev, Sergey V; Shakhgildyan, Georgiy Yu; Lorenzi, Roberto; Paleari, Alberto

2013-06-07

Herein we describe how UV excitation of localized electronic states in phosphate glasses can activate structural rearrangements that influence the kinetics of Au nanoparticle (NP) thermal growth in Au-doped glass. The results suggest a novel strategy to address the problem of controlling nano-assembly processes of metal NP patterns in fully inorganic and chemically stable hard materials, such as laser-quality glasses. We show that the mechanism is promoted by opening and subsequent cross-linkage of phosphate chains under UV excitation of non-bridging groups in the amorphous network of the glass, with a consequent modification of Au diffusion and metal NP growth. Importantly, the micro-Raman mapping of the UV-induced modifications demonstrates that the process is restricted within the beam waist region of the focused UV laser beam. This fact is consistent with the need for more than one excitation event, close in time and in space, in order to promote structural cross-linkage and Au diffusion confinement. The stability of the photo-induced modifications makes it possible to design new metal patterning approaches for the fabrication of three-dimensional metal structures in laser-quality materials for high-power nonlinear applications.

Photochemical Synthesis of Shape-Controlled Nanostructured Gold on Zinc Oxide Nanorods as Photocatalytically Renewable Sensors.

PubMed

Xu, Jia-Quan; Duo, Huan-Huan; Zhang, Yu-Ge; Zhang, Xin-Wei; Fang, Wei; Liu, Yan-Ling; Shen, Ai-Guo; Hu, Ji-Ming; Huang, Wei-Hua

2016-04-05

Biosensors always suffer from passivation that prevents their reutilization. To address this issue, photocatalytically renewable sensors composed of semiconductor photocatalysts and sensing materials have emerged recently. In this work, we developed a robust and versatile method to construct different kinds of renewable biosensors consisting of ZnO nanorods and nanostructured Au. Via a facile and efficient photochemical reduction, various nanostructured Au was obtained successfully on ZnO nanorods. As-prepared sensors concurrently possess excellent sensing capability and desirable photocatalytic cleaning performance. Experimental results demonstrate that dendritic Au/ZnO composite has the strongest surface-enhanced Raman scattering (SERS) enhancement, and dense Au nanoparticles (NPs)/ZnO composite has the highest electrochemical activity, which was successfully used for electrochemical detection of NO release from cells. Furthermore, both of the SERS and electrochemical sensors can be regenerated efficiently for renewable applications via photodegrading adsorbed probe molecules and biomolecules. Our strategy provides an efficient and versatile method to construct various kinds of highly sensitive renewable sensors and might expand the application of the photocatalytically renewable sensor in the biosensing area.

Nondestructive evaluation of a ceramic matrix composite material

NASA Technical Reports Server (NTRS)

Grosskopf, Paul P.; Duke, John C., Jr.

1992-01-01

Monolithic ceramic materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited because of their sensitivity to small imperfections. To overcome this extreme sensitivity to small imperfections, ceramic matrix composite materials have been developed that have the ability to withstand some distributed damage. A borosilicate glass reinforced with several layers of silicon-carbide fiber mat has been studied. Four-point flexure and tension tests were performed not only to determine some of the material properties, but also to initiate a controlled amount of damage within each specimen. Acousto-ultrasonic (AU) measurements were performed periodically during mechanical testing. This paper will compare the AU results to the mechanical test results and data from other nondestructive methods including acoustic emission monitoring and X-ray radiography. It was found that the AU measurements were sensitive to the damage that had developed within the material.

Cross-Reactive Plasmonic Aptasensors for Controlled Substance Identification

PubMed Central

Yoho, Joshua N.; Geier, Brian; Grigsby, Claude C.; Hagen, Joshua A.; Chávez, Jorge L.; Kelley-Loughnane, Nancy

2017-01-01

In this work, we developed an assay to determine if an arbitrary white powder is a controlled substance, given the plasmonic response of aptamer-gold nanoparticle conjugates (Apt-AuNPs). Toward this end, we designed Apt-AuNPs with specific a response to common controlled substances without cross reactivity to chemicals typically used as fillers in street formulations. Plasmonic sensor variation was shown to produce unique data fingerprints for each chemical analyzed, supporting the application of multivariate statistical techniques to annotate unknown samples by chemical similarity. Importantly, the assay takes less than fifteen minutes to run, and requires only a few micrograms of the material, making the proposed assay easily deployable in field operations. PMID:28832512

Simultaneous tracking of drug molecules and carriers using aptamer-functionalized fluorescent superstable gold nanorod-carbon nanocapsules during thermo-chemotherapy

NASA Astrophysics Data System (ADS)

Wang, Xue-Wei; Gao, Wei; Fan, Huanhuan; Ding, Ding; Lai, Xiao-Fang; Zou, Yu-Xiu; Chen, Long; Chen, Zhuo; Tan, Weihong

2016-04-01

Controlling and monitoring the drug delivery process is critical to its intended therapeutic function. Many nanocarrier systems for drug delivery have been successfully developed. However, biocompatibility, stability, and simultaneously tracing drugs and nanocarriers present significant limitations. Herein, we have fabricated a multifunctional nanocomposite by coating the gold nanorod (AuNR) with a biocompatible, superstable and fluorescent carbon layer, obtaining the AuNR@carbon core-shell nanocapsule. In this system, the carbon shell, originally obtained in aqueous glucose solutions and, therefore, biocompatible in physiological environments, could be simply loaded with cell-specific aptamers and therapeutic molecules through π-π interactions, a useful tool for cancer-targeted cellular imaging and therapy. Moreover, such a stable and intrinsic fluorescence effect of the AuNR@carbon enabled simultaneous tracking of released therapeutic molecules and nanocarriers under thermo-chemotherapy. The AuNR@carbons had high surface areas and stable shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications.Controlling and monitoring the drug delivery process is critical to its intended therapeutic function. Many nanocarrier systems for drug delivery have been successfully developed. However, biocompatibility, stability, and simultaneously tracing drugs and nanocarriers present significant limitations. Herein, we have fabricated a multifunctional nanocomposite by coating the gold nanorod (AuNR) with a biocompatible, superstable and fluorescent carbon layer, obtaining the AuNR@carbon core-shell nanocapsule. In this system, the carbon shell, originally obtained in aqueous glucose solutions and, therefore, biocompatible in physiological environments, could be simply loaded with cell-specific aptamers and therapeutic molecules through π-π interactions, a useful tool for cancer-targeted cellular imaging and therapy. Moreover, such a stable and intrinsic fluorescence effect of the AuNR@carbon enabled simultaneous tracking of released therapeutic molecules and nanocarriers under thermo-chemotherapy. The AuNR@carbons had high surface areas and stable shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications. Electronic supplementary information (ESI) available: Experimental details and characterization data for all new compounds. See DOI: 10.1039/c6nr00369a

The synthesis of high yield Au nanoplate and optimized optical properties

NASA Astrophysics Data System (ADS)

Ni, Yuan; Kan, Caixia; Xu, Juan; Liu, Yang

2018-02-01

The applications of Au nanoplates based on the tunable plasmon properties and enhanced electromagnetic field at the sharp tip and straight edges, have generated a great deal of interest in recent years, especially in the fields of the bio-chemical sensing and imaging. In this review, we focus on the synthesis of nanoscale platelike structures by multiple synthetic strategies (such as thermal solution method, seed-mediated method, seedless method, and some greener methods), and explore corresponding growth mechanism in different synthetic approaches. Other than to review the fabrication of Au nanoplates, the purification strategies are also discussed in order to support the applications in various fields. Modifying synthetic method to obtain well-defined nanoplates can tuned optical absorption from visible to near-infrared region. Moreover, the Au nanoplate dimers (vertex-to-vertex and edge-by-edge assemblies) can induce more specific plasmon properties and stronger localized field due to coupling of interparticles. Compared with 0D quasi-spherical nanoparticles and 1D nanorods, the 2D nanoplates can be applied as a good surface-enhanced Raman scattering (SERS) substrate because of the sharp corners and straight edges. This review will provide background information for the controllable synthesis of anisotropic nanoparticles and advance the application of coupled nanostructures.

Atomically precise metal nanoclusters: stable sizes and optical properties

NASA Astrophysics Data System (ADS)

Jin, Rongchao

2015-01-01

Controlling nanoparticles with atomic precision has long been a major dream of nanochemists. Breakthroughs have been made in the case of gold nanoparticles, at least for nanoparticles smaller than ~3 nm in diameter. Such ultrasmall gold nanoparticles indeed exhibit fundamentally different properties from those of the plasmonic counterparts owing to the quantum size effects as well as the extremely high surface-to-volume ratio. These unique nanoparticles are often called nanoclusters to distinguish them from conventional plasmonic nanoparticles. Intense work carried out in the last few years has generated a library of stable sizes (or stable stoichiometries) of atomically precise gold nanoclusters, which are opening up new exciting opportunities for both fundamental research and technological applications. In this review, we have summarized the recent progress in the research of thiolate (SR)-protected gold nanoclusters with a focus on the reported stable sizes and their optical absorption spectra. The crystallization of nanoclusters still remains challenging; nevertheless, a few more structures have been achieved since the earlier successes in Au102(SR)44, Au25(SR)18 and Au38(SR)24 nanoclusters, and the newly reported structures include Au20(SR)16, Au24(SR)20, Au28(SR)20, Au30S(SR)18, and Au36(SR)24. Phosphine-protected gold and thiolate-protected silver nanoclusters are also briefly discussed in this review. The reported gold nanocluster sizes serve as the basis for investigating their size dependent properties as well as the development of applications in catalysis, sensing, biological labelling, optics, etc. Future efforts will continue to address what stable sizes are existent, and more importantly, what factors determine their stability. Structural determination and theoretical simulations will help to gain deep insight into the structure-property relationships.

Size-controlled synthesis of transition metal nanoparticles through chemical and photo-chemical routes

NASA Astrophysics Data System (ADS)

Tangeysh, Behzad

The central objective of this work is developing convenient general procedures for controlling the formation and stabilization of nanoscale transition metal particles. Contemporary interest in developing alternative synthetic approaches for producing nanoparticles arises in large part from expanding applications of the nanomaterials in areas such as catalysis, electronics and medicine. This research focuses on advancing the existing nanoparticle synthetic routes by using a new class of polymer colloid materials as a chemical approach, and the laser irradiation of metal salt solution as a photo-chemical method to attain size and shape selectivity. Controlled synthesis of small metal nanoparticles with sizes ranging from 1 to 5nm is still a continuing challenge in nanomaterial synthesis. This research utilizes a new class of polymer colloid materials as nano-reactors and protective agents for controlling the formation of small transition metal nanoparticles. The polymer colloid particles were formed from cross-linking of dinegatively charged metal precursors with partially protonated poly dimethylaminoethylmethacrylate (PDMAEMA). Incorporation of [PtCl6]2- species into the colloidal particles prior to the chemical reduction was effectively employed as a new strategy for synthesis of unusually small platinum nanoparticles with narrow size distributions (1.12 +/-0.25nm). To explore the generality of this approach, in a series of proof-of-concept studies, this method was successfully employed for the synthesis of small palladium (1.4 +/-0.2nm) and copper nanoparticles (1.5 +/-0.6nm). The polymer colloid materials developed in this research are pH responsive, and are designed to self-assemble and/or disassemble by varying the levels of protonation of the polymer chains. This unique feature was used to tune the size of palladium nanoparticles in a small range from 1nm to 5nm. The procedure presented in this work is a new convenient room temperature route for synthesis of small nanoparticles, and its application can be extended to the formation of other transition metals and alloy nanoparticles. This research also focuses on developing new photo-chemical routes for controlling the size and shape of the nanoparticles through high-intensity ultra-fast laser irradiation of metal salt solution. One of the core objectives of this work is to explore the special capabilities of shaped laser pulses in formation of metal nanoparticles through irradiation of the solutions by using simultaneous spatial and temporal focusing (SSTF). Femtosecond laser irradiation has not yet been widely applied for nanoparticle synthesis, and offers new regimes of energy deposition for synthesis of nanomaterials. Photo-reduction of aqueous [AuCl4]- solution to the gold nanoparticles (AuNPs) has been applied as a model process for optimizing the experimental procedures, and evaluating the potential of shaped laser pulses in the synthesis of AuNPs. Systematic manipulation of the laser parameters and experimental conditions provided effective strategies to control the size of Au nanoparticles in strong laser fields. Varying the concentration of polyethylene glycol (PEG45) as a surfactant effectively tuned the size of AuNPs from 3.9 +/-0.7nm to 11.0 +/-2.4nm, and significantly increased the rate of Au(III) reduction during irradiation. Comparative studies revealed the capability of shaped laser pulses in the generation of smaller and more uniform AuNPs (5.8 +/-1.1nm) relative to the other conventional laser irradiation methods (7.2 +/-2.9nm). Furthermore, a new laser-assisted approach has been developed for selective formation of triangular Au nanoplates in the absence of any surfactant molecule. This method relies on rapid energy deposition by using shaped, ultra-intense laser pulses to generate Au seeds in aqueous [AuCl4]- solution, and the slow post-irradiation reduction of un-reacted [AuCl4]- species by using H2O2 as a mild reducing agent. Variation of the laser irradiation-time was found as an effective strategy to tune the morphology of Au nanomaterials from nanospheres to triangular nanoplates. The surfactant-free Au nanoplates produced in this research can be readily functionalized with a variety of target molecules or surfactants for desirable applications such as biomedicine. The concept of rapid laser processing followed by in situ chemical reduction can be expanded as a general methodology for high-yield production of nanomaterials, and provides a series of new laser dependent parameters for controlling the nanoparticle formation.

Development and testing of gold nanoparticles for drug delivery and treatment of heart failure: a theranostic potential for PPP cardiology.

PubMed

Spivak, Mykola Ya; Bubnov, Rostyslav V; Yemets, Ilya M; Lazarenko, Liudmyla M; Tymoshok, Natalia O; Ulberg, Zoia R

2013-07-29

Nanoscale gold particles (AuNPs) have wide perspectives for biomedical applications because of their unique biological properties, as antioxidative activity and potentials for drug delivery. The aim was to test effects of AuNPs using suggested heart failure rat model to compare with proved medication Simdax, to test gold nanoparticle for drug delivery, and to test sonoporation effect to increase nanoparticles delivery into myocardial cells. We performed biosafety and biocompatibility tests for AuNPs and conjugate with Simdax. For in vivo tests, we included Wistar rats weighing 180-200 g (n = 54), received doxorubicin in cumulative dose of 12.0 mg/kg to model advance heart failure, registered by ultrasonography. We formed six groups: the first three groups of animals received, respectively, 0.06 ml Simdax, AuNPs, and conjugate (AuNPs-Simdax), intrapleurally, and the second three received them intravenously. The seventh group was control (saline). We performed dynamic assessment of heart failure regression in vivo measuring hydrothorax. Sonoporation of gold nanoparticles to cardiomyocytes was tested. We designed and constructed colloidal, spherical gold nanoparticles, AuNPs-Simdax conjugate, both founded biosafety (in cytotoxicity, genotoxicity, and immunoreactivity). In all animals of the six groups after the third day post-medication injection, no ascites and liver enlargement were registered (P < 0.001 vs controls). Conjugate injection showed significantly higher hydrothorax reduction than Simdax injection only (P < 0.01); gold nanoparticle injection showed significantly higher results than Simdax injection (P < 0.05). AuNPs and conjugate showed no significant difference for rat recovery. Difference in rat life continuity was significant between Simdax vs AuNPs (P < 0.05) and Simdax vs conjugate (P < 0.05). Sonoporation enhances AuNP transfer into the cell and mitochondria that were highly localized, superior to controls (P < 0.01 for both). Gold nanoparticles of 30 nm and its AuNPs-Simdax conjugate gave positive results in biosafety and biocompatibility in vitro and in vivo. AuNPs-Simdax and AuNPs have similar significant cardioprotective effects in rats with doxorubicin-induced heart failure, higher than that of Simdax. Intrapleural (local) delivery is preferred over intravenous (systemic) delivery according to all tested parameters. Sonoporation is able to enhance gold nanoparticle delivery to myocardial cells in vivo.

Synthesis, Characterization and Application of Water-soluble Gold and Silver Nanoclusters

NASA Astrophysics Data System (ADS)

Kumar, Santosh

The term `nanotechnology' has emerged as a buzzword since the last few decades. It has found widespread applications across disciplines, from medicine to energy. The synthesis of gold and silver nanoclusters has found much excitement, due to their novel material properties. Seminal work by various groups, including ours, has shown that the size of these clusters can be controlled with atomic precision. This control gives access to tuning the optical and electronic properties. The majority of nanoclusters reported thus far are not water soluble, which limit their applications in biology that requires water-solubility. Going from organic to aqueous phase is by no means a simple task, as it is associated with many challenges. Their stability in the presence of oxygen, difficulty in characterization, and separation of pure nanoclusters are some of the major bottlenecks associated with the synthesis of water-soluble gold nanoclusters. Water-soluble gold nanoclusters hold great potential in biological labeling, bio-catalysis and nano-bioconjugates. To overcome this problem, a new ligand with structural rigidity is needed. After considering various possibilities, we chose Captopril as a candidate ligand. In my thesis research, the synthesis of Au25 nanocluster capped with captopril has been reported. Captopril-protected Au25 nanocluster showed significantly higher thermal stability and enhanced chiroptical properties than the Glutathione-capped cluster, which confirms our initial rationale, that the ligand is critical in protecting the nanocluster. The optical absorption properties of these Au25 nanoclusters are studied and compared to the plasmonic nanoparticles. The high thermal stability and solubility of Au25 cluster capped with Captopril motivated us to explore this ligand for the synthesis of other gold clusters. Captopril is a chiral molecule with two chiral centers. The chiral ligand can induce chirality to the overall cluster, even if the core is achiral. Therefore, to obtain Au38 clusters as an enantiomer, the ligand employed should be chiral. The enantioselective synthesis of Au 38 capped with different chiral ligands has been reported and their chiroptical properties have been compared. The synthesis of a series of water-soluble Au nanoclusters has motivated us to study the effect of capping ligands and the core-size on their steady-state and time-resolved fluorescence properties, since the photoluminescence properties are particularly important for bioimaging and biomedical applications of nanoclusters. To gain fundamental insights into the origin of luminescence in nanoclusters, the effect of temperature on the fluorescence properties of these clusters has also been studied. The different sized nanoclusters ranging from a few dozen atoms to hundreds of atoms form a bridge between discrete atoms and the plasmonic nanocrystals; the latter involves essentially collective electron excitation-a phenomenon well explained by classical physics as opposed to quantum physics. The central question is: at what size does this transition from quantum behavior to classical behavior occur? To unravel this, we have successfully synthesized a series of silver nanoclusters. The precise formula assignment and their structural determination are still ongoing. We have successfully demonstrated the application of these water-soluble Au nanoclusters in photodynamic therapy for the treatment of cancer. We have successfully demonstrated that Au nanocluster system can produce singlet oxygen without the presence of any organic photosensitizers. In a collaborative project with Dr. Peteanu's group, the quenching efficiency of organic dyes by these water soluble nanoclusters is studied in different systems. Overall, this thesis outlines the successful synthesis of a family of water-soluble nanoclusters, their optical, chiroptical and fluorescence properties, as well as some applications of these nanoclusters.

Two-dimensional molybdenum disulphide nanosheet-covered metal nanoparticle array as a floating gate in multi-functional flash memories

NASA Astrophysics Data System (ADS)

Han, Su-Ting; Zhou, Ye; Chen, Bo; Zhou, Li; Yan, Yan; Zhang, Hua; Roy, V. A. L.

2015-10-01

Semiconducting two-dimensional materials appear to be excellent candidates for non-volatile memory applications. However, the limited controllability of charge trapping behaviors and the lack of multi-bit storage studies in two-dimensional based memory devices require further improvement for realistic applications. Here, we report a flash memory consisting of metal NPs-molybdenum disulphide (MoS2) as a floating gate by introducing a metal nanoparticle (NP) (Ag, Au, Pt) monolayer underneath the MoS2 nanosheets. Controlled charge trapping and long data retention have been achieved in a metal (Ag, Au, Pt) NPs-MoS2 floating gate flash memory. This controlled charge trapping is hypothesized to be attributed to band bending and a built-in electric field ξbi between the interface of the metal NPs and MoS2. The metal NPs-MoS2 floating gate flash memories were further proven to be multi-bit memory storage devices possessing a 3-bit storage capability and a good retention capability up to 104 s. We anticipate that these findings would provide scientific insight for the development of novel memory devices utilizing an atomically thin two-dimensional lattice structure.Semiconducting two-dimensional materials appear to be excellent candidates for non-volatile memory applications. However, the limited controllability of charge trapping behaviors and the lack of multi-bit storage studies in two-dimensional based memory devices require further improvement for realistic applications. Here, we report a flash memory consisting of metal NPs-molybdenum disulphide (MoS2) as a floating gate by introducing a metal nanoparticle (NP) (Ag, Au, Pt) monolayer underneath the MoS2 nanosheets. Controlled charge trapping and long data retention have been achieved in a metal (Ag, Au, Pt) NPs-MoS2 floating gate flash memory. This controlled charge trapping is hypothesized to be attributed to band bending and a built-in electric field ξbi between the interface of the metal NPs and MoS2. The metal NPs-MoS2 floating gate flash memories were further proven to be multi-bit memory storage devices possessing a 3-bit storage capability and a good retention capability up to 104 s. We anticipate that these findings would provide scientific insight for the development of novel memory devices utilizing an atomically thin two-dimensional lattice structure. Electronic supplementary information (ESI) available: Energy-dispersive X-ray spectroscopy (EDS) spectra of the metal NPs, SEM image of MoS2 on Au NPs, erasing operations of the metal NPs-MoS2 memory device, transfer characteristics of the standard FET devices and Ag NP devices under programming operation, tapping-mode AFM height image of the fabricated MoS2 film for pristine MoS2 flash memory, gate signals used for programming the Au NPs-MoS2 and Pt NPs-MoS2 flash memories, and data levels recorded for 100 sequential cycles. See DOI: 10.1039/c5nr05054e

Highly Efficient Light-Driven TiO2-Au Janus Micromotors.

PubMed

Dong, Renfeng; Zhang, Qilu; Gao, Wei; Pei, Allen; Ren, Biye

2016-01-26

A highly efficient light-driven photocatalytic TiO2-Au Janus micromotor with wireless steering and velocity control is described. Unlike chemically propelled micromotors which commonly require the addition of surfactants or toxic chemical fuels, the fuel-free Janus micromotor (diameter ∼1.0 μm) can be powered in pure water under an extremely low ultraviolet light intensity (2.5 × 10(-3) W/cm(2)), and with 40 × 10(-3) W/cm(2), they can reach a high speed of 25 body length/s, which is comparable to common Pt-based chemically induced self-electrophoretic Janus micromotors. The photocatalytic propulsion can be switched on and off by incident light modulation. In addition, the speed of the photocatalytic TiO2-Au Janus micromotor can be accelerated by increasing the light intensity or by adding low concentrations of chemical fuel H2O2 (i.e., 0.1%). The attractive fuel-free propulsion performance, fast movement triggering response, low light energy requirement, and precise motion control of the TiO2-Au Janus photocatalytic micromotor hold considerable promise for diverse practical applications.

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst.

PubMed

Wu, Chien-Chen; Chen, Dong-Hwang

2012-06-19

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe3O4 nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe3O4 nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles.

Spontaneous synthesis of gold nanoparticles on gum arabic-modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst

PubMed Central

2012-01-01

A novel magnetically recoverable Au nanocatalyst was fabricated by spontaneous green synthesis of Au nanoparticles on the surface of gum arabic-modified Fe3O4 nanoparticles. A layer of Au nanoparticles with thickness of about 2 nm was deposited on the surface of gum arabic-modified Fe3O4 nanoparticles, because gum arabic acted as a reducing agent and a stabilizing agent simultaneously. The resultant magnetically recoverable Au nanocatalyst exhibited good catalytic activity for the reduction of 4-nitrophenol with sodium borohydride. The rate constants evaluated in terms of pseudo-first-order kinetic model increased with increase in the amount of Au nanocatalyst or decrease in the initial concentration of 4-nitrophenol. The kinetic data suggested that this catalytic reaction was diffusion-controlled, owing to the presence of gum arabic layer. In addition, this nanocatalyst exhibited good stability. Its activity had no significant decrease after five recycles. This work is useful for the development and application of magnetically recoverable Au nanocatalyst on the basis of green chemistry principles. PMID:22713480

Z-scan studies of the nonlinear optical properties of gold nanoparticles prepared by electron beam deposition.

PubMed

Mezher, M H; Nady, A; Penny, R; Chong, W Y; Zakaria, R

2015-11-20

This paper details the fabrication process for placing single-layer gold (Au) nanoparticles on a planar substrate, and investigation of the resulting optical properties that can be exploited for nonlinear optics applications. Preparation of Au nanoparticles on the substrate involved electron beam deposition and subsequent thermal dewetting. The obtained thin films of Au had a variation in thicknesses related to the controllable deposition time during the electron beam deposition process. These samples were then subjected to thermal annealing at 600°C to produce a randomly distributed layer of Au nanoparticles. Observation from field-effect scanning electron microscope (FESEM) images indicated the size of Au nanoparticles ranges from ∼13 to ∼48  nm. Details of the optical properties related to peak absorption of localized surface plasmon resonance (LSPR) of the nanoparticle were revealed by use of UV-Vis spectroscopy. The Z-scan technique was used to measure the nonlinear effects on the fabricated Au nanoparticle layers where it strongly relates LSPR and nonlinear optical properties.

Green synthesis and characterization of size tunable silica-capped gold core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Wangoo, Nishima; Shekhawat, Gajendra; Wu, Jin-Song; Bhasin, Aman K. K.; Suri, C. R.; Bhasin, K. K.; Dravid, Vinayak

2012-08-01

Silica-coated gold nanoparticles (Au@SiO2) with controlled silica-shell thickness were prepared by a modified Stober's method using 10-nm gold nanoparticles (AuNPs) as seeds. The AuNPs were silica-coated with a sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica source and ammonia as a catalyst. An increase in TEOS concentration resulted in an increase in shell thickness. The NPs were characterized by transmission electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectroscopy, scanning near-field ultrasound holography and scanning transmission electron microscopy. The method required no surface modification and the synthesized core shell nanoparticles can be used for various types of biological applications.

Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001).

PubMed

Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

2015-01-01

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots.

Systematic Study on the Self-Assembled Hexagonal Au Voids, Nano-Clusters and Nanoparticles on GaN (0001)

PubMed Central

Pandey, Puran; Sui, Mao; Li, Ming-Yu; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

2015-01-01

Au nano-clusters and nanoparticles (NPs) have been widely utilized in various electronic, optoelectronic, and bio-medical applications due to their great potentials. The size, density and configuration of Au NPs play a vital role in the performance of these devices. In this paper, we present a systematic study on the self-assembled hexagonal Au voids, nano-clusters and NPs fabricated on GaN (0001) by the variation of annealing temperature and deposition amount. At relatively low annealing temperatures between 400 and 600°C, the fabrication of hexagonal shaped Au voids and Au nano-clusters are observed and discussed based on the diffusion limited aggregation model. The size and density of voids and nano-clusters can systematically be controlled. The self-assembled Au NPs are fabricated at comparatively high temperatures from 650 to 800°C based on the Volmer-Weber growth model and also the size and density can be tuned accordingly. The results are symmetrically analyzed and discussed in conjunction with the diffusion theory and thermodynamics by utilizing AFM and SEM images, EDS maps and spectra, FFT power spectra, cross-sectional line-profiles and size and density plots. PMID:26285135

Controlling T c of Iridium films using interfacial proximity effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hennings-Yeomans, R; Chang, CL; Ding, J

High precision calorimetry using superconducting transition edge sensors requires the use of superconducting films with a suitable T c, depending on the application. To advance high-precision macrocalorimetry, we require low-T c films that are easy to fabricate. A simple and effective way to suppress T c of superconducting Iridium through the proximity effect is demonstrated by using Ir/Pt bilayers as well as Au/Ir/Au trilayers. While Ir/Au films fabricated by applying heat to the substrate during Ir deposition have been used in the past for superconducting sensors, we present results of T c suppression on Iridium by deposition at room temperature in Au/Ir/Au trilayers and Ir/Pt bilayers in the range ofmore » $$\\sim$$20-100~mK. Measurements of the relative impedance between the Ir/Pt bilayers and Au/Ir/Au trilayers fabricated show factor of $$\\sim$$10 higher values in the Ir/Pt case. These new films could play a key role in the development of scalable superconducting transition edge sensors that require low-T c films to minimize heat capacity and maximize energy resolution, while keeping high-yield fabrication methods.« less

Promotion of SH-SY5Y Cell Growth by Gold Nanoparticles Modified with 6-Mercaptopurine and a Neuron-Penetrating Peptide

NASA Astrophysics Data System (ADS)

Xiao, Yaruo; Zhang, Enqi; Fu, Ailing

2017-12-01

Much effort has been devoted to the discovery of effective biomaterials for nerve regeneration. Here, we reported a novel application of gold nanoparticles (AuNPs) modified with 6-mercaptopurine (6MP) and a neuron-penetrating peptide (RDP) as a neurophic agent to promote proliferation and neurite growth of human neuroblastoma (SH-SY5Y) cells. When the cells were treated with 6MP-AuNPs-RDP conjugates, they showed higher metabolic activity than the control. Moreover, SH-SY5Y cells were transplanted onto the surface coated with 6MP-AuNPs-RDP to examine the effect of neurite development. It can be concluded that 6MP-AuNPs-RDP attached to the cell surface and then internalized into cells, leading to a significant increase of neurite growth. Even though 6MP-AuNPs-RDP-treated cells were recovered from frozen storage, the cells still maintained constant growth, indicating that the cells have excellent tolerance to 6MP-AuNPs-RDP. The results suggested that the 6MP-AuNPs-RDP had promising potential to be developed as a neurophic nanomaterial for neuronal growth.

2,3-Pyridine dicarboxylic acid functionalized gold nanoparticles: Insight into experimental conditions for Cr3 + sensing

NASA Astrophysics Data System (ADS)

Shaikh, Ruqaya; Memon, Najma; Solangi, Amber R.; Shaikh, Huma I.; Agheem, Muhammad Hassan; Ali, Syed Abid; Shah, Muhammad Raza; Kandhro, Aftab

2017-02-01

Selectivity of gold nanoparticles (AuNPs) depends upon surface functionality; small changes in structure or concentration bring significant changes in the behavior of AuNPs. In this study, citrate-capped AuNPs were functionalized with ortho-dicarboxylate substituted pyridine (2,3-PDCA) and detailed studies on experimental conditions were carried out to check the stability of AuNPs and response for Cr3 +. Stability of PDCA-AuNPs was found sensitive to the pH, ionic strength of buffer and its type. Capping behavior of PDCA on C-AuNPs was examined by FTIR spectroscopy. Surface morphology and size of synthesized AuNPs were confirmed by AFM, XRD, and DLS techniques where particles were found 11 nm in size, monodisperse and spherical in shape. Interaction of stabilized AuNPs was tested with various metal ions; where Cr3 + induced the changes in localized surface plasmon band (LSPR) of PDCA-AuNPs which leads to a color change from wine red to violet blue. The phenomenon is explained as cooperative effect of citrate and pyridine nitrogen on surface of AuNPs in contrary to meta-dicarboxylate substituted pyridine derivatives. Further, under optimized and controlled conditions Cr3 + shows linear response with decrease in absorbance at LSPR intensity of AuNPs (518 nm). Moreover, to demonstrate the applicability of method, Cr3 + was determined in the presence of Cr (VI) which shows 96% recovery.

Manipulating the optical properties of dual implanted Au and Zn nanoparticles in sapphire

NASA Astrophysics Data System (ADS)

Epie, E. N.; Scott, D.; Chu, W. K.

2017-11-01

We have synthesized and manipulated the optical properties of metallic nanoparticles (NPs) by using a combination of low-energy high-fluence dual implantation and thermal annealing. We demonstrated that by implanting Zn before Au, the resulting absorption peak is enormously blue-shifted by 120 nm with respect to that of Au-only implanted samples. This magnitude of optical shift is not characteristic of unalloyed Au and to the best of our knowledge cannot be attributed to NP size change alone. On the other hand, the absorption peak for samples implanted with Au followed by Zn is blue-shifted about 20 nm. Additionally, by carefully annealing all implanted samples, both NP size distribution and corresponding optical properties can be further modified in a controlled manner. We attribute these behaviours to nanoalloy formation. This work provides a direct method for synthesizing and manipulating both the plasmonic and structural properties of metallic alloy NP in various transparent dielectrics for diverse applications.

Au nanoinjectors for electrotriggered gene delivery into the cell nucleus.

PubMed

Kang, Mijeong; Kim, Bongsoo

2015-01-01

Intracellular delivery of exogenous materials is an essential technique required for many fundamental biological researches and medical treatments. As our understanding of cell structure and function has been improved and diverse therapeutic agents with a subcellular site of action have been continuously developed, there is a demand to enhance the performance of delivering devices. Ideal intracellular delivery devices should convey various kinds of exogenous materials without deteriorating cell viability regardless of cell type and, furthermore, precisely control the location and the timing of delivery as well as the amount of delivered materials for advanced researches.In this chapter the development of a new intracellular delivery device, a nanoinjector made of a Au (gold) nanowire (a Au nanoinjector) is described in which delivery is triggered by external application of an electric pulse. As a model study, a gene was delivered directly into the nucleus of a neuroblastoma cell, and successful delivery without cell damage was confirmed by the expression of the delivered gene. The insertion of a Au nanoinjector directly into a cell can be generally applied to any kind of cell, and a high degree of surface modification of Au allows attachment of diverse materials such as proteins, small molecules, or nanoparticles as well as genes on Au nanoinjectors. This expands their applicability, and it is expected that they will provide important information on the effects of delivered exogenous materials and consequently contribute to the development of related therapeutic or clinical technologies.

Engineering ultrasmall water-soluble gold and silver nanoclusters for biomedical applications.

PubMed

Luo, Zhentao; Zheng, Kaiyuan; Xie, Jianping

2014-05-25

Gold and silver nanoclusters or Au/Ag NCs with core sizes smaller than 2 nm have been an attractive frontier of nanoparticle research because of their unique physicochemical properties such as well-defined molecular structure, discrete electronic transitions, quantized charging, and strong luminescence. As a result of these unique properties, ultrasmall size, and good biocompatibility, Au/Ag NCs have great potential for a variety of biomedical applications, such as bioimaging, biosensing, antimicrobial agents, and cancer therapy. In this feature article, we will first discuss some critical biological considerations, such as biocompatibility and renal clearance, of Au/Ag NCs that are applied for biomedical applications, leading to some design criteria for functional Au/Ag NCs in the biological settings. According to these biological considerations, we will then survey some efficient synthetic strategies for the preparation of protein- and peptide-protected Au/Ag NCs with an emphasis on our recent contributions in this fast-growing field. In the last part, we will highlight some potential biomedical applications of these protein- and peptide-protected Au/Ag NCs. It is believed that with continued efforts to understand the interactions of biomolecule-protected Au/Ag NCs with the biological systems, scientists can largely realize the great potential of Au/Ag NCs for biomedical applications, which could finally pave their way towards clinical use.

Directed Self-Organization of Polymer-Grafted Nanoparticles in Polymer Thin Films

NASA Astrophysics Data System (ADS)

Zhang, Ren

The controlled organization of nanoparticle (NP) constituents into superstructures of well-defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. Surface modification of NPs with grafted polymer ligands has emerged as a versatile means to control the interaction and organization of particle constituents in polymer-matrix composite materials. In this study, by incorporating polymer-grafted nanoparticles (PGNPs) into polymeric thin films, we aim to understand and control the spatial organization of PGNPs through the interactions between polymer brush layer and matrix chains. As model systems, we investigate thermodynamic behaviors of polystyrene-tethered gold nanoparticles (denoted as AuPS) dispersed in polymer thin film matrices with identical and different chemical compositions (PS and PMMA, respectively), and evaluate the influence of external perturbation fields on directed organization of nanofillers. With the presence of unfavorable enthalpic interactions between grafted and free polymer chains (i.e. AuPS/ PMMA blend thin films), phase-separated structures are generated upon thermal annealing, characterized with morphologies ranging from discrete droplets to spinodal structures, which is consistent with composition-dependent classic binary polymer blends phase separation. The phase separation kinetics of AuPS/ PMMA blends exhibit distinct features compared to the parent PS/ PMMA homopolymer blends. We further illustrate phase-separated AuPS-rich domains can be directed into unidirectionally aligned anisotropic structures through soft-shear dynamic zone annealing (DZA-SS) process with tunable domain aspect ratios. To exert exquisite control over the shape, size and location of phase-separated PGNP domains, topographically patterned elastomer confinement is introduced to PGNP/ polymer blend thin films during thermal annealing. When the phase-separated lengthscale coincides with confined pattern dimension, long-range ordered submicron-sized AuPS domains are generated in PMMA matrices with dense and well-dispersed nanoparticle distribution. Furthermore, preferential segregation of AuPS nanoparticles at patterned mesa regions can be induced in PS matrices where enthalpic interactions are absent. This selective segregation is achieved due to the local perturbation of grafted chains when confined in a restricted space. The efficiency of this particle segregation process within patterned mesa-trench films can be tuned by changing the relative entropic confinement effects on grafted and matrix chains. This physical pattern directed PGNP organization strategy is applicable to versatile pattern geometries and nanoparticle compositions.

Multifunctional two-photon active silica-coated Au@MnO Janus particles for selective dual functionalization and imaging.

PubMed

Schick, Isabel; Lorenz, Steffen; Gehrig, Dominik; Schilmann, Anna-Maria; Bauer, Heiko; Panthöfer, Martin; Fischer, Karl; Strand, Dennis; Laquai, Frédéric; Tremel, Wolfgang

2014-02-12

Monodisperse multifunctional and nontoxic Au@MnO Janus particles with different sizes and morphologies were prepared by a seed-mediated nucleation and growth technique with precise control over domain sizes, surface functionalization, and dye labeling. The metal oxide domain could be coated selectively with a thin silica layer, leaving the metal domain untouched. In particular, size and morphology of the individual (metal and metal oxide) domains could be controlled by adjustment of the synthetic parameters. The SiO2 coating of the oxide domain allows biomolecule conjugation (e.g., antibodies, proteins) in a single step for converting the photoluminescent and superparamagnetic Janus nanoparticles into multifunctional efficient vehicles for theranostics. The Au@MnO@SiO2 Janus particles were characterized using high-resolution transmission electron microscopy (HR-)TEM, powder X-ray diffraction (PXRD), optical (UV-vis) spectroscopy, confocal laser fluorescence scanning microscopy (CLSM), and dynamic light scattering (DLS). The functionalized nanoparticles were stable in buffer solution or serum, showing no indication of aggregation. Biocompatibility and potential biomedical applications of the Au@MnO@SiO2 Janus particles were assayed by a cell viability analysis by coincubating the Au@MnO@SiO2 Janus particles with Caki 1 and HeLa cells. Time-resolved fluorescence spectroscopy in combination with CLSM revealed the silica-coated Au@MnO@SiO2 Janus particles to be highly two-photon active; no indication for an electronic interaction between the dye molecules incorporated in the silica shell surrounding the MnO domains and the attached Au domains was found; fluorescence quenching was observed when dye molecules were bound directly to the Au domains.

Internal-Modified Dithiol DNA-Directed Au Nanoassemblies: Geometrically Controlled Self-Assembly and Quantitative Surface-Enhanced Raman Scattering Properties

NASA Astrophysics Data System (ADS)

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-11-01

In this work, a hierarchical DNA-directed self-assembly strategy to construct structure-controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal-modified dithiol single-strand DNA (ssDNA) (Au-B-A or A-B-Au-B-A). It is found that the dithiol-ssDNA-modified Au NPs and molecule quantity of thiol-modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au-DNA self-assembly units, geometrical structures of the Au NAs can be tailored from one-dimensional (1D) to quasi-2D and 2D. Au-B-A conjugates readily give 1D and quasi-2D Au NAs while 2D Au NAs can be formed by A-B-Au-B-A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite-difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”-number-depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique.

Gold nanoparticles prepared by laser ablation in aqueous biocompatible solutions: assessment of safety and biological identity for nanomedicine applications

PubMed Central

Correard, Florian; Maximova, Ksenia; Estève, Marie-Anne; Villard, Claude; Roy, Myriam; Al-Kattan, Ahmed; Sentis, Marc; Gingras, Marc; Kabashin, Andrei V; Braguer, Diane

2014-01-01

Due to excellent biocompatibility, chemical stability, and promising optical properties, gold nanoparticles (Au-NPs) are the focus of research and applications in nanomedicine. Au-NPs prepared by laser ablation in aqueous biocompatible solutions present an essentially novel object that is unique in avoiding any residual toxic contaminant. This paper is conceived as the next step in development of laser-ablated Au-NPs for future in vivo applications. The aim of the study was to assess the safety, uptake, and biological behavior of laser-synthesized Au-NPs prepared in water or polymer solutions in human cell lines. Our results showed that laser ablation allows the obtaining of stable and monodisperse Au-NPs in water, polyethylene glycol, and dextran solutions. The three types of Au-NPs were internalized in human cell lines, as shown by transmission electron microscopy. Biocompatibility and safety of Au-NPs were demonstrated by analyzing cell survival and cell morphology. Furthermore, incubation of the three Au-NPs in serum-containing culture medium modified their physicochemical characteristics, such as the size and the charge. The composition of the protein corona adsorbed on Au-NPs was investigated by mass spectrometry. Regarding composition of complement C3 proteins and apolipoproteins, Au-NPs prepared in dextran solution appeared as a promising drug carrier. Altogether, our results revealed the safety of laser-ablated Au-NPs in human cell lines and support their use for theranostic applications. PMID:25473280

Controllable Fabrication of Au Nanocups by Confined-Space Thermal Dewetting for OCT Imaging.

PubMed

Gao, Aiqin; Xu, Wenjing; Ponce de León, Yenisey; Bai, Yaocai; Gong, Mingfu; Xie, Kongliang; Park, Boris Hyle; Yin, Yadong

2017-07-01

Here, this study reports a novel confined-space thermal dewetting strategy for the fabrication of Au nanocups with tunable diameter, height, and size of cup opening. The nanocup morphology is defined by the cup-shaped void space created by a yolk-shell silica template that spontaneously takes an eccentric configuration during annealing. Thermal dewetting of Au, which is sandwiched between the yolk and shell, leads to the desired nanocup morphology. With strong scattering in near infrared, the Au nanocups exhibit superior efficiency as contrast agents for spectral-domain optical coherence tomography imaging. This confined-space thermal dewetting strategy is scalable and general, and can be potentially extended to the synthesis of novel anisotropic nanostructures of various compositions that are difficult to produce by conventional wet chemical or physical methods, thus opening up opportunities for many new applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aminosilane-Assisted Electrodeposition of Gold Nanodendrites and Their Catalytic Properties

PubMed Central

Hau, Nga Yu; Yang, Peixian; Liu, Chang; Wang, Jian; Lee, Po-Heng; Feng, Shien-Ping

2017-01-01

A promising alternative route for the synthesis of three-dimensional Au dendrites was developed by direct electrodeposition from a solution of HAuCl4 containing 3-aminopropyltriethoxysilane (APTS). Ultraviolet-visible spectroscopy, fourier transform infrared spectroscopy and isothermal titration calorimetry were used to study the interaction of APTS in electrolyte. The effect of APTS on the formation of the hierarchical structure of Au dendrites was investigated by cyclic voltammetry, rotating disk electrode, electrochemical impedance spectroscopy and quartz crystal microbalance. The growth directions of the trunks and branches of the Au dendrites can be controlled by sweep-potential electrodeposition to obtain more regular structures. The efficacy of as-synthesised Au dendrites was demonstrated in the enhanced electro-catalytic activity to methanol electro-oxidation and the high sensitivity of glucose detection, which have potential applications in direct-methanol fuel cells and non-enzymatic electrochemical glucose biosensors, respectively. PMID:28045064

Aminosilane-Assisted Electrodeposition of Gold Nanodendrites and Their Catalytic Properties

NASA Astrophysics Data System (ADS)

Hau, Nga Yu; Yang, Peixian; Liu, Chang; Wang, Jian; Lee, Po-Heng; Feng, Shien-Ping

2017-01-01

A promising alternative route for the synthesis of three-dimensional Au dendrites was developed by direct electrodeposition from a solution of HAuCl4 containing 3-aminopropyltriethoxysilane (APTS). Ultraviolet-visible spectroscopy, fourier transform infrared spectroscopy and isothermal titration calorimetry were used to study the interaction of APTS in electrolyte. The effect of APTS on the formation of the hierarchical structure of Au dendrites was investigated by cyclic voltammetry, rotating disk electrode, electrochemical impedance spectroscopy and quartz crystal microbalance. The growth directions of the trunks and branches of the Au dendrites can be controlled by sweep-potential electrodeposition to obtain more regular structures. The efficacy of as-synthesised Au dendrites was demonstrated in the enhanced electro-catalytic activity to methanol electro-oxidation and the high sensitivity of glucose detection, which have potential applications in direct-methanol fuel cells and non-enzymatic electrochemical glucose biosensors, respectively.

Role of Au(NPs) in the enhanced response of Au(NPs)-decorated MWCNT electrochemical biosensor

PubMed Central

Mehmood, Shahid; Ciancio, Regina; Carlino, Elvio; Bhatti, Arshad S

2018-01-01

Background The combination of Au-metallic-NPs and CNTs are a new class of hybrid nanomaterials for the development of electrochemical biosensor. Concentration of Au(nanoparticles [NPs]) in the electrochemical biosensor is crucial for the efficient charge transfer between the Au-NPs-MWCNTs modified electrode and electrolytic solution. Methods In this work, the charge transfer kinetics in the glassy carbon electrode (GCE) modified with Au(NPs)–multiwalled carbon nanotube (MWCNT) nanohybrid with varied concentrations of Au(NPs) in the range 40–100 nM was studied using electrochemical impedance spectroscopy (EIS). Field emission scanning electron microscopy and transmission electron microscopy confirmed the attachment of Au(NPs) on the surface of MWCNTs. Results The cyclic voltammetry and EIS results showed that the charge transfer mechanism was diffusion controlled and the rate of charge transfer was dependent on the concentration of Au(NPs) in the nanohybrid. The formation of spherical diffusion zone, which was dependent on the concentration of Au(NPs) in nanohybrids, was attributed to result in 3 times the increase in the charge transfer rate ks, 5 times increase in mass transfer, and 5% (9%) increase in Ipa (Ipc) observed in cyclic voltammetry in 80 nM Au(NP) nanohybrid-modified GCE from MWCNT-modified GCE. The work was extended to probe the effect of charge transfer rates at various concentrations of Au(NPs) in the nanohybrid-modified electrodes in the presence of Escherichia coli. The cyclic voltammetry results clearly showed the best results for 80 nM Au(NPs) in nanohybrid electrode. Conclusion The present study suggested that the formation of spherical diffusion zone in nanohybrid-modified electrodes is critical for the enhanced electrochemical biosensing applications. PMID:29713161

Synthesis of octahedral gold tip-blobbed nanoparticles and their dielectric sensing properties.

PubMed

Zhang, Liqiu; Jang, Hee-Jeong; Yoo, Sung Jae; Cho, Sanghyun; Won, Ji Hye; Liu, Lichun; Park, Sungho

2018-06-22

Site-selective synthesis of nanostructures is an important topic in the nanoscience community. Normally, the difference between seeds and deposition atoms in terms of crystallinity triggers the deposition atoms to grow initially at the specific site of nucleation. It is more challenging to control the deposition site of atoms that have the same composition as the seeds because the atoms tend to grow epitaxially, covering the whole surface of the seed nanoparticles. Gold (Au) nano-octahedrons used as seeds in this study possess obvious hierarchical surface energies depending on whether they are at vertices, edges, or terraces. Although vertices of Au nano-octahedrons have the highest surface energy, it remains a challenge to selectively deposit Au atoms at the vertices but not at the edges and faces; this selectivity is required to meet the ever-increasing demands of engineered nanomaterial properties. This work demonstrates an easy and robust method to precisely deposit Au nanoparticles at the vertices of Au nano-octahedrons via wet-chemical seed-mediated growth. The successful synthesis of octahedral Au tip-blobbed nanoparticles (Oh Au TBPs) benefited from the cooperative use of thin silver (Ag) layers at the surface of Au nano-octahedron seeds and iodide ions in the Au growth solution. As-synthesized Au nanostructures gave rise to hybrid optical properties, as evidenced from the UV-VIS-NIR extinction spectra, in which a new extinction peak appeared after Au nanoparticles were formed at the vertices of Au nano-octahedrons. A sensitivity evaluation toward dielectric media of a mixture of dimethyl sulfoxide and water suggested that Au TBPs were more optically sensitive compared to the original Au nano-octahedrons. The method demonstrated in this work is promising in the synthesis of advanced Au nanostructures with hybrid optical properties for versatile applications by engineering the surface energy of vertex-bearing Au nanostructures to trigger site-selective overgrowth of congener Au atoms. © 2018 IOP Publishing Ltd.

Seed-induced growth of flower-like Au-Ni-ZnO metal-semiconductor hybrid nanocrystals for photocatalytic applications.

PubMed

Chen, Yuanzhi; Zeng, Deqian; Cortie, Michael B; Dowd, Annette; Guo, Huizhang; Wang, Junbao; Peng, Dong-Liang

2015-03-25

The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au-Ni-ZnO metal-semiconductor hybrid nanocrystals with a flower-like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room-temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as-prepared Au-Ni-ZnO nanocrystals are strongly photocatalytic and can be separated and re-cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application unit for the administration of contrast gases for pulmonary magnetic resonance imaging: optimization of ventilation distribution for (3) He-MRI.

PubMed

Güldner, M; Becker, St; Wolf, U; Düber, C; Friesenecker, A; Gast, K K; Heil, W; Hoffmann, C; Karpuk, S; Otten, E W; Rivoire, J; Salhi, Z; Scholz, A; Schreiber, L M; Terekhov, M

2015-09-01

MRI of lung airspaces using gases with MR-active nuclei ((3) He, (129) Xe, and (19) F) is an important area of research in pulmonary imaging. The volume-controlled administration of gas mixtures is important for obtaining quantitative information from MR images. State-of-the-art gas administration using plastic bags (PBs) does not allow for a precise determination of both the volume and timing of a (3) He bolus. A novel application unit (AU) was built according to the requirements of the German medical devices law. Integrated spirometers enable the monitoring of the inhaled gas flow. The device is particularly suited for hyperpolarized (HP) gases (e.g., storage and administration with minimal HP losses). The setup was tested in a clinical trial (n = 10 healthy volunteers) according to the German medicinal products law using static and dynamic ventilation HP-(3) He MRI. The required specifications for the AU were successfully realized. Compared to PB-administration, better reproducibility of gas intrapulmonary distribution was observed when using the AU for both static and dynamic ventilation imaging. The new AU meets the special requirements for HP gases, which are storage and administration with minimal losses. Our data suggest that gas AU-administration is superior to manual modes for determining the key parameters of dynamic ventilation measurements. © 2014 Wiley Periodicals, Inc.

Magnetic-plasmonic multilayered nanorods

NASA Astrophysics Data System (ADS)

Thumthan, Orathai

Multilayered nanorods which consist of alternating magnetic layers separated by Au layers combine two distinctive properties, magnetic properties and surface plasmonic resonance (SPR) properties into one nano-entity. Their magnetic properties are tunable by changing the layer thickness, varying from single domain to superparamagnetic state. Superparamagnetic is a key requirement for magnetic nanoparticles for bioapplications. Superparamagnetic nanoparticles exhibit high magnetic moments at low applied magnetic field while retain no magnetic moments when magnetic field is removed preventing them from aggregation due to magnetic attraction. Au layers in the nanorods provide anchorage sites for functional group attachment. Also, Au nanodisks exhibit SPR properties. The SPR peak can be tuned from 540 nm to 820 nm by controlling the thickness of magnetic segments while keeping Au thickness constant. In this research, there are three types of multilayered nanorod have been fabricated: Au/NiFe nanorods, Au/Fe nanorods, and Au/Co nanorods. These magnetic nanorods were fabricated by templated electrodeposition into the channels in Anodic Aluminum Oxide (AAO) membrane. The setup for AAO fabrication was developed as a part of this research. Our fabricated AAO membrane has channels with a diameter ranging from 40nm to 80 nm and a thickness of 10um to 12um. Magnetic properties of nanorods such as saturation field, saturation moment, coercivity and remanence are able to manipulate through their shape anisotropy. The magnetization will be easier in long axis rather than short axis of particle. In addition, Au nanodisks in the nanorod structure are not only serving as anchorage sites for functional groups but also provide SPR properties. Under irradiation of light Au nanodisks strongly absorb light at SPR frequency which ranging from 540 nm to 820 nm by controlling the thickness of magnetic segments while keeping Au thickness constant. The SPR tunability of nanorods in near-infrared region can be used in in-vivo biomedical applications such as photo thermal therapy because tissue has an absorption maximum in the infrared range. The magnetic nanorods were explored for the following two applications: 1) as active component orientation-tunable ferrogel for cell culture matrix, 2) as MRI contrast agent. The results show that Au/NiFe magnetic nanorods can be aligned along applied magnetic field. Using MTT assay for 3T3 fibroblast cells, the biocompatibility of Au/Co nanorods was investigated. It shows that cell proliferation after 72 hours of incubation with nanorods decreases as the concentration of nanorods increases. However, cell viability quantified by counting dead cell/live cell reveals that only few cells died after three days of incubation. Au/Co multilayered nanorods were tested as T2 MRI-contrast agent, and a very large relaxivity was observed. In summary, we have successfully fabricated multilayered nanorods with tunability in both magnetic and SPR properties. These nanorods can potentially be used in biological and biomedical fields.

Morphological control of gold nanorods via thermally driven bi-surfactant growth and application for detection of heavy metal ions.

PubMed

Huang, Hao; Li, Huiyi; Wang, Huaiyu; Li, Jia; Li, Penghui; Chen, Qidan; Chen, Yue; Chu, Paul K; Li, Bo; Yu, Xuefeng

2018-05-22

We report a modified synthesis route of colloidal gold nanorods (AuNRs) by combining the thermal re-shaping treatment and bi-surfactant modification using hexadecyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL). Aspect ratios down to 1.3 ± 0.1 can be achieved in addition to good monodispersity, uniformity, and chemical stability of the materials. Furthermore, without needing post-treatment, metal ions directly interact with the AuNRs efficiently, allowing rapid and sensitive colorimetric detection of heavy metal ions such as Pb²⁺ and Cu²⁺ with a low concentration down to 2.5 μM. The detection performance in terms of selectivity, sensitivity and stability is systematically evaluated. The AuNRs with tunable aspect ratios as well as chemical stability have potential in surface-plasmon-based applications such as biochemical sensing, biochemical imaging, medical diagnostics, and cancer therapy. © 2018 IOP Publishing Ltd.

Au-modified three-dimensional In2O3 inverse opals: synthesis and improved performance for acetone sensing toward diagnosis of diabetes

NASA Astrophysics Data System (ADS)

Xing, Ruiqing; Li, Qingling; Xia, Lei; Song, Jian; Xu, Lin; Zhang, Jiahuan; Xie, Yi; Song, Hongwei

2015-07-01

Analyzing the volatile organic compounds (VOCs) in exhaled breath effectively is crucial to medical treatment, which can provide a fast and noninvasive way to diagnose disease. Well-designed materials with controlled structures have great influence on the sensing performance. In this work, the ordered three dimensional inverse opal (3DIO) macroporous In2O3 films with additional via-hole architectures were fabricated and different amounts of gold nanoparticles (Au NPs) were loaded on the In2O3 films aiming at enhancing their electrical responses. The gas sensing to acetone toward diabetes diagnosis in exhaled breath was performed with different Au/In2O3 electrodes. Representatively, the best 3DIO Au/In2O3 sensor can detect acetone effectively at 340 °C with response of 42.4 to 5 ppm, the actual detection limit is as low as 20 ppb, and it holds a dynamic response of 11 s and a good selectivity. Moreover, clinical tests proved that the as-prepared 3DIO Au/In2O3 IO sensor could distinguish acetone biomarkers in human breath clearly. The excellent gas sensing properties of the Au/In2O3 electrodes were attributed to the ``spillover effects'' between Au and In2O3 and the special 3DIO structure. This work indicates that 3DIO Au/In2O3 composite is a promising electrode material for actual application in the monitoring and detection of diabetes through exhaled breath.Analyzing the volatile organic compounds (VOCs) in exhaled breath effectively is crucial to medical treatment, which can provide a fast and noninvasive way to diagnose disease. Well-designed materials with controlled structures have great influence on the sensing performance. In this work, the ordered three dimensional inverse opal (3DIO) macroporous In2O3 films with additional via-hole architectures were fabricated and different amounts of gold nanoparticles (Au NPs) were loaded on the In2O3 films aiming at enhancing their electrical responses. The gas sensing to acetone toward diabetes diagnosis in exhaled breath was performed with different Au/In2O3 electrodes. Representatively, the best 3DIO Au/In2O3 sensor can detect acetone effectively at 340 °C with response of 42.4 to 5 ppm, the actual detection limit is as low as 20 ppb, and it holds a dynamic response of 11 s and a good selectivity. Moreover, clinical tests proved that the as-prepared 3DIO Au/In2O3 IO sensor could distinguish acetone biomarkers in human breath clearly. The excellent gas sensing properties of the Au/In2O3 electrodes were attributed to the ``spillover effects'' between Au and In2O3 and the special 3DIO structure. This work indicates that 3DIO Au/In2O3 composite is a promising electrode material for actual application in the monitoring and detection of diabetes through exhaled breath. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02709h

Self-Assembled Upconversion Nanoparticle Clusters for NIR-controlled Drug Release and Synergistic Therapy after Conjugation with Gold Nanoparticles.

PubMed

Cai, Huijuan; Shen, Tingting; Kirillov, Alexander M; Zhang, Yu; Shan, Changfu; Li, Xiang; Liu, Weisheng; Tang, Yu

2017-05-01

Fabricated three-dimensional (3D) upconversion nanoclusters (abbreviated as EBSUCNPs) are obtained via an emulsion-based bottom-up self-assembly of NaGdF 4 :Yb/Er@NaGdF 4 nanoparticles (abbreviated as UCNPs), which comprise a NaGdF 4 :Yb/Er core and a NaGdF 4 shell. The EBSUCNPs were then coated with a thin mesoporous amino-functionalized SiO 2 shell (resulting in EBSUCNPs@SiO 2 precursor) and further conjugated with gold nanoparticles to give the novel EBSUCNPs@SiO 2 @Au material. Finally, EBSUCNPs@SiO 2 @Au was applied as a biocompatible and efficient drug carrier for doxorubicin (DOX), thus giving rise to a multifunctional EBSUCNPs@SiO 2 -DOX@Au nanocomposite. This final material, EBSUCNPs@SiO 2 -DOX@Au, and the precursor nanoparticles, EBSUCNPs@SiO 2 @Au, were both fully characterized and their luminescence was investigated in detail. In addition, the drug release properties and photothermal effects of EBSUCNPs@SiO 2 -DOX@Au were also discussed. Interestingly, when under NIR irradiation, an increasing DOX release was achieved owing to the thermal effect of the Au NPs after absorbing the green light from the upconversion nanoclusters based on the fluorescence resonance energy transfer (FRET) effect. Thus, a near-infrared (NIR)-controlled "on-off" pattern of drug release behavior can be achieved. Moreover, compared with a single therapy method, the assembled nanocomposites exhibit a good synergistic therapy against cancer cells that combines chemotherapy with photothermal therapy. In addition, the in vitro fluorescence microscopy images of EBSUCNPs@SiO 2 -DOX@Au show a higher enhancement in the red region due to the loading of DOX molecules with respect to EBSUCNPs@SiO 2 @Au. Therefore, this novel multifunctional 3D cluster architecture can be used in the biomedical field after modification and may pave a new way in other application areas of UCNPs clusters.

Accumulation and interparticle connections of triangular Ag-coated Au nanoprisms by oil-coating method for surface-enhanced Raman scattering applications

NASA Astrophysics Data System (ADS)

Noda, Yuta; Asaka, Toru; Fudouzi, Hiroshi; Hayakawa, Tomokatsu

2018-03-01

To examine the optical responses of surface-enhanced Raman scattering (SERS) for tuned plasmonic nanoparticles, triangular Ag-coated Au (Au@Ag) nanoprisms with different sizes were separately synthesized, which were well controlled in their size (edge-length) and localized surface plasmon resonance (LSPR) wavelength (69.0 ± 8.4 to 173.8 ± 25.6 nm in size and 662-943 nm in LSPR wavelength). The mechanism of Ag shell formation on the Au nanoprisms was also studied with scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS). The Au@Ag nanoprisms were immobilized by covering a colloidal solution containing the nanoprisms with silicone oil and evaporating the solvent in the oil (oil-coating method) so as to form a layer of accumulated plasmonic Au@Ag nanoprisms that had LSPR peak wavelengths tuned from 839 to 1182 nm. The accumulation conditions were analyzed by field-emission scanning electron microscopy (FE-SEM) and a Raman mapping technique. The Au@Ag nanoprisms under excitation at 632.8 nm exhibited higher SERS signals of rhodamine 6G, and SERS-mapped images of the novel immobilized films were obtained at different magnifications. It was concluded that accumulated Au@Ag nanoprisms undergoing tip-planar interconnections could produce enhanced local fields, resulting in higher SERS signals.

Production of Au clusters by plasma gas condensation and their incorporation in oxide matrixes by sputtering

NASA Astrophysics Data System (ADS)

Figueiredo, N. M.; Serra, R.; Manninen, N. K.; Cavaleiro, A.

2018-05-01

Gold clusters were produced by plasma gas condensation method and studied in great detail for the first time. The influence of argon flow, discharge power applied to the Au target and aggregation chamber length on the size distribution and deposition rate of Au clusters was evaluated. Au clusters with sizes between 5 and 65 nm were deposited with varying deposition rates and size dispersion curves. Nanocomposite Au-TiO2 and Au-Al2O3 coatings were then deposited by alternating sputtering. These coatings were hydrophobic and showed strong colorations due to the surface plasmon resonance effect. By simulating the optical properties of the nanocomposites it was possible to identify each individual contribution to the overall surface plasmon resonance signal. These coatings show great potential to be used as high performance localized surface plasmon resonance sensors or as robust self-cleaning decorative protective layers. The hybrid method used for depositing the nanocomposites offers several advantages over co-sputtering or thermal evaporation processes, since a broader range of particle sizes can be obtained (up to tens of nanometers) without the application of any thermal annealing treatments and the properties of clusters and matrix can be controlled separately.

Laser generated gold nanocorals with broadband plasmon absorption for photothermal applications

NASA Astrophysics Data System (ADS)

Poletti, Annamaria; Fracasso, Giulio; Conti, Giamaica; Pilot, Roberto; Amendola, Vincenzo

2015-08-01

Gold nanoparticles with efficient plasmon absorption in the visible and near infrared (NIR) regions, biocompatibility and easy surface functionalization are of interest for photothermal applications. Herein we describe the synthesis and photothermal properties of gold ``nanocorals'' (AuNC) obtained by laser irradiation of Au nanospheres (AuNS) dispersed in liquid solution. AuNC are formed in two stages: by photofragmentation of AuNS, followed by spontaneous unidirectional assembly of gold nanocrystals. The whole procedure is performed without chemicals or templating compounds, hence the AuNC can be coated with thiolated molecules in one step. We show that AuNC coated with thiolated polymers are easily dispersed in an aqueous environment or in organic solvents and can be included in polymeric matrixes to yield a plasmonic nanocomposite. AuNC dispersions exhibit flat broadband plasmon absorption ranging from the visible to the NIR and unitary light-to-heat conversion. Besides, in vitro biocompatibility experiments assessed the absence of cytotoxic effects even at a dose as high as 100 μg mL-1. These safe-by-designed AuNC are promising for use in various applications such as photothermal cancer therapy, light-triggered drug release, antimicrobial substrates, optical tomography, obscurant materials and optical coatings.

Substrate-Based Noble-Metal Nanomaterials: Shape Engineering and Applications

NASA Astrophysics Data System (ADS)

Hajfathalian, Maryam

Nanostructures have potential for use in state-of-the-art applications such as sensing, imaging, therapeutics, drug delivery, and electronics. The ability to fabricate and engineer these nanoscale materials is essential for the continued development of such devices. Because the morphological features of nanomaterials play a key role in determining chemical and physical properties, there is great interest in developing and improving methods capable of controlling their size, shape, and composition. While noble nanoparticles have opened the door to promising applications in fields such as imaging, cancer targeting, photothermal treatment, drug delivery, catalysis and sensing, the synthetic processes required to form these nanoparticles on surfaces are not well-developed. Herein is a detailed account on efforts for adapting established solution-based seed-mediated synthetic protocols to structure in a substrate-based platform. These syntheses start by (i) defining heteroepitaxially oriented nanostructured seeds at site-specific locations using lithographic or directed-assembly techniques, and then (ii) transforming the seeds using either a solution or vapor phase processing route to activate kinetically- or thermodynamically-driven growth modes, to arrive at nanocrystals with complex and useful geometries. The first series of investigations highlight synthesis-routes based on heterogeneous nucleation, where templates serve as nucleation sites for metal atoms arriving in the vapor phase. In the first research direction, the vapor-phase heterogeneous nucleation of Ag on Au was carried out at high temperatures, where the Ag vapor was sourced from a sublimating foil onto adjacent Au templates. This process transformed both the composition and morphology of the initial Au Wulff-shaped nanocrystals to a homogeneous AuAg nanoprism. In the second case, the vapor-phase heterogeneous nucleation of Cu atoms on Au nanocrystal templates was investigated by placing a Cu foil next to Au templates and heating, which caused the Cu atoms from the foil to sublimate from the foil and heterogeneously nucleation on the surface of the immobilized Au seeds. This process caused the composition and morphology of the Au Wulff-shape to transform into a homogeneous AuCu nanotriangle. Lastly, we characterized the morphological features and composition, optical properties, and also the catalytic and photocatalytic performance toward hydrogenation of 4-nitrophenolate. The second series of investigations highlight synthetic routes utilizing competencies of substrate-based techniques with colloidal chemistry. We have demonstrated two substrate-based syntheses yielding bimetallic nanostructures where shape control was achieved through (i) facet-selective capping agents and (ii) additive and subtractive process. In the first case a citrate-based cubic structure has been synthesized in the presence or absence of ascorbic acid and the role of each has been considered in shape control. Reactions were carried out in which Ag+ ions were reduced onto substrate-immobilized Ag, Au, Pd, and Pt seeds. It was discovered that for syntheses lacking ascorbic acid, citrate acts as both the capping and the reducing agent, resulting in a robust nanocube growth mode; however, when ascorbic acid was included in these syntheses, then the growth mode reverted to one that advances the octahedral geometry. The conclusion of these results was that citrate, or one of its oxidation products, selectively caps (100) facets, but where this capability was compromised by ascorbic acid. In the second case, galvanic replacement reactions have been carried out on immobilized cubic and Wulff structures to create the substrate-based nanoshells and nanocages, where the prepositioned templates were chemically transformed into hollow structures. In this novel research, Wulff-shaped templates of Au, Pt, or Pd, formed through the dewetting of ultrathin films, were first transformed into core?shell structures through the reduction of Ag+ ions onto their surface and then further transformed through the galvanic replacement of Ag with Au. Detailed studies were provided highlighting discoveries related to (i) alloying, (ii) dealloying, (iii) hollowing, (iv) crystal structure and (vi) the localized surface plasmon resonance (LSPR). Overall, a series of synthetic strategies based on physical and chemical vapor deposition were devised and validated to achieve novel substrate- based nanomaterials with different shapes and compositions for a variety of applications such as sensing, plasmonics, catalysis, and photocatalysis. The novel research in this dissertation also takes advantage of competencies of substrate-based techniques with colloidal chemistry and, brings this rich and exciting chemistry and its associated functionalities to the substrate surface.

Development of Pt-Au-Graphene-Carbon Nanotube Composite for Fuel Cells and Biosensors Applications

DTIC Science & Technology

2011-02-11

1 Project Title:- Development of Pt-Au- Graphene -Carbon nanotube composites for fuel cells and biosensors applications Objectives:- This...project addresses the architectures needed for the processing of Pt-Au- graphene -carbon nanotube (Pt-Au/f-G/f-CNT) nanocomposites and aims at the...cells:- Graphene and nitrogen doped graphene as catalyst support materials:- Graphene and nitrogen doped graphene have been used as a catalyst

Triggering the volume phase transition of core-shell Au nanorod-microgel nanocomposites with light

NASA Astrophysics Data System (ADS)

Rodríguez-Fernández, Jessica; Fedoruk, Michael; Hrelescu, Calin; Lutich, Andrey A.; Feldmann, Jochen

2011-06-01

We have coated gold nanorods (NRs) with thermoresponsive microgel shells based on poly(N-isopropylacrylamide) (pNIPAM). We demonstrate by simultaneous laser-heating and optical extinction measurements that the Au NR cores can be simultaneously used as fast optothermal manipulators (switchers) and sensitive optical reporters of the microgel state in a fully externally controlled and reversible manner. We support our results with optical modeling based on the boundary element method and 3D numerical analysis on the temperature distribution. Briefly, we show that due to the sharp increase in refractive index resulting from the optothermally triggered microgel collapse, the longitudinal plasmon band of the coated Au NRs is significantly red-shifted. The optothermal control over the pNIPAM shell, and thereby over the optical response of the nanocomposite, is fully reversible and can be simply controlled by switching on and off a NIR heating laser. In contrast to bulk solution heating, we demonstrate that light-triggering does not compromise colloidal stability, which is of primary importance for the ultimate utilization of these types of nanocomposites as remotely controlled optomechanical actuators, for applications spanning from drug delivery to photonic crystals and nanoscale motion.

Conductive Au nanowires regulated by silk fibroin nanofibers

NASA Astrophysics Data System (ADS)

Dong, Bo-Ju; Lu, Qiang

2014-03-01

Conductive Au-biopolymer composites have promising applications in tissue engineering such as nerve tissue regeneration. In this study, silk fibroin nanofibers were formed in aqueous solution by regulating silk self-assembly process and then used as template for Au nanowire fabrication. We performed the synthesis of Au seeds by repeating the seeding cycles for several times in order to increase the density of Au seeds on the nanofibers. After electroless plating, densely decorated Au seeds grew into irregularly shaped particles following silk nanofiber to fill the gaps between particles and finally form uniform continuous nanowires. The conductive property of the Au-silk fibroin nanowires was studied with current-voltage ( I-V) measurement. A typical ohmic behavior was observed, which highlighted their potential applications in nerve tissue regeneration.

Synthesis and Plasmonic Understanding of Core/Satellite and Core Shell Nanostructures

NASA Astrophysics Data System (ADS)

Ruan, Qifeng

Localized surface plasmon resonance, which stems from the collective oscillations of conduction-band electrons, endows Au nanocrystals with unique optical properties. Au nanocrystals possess extremely large scattering/absorption cross-sections and enhanced local electromagnetic field, both of which are synthetically tunable. Moreover, when Au nanocrystals are closely placed or hybridized with semiconductors, the coupling and interaction between the individual components bring about more fascinating phenomena and promising applications, including plasmon-enhanced spectroscopies, solar energy harvesting, and cancer therapy. The continuous development in the field of plasmonics calls for further advancements in the preparation of high-quality plasmonic nanocrystals, the facile construction of hybrid plasmonic nanostructures with desired functionalities, as well as deeper understanding and efficient utilization of the interaction between plasmonic nanocrystals and semiconductor components. In this thesis, I developed a seed-mediated growth method for producing size-controlled Au nanospheres with high monodispersity and assembled Au nanospheres of different sizes into core/satellite nanostructures for enhancing Raman signals. For investigating the interactions between Au nanocrystals and semiconductors, I first prepared (Au core) (TiO2 shell) nanostructures, and then studied their synthetically controlled plasmonic properties and light-harvesting applications. Au nanocrystals with spherical shapes are desirable in plasmon-coupled systems owing to their high geometrical symmetry, which facilitates the analysis of electrodynamic responses in a classical electromagnetic framework and the investigation of quantum tunneling and nonlocal effects. I prepared remarkably uniform Au nanospheres with diameters ranging from 20 nm to 220 nm using a simple seed-mediated growth method associated with mild oxidation. Core/satellite nanostructures were assembled out of differently sized Au nanospheres with molecular linkers. The plasmon resonances of the core/satellite nanostructures undergo red shifts in comparison to those of the sole Au cores, which is consistent with Mie theory analysis. As predicted by finite-difference time-domain simulations, the assembled core/satellite nanostructures exhibit large enhancements for Raman scattering. The facile growth of Au nanospheres and assembly of core/satellite nanostructures blaze a new way to the design of nanoarchitectures with desired plasmonic properties and functions. Coating semiconductors onto Au nanocrystals to form core shell configurations can increase the interactions between the two materials, benefiting from their large active interfacial area. The shell can also protect the Au nanocrystal core from aggregation, reshaping, and chemical corrosion. In this thesis, (Au nanocrystal core) (titania shell) nanostructures with tunable shell thicknesses were prepared by a facile wetchemistry method. Au nanocrystals with strong and tunable plasmon resonances in the visible and near-infrared regions can enhance and broaden the light utilization of TiO2 through the scattering/absorption enhancement, sensitization, and hot-electron injection. The integration of Au nanocrystals therefore hold the prospect of breaking the light-harvesting limit of TiO2 arising from its wide band gap. The resultant (Au core) (TiO2 shell) nanostructures were examined to be capable of efficiently generating reactive oxygen species under near-infrared resonant excitation. On the other hand, the transverse plasmon modes of Au nanorods, which are often too weak to be observed on scattering spectra, are enhanced by the TiO2 shell through energy transfer. With the increment of the shell thickness, the intensity of the transverse plasmon mode increases significantly and even becomes comparable with the longitudinal plasmon mode. Interestingly, both the transverse and longitudinal modes of the (Au core) (TiO2 shell) nanostructures exhibit asymmetric Fano line shapes. The Fano resonances result from the coupling between the core and shell, as understood by the mechanical oscillator model. Besides varying the shell thickness, the plasmonic bands of the core shell nanostructures can also be tailored by employing Au nanorods with different aspect ratios. The synthetically tunable plasmonic properties and synergistic interactions between the gold core and the titania shell make the hybrid nanostructure a multifunctional nanomaterial and ideal system for studying the plasmonic hybrid nanostructures.

Noble metal based plasmonic nanomaterials and their application for bio-imaging and photothermal therapy

NASA Astrophysics Data System (ADS)

Zhu, Dewei

During the past two decades, researchers have gained more and more insight into the manipulation of nanomaterials to create useful technologies. Numerous classes of nanomaterials have been produced and studied based upon their intriguing chemical and physical properties and their potential applications in diverse fields, ranging from electronics to renewable energy and biomedicine. In this dissertation, we describe the synthesis and potential biomedical applications of several types of noble metal-based nanomaterials in which we control size, shape, and coupling to other materials to tune their localized surface plasmon resonance (LSPR) interaction with light. We demonstrate the application of these novel nanostructures as contrast agents for photoacoustic imaging and as photosensitizers for photothermal therapy. Chapter one first presents protocols for producing monodisperse spherical nanoparticles of gold and silver. The diameter of the nanospheres can be adjusted from less than 2 nm to greater than 10 nm by controlling the reaction conditions, including ligands that cap the nanosphere surfaces, reaction time, and reaction temperature. Next, we describe the synthesis of multi-branched Au nanocrystals with predominantly tripodal, tetrapodal and star-shaped morphologies. We demonstrate tuning of the LSPR energy in these materials by changing the branch length. In the third part of this chapter, we present a novel method for coupling heavily-doped p-type copper selenide (Cu2-xSe) NPs with Au NPs by seeded nanocrystal growth to form a new type of semiconductor-metal heterogeneous nanostructure. This new class of plasmonic nanomaterials can simultaneously exhibit two types of LSPR in a single system, producing a broad optical absorbance that is nearly flat across the near infrared (NIR) spectral region (750-1150nm), along with a small shoulder at 566 nm that originates from the Au NP. We conclude this first chapter by demonstrating the use of self-doped copper sulfide (Cu 2-xS) NCs as a template for preparing gold sulfide (Au2S) NCs and intermediate Cu2-xS-Au2S heterostructures by cation exchange. In chapter two, we demonstrate the use of Au-Cu2-xSe nano-dimers for high contrast multimodal imaging in vitro and in vivo. Their broad LSPR absorbance and scattering enables both dark-field optical imaging and photoacoustic (PA) imaging with different light sources. The clinical relevance of these new PA contrast agents was demonstrated through deep tissue visualization of a sentinel lymph node (SLN) in a rat. Imaging through layers of chicken breast tissue at total imaging depths needed for human SLN imaging was achieved. Further, the kinetics of these NCs in the rat circulatory system were monitored in vivo. A widely available and relatively low cost Nd:YAG laser source(1064 nm) was used for all PA imaging experiments, which is an additional benefit for easy commercialization and clinical translation. Thus, these unique Au-Cu2-xSe heterodimer NPs provide a promising optical contrast agent for deep tissue imaging by PAT, as well as a new material system for fundamental studies of plasmonic interactions. In chapter three, we study the potential of both Au-Cu 2-xSe NCs and multi-branched Au NCs for use in photothermal therapy (PTT). Upon illumination with a 980 nm laser beam, the Au-Cu2-xSe nanocrystals produce significant photothermal heating, exhibiting a photothermal transduction efficiency of 32%, which is comparable to that of Au nanorods and nanoparticles (10nm). The multi-branched Au NCs exhibited a photothermal transduction efficiency of 60%, significantly higher than other materials tested in this study. In vitro photothermal heating of either Au-Cu2-xSe nanocrystals or multi-branched Au nanocrystals in the presence of human cervical cancer cells caused effective cell ablation after 10 min laser irradiation at 1.34 W/cm2. Cell viability assays demonstrate that the two classes of nanocrystals are biocompatible at doses needed for photothermal therapy. Although the photothermal transduction efficiency of the multibranched Au NCs was higher than the other materials, they proved somewhat less effective for photothermal ablation of cells. We attribute this to decreased uptake of these relatively large nanostructures compared to the smaller Au-Cu2-xSe NCs. The calibration and analysis above suggest that the Au-Cu2-xSe NCs and the multi-branched Au NCs can serve as promising new photothermal therapy agents.

A remote-controlled generation of gold@polydopamine (core@shell) nanoparticles via physical-chemical stimuli of polydopamine/gold composites

NASA Astrophysics Data System (ADS)

Lee, Yi Seul; Bae, Ji Young; Koo, Hye Young; Lee, Young Boo; Choi, Won San

2016-03-01

We present the synthesis of polydopamine particle-gold composites (PdopP-Au) and unique release of Au@Pdop core@shell nanoparticles (NPs) from the PdopP-Au upon external stimuli. The PdopP-Au was prepared by controlled synthesis of AuNPs on the Pdop particles. Upon near infrared (NIR) irradiation or NaBH4 treatment on the PdopP-Au, the synthesized AuNPs within the PdopPs could be burst-released as a form of Au@Pdop NPs. The PdopP-Au composite showed outstanding photothermal conversion ability under NIR irradiation due to the ultrahigh loading of the AuNPs within the PdopPs, leading to a remote-controlled explosion of the PdopP-Au and rapid formation of numerous Au@Pdop NPs. The release of the Au@Pdop NPs could be instantly stopped or re-started by off or reboot of NIR, respectively. The structure of the released Au@Pdop NPs is suitable for a catalyst or adsorbent, thus we demonstrated that the PdopP-Au composite exhibited excellent and sustained performances for environmental remediation due to its capability of the continuous production of fresh catalysts or adsorbents during the reuse.

Peptide-coated gold nanoparticles for modulation of angiogenesis in vivo.

PubMed

Roma-Rodrigues, Catarina; Heuer-Jungemann, Amelie; Fernandes, Alexandra R; Kanaras, Antonios G; Baptista, Pedro V

2016-01-01

In this work, peptides designed to selectively interact with cellular receptors involved in the regulation of angiogenesis were anchored to oligo-ethylene glycol-capped gold nanoparticles (AuNPs) and used to evaluate the modulation of vascular development using an ex ovo chick chorioallantoic membrane assay. These nanoparticles alter the balance between naturally secreted pro- and antiangiogenic factors, under various biological conditions, without causing toxicity. Exposure of chorioallantoic membranes to AuNP-peptide activators of angiogenesis accelerated the formation of new arterioles when compared to scrambled peptide-coated nanoparticles. On the other hand, antiangiogenic AuNP-peptide conjugates were able to selectively inhibit angiogenesis in vivo. We demonstrated that AuNP vectorization is crucial for enhancing the effect of active peptides. Our data showed for the first time the effective control of activation or inhibition of blood vessel formation in chick embryo via AuNP-based formulations suitable for the selective modulation of angiogenesis, which is of paramount importance in applications where promotion of vascular growth is desirable (eg, wound healing) or ought to be contravened, as in cancer development.

Avoiding Thiol Compound Interference: A Nanoplatform Based on High-Fidelity Au-Se Bonds for Biological Applications.

PubMed

Hu, Bo; Kong, Fanpeng; Gao, Xiaonan; Jiang, Lulu; Li, Xiaofeng; Gao, Wen; Xu, Kehua; Tang, Bo

2018-05-04

Gold nanoparticles (Au NPs) assembled through Au-S covalent bonds have been widely used in biomolecule-sensing technologies. However, during the process, detection distortions caused by high levels of thiol compounds can still significantly influence the result and this problem has not really been solved. Based on the higher stability of Au-Se bonds compared to Au-S bonds, we prepared selenol-modified Au NPs as an Au-Se nanoplatform (NPF). Compared with the Au-S NPF, the Au-Se NPF exhibits excellent anti-interference properties in the presence of millimolar levels of glutathione (GSH). Such an Au-Se NPF that can effectively avoid detection distortions caused by high levels of thiols thus offers a new perspective in future nanomaterial design, as well as a novel platform with higher stability and selectivity for the in vivo application of chemical sensing and clinical therapies. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly monodisperse multiple twinned AuCu-Pt trimetallic nanoparticles with high index surfaces.

PubMed

Khanal, Subarna; Bhattarai, Nabraj; McMaster, David; Bahena, Daniel; Velazquez-Salazar, J Jesus; Jose-Yacaman, Miguel

2014-08-14

Trimetallic nanoparticles possess different properties than their mono- and bi-metallic counterparts, opening a wide range of possibilities for diverse potential applications with the notion to study possible morphology, atomic ordering, reduce precious metal consumption and many others. In this paper, we present a comprehensive experimental study on AuCu-Pt trimetallic nanoparticles with an average diameter of 15 ± 1.0 nm, synthesized in a one-pot synthesis method and characterized by the Cs-corrected scanning transmission electron microscopy technique that allowed us to probe the structure at the atomic level resolution. A new way to control the nanoparticle morphology by the presence of third metal (Pt) is also discussed by the overgrowth of Pt on the as prepared AuCu core by Frank-van der Merwe (FM) layer-by-layer and Stranski-Krastanov (SK) island-on-wetting-layer growth modes. With the application of this research, we are now a step closer to produce optimum catalysts in which the active phase forms only surface monolayers. In addition, the nanoalloy exhibits high index facet surfaces with {211} and {321} families that are highly open-structure surfaces and are interesting for the catalytic applications.

Highly Monodisperse Multiple Twinned AuCu/Pt Trimetallic Nanoparticles with High Index Surfaces

PubMed Central

Khanal, Subarna; Bhattarai, Nabraj; McMaster, David; Bahena, Daniel; Velazquez-Salazar, J. Jesus

2014-01-01

Trimetallic nanoparticles present different properties than their mono- and bi-metallic counterparts, opening a wide range of possibilities for diverse potential applications with the notion to study possible morphology, atomic ordering, reduce precious metal consumption and many others. In this paper, we are presenting a comprehensive experimental study on AuCu/Pt trimetallic nanoparticles with an average diameter 15 ± 1.0 nm, synthesized in one-pot synthesis method and characterized by Cs-corrected scanning transmission electron microscopy technique that allowed us to probe the structure at the atomic level resolution. A new way to control the nanoparticle morphology by the presence of third metal (Pt) is also discussed by the overgrowth of Pt on as prepared AuCu core by Frank–van der Merwe (FM) layer-by-layer and Stranski–Krastanov (SK) island-on-wetting-layer growth modes. With the application of this research, we are now a step closer to produce optimum catalysts in which the active phase forms only surface monolayers. In addition, the nanoalloy presents high index facet surfaces with {211} and {321} families, that are highly open-structure surfaces and are interesting for the catalytic applications. PMID:24975090

Pancreatic response to gold nanoparticles includes decrease of oxidative stress and inflammation in autistic diabetic model.

PubMed

Selim, Manar E; Abd-Elhakim, Yasmina M; Al-Ayadhi, Laila Y

2015-01-01

Gold nanoparticles (AuNPs) have a wide range of applications in various fields. This study provides an understanding of the modulatory effects of AuNPs on an antioxidant system in male Wistar diabetic rats with autism spectrum disorder (ASD). Normal littermates fed by control mothers were injected with citrate buffer alone and served as normal, untreated controls controlin this study. Diabetes mellitus (DM) was induced by administering a single intraperitoneal injection of streptozotocin (STZ) (100 mg/kg) to the pups of (ND) diabetic group, which had been fasted overnight. Autistic pups from mothers that had received a single intraperitoneal injection of 600 mg/kg sodium valproate on day 12.5 after conception were randomly divided into 2 groups (n 2 7/group) as follow; administering single intraperitoneal injection of streptozotocin (STZ) ( (100 mg/kg) to the overnight fasted autistic pups of (AD) autistic diabetic group. The treatment was started on the 5th day after STZ injection with the same dose as in group II and it was considered as 1st day of treatment with gold nanoparticles for 7 days to each rat of (group IV) treated autistic diabetic group(TAD) at a dosage of 2.5 mg/kg. b. wt. At this dose of administration AuNPs, the activities of hepatic superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase were greater in group TAD compared with the control group (P < 0.05). Oxidised glutathione levels were lower (P > 0.05) in the liver of autistic diabetic AuNPs -supplemented rats, whereas reduced glutathione was markedly higher than in control rats, especially after administration of AuNPs. Moreover, the kidney functions in addition to the fat profile scoring supported the protective potential of that dose of AuNPs. The beta cells revealed euchromatic nuclei with no evidence of separation of nuclear membrane. Our results showed that AuNPs improved many of the oxidative stress parameters (SOD, GPx and, CAT), plasma antioxidant capacity (ORAC) and lipid profile relative to the other parameters. In addition to the apparent reversibility of the pancreatic B cell in group IV which may reflect the regenerative capacity of AuNPs. © 2015 S. Karger AG, Basel.

PEGylated dendrimer-entrapped gold nanoparticles for in vivo blood pool and tumor imaging by computed tomography.

PubMed

Peng, Chen; Zheng, Linfeng; Chen, Qian; Shen, Mingwu; Guo, Rui; Wang, Han; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-02-01

We report the synthesis and characterization of dendrimer-entrapped gold nanoparticles (Au DENPs) modified by polyethylene glycol (PEG) with enhanced biocompatibility for computed tomography (CT) imaging applications. In this study, amine-terminated poly(amidoamine) dendrimers of generation 5 (G5.NH(2)) modified by PEG monomethyl ether (G5.NH(2)-mPEG(20)) were used as templates to synthesize Au DENPs, followed by acetylation of the remaining dendrimer terminal amines to generate PEGylated Au DENPs. The partial PEGylation modification of dendrimer terminal amines allows high loading of Au within the dendrimer interior, and consequently by simply varying the Au salt/dendrimer molar ratio, the size of the PEGylated Au DENPs can be controlled at a range of 2-4 nm with a narrow size distribution. The formed PEGylated Au DENPs are water-dispersible, stable in a pH range of 5-8 and a temperature range of 0-50 °C, and non-cytotoxic at a concentration as high as 100 μm. X-ray absorption coefficient measurements show that the attenuation intensity of the PEGylated Au DENPs is much higher than that of Omnipaque with iodine concentration similar to Au. With the sufficiently long half-decay time demonstrated by pharmacokinetics studies, the PEGylated Au DENPs enabled not only X-ray CT blood pool imaging of mice and rats after intravenous injection of the particles, but also effective CT imaging of a xenograft tumor model in nude mice. These findings suggest that the designed PEGylated Au DENPs can be used as a promising contrast agent with enhanced biocompatibility for CT imaging of various biological systems, especially in cancer diagnosis. Copyright © 2011 Elsevier Ltd. All rights reserved.

Dithiothreitol-Regulated Coverage of Oligonucleotide-Modified Gold Nanoparticles To Achieve Optimized Biosensor Performance.

PubMed

Liang, Pingping; Canoura, Juan; Yu, Haixiang; Alkhamis, Obtin; Xiao, Yi

2018-01-31

DNA-modified gold nanoparticles (AuNPs) are useful signal-reporters for detecting diverse molecules through various hybridization- and enzyme-based assays. However, their performance is heavily dependent on the probe DNA surface coverage, which can influence both target binding and enzymatic processing of the bound probes. Current methods used to adjust the surface coverage of DNA-modified AuNPs require the production of multiple batches of AuNPs under different conditions, which is costly and laborious. We here develop a single-step assay utilizing dithiothreitol (DTT) to fine-tune the surface coverage of DNA-modified AuNPs. DTT is superior to the commonly used surface diluent, mercaptohexanol, as it is less volatile, allowing for the rapid and reproducible controlling of surface coverage on AuNPs with only micromolar concentrations of DTT. Upon adsorption, DTT forms a dense monolayer on gold surfaces, which provides antifouling capabilities. Furthermore, surface-bound DTT adopts a cyclic conformation, which reorients DNA probes into an upright position and provides ample space to promote DNA hybridization, aptamer assembly, and nuclease digestion. We demonstrate the effects of surface coverage on AuNP-based sensors using DTT-regulated DNA-modified AuNPs. We then use these AuNPs to visually detect DNA and cocaine in colorimetric assays based on enzyme-mediated AuNP aggregation. We determine that DTT-regulated AuNPs with lower surface coverage achieve shorter reaction times and lower detection limits relative to those for assays using untreated AuNPs or DTT-regulated AuNPs with high surface coverage. Additionally, we demonstrate that our DTT-regulated AuNPs can perform cocaine detection in 50% urine without any significant matrix effects. We believe that DTT regulation of surface coverage can be broadly employed for optimizing DNA-modified AuNP performance for use in biosensors as well as drug delivery and therapeutic applications.

Enhanced electrocatalytic activity of graphene-gold nanoparticles hybrids for peroxynitrite electrochemical detection on hemin-based electrode.

PubMed

Wang, Beibei; Ji, Xueping; Ren, Jujie; Ni, Ruixing; Wang, Lin

2017-12-01

A simple, ultrasensitive peroxynitrite anion (ONOO - ) electrochemical sensing platform was developed by immobilizing hemin on a density controllable electrochemically reduced graphene oxide-Au nanoparticles (ERGO-AuNPs) nanohybrids. The ERGO-AuNPs in situ nanohybrids were produced onto a glass carbon electrode (GCE) by one-step electrodeposition, the density of which could be easily controlled by electrodeposited time. The morphology of ERGO-AuNPs nanohybrids was characterized by a scanning electron microscope (SEM). The ERGO-AuNPs nanohybrids showed a high electrocatalytic activity for immobilized-hemin, because the nanostructures hybrids could effectively promote electron transfer rate between hemin and the electrode. Due to nanohybrids-enhanced catalytic effect for hemin, they were firstly selected for use as a highly sensitive electrochemical platform for ONOO - detection. The resulted sensor showed a high electrocatalytic activity toward ONOO - oxidation, being free from the electroactive interferents, including nitrite, nitrate, dopamine and uric acid at an applied potential of 0.7V. The sensor exhibited a high sensitivity of 123.1nAμM -1 and a lower detection limit of 0.1μM, and a wide linear range of 2.4×10 -6 to 5.5×10 -5 M, which could be attributed to the synergy between ERGO and AuNPs in hybrids. The nanohybrids in situ preparation and ONOO - detection methods would be beneficial to developing other sensing interface and have promising applications in biological molecules analysis and clinical diagnostic. Copyright © 2017 Elsevier B.V. All rights reserved.

Alternating-pulse iontophoresis for targeted cutaneous anesthesia

NASA Technical Reports Server (NTRS)

Meyer, Peter F.; Oddsson, Lars I E.

2003-01-01

In studies of sensory contributions to motor control, it may be advantageous to temporarily reduce the sensitivity of specific sensory systems. This article details a method for non-invasively inducing cutaneous anesthesia, leaving proprioceptive and motor functions intact. This method, called alternating-pulse iontophoresis, differs from conventional direct-current (DC) iontophoretic drug delivery in that adjacent drug delivery electrodes are stimulated out-of-phase. The total current delivered at any instant is then less than that produced during a comparable DC application, while the uniformity of drug delivery is expected to improve. Effective delivery of local anesthetics to the cutaneous foot soles by alternating-pulse iontophoresis was demonstrated using cutaneous pressure sensory threshold levels (STL's) assessed with Semmes-Weinstein monofilaments (arbitrary units of perceived force, or a.u.). Thirteen of 16 healthy subjects achieved a level of anesthesia greater than or equal to that normally associated with clinical peripheral sensory neuropathy. Average STL's measured prior to the anesthesia procedure were 4.00 a.u. ( approximately 10 mN). Immediately following the procedure, STL's were elevated to an average of 5.40 a.u. ( approximately 246 mN) and averaged 4.97 a.u. ( approximately 92 mN) after 50 min of standing. A number of research and clinical applications for this technique are suggested.

The characteristics and mechanisms of Au nanoparticles processed by functional centrifugal procedures

NASA Astrophysics Data System (ADS)

Shiau, Bo-Wen; Lin, Chien-Hung; Liao, Ying-Yen; Lee, Ya-Rong; Liu, Shih-Hao; Ding, Wei-Cheng; Lee, Jia-Ren

2018-05-01

In this work, the optical properties of Au nanoparticles processed by centrifugation techniques are studied. Most of the literature related to the control of nanoparticle size has focused on different preparation parameters; however, the wide size distribution is commonly an issue for follow-up investigations and further applications. Therefore, we developed a method in which specific-diameter particles can be effectively separated using different centrifugal procedures. The initial nanoparticle solution with a primary absorption peak at 534 nm is separated into discernible resonance wavelengths from 526 to 537 nm, with corresponding particle sizes from 30 to 55 nm. For the atomic force microscopy analysis of nanoparticle size, a dry cetyltrimethylammonium bromide (CTAB) film often covers the particles and interferes with the measurement; thus, CTAB has to be removed. However, if too much CTAB is removed, the surface of the Au nanoparticle becomes unstable, and the particles aggregate. Accordingly, we used UV spectroscopy to monitor the CTAB content; properly adjust the rotational speed and the number of centrifugation stages; and design a method that can effectively remove impurities, avoid clustering, and enable particle size measurement. The usually complicated procedures and high cost of preparation of specific-size Au nanoparticles are greatly simplified and reduced by the convenient extraction process proposed in this work, which would benefit related research and applications.

Au-modified three-dimensional In₂O₃ inverse opals: synthesis and improved performance for acetone sensing toward diagnosis of diabetes.

PubMed

Xing, Ruiqing; Li, Qingling; Xia, Lei; Song, Jian; Xu, Lin; Zhang, Jiahuan; Xie, Yi; Song, Hongwei

2015-08-14

Analyzing the volatile organic compounds (VOCs) in exhaled breath effectively is crucial to medical treatment, which can provide a fast and noninvasive way to diagnose disease. Well-designed materials with controlled structures have great influence on the sensing performance. In this work, the ordered three dimensional inverse opal (3DIO) macroporous In2O3 films with additional via-hole architectures were fabricated and different amounts of gold nanoparticles (Au NPs) were loaded on the In2O3 films aiming at enhancing their electrical responses. The gas sensing to acetone toward diabetes diagnosis in exhaled breath was performed with different Au/In2O3 electrodes. Representatively, the best 3DIO Au/In2O3 sensor can detect acetone effectively at 340 °C with response of 42.4 to 5 ppm, the actual detection limit is as low as 20 ppb, and it holds a dynamic response of 11 s and a good selectivity. Moreover, clinical tests proved that the as-prepared 3DIO Au/In2O3 IO sensor could distinguish acetone biomarkers in human breath clearly. The excellent gas sensing properties of the Au/In2O3 electrodes were attributed to the "spillover effects" between Au and In2O3 and the special 3DIO structure. This work indicates that 3DIO Au/In2O3 composite is a promising electrode material for actual application in the monitoring and detection of diabetes through exhaled breath.

Tuning optical properties of magic number cluster (SiO2)4O2H4 by substitutional bonding with gold atoms.

PubMed

Cai, Xiulong; Zhang, Peng; Ma, Liuxue; Zhang, Wenxian; Ning, Xijing; Zhao, Li; Zhuang, Jun

2009-04-30

By bonding gold atoms to the magic number cluster (SiO(2))(4)O(2)H(4), two groups of Au-adsorbed shell-like clusters Au(n)(SiO(2))(4)O(2)H(4-n) (n = 1-4) and Au(n)(SiO(2))(4)O(2) (n = 5-8) were obtained, and their spectral properties were studied. The ground-state structures of these clusters were optimized by density functional theory, and the results show that in despite of the different numbers and types of the adsorbed Au atoms, the cluster core (SiO(2))(4)O(2) of T(d) point-group symmetry keeps almost unchanged. The absorption spectra were obtained by time-dependent density functional theory. From one group to the other, an extension of absorption wavelength from the UV-visible to the NIR region was observed, and in each group the absorption strengths vary linearly with the number of Au atoms. These features indicate their advantages for exploring novel materials with easily controlled tunable optical properties. Furthermore, due to the weak electronic charge transfer between the Au atoms, the clusters containing Au(2) dimers, especially Au(8)(SiO(2))(4)O(2), absorb strongly NIR light at 900 approximately 1200 nm. Such strong absorption suggests potential applications of these shell-like clusters in tumor cells thermal therapy, like the gold-coated silica nanoshells with larger sizes.

Facile synthesis of reduced graphene oxide-gold nanohybrid for potential use in industrial waste-water treatment

NASA Astrophysics Data System (ADS)

Kar, Prasenjit; Sardar, Samim; Liu, Bo; Sreemany, Monjoy; Lemmens, Peter; Ghosh, Srabanti; Pal, Samir Kumar

2016-01-01

Here, we report a facile approach, by the photochemical reduction technique, for in situ synthesis of Au-reduced graphene oxide (Au-RGO) nanohybrids, which demonstrate excellent adsorption capacities and recyclability for a broad range of dyes. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) data confirm the successful synthesis of Au-RGO nanohybrids. The effect of several experimental parameters (temperature and pH) variation can effectively control the dye adsorption capability. Furthermore, kinetic adsorption data reveal that the adsorption process follows a pseudo second-order model. The negative value of Gibbs free energy (ΔG0) confirms spontaneity while the positive enthalpy (ΔH0) indicates the endothermic nature of the adsorption process. Picosecond resolved fluorescence technique unravels the excited state dynamical processes of dye molecules adsorbed on the Au-RGO surface. Time resolved fluorescence quenching of Rh123 after adsorption on Au-RGO nanohybrids indicates efficient energy transfer from Rh123 to Au nanoparticles. A prototype device has been fabricated using Au-RGO nanohybrids on a syringe filter (pore size: 0.220 μm) and the experimental data indicate efficient removal of dyes from waste water with high recyclability. The application of this nanohybrid may lead to the development of an efficient reusable adsorbent in portable water purification.

Toehold-mediated internal control to probe the near-field interaction between the metallic nanoparticle and the fluorophore

NASA Astrophysics Data System (ADS)

Ang, Y. S.; Yung, L. Y. L.

2014-10-01

Metallic nanoparticles (MNPs) are known to alter the emission of vicinal fluorophores through the near-field interaction, leading to either fluorescence quenching or enhancement. Much ambiguity remains in the experimental outcome of such a near-field interaction, particularly for bulk colloidal solution. It is hypothesized that the strong far-field interference from the inner filter effect of the MNPs could mask the true near-field MNP-fluorophore interaction significantly. Thus, in this work, a reliable internal control capable of decoupling the near-field interaction from far-field interference is established by the use of the DNA toehold concept to mediate the in situ assembly and disassembly of the MNP-fluorophore conjugate. A model gold nanoparticle (AuNP)-Cy3 system is used to investigate our proposed toehold-mediated internal control system. The maximum fluorescence enhancement is obtained for large-sized AuNP (58 nm) separated from Cy3 at an intermediate distance of 6.8 nm, while fluorescence quenching is observed for smaller-sized AuNP (11 nm and 23 nm), which is in agreement with the theoretical values reported in the literature. This work shows that the toehold-mediated internal control design can serve as a central system for evaluating the near-field interaction of other MNP-fluorophore combinations and facilitate the rational design of specific MNP-fluorophore systems for various applications.Metallic nanoparticles (MNPs) are known to alter the emission of vicinal fluorophores through the near-field interaction, leading to either fluorescence quenching or enhancement. Much ambiguity remains in the experimental outcome of such a near-field interaction, particularly for bulk colloidal solution. It is hypothesized that the strong far-field interference from the inner filter effect of the MNPs could mask the true near-field MNP-fluorophore interaction significantly. Thus, in this work, a reliable internal control capable of decoupling the near-field interaction from far-field interference is established by the use of the DNA toehold concept to mediate the in situ assembly and disassembly of the MNP-fluorophore conjugate. A model gold nanoparticle (AuNP)-Cy3 system is used to investigate our proposed toehold-mediated internal control system. The maximum fluorescence enhancement is obtained for large-sized AuNP (58 nm) separated from Cy3 at an intermediate distance of 6.8 nm, while fluorescence quenching is observed for smaller-sized AuNP (11 nm and 23 nm), which is in agreement with the theoretical values reported in the literature. This work shows that the toehold-mediated internal control design can serve as a central system for evaluating the near-field interaction of other MNP-fluorophore combinations and facilitate the rational design of specific MNP-fluorophore systems for various applications. Electronic supplementary information (ESI) available: DNA sequences, size distribution analysis, photobleaching background and optical characterization. See DOI: 10.1039/c4nr03643c

Systematic Control of Self-Assembled Au Nanoparticles and Nanostructures Through the Variation of Deposition Amount, Annealing Duration, and Temperature on Si (111).

PubMed

Li, Ming-Yu; Sui, Mao; Pandey, Puran; Zhang, Quanzhen; Kim, Eun-Soo; Lee, Jihoon

2015-12-01

The size, density, and configurations of Au nanoparticles (NPs) can play important roles in controlling the electron mobility, light absorption, and localized surface plasmon resonance, and further in the Au NP-assisted nanostructure fabrications. In this study, we present a systematical investigation on the evolution of Au NPs and nanostructures on Si (111) by controlling the deposition amount (DA), annealing temperature (AT), and dwelling time (DT). Under an identical growth condition, the morphologies of Au NPs and nanostructures drastically evolve when the DA is only slightly varied, based on the Volmer-Weber and coalescence models: i.e. I: mini NPs, II: mid-sized round dome-shaped Au NPs, III: large Au NPs, and IV: coalesced nanostructures. With the AT control, three distinctive ranges are observed: i.e., NP nucleation, Au NPs maturation and melting. The gradual dimensional expansion of Au NPs is always compensated with the density reduction, which is explained with the thermodynamic theory. The DT effect is relatively minor on Au NPs, a sharp contrast to other metallic NPs, which is discussed based on the Ostwald-ripening.

Internal-Modified Dithiol DNA–Directed Au Nanoassemblies: Geometrically Controlled Self–Assembly and Quantitative Surface–Enhanced Raman Scattering Properties

PubMed Central

Yan, Yuan; Shan, Hangyong; Li, Min; Chen, Shu; Liu, Jianyu; Cheng, Yanfang; Ye, Cui; Yang, Zhilin; Lai, Xuandi; Hu, Jianqiang

2015-01-01

In this work, a hierarchical DNA–directed self–assembly strategy to construct structure–controlled Au nanoassemblies (NAs) has been demonstrated by conjugating Au nanoparticles (NPs) with internal–modified dithiol single-strand DNA (ssDNA) (Au–B–A or A–B–Au–B–A). It is found that the dithiol–ssDNA–modified Au NPs and molecule quantity of thiol–modified ssDNA grafted to Au NPs play critical roles in the assembly of geometrically controlled Au NAs. Through matching Au–DNA self–assembly units, geometrical structures of the Au NAs can be tailored from one–dimensional (1D) to quasi–2D and 2D. Au–B–A conjugates readily give 1D and quasi–2D Au NAs while 2D Au NAs can be formed by A–B–Au–B–A building blocks. Surface-enhanced Raman scattering (SERS) measurements and 3D finite–difference time domain (3D-FDTD) calculation results indicate that the geometrically controllable Au NAs have regular and linearly “hot spots”–number–depended SERS properties. For a certain number of NPs, the number of “hot spots” and accordingly enhancement factor of Au NAs can be quantitatively evaluated, which open a new avenue for quantitative analysis based on SERS technique. PMID:26581251

Knowledge Based System Applications for Guidance and Control (Application des Systemes a Base de Connaissances au Guidage-Pilotage)

DTIC Science & Technology

1991-01-01

techniques and integration concepts. Recent advances in digital computation techniques including data base management , represent the core enabling...tactical information management and effective pilot interaction are essential. Pilot decision aiding, combat automation, sensor fusion and ol-board...tactical battle management concepts offer the opportunity for substantial mission effectiveness improvements. Although real-time tactical military

Nanoscale Polysulfides Reactors Achieved by Chemical Au-S Interaction: Improving the Performance of Li-S Batteries on the Electrode Level.

PubMed

Fan, Chao-Ying; Xiao, Pin; Li, Huan-Huan; Wang, Hai-Feng; Zhang, Lin-Lin; Sun, Hai-Zhu; Wu, Xing-Long; Xie, Hai-Ming; Zhang, Jing-Ping

2015-12-23

In this work, the chemical interaction of cathode and lithium polysulfides (LiPSs), which is a more targeted approach for completely preventing the shuttle of LiPSs in lithium-sulfur (Li-S) batteries, has been established on the electrode level. Through simply posttreating the ordinary sulfur cathode in atmospheric environment just for several minutes, the Au nanoparticles (Au NPs) were well-decorated on/in the surface and pores of the electrode composed of commercial acetylene black (CB) and sulfur powder. The Au NPs can covalently stabilize the sulfur/LiPSs, which is advantageous for restricting the shuttle effect. Moreover, the LiPSs reservoirs of Au NPs with high conductivity can significantly control the deposition of the trapped LiPSs, contributing to the uniform distribution of sulfur species upon charging/discharging. The slight modification of the cathode with <3 wt % Au NPs has favorably prospered the cycle capacity and stability of Li-S batteries. Moreover, this cathode exhibited an excellent anti-self-discharge ability. The slight decoration for the ordinary electrode, which can be easily accessed in the industrial process, provides a facile strategy for improving the performance of commercial carbon-based Li-S batteries toward practical application.

Design of Janus nanoparticles with atomic precision: tungsten-doped gold nanostructures.

PubMed

Sun, Qiang; Wang, Qian; Jena, Puru; Kawazoe, Yoshiyuki

2008-02-01

Janus nanoparticles, characterized by their anisotropic structure and interactions, have added a new dimension to nanoscience because of their potential applications in biomedicine, sensors, catalysis, and assembled materials. The technological applications of these nanoparticles, however, have been limited as the current chemical, physical, and biosynthetic methods lack sufficient size and shape selectivity. We report a technique where gold clusters doped with tungsten can serve as a seed that facilitates the natural growth of anisotropic nanostructures whose size and shape can be controlled with atomic precision. Using ab initio simulated annealing and molecular dynamics calculations on AunW (n > 12) clusters, we discovered that the W@Au12 cage cluster forms a very stable core with the remaining Au atoms forming patchy structures on its surface. The anisotropic geometry gives rise to anisotropies in vibrational spectra, charge distributions, electronic structures, and reactivity, thus making it useful to have dual functionalities. In particular, the core-patch structure is shown to possess a hydrophilic head and a hydrophobic tail. The W@Au12 clusters can also be used as building blocks of a nanoring with novel properties.

CO2 storage resources, reserves, and reserve growth: Toward a methodology for integrated assessment of the storage capacity of oil and gas reservoirs and saline formations

USGS Publications Warehouse

Burruss, Robert

2009-01-01

Geologically based methodologies to assess the possible volumes of subsurface CO2 storage must apply clear and uniform definitions of resource and reserve concepts to each assessment unit (AU). Application of the current state of knowledge of geologic, hydrologic, geochemical, and geophysical parameters (contingencies) that control storage volume and injectivity allows definition of the contingent resource (CR) of storage. The parameters known with the greatest certainty are based on observations on known traps (KTs) within the AU that produced oil, gas, and water. The aggregate volume of KTs within an AU defines the most conservation volume of contingent resource. Application of the concept of reserve growth to CR volume provides a logical path for subsequent reevaluation of the total resource as knowledge of CO2 storage processes increases during implementation of storage projects. Increased knowledge of storage performance over time will probably allow the volume of the contingent resource of storage to grow over time, although negative growth is possible.

CO2 storage resources, reserves, and reserve growth: Toward a methodology for integrated assessment of the storage capacity of oil and gas reservoirs and saline formations

USGS Publications Warehouse

Burruss, R.C.

2009-01-01

Geologically based methodologies to assess the possible volumes of subsurface CO2 storage must apply clear and uniform definitions of resource and reserve concepts to each assessment unit (AU). Application of the current state of knowledge of geologic, hydrologic, geochemical, and geophysical parameters (contingencies) that control storage volume and injectivity allows definition of the contingent resource (CR) of storage. The parameters known with the greatest certainty are based on observations on known traps (KTs) within the AU that produced oil, gas, and water. The aggregate volume of KTs within an AU defines the most conservation volume of contingent resource. Application of the concept of reserve growth to CR volume provides a logical path for subsequent reevaluation of the total resource as knowledge of CO2 storage processes increases during implementation of storage projects. Increased knowledge of storage performance over time will probably allow the volume of the contingent resource of storage to grow over time, although negative growth is possible. ?? 2009 Elsevier Ltd. All rights reserved.

Effect of spherical Au nanoparticles on nanofriction and wear reduction in dry and liquid environments

PubMed Central

Maharaj, Dave

2012-01-01

Summary Nano-object additives are used in tribological applications as well as in various applications in liquids requiring controlled manipulation and targeting. On the macroscale, nanoparticles in solids and liquids have been shown to reduce friction and wear. On the nanoscale, atomic force microscopy (AFM) studies have been performed in single- and multiple-nanoparticle contact, in dry environments, to characterize friction forces and wear. However, limited studies in submerged liquid environments have been performed and further studies are needed. In this paper, spherical Au nanoparticles were studied for their effect on friction and wear under dry conditions and submerged in water. In single-nanoparticle contact, individual nanoparticles, deposited on silicon, were manipulated with a sharp tip and the friction force was determined. Multiple-nanoparticle contact sliding experiments were performed on nanoparticle-coated silicon with a glass sphere. Wear tests were performed on the nanoscale with AFM as well as on the macroscale by using a ball-on-flat tribometer to relate friction and wear reduction on the nanoscale and macroscale. Results indicate that the addition of Au nanoparticles reduces friction and wear. PMID:23213639

Thiolated DNA-based chemistry and control in the structure and optical properties of plasmonic nanoparticles with ultrasmall interior nanogap.

PubMed

Oh, Jeong-Wook; Lim, Dong-Kwon; Kim, Gyeong-Hwan; Suh, Yung Doug; Nam, Jwa-Min

2014-10-08

The design, synthesis and control of plasmonic nanostructures, especially with ultrasmall plasmonically coupled nanogap (∼1 nm or smaller), are of significant interest and importance in chemistry, nanoscience, materials science, optics and nanobiotechnology. Here, we studied and established the thiolated DNA-based synthetic principles and methods in forming and controlling Au core-nanogap-Au shell structures [Au-nanobridged nanogap particles (Au-NNPs)] with various interior nanogap and Au shell structures. We found that differences in the binding affinities and modes among four different bases to Au core, DNA sequence, DNA grafting density and chemical reagents alter Au shell growth mechanism and interior nanogap-forming process on thiolated DNA-modified Au core. Importantly, poly A or poly C sequence creates a wider interior nanogap with a smoother Au shell, while poly T sequence results in a narrower interstitial interior gap with rougher Au shell, and on the basis of the electromagnetic field calculation and experimental results, we unraveled the relationships between the width of the interior plasmonic nanogap, Au shell structure, electromagnetic field and surface-enhanced Raman scattering. These principles and findings shown in this paper offer the fundamental basis for the thiolated DNA-based chemistry in forming and controlling metal nanostructures with ∼1 nm plasmonic gap and insight in the optical properties of the plasmonic NNPs, and these plasmonic nanogap structures are useful as strong and controllable optical signal-generating nanoprobes.

Plasmonic Heterodimers with Binding Site-Dependent Hot Spot for Surface-Enhanced Raman Scattering.

PubMed

Tian, Yuanyuan; Shuai, Zhenhua; Shen, Jingjing; Zhang, Lei; Chen, Shufen; Song, Chunyuan; Zhao, Baomin; Fan, Quli; Wang, Lianhui

2018-06-01

A novel plasmonic heterodimer nanostructure with a controllable self-assembled hot spot is fabricated by the conjugation of individual Au@Ag core-shell nanocubes (Au@Ag NCs) and varisized gold nanospheres (GNSs) via the biotin-streptavidin interaction from the ensemble to the single-assembly level. Due to their featured configurations, three types of heterogeneous nanostructures referred to as Vertice, Vicinity, and Middle are proposed and a single hot spot forms between the nanocube and nanosphere, which exhibits distinct diversity in surface plasmon resonance effect. Herein, the calculated surface-enhanced Raman scattering enhancement factors of the three types of heterodimers show a narrow distribution and can be tuned in orders of magnitude by controlling the size of GNSs onto individual Au@Ag NCs. Particularly, the Vertice heterodimer with unique configuration can provide extraordinary enhancement of the electric field for the single hot spot region due to the collaborative interaction of lightning rod effect and interparticle plasmon coupling effect. This established relationship between the architecture and the corresponding optical properties of the heterodimers provides the basis for creating controllable platforms which can be exploited in the applications of plasmonic devices, electronics, and biodetection. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Complete Au@ZnO core-shell nanoparticles with enhanced plasmonic absorption enabling significantly improved photocatalysis

NASA Astrophysics Data System (ADS)

Sun, Yiqiang; Sun, Yugang; Zhang, Tao; Chen, Guozhu; Zhang, Fengshou; Liu, Dilong; Cai, Weiping; Li, Yue; Yang, Xianfeng; Li, Cuncheng

2016-05-01

Nanostructured ZnO exhibits high chemical stability and unique optical properties, representing a promising candidate among photocatalysts in the field of environmental remediation and solar energy conversion. However, ZnO only absorbs the UV light, which accounts for less than 5% of total solar irradiation, significantly limiting its applications. In this article, we report a facile and efficient approach to overcome the poor wettability between ZnO and Au by carefully modulating the surface charge density on Au nanoparticles (NPs), enabling rapid synthesis of Au@ZnO core-shell NPs at room temperature. The resulting Au@ZnO core-shell NPs exhibit a significantly enhanced plasmonic absorption in the visible range due to the Au NP cores. They also show a significantly improved photocatalytic performance in comparison with their single-component counterparts, i.e., the Au NPs and ZnO NPs. Moreover, the high catalytic activity of the as-synthesized Au@ZnO core-shell NPs can be maintained even after many cycles of photocatalytic reaction. Our results shed light on the fact that the Au@ZnO core-shell NPs represent a promising class of candidates for applications in plasmonics, surface-enhanced spectroscopy, light harvest devices, solar energy conversion, and degradation of organic pollutants.Nanostructured ZnO exhibits high chemical stability and unique optical properties, representing a promising candidate among photocatalysts in the field of environmental remediation and solar energy conversion. However, ZnO only absorbs the UV light, which accounts for less than 5% of total solar irradiation, significantly limiting its applications. In this article, we report a facile and efficient approach to overcome the poor wettability between ZnO and Au by carefully modulating the surface charge density on Au nanoparticles (NPs), enabling rapid synthesis of Au@ZnO core-shell NPs at room temperature. The resulting Au@ZnO core-shell NPs exhibit a significantly enhanced plasmonic absorption in the visible range due to the Au NP cores. They also show a significantly improved photocatalytic performance in comparison with their single-component counterparts, i.e., the Au NPs and ZnO NPs. Moreover, the high catalytic activity of the as-synthesized Au@ZnO core-shell NPs can be maintained even after many cycles of photocatalytic reaction. Our results shed light on the fact that the Au@ZnO core-shell NPs represent a promising class of candidates for applications in plasmonics, surface-enhanced spectroscopy, light harvest devices, solar energy conversion, and degradation of organic pollutants. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00933f

Stabilization of AuNPs by monofunctional triazole linked to ferrocene, ferricenium, or coumarin and applications to synthesis, sensing, and catalysis.

PubMed

Li, Na; Zhao, Pengxiang; Igartua, María E; Rapakousiou, Amalia; Salmon, Lionel; Moya, Sergio; Ruiz, Jaime; Astruc, Didier

2014-11-03

Monofunctional triazoles linked to ferrocene, ferricenium, or coumarin (Cou), easily synthesized by copper-catalyzed azide alkyne (CuAAC) "click" reactions between the corresponding functional azides and (trimethylsilyl)acetylene followed by silyl group deprotection, provide a variety of convenient neutral ligands for the stabilization of functional gold nanoparticles (AuNPs) in polar organic solvents. These triazole (trz)-AuNPs are very useful toward a variety of applications to synthesis, sensing, and catalysis. Both ferrocenyl (Fc) and isostructural ferricenium linked triazoles give rise to AuNP stabilization, although by different synthetic routes. Indeed, the first direct synthesis and stabilization of AuNPs by ferricenium are obtained by the reduction of HAuCl4 upon reaction with a ferrocene derivative, AuNP stabilization resulting from a synergy between electrostatic and coordination effects. The ferricenium/ferrocene trz-AuNP redox couple is fully reversible, as shown by cyclic voltammograms that were recorded with both redox forms. These trz-AuNPs are stable for weeks in various polar solvents, but at the same time, the advantage of trz-AuNPs is the easy substitution of neutral trz ligands by thiols and other ligands, giving rise to applications. Indeed, this ligand substitution of trz at the AuNP surface yields a stable Fc-terminated nanogold-cored dendrimer upon reaction with a Fc-terminated thiol dendron, substitution of Cou-linked trz with cysteine, homocysteine, and glutathione provides remarkably efficient biothiol sensing, and a ferricenium-linked trz-AuNP catalyst is effective for NaBH4 reduction of 4-nitrophenol to 4-aminophenol. In this catalytic example, the additional electrostatic AuNP stabilization modulates the reaction rate and induction time.

Ion irradiation synthesis of Ag-Au bimetallic nanospheroids in SiO2 glass substrate with tunable surface plasmon resonance frequency

NASA Astrophysics Data System (ADS)

Meng, Xuan; Shibayama, Tamaki; Yu, Ruixuan; Takayanagi, Shinya; Watanabe, Seiichi

2013-08-01

Ag-Au bimetallic nanospheroids with tunable localized surface plasmon resonance (LSPR) were synthesized by 100 keV Ar-ion irradiation of 30 nm Ag-Au bimetallic films deposited on SiO2 glass substrates. A shift of the LSPR peaks toward shorter wavelengths was observed up to an irradiation fluence of 1.0 × 1017 cm-2, and then shifted toward the longer wavelength because of the increase of fragment volume under ion irradiation. Further control of LSPR frequency over a wider range was realized by modifying the chemical components. The resulting LSPR frequencies lie between that of the pure components, and an approximate linear shift of the LSPR toward the longer wavelength with the Au concentration was achieved, which is in good agreement with the theoretical calculations based on Gans theory. In addition, the surface morphology and compositions were examined with a scanning electron microscope equipped with an energy dispersive spectrometer, and microstructural characterizations were performed using a transmission electron microscope. The formation of isolated photosensitive Ag-Au nanospheroids with a FCC structure partially embedded in the SiO2 substrate was confirmed, which has a potential application in solid-state devices.

Synthesis of Au microwires by selective oxidation of Au–W thin-film composition spreads

PubMed Central

Hamann, Sven; Brunken, Hayo; Salomon, Steffen; Meyer, Robert; Savan, Alan; Ludwig, Alfred

2013-01-01

We report on the stress-induced growth of Au microwires out of a surrounding Au–W matrix by selective oxidation, in view of a possible application as ‘micro-Velcro’. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au–W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au48W52 composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au48W52 composition are suitable for micro-Velcro applications. PMID:27877561

Seed mediated synthesis of highly mono-dispersed gold nanoparticles in the presence of hydroquinone

NASA Astrophysics Data System (ADS)

Kumar, Dhiraj; Mutreja, Isha; Sykes, Peter

2016-09-01

Gold nanoparticles (AuNPs) are being studied for several biomedical applications, including drug delivery, biomedical imaging, contrast agents and tumor targeting. The synthesis of nanoparticles with a narrow size distribution is critical for these applications. We report the synthesis of highly mono-dispersed AuNPs by a seed mediated approach, in the presence of tri-sodium citrate and hydroquinone (HQ). AuNPs with an average size of 18 nm were used for the synthesis of highly mono-dispersed nanocrystals of an average size 40 nm, 60 nm, 80 nm and ˜100 nm; but the protocol is not limited to these sizes. The colloidal gold was subjected to UV-vis absorbance spectroscopy, showing a red shift in lambda max wavelength, peaks at 518.47 nm, 526.37 nm, 535.73 nm, 546.03 nm and 556.50 nm for AuNPs seed (18 nm), 40 nm, 60 nm, 80 nm and ˜100 nm respectively. The analysis was consistent with dynamic light scattering and electron microscopy. Hydrodynamic diameters measured were 17.6 nm, 40.8 nm, 59.8 nm, 74.1 nm, and 91.4 nm (size by dynamic light scattering—volume %); with an average poly dispersity index value of 0.088, suggesting mono-dispersity in the size distribution, which was also confirmed by transmission electron microscopy analysis. The advantage of a seed mediated approach is a multi-step growth of nanoparticle size that enables us to control the number of nanoparticles in the suspension, for size ranging from 24.5 nm to 95.8 nm. In addition, the HQ-based synthesis of colloidal nanocrystals allowed control of the particle size and size distribution by tailoring either the number of seeds, amount of gold precursor or reducing agent (HQ) in the final reaction mixture.

FAST TRACK COMMUNICATION Tuning the spin state of iron phthalocyanine by ligand adsorption

NASA Astrophysics Data System (ADS)

Isvoranu, C.; Wang, B.; Schulte, K.; Ataman, E.; Knudsen, J.; Andersen, J. N.; Bocquet, M. L.; Schnadt, J.

2010-12-01

The future use of single-molecule magnets in applications will require the ability to control and manipulate the spin state and magnetization of the magnets by external means. There are different approaches to this control, one being the modification of the magnets by adsorption of small ligand molecules. In this paper we use iron phthalocyanine supported by an Au(111) surface as a model compound and demonstrate, using x-ray photoelectron spectroscopy and density functional theory, that the spin state of the molecule can be tuned to different values (S ~ 0, \\case {1}{2} , 1) by adsorption of ammonia, pyridine, carbon monoxide or nitric oxide on the iron ion. The interaction also leads to electronic decoupling of the iron phthalocyanine from the Au(111) support.

Highly narrow nanogap-containing Au@Au core-shell SERS nanoparticles: size-dependent Raman enhancement and applications in cancer cell imaging

NASA Astrophysics Data System (ADS)

Hu, Chongya; Shen, Jianlei; Yan, Juan; Zhong, Jian; Qin, Weiwei; Liu, Rui; Aldalbahi, Ali; Zuo, Xiaolei; Song, Shiping; Fan, Chunhai; He, Dannong

2016-01-01

Cellular imaging technologies employing metallic surface-enhanced Raman scattering (SERS) tags have gained much interest toward clinical diagnostics, but they are still suffering from poor controlled distribution of hot spots and reproducibility of SERS signals. Here, we report the fabrication and characterization of high narrow nanogap-containing Au@Au core-shell SERS nanoparticles (GCNPs) for the identification and imaging of proteins overexpressed on the surface of cancer cells. First, plasmonic nanostructures are made of gold nanoparticles (~15 nm) coated with gold shells, between which a highly narrow and uniform nanogap (~1.1 nm) is formed owing to polyA anchored on the Au cores. The well controlled distribution of Raman reporter molecules, such as 4,4'-dipyridyl (44DP) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), are readily encoded in the nanogap and can generate strong, reproducible SERS signals. In addition, we have investigated the size-dependent SERS activity of GCNPs and found that with the same laser wavelength, the Raman enhancement discriminated between particle sizes. The maximum Raman enhancement was achieved at a certain threshold of particle size (~76 nm). High narrow nanogap-containing Au@Au core-shell SERS tags (GCTs) were prepared via the functionalization of hyaluronic acid (HA) on GCNPs, which recognized the CD44 receptor, a tumor-associated surface biomarker. And it was shown that GCTs have a good targeting ability to tumour cells and promising prospects for multiplex biomarker detection.Cellular imaging technologies employing metallic surface-enhanced Raman scattering (SERS) tags have gained much interest toward clinical diagnostics, but they are still suffering from poor controlled distribution of hot spots and reproducibility of SERS signals. Here, we report the fabrication and characterization of high narrow nanogap-containing Au@Au core-shell SERS nanoparticles (GCNPs) for the identification and imaging of proteins overexpressed on the surface of cancer cells. First, plasmonic nanostructures are made of gold nanoparticles (~15 nm) coated with gold shells, between which a highly narrow and uniform nanogap (~1.1 nm) is formed owing to polyA anchored on the Au cores. The well controlled distribution of Raman reporter molecules, such as 4,4'-dipyridyl (44DP) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), are readily encoded in the nanogap and can generate strong, reproducible SERS signals. In addition, we have investigated the size-dependent SERS activity of GCNPs and found that with the same laser wavelength, the Raman enhancement discriminated between particle sizes. The maximum Raman enhancement was achieved at a certain threshold of particle size (~76 nm). High narrow nanogap-containing Au@Au core-shell SERS tags (GCTs) were prepared via the functionalization of hyaluronic acid (HA) on GCNPs, which recognized the CD44 receptor, a tumor-associated surface biomarker. And it was shown that GCTs have a good targeting ability to tumour cells and promising prospects for multiplex biomarker detection. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06919j

UV and visible light photocatalytic activity of Au/TiO2 nanoforests with Anatase/Rutile phase junctions and controlled Au locations.

PubMed

Yu, Yang; Wen, Wei; Qian, Xin-Yue; Liu, Jia-Bin; Wu, Jin-Ming

2017-01-24

To magnify anatase/rutile phase junction effects through appropriate Au decorations, a facile solution-based approach was developed to synthesize Au/TiO 2 nanoforests with controlled Au locations. The nanoforests cons®isted of anatase nanowires surrounded by radially grown rutile branches, on which Au nanoparticles were deposited with preferred locations controlled by simply altering the order of the fabrication step. The Au-decoration increased the photocatalytic activity under the illumination of either UV or visible light, because of the beneficial effects of either electron trapping or localized surface plasmon resonance (LSPR). Gold nanoparticles located preferably at the interface of anatase/rutile led to a further enhanced photocatalytic activity. The appropriate distributions of Au nanoparticles magnify the beneficial effects arising from the anatase/rutile phase junctions when illuminated by UV light. Under the visible light illumination, the LSPR effect followed by the consecutive electron transfer explains the enhanced photocatalysis. This study provides a facile route to control locations of gold nanoparticles in one-dimensional nanostructured arrays of multiple-phases semiconductors for achieving a further increased photocatalytic activity.

Synthesis of a novel glucose capped gold nanoparticle as a better theranostic candidate

PubMed Central

Suvarna, Saritha; Das, Ujjal; KC, Sunil; Mishra, Snehasis; Sudarshan, Mathummal; Saha, Krishna Das; Dey, Sanjit; Chakraborty, Anindita; Narayana, Y.

2017-01-01

Gold nanoparticles are predominantly used in diagnostics, therapeutics and biomedical applications. The present study has been designed to synthesize differently capped gold nanoparticles (AuNps) by a simple, one-step, room temperature procedure and to evaluate the potential of these AuNps for biomedical applications. The AuNps are capped with glucose, 2-deoxy-D-glucose (2DG) and citrate using different reducing agents. This is the first report of synthesis of 2DG-AuNp by the simple room temperature method. The synthesized gold nanoparticles are characterized with UV-Visible Spectroscopy, Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and selected area electron diffraction (SAED), Dynamic light scattering (DLS), and Energy-dispersive X-ray spectroscopy (SEM-EDS). Surface-enhanced Raman scattering (SERS) study of the synthesized AuNps shows increase in Raman signals up to 50 times using 2DG. 3-(4, 5-dimethylthiozol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay has been performed using all the three differently capped AuNps in different cell lines to assess cytotoxcity if any, of the nanoparticles. The study shows that 2DG-AuNps is a better candidate for theranostic application. PMID:28582426

Sharp organic interface of molecular C60 chains and a pentacene derivative SAM on Au(788): A combined STM & DFT study

NASA Astrophysics Data System (ADS)

Wang, Jun; Tang, Jian-Ming; Larson, Amanda M.; Miller, Glen P.; Pohl, Karsten

2013-12-01

Controlling the molecular structure of the donor-acceptor interface is essential to overcoming the efficiency bottleneck in organic photovoltaics. We present a study of self-assembled fullerene (C60) molecular chains on perfectly ordered 6,13-dichloropentacene (DCP) monolayers forming on a vicinal Au(788) surface using scanning tunneling microscopy in conjunction with density functional theory calculations. DCP is a novel pentacene derivative optimized for photovoltaic applications. The molecules form a brick-wall patterned centered rectangular lattice with the long axis parallel to the monatomic steps that separate the 3.9 nm wide Au(111) terraces. The strong interaction between the C60 molecules and the gold substrate is well screened by the DCP monolayer. At submonolayer C60 coverage, the fullerene molecules form long parallel chains, 1.1 nm apart, with a rectangular arrangement instead of the expected close-packed configuration along the upper step edges. The perfectly ordered DCP structure is unaffected by the C60 chain formation. The controlled sharp highly-ordered organic interface has the potential to improve the conversion efficiency in organic photovoltaics.

Gold nanoparticle-assisted all optical localized stimulation and monitoring of Ca2+ signaling in neurons

PubMed Central

Lavoie-Cardinal, Flavie; Salesse, Charleen; Bergeron, Éric; Meunier, Michel; De Koninck, Paul

2016-01-01

Light-assisted manipulation of cells to control membrane activity or intracellular signaling has become a major avenue in life sciences. However, the ability to perform subcellular light stimulation to investigate localized signaling has been limited. Here, we introduce an all optical method for the stimulation and the monitoring of localized Ca2+ signaling in neurons that takes advantage of plasmonic excitation of gold nanoparticles (AuNPs). We show with confocal microscopy that 800 nm laser pulse application onto a neuron decorated with a few AuNPs triggers a transient increase in free Ca2+, measured optically with GCaMP6s. We show that action potentials, measured electrophysiologically, can be induced with this approach. We demonstrate activation of local Ca2+ transients and Ca2+ signaling via CaMKII in dendritic domains, by illuminating a single or few functionalized AuNPs specifically targeting genetically-modified neurons. This NP-Assisted Localized Optical Stimulation (NALOS) provides a new complement to light-dependent methods for controlling neuronal activity and cell signaling. PMID:26857748

Control of average spacing of OMCVD grown gold nanoparticles

NASA Astrophysics Data System (ADS)

Rezaee, Asad

Metallic nanostructures and their applications is a rapidly expanding field. Nobel metals such as silver and gold have historically been used to demonstrate plasmon effects due to their strong resonances, which occur in the visible part of the electromagnetic spectrum. Localized surface plasmon resonance (LSPR) produces an enhanced electromagnetic field at the interface between a gold nanoparticle (Au NP) and the surrounding dielectric. This enhanced field can be used for metal-dielectric interfacesensitive optical interactions that form a powerful basis for optical sensing. In addition to the surrounding material, the LSPR spectral position and width depend on the size, shape, and average spacing between these particles. Au NP LSPR based sensors depict their highest sensitivity with optimized parameters and usually operate by investigating absorption peak: shifts. The absorption peak: of randomly deposited Au NPs on surfaces is mostly broad. As a result, the absorption peak: shifts, upon binding of a material onto Au NPs might not be very clear for further analysis. Therefore, novel methods based on three well-known techniques, self-assembly, ion irradiation, and organo-meta1lic chemical vapour deposition (OMCVD) are introduced to control the average-spacing between Au NPs. In addition to covalently binding and other advantages of OMCVD grown Au NPs, interesting optical features due to their non-spherical shapes are presented. The first step towards the average-spacing control is to uniformly form self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) as resists for OMCVD Au NPs. The formation and optimization of the OTS SAMs are extensively studied. The optimized resist SAMs are ion-irradiated by a focused ion beam (Fill) and ions generated by a Tandem accelerator. The irradiated areas are refilled with 3-mercaptopropyl-trimethoxysilane (MPTS) to provide nucleation sites for the OMCVD Au NP growth. Each step during sample preparation is monitored by using surface characterization methods such as contact angle measurements, ellipsometry, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), Rutherford backscattering spectroscopy (RBS), UV-Visible spectroscopy, and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Keywords: Absorption, Array, Average Spacing, Binary Mixture, Density, Deposition, Dose, Fm, Gold Nanoparticle, Growth, Ion Irradiation, LSPR, Nanolithography, Nearest Neighbour Distance, OMCVD, Optical Response, OTS, Polarization, Refilling, Resist, SAM, Self-assembly, SEM Image Analysis, Sensing, Surface, Thin Film, Transparent Substrate.

Improvement on controllable fabrication of streptavidin-modified three-layer core-shell Fe3O4@SiO2@Au magnetic nanocomposites with low fluorescence background.

PubMed

Jiang, Hongrong; Zeng, Xin; Xi, Zhijiang; Liu, Ming; Li, Chuanyan; Li, Zhiyang; Jin, Lian; Wang, Zhifei; Deng, Yan; He, Nongyue

2013-04-01

In present study, we put forward an approach to prepare three-layer core-shell Fe3O4@SiO2@Au magnetic nanocomposites via the combination of self-assembling, seed-mediated growing and multi-step chemical reduction. The Fe3O4@SiO2@Au magnetic nanocomposites were analyzed and characterized by transmission electron microscope (TEM), scanning electronic microscope (SEM), energy dispersive spectrometer analysis (EDS), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), and ultraviolet and visible spectrophotometer (UV-Vis). TEM and SEM characterizations showed that the FeO4@SiO2@Au nanocomposites were obtained successfully with three-layer structures, especially a layer of thin, smooth and continuous gold shell. The average diameter of Fe3O4@SiO2@Au nanocomposites was about 600 nm and an excellent dispersity was observed for the as-prepared nanoparticles. EDS characterizations demonstrated that the nanocomposites contained three elements of the precursors, Fe, Si, and Au. Furthermore, FT-IR showed that the silica and gold shell were coated successfully. UV-Vis and VSM characterizations showed that the Fe3O4@SiO2@Au nanocomposites exhibited good optical and magnetic property, and the saturation magnetization was 25.76 emu/g. In conclusion, the Fe3O4@SiO2@Au magnetic nanocomposites with three-layer core-shell structures were prepared. Furthermore, Fe3O4@SiO2@Au magnetic nanocomposites were modified with streptavidin (SA) successfully, and it was validated that they performed low fluorescence background, suggesting that they should have good applications especially in bioassay based on fluorescence detection through bonding the biotinylated fluorescent probes.

Bimetallic Pt-Au nanocatalysts electrochemically deposited on boron-doped diamond electrodes for nonenzymatic glucose detection.

PubMed

Nantaphol, Siriwan; Watanabe, Takeshi; Nomura, Naohiro; Siangproh, Weena; Chailapakul, Orawon; Einaga, Yasuaki

2017-12-15

The enormous demand for medical diagnostics has encouraged the fabrication of high- performance sensing platforms for the detection of glucose. Nonenzymatic glucose sensors are coming ever closer to being used in practical applications. Bimetallic catalysts have been shown to be superior to single metal catalysts in that they have greater activity and selectivity. Here, we demonstrate the preparation, characterization, and electrocatalytic characteristics of a new bimetallic Pt/Au nanocatalyst. This nanocatalyst can easily be synthesized by electrodeposition by sequentially depositing Au and Pt on the surface of a boron-doped diamond (BDD) electrode. We characterized the nanocatalyst by scanning electron microscopy (SEM), X-ray diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the electrodeposition process and the molar ratio between the Pt and Au precursors. The electrocatalytic characteristics of a Pt/Au/BDD electrode for the nonenzymatic oxidation of glucose were systematically investigated by cyclic voltammetry. The electrode exhibits higher catalytic activity for glucose oxidation than Pt/BDD and Au/BDD electrodes. The best catalytic activity and stability was obtained with a Pt:Au molar ratio of 50:50. Moreover, the presence of Au can significantly enhance the long-term stability and poisoning tolerance during the electro-oxidation of glucose. Measurements of glucose using the Pt/Au/BDD electrode were linear in the range from 0.01 to 7.5mM, with a detection limit of 0.0077mM glucose. The proposed electrode performs selective electrochemical analysis of glucose in the presence of common interfering species (e.g., acetaminophen, uric and ascorbic acids), avoiding the generation of overlapping signals from such species. Copyright © 2017 Elsevier B.V. All rights reserved.

Chemiluminescence of off-line and on-line gold nanoparticle-catalyzed luminol system in the presence of flavonoid.

PubMed

Wu, Dong; Zhang, Xiaoyue; Liu, Yong; Ma, Yan; Wang, Xiaowu; Wang, Xiaojuan; Xu, Liuxin

2017-06-01

It was found that flavonoids could remarkably inhibit the chemiluminescence (CL) intensity of an off-line gold nanoparticle (AuNP)-catalyzed luminol-H 2 O 2 CL system. By contrast, flavonoids enhanced the CL intensity of an on-line AuNP-catalyzed luminol-H 2 O 2 CL system. In the off-line system, the AuNPs were prepared beforehand, whereas in the on-line system, AuNPs were produced by on-line mixing of luminol prepared in a buffer solution of NaHCO 3  - Na 2 CO 3 and HAuCl 4 with no need for the preliminary preparation of AuNPs. The on-line system had prominent advantages over the off-line system, namely a lowering of the background noise and improvements in the stability of the CL system. The results show that differences in the signal suppression effect of flavonoids on the off-line AuNP-catalyzed CL system are influenced by the combined action of a free radical scavenging effect and occupy-sites function; the latter was proved to be predominant using controlled experiments. Enhancement of the on-line system was ascribed to the presence of flavonoids promoting the on-line formation of AuNPs, which better catalyzed the luminol-H 2 O 2 CL reaction, and the enhancement activity of the six flavonoids increased with the increase in reducibility. This work broadens the scope of practical applications of an AuNP-catalyzed CL system. Copyright © 2016 John Wiley & Sons, Ltd.

Thrust Vector Control of an Overexpanded Supersonic Nozzle Using Pin Insertion and Rotating Airfoils

DTIC Science & Technology

1991-12-01

12 THRUST VECTOR CONTROL OP AN OVEREXPANDED 3UPfRSONIC NOZZLE USING PIN INSERTION AND ROTATINO AIRFOILS THESIS Presented to the Faculty of the School...gather data that would aid in the evaluation of thrust vector control mechanisms for nozzle applications. I would like to thank my thesis advisor, Dr... Control Nozzle. MS Thesis . Air Force Institute of Technology (AU), Wright- Patterson AFB OH, December 1988. 4. Herup, Eric J. Confined Jet Thrust Vector

Binding Structures of Diatomic Molecules to Co-Porphyrins on Au(111) Studied by Scanning Tunneling Microscopy

NASA Astrophysics Data System (ADS)

Lee, Soon-Hyeong; Chang, Yun; Kim, Howon; Jang, Won; Kim, Yong-Hyun; Kahng, Se-Jong; Department Of Physics, Korea University. Collaboration; Graduate School Of Nanoscience; Technology (Wcu), Kaist Collaboration

2013-03-01

Axial bindings of diatomic molecules to metalloporphyrins involve in the dynamic processes of biological functions such as respiration, neurotransmission, and photosynthesis. The binding reactions are also useful in sensor applications and to control molecular spins in metalloporphyrins for spintronic applications. Here, we present the binding structures of diatomic molecules to surface-supported Co-porphyrins studied using scanning tunneling microscopy. Upon gas exposure, three-lobed structures of Co-porphyrins transformed to bright ring shapes on Au(111), whereas H2-porphyrins of dark rings remained intact. The bright rings are explained by the structures of reaction complexes where a diatomic ligand, tilted away from the axis normal to the porphyrin plane, is under precession. Our results are consistent with previous bulk experiments using X-ray diffraction and nuclear magnetic resonance spectroscopy.

Gold nanoparticle-embedded silk protein-ZnO nanorod hybrids for flexible bio-photonic devices

NASA Astrophysics Data System (ADS)

Gogurla, Narendar; Kundu, Subhas C.; Ray, Samit K.

2017-04-01

Silk protein has been used as a biopolymer substrate for flexible photonic devices. Here, we demonstrate ZnO nanorod array hybrid photodetectors on Au nanoparticle-embedded silk protein for flexible optoelectronics. Hybrid samples exhibit optical absorption at the band edge of ZnO as well as plasmonic energy due to Au nanoparticles, making them attractive for selective UV and visible wavelength detection. The device prepared on Au-silk protein shows a much lower dark current and a higher photo to dark-current ratio of ∼105 as compared to the control sample without Au nanoparticles. The hybrid device also exhibits a higher specific detectivity due to higher responsivity arising from the photo-generated hole trapping by Au nanoparticles. Sharp pulses in the transient photocurrent have been observed in devices prepared on glass and Au-silk protein substrates due to the light induced pyroelectric effect of ZnO, enabling the demonstration of self-powered photodetectors at zero bias. Flexible hybrid detectors have been demonstrated on Au-silk/polyethylene terephthalate substrates, exhibiting characteristics similar to those fabricated on rigid glass substrates. A study of the performance of photodetectors with different bending angles indicates very good mechanical stability of silk protein based flexible devices. This novel concept of ZnO nanorod array photodetectors on a natural silk protein platform provides an opportunity to realize integrated flexible and self-powered bio-photonic devices for medical applications in near future.

A flexible and stable surface-enhanced Raman scattering (SERS) substrate based on Au nanoparticles/Graphene oxide/Cicada wing array

NASA Astrophysics Data System (ADS)

Shi, Guochao; Wang, Mingli; Zhu, Yanying; Shen, Lin; Wang, Yuhong; Ma, Wanli; Chen, Yuee; Li, Ruifeng

2018-04-01

In this work, we presented an eco-friendly and low-cost method to fabricate a kind of flexible and stable Au nanoparticles/graphene oxide/cicada wing (AuNPs/GO/CW) substrate. By controlling the ratio of reactants, the optimum SERS substrate with average AuNPs size of 65 nm was obtained. The Raman enhancement factor for rhodamine 6G (R6G) was 1.08 ×106 and the limit of detection (LOD) was as low as 10-8 M. After calibrating the Raman peak intensities of R6G, it could be quantitatively detected. In order to better understand the experimental results, the 3D finite-different time-domain simulation was used to simulate the AuNPs/GO/CW-1 (the diameter of the AuNPs was 65 nm) to further investigate the SERS enhancement effect. More importantly, the AuNPs/GO/CW-1 substrates not only can provide strong enhancement factors but also can be stable and reproducible. This SERS substrates owned a good stability for the SERS intensity which was reduced only by 25% after the aging time of 60 days and the relative standard deviation was lower than 20%, revealing excellent uniformity and reproducibility. Our positive findings can pave a new way to optimize the application of SERS substrate as well as provide more SERS platforms for quantitative detection of organic contaminants vestige, which makes it very promising in the trace detection of biological molecules.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosli, Nur Shafawati binti; Rahman, Azhar Abdul; Aziz, Azlan Abdul

Gold nanoparticles (AuNPs) received a great deal of attention for biomedical applications, especially in diagnostic imaging and therapeutics. Even though AuNPs have potential benefits in biomedical applications, the impact of AuNPs on human and environmental health still remains unclear. The use of AuNPs which is a high-atomic-number materials, provide advantages in terms of radiation dose enhancement. However, before this can become a clinical reality, cytotoxicity of the AuNPs has to be carefully evaluated. Cytotoxicity test is a rapid, standardized test that is very sensitive to determine whether the nanoparticles produced are harmful or benign on cellular components. In this workmore » the size and concentration dependence of AuNPs cytotoxicity in breast cancer cell lines (MCF-7) are tested by using WST-1 assay. The sizes of AuNPs tested were 13 nm, 50 nm, and 70 nm. The cells were seeded in the 96-well plate and were treated with different concentrations of AuNPs by serial dilution for each size of AuNPs. The high concentration of AuNPs exhibit lower cell viability compared to low concentration of AuNPs. We quantified the toxicity of AuNPs in MCF-7 cell lines by determining the IC{sub 50} values in WST-1 assays. The IC{sub 50} values (inhibitory concentrations that effected 50% growth inhibition) of 50 nm AuNPs is lower than 13 nm and 70 nm AuNPs. Mean that, 50nm AuNPs are more toxic to the MCF-7 cells compared to smaller and larger sizes AuNPs. The presented results clearly indicate that the cytotoxicity of AuNPs depend not only on the concentration, but also the size of the nanoparticles.« less

Reshaping, Fragmentation, and Assembly of Gold Nanoparticles Assisted by Pulse Lasers

PubMed Central

2016-01-01

Conspectus The vast majority of the outstanding applications of metal nanoparticles (NPs) developed during the last two decades have arisen from their unique optical properties. Within this context, rational synthesis and assembly of gold NPs have been the main research focus, aiming at the design of nanoplasmonic devices with tailored optical functionalities. The progress made in this field is thus to be ascribed to the understanding of the origin of the interaction between light and such gold nanostructures, the dynamics of which have been thoroughly investigated with significant contributions from short and ultrashort pulse laser technologies. We focus this Account on the potential of pulse lasers to provide new fundamental insights into the electron dynamics involved in the interaction of light with the free conduction electrons of Au NPs, that is, localized surface plasmon resonances (LSPRs). The excitation of LSPRs with a femtosecond pulse laser is followed by thermalization of the Au NP electrons and the subsequent relaxation of the nanocrystal lattice and the surrounding environment, which generally results in surface melting. By contrast, nanosecond irradiation usually induces AuNP fragmentation and uncontrolled melting due to overlapping excitation and relaxation phenomena. These concepts have been exploited toward the preparation of highly monodisperse gold nanospheres via pulse laser irradiation of polyhedral nanocrystal colloids, or in the fabrication of nanostructures with “written-in” optical properties. The applicability of pulsed coherent light has been extended toward the direct synthesis and manipulation of Au NPs. Through ablation of a gold target in a liquid with pulse lasers, spherical Au NPs can be synthesized with no need of stabilizing ligands, which is a great advantage in terms of reducing toxicity, rendering these NPs particularly suitable for medical applications. In addition, femtosecond laser irradiation has been proven a unique tool for the controlled welding of plasmonic gold nanostructures by electromagnetic field enhancement at the hot spots of assembled Au NPs. The combination of such nanostructures with pulse lasers promises significant chemical and biochemical advances, including the structural determination of organic reaction intermediates, the investigation of phase transitions in inorganic nanomaterials at mild reaction conditions, or the efficient photothermal destruction of cancer cells avoiding damage of surrounding tissue. PMID:27035211

Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

PubMed Central

Yang, Gaixiu; Chen, Dong; Lv, Pengmei; Kong, Xiaoying; Sun, Yongming; Wang, Zhongming; Yuan, Zhenhong; Liu, Hui; Yang, Jun

2016-01-01

Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m−3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells. PMID:27734945

Synthesis and spectroscopic characterization of gold nanoparticles via plasma-liquid interaction technique

NASA Astrophysics Data System (ADS)

Khatoon, N.; Yasin, H. M.; Younus, M.; Ahmed, W.; Rehman, N. U.; Zakaullah, M.; Iqbal, M. Zafar

2018-01-01

Fabrication of non-functionalized gold nanoparticles is interesting owing to their potential applications in sensing and biomedicine. We report on the synthesis of surfactant-free gold nanoparticles (AuNPs) by Plasma-Liquid Interaction (PLI) technique, using micro-atmospheric pressure D.C. plasma. The effects of discharge parameters, such as discharge current, precursor concentration and gas flow rates on the structure and morphology of AuNPs have been investigated. Optical Emission Spectroscopy (OES) was employed to estimate the UV radiation intensity and OH radical density. Scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) optical spectroscopy were employed to study the morphology and structure of AuNPs. The normalized intensities of UV radiation and OH radical density found to increase with increase in discharge current. We observed that the particle size can be tuned by controlling any of the following parameters: intensity of the UV radiation, OH radical density, and concentration of the Au precursor. Interestingly, we found that addition of 1% Ar in the feedstock gas results in formation of relatively uniform size distribution of nanoparticles. The surfactant-free AuNPs, due to their bare-surface, exhibit excellent surface-enhanced Raman scattering (SERS) properties. The SERS study of Rhodamine 6G using AuNPs as substrates, shows significant Raman enhancement and fluorescence quenching, which makes our technique a potentially powerful route to detection of trace amounts of dangerous explosives and other materials.

Mangiferin functionalized radioactive gold nanoparticles (MGF-198AuNPs) in prostate tumor therapy: green nanotechnology for production, in vivo tumor retention and evaluation of therapeutic efficacy.

PubMed

Al-Yasiri, A Y; Khoobchandani, M; Cutler, C S; Watkinson, L; Carmack, T; Smith, C J; Kuchuk, M; Loyalka, S K; Lugão, A B; Katti, K V

2017-10-31

We report here an innovative feature of green nanotechnology-focused work showing that mangiferin-a glucose functionalized xanthonoid, found in abundance in mango peels-serves dual roles of chemical reduction and in situ encapsulation, to produce gold nanoparticles with optimum in vivo stability and tumor specific characteristics. The interaction of mangiferin with a Au-198 gold precursor affords MGF- 198 AuNPs as the beta emissions of Au-198 provide unique advantages for tumor therapy while gamma rays are used for the quantitative estimation of gold within the tumors and various organs. The laminin receptor specificity of mangiferin affords specific accumulation of therapeutic payloads of this new therapeutic agent within prostate tumors (PC-3) of human prostate tumor origin induced in mice which overexpress this receptor subtype. Detailed in vivo therapeutic efficacy studies, through the intratumoral delivery of MGF- 198 AuNPs, show the retention of over 80% of the injected dose (ID) in prostate tumors up to 24 h. By three weeks post treatment, tumor volumes of the treated group of animals showed an over 5 fold reduction as compared to the control saline group. New opportunities for green nanotechnology and a new paradigm of using mangiferin as a tumor targeting agent in oncology for the application of MGF- 198 AuNPs in the treatment of cancer are discussed.

Peptide protected gold clusters: chemical synthesis and biomedical applications

NASA Astrophysics Data System (ADS)

Yuan, Qing; Wang, Yaling; Zhao, Lina; Liu, Ru; Gao, Fuping; Gao, Liang; Gao, Xueyun

2016-06-01

Bridging the gap between atoms and nanoparticles, noble metal clusters with atomic precision continue to attract considerable attention due to their important applications in catalysis, energy transformation, biosensing and biomedicine. Greatly different to common chemical synthesis, a one-step biomimetic synthesis of peptide-conjugated metal clusters has been developed to meet the demand of emerging bioapplications. Under mild conditions, multifunctional peptides containing metal capturing, reactive and targeting groups are rationally designed and elaborately synthesized to fabricate atomically precise peptide protected metal clusters. Among them, peptide-protected Au Cs (peptide-Au Cs) possess a great deal of exceptional advantages such as nanometer dimensions, high photostability, good biocompatibility, accurate chemical formula and specific protein targeting capacity. In this review article, we focus on the recent advances in potential theranostic fields by introducing the rising progress of peptide-Au Cs for biological imaging, biological analysis and therapeutic applications. The interactions between Au Cs and biological systems as well as potential mechanisms are also our concerned theme. We expect that the rapidly growing interest in Au Cs-based theranostic applications will attract broader concerns across various disciplines.

Size control of Au NPs supported by pH operation

NASA Astrophysics Data System (ADS)

Ichiji, Masumi; Akiba, Hiroko; Hirasawa, Izumi

2017-07-01

Au NPs are expected to become useful functional particles, as particle gun used for plant gene transfer and also catalysts. We have studied PSD (particle size distribution) control of Au NPs by reduction crystallization. Previous study found out importance of seeds policy and also feeding profile. In this paper, effect of pH in the reduction crystallization was investigated to clarify the possibility of Au NPs PSD control by pH operation and also their growth process. Au NPs of size range 10-600 nm were obtained in single-jet system using ascorbic acid (AsA) as a reducing agent with adjusting pH of AsA. Au NPs are found to grow in the process of nucleation, agglomeration, agglomeration growth and surface growth. Au NPs tend to grow by agglomeration and become larger size in lower pH regions, and to grow only by surface growth and become smaller size in higher pH regions.

Near-infrared light-responsive liposomal contrast agent for photoacoustic imaging and drug release applications.

PubMed

Sivasubramanian, Kathyayini; Mathiyazhakan, Malathi; Wiraja, Christian; Upputuri, Paul Kumar; Xu, Chenjie; Pramanik, Manojit

2017-04-01

Photoacoustic imaging has become an emerging tool for theranostic applications. Not only does it help in

Near-infrared light-responsive liposomal contrast agent for photoacoustic imaging and drug release applications

NASA Astrophysics Data System (ADS)

Sivasubramanian, Kathyayini; Mathiyazhakan, Malathi; Wiraja, Christian; Upputuri, Paul Kumar; Xu, Chenjie; Pramanik, Manojit

2017-04-01

Photoacoustic imaging has become an emerging tool for theranostic applications. Not only does it help in in vivo, noninvasive imaging of biological structures at depths but it can also be used for drug release and therapeutic applications. We explore near-infrared light-sensitive liposomes coated with gold nanostars (AuNSs) for both imaging and drug release applications using a photoacoustic imaging system. Being amphiphilic, the liposomes lipid bilayer and the aqueous core enable encapsulation of both hydrophobic and hydrophilic drugs. The AuNSs on the surface of the liposomes act as photon absorbers due to their intrinsic surface plasmon resonance. Upon excitation by laser light at specific wavelength, AuNSs facilitate rapid release of the contents encapsulated in the liposomes due to local heating and pressure wave formation (photoacoustic wave). Herein, we describe the design and optimization of the AuNSs-coated liposomes and demonstrate the release of both hydrophobic and hydrophilic model drugs (paclitaxel and calcein, respectively) through laser excitation at near-infrared wavelength. The use of AuNSs-coated liposomes as contrast agents for photoacoustic imaging is also explored with tissue phantom experiments. In comparison to blood, the AuNSs-coated liposomes have better contrast (approximately two times) at 2-cm imaging depth.

Programmable Regulation of DNA Conjugation to Gold Nanoparticles via Strand Displacement.

PubMed

Zhang, Cheng; Wu, Ranfeng; Li, Yifan; Zhang, Qiang; Yang, Jing

2017-10-31

Methods for conjugating DNA to gold nanoparticles (AuNPs) have recently attracted considerable attention. The ability to control such conjugation in a programmable way is of great interest. Here, we have developed a logic-based method for manipulating the conjugation of thiolated DNA species to AuNPs via cascading DNA strand displacement. Using this method, several logic-based operation systems are established and up to three kinds of DNA signals are introduced at the same time. In addition, a more sensitive catalytic logic-based operation is also achieved based on an entropy-driven process. In the experiment, all of the DNA/AuNPs conjugation results are verified by agrose gel. This strategy promises great potential for automatically conjugating DNA stands onto label-free gold nanoparticles and can be extended to constructing DNA/nanoparticle devices for applications in diagnostics, biosensing, and molecular robotics.

Synergetic approach for simple and rapid conjugation of gold nanoparticles with oligonucleotides.

PubMed

Li, Jiuxing; Zhu, Binqing; Yao, Xiujie; Zhang, Yicong; Zhu, Zhi; Tu, Song; Jia, Shasha; Liu, Rudi; Kang, Huaizhi; Yang, Chaoyong James

2014-10-08

Attaching thiolated DNA on gold nanoparticles (AuNPs) has been extremely important in nanobiotechnology because DNA-AuNPs combine the programmability and molecular recognition properties of the biopolymers with the optical, thermal, and catalytic properties of the inorganic nanomaterials. However, current standard protocols to attach thiolated DNA on AuNPs involve time-consuming, tedious steps and do not perform well for large AuNPs, thereby greatly restricting applications of DNA-AuNPs. Here we demonstrate a rapid and facile strategy to attach thiolated DNA on AuNPs based on the excellent stabilization effect of mPEG-SH on AuNPs. AuNPs are first protected by mPEG-SH in the presence of Tween 20, which results in excellent stability of AuNPs in high ionic strength environments and extreme pHs. A high concentration of NaCl can be applied to the mixture of DNA and AuNP directly, allowing highly efficient DNA attachment to the AuNP surface by minimizing electrostatic repulsion. The entire DNA loading process can be completed in 1.5 h with only a few simple steps. DNA-loaded AuNPs are stable for more than 2 weeks at room temperature, and they can precisely hybridize with the complementary sequence, which was applied to prepare core-satellite nanostructures. Moreover, cytotoxicity assay confirmed that the DNA-AuNPs synthesized by this method exhibit lower cytotoxicity than those prepared by current standard methods. The proposed method provides a new way to stabilize AuNPs for rapid and facile loading thiolated DNA on AuNPs and will find wide applications in many areas requiring DNA-AuNPs, including diagnosis, therapy, and imaging.

Oxidized Ni/Au Transparent Electrode in Efficient CH3 NH3 PbI3 Perovskite/Fullerene Planar Heterojunction Hybrid Solar Cells.

PubMed

Lai, Wei-Chih; Lin, Kun-Wei; Wang, Yuan-Ting; Chiang, Tsung-Yu; Chen, Peter; Guo, Tzung-Fang

2016-05-01

The successful application of a Ni/Au transparent electrode for fabricating efficient perovskite-based solar cells is demonstrated. Through interdiffusion of the Ni/Au bilayer, Au forms an interconnected metallic network structure as the transparent electrode. Ni diffuses to the bilayer surface and oxidizes into NiOx becoming an appropriate electrode interlayer. These ITO- and PSS-free devices have potential applications in the design of future cost-effective, low-weight, and stable solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Amperometric Glucose Biosensor Based on Effective Self-Assembly Technology for Preparation of Poly(allylamine hydrochloride)/Au Nanoparticles Multilayers.

PubMed

Ye, Yuhang; Xie, Hangqing; Shao, Xiaobao; Wei, Yuan; Liu, Yuhong; Zhao, Wenbo; Xia, Xinyi

2016-03-01

Novel nanomaterials and nanotechnology for use in bioassay applications represent a rapidly advancing field. This study developed a novel method to fabricate the glucose biosensor with good gold nanoparticles (AuNPs) fixed efficiency based on effective self-assembly technology for preparation of multilayers composed of poly(allylamine hydrochloride) (PAH) and AuNPs. The electrochemical properties of the biosensor based on (AuNPs/PAH)n/AuNPs/glucose oxide (GOD) with different multilayers were systematically investigated. Among the resulting glucose biosensors, electrochemical properties of the biosensor with three times self-assembly processes ((AuNPs/PAH)3/AuNPs/GOD) is best. The GOD biosensor exhibited a fast amperometric response (5 s) to glucose, a good linear current-time relation over a wide range of glucose concentrations from 0.05 to 162 mM, and a low detection limit of 0.029 mM. The GOD biosensor modified with (AuNPs/PAH)n layers will have essential significance and practical application in future owing to the simple method of fabrication and good performance.

Gold nanoparticles cellular toxicity and recovery: adipose Derived Stromal cells.

PubMed

Mironava, Tatsiana; Hadjiargyrou, Michael; Simon, Marcia; Rafailovich, Miriam H

2014-03-01

Gold nanoparticles (AuNPs) are currently used in numerous medical applications. Herein, we describe their in vitro impact on human adipose-derived stromal cells (ADSCs) using 13 nm and 45 nm citrate-coated AuNPs. In their non-differentiated state, ADSCs were penetrated by the AuNPs and stored in vacuoles. The presence of the AuNPs in ADSCs resulted in increased population doubling times, decreased cell motility and cell-mediated collagen contraction. The degree to which the cells were impacted was a function of particle concentration, where the smaller particles required a sevenfold higher concentration to have the same effect as the larger ones. Furthermore, AuNPs reduced adipogenesis as measured by lipid droplet accumulation and adiponectin secretion. These effects correlated with transient increases in DLK1 and with relative reductions in fibronectin. Upon removal of exogenous AuNPs, cellular NP levels decreased and normal ADSC functions were restored. As adiponectin helps regulate energy metabolism, local fluctuations triggered by AuNPs can lead to systemic changes. Hence, careful choice of size, concentration and clinical application duration of AuNPs is warranted.

Theranostic potential of gold nanoparticle-protein agglomerates

NASA Astrophysics Data System (ADS)

Sanpui, Pallab; Paul, Anumita; Chattopadhyay, Arun

2015-11-01

Owing to the ever-increasing applications, glittered with astonishing success of gold nanoparticles (Au NPs) in biomedical research as diagnostic and therapeutic agents, the study of Au NP-protein interaction seems critical for maximizing their theranostic efficiency, and thus demands comprehensive understanding. The mutual interaction of Au NPs and proteins at physiological conditions may result in the aggregation of protein, which can ultimately lead to the formation of Au NP-protein agglomerates. In the present article, we try to appreciate the plausible steps involved in the Au NP-induced aggregation of proteins and also the importance of the proteins' three-dimensional structures in the process. The Au NP-protein agglomerates can potentially be exploited for efficient loading and subsequent release of various therapeutically important molecules, including anticancer drugs, with the unique opportunity of incorporating hydrophilic as well as hydrophobic drugs in the same nanocarrier system. Moreover, the Au NP-protein agglomerates can act as `self-diagnostic' systems, allowing investigation of the conformational state of the associated protein(s) as well as the protein-protein or protein-Au NP interaction within the agglomerates. Furthermore, the potential of these Au NP-protein agglomerates as a novel platform for multifunctional theranostic application along with exciting future-possibilities is highlighted here.

Polyethyleneglycol diacrylate hydrogels with plasmonic gold nanospheres incorporated via functional group optimization

NASA Astrophysics Data System (ADS)

Ponnuvelu, Dinesh Veeran; Kim, Seokbeom; Lee, Jungchul

2017-12-01

We present a facile method for the preparation of polyethyleneglycol diacrylate (PEG-DA) hydrogels with plasmonic gold (Au) nanospheres incorporated for various biological and chemical sensing applications. Plasmonic Au nanospheres were prepared ex situ using the standard citrate reduction method with an average diameter of 3.5 nm and a standard deviation of 0.5 nm, and evaluated for their surface functionalization process intended for uniform dispersion in polymer matrices. UV-Visible spectroscopy reveals the existence of plasmonic properties for pristine Au nanospheres, functionalized Au nanospheres, and PEG-DA with uniformly dispersed functionalized Au nanospheres (hybrid Au/PEG-DA hydrogels). Hybrid Au/PEG-DA hydrogels examined by using Fourier transform infra-red spectroscopy (FT-IR) exhibit the characteristic bands at 1635, 1732 and 2882 cm-1 corresponding to reaction products of OH- originating from oxidized product of citrate, -C=O stretching from ester bond, and C-H stretching of PEG-DA, respectively. Thermal studies of hybrid Au/PEG-DA hydrogels show three-stage decomposition with their stabilities up to 500 °C. Optical properties and thermal stabilities associated with the uniform dispersion of Au nanospheres within hydrogels reported herein will facilitate various biological and chemical sensing applications.

Multifunctional Virus-Nanoshell Assembly for Targeted Hyperthermia and Viral Gene Therapy for Breast Cancer

DTIC Science & Technology

2012-06-01

thin layer of Au. The unique property of Au NS is the tunability of its plasma resonance. Au NS can accumulate heat upon irradiation with NIR light...which is very useful for biomedical applications because tissues are transparent to NIR. Using NIR irradiation , the Au NS can be induced to...and 6161.5 Dalton for the product. Figure 1. (a) UV_VIS spectrum of Au nanoshell. Insect is TEM image of Au Nanoshell, scale bar: 20 nm. (b

Cu-Au Alloys Using Monte Carlo Simulations and the BFS Method for Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Good, Brian; Ferrante, John

1996-01-01

Semi empirical methods have shown considerable promise in aiding in the calculation of many properties of materials. Materials used in engineering applications have defects that occur for various reasons including processing. In this work we present the first application of the BFS method for alloys to describe some aspects of microstructure due to processing for the Cu-Au system (Cu-Au, CuAu3, and Cu3Au). We use finite temperature Monte Carlo calculations, in order to show the influence of 'heat treatment' in the low-temperature phase of the alloy. Although relatively simple, it has enough features that could be used as a first test of the reliability of the technique. The main questions to be answered in this work relate to the existence of low temperature ordered structures for specific concentrations, for example, the ability to distinguish between rather similar phases for equiatomic alloys (CuAu I and CuAu II, the latter characterized by an antiphase boundary separating two identical phases).

Surface-Enhanced Raman Scattering Active Plasmonic Nanoparticles with Ultrasmall Interior Nanogap for Multiplex Quantitative Detection and Cancer Cell Imaging.

PubMed

Li, Jiuxing; Zhu, Zhi; Zhu, Bingqing; Ma, Yanli; Lin, Bingqian; Liu, Rudi; Song, Yanling; Lin, Hui; Tu, Song; Yang, Chaoyong

2016-08-02

Due to its large enhancement effect, nanostructure-based surface-enhanced Raman scattering (SERS) technology had been widely applied for bioanalysis and cell imaging. However, most SERS nanostructures suffer from poor signal reproducibility, which hinders the application of SERS nanostructures in quantitative detection. We report an etching-assisted approach to synthesize SERS-active plasmonic nanoparticles with 1 nm interior nanogap for multiplex quantitative detection and cancer cell imaging. Raman dyes and methoxy poly(ethylene glycol) thiol (mPEG-SH) were attached to gold nanoparticles (AuNPs) to prepare gold cores. Next, Ag atoms were deposited on gold cores in the presence of Pluronic F127 to form a Ag shell. HAuCl4 was used to etch the Ag shell and form an interior nanogap in Au@AgAuNPs, leading to increased Raman intensity of dyes. SERS intensity distribution of Au@AgAuNPs was found to be more uniform than that of aggregated AuNPs. Finally, Au@AgAuNPs were used for multiplex quantitative detection and cancer cell imaging. With the advantages of simple and rapid preparation of Au@AgAuNPs with highly uniform, stable, and reproducible Raman intensity, the method reported here will widen the applications of SERS-active nanoparticles in diagnostics and imaging.

Cathodic Corrosion of a Bulk Wire to Nonaggregated Functional Nanocrystals and Nanoalloys

PubMed Central

2018-01-01

A key enabling step in leveraging the properties of nanoparticles (NPs) is to explore new, simple, controllable, and scalable nanotechnologies for their syntheses. Among “wet” methods, cathodic corrosion has been used to synthesize catalytic aggregates with some control over their size and preferential faceting. Here, we report on a modification of the cathodic corrosion method for producing a range of nonaggregated nanocrystals (Pt, Pd, Au, Ag, Cu, Rh, Ir, and Ni) and nanoalloys (Pt50Au50, Pd50Au50, and AgxAu100–x) with potential for scaling up the production rate. The method employs poly(vinylpyrrolidone) (PVP) as a stabilizer in an electrolyte solution containing nonreducible cations (Na+, Ca2+), and cathodic corrosion of the corresponding wires takes place in the electrolyte under ultrasonication. The ultrasonication not only promotes particle–PVP interactions (enhancing NP dispersion and diluting locally high NP concentration) but also increases the production rate by a factor of ca. 5. Further increase in the production rate can be achieved through parallelization of electrodes to construct comb electrodes. With respect to applications, carbon-supported Pt NPs prepared by the new method exhibit catalytic activity and durability for methanol oxidation comparable or better than the commercial benchmark catalyst. A variety of AgxAu100–x nanoalloys are characterized by ultraviolet–visible absorption spectroscopy and high-resolution transmission electron microscopy. The protocol for NP synthesis by cathodic corrosion should be a step toward its further use in academic research as well as in its practical upscaling. PMID:29446912

Facile formation of dendrimer-stabilized gold nanoparticles modified with diatrizoic acid for enhanced computed tomography imaging applications.

PubMed

Peng, Chen; Li, Kangan; Cao, Xueyan; Xiao, Tingting; Hou, Wenxiu; Zheng, Linfeng; Guo, Rui; Shen, Mingwu; Zhang, Guixiang; Shi, Xiangyang

2012-11-07

We report a facile approach to forming dendrimer-stabilized gold nanoparticles (Au DSNPs) through the use of amine-terminated fifth-generation poly(amidoamine) (PAMAM) dendrimers modified by diatrizoic acid (G5.NH(2)-DTA) as stabilizers for enhanced computed tomography (CT) imaging applications. In this study, by simply mixing G5.NH(2)-DTA dendrimers with gold salt in aqueous solution at room temperature, dendrimer-entrapped gold nanoparticles (Au DENPs) with a mean core size of 2.5 nm were able to be spontaneously formed. Followed by an acetylation reaction to neutralize the dendrimer remaining terminal amines, Au DSNPs with a mean size of 6 nm were formed. The formed DTA-containing [(Au(0))(50)-G5.NHAc-DTA] DSNPs were characterized via different techniques. We show that the Au DSNPs are colloid stable in aqueous solution under different pH and temperature conditions. In vitro hemolytic assay, cytotoxicity assay, flow cytometry analysis, and cell morphology observation reveal that the formed Au DSNPs have good hemocompatibility and are non-cytotoxic at a concentration up to 3.0 μM. X-ray absorption coefficient measurements show that the DTA-containing Au DSNPs have enhanced attenuation intensity, much higher than that of [(Au(0))(50)-G5.NHAc] DENPs without DTA or Omnipaque at the same molar concentration of the active element (Au or iodine). The formed DTA-containing Au DSNPs can be used for CT imaging of cancer cells in vitro as well as for blood pool CT imaging of mice in vivo with significantly improved signal enhancement. With the two radiodense elements of Au and iodine incorporated within one particle, the formed DTA-containing Au DSNPs may be applicable for CT imaging of various biological systems with enhanced X-ray attenuation property and detection sensitivity.

Cytotoxicity of various types of gold-mesoporous silica nanoparticles in human breast cancer cells

PubMed Central

Liu, Guomu; Li, Qiongshu; Ni, Weihua; Zhang, Nannan; Zheng, Xiao; Wang, Yingshuai; Shao, Dan; Tai, Guixiang

2015-01-01

Recently, gold nanoparticles (AuNPs) have shown promising biological applications due to their unique electronic and optical properties. However, the potential toxicity of AuNPs remains a major hurdle that impedes their use in clinical settings. Mesoporous silica is very suitable for the use as a coating material for AuNPs and might not only reduce the cytotoxicity of cetyltrimethylammonium bromide-coated AuNPs but might also facilitate the loading and delivery of drugs. Herein, three types of rod-like gold-mesoporous silica nanoparticles (termed bare AuNPs, core–shell Au@mSiO2NPs, and Janus Au@mSiO2NPs) were specially designed, and the effects of these AuNPs on cellular uptake, toxic behavior, and mechanism were then systematically studied. Our results indicate that bare AuNPs exerted higher toxicity than the Au@mSiO2NPs and that Janus Au@mSiO2NPs exhibited the lowest toxicity in human breast cancer MCF-7 cells, consistent with the endocytosis capacity of the nanoparticles, which followed the order, bare AuNPs > core–shell Au@mSiO2NPs > Janus Au@mSiO2NPs. More importantly, the AuNPs-induced apoptosis of MCF-7 cells exhibited features that were characteristic of intracellular reactive oxygen species (ROS) generation, activation of c-Jun-N-terminal kinase (JNK) phosphorylation, an enhanced Bax-to-Bcl-2 ratio, and loss of the mitochondrial membrane potential. Simultaneously, cytochrome c was released from mitochondria, and the caspase-3/9 cascade was activated. Moreover, both ROS scavenger (N-acetylcysteine) and JNK inhibitor (SP600125) partly blocked the induction of apoptosis in all AuNPs-treated cells. Taken together, these findings suggest that all AuNPs induce apoptosis through the ROS-/JNK-mediated mitochondrial pathway. Thus, Janus Au@mSiO2NPs exhibit the potential for applications in biomedicine, thus aiding the clinical translation of AuNPs. PMID:26491285

Plasmon-enhanced versatile optical nonlinearities in a Au-Ag-Au multi-segmental hybrid structure.

PubMed

Yao, Lin-Hua; Zhang, Jun-Pei; Dai, Hong-Wei; Wang, Ming-Shan; Zhang, Lu-Man; Wang, Xia; Han, Jun-Bo

2018-06-27

A Au-Ag-Au multi-segmental hybrid structure has been synthesized by using an electrodeposition method based on an anodic aluminum oxide (AAO) membrane. The third-order optical nonlinearities, second harmonic generation (SHG) and photoluminescence (PL) properties containing ultrafast supercontinuum generation and plasmon mediated thermal emission have been investigated. Significant optical enhancements have been obtained near surface plasmon resonance wavelength in all the abovementioned nonlinear processes. Comparative studies between the Au-Ag-Au multi-segmental hybrid structure and the corresponding single-component Au and Ag hybrid structures demonstrate that the Au-Ag-Au multi-segmental hybrid structure has much larger optical nonlinearities than its counterparts. These results demonstrate that the Au-Ag-Au hybrid structure is a promising candidate for applications in plasmonic devices and enhancement substrates.

Au/ZnO nanoarchitectures with Au as both supporter and antenna of visible-light

NASA Astrophysics Data System (ADS)

Liu, Tianyu; Chen, Wei; Hua, Yuxiang; Liu, Xiaoheng

2017-01-01

In this paper, we fabricate Au/ZnO nanostructure with smaller ZnO nanoparticles loaded onto bigger gold nanoparticles via combining seed-mediated method and sol-gel method. The obtained Au/ZnO nanocomposites exhibit excellent properties in photocatalysis process like methyl orange (MO) degradation and oxidative conversion of methanol into formaldehyde under visible light irradiation. The enhanced properties were ascribed to the surface plasmon resonance (SPR) effect of Au nanoparticles, which could contribute to the separation of photo-excited electrons and holes and facilitate the process of absorbing visible light. This paper contributes to the emergence of multi-functional nanocomposites with possible applications in visible-light driven photocatalysts and makes the Au/ZnO photocatalyst an exceptional choice for practical applications such as environmental purification of organic pollutants in aqueous solution and the synthesis of fine chemicals and intermediates.

Layered Metal Nanoparticle Structures on Electrodes for Sensing, Switchable Controlled Uptake/Release, and Photo-electrochemical Applications.

PubMed

Tel-Vered, Ran; Kahn, Jason S; Willner, Itamar

2016-01-06

Layered metal nanoparticle (NP) assemblies provide highly porous and conductive composites of unique electrical and optical (plasmonic) properties. Two methods to construct layered metal NP matrices are described, and these include the layer-by-layer deposition of NPs, or the electropolymerization of monolayer-functionalized NPs, specifically thioaniline-modified metal NPs. The layered NP composites are used as sensing matrices through the use of electrochemistry or surface plasmon resonance (SPR) as transduction signals. The crosslinking of the metal NP composites with molecular receptors, or the imprinting of molecular recognition sites into the electropolymerized NP matrices lead to selective and chiroselective sensing interfaces. Furthermore, the electrosynthesis of redox-active, imprinted, bis-aniline bridged Au NP composites yields electrochemically triggered "sponges" for the switchable uptake and release of electron-acceptor substrates, and results in conductive surfaces of electrochemically controlled wettability. Also, photosensitizer-relay-crosslinked Au NP composites, or electrochemically polymerized layered semiconductor quantum dot/metal NP matrices on electrodes, are demonstrated as functional nanostructures for photoelectrochemical applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

NIR-assisted orchid virus therapy using urchin bimetallic nanomaterials in phalaenopsis

NASA Astrophysics Data System (ADS)

Chen, Shin-Yu; Cheng, Liang-Chien; Chen, Chieh-Wei; Lee, Po-Han; Yu, Fengjiao; Zhou, Wuzong; Liu, Ru-Shi; Do, Yi-Yin; Huang, Pung-Ling

2013-12-01

The use of nanoparticles has drawn special attention, particularly in the treatment of plant diseases. Cymbidium mosaic virus (CymMV) and Odontoglossum ring spot virus (ORSV) are the most prevalent and serious diseases that affect the development of the orchid industry. In this study we treated nanoparticles as a strategy for enhancing the resistance of orchids against CymMV and ORSV. After chitosan-modified gold nanoparticles (Au NPs) were injected into Phalaenopsis leaves, the injected leaves were exposed to 980 nm laser for light-heat conversion. To evaluate virus elimination in the treated Phalaenopsis leaves, the transcripts of coat protein genes and the production of viral proteins were assessed by reverse transcription-Polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The expression of coat protein genes for both CymMV and ORSV was significantly lower in the chitosan-modified Au NP-treated Phalaenopsis leaves than in the control. Similarly, the amount of coat proteins for both viruses in the Phalaenopsis leaves was lower than that in the control (without nanoparticle injection). We propose that the temperature increase in the chitosan-modified Au NP-treated Phalaenopsis tissues after laser exposure reduces the viral population, consequently conferring resistance against CymMV and ORSV. Our findings suggest that the application of chitosan-modified Au NPs is a promising new strategy for orchid virus therapy.

Fabrication of Au 25(SG) 18–ZIF-8 Nanocomposites: A Facile Strategy to Position Au 25(SG) 18 Nanoclusters Inside and Outside ZIF-8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yucheng; Fan, Shiyan; Yu, Wenqian

Multifunctional composite materials are currently highly desired for sustainable energy applications. A general strategy to integrate atomically precise Au 25(SG) 18 with ZIF-8 (Zn(MeIm) 2, MeIm = 2-methylimidazole), is developed in this paper via the typical Zn-carboxylate type of linkage. Au 25(SG) 18 are uniformly encapsulated into a ZIF-8 framework (Au 25(SG) 18@ZIF-8) by coordination-assisted self-assembly. In contrast, Au 25(SG) 18 integrated by simple impregnation is oriented along the outer surface of ZIF-8 (Au 25(SG) 18/ZIF-8). The porous structure and thermal stability of these nanocomposites are characterized by N 2 adsorption–desorption isothermal analysis and thermal gravimetric analysis. The distribution ofmore » Au 25(SG) 18 in the two nanocomposites is confirmed by electron microscopy, and the accessibility of Au 25(SG) 18 is evaluated by the 4-nitrophenol reduction reaction. The as-prepared nanocomposites retain the high porosity and thermal stability of the ZIF-8 matrix, while also exhibiting the desired catalytic and optical properties derived from the integrated Au 25(SG) 18 nanoclusters (NCs). Au 25(SG) 18@ZIF-8 with isolated Au 25 sites is a promising heterogenous catalyst with size selectivity imparted by the ZIF-8 matrix. Finally, the structural distinction between Au 25(SG) 18@ZIF-8 and Au 25(SG) 18/ZIF-8 determines their different emission features, and provides a new strategy to adjust the optical behavior of Au 25(SG) 18 for applications in bioimaging and biotherapy.« less

Fabrication of Au 25(SG) 18–ZIF-8 Nanocomposites: A Facile Strategy to Position Au 25(SG) 18 Nanoclusters Inside and Outside ZIF-8

DOE PAGES

Luo, Yucheng; Fan, Shiyan; Yu, Wenqian; ...

2017-12-22

Multifunctional composite materials are currently highly desired for sustainable energy applications. A general strategy to integrate atomically precise Au 25(SG) 18 with ZIF-8 (Zn(MeIm) 2, MeIm = 2-methylimidazole), is developed in this paper via the typical Zn-carboxylate type of linkage. Au 25(SG) 18 are uniformly encapsulated into a ZIF-8 framework (Au 25(SG) 18@ZIF-8) by coordination-assisted self-assembly. In contrast, Au 25(SG) 18 integrated by simple impregnation is oriented along the outer surface of ZIF-8 (Au 25(SG) 18/ZIF-8). The porous structure and thermal stability of these nanocomposites are characterized by N 2 adsorption–desorption isothermal analysis and thermal gravimetric analysis. The distribution ofmore » Au 25(SG) 18 in the two nanocomposites is confirmed by electron microscopy, and the accessibility of Au 25(SG) 18 is evaluated by the 4-nitrophenol reduction reaction. The as-prepared nanocomposites retain the high porosity and thermal stability of the ZIF-8 matrix, while also exhibiting the desired catalytic and optical properties derived from the integrated Au 25(SG) 18 nanoclusters (NCs). Au 25(SG) 18@ZIF-8 with isolated Au 25 sites is a promising heterogenous catalyst with size selectivity imparted by the ZIF-8 matrix. Finally, the structural distinction between Au 25(SG) 18@ZIF-8 and Au 25(SG) 18/ZIF-8 determines their different emission features, and provides a new strategy to adjust the optical behavior of Au 25(SG) 18 for applications in bioimaging and biotherapy.« less

Fabrication of Au25 (SG)18 -ZIF-8 Nanocomposites: A Facile Strategy to Position Au25 (SG)18 Nanoclusters Inside and Outside ZIF-8.

PubMed

Luo, Yucheng; Fan, Shiyan; Yu, Wenqian; Wu, Zili; Cullen, David A; Liang, Chaolun; Shi, Jianying; Su, Chengyong

2018-02-01

Multifunctional composite materials are currently highly desired for sustainable energy applications. A general strategy to integrate atomically precise Au 25 (SG) 18 with ZIF-8 (Zn(MeIm) 2 , MeIm = 2-methylimidazole), is developed via the typical Zn-carboxylate type of linkage. Au 25 (SG) 18 are uniformly encapsulated into a ZIF-8 framework (Au 25 (SG) 18 @ZIF-8) by coordination-assisted self-assembly. In contrast, Au 25 (SG) 18 integrated by simple impregnation is oriented along the outer surface of ZIF-8 (Au 25 (SG) 18 /ZIF-8). The porous structure and thermal stability of these nanocomposites are characterized by N 2 adsorption-desorption isothermal analysis and thermal gravimetric analysis. The distribution of Au 25 (SG) 18 in the two nanocomposites is confirmed by electron microscopy, and the accessibility of Au 25 (SG) 18 is evaluated by the 4-nitrophenol reduction reaction. The as-prepared nanocomposites retain the high porosity and thermal stability of the ZIF-8 matrix, while also exhibiting the desired catalytic and optical properties derived from the integrated Au 25 (SG) 18 nanoclusters (NCs). Au 25 (SG) 18 @ZIF-8 with isolated Au 25 sites is a promising heterogenous catalyst with size selectivity imparted by the ZIF-8 matrix. The structural distinction between Au 25 (SG) 18 @ZIF-8 and Au 25 (SG) 18 /ZIF-8 determines their different emission features, and provides a new strategy to adjust the optical behavior of Au 25 (SG) 18 for applications in bioimaging and biotherapy. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gold nanoparticle size and shape influence on osteogenesis of mesenchymal stem cells

NASA Astrophysics Data System (ADS)

Li, Jingchao; Li, Jia'en Jasmine; Zhang, Jing; Wang, Xinlong; Kawazoe, Naoki; Chen, Guoping

2016-04-01

Gold nanoparticles (AuNPs) have been extensively explored for biomedical applications due to their advantages of facile synthesis and surface functionalization. Previous studies have suggested that AuNPs can induce differentiation of stem cells into osteoblasts. However, how the size and shape of AuNPs affect the differentiation response of stem cells has not been elucidated. In this work, a series of bovine serum albumin (BSA)-coated Au nanospheres, Au nanostars and Au nanorods with different diameters of 40, 70 and 110 nm were synthesized and their effects on osteogenic differentiation of human mesenchymal stem cells (hMSCs) were investigated. All the AuNPs showed good cytocompatibility and did not influence proliferation of hMSCs at the studied concentrations. Osteogenic differentiation of hMSCs was dependent on the size and shape of AuNPs. Sphere-40, sphere-70 and rod-70 significantly increased the alkaline phosphatase (ALP) activity and calcium deposition of cells while rod-40 reduced the ALP activity and calcium deposition. Gene profiling revealed that the expression of osteogenic marker genes was down-regulated after incubation with rod-40. However, up-regulation of these genes was found in the sphere-40, sphere-70 and rod-70 treatment. Moreover, it was found that the size and shape of AuNPs affected the osteogenic differentiation of hMSCs through regulating the activation of Yes-associated protein (YAP). These results indicate that the size and shape of AuNPs had an influence on the osteogenic differentiation of hMSCs, which should provide useful guidance for the preparation of AuNPs with defined size and shape for their biomedical applications.Gold nanoparticles (AuNPs) have been extensively explored for biomedical applications due to their advantages of facile synthesis and surface functionalization. Previous studies have suggested that AuNPs can induce differentiation of stem cells into osteoblasts. However, how the size and shape of AuNPs affect the differentiation response of stem cells has not been elucidated. In this work, a series of bovine serum albumin (BSA)-coated Au nanospheres, Au nanostars and Au nanorods with different diameters of 40, 70 and 110 nm were synthesized and their effects on osteogenic differentiation of human mesenchymal stem cells (hMSCs) were investigated. All the AuNPs showed good cytocompatibility and did not influence proliferation of hMSCs at the studied concentrations. Osteogenic differentiation of hMSCs was dependent on the size and shape of AuNPs. Sphere-40, sphere-70 and rod-70 significantly increased the alkaline phosphatase (ALP) activity and calcium deposition of cells while rod-40 reduced the ALP activity and calcium deposition. Gene profiling revealed that the expression of osteogenic marker genes was down-regulated after incubation with rod-40. However, up-regulation of these genes was found in the sphere-40, sphere-70 and rod-70 treatment. Moreover, it was found that the size and shape of AuNPs affected the osteogenic differentiation of hMSCs through regulating the activation of Yes-associated protein (YAP). These results indicate that the size and shape of AuNPs had an influence on the osteogenic differentiation of hMSCs, which should provide useful guidance for the preparation of AuNPs with defined size and shape for their biomedical applications. Electronic supplementary information (ESI) available: Additional experimental results. See DOI: 10.1039/c5nr08808a

The coupled geochemistry of Au and As in pyrite from hydrothermal ore deposits

NASA Astrophysics Data System (ADS)

Deditius, Artur P.; Reich, Martin; Kesler, Stephen E.; Utsunomiya, Satoshi; Chryssoulis, Stephen L.; Walshe, John; Ewing, Rodney C.

2014-09-01

The ubiquity of Au-bearing arsenian pyrite in hydrothermal ore deposits suggests that the coupled geochemical behaviour of Au and As in this sulfide occurs under a wide range of physico-chemical conditions. Despite significant advances in the last 20 years, fundamental factors controlling Au and As ratios in pyrite from ore deposits remain poorly known. Here we explore these constraints using new and previously published EMPA, LA-ICP-MS, SIMS, and μ-PIXE analyses of As and Au in pyrite from Carlin-type Au, epithermal Au, porphyry Cu, Cu-Au, and orogenic Au deposits, volcanogenic massive sulfide (VHMS), Witwatersrand Au, iron oxide copper gold (IOCG), and coal deposits. Pyrite included in the data compilation formed under temperatures from ∼30 to ∼600 °C and in a wide variety of geological environments. The pyrite Au-As data form a wedge-shaped zone in compositional space, and the fact that most data points plot below the solid solubility limit defined by Reich et al. (2005) indicate that Au1+ is the dominant form of Au in arsenian pyrite and that Au-bearing ore fluids that deposit this sulfide are mostly undersaturated with respect to native Au. The analytical data also show that the solid solubility limit of Au in arsenian pyrite defined by an Au/As ratio of 0.02 is independent of the geochemical environment of pyrite formation and rather depends on the crystal-chemical properties of pyrite and post-depositional alteration. Compilation of Au-As concentrations and formation temperatures for pyrite indicates that Au and As solubility in pyrite is retrograde; Au and As contents decrease as a function of increasing temperature from ∼200 to ∼500 °C. Based on these results, two major Au-As trends for Au-bearing arsenian pyrite from ore deposits are defined. One trend is formed by pyrites from Carlin-type and orogenic Au deposits where compositions are largely controlled by fluid-rock interactions and/or can be highly perturbed by changes in temperature and alteration by hydrothermal fluids. The second trend consists of pyrites from porphyry Cu and epithermal Au deposits, which are characterised by compositions that preserve the Au/As signature of mineralizing magmatic-hydrothermal fluids, confirming the role of this sulfide in controlling metal ratios in ore systems.

Ion irradiation synthesis of Ag–Au bimetallic nanospheroids in SiO{sub 2} glass substrate with tunable surface plasmon resonance frequency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Xuan; Yu, Ruixuan; Takayanagi, Shinya

2013-08-07

Ag–Au bimetallic nanospheroids with tunable localized surface plasmon resonance (LSPR) were synthesized by 100 keV Ar–ion irradiation of 30 nm Ag–Au bimetallic films deposited on SiO{sub 2} glass substrates. A shift of the LSPR peaks toward shorter wavelengths was observed up to an irradiation fluence of 1.0 × 10{sup 17} cm{sup −2}, and then shifted toward the longer wavelength because of the increase of fragment volume under ion irradiation. Further control of LSPR frequency over a wider range was realized by modifying the chemical components. The resulting LSPR frequencies lie between that of the pure components, and an approximate linearmore » shift of the LSPR toward the longer wavelength with the Au concentration was achieved, which is in good agreement with the theoretical calculations based on Gans theory. In addition, the surface morphology and compositions were examined with a scanning electron microscope equipped with an energy dispersive spectrometer, and microstructural characterizations were performed using a transmission electron microscope. The formation of isolated photosensitive Ag–Au nanospheroids with a FCC structure partially embedded in the SiO{sub 2} substrate was confirmed, which has a potential application in solid-state devices.« less

Study of Ag induced bimetallic (Au-Ag) nanowires on silicon (5 5 12) surfaces: Experiment and theoretical aspects

NASA Astrophysics Data System (ADS)

Bhukta, Anjan; Bagarti, Trilochan; Guha, Puspendu; Ravulapalli, Sathyavathi; Satpati, Biswarup; Rakshit, Bipul; Maiti, Paramita; Parlapalli, Venkata Satyam

2017-10-01

The reconstructed vicinal (high index) silicon surfaces, such as, Si (5 5 12) composes row-like structures that can be used as templates for growing aligned nanowires. By using a sub-monolayers of Ag, prior to Au deposition on reconstructed Si (5 512) surface, intermixing of Au and Ag, enhancement of aspect ratio of bimetallic Au-Ag nanowires with tunable morphology is reported. This is attributed to a combined effect of pre-grown Ag strips as nucleation centers for incoming Au ad-atoms and anisotropic Au-Ag intermixing. To achieve optimum conditions for the growth of larger aspect ratio Au-Ag nanostructures, the growth kinetics have been studied by varying growth and annealing temperatures. At ≈400 °C, the Ag diffused into silicon substrate and the inter-diffusion found to inhibit the formation of Au-Ag bimetallic nanostructures. Controlled experiments under ultra-high vacuum condition in a molecular beam epitaxy system and in-situ scanning tunneling microscopy measurements along with ex-situ scanning transmission and secondary electron microscopy measurements have been carried out to understand the bimetallic nanostructure growth. Kinetic Monte Carlo (KMC) simulations based on kinematics of ad-atoms on an anisotropic template with a solid on solid model in which the relative ratios of binding energies (that are obtained from the Density Functional Theory) have been used and the KMC simulations results agree with the experimental observations. Advantage of having bimetallic structures as effective substrates for Surface enhanced Raman spectroscopy application is demonstrated by detecting Rhodamine 6 G (R6G) molecule at the concentration of 10-7M.

A ternary functional Ag@GO@Au sandwiched hybrid as an ultrasensitive and stable surface enhanced Raman scattering platform

NASA Astrophysics Data System (ADS)

Zhang, Cong-yun; Hao, Rui; Zhao, Bin; Hao, Yao-wu; Liu, Ya-qing

2017-07-01

The graphene-mediated surface enhanced Raman scattering (SERS) substrates by virtues of plasmonic metal nanostructures and graphene or its derivatives have attracted tremendous interests which are expected to make up the deficiency of traditional plasmonic metal substrates. Herein, we designed and fabricated a novel ternary Ag@GO@Au sandwich hybrid wherein the ultrathin graphene oxide (GO) films were seamlessly wrapped around the hierarchical flower-like Ag particle core and meanwhile provided two-dimensional anchoring scaffold for the coating of Au nanoparticles (NPs). The surface coverage density of loading Au NPs could be readily controlled by tuning the dosage amount of Au particle solutions. These features endowed the sandwiched structures high enrichment capability for analytes such as aromatic molecules and astonishing SERS performance. The Raman signals were enormously enhanced with an ultrasensitive detection limit of rhodamine-6G (R6G) as low as 10-13 M based on the chemical enhancement from GO and multi-dimensional plasmonic coupling between the metal nanoparticles. In addition, the GO interlayer as an isolating shell could effectively prevent the metal-molecule direct interaction and suppress the oxidation of Ag after exposure at ambient condition which enabled the substrates excellent reproducibility with less than 6% signal variations and prolonged life-time. To evaluate the feasibility and the practical application for SERS detection in real-world samples based on GO sandwiched hybrid as SERS-active substrate, three different prohibited colorants with a series of concentrations were measured with a minimum detected concentration down to 10-9 M. Furthermore, the prepared GO sandwiched nanostructures can be used to identify different types of colorants existing in red wine, implying the great potential applications for single-particle SERS sensing of biotechnology and on-site monitoring in food security.

Carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures with tunable size for enhanced visible-light-driven photocatalysis

NASA Astrophysics Data System (ADS)

Li, Yayuan; Cao, Shubo; Zhang, Ang; Zhang, Chen; Qu, Ting; Zhao, Yongbin; Chen, Aihua

2018-07-01

It is of great importance to extend the UV response of anatase TiO2 into the visible light range for the practical applications. Here, a facile rout to carbon and nitrogen co-doped, Au loaded bowl-like TiO2 nanostructures with tunable size are proposed by using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) spherical micelles as templates. Amphiphilic PS-b-P4VP self-assembles to form PS@P4VP core-shell spherical micelles with P4VP as the out layer in an evaporable mixed solvents of ethanol/tetrahydrofuran (THF). The size of uniform PS@P4VP spherical micelles can be precisely tuned in the range of a few nm to several hundred nm by controlling the molecular composition of the BCPs. Bowl-like TiO2 nanostructures with a replicate size loaded with highly dispersed Au nanoparticles (NPs) of ∼5 nm in diameter are fabricated from these spherical micelles because of strong complex ability of pyridine groups. PS-b-P4VP provides carbon and nitrogen sources to dope the resulting samples simultaneously. The special carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures exhibit much higher photocatalytic activity in the photodegradation of rhodamine B (RhB) compared to Au/P25 under visible light irradiation. Furthermore, the photocatalytic activity is significantly influenced by the BCP molecular composition due to different surface area and loading capacity of the resulting samples. This study provides a facile way to synthesize multi-element doped hollow or bowl-like nanoparticles with tunable size in the nanometer range which have potential application at photocatalysis, oxygen reduction reaction, etc.

Gold core/ceria shell-based redox active nanozyme mimicking the biological multienzyme complex phenomenon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhagat, Stuti; Srikanth Vallabani, N. V.; Shutthanandan, Vaithiyalingam

Catalytically active individual gold (Au) and cerium oxide (CeO2) nanoparticles are well known to exhibit specific enzyme-like activities, such as natural catalase, oxidase, superoxide dismutase, and peroxidase enzymes. These activities have been maneuvered to design several biological applications such as immunoassays, glucose detection, radiation and free radical protection and tissue engineering. A functional nanozyme depicting multienzyme like properties that functions as a synthetic super enzyme has eluded the researchers in the nanoscience community for past decade. In current report, we have designed a functional multienzyme in the form of Gold (core)-CeO2 (shell) nanoparticles (Au@CeO2 CSNPs) exhibiting excellent peroxidase, catalase andmore » superoxide dismutase enzyme-like activities that are controlled simply by tuning the pH. The reaction kinetic parameters reveal that the peroxidase-like activity of this core shell nanozyme is comparable to natural HRP enzyme. Unlike peroxidase-like activity exhibited by other nanomaterials, Au@CeO2 CSNPs showed decrease in hydroxyl radical formation, suggesting that the bio catalytic reactions are performed by efficient electron transfers. A significant enzyme-like activity of this core shell nanoparticle was conserved at extreme pH (2 – 11) and temperatures (up to 90 °C), clearly suggesting the superiority over natural enzymes. Further, the utility of peroxidase-like activity of this core shell nanoparticles was extended for the detection of glucose, which showed a linear range of detection between (100 µM – 1 mM). It is hypothesized that the proximity of the redox potentials of Au+/Au and Ce (III)/Ce (IV) may result in a redox couple promoting the multienzyme activity of core shell nanoparticles. Au@CeO2 CSNPs may open new directions for development of single platform sensors in multiple biosensing applications.« less

One-Step Synthesis of Au-Ag Nanowires through Microorganism-Mediated, CTAB-Directed Approach.

PubMed

Xu, Luhang; Huang, Dengpo; Chen, Huimei; Jing, Xiaoling; Huang, Jiale; Odoom-Wubah, Tareque; Li, Qingbiao

2018-05-28

Synthesis and applications of one dimensional (1D) metal nanostructures have attracted much attention. However, one-step synthesis of bimetallic nanowires (NWs) has remained challenging. In this work, we developed a microorganism-mediated, hexadecyltrimethylammonium bromide (CTAB)-directed (MCD) approach to synthesize closely packed and long Au-Ag NWs with the assistance of a continuous injection pump. Characterization results confirmed that the branched Au-Ag alloy NWs was polycrystalline. And the Au-Ag NWs exhibited a strong absorbance at around 1950 nm in the near-infrared (NIR) region, which can find potential application in NIR absorption. In addition, the Au-Ag NWs showed excellent surface-enhanced Raman scattering (SERS) enhancement when 4-mercaptobenzoic acid (MBA) and rhodamine 6G (R6G) were used as probe molecules.

Neurite outgrowth stimulatory effects of myco synthesized AuNPs from Hericium erinaceus (Bull.: Fr.) Pers. on pheochromocytoma (PC-12) cells

PubMed Central

Raman, Jegadeesh; Lakshmanan, Hariprasath; John, Priscilla A; Zhijian, Chan; Periasamy, Vengadesh; David, Pamela; Naidu, Murali; Sabaratnam, Vikineswary

2015-01-01

Background Hericium erinaceus has been reported to have a wide range of medicinal properties such as stimulation of neurite outgrowth, promotion of functional recovery of axonotmetic peroneal nerve injury, antioxidant, antihypertensive, and antidiabetic properties. In recent years, the green synthesis of gold nanoparticles (AuNPs) has attracted intense interest due to the potential use in biomedical applications. The aim of this study was to investigate the effects of AuNPs from aqueous extract of H. erinaceus on neurite outgrowth of rat pheochromocytoma (PC-12) cells. Methods The formation of AuNPs was characterized by UV–visible spectrum, energy dispersive X-ray (EDX), field-emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), particle size distribution, and Fourier transform-infrared spectroscopy (FTIR). Furthermore, the neurite extension study of synthesized AuNPs was evaluated by in vitro assay. Results The AuNPs exhibited maximum absorbance between 510 and 600 nm in UV–visible spectrum. FESEM and TEM images showed the existence of nanoparticles with sizes of 20–40 nm. FTIR measurements were carried out to identify the possible biomolecules responsible for capping and efficient stabilization of the nanoparticles. The purity and the crystalline properties were confirmed by EDX diffraction analysis, which showed strong signals with energy peaks in the range of 2–2.4 keV, indicating the existence of gold atoms. The synthesized AuNPs showed significant neurite extension on PC-12 cells. Nerve growth factor 50 ng/mL was used as a positive control. Treatment with different concentrations (nanograms) of AuNPs resulted in neuronal differentiation and neuronal elongation. AuNPs induced maximum neurite outgrowth of 13% at 600 ng/mL concentration. Conclusion In this study, the AuNPs synthesis was achieved by a simple, low-cost, and rapid bioreduction approach. AuNPs were shown to have potential neuronal differentiation and stimulated neurite outgrowth. The water-soluble bioconstituents could be responsible for the neuroactivity. This is the first report for the biosynthesis of AuNPs using the hot aqueous extract of H. erinaceus. PMID:26425086

Neurite outgrowth stimulatory effects of myco synthesized AuNPs from Hericium erinaceus (Bull.: Fr.) Pers. on pheochromocytoma (PC-12) cells.

PubMed

Raman, Jegadeesh; Lakshmanan, Hariprasath; John, Priscilla A; Zhijian, Chan; Periasamy, Vengadesh; David, Pamela; Naidu, Murali; Sabaratnam, Vikineswary

2015-01-01

Hericium erinaceus has been reported to have a wide range of medicinal properties such as stimulation of neurite outgrowth, promotion of functional recovery of axonotmetic peroneal nerve injury, antioxidant, antihypertensive, and antidiabetic properties. In recent years, the green synthesis of gold nanoparticles (AuNPs) has attracted intense interest due to the potential use in biomedical applications. The aim of this study was to investigate the effects of AuNPs from aqueous extract of H. erinaceus on neurite outgrowth of rat pheochromocytoma (PC-12) cells. The formation of AuNPs was characterized by UV-visible spectrum, energy dispersive X-ray (EDX), field-emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), particle size distribution, and Fourier transform-infrared spectroscopy (FTIR). Furthermore, the neurite extension study of synthesized AuNPs was evaluated by in vitro assay. The AuNPs exhibited maximum absorbance between 510 and 600 nm in UV-visible spectrum. FESEM and TEM images showed the existence of nanoparticles with sizes of 20-40 nm. FTIR measurements were carried out to identify the possible biomolecules responsible for capping and efficient stabilization of the nanoparticles. The purity and the crystalline properties were confirmed by EDX diffraction analysis, which showed strong signals with energy peaks in the range of 2-2.4 keV, indicating the existence of gold atoms. The synthesized AuNPs showed significant neurite extension on PC-12 cells. Nerve growth factor 50 ng/mL was used as a positive control. Treatment with different concentrations (nanograms) of AuNPs resulted in neuronal differentiation and neuronal elongation. AuNPs induced maximum neurite outgrowth of 13% at 600 ng/mL concentration. In this study, the AuNPs synthesis was achieved by a simple, low-cost, and rapid bioreduction approach. AuNPs were shown to have potential neuronal differentiation and stimulated neurite outgrowth. The water-soluble bioconstituents could be responsible for the neuroactivity. This is the first report for the biosynthesis of AuNPs using the hot aqueous extract of H. erinaceus.

Nanoporous Gold: Fabrication, Characterization, and Applications

PubMed Central

Seker, Erkin; Reed, Michael L.; Begley, Matthew R.

2009-01-01

Nanoporous gold (np-Au) has intriguing material properties that offer potential benefits for many applications due to its high specific surface area, well-characterized thiol-gold surface chemistry, high electrical conductivity, and reduced stiffness. The research on np-Au has taken place on various fronts, including advanced microfabrication and characterization techniques to probe unusual nanoscale properties and applications spanning from fuel cells to electrochemical sensors. Here, we provide a review of the recent advances in np-Au research, with special emphasis on microfabrication and characterization techniques. We conclude the paper with a brief outline of challenges to overcome in the study of nanoporous metals.

Preparation and evaluation of nanocellulose-gold nanoparticle nanocomposites for SERS applications.

PubMed

Wei, Haoran; Rodriguez, Katia; Renneckar, Scott; Leng, Weinan; Vikesland, Peter J

2015-08-21

Nanocellulose is of research interest due to its extraordinary optical, thermal, and mechanical properties. The incorporation of guest nanoparticles into nanocellulose substrates enables production of novel nanocomposites with a broad range of applications. In this study, gold nanoparticle/bacterial cellulose (AuNP/BC) nanocomposites were prepared and evaluated for their applicability as surface-enhanced Raman scattering (SERS) substrates. The nanocomposites were prepared by citrate mediated in situ reduction of Au(3+) in the presence of a BC hydrogel at 303 K. Both the size and morphology of the AuNPs were functions of the HAuCl4 and citrate concentrations. At high HAuCl4 concentrations, Au nanoplates form within the nanocomposites and are responsible for high SERS enhancements. At lower HAuCl4 concentrations, uniform nanospheres form and the SERS enhancement is dependent on the nanosphere size. The time-resolved increase in the SERS signal was probed as a function of drying time with SERS 'hot-spots' primarily forming in the final minutes of nanocomposite drying. The application of the AuNP/BC nanocomposites for detection of the SERS active dyes MGITC and R6G as well as the environmental contaminant atrazine is illustrated as is its use under low and high pH conditions. The results indicate the broad applicability of this nanocomposite for analyte detection.

Biosynthesis and stabilization of Au and Au Ag alloy nanoparticles by fungus, Fusarium semitectum

NASA Astrophysics Data System (ADS)

Dasaratrao Sawle, Balaji; Salimath, Basavaraja; Deshpande, Raghunandan; Dhondojirao Bedre, Mahesh; Krishnamurthy Prabhakar, Belawadi; Venkataraman, Abbaraju

2008-09-01

Crystallized and spherical-shaped Au and Au-Ag alloy nanoparticles have been synthesized and stabilized using a fungus, F . semitectum in an aqueous system. Aqueous solutions of chloroaurate ions for Au and chloroaurate and Ag+ ions (1 : 1 ratio) for Au-Ag alloy were treated with an extracellular filtrate of F . semitectum biomass for the formation of Au nanoparticles (AuNP) and Au-Ag alloy nanoparticles (Au-AgNP). Analysis of the feasibility of the biosynthesized nanoparticles and core-shell alloy nanoparticles from fungal strains is particularly significant. The resultant colloidal suspensions are highly stable for many weeks. The obtained Au and Au-Ag alloy nanoparticles were characterized by the surface plasmon resonance (SPR) peaks using a UV-vis spectrophotometer, and the structure, morphology and size were determined by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and transmission electron microscopy (TEM). Possible optoelectronics and medical applications of these nanoparticles are envisaged.

Structural, electronic and magnetic properties of Au-based monolayer derivatives in honeycomb structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kapoor, Pooja, E-mail: pupooja16@gmail.com; Sharma, Munish; Ahluwalia, P. K.

2016-05-23

We present electronic properties of atomic layer of Au, Au{sub 2}-N, Au{sub 2}-O and Au{sub 2}-F in graphene-like structure within the framework of density functional theory (DFT). The lattice constant of derived monolayers are found to be higher than the pristine Au monolayer. Au monolayer is metallic in nature with quantum ballistic conductance calculated as 4G{sub 0}. Similarly, Au{sub 2}-N and Au{sub 2}-F monolayers show 4G{sub 0} and 2G{sub 0} quantum conductance respectively while semiconducting nature with calculated band gap of 0.28 eV has been observed for Au{sub 2}-O monolayer. Most interestingly, half metalicity has been predicted for Au{sub 2}-Nmore » and Au{sub 2}-F monolayers. Our findings may have importance for the application of these monolayers in nanoelectronic and spintronics.« less

Performance Characterization, Development, and Application of Artificial Potential Function Guidance Methods

DTIC Science & Technology

2014-03-01

to determine if a system is stabilizable with feedback. 12 that asymptotic stability is guaranteed by Lyapunov theory. The advantage of this method are...discretized dynamics are a sufficient representation of the continuous system . Given these assumptions, the optimal control problem for minimum transit time is...tion (APF) guidance performance when applied to systems with limited control au- thority in a dynamic environment and then to use the findings to

Fabrication of Plasmonic Nanorod-Embedded Dipeptide Microspheres via the Freeze-Quenching Method for Near-Infrared Laser-Triggered Drug-Delivery Applications.

PubMed

Erdogan, Hakan; Yilmaz, Mehmet; Babur, Esra; Duman, Memed; Aydin, Halil M; Demirel, Gokhan

2016-05-09

Control of drug release by an external stimulus may provide remote controllability, low toxicity, and reduced side effects. In this context, varying physical external stimuli, including magnetic and electric fields, ultrasound, light, and pharmacological stimuli, have been employed to control the release rate of drug molecules in a diseased region. However, the design and development of alternative on-demand drug-delivery systems that permit control of the dosage of drug released via an external stimulus are still required. Here, we developed near-infrared laser-activatable microspheres based on Fmoc-diphenylalanine (Phe-Phe) dipeptides and plasmonic gold nanorods (AuNRs) via a simple freeze-quenching approach. These plasmonic nanoparticle-embedded microspheres were then employed as a smart drug-delivery platform for native, continuous, and pulsatile doxorubicin (DOX) release. Remarkable sustained, burst, and on-demand DOX release from the fabricated microspheres were achieved by manipulating the laser exposure time. Our results demonstrate that AuNR-embedded dipeptide microspheres have great potential for controlled drug-delivery systems.

Colloidal Random Terpolymers: Controlling Reactivity Ratios of Colloidal Comonomers via Metal Tipping

DOE PAGES

Pavlopoulos, Nicholas G.; Dubose, Jeffrey T.; Hartnett, Erin D.; ...

2016-07-26

We report on a versatile synthetic m-shell nanoparticles (NPs) in the backbone, along with semiconductor CdSe@CdS nanorod (NR), or tetrapod (TP) side chain groups. A seven-step colloidal total synthesis enabled the synthesis of well-defined colloidal comonomers composed of a dipolar Au@CoNP attached to a single CdSe@CdS NR, or TP, where magnetic dipolar associations between Au@CoNP units promoted the formation of colloidal co- or terpolymers. The key step in this synthesis was the ability to photodeposit a single AuNP tip onto CdSe@CdS NR or TP that enables selective seeding of a dipolar CoNP onto the AuNP seed. In conclusion, we showmore » that the variation of the AuNP size directly controlled the size and dipolar character of the CoNP tip, where the size modulation of the Au and Au@CoNP tips is analogous to control of comonomer reactivity ratios in classical copolymerization processes.« less

Facile synthesis, pharmacokinetic and systemic clearance evaluation, and positron emission tomography cancer imaging of 64Cu-Au alloy nanoclusters

NASA Astrophysics Data System (ADS)

Zhao, Yongfeng; Sultan, Deborah; Detering, Lisa; Luehmann, Hannah; Liu, Yongjian

2014-10-01

Gold nanoparticles have been widely used for oncological applications including diagnosis and therapy. However, the non-specific mononuclear phagocyte system accumulation and potential long-term toxicity have significantly limited clinical translation. One strategy to overcome these shortcomings is to reduce the size of gold nanoparticles to allow renal clearance. Herein, we report the preparation of 64Cu alloyed gold nanoclusters (64CuAuNCs) for in vivo evaluation of pharmacokinetics, systemic clearance, and positron emission tomography (PET) imaging in a mouse prostate cancer model. The facile synthesis in acqueous solution allowed precisely controlled 64Cu incorporation for high radiolabeling specific activity and stability for sensitive and accurate detection. Through surface pegylation with 350 Da polyethylene glycol (PEG), the 64CuAuNCs-PEG350 afforded optimal biodistribution and significant renal and hepatobiliary excretion. PET imaging showed low non-specific tumor uptake, indicating its potential for active targeting of clinically relevant biomarkers in tumor and metastatic organs.Gold nanoparticles have been widely used for oncological applications including diagnosis and therapy. However, the non-specific mononuclear phagocyte system accumulation and potential long-term toxicity have significantly limited clinical translation. One strategy to overcome these shortcomings is to reduce the size of gold nanoparticles to allow renal clearance. Herein, we report the preparation of 64Cu alloyed gold nanoclusters (64CuAuNCs) for in vivo evaluation of pharmacokinetics, systemic clearance, and positron emission tomography (PET) imaging in a mouse prostate cancer model. The facile synthesis in acqueous solution allowed precisely controlled 64Cu incorporation for high radiolabeling specific activity and stability for sensitive and accurate detection. Through surface pegylation with 350 Da polyethylene glycol (PEG), the 64CuAuNCs-PEG350 afforded optimal biodistribution and significant renal and hepatobiliary excretion. PET imaging showed low non-specific tumor uptake, indicating its potential for active targeting of clinically relevant biomarkers in tumor and metastatic organs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04569f

Dextran-encapsulated photoluminescent gold nanoclusters: synthesis and application

NASA Astrophysics Data System (ADS)

Chiu, Wei-Ju; Chen, Wei-Yu; Lai, Hong-Zheng; Wu, Ching-Yi; Chiang, Hsiang-Lin; Chen, Yu-Chie

2014-07-01

Dextrans are widely used as additives in food, pharmaceutical, and cosmetics because of their hydrophilicity, biocompatibility, and low toxicity. These features allow the use of dextrans to modify the surface of nanoparticles to improve cell compatibility for biomedical applications. Additionally, dextran molecules covalently bound with fluorescent dyes are frequently used as tracers in animal studies. These facts show that dextrans are useful compounds for biomedicine-related applications and research. Our aim was to explore a facile way to generate dextran-derived nanoparticles with photoluminescent property for the use in fluorescence imaging of bacteria and cancer cells. Dextran-encapsulated gold nanoclusters (AuNCs@dextran) were generated through a one-pot reaction by stirring dextrans and aqueous tetrachloroauric acid overnight. The generated AuNCs exhibit bright and green photoluminescence under the illumination of an ultraviolet lamp ( λ max = 365 nm), and high cell biocompatibility was found as well. Therefore, the generated AuNCs can be used as fluorescence tracers and nanoprobes. We explored the suitability of AuNCs@dextran as labeling agents for bacteria, such as Staphylococcus aureus and Escherichia coli. After the bacteria were labeled by AuNCs@dextran, they became quite visible under a fluorescence microscope. Additionally, we demonstrated that nanocomposites composed of AuNCs@dextran and silica beads can be readily internalized by cancer cells. The nanocomposites can be readily detected in the cells through their photoluminescence, suggesting possible applications in drug delivery and fluorescence imaging.

Artificial neural network and particle swarm optimization for removal of methyl orange by gold nanoparticles loaded on activated carbon and Tamarisk.

PubMed

Ghaedi, M; Ghaedi, A M; Ansari, A; Mohammadi, F; Vafaei, A

2014-11-11

The influence of variables, namely initial dye concentration, adsorbent dosage (g), stirrer speed (rpm) and contact time (min) on the removal of methyl orange (MO) by gold nanoparticles loaded on activated carbon (Au-NP-AC) and Tamarisk were investigated using multiple linear regression (MLR) and artificial neural network (ANN) and the variables were optimized by partial swarm optimization (PSO). Comparison of the results achieved using proposed models, showed the ANN model was better than the MLR model for prediction of methyl orange removal using Au-NP-AC and Tamarisk. Using the optimal ANN model the coefficient of determination (R2) for the test data set were 0.958 and 0.989; mean squared error (MSE) values were 0.00082 and 0.0006 for Au-NP-AC and Tamarisk adsorbent, respectively. In this study a novel and green approach were reported for the synthesis of gold nanoparticle and activated carbon by Tamarisk. This material was characterized using different techniques such as SEM, TEM, XRD and BET. The usability of Au-NP-AC and activated carbon (AC) Tamarisk for the methyl orange from aqueous solutions was investigated. The effect of variables such as pH, initial dye concentration, adsorbent dosage (g) and contact time (min) on methyl orange removal were studied. Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Kinetic models such as pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models indicate that the second-order equation and intraparticle diffusion models control the kinetic of the adsorption process. The small amount of proposed Au-NP-AC and activated carbon (0.015 g and 0.75 g) is applicable for successful removal of methyl orange (>98%) in short time (20 min for Au-NP-AC and 45 min for Tamarisk-AC) with high adsorption capacity 161 mg g(-1) for Au-NP-AC and 3.84 mg g(-1) for Tamarisk-AC. Copyright © 2014 Elsevier B.V. All rights reserved.

Artificial neural network and particle swarm optimization for removal of methyl orange by gold nanoparticles loaded on activated carbon and Tamarisk

NASA Astrophysics Data System (ADS)

Ghaedi, M.; Ghaedi, A. M.; Ansari, A.; Mohammadi, F.; Vafaei, A.

2014-11-01

The influence of variables, namely initial dye concentration, adsorbent dosage (g), stirrer speed (rpm) and contact time (min) on the removal of methyl orange (MO) by gold nanoparticles loaded on activated carbon (Au-NP-AC) and Tamarisk were investigated using multiple linear regression (MLR) and artificial neural network (ANN) and the variables were optimized by partial swarm optimization (PSO). Comparison of the results achieved using proposed models, showed the ANN model was better than the MLR model for prediction of methyl orange removal using Au-NP-AC and Tamarisk. Using the optimal ANN model the coefficient of determination (R2) for the test data set were 0.958 and 0.989; mean squared error (MSE) values were 0.00082 and 0.0006 for Au-NP-AC and Tamarisk adsorbent, respectively. In this study a novel and green approach were reported for the synthesis of gold nanoparticle and activated carbon by Tamarisk. This material was characterized using different techniques such as SEM, TEM, XRD and BET. The usability of Au-NP-AC and activated carbon (AC) Tamarisk for the methyl orange from aqueous solutions was investigated. The effect of variables such as pH, initial dye concentration, adsorbent dosage (g) and contact time (min) on methyl orange removal were studied. Fitting the experimental equilibrium data to various isotherm models such as Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich models show the suitability and applicability of the Langmuir model. Kinetic models such as pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models indicate that the second-order equation and intraparticle diffusion models control the kinetic of the adsorption process. The small amount of proposed Au-NP-AC and activated carbon (0.015 g and 0.75 g) is applicable for successful removal of methyl orange (>98%) in short time (20 min for Au-NP-AC and 45 min for Tamarisk-AC) with high adsorption capacity 161 mg g-1 for Au-NP-AC and 3.84 mg g-1 for Tamarisk-AC.

Flexible Conformable Clamps for a Machining Cell with Applications to Turbine Blade Machining.

DTIC Science & Technology

1983-05-01

PERIOD COVERED * FLEXIBLE CONFORMABLE CLAMPS FOR A MACHINING CELL Interim WITH APPLICATIONS TO TURBINE BLADE MACHINING 6. PERFORMING ORG. REPORT NUMBER...7. AuTmbR(s) 6. CONTRACT OR GRANT NUMBER(a) Eiki Kurokawa 3. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELE%4NTPROJECT. TASK Carnegie-Mellon...University AREA a WORK UhIT NUMBERS The Robotics Institute Pittsburgh, PA. 15213 II. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE May 1983. 13

Dewetting process of Au films on SiO2 nanowires: Activation energy evaluation

NASA Astrophysics Data System (ADS)

Ruffino, F.; Grimaldi, M. G.

2015-05-01

SiO2 nanowires gain scientific and technological interest in application fields ranging from nano-electronics, optics and photonics to bio-sensing. Furthermore, the SiO2 nanowires chemical and physical properties, and so their performances in devices, can be enhanced if decorated by metal nanoparticles (such Au) due to local plasmonic effects. In the present paper, we propose a simple, low-cost and high-throughput three-steps methodology for the mass-production of Au nanoparticles coated SiO2 nanowires. It is based on (1) production of the SiO2 nanowires on Si surface by solid state reaction of an Au film with the Si substrate at high temperature; (2) sputtering deposition of Au on the SiO2 nanowires to obtain the nanowires coated by an Au film; and (3) furnace annealing processes to induce the Au film dewetting on the SiO2 nanowires surface. Using scanning electron microscopy analyses, we followed the change of the Au nanoparticles mean versus the annealing time extracting values for the characteristic activation energy of the dewetting process of the Au film on the SiO2 nanowires surface. Such a study can allow the tuning of the nanowires/nanoparticles sizes for desired technological applications.

Highly active surface-enhanced Raman scattering (SERS) substrates based on gold nanoparticles infiltrated into SiO2 inverse opals

NASA Astrophysics Data System (ADS)

Ankudze, Bright; Philip, Anish; Pakkanen, Tuula T.; Matikainen, Antti; Vahimaa, Pasi

2016-11-01

SiO2 inverse opal (IO) films with embedded gold nanoparticles (AuNPs) for surface-enhanced Raman scattering (SERS) application are reported. SiO2 IO films were loaded with AuNPs by a simple infiltration in a single cycle to form Au-SiO2 IOs. The optical property and the morphology of the Au-SiO2 IO substrates were characterized; it was observed that they retained the Bragg diffraction of SiO2 IO and the localized surface plasmon resonance (LSPR) of AuNPs. The SERS property of the Au-SiO2 IO substrates were studied with methylene blue (MB) and 4-aminothiophenol (4-ATP). The SERS enhancement factors were 107 and 106 for 4-ATP and MB, respectively. A low detection limit of 10-10 M for 4-ATP was also obtained with the Au-SiO2 IO substrate. A relative standard deviation of 18.5% for the Raman signals intensity at 1077 cm-1 for 4-ATP shows that the Au-SiO2 IO substrates have good signal reproducibility. The results of this study indicate that the Au-SiO2 IO substrates can be used in sensing and SERS applications.

Mechanical behavior of a ceramic matrix composite material. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Grosskopf, Paul P.; Duke, John C., Jr.

1991-01-01

Monolithic ceramic materials have been used in industry for hundreds of years. These materials have proven their usefulness in many applications, yet, their potential for critical structural applications is limited. The existence of an imperfection in a monolithic ceramic on the order of several microns in size may be critical, resulting in catastrophic failure. To overcome this extreme sensitivity to small material imperfections, reinforced ceramic materials were developed. A ceramic matrix which has been reinforced with continuous fibers is not only less sensitive to microscopic flaws, but is also able to sustain significant damage without suffering catastrophic failure. A borosilicate glass reinforced with several layers of plain weave silicon carbide cloth (Nicalon) was studied. The mechanical testing which was performed included both flexural and tensile loading configurations. This testing was done not only to determine the material properties, but also to initiate a controlled amount of damage within each specimen. Several nondestructive testing techniques, including acousto-ultrasonics (AU), were performed on the specimens periodically during testing. The AU signals were monitored through the use of an IBM compatible personal computer with a high speed data acquisition board. Software was written which manipulates the AU signals in both the time and frequency domains, resulting in quantitative measures of the mechanical response of the material. The measured AU parameters are compared to both the mechanical test results and data from other nondestructive methods including ultrasonic C-scans and penetrant enhanced x ray radiography.

Label-Free Platform for MicroRNA Detection Based on the Fluorescence Quenching of Positively Charged Gold Nanoparticles to Silver Nanoclusters.

PubMed

Miao, Xiangmin; Cheng, Zhiyuan; Ma, Haiyan; Li, Zongbing; Xue, Ning; Wang, Po

2018-01-16

A novel strategy was developed for microRNA-155 (miRNA-155) detection based on the fluorescence quenching of positively charged gold nanoparticles [(+)AuNPs] to Ag nanoclusters (AgNCs). In the designed system, DNA-stabilized Ag nanoclusters (DNA/AgNCs) were introduced as fluorescent probes, and DNA-RNA heteroduplexes were formed upon the addition of target miRNA-155. Meanwhile, the (+)AuNPs could be electrostatically adsorbed on the negatively charged single-stranded DNA (ssDNA) or DNA-RNA heteroduplexes to quench the fluorescence signal. In the presence of duplex-specific nuclease (DSN), DNA-RNA heteroduplexes became a substrate for the enzymatic hydrolysis of the DNA strand to yield a fluorescence signal due to the diffusion of AgNCs away from (+)AuNPs. Under the optimal conditions, (+)AuNPs displayed very high quenching efficiency to AgNCs, which paved the way for ultrasensitive detection with a low detection limit of 33.4 fM. In particular, the present strategy demonstrated excellent specificity and selectivity toward the detection of target miRNA against control miRNAs, including mutated miRNA-155, miRNA-21, miRNA-141, let-7a, and miRNA-182. Moreover, the practical application value of the system was confirmed by the evaluation of the expression levels of miRNA-155 in clinical serum samples with satisfactory results, suggesting that the proposed sensing platform is promising for applications in disease diagnosis as well as the fundamental research of biochemistry.

Evolution of Excited-State Dynamics in Periodic Au 28, Au 36, Au 44, and Au 52 Nanoclusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Meng; Zeng, Chenjie; Sfeir, Matthew Y.

An understanding of the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. We report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au 28, Au 36, Au 44, and Au 52), which exhibit a set of unique features compared with other similar sized clusters. Molecular-like ultrafast S n → S 1 internal conversions (i.e., radiationless electronic transitions) are observed in the relaxation dynamics of FCC periodic series. Excited-state dynamics with near-HOMO–LUMO gap excitation lacksmore » ultrafast decay component, and only the structural relaxation dominates in the dynamical process, which proves the absence of core–shell relaxation. Interestingly, both the relaxation of the hot carriers and the band-edge carrier recombination become slower as the size increases. The evolution in excited-state properties of this FCC series offers new insight into the structure-dependent properties of metal nanoclusters, which will benefit their optical energy harvesting and photocatalytic applications.« less

Electrogenerated Chemiluminescence Behavior of Au nanoparticles-hybridized Pb (II) metal-organic framework and its application in selective sensing hexavalent chromium.

PubMed

Ma, Hongmin; Li, Xiaojian; Yan, Tao; Li, Yan; Liu, Haiyang; Zhang, Yong; Wu, Dan; Du, Bin; Wei, Qin

2016-02-23

In this work, a novel electrochemiluminescence (ECL) sensor based on Au nanoparticles-hybridized Pb (II)-β-cyclodextrin (Pb-β-CD) metal-organic framework for detecting hexavalent chromium (Cr(VI)) was developed. Pb-β-CD shows excellent ECL behavior and unexpected reducing ability towards Au ions. Au nanoparticles could massively form on the surface of Pb-β-CD (Au@Pb-β-CD) without use of any additional reducing agent. In the presence of coreactant K2S2O8, the ECL emission of Pb-β-CD was enhanced by the formation of Au nanoparticles. Cr(VI) can collisionally quench the ECL behavior of Au@Pb-β-CD/S2O8(2-) system and the detection mechanism was investigated. This ECL sensor is found to have a linear response in the range of 0.01-100 μM and a low detection limit of 3.43 nM (S/N = 3) under the optimal conditions. These results suggest that metal-organic framework Au@Pb-β-CD has great potential in extending the application in the ECL field as an efficient luminophore.

Evolution of Excited-State Dynamics in Periodic Au 28, Au 36, Au 44, and Au 52 Nanoclusters

DOE PAGES

Zhou, Meng; Zeng, Chenjie; Sfeir, Matthew Y.; ...

2017-08-10

An understanding of the correlation between the atomic structure and optical properties of gold nanoclusters is essential for exploration of their functionalities and applications involving light harvesting and electron transfer. We report the femto-nanosecond excited state dynamics of a periodic series of face-centered cubic (FCC) gold nanoclusters (including Au 28, Au 36, Au 44, and Au 52), which exhibit a set of unique features compared with other similar sized clusters. Molecular-like ultrafast S n → S 1 internal conversions (i.e., radiationless electronic transitions) are observed in the relaxation dynamics of FCC periodic series. Excited-state dynamics with near-HOMO–LUMO gap excitation lacksmore » ultrafast decay component, and only the structural relaxation dominates in the dynamical process, which proves the absence of core–shell relaxation. Interestingly, both the relaxation of the hot carriers and the band-edge carrier recombination become slower as the size increases. The evolution in excited-state properties of this FCC series offers new insight into the structure-dependent properties of metal nanoclusters, which will benefit their optical energy harvesting and photocatalytic applications.« less

Technical Evaluation Report on Knowledge Based System Applications for Guidance and Control (Application des Systemes a Base de Connaissances au Guidage-Pilotage),

DTIC Science & Technology

1991-07-01

base de connaissances. Le doniaine de l’intelligence artificieflcs’affirinc en tant que science dont les 6l6mcnts technologiques 6volucnt tr~s...substantiellc de l’cfficacit6 opdrationnellc. Bien que los applications temps riel soient encore relativement rares, un certain nombre de projets de...Sanz-Aranguez SP ProfessorJohn T.Shcpherd UK Dr Elihu Zimet us HOST PAINEL COORDINATOR Mdr Carlos A. Garriga. Lopez SENER Ingenieria y Sistemas SA

Hierarchical Flowerlike Gold Nanoparticles Labeled Immunochromatography Test Strip for Highly Sensitive Detection of Escherichia coli O157:H7.

PubMed

Zhang, Lei; Huang, Youju; Wang, Jingyun; Rong, Yun; Lai, Weihua; Zhang, Jiawei; Chen, Tao

2015-05-19

Gold nanoparticles (AuNPs) labeled lateral-flow test strip immunoassay (LFTS) has been widely used in biomedical, feed/food, and environmental analysis fields. Conventional ILFS assay usually uses spherical AuNPs as labeled probes and shows low detection sensitivity, which further limits its widespread practical application. Unlike spherical AuNP used as labeled probe in conventional ILFS, in our present study, a hierarchical flowerlike AuNP specific probe was designed for LFTS and further used to detect Escherichia coli O157:H7 (E. coli O157:H7). Three types of hierarchical flowerlike AuNPs, such as tipped flowerlike, popcornlike, and large-sized flowerlike AuNPs were synthesized in a one-step method. Compared with other two kinds of Au particles, tipped flowerlike AuNPs probes for LFTS particularly exhibited highly sensitive detection of E. coli O157:H7. The remarkable improvement of detection sensitivity of tipped flowerlike AuNPs probes can be achieved even as low as 10(3) colony-forming units (CFU)/mL by taking advantages of its appropriate size and hierarchical structures, which is superior over the detection performance of conventional LFTS. Using this novel tipped flower AuNPs probes, quantitative detection of E. coli O157:H7 can be obtained partially in a wide concentration range with good repeatability. This hierarchical tipped flower-shaped AuNPs probe for LFTS is promising for the practical applications in widespread analysis fields.

Interaction of Au, Ag, and Bi ions with Ba2YCu3O(7-y) - Implications for superconductor applications

NASA Technical Reports Server (NTRS)

Hepp, A. F.; Gaier, J. R.; Pouch, J. J.; Hambourger, P. D.

1988-01-01

Results are presented on the reactions of Au, Ag, and Bi ions with Ba2YCu3O(7-y) oxides and on the properties of the resultant materials. The results indicate that Au(3+) structural chemistry makes gold an excellent candidate for multiphase structures of the Ba2Y(Cu/1-x/Au/x/)3O(7-y)-type substituted superconductors. Silver is structurally and chemically compatible with the perovskite structure, but when it forms a second phase, it does so without the destruction of the superconducting phase, making silver a useful metal for metal/ceramic applications. On the other hand, bismuth was shown to degrade Tc phase or to form other phases, indicating that it may not be useful in applications with rare-earth-based superconductors.

Non-specific adsorption of complement proteins affects complement activation pathways of gold nanomaterials.

PubMed

Quach, Quang Huy; Kah, James Chen Yong

2017-04-01

The complement system is a key humoral component of innate immunity, serving as the first line of defense against intruders, including foreign synthetic nanomaterials. Although gold nanomaterials (AuNMs) are widely used in nanomedicine, their immunological response is not well understood. Using AuNMs of three shapes commonly used in biomedical applications: spherical gold nanoparticles, gold nanostars and gold nanorods, we demonstrated that AuNMs activated whole complement system, leading to the formation of SC5b-9 complex. All three complement pathways were simultaneously activated by all the AuNMs. Recognition molecules of the complement system interacted with all AuNMs in vitro, except for l-ficolin, but the correlation between these interactions and corresponding complement pathway activation was only observed in the classical and alternative pathways. We also observed the mediating role of complement activation in cellular uptake of all AuNMs by human U937 promonocytic cells, which expresses complement receptors. Taken together, our results highlighted the potential immunological challenges for clinical applications of AuNMs that were often overlooked.

Electrochemical behavior of gold nanoparticles modified nitrogen incorporated tetrahedral amorphous carbon and its application in glucose sensing.

PubMed

Liu, Aiping; Wu, Huaping; Qiu, Xu; Tang, Weihua

2011-12-01

Gold nanoparticles (NPs) with 10-50 nm in diameter were synthesized on nitrogen incorporated tetrahedral amorphous carbon (ta-C:N) thin film electrode by electrodeposition. The deposition and nucleation processes of Au on ta-C:N surface were investigated by cyclic voltammetry and chronoamperometry. The morphology of Au NPs was characterized by scanned electron microscopy. The electrochemical properties of Au NPs modified ta-C:N (ta-C:N/Au) electrode and its ability to sense glucose were investigated by voltammetric and amperometric measurements. The potentiostatic current-time transients showed a progressive nucleation process and diffusion growth of Au on the surface of ta-C:N film according to the Scharifker-Hills model. The Au NPs acted as microelectrodes improved the electron transfer and electrocatalytic oxidation of glucose on ta-C:N electrode. The ta-C:N/Au electrode exhibited fast current response, a linear detection range of glucose from 0.5 to 25 mM and a detection limit of 120 microM, which hinted its potential application as a glucose biosensor.

The fractional laser-induced coagulation zone characterized over time by laser scanning confocal microscopy-A proof of concept study.

PubMed

Banzhaf, Christina A; Lin, Lynlee L; Dang, Nhung; Freeman, Michael; Haedersdal, Merete; Prow, Tarl W

2018-01-01

Ablative fractional laser (AFXL) is an acknowledged technique to increase uptake of topical agents in skin. Micro thermal ablation zones (MAZs) consist of ablated vertical channels surrounded by a coagulation zone (CZ). Laser scanning confocal microscopy (LSCM) images individual MAZs at 733 nm (reflectance confocal microscopy (RCM)). Further, LSCM can image sodium fluorescein (NaF) fluorescence with 488 nm excitation (fluorescence confocal microcopy (FCM)), a small hydrophilic test molecule (370 MW, log P -1.52), which may simulate uptake, bio-distribution and kinetics of small hydrophilic drugs. To explore LSCM for combined investigations of CZ thickness and uptake, bio-distribution and kinetics of NaF in AFXL-exposed skin. Excised human abdominal skin samples were exposed to AFXL (15 mJ/microbeam, 2% density) and NaF gel (1000 μg/ml, 10 μl/cm2) in six repetitions, including untreated control samples. CZ thickness and spatiotemporal fluorescence intensities (FI) were quantified up to four hours after NaF application by RCM and FCM. Test sites were scanned to a depth of 200 μm, quantifying thickness of skin compartments (stratum corneum, epidermis, upper dermis), individual CZ thicknesses and FI in CZ and surrounding skin. RCM images established skin morphology to a depth of 200 μm. The CZ thickness measurements were feasible to a depth of 50 μm, and remained unchanged over time at 50 μm (P > 0.5). FI were detected to a depth of 160 μm and remained constant in CZ up to four hours after NaF application (15 minutes: 79 AU (73-92 AU), 60 minutes: 72 AU (58-82 AU), four hours: 78 AU (71-90 AU), P > 0.1). In surrounding skin, FI increased significantly over time, but remained lower than FI in CZ (15 minutes: 21 AU (17-22 AU), 60 minutes: 21 AU (19-26 AU), four hours: 42 (31- 48 AU), P = 0.03). AFXL-processed skin generated higher FI compared to non-laser processed skin in epidermis and upper dermis at 60 minutes and four hours (P = 0.03). By LSCM, assessment of the AFXL-induced CZ thickness was feasible to a depth of 50 μm, and assessment of FI from a small hydrophilic test molecule, NaF in CZ and surrounding skin feasible to a depth of 160 μm. Lasers Surg. Med. 50:70-77, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Growth of GaN@InGaN Core-Shell and Au-GaN Hybrid Nanostructures for Energy Applications

DOE PAGES

Kuykendall, Tevye; Aloni, Shaul; Jen-La Plante, Ilan; ...

2009-01-01

We demonstrated a method to control the bandgap energy of GaN nanowires by forming GaN@InGaN core-shell hybrid structures using metal organic chemical vapor deposition (MOCVD). Furthermore, we show the growth of Au nanoparticles on the surface of GaN nanowires in solution at room temperature. The work shown here is a first step toward engineering properties that are crucial for the rational design and synthesis of a new class of photocatalytic materials. The hybrid structures were characterized by various techniques, including photoluminescence (PL), energy dispersive x-ray spectroscopy (EDS), transmission and scanning electron microscopy (TEM and SEM), and x-ray diffraction (XRD).

Gold nanoparticle flow sensors designed for dynamic X-ray imaging in biofluids.

PubMed

Ahn, Sungsook; Jung, Sung Yong; Lee, Jin Pyung; Kim, Hae Koo; Lee, Sang Joon

2010-07-27

X-ray-based imaging is one of the most powerful and convenient methods in terms of versatility in applicable energy and high performance in use. Different from conventional nuclear medicine imaging, contrast agents are required in X-ray imaging especially for effectively targeted and molecularly specific functions. Here, in contrast to much reported static accumulation of the contrast agents in targeted organs, dynamic visualization in a living organism is successfully accomplished by the particle-traced X-ray imaging for the first time. Flow phenomena across perforated end walls of xylem vessels in rice are monitored by a gold nanoparticle (AuNP) (approximately 20 nm in diameter) as a flow tracing sensor working in nontransparent biofluids. AuNPs are surface-modified to control the hydrodynamic properties such as hydrodynamic size (DH), zeta-potential, and surface plasmonic properties in aqueous conditions. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray nanoscopy (XN), and X-ray microscopy (XM) are used to correlate the interparticle interactions with X-ray absorption ability. Cluster formation and X-ray contrast ability of the AuNPs are successfully modulated by controlling the interparticle interactions evaluated as flow-tracing sensors.

Simple size-controlled synthesis of Au nanoparticles and their size-dependent catalytic activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suchomel, Petr; Kvitek, Libor; Prucek, Robert

The controlled preparation of Au nanoparticles (NPs) in the size range of 6 to 22 nm is explored in this study. The Au NPs were prepared by the reduction of tetrachloroauric acid using maltose in the presence of nonionic surfactant Tween 80 at various concentrations to control the size of the resulting Au NPs. With increasing concentration of Tween 80 a decrease in the size of produced Au NPs was observed, along with a significant decrease in their size distribution. The size-dependent catalytic activity of the synthesized Au NPs was tested in the reduction of 4-nitrophenol with sodium borohydride, resultingmore » in increasing catalytic activity with decreasing size of the prepared nanoparticles. Eley-Rideal catalytic mechanism emerges as the more probable, in contrary to the Langmuir-Hinshelwood mechanism reported for other noble metal nanocatalysts.« less

Simple size-controlled synthesis of Au nanoparticles and their size-dependent catalytic activity

DOE PAGES

Suchomel, Petr; Kvitek, Libor; Prucek, Robert; ...

2018-03-15

The controlled preparation of Au nanoparticles (NPs) in the size range of 6 to 22 nm is explored in this study. The Au NPs were prepared by the reduction of tetrachloroauric acid using maltose in the presence of nonionic surfactant Tween 80 at various concentrations to control the size of the resulting Au NPs. With increasing concentration of Tween 80 a decrease in the size of produced Au NPs was observed, along with a significant decrease in their size distribution. The size-dependent catalytic activity of the synthesized Au NPs was tested in the reduction of 4-nitrophenol with sodium borohydride, resultingmore » in increasing catalytic activity with decreasing size of the prepared nanoparticles. Eley-Rideal catalytic mechanism emerges as the more probable, in contrary to the Langmuir-Hinshelwood mechanism reported for other noble metal nanocatalysts.« less

Lecithin-gold hybrid nanocarriers as efficient and pH selective vehicles for oral delivery of diacerein-In-vitro and in-vivo study.

PubMed

Javed, Ibrahim; Hussain, Syed Zajif; Shahzad, Atif; Khan, Jahanzeb Muhammad; Ur-Rehman, Habib; Rehman, Mubashar; Usman, Faisal; Razi, Muhammad Tahir; Shah, Muhammad Raza; Hussain, Irshad

2016-05-01

We report the synthesis and evaluation of lecithin-gold hybrid nanocarriers for the oral delivery of drugs with improved pharmacokinetics, Au-drug interactive bioactivity and controlled drug releasing behavior at physiological pH inside human body. For this purpose, diacerein, a hydrophobic anti-arthritic drug, was loaded in lecithin NPs (LD NPs), which were further coated by Au NPs either by in-situ production of Au NPs on LD NPs or by employing pre-synthesized Au NPs. All LDAu NPs were found to release drug selectively at the physiological pH of 7.4 and showed 2.5 times increase in the oral bioavailability of diacerein. Pharmacological efficacy was significantly improved i.e., greater than the additive effect of diacerein and Au NPs alone. LDAu NPs started suppressing inflammation at first phase, whereas LD NPs showed activity in the second phase of inflammation. These results indicate the interaction of Au NPs with prostaglandins and histaminic mediators of first phase of carrageenan induced inflammation. Acute toxicity study showed no hepatic damage but the renal toxicity parameters were close to the upper safety limits. Toxicity parameters were dependent on surface engineering of LDAu NPs. Apart from enhancing the oral bioavailability of hydrophobic drugs and improving their anti-inflammatory activity, these hybrid nanocarriers may have potential applications in gold-based photothermal therapy and the tracing of inflammation at atherosclerotic and arthritic site. Copyright © 2016 Elsevier B.V. All rights reserved.

A colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA based on silver nanoclusters and unmodified gold nanoparticles

NASA Astrophysics Data System (ADS)

Qu, Fei; Chen, Zeqiu; You, Jinmao; Song, Cuihua

2018-05-01

Human telomere DNA plays a vital role in genome integrity control and carcinogenesis as an indication for extensive cell proliferation. Herein, silver nanoclusters (Ag NCs) templated by polymer and unmodified gold nanoparticles (Au NPs) are designed as a new colorimetric platform for sensitively differentiating telomere DNA with different lengths, monitoring G-quadruplex and dsDNA. Ag NCs can produce the aggregation of Au NPs, so the color of Au NPs changes to blue and the absorption peak moves to 700 nm. While the telomere DNA can protect Au NPs from aggregation, the color turns to red again and the absorption band blue shift. Benefiting from the obvious color change, we can differentiate the length of telomere DNA by naked eyes. As the length of telomere DNA is longer, the variation of color becomes more noticeable. The detection limits of telomere DNA containing 10, 22, 40, 64 bases are estimated to be 1.41, 1.21, 0.23 and 0.22 nM, respectively. On the other hand, when telomere DNA forms G-quadruplex in the presence of K+, or dsDNA with complementary sequence, both G-quadruplex and dsDNA can protect Au NPs better than the unfolded telomere DNA. Hence, a new colorimetric platform for monitoring structure conversion of DNA is established by Ag NCs-Au NPs system, and to prove this type of application, a selective K+ sensor is developed.

Light-Triggered Release of DNA from Plasmon-Resonant Nanoparticles

NASA Astrophysics Data System (ADS)

Huschka, Ryan

Plasmon-resonant nanoparticle complexes show promising potential for lighttriggered, controllable delivery of deoxyribonucleic acids (DNA) for research and therapeutic purposes. For example, the approach of RNA interference (RNAi) . using antisense DNA or RNA oligonucleotides to silence activity of a specific pathogenic gene transcript and reduce expression of the encoded protein . is very useful in dissecting genetic function and holds promise as a molecular therapeutic. Herein, we investigate the mechanism and probe the in vitro therapeutic potential of DNA light-triggered release from plasmonic nanoparticles. First, we investigate the mechanism of light-triggered release by dehybridizing double-stranded (dsDNA) via laser illumination from two types of nanoparticle substrates: gold (Au) nanoshells and Au nanorods. Both light-triggered and thermally induced releases are distinctly observable from nanoshell-based complexes. Surprisingly, no analogous measurable light-triggered release was observable from nanorod-based complexes below the DNA melting temperature. These results suggest that a nonthermal mechanism may play a role in light-triggered DNA release. Second, we demonstrate the in vitro light-triggered release of molecules noncovalently attached within dsDNA bound to the Au nanoshell surface. DAPI (4',6- diamidino-2-phenylindole), a bright blue fluorescent molecule that binds reversibly to double-stranded DNA, was chosen to visualize this intracellular light-induced release process. Illumination through the cell membrane of the nanoshell-dsDNA-DAPI complexes dehybridizes the DNA and releases the DAPI molecules within living cells. The DAPI molecules diffuse to the nucleus and associate with the cell's endogenous DNA. This work could have future applications towards drug delivery of molecules that associate with dsDNA. Finally, we demonstrate an engineered Au nanoshell (AuNS)-based therapeutic oligonucleotide delivery vehicle, designed to release its cargo on demand upon illumination with a near-infrared (NIR) laser. A poly(L)lysine peptide (PLL) epilayer coated onto the AuNS surface (AuNS-PLL) is used to capture intact, single-stranded antisense DNA oligonucleotide, or alternatively, double-stranded short-interfering RNA (siRNA) molecules. A green fluorescent protein (GFP)-expressing human lung cancer H1299 cell line was used to determine cellular uptake and GFP gene silencing mediated by AuNS-PLL delivery vector. The light-triggered release of oligonucleotides could have broad applications in the study of cellular processes and in the development of intracellular targeted therapies.

Controlling Au Nanorod Dispersion in Thin Film Polymer Blends

NASA Astrophysics Data System (ADS)

Hore, Michael J. A.; Composto, Russell J.

2012-02-01

Dispersion of Au nanorods (Au NRs) in polymer thin films is studied using a combination of experimental and theoretical techniques. Here, we incorporate small volume fractions of polystyrene-functionalized Au NRs (φrod 0.05) into polystyrene (PS) thin films. By controlling the ratio of the brush length (N) to that of the matrix polymers (P), we can selectively obtain dispersed or aggregated Au NR structures in the PS-Au(N):PS(P) films. A dispersion map of these structures allows one to choose N and P to obtain either uniformly dispersed Au NRs or aggregates of closely packed, side-by-side aligned Au NRs. Furthermore, by blending poly(2,6-dimethyl-p-phenylene oxide) (PPO) into the PS films, we demonstrate that the Au nanorod morphology can be further tuned by reducing depletion-attraction forces and promoting miscibility of the Au NRs. These predictable structures ultimately give rise to tunable optical absorption in the films resulting from surface plasmon resonance coupling between the Au NRs. Finally, self-consistent field theoretic (SCFT) calculations for both the PS-Au(N):PS(P) and PS-Au(N):PS(P):PPO systems provide insight into the PS brush structure, and allow us to interpret morphology and optical property results in terms of wet and dry PS brush states.

Synthesis of CO2/N2-triggered reversible stability-controllable poly(2-(diethylamino)ethyl methacrylate)-grafted-AuNPs by surface-initiated atom transfer radical polymerization.

PubMed

Kitayama, Yukiya; Takeuchi, Toshifumi

2014-10-28

CO2/N2-triggered stability-controllable gold nanoparticles (AuNPs) grafted with poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) layers (PDEAEMA-g-AuNPs) were synthesized by the surface-initiated atom transfer radical polymerization of DEAEMA with AuNPs bearing the bis[2-(2-bromoisobutyryloxy)undecyl] layer (grafting from method). Extension of the PDEAEMA chain length increased the stability of the PDEAEMA-g-AuNPs in CO2-bubbled water because of the electrosteric repulsion of the protonated PDEAEMA layer. The chain-length-dependent stability of PDEAEMA-g-AuNPs was confirmed by DLS and UV-vis spectra by using the localized surface plasmon resonance property of the AuNPs, where the extinction wavelength was shifted toward shorter wavelength with increasing PDEAEMA chain length. The reversible stability change with the gas stimuli of CO2/N2 was also successfully demonstrated. Finally, the transfer across the immiscible interface between water and organic solvent was successfully demonstrated by N2-triggered insolubilization of PDEAEMA layer on AuNPs in the aqueous phase, leading to the successful collection of AuNPs using organic solvent from the aqueous phase. Our "grafting from" method of reversible stability-controllable AuNPs can be applied to develop advanced materials such as reusable optical AuNP-based nanosensors because the molecular recognition layer can be constructed by two-step polymerization.

Gold nanoparticles on titanium and interaction with prototype protein.

PubMed

Padmos, J Daniel; Duchesne, Paul; Dunbar, Michael; Zhang, Peng

2010-10-01

Modifying titanium (Ti) implant surfaces with functional proteins can strengthen the interface between prosthesis and bone. A prototype system was developed using gold nanoparticles (AuNPs) to immobilize proteins onto Ti. An electroless (galvanic displacement) deposition method was first used to form AuNPs of controlled size and coverage on commercial Ti foil (giving Ti-AuNPs). Parameters were then modified to create two groups of discs (n = 26) with different average AuNP diameters. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the morphology and surface structure of Ti-AuNPs. To study the interaction of Ti-AuNPs with proteins, Ti discs (n = 8) modified with plain AuNPs and discs (n = 8) modified with thiol (HS--R--COOH)-functionalized AuNPs were treated with lysozyme solution. The amount and activity of the lysozyme on the discs were examined with Micro-BCA and enzymatic assays. Lysozyme was immobilized onto the discs, and the assays showed that the discs with thiol-functionalized AuNPs, discs with bare AuNPs, and Ti controls had average lysozyme adsorptions of 23 x 10(4), 2.3 x 10(4), and 5.7 x 10(4) microg/m2, respectively. The activity assays showed that 21.5, 18.4, and 12.5% of the adsorbed lysozyme was active on the discs with thiol-functionalized AuNPs, discs with bare AuNPs, and Ti controls, respectively. This technique holds promise for binding functional biomolecules to surgical implants, hence possibly creating implant surfaces that react to their local environment. Copyright 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2010.

Ultrathin Au-Alloy Nanowires at the Liquid-Liquid Interface.

PubMed

Chatterjee, Dipanwita; Shetty, Shwetha; Müller-Caspary, Knut; Grieb, Tim; Krause, Florian F; Schowalter, Marco; Rosenauer, Andreas; Ravishankar, Narayanan

2018-03-14

Ultrathin bimetallic nanowires are of importance and interest for applications in electronic devices such as sensors and heterogeneous catalysts. In this work, we have designed a new, highly reproducible and generalized wet chemical method to synthesize uniform and monodispersed Au-based alloy (AuCu, AuPd, and AuPt) nanowires with tunable composition using microwave-assisted reduction at the liquid-liquid interface. These ultrathin alloy nanowires are below 4 nm in diameter and about 2 μm long. Detailed microstructural characterization shows that the wires have an face centred cubic (FCC) crystal structure, and they have low-energy twin-boundary and stacking-fault defects along the growth direction. The wires exhibit remarkable thermal and mechanical stability that is critical for important applications. The alloy wires exhibit excellent electrocatalytic activity for methanol oxidation in an alkaline medium.

Gold nanoparticles enlighten the future of cancer theranostics

PubMed Central

Guo, Jianfeng; Rahme, Kamil; He, Yan; Li, Lin-Lin; Holmes, Justin D; O’Driscoll, Caitriona M

2017-01-01

Development of multifunctional nanomaterials, one of the most interesting and advanced research areas in the field of nanotechnology, is anticipated to revolutionize cancer diagnosis and treatment. Gold nanoparticles (AuNPs) are now being widely utilized in bio-imaging and phototherapy due to their tunable and highly sensitive optical and electronic properties (the surface plasmon resonance). As a new concept, termed “theranostics,” multifunctional AuNPs may contain diagnostic and therapeutic functions that can be integrated into one system, thereby simultaneously facilitating diagnosis and therapy and monitoring therapeutic responses. In this review, the important properties of AuNPs relevant to diagnostic and phototherapeutic applications such as structure, shape, optics, and surface chemistry are described. Barriers for translational development of theranostic AuNPs and recent advances in the application of AuNPs for cancer diagnosis, photothermal, and photodynamic therapy are discussed. PMID:28883725

Active control of methanol carbonylation selectivity over Au/carbon anode by electrochemical potential.

PubMed

Funakawa, Akiyasu; Yamanaka, Ichiro; Otsuka, Kiyoshi

2005-05-12

Electrochemical oxidative carbonylation of methanol was studied over Au supported carbon anode in CO. The major carbonylation products were dimethyl oxalate (DMO) and dimethyl carbonate (DMC). The minor oxidation products were dimethoxy methane (DMM) and methyl formate (MF) from methanol and CO(2). Influences of various reaction conditions were studied on carbonylation activities and selectivities. The selectivities to DMO and DMC can be controlled by the electrochemical potential. Electrocatalysis of Au/carbon anode was studied by cyclic voltammetry (CV), stoichiometric reactions among Au(3+), methanol, and CO, and UV-vis spectra. The Au/carbon anode was characterized by XRD, SEM, and BE images before and after the carbonylation. These experimental facts strongly suggest that transition of oxidation states of Au affects changing of the carbonylation selectivities to DMO and DMC. Au(0) is the active species for the selective DMO formation by direct electrochemical carbonylation at low potentials (<+1.2 V (Ag/AgCl)). On the other hand, Au(3+) is the active spices for the selective DMC formation by indirect electrochemical carbonylation through Au(3+)/Au(+) redox at high potentials (>+1.3 V).

The effects of colorimetric detection of heavy metal ions based on Au nanoparticles (NPs): size and shape—a case of Co2+

NASA Astrophysics Data System (ADS)

Leng, Yumin; He, Junbao; Li, Bo; Xing, Xiaojing; Guo, Yongming; Ye, Liqun; Lu, Zhiwen

2017-09-01

The different sized and shaped Au NPs have intrigued considerable attention, because they possess different surface plasma resonance (SPR) absorption bands and thus result in many colorimetric Au NP-based detection applications. In this article, four different sized and shaped Au NPs of nanodots/rods were prepared and characterized. The as-prepared Au NPs were modified by the negatively charged anions of [SCH2CO2]2- to investigate both the size and shape effects of modified Au NPs on colorimetric detection of Co2+ and the corresponding SPR absorption properties. The different-shaped Au NPs possess different SPR absorption properties. The Au nanorods appeared to be colorimetric sensitive for Co2+ sensing.

Experimental optimization during SERS application

NASA Astrophysics Data System (ADS)

Laha, Ranjit; Das, Gour Mohan; Ranjan, Pranay; Dantham, Venkata Ramanaiah

2018-05-01

The well known surface enhanced Raman scattering (SERS) needs a lot of experimental optimization for its proper implementation. In this report, we demonstrate the efficient SERS using gold nanoparticles (AuNPs) on quartz plate. The AuNPs were prepared by depositing direct current sputtered Au thin film followed by suitable annealing. The parameters varied for getting best SERS effect were 1) Numerical Aperture of Raman objective lens and 2) Sputtering duration of Au film. It was found that AuNPs formed from the Au layer deposited for 40s and Raman objective lens of magnification 50X are the best combination for obtaining efficient SERS effect.

Mechanical Strength and Stability of DNA-modified Gold Nanoparticle Systems

NASA Astrophysics Data System (ADS)

Lam, Letisha McLaughlin

Systems in which gold nanoparticles (AuNPs) are functionalized with DNA have the potential for a broad range of applications in gene regulation therapies, drug delivery, sensing, innovative biomaterials and material templates. The use of DNA-modified gold nanoparticle (AuNP-DNA) systems is driven by their ease of assembly with bottom-up methods as well as the tunability of the systems' mechanical, optical, and electronic properties by exploiting AuNP characteristics and behavior in a multi-particle arrangement. Periodic arrangements of AuNPs precisely distributed through ligated DNA linkers may be assembled and used on relatively large length scales, on the order of hundreds of nanometers, for use in potential nanoscale technologies and applications. However, because of the size and heterogeneous composition of AuNP-DNA systems, their stability under mechanical loading is not well understood or quantified on relevant physical scales for these applications. Hence, a large-scale specialized finite-element predictive approach with a dislocation-density based crystalline plasticity has been used to investigate the mechanical stability of AuNP-DNA-ligand systems with AuNPs within the physical dimensions required for plasmon resonance. The crystalline formulation for the AuNPs accounts for multiple crystalline slip, dislocation-density evolution, lattice rotations, and large inelastic strains. A hypoelastic formulation was used for the DNA and the ligands. The nonlinear finite-element scheme is based on accounting for finite elastic and inelastic strains. These approaches were employed to predict and understand the fundamental scale-dependent microstructural behavior, the evolving heterogeneous microstructure, and localized phenomena that can contribute to failure initiation and instability. Each system was loaded using quasi-static plane strain tension and compression to simulate application loading conditions, and the elastic and inelastic evolutions were analyzed for evidence of mechanical strengthening as well as possible failure modes. To establish a foundation for AuNP-DNA stability analysis, several different two-particle conformations were investigated, including systems with pentagonally twinned AuNPs, systems with circular AuNPs, systems with non-textured and textured cuboctahedron AuNPs with 6 nm DNA, 12 nm DNA, and 18 nm DNA. In general, the analyses indicated that the systems' stability are mainly affected by large stress gradients at AuNP-ligand interfaces, as well as large dislocation-density, normal stresses, and inelastic accumulations in the region adjacent to these interfaces between the AuNPs and the DNA. The predictions also indicate that highly faceted f.c.c. AuNPs with DNA lengths of approximately 6 nm in biaxial loading conditions were found to have the highest strength and overall stability. Furthermore, periodic AuNP-DNA superlattice composites, which mimic the crystallography of f.c.c. atomic lattices, were investigated for mechanical effectiveness as both a composite material and thin film. This investigation analyzed the stress behavior and inelastic evolution of f.c.c. AuNP-DNA superlattice systems with different Au volume fractions, matrix strengths, intrinsic nanoparticle crystallographic orientations and sizes. These analyses were also extended to superlattice f.c.c. composites on a silicon substrate. The results indicate that f.c.c. AuNP-DNA superlattices have a combination of high strength and toughness due to the ductile nature of the nanoparticles in conjunction with the physical properties of the DNA and matrix materials. The superlattice films also exhibited high strengths and toughness, with the limiting factor being the interrelated aspects of film thickness and delamination. These predictions can be used as guidelines for using these composites, superlattices, and thin films as candidates for innovative building blocks for new material systems.

Control over position, orientation, and spacing of arrays of gold nanorods using chemically nanopatterned surfaces and tailored particle-particle-surface interactions.

PubMed

Nepal, Dhriti; Onses, M Serdar; Park, Kyoungweon; Jespersen, Michael; Thode, Christopher J; Nealey, Paul F; Vaia, Richard A

2012-06-26

The synergy of self- and directed-assembly processes and lithography provides intriguing avenues to fabricate translationally ordered nanoparticle arrangements, but currently lacks the robustness necessary to deliver complex spatial organization. Here, we demonstrate that interparticle spacing and local orientation of gold nanorods (AuNR) can be tuned by controlling the Debye length of AuNR in solution and the dimensions of a chemical contrast pattern. Electrostatic and hydrophobic selectivity for AuNR to absorb to patterned regions of poly(2-vinylpyridine) (P2VP) and polystyrene brushes and mats was demonstrated for AuNR functionalized with mercaptopropane sulfonate (MS) and poly(ethylene glycol), respectively. For P2VP patterns of stripes with widths comparable to the length of the AuNR, single- and double-column arrangements of AuNR oriented parallel and perpendicular to the P2VP line were obtained for MS-AuNR. Furthermore, the spacing of the assembled AuNR was uniform along the stripe and related to the ionic strength of the AuNR dispersion. The different AuNR arrangements are consistent with predictions based on maximization of packing of AuNR within the confined strip.

Controlled deposition of palladium nanodendrites on the tips of gold nanorods and their enhanced catalytic activity.

PubMed

Su, Gaoxing; Jiang, Huaqiao; Zhu, Hongyan; Lv, Jing-Jing; Yang, Guohai; Yan, Bing; Zhu, Jun-Jie

2017-08-31

Plasmonic Au-Pd nanostructures have drawn significant attention for use in heterogeneous catalysis. In this study, palladium nanodendrite-tipped gold nanorods (PdND-T-AuNRs) were subjected to a facile fabrication under mild reaction conditions. The palladium amounts on the two tips were tunable. In the preparation of PdND-T-AuNRs, dense capped AuNRs, a low reaction temperature, and suitable stabilizing agents were identified as critical reaction parameters for controlling palladium nanodendrites deposited on both ends of AuNRs. After overgrowth with palladium nanodendrites, the longitudinal surface plasmonic resonance peaks of PdND-T-AuNRs were red-shifted from 810 nm to 980 nm. The electrocatalytic activity of PdND-T-AuNRs for ethanol oxidation was examined, which was a bit weaker than that of cuboid core-shell Au-Pd nanodendrites; however, PdND-T-AuNRs were more stable in ethanol electrooxidation. Moreover, the photocatalytic activity of PdND-T-AuNRs for Suzuki cross-coupling reactions was investigated. At room temperature, nearly 100% yield was obtained under laser irradiation. The results can further enhance our capability of fine-tuning the optical, electronic, and catalytic properties of the bimetallic Au-Pd nanostructures.

LSPR Tuning from 470 to 800 nm and Improved Stability of Au-Ag Nanoparticles Formed by Gold Deposition and Rebuilding in the Presence of Poly(styrenesulfonate).

PubMed

Cathcart, Nicole; Chen, Jennifer I L; Kitaev, Vladimir

2018-01-16

Stability and precise control over functional properties of metal nanoparticles remain a challenge for the realization of prospective applications. Our described process of shell formation and rebuilding can address both these challenges. Template silver nanoparticles (AgNPs) stabilized by poly(styrenesulfonate) are first transformed with gold deposition, after which the resulting shell rebuilds with the replaced silver. The shell formation and rebuilding are accompanied by large shifts in localized surface plasmon resonance (LSPR) peak position, which enables LSPR tuning in a range from 470 to 800 nm. Furthermore, chemical stability of Au-AgNPs is significantly improved compared to AgNPs due to gold stability. Silver templates of different shapes and sizes were demonstrated to transform to AuAg composite NPs to further extend the accessible LSPR range tuning. Stabilization of template AgNPs with poly(styrenesulfonate), in contrast to commonly used poly(vinylpyrrolidone), was found to be a key factor for shell rebuilding. The developed Au-AgNPs were shown to be advantageous for surface plasmon resonance (SPR) detection and surface-enhanced Raman spectroscopy (SERS) owing to their tunable LSPR and enhanced stability.

Retraction: Gold nanoparticles immobilized on electrospun titanium dioxide nanofibers for catalytic reduction of 4-nitrophenol.

PubMed

Cavusoglu, Halit; Buyukbekar, Burak Zafer; Sakalak, Huseyin; Kohsakowski, Sebastian

2017-02-13

This study involves the preparation and catalytic properties of anatase titanium dioxide nanofibers (TiO2 NFs) supported gold nanoparticles (Au NPs) using a model reaction based on the reduction of 4-nitrophenol (NP) into 4-aminophenol (AP) by sodium borohydride (NaBH4). The fabrication of surfactant-free Au NPs was performed using pulsed laser ablation in liquid (PLAL) technique. The TiO2 NFs were fabricated by a combination of electrospinning and calcination process using a solution containing poly(vinyl pyrolidone)(PVP) and titanium isopropoxide. The adsorption efficiency of laser-generated surfactant-free Au NPs to TiO2 NF supports as a function of pH was analyzed. Our results show that the electrostatic interaction mainly controls the adsorption of the nanoparticles. Au NPs/TiO2 NFs composite exhibited good catalytic activity for the reduction of 4-NP to 4-AP. The unique combination of these materials leads to the development of highly efficient catalysts. Our heterostructured nanocatalysts possibly form an efficient path to fabricate various metal NP/metal-oxide supported catalysts. Thus the applications of PLAL-noble metal NPs can widely broaden. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A novel fluorimetric sensing platform for highly sensitive detection of organophosphorus pesticides by using egg white-encapsulated gold nanoclusters.

PubMed

Yan, Xu; Li, Hongxia; Hu, Tianyu; Su, Xingguang

2017-05-15

Assays for organophosphorus pesticides (OPs) with high sensitivity as well as on-site screening have been urgently required to protect ecosystem and prevent disease. Herein, a novel fluorimetric sensing platform was constructed for quantitative detection of OPs via tyrosinase (TYR) enzyme-controlled quenching of gold nanoclusters (AuNCs). One-step green synthetic approach was developed for the synthesis of AuNCs by using chicken egg white (CEW) as template and stabilizer. Initially, TYR can catalyze the oxidation of dopamine to dopaminechrome, which can efficiently quench the fluorescence intensity of AuNCs at 630nm based on dynamic quenching process. However, with the presence of OPs, the activity of TYR was inhibited, resulting in the fluorescence recovery of AuNCs. This proposed fluorescence platform was demonstrated to enable rapid detection for OPs (paraoxon as model) and to provide excellent sensitivity with a detection limit of 0.1ngmL -1 . Significantly, the fluorescence probe was used to prepare paper-based test strips for visual detection of OPs, which validated the excellent potential for real-time and on-site application. Copyright © 2016 Elsevier B.V. All rights reserved.

Realization of improved metallization-Ti/Al/Ti/W/Au ohmic contacts to n-GaN for high temperature application

NASA Astrophysics Data System (ADS)

Motayed, A.; Davydov, A. V.; Boettinger, W. J.; Josell, D.; Shapiro, A. J.; Levin, I.; Zheleva, T.; Harris, G. L.

2005-05-01

Tungsten metal layer was used for the first time as an effective diffusion barrier for the standard Ti/Al/Ti/Au ohmic metallization scheme to obtain thermally stable ohmic contact suitable for high temperature applications. Comparative studies were performed on three distinct metallization schemes: 1) standard GaN/Ti/Al/Ti/Au, 2) GaN/Ti/Al/W/Au, and 3) GaN/Ti/Al/Ti/W/Au. For the GaN with doping level of 5 × 1017 cm-3, the lowest specific contact resistance for the Ti/Al/Ti/W/Au metallization scheme annealed in argon at 750 °C for 30 sec was 5 × 10-6 .cm2, which is comparable to the standard Ti/Al/Ti/Au scheme. X-ray diffractions (XRD), auger electron spectroscopy (AES) depth profiling, field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and cross-sectional transmission electron microscopy (TEM) revealed that the Ti/Al/Ti/W/Au metallization has superior morphology and microstructural properties compared to standard Ti/Al/Ti/Au metallizations. Remarkably, this metallization was able to withstand thermal aging at 500 °C for 50 hrs with only marginal morphological and electrical deterioration. These studies revealed that the utilization of a compound diffusion barrier stack, as in the Ti/Al/Ti/W/Au metallization, yields electrically, structurally, and morphologically superior metallizations with exceptional thermal stability.

Green synthesis of gold nanoparticles using chlorogenic acid and their enhanced performance for inflammation.

PubMed

Hwang, Su Jung; Jun, Sang Hui; Park, Yohan; Cha, Song-Hyun; Yoon, Minho; Cho, Seonho; Lee, Hyo-Jong; Park, Youmie

2015-10-01

Here we developed a novel green synthesis method for gold nanoparticles (CGA-AuNPs) using chlorogenic acid (CGA) as reductants without the use of other chemicals and validated the anti-inflammatory efficacy of CGA-AuNPs in vitro and in vivo. The resulting CGA-AuNPs appeared predominantly spherical in shape with an average diameter of 22.25±4.78nm. The crystalline nature of the CGA-AuNPs was confirmed by high-resolution X-ray diffraction and by selected-area electron diffraction analyses. High-resolution liquid chromatography/electrospray ionization mass spectrometry revealed that the caffeic acid moiety of CGA forms quinone structure through a two-electron oxidation causing the reduction of Au(3+) to Au(0). When compared to CGA, CGA-AuNPs exhibited enhanced anti-inflammatory effects on NF-κB-mediated inflammatory network, as well as cell adhesion. Collectively, green synthesis of CGA-AuNPs using bioactive reductants and mechanistic studies based on mass spectrometry may open up new directions in nanomedicine and CGA-AuNPs can be an anti-inflammatory nanomedicine for future applications. Gold nanoparticles (Au NPs) have been shown to be very useful in many applications due to their easy functionalization capability. In this article, the authors demonstrated a novel method for the synthesis of gold nanoparticles using chlorogenic acid (CGA) as reductants. In-vitro experiments also confirmed biological activity of the resultant gold nanoparticles. Further in-vivo studies are awaited. Copyright © 2015 Elsevier Inc. All rights reserved.

Size-dependent tissue kinetics of PEG-coated gold nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Wan-Seob; Department of Toxicological Research, National Institute of Food and Drug Safety Evaluation, Korea Food and Drug Administration, Seoul 122-704; Cho, Minjung

2010-05-15

Gold nanoparticles (AuNPs) can be used in various biomedical applications, however, very little is known about their size-dependent in vivo kinetics. Here, we performed a kinetic study in mice with different sizes of PEG-coated AuNPs. Small AuNPs (4 or 13 nm) showed high levels in blood for 24 h and were cleared by 7 days, whereas large (100 nm) AuNPs were completely cleared by 24 h. All AuNPs in blood re-increased at 3 months, which correlated with organ levels. Levels of small AuNPs were peaked at 7 days in the liver and spleen and at 1 month in the mesentericmore » lymph node, and remained high until 6 months, with slow elimination. In contrast, large AuNPs were taken up rapidly (approx 30 min) into the liver, spleen, and mesenteric lymph nodes with less elimination phase. TEM showed that AuNPs were entrapped in cytoplasmic vesicles and lysosomes of Kupffer cells and macrophages of spleen and mesenteric lymph node. Small AuNPs transiently activated CYP1A1 and 2B, phase I metabolic enzymes, in liver tissues from 24 h to 7 days, which mirrored with elevated gold levels in the liver. Large AuNPs did not affect the metabolic enzymes. Thus, propensity to accumulate in the reticuloendothelial organs and activation of phase I metabolic enzymes, suggest that extensive further studies are needed for practical in vivo applications.« less

Nonenzymatic free-cholesterol detection via a modified highly sensitive macroporous gold electrode with platinum nanoparticles.

PubMed

Lee, Yi-Jae; Park, Jae-Yeong

2010-12-15

A sensitive macroporous Au electrode with a highly rough surface obtained through the use of with Pt nanoparticles (macroporous Au-/nPts) is reported. It has been designed for nonenzymatic free-cholesterol biosensor applications. A macroporous Au-/nPts electrode was fabricated by electroplating Pt nanoparticles onto a coral-like shaped macroporous Au electrode structure. The macroporous Au-/nPts electrode was physically characterized by field emission scanning electron microscopy (FESEM). It was confirmed that the Pt nanoparticles were well deposited on the surface of the macroporous Au electrode. The porosity and window pore size of the macroporous Au electrode were 50% and 100-300 nm, respectively. The electroplated Pt nanoparticle size was approximately 10-20 nm. Electrochemical experiments showed that the macroporous Au-/nPts exhibited a much larger surface activation area (roughness factor (RF)=2024.7) than the macroporous Au electrode (RF=46.07). The macroporous Au-/nPts also presented a much stronger electrocatalytic activity towards cholesterol oxidation than does the macroporous Au electrode. At 0.2 V, the electrode responded linearly up to a 5 mM cholesterol concentration in a neutral media, with a detection limit of 0.015 mM and detection sensitivity of 226.2 μA mM(-1) cm(-2). Meanwhile, interfering species such as ascorbic acid (AA), acetaminophen (AP), and uric acid (UA), were effectively avoided. This novel nonenzymatic detection electrode has strong applications as an electrochemically based cholesterol biosensor. Copyright © 2010 Elsevier B.V. All rights reserved.

Fabrication of bimetallic Cu/Au nanotubes and their sensitive, selective, reproducible and reusable electrochemical sensing of glucose

NASA Astrophysics Data System (ADS)

Tee, Si Yin; Ye, Enyi; Pan, Pei Hua; Lee, Coryl Jing Jun; Hui, Hui Kim; Zhang, Shuang-Yuan; Koh, Leng Duei; Dong, Zhili; Han, Ming-Yong

2015-06-01

Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu+-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au3+ at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other potential interfering species and excellent reproducibility with long-term stability. By introducing gold into copper nanostructures at a low level of 3, 1 and 0.1 mol% relative to the initial copper precursor, a significant electrocatalytic enhancement of the resulting bimetallic Cu/Au nanostructures starts to occur at 1 mol%. Overall, the present fabrication of stable Cu/Au nanostructures offers a promising low-cost platform for sensitive, selective, reproducible and reusable electrochemical sensing of glucose.Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu+-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au3+ at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other potential interfering species and excellent reproducibility with long-term stability. By introducing gold into copper nanostructures at a low level of 3, 1 and 0.1 mol% relative to the initial copper precursor, a significant electrocatalytic enhancement of the resulting bimetallic Cu/Au nanostructures starts to occur at 1 mol%. Overall, the present fabrication of stable Cu/Au nanostructures offers a promising low-cost platform for sensitive, selective, reproducible and reusable electrochemical sensing of glucose. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02399h

A nanocomposite of Au-AgI core/shell dimer as a dual-modality contrast agent for x-ray computed tomography and photoacoustic imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orza, Anamaria; Wu, Hui; Li, Yuancheng

Purpose: To develop a core/shell nanodimer of gold (core) and silver iodine (shell) as a dual-modal contrast-enhancing agent for biomarker targeted x-ray computed tomography (CT) and photoacoustic imaging (PAI) applications. Methods: The gold and silver iodine core/shell nanodimer (Au/AgICSD) was prepared by fusing together components of gold, silver, and iodine. The physicochemical properties of Au/AgICSD were then characterized using different optical and imaging techniques (e.g., HR- transmission electron microscope, scanning transmission electron microscope, x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, Z-potential, and UV-vis). The CT and PAI contrast-enhancing effects were tested and then compared with a clinically used CT contrast agentmore » and Au nanoparticles. To confer biocompatibility and the capability for efficient biomarker targeting, the surface of the Au/AgICSD nanodimer was modified with the amphiphilic diblock polymer and then functionalized with transferrin for targeting transferrin receptor that is overexpressed in various cancer cells. Cytotoxicity of the prepared Au/AgICSD nanodimer was also tested with both normal and cancer cell lines. Results: The characterizations of prepared Au/AgI core/shell nanostructure confirmed the formation of Au/AgICSD nanodimers. Au/AgICSD nanodimer is stable in physiological conditions for in vivo applications. Au/AgICSD nanodimer exhibited higher contrast enhancement in both CT and PAI for dual-modality imaging. Moreover, transferrin functionalized Au/AgICSD nanodimer showed specific binding to the tumor cells that have a high level of expression of the transferrin receptor. Conclusions: The developed Au/AgICSD nanodimer can be used as a potential biomarker targeted dual-modal contrast agent for both or combined CT and PAI molecular imaging.« less

Rational Design of Plasmonic Nanoparticles for Enhanced Cavitation and Cell Perforation.

PubMed

Lachaine, Rémi; Boutopoulos, Christos; Lajoie, Pierre-Yves; Boulais, Étienne; Meunier, Michel

2016-05-11

Metallic nanoparticles are routinely used as nanoscale antenna capable of absorbing and converting photon energy with subwavelength resolution. Many applications, notably in nanomedicine and nanobiotechnology, benefit from the enhanced optical properties of these materials, which can be exploited to image, damage, or destroy targeted cells and subcellular structures with unprecedented precision. Modern inorganic chemistry enables the synthesis of a large library of nanoparticles with an increasing variety of shapes, composition, and optical characteristic. However, identifying and tailoring nanoparticles morphology to specific applications remains challenging and limits the development of efficient nanoplasmonic technologies. In this work, we report a strategy for the rational design of gold plasmonic nanoshells (AuNS) for the efficient ultrafast laser-based nanoscale bubble generation and cell membrane perforation, which constitute one of the most crucial challenges toward the development of effective gene therapy treatments. We design an in silico rational design framework that we use to tune AuNS morphology to simultaneously optimize for the reduction of the cavitation threshold while preserving the particle structural integrity. Our optimization procedure yields optimal AuNS that are slightly detuned compared to their plasmonic resonance conditions with an optical breakdown threshold 30% lower than randomly selected AuNS and 13% lower compared to similarly optimized gold nanoparticles (AuNP). This design strategy is validated using time-resolved bubble spectroscopy, shadowgraphy imaging and electron microscopy that confirm the particle structural integrity and a reduction of 51% of the cavitation threshold relative to optimal AuNP. Rationally designed AuNS are finally used to perforate cancer cells with an efficiency of 61%, using 33% less energy compared to AuNP, which demonstrate that our rational design framework is readily transferable to a cell environment. The methodology developed here thus provides a general strategy for the systematic design of nanoparticles for nanomedical applications and should be broadly applicable to bioimaging and cell nanosurgery.

Computational insights into the concomitant changes of hollow interior evolution in [SbnAunSbn]m (n=3, 4, 5, 6; m= -3, -2, -1, -2) complex

NASA Astrophysics Data System (ADS)

Zhu, Tingting; Ning, Ping; Tang, Lihong; Li, Kai; Bao, Shuangyou; Jin, Xu; Song, Xin; Zhang, Xiuying; Han, Shuang

2017-02-01

A series of novel all-metal sandwich species, [SbnAunSbn]m (n= 3, 4, 5, 6; m= -3, -2, -1, -2), are carefully designed and are systematically investigated in term of structure, bonding nature, stability, and potential application. These results show that [SbnAunSbn]m (n=3, 4, 5, 6; m= -3, -2, -1, -2), have local minimum values on their potential energy surfaces. For the Sb-Sb and Sb-Au bond, they are obviously covalent features, while in Au-Au, there is a typical aurophilic interaction. Furthermore, these species present expected stability owing to the positive dissociation energy, great Egap, ionization potential (IP), aromaticity and perfected mechanical stability. Interestingly, [Sb5Au5Sb5]- and [Sb6Au6Sb6]2- are aromatic, while both [Sb3Au3Sb3]3- and [Sb4Au4Sb4]2- possess conflicting aromaticity. And all the title species hold tube aromaticty and δ aromaticty. prediction The application suggests that the Sb site is favorable for absorbing CO in the units, and [Sb3Au3Sb3]3- is more suitable than others; CO is absorbed by the p-p interaction between the C and Sb atoms.

Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells

NASA Astrophysics Data System (ADS)

Cacha, Brian Joseph Gonda

Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C60/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (Voc) by 160% and short circuit current (Jsc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

Cu2O-directed in situ growth of Au nanoparticles inside HKUST-1 nanocages.

PubMed

Liu, Yongxin; Liu, Ting; Tian, Long; Zhang, Linlin; Yao, Lili; Tan, Taixing; Xu, Jin; Han, Xiaohui; Liu, Dan; Wang, Cheng

2016-12-07

Controllable integration of metal nanoparticles (MNPs) and metal-organic frameworks (MOFs) is attracting considerable attention as the obtained composite materials always show synergistic effects in applications of catalysis, delivery, as well as sensing. Herein, a Cu 2 O-directed in situ growth strategy was developed to integrate Au nanoparticles and HKUST-1. In this strategy, Cu 2 O@HKUST-1 core-shell heterostructures, HKUST-1 nanocages, Cu 2 O@Au@HKUST-1 sandwich core-shell heterostructures and Au@HKUST-1 balls-in-cage heterostructures were successfully synthesized. Cu 2 O@HKUST-1 core-shell heterostructures were synthesized by soaking Cu 2 O nanocrystals in benzene-1,3,5-tricarboxylic acid solution. The well-defined Cu 2 O@HKUST-1 core-shell heterostructures were demonstrated to be dominated by the ratio of Cu 2+ cations to btc 3- ligands in solution during the period of HKUST-1 formation. Cu 2 O@Au@HKUST-1 sandwich core-shell or Au@HKUST-1 balls-in-cage heterostructures were obtained by impregnating HAuCl 4 into Cu 2 O@HKUST-1 core-shell heterostructures. Due to the porosity of HKUST-1 and reducibility of Cu 2 O, HAuCl 4 could pass through the HKUST-1 shell and be reduced by the Cu 2 O core in situ forming Au nanoparticles. Finally, CO oxidation reaction at high temperatures was carried out to assess the catalytic functionality of the obtained composite heterostructures. This strategy can circumvent some drawbacks of the existing approaches for integrating MNPs and MOFs, such as nonselective deposition of MNPs at the outer surface of the MOF matrices, extreme treatment conditions and additional surface modifications.

Wide-range tuning of the surface plasmon resonance of silver/gold core shell and alloyed nanoparticles

NASA Astrophysics Data System (ADS)

Hubenthal, Frank; Ziegler, Torsten; Hendrich, Christian; Träger, Frank

2004-03-01

For many applications like surface enhanced Raman scattering in which the optical field enhancement associated with surface plasmon excitation is exploited, tunability of this collective resonance over a wide range is required. For this purpose we have prepared Ag/Au core shell and Ag/Au alloyed nanoparticles with different shell thicknesses and different percentages of the two metals. The nanoparticles were made by subsequent deposition of Ag and Au atoms on dielectric substrates followed by diffusion and nucleation or heat treatment. Depending on the Au shell thickness the plasmon frequency can be tuned, e.g. from 2.8 eV (442 nm) to 2.1 eV (590 nm). Annealing of the core-shell nanoparticles causes a shift of the resonance frequency to 2.6 eV. Theoretical modelling allows us to attribute this observation to the production of alloyed nanoparticles. Possible application of the Ag/Au nanoparticles will be discussed.

Gold Aerogels: Three-Dimensional Assembly of Nanoparticles and Their Use as Electrocatalytic Interfaces

PubMed Central

2016-01-01

Three-dimensional (3D) porous metal nanostructures have been a long sought-after class of materials due to their collective properties and widespread applications. In this study, we report on a facile and versatile strategy for the formation of Au hydrogel networks involving the dopamine-induced 3D assembly of Au nanoparticles. Following supercritical drying, the resulting Au aerogels exhibit high surface areas and porosity. They are all composed of porous nanowire networks reflecting in their diameters those of the original particles (5–6 nm) via electron microscopy. Furthermore, electrocatalytic tests were carried out in the oxidation of some small molecules with Au aerogels tailored by different functional groups. The beta-cyclodextrin-modified Au aerogel, with a host–guest effect, represents a unique class of porous metal materials of considerable interest and promising applications for electrocatalysis. PMID:26751502

Photo-Modulated Therapeutic Protein Release from a Hydrogel Depot Using Visible Light.

PubMed

Basuki, Johan S; Qie, Fengxiang; Mulet, Xavier; Suryadinata, Randy; Vashi, Aditya V; Peng, Yong Y; Li, Lingli; Hao, Xiaojuan; Tan, Tianwei; Hughes, Timothy C

2017-01-19

The use of biomacromolecular therapeutics has revolutionized disease treatment, but frequent injections are required owing to their short half-life in vivo. Thus there is a need for a drug delivery system that acts as a reservoir and releases the drug remotely "on demand". Here we demonstrate a simple light-triggered local drug delivery system through photo-thermal interactions of polymer-coated gold nanoparticles (AuNPs) inside an agarose hydrogel as therapeutic depot. Localized temperature increase induced by the visible light exposure caused reversible softening of the hydrogel matrix to release the pre-loaded therapeutics. The release profile can be adjusted by AuNPs and agarose concentrations, light intensity and exposure time. Importantly, the biological activity of the released bevacizumab was highly retained. In this study we demonstrate the potential application of this facile AuNPs/hydrogel system for ocular therapeutics delivery through its versatility to release multiple biologics, compatibility to ocular cells and spatiotemporal control using visible light. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photoinduced work function changes by isomerization of a densely packed azobenzene-based SAM on Au: a joint experimental and theoretical study.

PubMed

Crivillers, N; Liscio, A; Di Stasio, F; Van Dyck, C; Osella, S; Cornil, D; Mian, S; Lazzerini, G M; Fenwick, O; Orgiu, E; Reinders, F; Braun, S; Fahlman, M; Mayor, M; Cornil, J; Palermo, V; Cacialli, F; Samorì, P

2011-08-28

Responsive monolayers are key building blocks for future applications in organic and molecular electronics in particular because they hold potential for tuning the physico-chemical properties of interfaces, including their energetics. Here we study a photochromic SAM based on a conjugated azobenzene derivative and its influence on the gold work function (Φ(Au)) when chemisorbed on its surface. In particular we show that the Φ(Au) can be modulated with external stimuli by controlling the azobenzene trans/cis isomerization process. This phenomenon is characterized experimentally by four different techniques, kelvin probe, kelvin probe force microscopy, electroabsorption spectroscopy and ultraviolet photoelectron spectroscopy. The use of different techniques implies exposing the SAM to different measurement conditions and different preparation methods, which, remarkably, do not alter the observed work function change (Φ(trans)-Φ(cis)). Theoretical calculations provided a complementary insight crucial to attain a deeper knowledge on the origin of the work function photo-modulation.

One-step synthesis of large-scale graphene film doped with gold nanoparticles at liquid-air interface for electrochemistry and Raman detection applications.

PubMed

Zhang, Panpan; Huang, Ying; Lu, Xin; Zhang, Siyu; Li, Jingfeng; Wei, Gang; Su, Zhiqiang

2014-07-29

We demonstrated a facile one-step synthesis strategy for the preparation of a large-scale reduced graphene oxide multilayered film doped with gold nanoparticles (RGO/AuNP film) and applied this film as functional nanomaterials for electrochemistry and Raman detection applications. The related applications of the fabricated RGO/AuNP film in electrochemical nonenzymatic H2O2 biosensor, electrochemical oxygen reduction reaction (ORR), and surface-enhanced Raman scattering (SERS) detection were investigated. Electrochemical data indicate that the H2O2 biosensor fabricated by RGO/AuNP film shows a wide linear range, low limitation of detection, high selectivity, and long-term stability. In addition, it was proved that the created RGO/AuNP film also exhibits excellent ORR electrochemical catalysis performance. The created RGO/AuNP film, when serving as SERS biodetection platform, presents outstanding performances in detecting 4-aminothiophenol with an enhancement factor of approximately 5.6 × 10(5) as well as 2-thiouracil sensing with a low concentration to 1 μM. It is expected that this facile strategy for fabricating large-scale graphene film doped with metallic nanoparticles will spark inspirations in preparing functional nanomaterials and further extend their applications in drug delivery, wastewater purification, and bioenergy.

Cation coordination reactions on nanocrystals: surface/interface, doping control and advanced photocatalysis applications (Conference Presentation)

NASA Astrophysics Data System (ADS)

Zhang, Jiatao

2016-10-01

Abstract: Including the shape and size effect, the controllable doping, hetero-composite and surface/interface are the prerequisite of colloidal nanocrystals for exploring their optoelectronic properties, such as fluorescence, plasmon-exciton coupling, efficient electron/hole separation, and enhanced photocatalysis applications. By controlling soft acid-base coordination reactions between cation molecular complexes and colloidal nanocrystals, we showed that chemical thermodynamics could drive nanoscale monocrystalline growth of the semiconductor shell on metal nano-substrates and the substitutional heterovalent doping in semiconductor nanocrystals. We have demonstrated evolution of relative position of Au and II-VI semiconductor in Au-Semi from symmetric to asymmetric configuration, different phosphines initiated morphology engineering, oriented attachment of quantum dots into micrometer nanosheets with synergistic control of surface/interface and doing, which can further lead to fine tuning of plasmon-exciton coupling. Therefore, different hydrogen photocatalytic performance, Plasmon enhanced photocatalysis properties have been achieved further which lead to the fine tuning of plasmon-exciton coupling. Substitutional heterovalent doping here enables the tailoring of optical, electronic properties and photocatalysis applications of semiconductor nanocrystals because of electronic impurities (p-, n-type doping) control. References: (1) J. Gui, J. Zhang*, et al. Angew. Chem. Int. Ed. 2015, 54, 3683. (2) Q. Zhao, J. Zhang*, etc., Adv. Mater. 2014, 26, 1387. (3) J. Liu, Q. Zhao, S. G. Wang*, J. Zhang*, etc., Adv. Mater. 2015, 27-2753-2761. (4) H. Qian, J. Zhang*, etc., NPG Asia Mater. (2015) 7, e152. (5) M. Ji, M. Xu, etc., J. Zhang*, Adv. Mater. 2016, in proof. (6) S. Yu, J. T. Zhang, Y. Tang, M. Ouyang*, Nano Lett. 2015, 15, 6282-6288. (7) J. Zhang, Y. Tang, K. Lee and M. Ouyang*, Science 2010, 327, 1634. (8) J. Zhang, Y. Tang, K. Lee, M. Ouyang*, Nature 2010, 466, 91.

Aptamer functionalized noble metal particles for bioanalytical and biomedical applications

NASA Astrophysics Data System (ADS)

Yasun, Emir

Noble metal particles, especially gold (Au) and silver (Ag) have been exploited in a broad range of biological applications due to their unique intrinsic features that depend on their physical appearance or optoelectronic properties, which can be tuned with the change in the size or shape of those particles. Thus, this tunability enables gold nanoparticles (AuNPs) to be used in biomedical diagnostic and therapeutical applications. In photothermal therapy applications, nanomaterials, which can absorb efficiently in NIR region, are utilized since the healthy tissue or cells can't absorb at this spectral region. Among AuNPs, gold nanorods (AuNRs) are one of the best candidates for hyperthermia therapy of cancer cells with their high absorption cross-sections and tunable absorption maxima in NIR region. When this unique optical property is combined with the specificity against cancer cells utilized by aptamer conjugations, AuNRs become to be one of the most important nanoparticles employed in both cancer cell sensing and therapy. However, one drawback of AuNRs is having the surfactant CTAB on their surface, which can cause nonspecificity and cytotoxicity. In this research, the side effects of CTAB are passivated by BSA modification, where the nonspecificity and cytotoxicity are dramatically decreased prior to the NIR treatment. Recognition of changes in the rare cancer protein abundances can lead the early diagnosis of cancer, so capturing these low abundance proteins has a great significance. In this research, firstly, aptamer conjugated AuNRs were used to capture 1ng of a-thrombin effectively from plasma samples as model system. Then both aptamer conjugated AuNRs and silver microspheres (SMSs) are used to capture the biomarker proteins of a colon cancer cell line, DLD-1. Gold and silver surfaces can easily be modified through thiolate chemistry, compared to the tedious modification steps for the magnetic particles, so more aptamer immobilization can be achieved for AuNRs and SMSs, which can increase the possibility of binding to the target protein. Furthermore, SMSs offer a novel separation method, gravitational separation owing to their heavy nature. In this way, there is no need for an external stimuli to separate the captured proteins and protein isolation can take only seconds.

Corrosion resistance evaluation of Pd-free Ag-Au-Pt-Cu dental alloys.

PubMed

Fujita, Takeshi; Shiraishi, Takanobu; Takuma, Yasuko; Hisatsune, Kunihiro

2011-01-01

The corrosion resistance of nine experimental Pd-free Ag-Au-Pt-Cu dental alloys in a 0.9% NaCl solution was investigated using cyclic voltammetry (CV), optical microscopy, and scanning electron microscopy (SEM). CV measurements revealed that the breakdown potential (E(bd)) and zero current potential (E(zc)) increased with increasing Au/(Au+Ag) atomic ratio. Thus, the Au/(Au+Ag) atomic ratio, but not the Cu content, influenced the corrosion resistance of Ag-Au-Pt-Cu alloys. After the forward scan of CV, both optical and scanning electron microscope images showed that in all the experimental alloys, the matrix phase was corroded but not the second phase. From corrosion resistance viewpoint, the Ag-Au-Pt-Cu alloys seemed to be suitable for clinical application.

Morphological effects on the selectivity of intramolecular versus intermolecular catalytic reaction on Au nanoparticles.

PubMed

Wang, Dan; Sun, Yuanmiao; Sun, Yinghui; Huang, Jing; Liang, Zhiqiang; Li, Shuzhou; Jiang, Lin

2017-06-14

It is hard for metal nanoparticle catalysts to control the selectivity of a catalytic reaction in a simple process. In this work, we obtain active Au nanoparticle catalysts with high selectivity for the hydrogenation reaction of aromatic nitro compounds, by simply employing spine-like Au nanoparticles. The density functional theory (DFT) calculations further elucidate that the morphological effect on thermal selectivity control is an internal key parameter to modulate the nitro hydrogenation process on the surface of Au spines. These results show that controlled morphological effects may play an important role in catalysis reactions of noble metal NPs with high selectivity.

Global transcriptomic analysis of model human cell lines exposed to surface-modified gold nanoparticles: the effect of surface chemistry

NASA Astrophysics Data System (ADS)

Grzincic, E. M.; Yang, J. A.; Drnevich, J.; Falagan-Lotsch, P.; Murphy, C. J.

2015-01-01

Gold nanoparticles (Au NPs) are attractive for biomedical applications not only for their remarkable physical properties, but also for the ease of which their surface chemistry can be manipulated. Many applications involve functionalization of the Au NP surface in order to improve biocompatibility, attach targeting ligands or carry drugs. However, changes in cells exposed to Au NPs of different surface chemistries have been observed, and little is known about how Au NPs and their surface coatings may impact cellular gene expression. The gene expression of two model human cell lines, human dermal fibroblasts (HDF) and prostate cancer cells (PC3) was interrogated by microarray analysis of over 14 000 human genes. The cell lines were exposed to four differently functionalized Au NPs: citrate, poly(allylamine hydrochloride) (PAH), and lipid coatings combined with alkanethiols or PAH. Gene functional annotation categories and weighted gene correlation network analysis were used in order to connect gene expression changes to common cellular functions and to elucidate expression patterns between Au NP samples. Coated Au NPs affect genes implicated in proliferation, angiogenesis, and metabolism in HDF cells, and inflammation, angiogenesis, proliferation apoptosis regulation, survival and invasion in PC3 cells. Subtle changes in surface chemistry, such as the initial net charge, lability of the ligand, and underlying layers greatly influence the degree of expression change and the type of cellular pathway affected.Gold nanoparticles (Au NPs) are attractive for biomedical applications not only for their remarkable physical properties, but also for the ease of which their surface chemistry can be manipulated. Many applications involve functionalization of the Au NP surface in order to improve biocompatibility, attach targeting ligands or carry drugs. However, changes in cells exposed to Au NPs of different surface chemistries have been observed, and little is known about how Au NPs and their surface coatings may impact cellular gene expression. The gene expression of two model human cell lines, human dermal fibroblasts (HDF) and prostate cancer cells (PC3) was interrogated by microarray analysis of over 14 000 human genes. The cell lines were exposed to four differently functionalized Au NPs: citrate, poly(allylamine hydrochloride) (PAH), and lipid coatings combined with alkanethiols or PAH. Gene functional annotation categories and weighted gene correlation network analysis were used in order to connect gene expression changes to common cellular functions and to elucidate expression patterns between Au NP samples. Coated Au NPs affect genes implicated in proliferation, angiogenesis, and metabolism in HDF cells, and inflammation, angiogenesis, proliferation apoptosis regulation, survival and invasion in PC3 cells. Subtle changes in surface chemistry, such as the initial net charge, lability of the ligand, and underlying layers greatly influence the degree of expression change and the type of cellular pathway affected. Electronic supplementary information (ESI) available: UV-Vis spectra of Au NPs, the most significantly changed genes of HDF cells after Au NP incubation under GO accession number GO:0007049 ``cell cycle'', detailed information about the primer/probe sets used for RT-PCR validation of results. See DOI: 10.1039/c4nr05166a

Great improvement in pseudocapacitor properties of nickel hydroxide via simple gold deposition

NASA Astrophysics Data System (ADS)

Kim, Sun-I.; Thiyagarajan, Pradheep; Jang, Ji-Hyun

2014-09-01

In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g-1 at 1 A g-1, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g-1 and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g-1 and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data.In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g-1 at 1 A g-1, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g-1 and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g-1 and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02204a

Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

PubMed

Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

2015-06-18

A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts.

Carbon-Coated Gold Nanorods: A Facile Route to Biocompatible Materials for Photothermal Applications.

PubMed

Kaneti, Yusuf Valentino; Chen, Chuyang; Liu, Minsu; Wang, Xiaochun; Yang, Jia Lin; Taylor, Robert Allen; Jiang, Xuchuan; Yu, Aibing

2015-11-25

Gold nanorods and their core-shell nanocomposites have been widely studied because of their well-defined anisotropy and unique optical properties and applications. This study demonstrates a facile hydrothermal synthesis strategy for generating carbon coating on gold nanorods (AuNRs@C) under mild conditions (<200 °C), where the carbon shell is composed of polymerized sugar molecules (glucose). The structure and composition of the produced core-shell nanocomposites were characterized using advanced microscopic and spectroscopic techniques. The functional properties, particularly the photothermal and biocompatibility properties of the produced AuNRs@C, were quantified to assess their potential in photothermal hyperthermia. These AuNRs@C were tested in vitro (under representative treatment conditions) using near-infrared (NIR) light irradiation. It was found that the AuNRs produced here exhibit exemplary heat generation capability. Temperature changes of 10.5, 9, and 8 °C for AuNRs@C were observed with carbon shell thicknesses of 10, 17, and 25 nm, respectively, at a concentration of 50 μM, after 600 s of irradiation with a laser power of 0.17 W/cm(2). In addition, the synthesized AuNRs@C also exhibit good biocompatibility toward two soft tissue sarcoma cell lines (HT1080, a fibrosarcoma; and GCT, a fibrous histiocytoma). The cell viability study shows that AuNRs@C (at a concentration of <0.1 mg/mL) core-shell particles induce significantly lower cytotoxicity on both HT1080 and GCT cell lines, as compared with cetyltrimethylammonium bromide (CTAB)-capped AuNRs. Furthermore, similar to PEG-modified AuNRs, they are also safe to both HT1080 and GCT cell lines. This biocompatibility results from a surface full of -OH or -COH groups, which are suitable for linking and are nontoxic Therefore, the AuNRs@C represent a viable alternative to PEG-coated AuNRs for facile synthesis and improved photothermal conversion. Overall, these findings open up a new class of carbon-coated nanostructures that are biocompatible and could potentially be employed in a wide range of biomedical applications.

Plasmonic gold nanoparticles modified titania nanotubes for antibacterial application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jinhua; Zhou, Huaijuan; Qian, Shi

Close-packed TiO{sub 2} nanotube arrays are prepared on metallic Ti surface by electrochemical anodization. Subsequently, by magnetron sputtering, Au nanoparticles are coated onto the top sidewall and tube inwall. The Au@TiO{sub 2} systems can effectively kill Staphylococcus aureus and Escherichia coli in darkness due to the existence of Au nanoparticles. On the basis of classical optical theories, the antibacterial mechanism is proposed from the perspective of localized surface plasmon resonance. Respiratory electrons of bacterial membrane transfer to Au nanoparticles and then to TiO{sub 2}, which makes bacteria steadily lose electrons until death. This work provides insights for the better understandingmore » and designing of noble metal nanoparticles-based plasmonic heterostructures for antibacterial application.« less

Cross-linked chitosan aerogel modified with Au: Synthesis, characterization and catalytic application.

PubMed

Keshipour, Sajjad; Mirmasoudi, Seyyedeh Sahra

2018-09-15

Dimercaprol as the chelating agent of Au(III) was loaded on chitosan aerogel. Dimercaprol supported on chitosan aerogel efficiently was complexed with Au(III). The new organometallic compound showed good catalytic activity in the oxidation reaction of some aliphatic alcohols, benzyl alcohol, and ethylbenzene. High conversions and excellent selectivities were obtained in the solvent-free oxidation reactions under mild reaction conditions. Also, turnover numbers were calculated for the oxidation reactions with 203, 134, 308, 282, 392, and 153 for 1-pentanol, 1-octanol, 2-propanol, 2-butanol, benzyl alcohol, and ethylbenzene, respectively. The organometallic compound is applicable as a heterogeneous Au(III) catalyst with high chemical stabilityand recyclability up to 6 times. Copyright © 2018 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katoch, Neha, E-mail: nehakatoch2@gmail.com; Kapoor, Pooja; Sharma, Munish

We report stability and electronic properties of benzene molecule adsorbed on the Au atomic layer within the framework of density function theory (DFT). Horizontal configuration of benzene on the top site of Au monolayer prefers energetically over other studied configurations. On the adsorption of benzene, the ballistic conductance of Au monolayer is found to decrease from 4G{sub 0} to 2G{sub 0} suggesting its applications for the fabrications of organic sensor devices based on the Au atomic layers.

Polarization and angle independent magneto-electric Fano resonance in multilayer hetero-nanoshells

NASA Astrophysics Data System (ADS)

Wang, Wudeng; Xiong, Li; Zheng, Li; Li, Wei; Shi, Ying; Qi, Jianguang

2018-05-01

In this work, we have demonstrated that the Si-SiO2 -Au multilayer hetero-nanoshells can support the polarization and angle independent magneto-electric Fano resonance. Such Fano resonance arises from the direct destructive interference between the orthogonal electric dipole mode of Au core and magnetic dipole mode of the Si shell and is independent of the angle due to the high structural symmetry. In contrast to metal particle arrays, here is a possibility to generate controllable interaction between the electric and magnetic dipole resonances of individual nanoshell with the structural features. The discrete magnetic responses provided directly by the Si shell pave the groundwork for designing the magnetic responses at optical frequencies and enable many fascinating applications in nanophotonics.

Interface Schottky barrier engineering via strain in metal-semiconductor composites

NASA Astrophysics Data System (ADS)

Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

2016-01-01

The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures.The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures. Electronic supplementary information (ESI) available: The changes of Au 5d DOS, valence bands of TiO2, the interfacial bond length and interfacial energy with strain, and the local DOS results for the change of SBH with strain. See DOI: 10.1039/c5nr05583k

Surface-enhanced Raman spectroscopy with Au-nanoparticle substrate fabricated by using femtosecond pulse

NASA Astrophysics Data System (ADS)

Zhang, Wending; Li, Cheng; Gao, Kun; Lu, Fanfan; Liu, Min; Li, Xin; Zhang, Lu; Mao, Dong; Gao, Feng; Huang, Ligang; Mei, Ting; Zhao, Jianlin

2018-05-01

Au-nanoparticle (Au-NP) substrates for surface-enhanced Raman spectroscopy (SERS) were fabricated by grid-like scanning a Au-film using a femtosecond pulse. The Au-NPs were directly deposited on the Au-film surface due to the scanning process. The experimentally obtained Au-NPs presented local surface plasmon resonance effect in the visible spectral range, as verified by finite difference time domain simulations and measured reflection spectrum. The SERS experiment using the Au-NP substrates exhibited high activity and excellent substrate reproducibility and stability, and a clearly present Raman spectra of target analytes, e.g. Rhodamine-6G, Rhodamine-B and Malachite green, with concentrations down to 10‑9 M. This work presents an effective approach to producing Au-NP SERS substrates with advantages in activity, reproducibility and stability, which could be used in a wide variety of practical applications for trace amount detection.

Surface-enhanced Raman spectroscopy with Au-nanoparticle substrate fabricated by using femtosecond pulse.

PubMed

Zhang, Wending; Li, Cheng; Gao, Kun; Lu, Fanfan; Liu, Min; Li, Xin; Zhang, Lu; Mao, Dong; Gao, Feng; Huang, Ligang; Mei, Ting; Zhao, Jianlin

2018-05-18

Au-nanoparticle (Au-NP) substrates for surface-enhanced Raman spectroscopy (SERS) were fabricated by grid-like scanning a Au-film using a femtosecond pulse. The Au-NPs were directly deposited on the Au-film surface due to the scanning process. The experimentally obtained Au-NPs presented local surface plasmon resonance effect in the visible spectral range, as verified by finite difference time domain simulations and measured reflection spectrum. The SERS experiment using the Au-NP substrates exhibited high activity and excellent substrate reproducibility and stability, and a clearly present Raman spectra of target analytes, e.g. Rhodamine-6G, Rhodamine-B and Malachite green, with concentrations down to 10 -9 M. This work presents an effective approach to producing Au-NP SERS substrates with advantages in activity, reproducibility and stability, which could be used in a wide variety of practical applications for trace amount detection.

One pot environmental friendly synthesis of gold nanoparticles using Punica Granatum Juice: A novel antioxidant agent for future dermatological and cosmetic applications.

PubMed

Gubitosa, Jennifer; Rizzi, Vito; Lopedota, Angela; Fini, Paola; Laurenzana, Anna; Fibbi, Gabriella; Fanelli, Fiorenza; Petrella, Andrea; Laquintana, Valentino; Denora, Nunzio; Comparelli, Roberto; Cosma, Pinalysa

2018-07-01

The interesting properties of Gold Nanoparticles (AuNPs) make them attractive for different application fields such as cosmetology, medicine and clinical nanotechnologies. In this work a fast, easy and eco-friendly method for the AuNPs synthesis is proposed by using the Punica Granatum Juice (PGJ) with potential dermatological and cosmetic applications. The AuNPs antioxidant activity, due to the presence of phenols from the juice, and their use as booster for improving the Sun Protection Factor (SPF) in commercial sunscreen formulations, are thus expounded. By using appropriate amounts of PGJ and HAuCl 4 , under mild work conditions, AuNPs with a mean size of 100 ± 40 nm are observed and carefully characterized. Solution pH, temperature, and volume were also changed for optimizing the AuNPs formation and features. The antioxidant activity was studied, by evaluating the AuNP ability of scavenging the radical 2,2-diphenyl-1-picrylhydrazylhydrate (DPPH). This finding was confirmed performing special experiments focused on the reaction between AuNPs and H 2 O 2 , by using suitable probes, such as 4-thiothymidine (S 4 TdR) and Cytochrome-c (Cyt-c). The SPF value was also calculated. The synthetized AuNPs showed a surface plasmon in visible range at 577 nm and resulted stable for long time in aqueous medium, also changing the pH values in the range 2-12. The studied antioxidant activity, confirmed also by performing special experiments with suitable probes, demonstrated the high performance of AuNPs. The AuNP photostability under sun irradiation is also shown. The calculated SPF values were in the range 3-18, related to AuNPs concentration in the range 1.80 × 10 -12 -1.00 × 10 -11  M. The same AuNPs concentrations were used for cellular experiments. Indeed, since the AuNPs-PGJ mediated will be potentially introduced by dermal contact, dermal fibroblasts (Human Dermal Fibroblasts, HDF) and Human Microvascular Endothelial Cells (HMVEC) were used to evaluate the possible effects of these nanoparticles as a preliminary step. The results indicated that an AuNP concentrations in the range 1.80 × 10 -12 -3.60 × 10 -12  M could be adopted since they do not appeared cyctotoxic. Copyright © 2018 Elsevier Inc. All rights reserved.

ALD-Developed Plasmonic Two-Dimensional Au-WO3-TiO2 Heterojunction Architectonics for Design of Photovoltaic Devices.

PubMed

Karbalaei Akbari, Mohammad; Hai, Zhenyin; Wei, Zihan; Detavernier, Christophe; Solano, Eduardo; Verpoort, Francis; Zhuiykov, Serge

2018-03-28

Electrically responsive plasmonic devices, which benefit from the privilege of surface plasmon excited hot carries, have supported fascinating applications in the visible-light-assisted technologies. The properties of plasmonic devices can be tuned by controlling charge transfer. It can be attained by intentional architecturing of the metal-semiconductor (MS) interfaces. In this study, the wafer-scaled fabrication of two-dimensional (2D) TiO 2 semiconductors on the granular Au metal substrate is achieved using the atomic layer deposition (ALD) technique. The ALD-developed 2D MS heterojunctions exhibited substantial enhancement of the photoresponsivity and demonstrated the improvement of response time for 2D Au-TiO 2 -based plasmonic devices under visible light illumination. To circumvent the undesired dark current in the plasmonic devices, a 2D WO 3 nanofilm (∼0.7 nm) was employed as the intermediate layer on the MS interface to develop the metal-insulator-semiconductor (MIS) 2D heterostructure. As a result, 13.4% improvement of the external quantum efficiency was obtained for fabricated 2D Au-WO 3 -TiO 2 heterojunctions. The impedancometry measurements confirmed the modulation of charge transfer at the 2D MS interface using MIS architectonics. Broadband photoresponsivity from the UV to the visible light region was observed for Au-TiO 2 and Au-WO 3 -TiO 2 heterostructures, whereas near-infrared responsivity was not observed. Consequently, considering the versatile nature of the ALD technique, this approach can facilitate the architecturing and design of novel 2D MS and MIS heterojunctions for efficient plasmonic devices.

Ultrathin Au film on polymer surface for surface plasmon polariton waveguide application

NASA Astrophysics Data System (ADS)

Liu, Tong; Ji, Lanting; He, Guobing; Sun, Xiaoqiang; Wang, Fei; Zhang, Daming

2017-11-01

Formation of laterally continuous ultrathin gold films on polymer substrates is a technological challenge. In this work, the vacuum thermal evaporation method is adopted to form continuous Au films in the thickness range of 7-17 nm on polymers of Poly(methyl-methacrylate-glycidly-methacrylate) and SU-8 film surface without using the adhesion or metallic seeding layers. Absorption spectrum, scanning electron microscope and atomic force microscope images are used to characterize the Au film thickness, roughness and optical loss. The result shows that molecular-scale structure, surface energy and electronegativity have impacts on the Au film morphology on polymers. Wet chemical etching is used to fabricate 7-nm thick Au stripes embedded in polymer claddings. These long-range surface plasmon polariton waveguides demonstrate the favorable morphological configurations and cross-sectional states. Through the end-fire excitation method, propagation losses of 6-μm wide Au stripes are compared to theoretical values and analyzed from practical film status. The smooth, patternable gold films on polymer provide potential applications to plasmonic waveguides, biosensing, metamaterials and optical antennas.

Gold Nanocages for Biomedical Applications**

PubMed Central

Skrabalak, Sara E.; Chen, Jingyi; Au, Leslie; Lu, Xianmao; Li, Xingde; Xia, Younan

2008-01-01

Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl4. The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where the optical attenuation caused by blood and soft tissue is essentially negligible. They are also biocompatible and present a well-established surface for easy functionalization. We have tailored the scattering and absorption cross-sections of Au nanocages for use in optical coherence tomography and photothermal treatment, respectively. Our preliminary studies show greatly improved spectroscopic image contrast for tissue phantoms containing Au nanocages. Our most recent results also demonstrate the photothermal destruction of breast cancer cells in vitro by using immuno-targeted Au nanocages as an effective photo-thermal transducer. These experiments suggest that Au nanocages may be a new class of nanometer-sized agents for cancer diagnosis and therapy. PMID:18648528

Gold nanoparticle contrast agents in advanced X-ray imaging technologies.

PubMed

Ahn, Sungsook; Jung, Sung Yong; Lee, Sang Joon

2013-05-17

Recently, there has been significant progress in the field of soft- and hard-X-ray imaging for a wide range of applications, both technically and scientifically, via developments in sources, optics and imaging methodologies. While one community is pursuing extensive applications of available X-ray tools, others are investigating improvements in techniques, including new optics, higher spatial resolutions and brighter compact sources. For increased image quality and more exquisite investigation on characteristic biological phenomena, contrast agents have been employed extensively in imaging technologies. Heavy metal nanoparticles are excellent absorbers of X-rays and can offer excellent improvements in medical diagnosis and X-ray imaging. In this context, the role of gold (Au) is important for advanced X-ray imaging applications. Au has a long-history in a wide range of medical applications and exhibits characteristic interactions with X-rays. Therefore, Au can offer a particular advantage as a tracer and a contrast enhancer in X-ray imaging technologies by sensing the variation in X-ray attenuation in a given sample volume. This review summarizes basic understanding on X-ray imaging from device set-up to technologies. Then this review covers recent studies in the development of X-ray imaging techniques utilizing gold nanoparticles (AuNPs) and their relevant applications, including two- and three-dimensional biological imaging, dynamical processes in a living system, single cell-based imaging and quantitative analysis of circulatory systems and so on. In addition to conventional medical applications, various novel research areas have been developed and are expected to be further developed through AuNP-based X-ray imaging technologies.

Synthesis and electrocatalytic activity of Au/Pt bimetallic nanodendrites for ethanol oxidation in alkaline medium.

PubMed

Han, Xinyi; Wang, Dawei; Liu, Dong; Huang, Jianshe; You, Tianyan

2012-02-01

Gold/Platinum (Au/Pt) bimetallic nanodendrites were successfully synthesized through seeded growth method using preformed Au nanodendrites as seeds and ascorbic acid as reductant. Cyclic voltammograms (CVs) of a series of Au/Pt nanodendrites modified electrodes in 1M KOH solution containing 1M ethanol showed that the electrocatalyst with a molar ratio (Au:Pt) of 3 exhibited the highest peak current density and the lowest onset potential. The peak current density of ethanol electro-oxidation on the Au(3)Pt(1) nanodendrites modified glassy carbon electrode (Au(3)Pt(1) electrode) is about 16, 12.5, and 4.5 times higher than those on the polycrystalline Pt electrode, polycrystalline Au electrode, and Au nanodendrites modified glassy carbon electrode (Au dendrites electrode), respectively. The oxidation peak potential of ethanol electro-oxidation on the Au(3)Pt(1) electrode is about 299 and 276 mV lower than those on the polycrystalline Au electrode and Au dendrites electrode, respectively. These results demonstrated that the Au/Pt bimetallic nanodendrites may find potential application in alkaline direct ethanol fuel cells (ADEFCs). Copyright © 2011 Elsevier Inc. All rights reserved.

Controlling the Nanoscale Patterning of AuNPs on Silicon Surfaces

PubMed Central

Williams, Sophie E.; Davies, Philip R.; Bowen, Jenna L.; Allender, Chris J.

2013-01-01

This study evaluates the effectiveness of vapour-phase deposition for creating sub-monolayer coverage of aminopropyl triethoxysilane (APTES) on silicon in order to exert control over subsequent gold nanoparticle deposition. Surface coverage was evaluated indirectly by observing the extent to which gold nanoparticles (AuNPs) deposited onto the modified silicon surface. By varying the distance of the silicon wafer from the APTES source and concentration of APTES in the evaporating media, control over subsequent gold nanoparticle deposition was achievable to an extent. Fine control over AuNP deposition (AuNPs/μm2) however, was best achieved by adjusting the ionic concentration of the AuNP-depositing solution. Furthermore it was demonstrated that although APTES was fully removed from the silicon surface following four hours incubation in water, the gold nanoparticle-amino surface complex was stable under the same conditions. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to study these affects. PMID:28348330

Gold Nanoparticles Stabilized with MPEG-Grafted Poly(l-lysine): in Vitro and in Vivo Evaluation of a Potential Theranostic Agent

PubMed Central

2015-01-01

As the number of diagnostic and therapeutic applications utilizing gold nanoparticles (AuNPs) increases, so does the need for AuNPs that are stable in vivo, biocompatible, and suitable for bioconjugation. We investigated a strategy for AuNP stabilization that uses methoxypolyethylene glycol-graft-poly(l-lysine) copolymer (MPEG-gPLL) bearing free amino groups as a stabilizing molecule. MPEG-gPLL injected into water solutions of HAuCl4 with or without trisodium citrate resulted in spherical (Zav = 36 nm), monodisperse (PDI = 0.27), weakly positively charged nanoparticles (AuNP3) with electron-dense cores (diameter: 10.4 ± 2.5 nm) and surface amino groups that were amenable to covalent modification. The AuNP3 were stable against aggregation in the presence of phosphate and serum proteins and remained dispersed after their uptake into endosomes. MPEG-gPLL-stabilized AuNP3 exhibited high uptake and very low toxicity in human endothelial cells, but showed a high dose-dependent toxicity in epithelioid cancer cells. Highly stable radioactive labeling of AuNP3 with 99mTc allowed imaging of AuNP3 biodistribution and revealed dose-dependent long circulation in the blood. The minor fraction of AuGNP3 was found in major organs and at sites of experimentally induced inflammation. Gold analysis showed evidence of a partial degradation of the MPEG-gPLL layer in AuNP3 particles accumulated in major organs. Radiofrequency-mediated heating of AuNP3 solutions showed that AuNP3 exhibited heating behavior consistent with 10 nm core nanoparticles. We conclude that PEG-pPLL coating of AuNPs confers “stealth” properties that enable these particles to exist in vivo in a nonaggregating, biocompatible state making them suitable for potential use in biomedical applications such as noninvasive radiofrequency cancer therapy. PMID:25496453

Solubility of gold in oxidized, sulfur-bearing fluids at 500-850 °C and 200-230 MPa: A synthetic fluid inclusion study

NASA Astrophysics Data System (ADS)

Guo, Haihao; Audétat, Andreas; Dolejš, David

2018-02-01

Although Au solubility in magmatic-hydrothermal fluids has been investigated by numerous previous studies, there is a dearth of data on oxidized (log fO2 > FMQ+2.5; FMQ - fayalite-magnetite-quartz buffer), sulfur-bearing fluids such as those that formed porphyry Cu-Au (-Mo) deposits. We performed experiments to constrain the effects of fluid salinity, HCl content, sulfur content, fO2 and temperature on Au solubility in such oxidized, sulfur-bearing fluids. For this purpose, small aliquots of fluids equilibrated with Au metal were trapped at high pressure and temperature in the form of synthetic fluid inclusions in quartz and were subsequently analyzed by LA-ICP-MS. Additionally, Raman spectra were collected from quartz-hosted fluid inclusions at up to 600 °C to help to identify the nature of dissolved gold and sulfur species. Gold solubility was found to be affected most strongly by the HCl content of the fluid, followed by fO2, fluid salinity and temperature. Compared to these factors the sulfur content of the fluid has relatively little influence. At 600 °C and 100 MPa, fluids with geologically realistic HCl contents (∼1.1 wt%) and salinities (7-50 wt% NaClequiv) dissolve ∼1000-3000 ppm Au at oxygen fugacities controlled by the magnetite-hematite buffer. At even more oxidized conditions (three log units above the hematite-magnetite fO2 buffer), HCl-, NaCl- and H2SO4-rich fluids can dissolve up to 5 wt% Au at 800 °C and 200 MPa. The observed Au solubility trends are controlled by HCl0 species in the Na-H-Cl-SO4 fluid and are quantitatively reproduced by existing thermodynamic data for Au-Cl complexes. In all experiments, AuCl0 and AuCl2- species are predicted to occur in comparable although variable concentrations, and account for more than 95% of Au solutes. Natural, high-temperature (>500 °C) brine inclusions from porphyry Cu-Au (-Mo) deposits contain significantly less Au than gold-saturated brines that were synthesized experimentally, implying that the natural brines were Au-undersaturated. Consequently, gold grades in Au-rich porphyries were not controlled by the precipitation of native Au, but rather by factors that caused the precipitation of Au-bearing hydrothermal sulfides such as bornite.

Direct colorimetric detection of unamplified pathogen DNA by dextrin-capped gold nanoparticles.

PubMed

Baetsen-Young, Amy M; Vasher, Matthew; Matta, Leann L; Colgan, Phil; Alocilja, Evangelyn C; Day, Brad

2018-03-15

The interaction between gold nanoparticles (AuNPs) and nucleic acids has facilitated a variety of diagnostic applications, with further diversification of synthesis match bio-applications while reducing biotoxicity. However, DNA interactions with unique surface capping agents have not been fully defined. Using dextrin-capped AuNPs (d-AuNPs), we have developed a novel unamplified genomic DNA (gDNA) nanosensor, exploiting dispersion and aggregation characteristics of d-AuNPs, in the presence of gDNA, for sequence-specific detection. We demonstrate that d-AuNPs are stable in a five-fold greater salt concentration than citrate-capped AuNPs and the d-AuNPs were stabilized by single stranded DNA probe (ssDNAp). However, in the elevated salt concentrations of the DNA detection assay, the target reactions were surprisingly further stabilized by the formation of a ssDNAp-target gDNA complex. The results presented herein lead us to propose a mechanism whereby genomic ssDNA secondary structure formation during ssDNAp-to-target gDNA binding enables d-AuNP stabilization in elevated ionic environments. Using the assay described herein, we were successful in detecting as little as 2.94 fM of pathogen DNA, and using crude extractions of a pathogen matrix, as few as 18 spores/µL. Copyright © 2017 Elsevier B.V. All rights reserved.

Gold core/Ceria shell-based redox active nanozyme mimicking the biological multienzyme complex phenomenon

DOE PAGES

Bhagat, Stuti; Srikanth Vallabani, NV; Shutthanandan, Vaithiyalingam; ...

2017-12-02

Catalytically active individual gold (Au) and cerium oxide (CeO 2) nanoparticles (NPs) are well known to exhibit specific enzyme-like activities, such as natural catalase, oxidase, superoxide dismutase, and peroxidase enzymes. Our activities have been maneuvered to design several biological applications such as immunoassays, glucose detection, radiation and free radical protection and tissue engineering. In biological systems, multienzyme complexes are involved in catalyzing important reactions of essential metabolic processes such as respiration, biomolecule synthesis, and photosynthesis. It is well known that metabolic processes linked with multienzyme complexes offer several advantages over reactions catalyzed by individual enzymes. A functional nanozyme depicting multienzymemore » like properties has eluded the researchers in the nanoscience community for the past few decades. Here, we have designed a functional multienzyme in the form of Gold (core)-CeO 2 (shell) nanoparticles (Au/CeO 2 CSNPs) exhibiting excellent peroxidase, catalase, and superoxide dismutase enzyme-like activities that are controlled simply by tuning the pH. The reaction kinetic parameters reveal that the peroxidase-like activity of this core-shell nanozyme is comparable to natural horseradish peroxidase (HRP) enzyme. Unlike peroxidase-like activity exhibited by other nanomaterials, Au/CeO 2 CSNPs showed a decrease in hydroxyl radical formation, suggesting that the biocatalytic reactions are performed by efficient electron transfers. A significant enzyme-like activity of this core-shell nanoparticle was conserved at extreme pH (2 – 11) and temperatures (up to 90 °C), clearly suggesting the superiority over natural enzymes. Further, the utility of peroxidase-like activity of this core-shell nanoparticles was extended for the detection of glucose, which showed a linear range of detection between (100 µM – 1 mM). It is hypothesized that the proximity of the redox potentials of Au+/Au and Ce (III)/Ce (IV) may result in a redox couple promoting the multienzyme activity of core-shell nanoparticles. Au/CeO 2 CSNPs may open new directions for development of single platform sensors in multiple biosensing applications.« less

Gold core/Ceria shell-based redox active nanozyme mimicking the biological multienzyme complex phenomenon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhagat, Stuti; Srikanth Vallabani, NV; Shutthanandan, Vaithiyalingam

Catalytically active individual gold (Au) and cerium oxide (CeO 2) nanoparticles (NPs) are well known to exhibit specific enzyme-like activities, such as natural catalase, oxidase, superoxide dismutase, and peroxidase enzymes. Our activities have been maneuvered to design several biological applications such as immunoassays, glucose detection, radiation and free radical protection and tissue engineering. In biological systems, multienzyme complexes are involved in catalyzing important reactions of essential metabolic processes such as respiration, biomolecule synthesis, and photosynthesis. It is well known that metabolic processes linked with multienzyme complexes offer several advantages over reactions catalyzed by individual enzymes. A functional nanozyme depicting multienzymemore » like properties has eluded the researchers in the nanoscience community for the past few decades. Here, we have designed a functional multienzyme in the form of Gold (core)-CeO 2 (shell) nanoparticles (Au/CeO 2 CSNPs) exhibiting excellent peroxidase, catalase, and superoxide dismutase enzyme-like activities that are controlled simply by tuning the pH. The reaction kinetic parameters reveal that the peroxidase-like activity of this core-shell nanozyme is comparable to natural horseradish peroxidase (HRP) enzyme. Unlike peroxidase-like activity exhibited by other nanomaterials, Au/CeO 2 CSNPs showed a decrease in hydroxyl radical formation, suggesting that the biocatalytic reactions are performed by efficient electron transfers. A significant enzyme-like activity of this core-shell nanoparticle was conserved at extreme pH (2 – 11) and temperatures (up to 90 °C), clearly suggesting the superiority over natural enzymes. Further, the utility of peroxidase-like activity of this core-shell nanoparticles was extended for the detection of glucose, which showed a linear range of detection between (100 µM – 1 mM). It is hypothesized that the proximity of the redox potentials of Au+/Au and Ce (III)/Ce (IV) may result in a redox couple promoting the multienzyme activity of core-shell nanoparticles. Au/CeO 2 CSNPs may open new directions for development of single platform sensors in multiple biosensing applications.« less

Light controllable catalytic activity of Au clusters decorated with photochromic molecules.

PubMed

Guo, Na; Yam, Kah Meng; Zhang, Chun

2018-06-15

By ab initio calculations, we show that when decorated with a photochromic molecule, the catalytic activity of an Au nanocluster can be reversibly controlled by light. The combination of a photochromic thiol-pentacarbonyl azobenzene (TPA) molecule and an Au 8 cluster is chosen as a model catalyst. The TPA molecule has two configurations (trans and cis) that can be reversibly converted to each other upon photo-excitation. Our calculations show that when the TPA takes the trans configuration, the combined system (trans-Au 8 ) is an excellent catalyst for CO oxidation. The reaction barrier of the catalyzed CO oxidation is less than 0.4 eV. While, the reaction barrier of CO oxidation catalyzed by cis-Au 8 is very high (>2.7 eV), indicating that the catalyst is inactive. These results pave the way for a new class of light controllable nanoscale catalysts.

Light controllable catalytic activity of Au clusters decorated with photochromic molecules

NASA Astrophysics Data System (ADS)

Guo, Na; Meng Yam, Kah; Zhang, Chun

2018-06-01

By ab initio calculations, we show that when decorated with a photochromic molecule, the catalytic activity of an Au nanocluster can be reversibly controlled by light. The combination of a photochromic thiol-pentacarbonyl azobenzene (TPA) molecule and an Au8 cluster is chosen as a model catalyst. The TPA molecule has two configurations (trans and cis) that can be reversibly converted to each other upon photo-excitation. Our calculations show that when the TPA takes the trans configuration, the combined system (trans-Au8) is an excellent catalyst for CO oxidation. The reaction barrier of the catalyzed CO oxidation is less than 0.4 eV. While, the reaction barrier of CO oxidation catalyzed by cis-Au8 is very high (>2.7 eV), indicating that the catalyst is inactive. These results pave the way for a new class of light controllable nanoscale catalysts.

A simple way to prepare Au@polypyrrole/Fe3O4 hollow capsules with high stability and their application in catalytic reduction of methylene blue dye

NASA Astrophysics Data System (ADS)

Yao, Tongjie; Cui, Tieyu; Wang, Hao; Xu, Linxu; Cui, Fang; Wu, Jie

2014-06-01

Metal nanoparticles are promising catalysts for dye degradation in treating wastewater despite the challenges of recycling and stability. In this study, we have introduced a simple way to prepare Au@polypyrrole (PPy)/Fe3O4 catalysts with Au nanoparticles embedded in a PPy/Fe3O4 capsule shell. The PPy/Fe3O4 capsule shell used as a support was constructed in one-step, which not only dramatically simplified the preparation process, but also easily controlled the magnetic properties of the catalysts through adjusting the dosage of FeCl2.4H2O. The component Au nanoparticles could catalyze the reduction of methylene blue dye with NaBH4 as a reducing agent and the reaction rate constant was calculated through the pseudo-first-order reaction equation. The Fe3O4 nanoparticles permitted quick recycling of the catalysts with a magnet due to their room-temperature superparamagnetic properties; therefore, the catalysts exhibited good reusability. In addition to catalytic activity and reusability, stability is also an important property for catalysts. Because both Au and Fe3O4 nanoparticles were wrapped in the PPy shell, compared with precursor polystyrene/Au composites and bare Fe3O4 nanoparticles, the stability of Au@PPy/Fe3O4 hollow capsules was greatly enhanced. Since the current method is simple and flexible to create recyclable catalysts with high stability, it would promote the practicability of metal nanoparticle catalysts in industrial polluted water treatment.Metal nanoparticles are promising catalysts for dye degradation in treating wastewater despite the challenges of recycling and stability. In this study, we have introduced a simple way to prepare Au@polypyrrole (PPy)/Fe3O4 catalysts with Au nanoparticles embedded in a PPy/Fe3O4 capsule shell. The PPy/Fe3O4 capsule shell used as a support was constructed in one-step, which not only dramatically simplified the preparation process, but also easily controlled the magnetic properties of the catalysts through adjusting the dosage of FeCl2.4H2O. The component Au nanoparticles could catalyze the reduction of methylene blue dye with NaBH4 as a reducing agent and the reaction rate constant was calculated through the pseudo-first-order reaction equation. The Fe3O4 nanoparticles permitted quick recycling of the catalysts with a magnet due to their room-temperature superparamagnetic properties; therefore, the catalysts exhibited good reusability. In addition to catalytic activity and reusability, stability is also an important property for catalysts. Because both Au and Fe3O4 nanoparticles were wrapped in the PPy shell, compared with precursor polystyrene/Au composites and bare Fe3O4 nanoparticles, the stability of Au@PPy/Fe3O4 hollow capsules was greatly enhanced. Since the current method is simple and flexible to create recyclable catalysts with high stability, it would promote the practicability of metal nanoparticle catalysts in industrial polluted water treatment. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00023d

Synthesis of multimetallic nanoparticles by seeded methods

NASA Astrophysics Data System (ADS)

Weiner, Rebecca Gayle

This dissertation focuses on the synthesis of metal nanocrystals (NCs) by seeded methods, in which preformed seeds serve as platforms for growth. Metal NCs are of interest due to their tunable optical and catalytic properties, which arise from their composition and crystallite size and shape. Moreover, multimetallic NCs are potentially multifunctional due to the integration of the properties of each metal within one structure. However, such structures are difficult to synthesize with structural definition due to differences in precursor reduction rates and the size-dependent solubility of bimetallic phases. Seed-mediated co-reduction (SMCR) is a method developed in the Skrabalak Laboratory that couples the advantages of a seeded method with co-reduction methods to achieve multimetallic nanomaterials with defined shape and architecture. This approach was originally demonstrated in a model Au-Pd system in which Au and Pd precursors were simultaneously reduced to deposit metal onto shape-controlled Au or Pd NC seeds. Using SMCR, uniformly branched core shell Au Au-Pd and Pd Au-Pd NCs were synthesized, with the shape of the seeds directing the symmetry of the final structures. By varying the seed shape and the temperature at which metal deposition occurs, the roles of adatom diffusion and seed shape on final NC morphology were decoupled. Moreover, by selecting seeds of a composition (Ag) different than the depositing metals (Au and Pd), trimetallic nanostructures are possible, including shape-controlled Ag Au-Pd NCs and hollow Au-Pd-Ag nanoparticles (NPs). The latter architecture arises through galvanic replacement. Shape-controlled core shell NCs with trimetallic shells are also possible by co-reducing three metal precursors (Ag, Au, and Pd) with shape-controlled Au seeds; for example, convex octopods, concave cubes, and truncated octahedra were achieved in this initial demonstration and was enabled by varying the ratio of Ag to Au/Pd in the overgrowth step as well as reaction pH. Ultimately, the final multimetallic nanostructure depends on the kinetics of metal deposition as well as seed composition, shape, reactivity, and crystallinity. In elucidating the roles of these parameters in nanomaterial synthesis, the rational design of new functional NCs becomes possible, which capitalize on the unique optical and catalytic properties of structurally defined multimetallic structures. In fact, branched Au-Pd NCs with high symmetry were found to be effective refractive index-based hydrogen sensors.

MAOA, DBH and SLC6A4 variants in CHARGE: A case control study of autism spectrum disorders

PubMed Central

Tassone, Flora; Qi, Lihong; Zhang, Wenting; Hansen, Robin L; Pessah, Isaac N; Hertz-Picciotto, Irva

2011-01-01

Background Genetic factors are established to contribute to the development of autism. We examined three loci, serotonin transporter (SLC6A4), dopamine hydroxylase (DBH) and the variable number of tandem repeat promoter of the monoamine oxidase A (MAOA) for association with autism in participants from the CHARGE (CHildhood Autism Risks from Genetics and the Environment) Study, the first large-scale population-based case-control investigation of both environmental and genetic contributions to autism risk. Methods Among male children enrolled in the CHARGE study we tested associations between each of the three polymorphisms and autism (AU) (n=119), or a combined group of autism and other autism spectrum disorders (AU+ASD, which includes an additional n=53) as compared with typically developing controls (TD, n=137). Results The case-control association analysis showed neither SLC6A4 nor DBH to be statistically significantly associated with AU or ASD. However, the male children carrying 4 tandem repeats in the promoter region of the MAOA gene showed a 2-fold higher risk of AU (or AU+ASD) than those carrying allele 3, adjusted for confounders (OR = 2.02, 95% CI = 1.12, 3.65, p = 0.02 for AU vs. TD, and OR = 2.05, 95% CI = 1.19, 3.53, p = 0.01 for ASD vs. TD). In addition, mothers homozygous for the 4 tandem repeat allele showed at least a 3-fold higher risk of AU (or AU+ASD) than mothers homozygous for allele 3 (OR = 3.07, 95% CI = 1.19, 7.91, p = 0.02 for AU vs. TD, and OR = 3.26, 95% CI = 1.35, 7.89, p = 0.009 for AU+ASD vs. TD). Conclusions These results suggest a potential role of the functional MAOA promoter alleles in the male child, the mother, or both in autism spectrum disorders. PMID:21538940

Bimetallic Pt-Au Nanocatalysts on ZnO/Al2O3/Monolith for Air Pollution Control.

PubMed

Kim, Ki-Joong; Ahn, Ho-Geun

2015-08-01

The catalytic activity of a monolithic catalyst with nanosized Pt and Au particles on ZnO/Al2O3 (Pt-Au/ZnO/Al2O3/M) prepared by a wash-coat method was examined, specifically for toluene oxidation. Scanning electron microscopy image showed clearly the formation of a ZnO/Al2O3 layer on the monolith. Nanosized Pt-Au particles on ZnO/Al2O3/M with different sizes could be found in the Pt-Au/ZnO/Al2O3/M catalyst. The conversion of toluene decreased with increasing toluene concentration and was also largely affected by the feed flow rate. The Pt-Au/ZnO/Al2O3/M catalysts prepared in this work have almost the same activity (molecules of toluene per second) compared with a powder Pt-Au/ZnO/Al2O3 catalyst with the same loadings of Pt and Au components; thus this catalyst could be used in controlling air pollution with very low concentrations and high flow rate.

Morphology-Controlled Synthesis of Au/Cu₂FeSnS₄ Core-Shell Nanostructures for Plasmon-Enhanced Photocatalytic Hydrogen Generation.

PubMed

Ha, Enna; Lee, Lawrence Yoon Suk; Man, Ho-Wing; Tsang, Shik Chi Edman; Wong, Kwok-Yin

2015-05-06

Copper-based chalcogenides of earth-abundant elements have recently arisen as an alternate material for solar energy conversion. Cu2FeSnS4 (CITS), a quaternary chalcogenide that has received relatively little attention, has the potential to be developed into a low-cost and environmentlly friendly material for photovoltaics and photocatalysis. Herein, we report, for the first time, the synthesis, characterization, and growth mechanism of novel Au/CITS core-shell nanostructures with controllable morphology. Precise manipulations in the core-shell dimensions are demonstrated to yield two distinct heterostructures with spherical and multipod gold nanoparticle (NP) cores (Au(sp)/CITS and Au(mp)/CITS). In photocatalytic hydrogen generation with as-synthesized Au/CITS NPs, the presence of Au cores inside the CITS shell resulted in higher hydrogen generation rates, which can be attributed to the surface plasmon resonance (SPR) effect. The Au(sp)/CITS and Au(mp)/CITS core-shell NPs enhanced the photocatalytic hydrogen generation by about 125% and 240%, respectively, compared to bare CITS NPs.

Gold nanoparticles induce transcriptional activity of NF-κB in a B-lymphocyte cell line

NASA Astrophysics Data System (ADS)

Sharma, Monita; Salisbury, Richard L.; Maurer, Elizabeth I.; Hussain, Saber M.; Sulentic, Courtney E. W.

2013-04-01

Gold nanoparticles (Au-NPs) have been designated as superior tools for biological applications owing to their characteristic surface plasmon absorption/scattering and amperometric (electron transfer) properties, in conjunction with low or no immediate toxicity towards biological systems. Many studies have shown the ease of designing application-based tools using Au-NPs but the interaction of this nanosized material with biomolecules in a physiological environment is an area requiring deeper investigation. Immune cells such as lymphocytes circulate through the blood and lymph and therefore are likely cellular components to come in contact with Au-NPs. The main aim of this study was to mechanistically determine the functional impact of Au-NPs on B-lymphocytes. Using a murine B-lymphocyte cell line (CH12.LX), treatment with citrate-stabilized 10 nm Au-NPs induced activation of an NF-κB-regulated luciferase reporter, which correlated with altered B lymphocyte function (i.e. increased antibody expression). TEM imaging demonstrated that Au-NPs can pass through the cellular membrane and therefore could interact with intracellular components of the NF-κB signaling pathway. Based on the inherent property of Au-NPs to bind to -thiol groups and the presence of cysteine residues on the NF-κB signal transduction proteins IκB kinases (IKK), proteins specifically bound to Au-NPs were extracted from CH12.LX cellular lysate exposed to 10 nm Au-NPs. Electrophoresis identified several bands, of which IKKα and IKKβ were immunoreactive. Further evaluation revealed activation of the canonical NF-κB signaling pathway as evidenced by IκBα phosphorylation at serine residues 32 and 36 followed by IκBα degradation and increased nuclear RelA. Additionally, expression of an IκBα super-repressor (resistant to proteasomal degradation) reversed Au-NP-induced NF-κB activation. Altered NF-κB signaling and cellular function in B-lymphocytes suggests a potential for off-target effects with in vivo applications of gold nanomaterials and underscores the need for more studies evaluating the interactions of nanomaterials with biomolecules and cellular components.

Experimental evidences of a large extrinsic spin Hall effect in AuW alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laczkowski, P.; Rojas-Sánchez, J.-C.; INAC/SP2M, CEA-Université Joseph Fourier, F-38054 Grenoble

2014-04-07

We report an experimental study of a gold-tungsten alloy (7 at. % W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity, and small induced damping, this AuW alloy may find applications in the nearest future.

Synthesis and in vitro cellular interactions of superparamagnetic iron nanoparticles with a crystalline gold shell

NASA Astrophysics Data System (ADS)

Bandyopadhyay, Sulalit; Singh, Gurvinder; Sandvig, Ioanna; Sandvig, Axel; Mathieu, Roland; Anil Kumar, P.; Glomm, Wilhelm Robert

2014-10-01

Fe@Au core-shell nanoparticles (NPs) exhibit multiple functionalities enabling their effective use in applications such as medical imaging and drug delivery. In this work, a novel synthetic method was developed and optimized for the synthesis of highly stable, monodisperse Fe@Au NPs of average diameter ∼24 nm exhibiting magneto-plasmonic characteristics. Fe@Au NPs were characterized by a wide range of experimental techniques, including scanning (transmission) electron microscopy (S(T)EM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS) and UV-vis spectroscopy. The formed particles comprise an amorphous iron core with a crystalline Au shell of tunable thickness, and retain the superparamagnetic properties at room temperature after formation of a crystalline Au shell. After surface modification, PEGylated Fe@Au NPs were used for in vitro studies on olfactory ensheathing cells (OECs) and human neural stem cells (hNSCs). No adverse effects of the Fe@Au particles were observed post-labeling, both cell types retaining normal morphology, viability, proliferation, and motility. It can be concluded that no appreciable toxic effects on both cell types, coupled with multifunctionality and chemical stability make them ideal candidates for therapeutic as well as diagnostic applications.

Configuration-controlled Au nanocluster arrays on inverse micelle nano-patterns: versatile platforms for SERS and SPR sensors

NASA Astrophysics Data System (ADS)

Jang, Yoon Hee; Chung, Kyungwha; Quan, Li Na; Špačková, Barbora; Šípová, Hana; Moon, Seyoung; Cho, Won Joon; Shin, Hae-Young; Jang, Yu Jin; Lee, Ji-Eun; Kochuveedu, Saji Thomas; Yoon, Min Ji; Kim, Jihyeon; Yoon, Seokhyun; Kim, Jin Kon; Kim, Donghyun; Homola, Jiří; Kim, Dong Ha

2013-11-01

Nanopatterned 2-dimensional Au nanocluster arrays with controlled configuration are fabricated onto reconstructed nanoporous poly(styrene-block-vinylpyridine) inverse micelle monolayer films. Near-field coupling of localized surface plasmons is studied and compared for disordered and ordered core-centered Au NC arrays. Differences in evolution of the absorption band and field enhancement upon Au nanoparticle adsorption are shown. The experimental results are found to be in good agreement with theoretical studies based on the finite-difference time-domain method and rigorous coupled-wave analysis. The realized Au nanopatterns are exploited as substrates for surface-enhanced Raman scattering and integrated into Kretschmann-type SPR sensors, based on which unprecedented SPR-coupling-type sensors are demonstrated.Nanopatterned 2-dimensional Au nanocluster arrays with controlled configuration are fabricated onto reconstructed nanoporous poly(styrene-block-vinylpyridine) inverse micelle monolayer films. Near-field coupling of localized surface plasmons is studied and compared for disordered and ordered core-centered Au NC arrays. Differences in evolution of the absorption band and field enhancement upon Au nanoparticle adsorption are shown. The experimental results are found to be in good agreement with theoretical studies based on the finite-difference time-domain method and rigorous coupled-wave analysis. The realized Au nanopatterns are exploited as substrates for surface-enhanced Raman scattering and integrated into Kretschmann-type SPR sensors, based on which unprecedented SPR-coupling-type sensors are demonstrated. Electronic supplementary information (ESI) available: TEM image and UV-vis absorption spectrum of citrate-capped Au NPs, AFM images of Au NC arrays on the PS-b-P4VP (41k-24k) template, ImageJ-analyzed results of PS-b-P4VP (41k-24k)-templated Au NC arrays, calculated %-surface coverage values, SEM images of Au NC arrays on the PS-b-P2VP (172k-42k) template for SPR biosensing, corresponding ImageJ-analyzed images by varying the Au NP deposition time and results of image analysis. See DOI: 10.1039/c3nr03860b

Structure and thermoelectric properties of Al-doped ZnO films prepared by thermal oxidization under high magnetic field

NASA Astrophysics Data System (ADS)

Liu, Shiying; Peng, Sunjuan; Ma, Jun; Li, Guojian; Qin, Xuesi; Li, Mengmeng; Wang, Qiang

2017-04-01

This paper studies the effects of high magnetic field (HMF) on the structure, optical and thermoelectric properties of the doped ZnO thin films. The results show that both Al dopant and application of HMF can affect the crystal structure, surface morphology, elemental distribution and so on. The particles of the thin films become small and regular by doping Al. The ZnO films oxidized from the Au/Zn bilayer have needle structure. The ZnO films oxidized from the Au/Zn-Al bilayer transform to spherical from hexagonal due to the application of HMF. The transmittance decreases with doping Al because of the opaque of Al element and decreases with the application of HMF due to the dense structure obtained under HMF. Electrical resistivity (ρ) of the ZnO films without Al decreases with increasing measurement temperature (T) and is about 1.5 × 10-3 Ω·m at 210 °C. However, the ρ of the Al-doped ZnO films is less than 10-5 Ω·m. The Seebeck coefficient (S) of the films oxidized from the Au/Zn-Al films reduces with increasing T. The S values oxidized under 0 T and 12 T conditions are 2.439 μV/K and -3.415 μV/K at 210 °C, respectively. Power factor reaches the maximum value (3.198 × 10-4 W/m·K2) at 210 °C for the film oxidized under 12 T condition. These results indicate that the Al dopant and the application of HMF can be used to control structure and thermoelectric properties of doped ZnO films.

Self-assembly of bacitracin-gold nanoparticles and their toxicity analysis.

PubMed

Li, Xiaoling; Wang, Zi; Li, Yanji; Bian, Kexin; Yin, Tian; Gao, Dawei

2018-01-01

As the widely use of gold nanoparticles (AuNPs) in drug delivery, the precise control on the size and morphology of the AuNPs is urgently required. In this scenario, traditional synthesis methods cannot meet current requirement because of their inherent defects. We have depicted here a novel method for fabricating monodispersed large size gold nanoparticles, based on the self-assembly of bacitracin. The AuNPs could be facilely, low-cost, and green synthesized with repeatability and controllability in this method. The Bac gold nanoparticles (Bac-AuNPs), composed by bacitracin core and gold shell, exhibited a spherical morphology in TEM and a face-centered cubic crystal structure in X-Ray diffraction and selected area electron diffraction. The mean diameter of the Bac-AuNPs was 89nm. The nanoparticles were mono-dispersed and the zeta potential of the nanoparticles was 4.1±0.64mV. Notably, in cell viability assay, the Bac-AuNPs showed less toxicity to HepG2 cells and HEK293 cells compared to small size AuNPs. Collectively, the size, rheological characteristic and the biocompatibility supported the use of the gold nanoparticles as intracellular delivery vehicles for drug delivery, especially for tumor therapy. And this study could provide a maneuverable, controllable and green strategy for the synthesis of AuNPs, which would be applied in disease diagnosis and therapy with biosafety. Copyright © 2017. Published by Elsevier B.V.

Gold nanorod linking to control plasmonic properties in solution and polymer nanocomposites.

PubMed

Ferrier, Robert C; Lee, Hyun-Su; Hore, Michael J A; Caporizzo, Matthew; Eckmann, David M; Composto, Russell J

2014-02-25

A novel, solution-based method is presented to prepare bifunctional gold nanorods (B-NRs), assemble B-NRs end-to-end in various solvents, and disperse linked B-NRs in a polymer matrix. The B-NRs have poly(ethylene glycol) grafted along its long axis and cysteine adsorbed to its ends. By controlling cysteine coverage, bifunctional ligands or polymer can be end-grafted to the AuNRs. Here, two dithiol ligands (C6DT and C9DT) are used to link the B-NRs in organic solvents. With increasing incubation time, the nanorod chain length increases linearly as the longitudinal surface plasmon resonance shifts toward lower adsorption wavelengths (i.e., red shift). Analogous to step-growth polymerization, the polydispersity in chain length also increases. Upon adding poly(ethylene glycol) or poly(methyl methacrylate) to chloroform solution with linked B-NR, the nanorod chains are shown to retain end-to-end linking upon spin-casting into PEO or PMMA films. Using quartz crystal microbalance with dissipation (QCM-D), the mechanism of nanorod linking is investigated on planar gold surfaces. At submonolayer coverage of cysteine, C6DT molecules can insert between cysteines and reach an areal density of 3.4 molecules per nm(2). To mimic the linking of Au NRs, this planar surface is exposed to cysteine-coated Au nanoparticles, which graft at 7 NPs per μm(2). This solution-based method to prepare, assemble, and disperse Au nanorods is applicable to other nanorod systems (e.g., CdSe) and presents a new strategy to assemble anisotropic particles in organic solvents and polymer coatings.

Gold Nanorod Linking to Control Plasmonic Properties in Solution and Polymer Nanocomposites

PubMed Central

2015-01-01

A novel, solution-based method is presented to prepare bifunctional gold nanorods (B-NRs), assemble B-NRs end-to-end in various solvents, and disperse linked B-NRs in a polymer matrix. The B-NRs have poly(ethylene glycol) grafted along its long axis and cysteine adsorbed to its ends. By controlling cysteine coverage, bifunctional ligands or polymer can be end-grafted to the AuNRs. Here, two dithiol ligands (C6DT and C9DT) are used to link the B-NRs in organic solvents. With increasing incubation time, the nanorod chain length increases linearly as the longitudinal surface plasmon resonance shifts toward lower adsorption wavelengths (i.e., red shift). Analogous to step-growth polymerization, the polydispersity in chain length also increases. Upon adding poly(ethylene glycol) or poly(methyl methacrylate) to chloroform solution with linked B-NR, the nanorod chains are shown to retain end-to-end linking upon spin-casting into PEO or PMMA films. Using quartz crystal microbalance with dissipation (QCM-D), the mechanism of nanorod linking is investigated on planar gold surfaces. At submonolayer coverage of cysteine, C6DT molecules can insert between cysteines and reach an areal density of 3.4 molecules per nm2. To mimic the linking of Au NRs, this planar surface is exposed to cysteine-coated Au nanoparticles, which graft at 7 NPs per μm2. This solution-based method to prepare, assemble, and disperse Au nanorods is applicable to other nanorod systems (e.g., CdSe) and presents a new strategy to assemble anisotropic particles in organic solvents and polymer coatings. PMID:24483622

New type of redox nanoprobe: C60-based nanomaterial and its application in electrochemical immunoassay for doping detection.

PubMed

Han, Jing; Zhuo, Ying; Chai, Ya-Qin; Xiang, Yun; Yuan, Ruo

2015-02-03

Carbon nanomaterials were usually exploited as nanocarriers in an electrochemical immunosensor but rarely acted as redox nanoprobes. Herein, our motivation is to adequately utilize the inner redox activity of fullerene (C60) to obtain a new type of redox nanoprobe based on a hydrophilic C60 nanomaterial. First, C60 nanoparticles (C60NPs) were prepared by phase-transfer method and functionalized with amino-terminated polyamidoamine (PAMAM) to obtain the PAMAM decorated C60NPs (PAMAM-C60NPs) which have better hydrophilicity compared to that of unmodified C60NPs and possesses abundant amine groups for further modification. Following that, gold nanoparticles (nano-Au) were absorbed on the PAMAM-C60NPs surface, and the resultant Au-PAMAM-C60NPs were employed as a new type of redox nanoprobe and nanocarrier to label detection antibodies (Ab2). Doping control has become the biggest problem facing international sport. Erythropoietin (EPO) as a blood doping agent has been a hotspot in doping control. After sandwich-type immunoreaction between EPO (as a model) and Ab2-labeled Au-PAMAM-C60NPs, the resultant immunosensor was further incubated with a drop of tetraoctylammonium bromide (TOAB) which acts as booster to arouse the inner redox activity of Au-PAMAM-C60NPs, thus a pair of reversible redox peaks is observed. As a result, the proposed immunosensor shows a wide linear range and a relatively low detection limit for EPO. This strategy paves a new avenue for exploring the redox nanoprobe based on carbon nanomaterials in the electrochemical biosensor field.

Noble Hybrid Nanostructures as Efficient Anti-Proliferative Platforms for Human Breast Cancer Cell.

PubMed

Tavangar, Amirhossein; Premnath, Priyatha; Tan, Bo; Venkatakrishnan, Krishnan

2016-04-27

Nanomaterials have proven to possess great potential in biomaterials research. Recently, they have suggested considerable promise in cancer diagnosis and therapy. Among others, silicon (Si) nanomaterials have been extensively employed for various biomedical applications; however, the utilization of Si for cancer therapy has been limited to nanoparticles, and its potential as anticancer substrates has not been fully explored. Noble nanoparticles have also received considerable attention owing to unique anticancer properties to improve the efficiency of biomaterials for numerous biological applications. Nevertheless, immobilization and control over delivery of the nanoparticles have been challenge. Here, we develop hybrid nanoplatforms to efficiently hamper breast cancer cell adhesion and proliferation. Platforms are synthesized by femtosecond laser processing of Si into multiphase nanostructures, followed by sputter-coating with gold (Au)/gold-palladium (Au-Pd) nanoparticles. The performance of the developed platforms was then examined by exploring the response of normal fibroblast and metastatic breast cancer cells. Our results from the quantitative and qualitative analyses show a dramatic decrease in the number of breast cancer cells on the hybrid platform compared to untreated substrates. Whereas, fibroblast cells form stable adhesion with stretched and elongated cytoskeleton and actin filaments. The hybrid platforms perform as dual-acting cytophobic/cytostatic stages where Si nanostructures depress breast cancer cell adhesion while immobilized Au/Au-Pd nanoparticles are gradually released to affect any surviving cell on the nanostructures. The nanoparticles are believed to be taken up by breast cancer cells via endocytosis, which subsequently alter the cell nucleus and may cause cell death. The findings suggest that the density of nanostructures and concentration of coated nanoparticles play critical roles on cytophobic/cytostatic properties of the platforms on human breast cancer cells while having no or even cytophilic effects on fibroblast cells. Because of the remarkable contrary responses of normal and cancer cells to the proposed platform, we envision that it will provide novel applications in cancer research.

Photo-controlled aptamers delivery by dual surface gold-magnetic nanoparticles for targeted cancer therapy.

PubMed

Zhao, Jian; Tu, Keyao; Liu, Yanlei; Qin, Yulei; Wang, Xiwei; Qi, Lifeng; Shi, Donglu

2017-11-01

Dual surfaced dumbbell-like gold magnetic nanoparticles (Au-Fe 3 O 4 ) were synthesized for targeted aptamers delivery. Their unique biological properties were characterized as a smart photo-controlled drug carrier. DNA aptamers targeting vascular endothelial growth factor (VEGF) were assembled onto the surface of Au-Fe 3 O 4 by electrostatic absorption. The binding capacity of the nanoparticles with VEGF aptamers was confirmed by gel electrophoresis. The targeted recognization of ovarian cancer cells by the aptamers-functionalized Au-Fe 3 O 4 nanoparticles (Apt-Au-Fe 3 O 4 NPs) was observed by confocal microscopy. Apt-Au-Fe 3 O 4 was found to bind with SKOV-3 ovarian cancer cells specifically, leading to marked intracellular release of aptamers upon plasmon-resonant light (605nm) radiation, and to enhance the in vitro inhibition against tumor cell proliferation. The results show high potential of Apt-Au-Fe 3 O 4 as a targeted cancer hyperthermia carrier by remote control with high spatial/temporal resolution. Copyright © 2017. Published by Elsevier B.V.

Blood mercury concentrations in CHARGE Study children with and without autism.

PubMed

Hertz-Picciotto, Irva; Green, Peter G; Delwiche, Lora; Hansen, Robin; Walker, Cheryl; Pessah, Isaac N

2010-01-01

Some authors have reported higher blood mercury (Hg) levels in persons with autism, relative to unaffected controls. We compared blood total Hg concentrations in children with autism or autism spectrum disorder (AU/ASD) and typically developing (TD) controls in population-based samples, and determined the role of fish consumption in differences observed. The Childhood Autism Risk from Genetics and the Environment (CHARGE) Study enrolled children 2-5 years of age. After diagnostic evaluation, we analyzed three groups: AU/ASD, non-AU/ASD with developmental delay (DD), and population-based TD controls. Mothers were interviewed about household, medical, and dietary exposures. Blood Hg was measured by inductively coupled plasma mass spectrometry. Multiple linear regression analysis was conducted (n = 452) to predict blood Hg from diagnostic status controlling for Hg sources. Fish consumption strongly predicted total Hg concentration. AU/ASD children ate less fish. After adjustment for fish and other Hg sources, blood Hg levels in AU/ASD children were similar to those of TD children (p = 0.75); this was also true among non-fish eaters (p = 0.73). The direct effect of AU/ASD diagnosis on blood Hg not through the indirect pathway of altered fish consumption was a 12% reduction. DD children had lower blood Hg concentrations in all analyses. Dental amalgams in children with gum-chewing or teeth-grinding habits predicted higher levels. After accounting for dietary and other differences in Hg exposures, total Hg in blood was neither elevated nor reduced in CHARGE Study preschoolers with AU/ASD compared with unaffected controls, and resembled those of nationally representative samples.

Green synthesis of bacterial mediated anti-proliferative gold nanoparticles: inducing mitotic arrest (G2/M phase) and apoptosis (intrinsic pathway)

NASA Astrophysics Data System (ADS)

Ganesh Kumar, C.; Poornachandra, Y.; Chandrasekhar, Cheemalamarri

2015-11-01

The physiochemical and biological properties of microbial derived gold nanoparticles have potential applications in various biomedical domains as well as in cancer therapy. We have fabricated anti-proliferative bacterial mediated gold nanoparticles (b-Au NPs) using a culture supernatant of Streptomyces clavuligerus and later characterized them by UV-visible, TEM, DLS, XRD and FT-IR spectroscopic techniques. The capping agent responsible for the nanoparticle formation was characterized based on SDS-PAGE and MALDI-TOF-MS analyses. They were tested for anticancer activity in A549, HeLa and DU145 cell lines. The biocompatibility and non-toxic nature of the nanoparticles were tested on normal human lung cell line (MRC-5). The b-Au NPs induced the cell cycle arrest in G2/M phase and also inhibited the microtubule assembly in DU145 cells. Mechanistic studies, such as ROS, MMP, Cyt-c, GSH, caspases 9, 8 and 3 activation and the Annexin V-FITC staining, along with the above parameters tested provided sufficient evidence that the b-Au NPs induced apoptosis through the intrinsic pathway. The results supported the use of b-Au NPs for future therapeutic application in cancer therapy and other biomedical applications.The physiochemical and biological properties of microbial derived gold nanoparticles have potential applications in various biomedical domains as well as in cancer therapy. We have fabricated anti-proliferative bacterial mediated gold nanoparticles (b-Au NPs) using a culture supernatant of Streptomyces clavuligerus and later characterized them by UV-visible, TEM, DLS, XRD and FT-IR spectroscopic techniques. The capping agent responsible for the nanoparticle formation was characterized based on SDS-PAGE and MALDI-TOF-MS analyses. They were tested for anticancer activity in A549, HeLa and DU145 cell lines. The biocompatibility and non-toxic nature of the nanoparticles were tested on normal human lung cell line (MRC-5). The b-Au NPs induced the cell cycle arrest in G2/M phase and also inhibited the microtubule assembly in DU145 cells. Mechanistic studies, such as ROS, MMP, Cyt-c, GSH, caspases 9, 8 and 3 activation and the Annexin V-FITC staining, along with the above parameters tested provided sufficient evidence that the b-Au NPs induced apoptosis through the intrinsic pathway. The results supported the use of b-Au NPs for future therapeutic application in cancer therapy and other biomedical applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04577k

How Does Amino Acid Ligand Modulate Au Core Structure and Characteristics in Peptide Coated Au Nanocluster?

PubMed

Li, Nan; Li, Xu; Zhao, Hongkang; Zhao, Lina

2018-03-01

The atomic structures and the corresponding physicochemical properties of peptide coated Au nanoclusters determine their distinctive biological targeting applications. To learn the modulation of amino acid ligand on the atomic structure and electronic characteristics of coated Au core is the fundamental knowledge for peptide coated Au nanocluster design and construction. Based on our recent coated Au nanocluster configuration study (Nanoscale, 2016, 8, 11454), we built the typically simplified Au13(Cys-Au-Cys) system to more clearly learn the basic modulation information of amino acid ligand on Au core by the density functional theory (DFT) calculations. There are two isomers as ligand adjacent bonding (Iso1) and diagonal bonding (Iso2) to Au13 cores. The geometry optimizations indicate the adjacent bonding Iso1 is more stable than Iso2. More important, the Au13 core of Iso1 distorts much more significantly than that of Iso2 by Cys-Au-Cys bonding through the root-mean-square deviation (RMSD) analysis, which modulate their electronic characteristics in different ways. In addition, the frontier molecular orbital results of Au13(Cys-Au-Cys) isomers confirm that the Au cores mainly determine the blue shifts of Au13(Cys-Au-Cys) systems versus the original Au13 core in their UV-visible absorption spectrum studies. The configuration of Au13 core performs deformation under Cys-Au-Cys ligand modulation to reach new stability with distinct atomic structure and electronic properties, which could be the theory basis for peptide coated AuNCs design and construction.

Visible light plasmonic heating of Au-ZnO for the catalytic reduction of CO 2

DOE PAGES

Wang, Congjun; Ranasingha, Oshadha; Natesakhawat, Sittichai; ...

2013-01-01

Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO 2 and H 2 reactants to CH 4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au–ZnO from 30 to ~600 °C and simultaneously tune the CH 4 : CO product ratio. The laser induced heating and resulting CH 4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction ismore » a thermally driven process resulting from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO 2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO 2 reduction is low ( ~2.5 x 10 5 W m -2) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO 2 utilization and other practical thermal catalytic applications.« less

The use of plants in prospecting for gold: A brief overview with a selected bibliography and topic index

USGS Publications Warehouse

Erdman, J.A.; Olson, J.C.

1985-01-01

The focal point of this report is a bibliography of 133 references and an associated topic index - both of which could be useful to geochemists attempting to locate new Au deposits. Fifty of these references originated in the Soviet Union, where most of the initial work on biogeochemical exploration for Au had been done. The 15 topics in the index range from agriculture (Au in crop plants) to silver. As an introduction to the bibliography, we have briefly described some examples of applications and difficulties in using plants. These examples are drawn from the literature and from field experience. Because of the generally low Au concentrations found in plants, the analysis of plant tissue is critical to the successful application of the biogeochemical method of prospecting. Neuron activation analysis is the most widely used method to detect Au in plants, due largely to its sensitivity; levels in the parts per billion range are easily attained. Two general types of sampling media are used in prospecting for Au: humus and living plants. Humus has been widely used in Canada, but the sampling of plants has increased there and elsewhere in recent years. Our use of douglas-fir (Pseudotsuga menziesii) at a Au-bearing stockwork in Idaho is a prime example. A maximum Au concentration of 14 ??g/g (ppm) was detected in the wood ash of this coniferous tree, well above the normal concentration of ??? 0.15 ??g/g. Among shrubs that might be useful in Au prospecting, we recommend sagebrush or wormwood (genus Artemisia), because it is extremely responsive to concealed mineralization. It has been used extensively in the Soviet Union and could be used in areas of the western United States where disseminated Au occurrences might be located. Among the problems one may encounter in using plants for Au prospecting are: (1) physiological barriers, by which many plant species simply do not absorb Au at detectable levels; (2) misconceptions of soil-plant correlations; (3) localization of Au in plant tissue; and (4) the variation of Au concentrations due to season. Despite these limitations, biogeochemical techniques can complement or replace other geochemical methods currently used. ?? 1985.

Modification of emission photon statistics from single quantum dots using metal/SiO2 core/shell nanostructures.

PubMed

Naiki, Hiroyuki; Oikawa, Hidetoshi; Masuo, Sadahiro

2017-04-12

Emission photon statistics, i.e., single-photon and multi-photon emissions, of isolated QDs is required for tailoring optoelectronic applications. In this article, we demonstrate that the emission photon statistics can be modified by the control of the spectral overlap of the QDs with the localized surface plasmon resonance (LSPR) of the metal nanoparticle (metal NP) and by the distance between the QD and the metal NP. Moreover, the contribution to the modification of the emission photon statistics, which is the excitation and emission enhancements and the quenching generated by the spectral overlap and the distance, is elucidated. By fabricating well-defined SiO 2 -coated AgNPs and AuNPs (metal/SiO 2 ), the spectral overlap originated from the metal species of Ag and Au and the distance constituted by the thickness of the SiO 2 shell are controlled. The probability of single-photon emission of single QD was increased by the enhancement of the excitation rate via adjusting the distance using Ag/SiO 2 while the single-photon emission was converted to multi-photon emission by the effect of exciton quenching at a short distance and a small spectral overlap. By contrast, the probability of multi-photon emission was increased by enhancement of the multi-photon emission rate and the quenching via the spectral overlap using Au/SiO 2 . These results indicated the fundamental finding to control emission photon statistics in single QDs by controlling the spectral overlap and the distance, and understand the interaction of plasmonic nanostructures and single QD systems.

Determination of functionalized gold nanoparticles incorporated in hydrophilic and hydrophobic microenvironments by surface modification of quartz crystal microbalance

NASA Astrophysics Data System (ADS)

Wu, Tsui-Hsun; Liao, Shu-Chuan; Chen, Ying-Fang; Huang, Yi-You; Wei, Yi-Syuan; Tu, Shu-Ju; Chen, Ko-Shao

2013-06-01

In this study, plasma deposition methods were used to immobilize Au electrode of a quartz crystal microbalance (QCM) to create different microenvironments for mass measurement of various modified Au nanoparticles (AuNPs). AuNPs were modified by 11-mercaptoundecanoic acid (MUA) and 1-decanethiol (DCT) for potential applications to drug release, protective coatings, and immunosensors. We aimed to develop a highly sensitive and reliable method to quantify the mass of various modified AuNPs. The surface of AuNPs and Au electrode was coated with polymer films, as determined by Fourier transform infrared spectroscopy and atomic force microscopy. Measurements obtained for various AuNPs and the plasma-treated surface of the Au electrode were compared with those obtained for an untreated Au electrode. According to the resonant frequency shift of QCM, a linear relationship was observed that significantly differed for AuNPs, MUA-AuNPs, and DCT-AuNPs (R2 range, 0.94-0.965, 0.934-0.972, and 0.874-0.9514, respectively). Compared to inductively coupled plasma and micro-computerized tomography, the QCM method with plasma treatment has advantages of real-time monitoring, greater sensitivity, and lower cost. Our results demonstrate that surface modifications measured by a QCM system for various modified AuNPs were reliable.

Architecture effects of glucose oxidase/Au nanoparticle composite Langmuir-Blodgett films on glucose sensing performance

NASA Astrophysics Data System (ADS)

Wang, Ke-Hsuan; Wu, Jau-Yann; Chen, Liang-Huei; Lee, Yuh-Lang

2016-03-01

The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).

Study on plasmon absorption of hybrid Au-GO-GNP films for SPR sensing application

NASA Astrophysics Data System (ADS)

Mukhtar, Wan Maisarah; Ahmad, Farah Hayati; Samsuri, Nurul Diyanah; Murat, Noor Faezah

2018-06-01

This study proposed the development of hybrid Au-GO-GNP films for the enhancement of plasmon absorption in SPR sensing. Several thicknesses of Au at t=40nm, t=50nm and t=300nm were sputtered on the glass substrate. The hybridization of bilayer and trilayer films were formed by depositing GO-GNP layers and GNP-GO layers on top of various thicknesses of Au coated substrates. UV-Vis spectra analysis was conducted to characterize the plasmon absorption for each configuration. The plasmon absorption was successfully amplified by employing hybrid trilayer Au-GO-GNP with the thickness of Au film was fixed at t=50nm. It is noteworthy to highlight that the employment of bilayer and trilayer configurations are the key success to enhance the SPP excitation. Au-GNP and Au-GNP-GO results no significant outcome in comparison with Au-GO and Au-GO-GNP. A redshift of the absorbance wavelength evinces the presence of GO on Au-GO sample and GNP on Au-GO-GNP sample due to the surface reconstruction. It is important to emphasize that not all bilayer and trilayer configurations able to enhance the plasmon absorption where no significant output was obtained with the hybridization order of Au-GNP and Au-GNP-GO.

Controlled Vectorial Electron Transfer and Photoelectrochemical Applications of Layered Relay/Photosensitizer-Imprinted Au Nanoparticle Architectures on Electrodes.

PubMed

Metzger, Tzuriel S; Tel-Vered, Ran; Willner, Itamar

2016-03-23

Two configurations of molecularly imprinted bis-aniline-bridged Au nanoparticles (NPs) for the specific binding of the electron acceptor N,N'-dimethyl-4,4'-bipyridinium (MV(2+) ) and for the photosensitizer Zn(II)-protoporphyrin IX (Zn(II)-PP-IX) are assembled on electrodes, and the photoelectrochemical features of the two configurations are discussed. Configuration I includes the MV(2+) -imprinted Au NPs matrix as a base layer, on which the Zn(II)-PP-IX-imprinted Au NPs layer is deposited, while configuration II consists of a bilayer corresponding to the reversed imprinting order. Irradiation of the two electrodes in the presence of a benzoquinone/benzohydroquinone redox probe yields photocurrents of unique features: (i) Whereas configuration I yields an anodic photocurrent, the photocurrent generated by configuration II is cathodic. (ii) The photocurrents obtained upon irradiation of the imprinted electrodes are substantially higher as compared to the nonimprinted surfaces. The high photocurrents generated by the imprinted Au NPs-modified electrodes are attributed to the effective loading of the imprinted matrices with the MV(2+) and Zn(II)-PP-IX units and to the effective charge separation proceeding in the systems. The directional anodic/cathodic photocurrents are rationalized in terms of vectorial electron transfer processes dictated by the imprinting order and by the redox potentials of the photosensitizer/electron acceptor units associated with the imprinted sites in the two configurations. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Colorimetric Detection of Small Molecules in Complex Matrixes via Target-Mediated Growth of Aptamer-Functionalized Gold Nanoparticles.

PubMed

Soh, Jun Hui; Lin, Yiyang; Rana, Subinoy; Ying, Jackie Y; Stevens, Molly M

2015-08-04

A versatile and sensitive colorimetric assay that allows the rapid detection of small-molecule targets using the naked eye is demonstrated. The working principle of the assay integrates aptamer-target recognition and the aptamer-controlled growth of gold nanoparticles (Au NPs). Aptamer-target interactions modulate the amount of aptamer strands adsorbed on the surface of aptamer-functionalized Au NPs via desorption of the aptamer strands when target molecules bind with the aptamer. Depending on the resulting aptamer coverage, Au NPs grow into morphologically varied nanostructures, which give rise to different colored solutions. Au NPs with low aptamer coverage grow into spherical NPs, which produce red-colored solutions, whereas Au NPs with high aptamer coverage grow into branched NPs, which produce blue-colored solutions. We achieved visible colorimetric response and nanomolar detection limits for the detection of ochratoxin A (1 nM) in red wine samples, as well as cocaine (1 nM) and 17β-estradiol (0.2 nM) in spiked synthetic urine and saliva, respectively. The detection limits were well within clinically and physiologically relevant ranges, and below the maximum food safety limits. The assay is highly sensitive, specific, and able to detect an array of analytes rapidly without requiring sophisticated equipment, making it relevant for many applications, such as high-throughput drug and clinical screening, food sampling, and diagnostics. Furthermore, the assay is easily adapted as a chip-based platform for rapid and portable target detection.

Colloidal Au and Au-alloy catalysts for direct borohydride fuel cells: Electrocatalysis and fuel cell performance

NASA Astrophysics Data System (ADS)

Atwan, Mohammed H.; Macdonald, Charles L. B.; Northwood, Derek O.; Gyenge, Elod L.

Supported colloidal Au and Au-alloys (Au-Pt and Au-Pd, 1:1 atomic ratio) on Vulcan XC-72 (with 20 wt% metal load) were prepared by the Bönneman method. The electrocatalytic activity of the colloidal metals with respect to borohydride electro-oxidation for fuel cell applications was investigated by voltammetry on static and rotating electrodes, chronoamperometry, chronopotentiometry and fuel cell experiments. The fundamental electrochemical techniques showed that alloying Au, a metal that leads to the maximum eight-electron oxidation of BH 4 -, with Pd or Pt, well-known catalysts of dehydrogenation reactions, improved the electrode kinetics of BH 4 - oxidation. Fuel cell experiments corroborated the kinetic studies. Using 5 mg cm -2 colloidal metal load on the anode, it was found that Au-Pt was the most active catalyst giving a cell voltage of 0.47 V at 100 mA cm -2 and 333 K, while under identical conditions the cell voltage using colloidal Au was 0.17 V.

Ordered arrays of Au catalysts by FIB assisted heterogeneous dewetting.

PubMed

Benkouider, A; Ronda, A; David, T; Favre, L; Abbarchi, M; Naffouti, M; Osmond, J; Delobbe, A; Sudraud, P; Berbezier, I

2015-12-18

Synthesizing Au0.8Si0.2 nanocatalysts that are homogeneous in size and have controlled position is becoming a challenging and crucial prequisite for the fabrication of ordered semiconductor nanowires. In this study, Au0.8Si0.2 nanocatalysts are synthesized via dewetting of Au layers on Si(111) during thermal annealing in an ultra-high vacuum. In the first part of the paper, the mechanism of homogeneous dewetting is analyzed as a function of the Au-deposited thickness (h Au). We distinguish three different dewetting regimes: (I) for a low thickness ([Formula: see text]), a submonolyer coverage of Au is stabilized and there is no dewetting. (II) For an intermediate thickness ([Formula: see text]), there is both dewetting and Au0.8Si0.2 phase formation. The size and density of the Au0.8Si0.2 clusters are directly related to h Au. When cooling down to room temperature, the clusters decompose and reject the Si at the Au/Si substrate interface. (III) For a large thickness ([Formula: see text]), only dewetting takes place, without forming AuSi clusters. In this regime, the dewetting is kinetically controlled by the self-diffusion of Au (activation energy ∼0.43 eV) without evidence of an Si-alloying effect. As a practical consequence, when relying solely on the homogeneous dewetting of Au/Si(111) to form the Au0.8Si0.2 catalysts (without a supply of Si atoms from vapor), regime II should be used to obtain good size and density control. In the second part of the paper, a process for ordering the catalysts using focused ion beam-(FIB) assisted dewetting (heterogeneous dewetting) is developed. We show that no matter what the FIB milling conditions and the Au nominal thickness are, dewetting is promoted by ion beam irradiation and is accompanied by the formation of Au0.8Si0.2 droplets. The droplets preferentially form on the patterned areas, while in similar annealing conditions, they do not form on the unpatterned areas. This behavior is attributed to the larger Au-Si interdiffusion in the patterned areas, which results from the Si amorphization induced by the FIB. A systematic analysis of the position of the nanodroplets shows their preferential nucleation inside the patterns, while thicker platelets of almost pure Au are observed between the patterns. The evolutions of the size homogeneity and the occupancy rate of the patterns are quantified as a function of the FIB dose and annealing temperature. Nice arrays of perfectly ordered AuSi catalysts are obtained after optimizing the FIB and dewetting conditions.

Covalent Coupling of Nanoparticles with Low-Density Functional Ligands to Surfaces via Click Chemistry

PubMed Central

Rianasari, Ina; de Jong, Michel P.; Huskens, Jurriaan; van der Wiel, Wilfred G.

2013-01-01

We demonstrate the application of the 1,3-dipolar cycloaddition (“click” reaction) to couple gold nanoparticles (Au NPs) functionalized with low densities of functional ligands. The ligand coverage on the citrate-stabilized Au NPs was adjusted by the ligand:Au surface atom ratio, while maintaining the colloidal stability of the Au NPs in aqueous solution. A procedure was developed to determine the driving forces governing the selectivity and reactivity of citrate-stabilized and ligand-functionalized Au NPs on patterned self-assembled monolayers. We observed selective and remarkably stable chemical bonding of the Au NPs to the complimentarily functionalized substrate areas, even when estimating that only 1–2 chemical bonds are formed between the particles and the substrate. PMID:23434666

Growth of polymer-metal nanocomposites by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Röder, Johanna; Faupel, Jörg; Krebs, Hans-Ulrich

2008-12-01

Complex polymer-metal nanocomposites have a wide range of applications, e.g. as flexible displays and packaging materials. Pulsed laser deposition was applied to form nanostructured materials consisting of metal clusters (Ag, Au, Pd and Cu) embedded in a polymer (polycarbonate, PC) matrix. The size and amount of the metal clusters are controlled by the number of laser pulses hitting the respective targets. For Cu and Pd, smaller clusters and higher cluster densities are obtained as in the cases of Ag and Au due to a stronger reactivity with the polymers and thus a lower diffusivity. Implantation effects, differences in metal diffusivity and reactivity on the polymer surfaces, and the coalescence properties are discussed with respect to the observed microstructures on PC and compared to the metal growth on poly (methyl methacrylate), PMMA.

Facile synthesis of hierarchical gold nanostructures and their catalytic application

NASA Astrophysics Data System (ADS)

Ma, Ying; Siang Yi, Edward Ng

2016-08-01

We demonstrate a one-step, surfactant-free method to prepare gold (Au) nanostructures using a synthesized aniline (ANI) derivative N-(3-amidino)-aniline (NAAN) as a reducing agent. By simply mixing NAAN with a Au precursor, raspberry-like Au particles (RSPs) were formed. The presence of Ag+ resulted in the formation of Au nanoflowers (AuNFs). The size and shape of the AuNFs can be tuned by the reaction conditions such as the NAAN/HAuCl4 ratio, the temperature and the solvent composition. Under the same reaction conditions, bowling-pin-like particles (BPLPs) were reported for the first time using commercial ANI as a reducing agent. The AuNFs exhibited good ability to oxidize peroxidase substrate 3, 3‧, 5, 5‧-tetramethylbenzidine (TMB) by H2O2, allowing them as a peroxidase mimetic.

Gold nanoparticles based colorimetric nanodiagnostics for cancer and infectious diseases

NASA Astrophysics Data System (ADS)

Valentini, Paola; Persano, Stefano; Cecere, Paola; Sabella, Stefania; Pompa, Pier Paolo

2014-03-01

Traditional in vitro diagnostics requires specialized laboratories and costly instrumentation, both for the amplification of nucleic acid targets (usually achieved by PCR) and for the assay readout, often based on fluorescence. We are developing hybrid nanomaterials-based sensors for the rapid and low-cost diagnosis of various disease biomarkers, for applications in portable platforms for diagnostics at the point-of-care. To this aim, we exploited the size and distancedependent optical properties of gold nanoparticles (AuNPs) to achieve colorimetric detection. Moreover, in order to avoid the complexity of thermal cycles associated to traditional PCR, the design of our systems includes signal amplification schemes, achieved by the use of enzymes (nucleases, helicase) or DNAzymes. Focused on instrument-free and sensitive detection, we carefully combined the intrinsic sensitivity by multivalency of functionalized AuNPs with isothermal and non-stringent enzyme-aided reaction conditions, controlled AuNPs aggregates, universal reporters and magnetic microparticles, the latter used both as a substrate and as a means for the colorimetric detection. We obtained simple and robust assays for the sensitive (pM range or better) naked-eye detection of cancer or infectious diseases (HPV, HCV) biomarkers, requiring no instrumentation except for a simple heating plate. Finally, we are also developing non-medical applications of these bio-nanosensors, such as in the development of on-field rapid tests for the detection of pollutants and other food and water contaminants.

Graphene–Gold Nanoparticles Hybrid—Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor

PubMed Central

Khalil, Ibrahim; Julkapli, Nurhidayatullaili Muhd; Yehye, Wageeh A.; Basirun, Wan Jefrey; Bhargava, Suresh K.

2016-01-01

Graphene is a single-atom-thick two-dimensional carbon nanosheet with outstanding chemical, electrical, material, optical, and physical properties due to its large surface area, high electron mobility, thermal conductivity, and stability. These extraordinary features of graphene make it a key component for different applications in the biosensing and imaging arena. However, the use of graphene alone is correlated with certain limitations, such as irreversible self-agglomerations, less colloidal stability, poor reliability/repeatability, and non-specificity. The addition of gold nanostructures (AuNS) with graphene produces the graphene–AuNS hybrid nanocomposite which minimizes the limitations as well as providing additional synergistic properties, that is, higher effective surface area, catalytic activity, electrical conductivity, water solubility, and biocompatibility. This review focuses on the fundamental features of graphene, the multidimensional synthesis, and multipurpose applications of graphene–Au nanocomposites. The paper highlights the graphene–gold nanoparticle (AuNP) as the platform substrate for the fabrication of electrochemical and surface-enhanced Raman scattering (SERS)-based biosensors in diverse applications as well as SERS-directed bio-imaging, which is considered as an emerging sector for monitoring stem cell differentiation, and detection and treatment of cancer. PMID:28773528

Graphene-Gold Nanoparticles Hybrid-Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor.

PubMed

Khalil, Ibrahim; Julkapli, Nurhidayatullaili Muhd; Yehye, Wageeh A; Basirun, Wan Jefrey; Bhargava, Suresh K

2016-05-24

Graphene is a single-atom-thick two-dimensional carbon nanosheet with outstanding chemical, electrical, material, optical, and physical properties due to its large surface area, high electron mobility, thermal conductivity, and stability. These extraordinary features of graphene make it a key component for different applications in the biosensing and imaging arena. However, the use of graphene alone is correlated with certain limitations, such as irreversible self-agglomerations, less colloidal stability, poor reliability/repeatability, and non-specificity. The addition of gold nanostructures (AuNS) with graphene produces the graphene-AuNS hybrid nanocomposite which minimizes the limitations as well as providing additional synergistic properties, that is, higher effective surface area, catalytic activity, electrical conductivity, water solubility, and biocompatibility. This review focuses on the fundamental features of graphene, the multidimensional synthesis, and multipurpose applications of graphene-Au nanocomposites. The paper highlights the graphene-gold nanoparticle (AuNP) as the platform substrate for the fabrication of electrochemical and surface-enhanced Raman scattering (SERS)-based biosensors in diverse applications as well as SERS-directed bio-imaging, which is considered as an emerging sector for monitoring stem cell differentiation, and detection and treatment of cancer.

High hardness in the biocompatible intermetallic compound β-Ti3Au

PubMed Central

Svanidze, Eteri; Besara, Tiglet; Ozaydin, M. Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K.; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M.; Morosan, E.

2016-01-01

The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti–Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials. PMID:27453942

Hot electron induced NIR detection in CdS films.

PubMed

Sharma, Alka; Kumar, Rahul; Bhattacharyya, Biplab; Husale, Sudhir

2016-03-11

We report the use of random Au nanoislands to enhance the absorption of CdS photodetectors at wavelengths beyond its intrinsic absorption properties from visible to NIR spectrum enabling a high performance visible-NIR photodetector. The temperature dependent annealing method was employed to form random sized Au nanoparticles on CdS films. The hot electron induced NIR photo-detection shows high responsivity of ~780 mA/W for an area of ~57 μm(2). The simulated optical response (absorption and responsivity) of Au nanoislands integrated in CdS films confirms the strong dependence of NIR sensitivity on the size and shape of Au nanoislands. The demonstration of plasmon enhanced IR sensitivity along with the cost-effective device fabrication method using CdS film enables the possibility of economical light harvesting applications which can be implemented in future technological applications.

High hardness in the biocompatible intermetallic compound β-Ti3Au.

PubMed

Svanidze, Eteri; Besara, Tiglet; Ozaydin, M Fevsi; Tiwary, Chandra Sekhar; Wang, Jiakui K; Radhakrishnan, Sruthi; Mani, Sendurai; Xin, Yan; Han, Ke; Liang, Hong; Siegrist, Theo; Ajayan, Pulickel M; Morosan, E

2016-07-01

The search for new hard materials is often challenging, but strongly motivated by the vast application potential such materials hold. Ti3Au exhibits high hardness values (about four times those of pure Ti and most steel alloys), reduced coefficient of friction and wear rates, and biocompatibility, all of which are optimal traits for orthopedic, dental, and prosthetic applications. In addition, the ability of this compound to adhere to ceramic parts can reduce both the weight and the cost of medical components. The fourfold increase in the hardness of Ti3Au compared to other Ti-Au alloys and compounds can be attributed to the elevated valence electron density, the reduced bond length, and the pseudogap formation. Understanding the origin of hardness in this intermetallic compound provides an avenue toward designing superior biocompatible, hard materials.

Green Chemistry Techniques for Gold Nanoparticles Synthesis

NASA Astrophysics Data System (ADS)

Cannavino, Sarah A.; King, Christy A.; Ferrara, Davon W.

Gold nanoparticles (AuNPs) are often utilized in many technological and research applications ranging from the detection of tumors, molecular and biological sensors, and as nanoantennas to probe physical processes. As these applications move from the research laboratory to industrial settings, there is a need to develop efficient and sustainable synthesis techniques. Recent research has shown that several food products and beverages containing polyphenols, a common antioxidant, can be used as reducing agents in the synthesis of AuNPs in solution. In this study, we explore a variety of products to determine which allow for the most reproducible solution of nanoparticles based on the size and shapes of particles present. We analyzed the AuNPs solutions using extinction spectroscopy and atomic force microscopy. We also develop a laboratory activity to introduce introductory chemistry and physics students to AuNP synthesis techniques and analysis.

Tuning of gold nanoclusters sensing applications with bovine serum albumin and bromelain for detection of Hg2+ ion and lambda-cyhalothrin via fluorescence turn-off and on mechanisms.

PubMed

Bhamore, Jigna R; Jha, Sanjay; Basu, Hirakendu; Singhal, Rakesh Kumar; Murthy, Z V P; Kailasa, Suresh Kumar

2018-04-01

Herein, fluorescent gold nanoclusters (Au NCs) were obtained by one-pot synthetic method using bovine serum albumin (BSA) and bromelain as templates. As-synthesized fluorescent Au NCs were stable and showed bright red fluorescence under UV lamp at 365 nm. The fluorescent Au NCs exhibit the emission intensity at 648 nm when excited at 498 nm. Various techniques were used such as spectroscopy (UV-visible, fluorescence, and Fourier-transform infrared), high-resolution transmission electron microscopy, and dynamic light scattering for the characterization of fluorescent Au NCs. The values of I 0 /I at 648 nm are proportional to the concentrations of Hg 2+ ion in the range from 0.00075 to 5.0 μM and of lambda-cyhalothrin in the range from 0.01 to 10 μM with detection limits of 0.0003 and 0.0075 μM for Hg 2+ ion and lambda-cyhalothrin, respectively. The practical application of the probe was successfully demonstrated by analyzing Hg 2+ ion and lambda-cyhalothrin in water samples. In addition, Au NCs used as probes for imaging of Simplicillium fungal cells. These results indicated that the as-synthesized Au NCs have proven to be promising fluorescent material for the sensing of Hg 2+ ion and lambda-cyhalothrin in environmental and for imaging of microorganism cells in biomedical applications.

Light-Driven Au-WO3@C Janus Micromotors for Rapid Photodegradation of Dye Pollutants.

PubMed

Zhang, Qilu; Dong, Renfeng; Wu, Yefei; Gao, Wei; He, Zihan; Ren, Biye

2017-02-08

A novel light-driven Au-WO 3 @C Janus micromotor based on colloidal carbon WO 3 nanoparticle composite spheres (WO 3 @C) prepared by one-step hydrothermal treatment is described. The Janus micromotors can move in aqueous media at a speed of 16 μm/s under 40 mW/cm 2 UV light due to diffusiophoretic effects. The propulsion of such Au-WO 3 @C Janus micromotors (diameter ∼ 1.0 μm) can be generated by UV light in pure water without any external chemical fuels and readily modulated by light intensity. After depositing a paramagnetic Ni layer between the Au layer and WO 3 , the motion direction of the micromotor can be precisely controlled by an external magnetic field. Such magnetic micromotors not only facilitate recycling of motors but also promise more possibility of practical applications in the future. Moreover, the Au-WO 3 @C Janus micromotors show high sensitivity toward extremely low concentrations of sodium-2,6-dichloroindophenol (DCIP) and Rhodamine B (RhB). The moving speed of motors can be significantly accelerated to 26 and 29 μm/s in 5 × 10 -4 wt % DCIP and 5 × 10 -7 wt % RhB aqueous solutions, respectively, due to the enhanced diffusiophoretic effect, which results from the rapid photocatalytic degradation of DCIP and RhB by WO 3 . This photocatalytic acceleration of the Au-WO 3 @C Janus micromotors confirms the self-diffusiophoretic mechanism and opens an opportunity to tune the motility of the motors. This work also offers the light-driven micromotors a considerable potential for detection and rapid photodegradation of dye pollutants in water.

Tunable synthesis and acetylation of dendrimer-entrapped or dendrimer-stabilized gold-silver alloy nanoparticles.

PubMed

Liu, Hui; Shen, Mingwu; Zhao, Jinglong; Guo, Rui; Cao, Xueyan; Zhang, Guixiang; Shi, Xiangyang

2012-06-01

In this study, amine-terminated generation 5 poly(amidoamine) dendrimers were used as templates or stabilizers to synthesize dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy nanoparticles (NPs) with different gold atom/silver atom/dendrimer molar ratios with the assistance of sodium borohydride reduction chemistry. Following a one-step acetylation reaction to transform the dendrimer terminal amines to acetyl groups, a series of dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs with terminal acetyl groups were formed. The formed Au-Ag alloy NPs before and after acetylation reaction were characterized using different techniques. We showed that the optical property and the size of the bimetallic NPs were greatly affected by the metal composition. At the constant total metal atom/dendrimer molar ratio, the size of the alloy NPs decreased with the gold content. The formed Au-Ag alloy NPs were stable at different pH (pH 5-8) and temperature (4-50°C) conditions. X-ray absorption coefficient measurements showed that the attenuation of the binary NPs was dependent on both the gold content and the surface modification. With the increase of gold content in the binary NPs, their X-ray attenuation intensity was significantly enhanced. At a given metal composition, the X-ray attenuation intensity of the binary NPs was enhanced after acetylation. Cytotoxicity assays showed that after acetylation, the cytocompatibility of Au-Ag alloy NPs was significantly improved. With the controllable particle size and optical property, metal composition-dependent X-ray attenuation characteristics, and improved cytocompatibility after acetylation, these dendrimer-entrapped or dendrimer-stabilized Au-Ag alloy NPs should have a promising potential for CT imaging and other biomedical applications. Copyright © 2012 Elsevier B.V. All rights reserved.

Controlled assembly and single electron charging of monolayer protected Au144 clusters: an electrochemistry and scanning tunneling spectroscopy study

NASA Astrophysics Data System (ADS)

Bodappa, Nataraju; Fluch, Ulrike; Fu, Yongchun; Mayor, Marcel; Moreno-García, Pavel; Siegenthaler, Hans; Wandlowski, Thomas

2014-11-01

Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles.Single gold particles may serve as room temperature single electron memory units because of their size dependent electronic level spacing. Here, we present a proof-of-concept study by electrochemically controlled scanning probe experiments performed on tailor-made Au particles of narrow dispersity. In particular, the charge transport characteristics through chemically synthesized hexane-1-thiol and 4-pyridylbenzene-1-thiol mixed monolayer protected Au144 clusters (MPCs) by differential pulse voltammetry (DPV) and electrochemical scanning tunneling spectroscopy (EC-STS) are reported. The pyridyl groups exposed by the Au-MPCs enable their immobilization on Pt(111) substrates. By varying the humidity during their deposition, samples coated by stacks of compact monolayers of Au-MPCs or decorated with individual, laterally separated Au-MPCs are obtained. DPV experiments with stacked monolayers of Au144-MPCs and EC-STS experiments with laterally separated individual Au144-MPCs are performed both in aqueous and ionic liquid electrolytes. Lower capacitance values were observed for individual clusters compared to ensemble clusters. This trend remains the same irrespective of the composition of the electrolyte surrounding the Au144-MPC. However, the resolution of the energy level spacing of the single clusters is strongly affected by the proximity of neighboring particles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03793f

Enhanced catalyst activity by decorating of Au on Ag@Cu2O nanoshell

NASA Astrophysics Data System (ADS)

Chen, Lei; Liu, Maomao; Zhao, Yue; Kou, Qiangwei; Wang, Yaxin; Liu, Yang; Zhang, Yongjun; Yang, Jinghai; Jung, Young Mee

2018-03-01

We successfully synthesized Au-decorated Ag@Cu2O heterostructures via a simple galvanic replacement method. As the Au precursor concentration increased, the density of the Au nanoparticles (NPs) on the Ag@Cu2O surface increased, which changed the catalytic activity of the Ag@Cu2O-Au structure. The combination of Au, Ag, and Cu2O exhibited excellent catalytic properties, which can further effect on the catalyst activity of the Ag@Cu2O-Au structure. In addition, the proposed Ag@Cu2O-Au nanocomposite was used to transform the organic, toxic pollutant, 4-nitrophenol (4-NP), into its nontoxic and medicinally important amino derivative via a catalytic reduction to optimize the material performance. The proposed Au-decorated Ag@Cu2O exhibited excellent catalytic activity, and the catalytic reduction time greatly decreased (5 min). Thus, three novel properties of Ag@Cu2O-Au, i.e., charge redistribution and transfer, adsorption, and catalytic reduction of organic pollutants, were ascertained for water remediation. The proposed catalytic properties have potential applications for photocatalysis and localized surface plasmon resonance (LSPR)- and peroxidase-like catalysis.

Self-healing gold mirrors and filters at liquid-liquid interfaces

NASA Astrophysics Data System (ADS)

Smirnov, Evgeny; Peljo, Pekka; Scanlon, Micheál D.; Gumy, Frederic; Girault, Hubert H.

2016-03-01

The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of ``floating islands'' of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing tetrathiafulvalene with neocuproine as the AuNP capping ligand in the nanofilm. These interfacial nanofilms formed with neocuproine and 38 nm mean diameter AuNPs, at monolayer surface coverages and above, were black due to aggregation and broadband absorbance.The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of ``floating islands'' of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing tetrathiafulvalene with neocuproine as the AuNP capping ligand in the nanofilm. These interfacial nanofilms formed with neocuproine and 38 nm mean diameter AuNPs, at monolayer surface coverages and above, were black due to aggregation and broadband absorbance. Electronic supplementary information (ESI) available: Interfacial tension measurements for various water-organic solvent systems, step-by-step optical microscopy and SEM characterization of the obtained film, optical photographs of all tested solvents and molecules, and influence of the interfacial tension on optical responses of AuNPs assemblies. See DOI: 10.1039/c6nr00371k

Size-controlled synthesis of gold bipyramids using an aqueous mixture of CTAC and salicylate anions as the soft template.

PubMed

Yoo, Hyojong; Jang, Min Hoon

2013-08-07

One-dimensional (1D) gold (Au) bipyramids are successfully synthesized through a facile seed-mediated method using cetyltrimethylammonium chloride (CTAC), Au seed nanoparticles, Ag(+) ions, and ascorbic acid. The length and optical properties of the synthesized Au bipyramids are controlled with precision by varying the amount of salicylate anions (Sal(-)) added during the synthesis. The micelles formed from CTA(+)-Sal(-) mixtures in aqueous solutions act as effective templates for the size-controlled synthesis of 1D nanocrystals.

Electrochemical Recovery of Gold from Waste Electric and Electronic Equipment Using Circulating Particulate Bed Reactor (CPBE)

NASA Astrophysics Data System (ADS)

Ravinder, T.; Ali, U. F. M.; Ridwan, F. M.; Ibrahim, N.; Azmi, N. H.

2017-06-01

The utilization of electrochemical process recovery involving low reactant concentrations of metal requires electrodes with high mass transport rates and specific surface areas. This is essential to increase cross-sectional current densities whilst optimizing the capital and operating costs. Experimental results demonstrated that Circulating Particulate Bed Reactor (CPBE) is suitable for the recovery of low concentrations of gold from aqueous chloride solution containing {{AuCl}}4- and {{AuCl}}2- of less than 0.5 mol m-3(< 102 g m-3). Elemental gold was successfully obtained on 0.5-1 mm gr particles in an electrochemical reactor incorporating a cation- permeable membrane and operated in bath recycle mode. Depletion to concentration < 5 × 10-3 mol m-3 (< 1 g m-3) appeared to be mass transport controlled at an applied potential of +0.20 V (SCE), specific electrical energy consumption (SEEC) of ca. 800-1300 kWh h (tonne Au)-1 for cell voltages (U) of 2.0-3.0 V, and fractional current efficiencies of ca. 0.95. However, atomic absorption and UV spectrophotometry established that as the ([{{AuCl}}4-+[{{AuCl}}2-]) concentration decayed, the [{{AuCl}}4-]:[{{AuCl}}2-] molar ratio changed. A multi-step mechanism for reduction of {{AuCl}}4- ions explained this behavior in terms of changing overpotentials for {{AuCl}}4- and {{AuCl}}2- reduction as total dissolved gold concentration decreased. In addition, SEM images confirmed that adherent and coherent Au deposits were achieved with CPBE for Au deposition under mass transport control at 0.20 V (SCE).

One-pot green synthesis of luminescent gold nanoparticles using imidazole derivative of chitosan.

PubMed

Nazirov, Alexander; Pestov, Alexander; Privar, Yuliya; Ustinov, Alexander; Modin, Evgeny; Bratskaya, Svetlana

2016-10-20

Water soluble luminescent gold nanoparticles with average size 2.3nm were for the first time synthesized by completely green method of Au(III) reduction using chitosan derivative-biocompatible nontoxic N-(4-imidazolyl)methylchitosan (IMC) as both reducing and stabilizing agent. Reduction of Au(III) to gold nanoparticles in IMC solution is a slow process, in which coordination power of biopolymer controls both reducing species concentration and gold crystal growth rate. Gold nanoparticles formed in IMC solution do not manifest surface plasmon resonance, but exhibit luminescence at 375nm under UV light excitation at 230nm. Due to biological activity of imidazolyl-containing polymers and their ability to bind proteins and drugs, the obtained ultra-small gold nanoparticles can find an application for biomolecules detection, bio-imaging, drug delivery, and catalysis. Very high catalytic activity (as compared to gold nanoparticles obtained by other green methods) was found for Au/IMC nanoparticles in the model reaction of p-nitrophenol reduction providing complete conversion of p-nitrophenol to p-aminophenol within 180-190s under mild conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Single cytidine units-templated syntheses of multi-colored water-soluble Au nanoclusters

NASA Astrophysics Data System (ADS)

Jiang, Hui; Zhang, Yuanyuan; Wang, Xuemei

2014-08-01

Ultra-small metallic nanoparticles, or so-called ``nanoclusters'' (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications.Ultra-small metallic nanoparticles, or so-called ``nanoclusters'' (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications. Electronic supplementary information (ESI) available: The feed amount for preparation of Au NCs, photophysical properties of Au NCs, the FL spectra under different pH and reaction time, and XPS results are included. See DOI: 10.1039/c4nr02180k

Atomic scale origins of sub-band gap optical absorption in gold-hyperdoped silicon

NASA Astrophysics Data System (ADS)

Ferdous, Naheed; Ertekin, Elif

2018-05-01

Gold hyperdoped silicon exhibits room temperature sub band gap optical absorption, with potential applications as infrared absorbers/detectors and impurity band photovoltaics. We use first-principles density functional theory to establish the origins of the sub band gap response. Substitutional gold AuSi and substitutional dimers AuSi - AuSi are found to be the energetically preferred defect configurations, and AuSi gives rise to partially filled mid-gap defect bands well offset from the band edges. AuSi is predicted to offer substantial sub-band gap absorption, exceeding that measured in prior experiments by two orders of magnitude for similar Au concentration. This suggests that in experimentally realized systems, in addition to AuSi, the implanted gold is accommodated by the lattice in other ways, including other defect complexes and gold precipitates. We further identify that it is energetically favorable for isolated AuSi to form AuSi - AuSi, which by contrast do not exhibit mid-gap states. The formation of dimers and other complexes could serve as nuclei in the earliest stages of Au precipitation, which may be responsible for the observed rapid deactivation of sub-band gap response upon annealing.

New pathway to prepare gold nanoparticles and their applications in catalysis and surface-enhanced Raman scattering.

PubMed

Chang, Chun-Chao; Yang, Kuang-Hsuan; Liu, Yu-Chuan; Hsu, Ting-Chu

2012-05-01

As shown in the literature, additional energies are necessary for the reduction of positively charged noble metal ions to prepare metal nanoparticles (NPs). In this work, we report a new green pathway to prepare Au NPs in neutral 0.1M NaCl aqueous solutions from bulk Au substrates without addition of any stabilizer and reductant just via aid of natural chitosan (Ch) at room temperature. Au- and Ch-containing complexes in aqueous solution were electrochemically prepared. The role of Ch is just an intermediate to perform electron transfer with Au NPs. The stability of these prepared Au NPs is well maintained by Au NPs themselves with slightly positively charged Au remained on the surface of Au NPs. The particle size of prepared spherical Au (111) NPs is ca. 15 nm in diameter. Moreover, increasing the pH of preparation solutions can be contributive to preparing concentrated Au NPs in solutions. The prepared Au NPs are surface-enhanced Raman scattering (SERS)-active for probe molecules of Rhodamine 6G. They also demonstrate significantly catalytic activity for decomposition of acetaldehyde in rice wine. Copyright © 2012 Elsevier B.V. All rights reserved.

Toward hybrid Au nanorods @ M (Au, Ag, Pd and Pt) core-shell heterostructures for ultrasensitive SERS probes

NASA Astrophysics Data System (ADS)

Xie, Xiaobin; Gao, Guanhui; Kang, Shendong; Lei, Yanhua; Pan, Zhengyin; Shibayama, Tamaki; Cai, Lintao

2017-06-01

Being able to precisely control the morphologies of noble metallic nanostructures is of essential significance for promoting the surface-enhanced Raman scattering (SERS) effect. Herein, we demonstrate an overgrowth strategy for synthesizing Au @ M (M = Au, Ag, Pd, Pt) core-shell heterogeneous nanocrystals with an orientated structural evolution and highly improved properties by using Au nanorods as seeds. With the same reaction condition system applied, we obtain four well-designed heterostructures with diverse shapes, including Au concave nanocuboids (Au CNs), Au @ Ag crystalizing face central cube nanopeanuts, Au @ Pd porous nanocuboids and Au @ Pt nanotrepangs. Subsequently, the exact overgrowth mechanism of the above heterostructural building blocks is further analysed via the systematic optimiziation of a series of fabrications. Remarkably, the well-defined Au CNs and Au @ Ag nanopeanuts both exhibit highly promoted SERS activity. We expect to be able to supply a facile strategy for the fabrication of multimetallic heterogeneous nanostructures, exploring the high SERS effect and catalytic activities.

Controlling Shape and Plasmon Resonance of Pt-Etched Au@Ag Nanorods.

PubMed

Ye, Rongkai; Zhang, Yanping; Chen, Yuyu; Tang, Liangfeng; Wang, Qiong; Wang, Qianyu; Li, Bishan; Zhou, Xuan; Liu, Jianyu; Hu, Jianqiang

2018-05-22

Pt-based catalysts with novel structure have attracted great attention due to their outstanding performance. In this work, H 2 PtCl 6 was used as both precursor and etching agent to realize the shape-controlled synthesis of Pt-modified Au@Ag nanorods (NRs). During the synthesis, the as-prepared Ag shell played a crucial role in both protecting the Au NRs from being etched away by PtCl 6 2- and leading to an unusual growth mode of Pt component. The site-specified etching and/or growth depended on the concentration of H 2 PtCl 6 , where high-yield core-shell structure or dumbbell-like structure could be obtained. The shape-controlled synthesis also led to a tunable longitudinal surface plasmon resonance from ca. 649 to 900 nm. Meanwhile, the core-shell Pt-modified Au@Ag NRs showed approximately 4-fold enhancement in catalytic reduction reaction of p-nitrophenol than that of the Au NRs, suggesting the great potential for photocatalytic reaction.

Communication Dependent Control of Multi-Vehicle Formations

DTIC Science & Technology

2016-05-11

On Maximizing the Second Smallest Eigen- value of a State-Dependent Graph Laplacian,” IEEE Transactions on Au- tomatic Control, vol. 51, no. 1, pp...Collective Motion With Limited Communication,” IEEE Transactions on Au- tomatic Control, vol. 53, no. 3, pp. 706–719, 2008. [Online]. Available: http

Modeling, Fabrication and Characterization of Scalable Electroless Gold Plated Nanostructures for Enhanced Surface Plasmon Resonance

NASA Astrophysics Data System (ADS)

Jang, Gyoung Gug

The scientific and industrial demand for controllable thin gold (Au) film and Au nanostructures is increasing in many fields including opto-electronics, photovoltaics, MEMS devices, diagnostics, bio-molecular sensors, spectro-/microscopic surfaces and probes. In this study, a novel continuous flow electroless (CF-EL) Au plating method is developed to fabricate uniform Au thin films in ambient condition. The enhanced local mass transfer rate and continuous deposition resulting from CF-EL plating improved physical uniformity of deposited Au films and thermally transformed nanoparticles (NPs). Au films and NPs exhibited improved optical photoluminescence (PL) and surface plasmon resonance (SPR), respectively, relative to batch immersion EL (BI-EL) plating. Suggested mass transfer models of Au mole deposition are consistent with optical feature of CF-EL and BI-EL films. The prototype CF-EL plating system is upgraded an automated scalable CF-EL plating system with real-time transmission UV-vis (T-UV) spectroscopy which provides the advantage of CF-EL plating, such as more uniform surface morphology, and overcomes the disadvantages of conventional EL plating, such as no continuous process and low deposition rate, using continuous process and controllable deposition rate. Throughout this work, dynamic morphological and chemical transitions during redox-driven self-assembly of Ag and Au film on silica surfaces under kinetic and equilibrium conditions are distinguished by correlating real-time T-UV spectroscopy with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) measurements. The characterization suggests that four previously unrecognized time-dependent physicochemical regimes occur during consecutive EL deposition of silver (Ag) and Au onto tin-sensitized silica surfaces: self-limiting Ag activation; transitory Ag NP formation; transitional Au-Ag alloy formation during galvanic replacement of Ag by Au; and uniform morphology formation under controlled hydraulic conditions. A method to achieve the time-resolved optical profile of EL Au plating was devised and provided a new transitional EL Au film growth model which validated mass transfer model prediction of the deposited thickness of ≤100 nm thin films. As a part of the project, validation of mass transfer model, a spectrophotometric method for quantitative analysis of metal ion is developed that improves the limit of detection comparable to conventional instrumental analysis. The present work suggests that modeling, fabrication and characterization of this novel CF-EL plating method is performed to achieve an ultimate purpose: developing a reliable, inexpensive wet chemical process for controlled metal thin film and nanostructure fabrication.

Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

NASA Astrophysics Data System (ADS)

Tiruvalam, Ram Chandra

Nanoscale gold has been shown to possess an intriguing combination of unexpected optical, photochemical and catalytic properties. The ability to control the size, shape, morphology, composition and dispersion of gold-based nanostructures is key to optimizing their performance for nanotechnology applications. The advanced electron microscopy studies described in this thesis analyze three important aspects of gold and gold-palladium alloy nanoparticles: namely, (i) the ability to synthesize gold nanoparticles of controlled size and shape in an aqueous medium; (ii) the colloidal preparation of designer gold-palladium alloys for selective oxidation catalysis; and (iii) the ability to disperse gold as finely and homogeneously as possible on a metal oxide or carbon support. The ability to exploit the nanoscale properties of gold for various engineering applications often depends on our ability to control size and shape of the nanoscale entity by careful manipulation of the synthesis parameters. We have explored an aqueous based synthesis route, using oleylamine as both a reductant and surfactant, for preparing gold nanostructures. By systematically varying synthesis parameters such as oleylamine concentration, reaction temperature, and aging time it is possible to identify processing regimens that generate Au nanostructures having either pseudo-spherical, faceted polyhedral, nanostar or wire shaped morphologies. Furthermore, by quenching the reaction partway through it is possible to create a class of metastable Au-containing structures such as nanocubes, nanoboxes and nanowires. Possible formation mechanisms for these gold based nano-objects are discussed. There is a growing interest in using supported bimetallic AuPd alloy nanoparticles for selective oxidation reactions. In this study, a systematic series of size controlled AuPd bimetallic particles have been prepared by colloidal synthesis methods. Particles having random alloy structures, as well as `designer' particles with Pd-shell/Au-core and Au-shell/Pd-core morphologies, have been prepared and immobilized on both activated carbon and TiO2 supports. These have subsequently been compared as catalysts for the direct production of H2O2 and for benzyl alcohol oxidation in an attempt to elucidate the optimum particle morphology/support combination for both these reactions. Aberration corrected analytical electron microscopy has been used extensively to characterize these sol-immobilized materials. In particular, the STEM -HAADF technique has provided invaluable new (and often unexpected) information on the atomic structure, elemental distribution within particles, and compositional variations between particles for these controlled catalyst preparations. In addition, we have been able to compare their differing thermal stability and sintering behaviors, and to demonstrate that they have quite varying wetting interactions with activated carbon and TiO2 supports. Over the course of their lifetime, many supported metal catalysts exposed to elevated temperatures tend to de-activate by nanoparticle sintering, which decreases the overall exposed metal surface area and the number of active sites available for catalysis. It is sometimes desirable to devise chemical re-dispersion treatments whereby the mean size of the particles is reduced and the catalytic activity regenerated. In this work, the possibility of re-dispersing gold nanoparticles by a simple low temperature methyl iodide (CH3 I) treatment has been investigated. A variety of characterization techniques, including EXAFS, XRD, XPS, UV-DRS and STEM-HAADF imaging has been applied to samples before and after CH3 I treatment, in an attempt to determine the efficacy of the re-dispersion method. It is shown that re-dispersion of Au nanoparticles on activated carbon, graphite, Al2 O3 and TiO2 substrates is possible to varying degrees. A complete re-dispersion of `bulk' gold nanoparticles down to the atomic scale has been achieved on activated carbon and graphite substrates, with the exclusive formation of isolated gold atoms, dimeric species, and sub-nm clusters.

Synthesis of one-dimensional gold nanostructures and the electrochemical application of the nanohybrid containing functionalized graphene oxide for cholesterol biosensing.

PubMed

Nandini, Seetharamaiah; Nalini, Seetharamaiah; Reddy, M B Madhusudana; Suresh, Gurukar Shivappa; Melo, Jose Savio; Niranjana, Pathappa; Sanetuntikul, Jakkid; Shanmugam, Sangaraju

2016-08-01

This manuscript reports a new approach for the synthesis of one dimensional gold nanostructure (AuNs) and its application in the development of cholesterol biosensor. Au nanostructures have been synthesized by exploiting β-diphenylalanine (β-FF) as an sacrificial template, whereas the Au nanoparticles (AuNPs) were synthesized by ultrasound irradiation. X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive analysis of X-rays (EDAX) have been employed to characterize the morphology and composition of the prepared samples. With the aim to develop a highly sensitive cholesterol biosensor, cholesterol oxidase (ChOx) was immobilized on AuNs which were appended on the graphite (Gr) electrode via chemisorption onto thiol-functionalized graphene oxide (GO-SH). This Gr/GO-SH/AuNs/ChOx biosensor has been characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy and chronoamperometry. CV results indicated a direct electron transfer between the enzyme and the electrode surface. A new potentiostat intermitant titration technique (PITT) has been studied to determine the diffusion coefficient and maxima potential value. The proposed biosensor showed rapid response, high sensitivity, wide linear range and low detection limit. Furthermore, our AuNs modified electrode showed excellent selectivity, repeatability, reproducibility and long term stability. The proposed electrode has also been used successfully to determine cholesterol in serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species.

PubMed

Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

2017-02-10

In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters.

Photoluminescent Gold Nanoclusters in Cancer Cells: Cellular Uptake, Toxicity, and Generation of Reactive Oxygen Species

PubMed Central

Matulionyte, Marija; Dapkute, Dominyka; Budenaite, Laima; Jarockyte, Greta; Rotomskis, Ricardas

2017-01-01

In recent years, photoluminescent gold nanoclusters have attracted considerable interest in both fundamental biomedical research and practical applications. Due to their ultrasmall size, unique molecule-like optical properties, and facile synthesis gold nanoclusters have been considered very promising photoluminescent agents for biosensing, bioimaging, and targeted therapy. Yet, interaction of such ultra-small nanoclusters with cells and other biological objects remains poorly understood. Therefore, the assessment of the biocompatibility and potential toxicity of gold nanoclusters is of major importance before their clinical application. In this study, the cellular uptake, cytotoxicity, and intracellular generation of reactive oxygen species (ROS) of bovine serum albumin-encapsulated (BSA-Au NCs) and 2-(N-morpholino) ethanesulfonic acid (MES)-capped photoluminescent gold nanoclusters (Au-MES NCs) were investigated. The results showed that BSA-Au NCs accumulate in cells in a similar manner as BSA alone, indicating an endocytotic uptake mechanism while ultrasmall Au-MES NCs were distributed homogeneously throughout the whole cell volume including cell nucleus. The cytotoxicity of BSA-Au NCs was negligible, demonstrating good biocompatibility of such BSA-protected Au NCs. In contrast, possibly due to ultrasmall size and thin coating layer, Au-MES NCs exhibited exposure time-dependent high cytotoxicity and higher reactivity which led to highly increased generation of reactive oxygen species. The results demonstrate the importance of the coating layer to biocompatibility and toxicity of ultrasmall photoluminescent gold nanoclusters. PMID:28208642

Poly(methacrylic acid)-Coated Gold Nanoparticles: Functional Platforms for Theranostic Applications.

PubMed

Yilmaz, Gokhan; Demir, Bilal; Timur, Suna; Becer, C Remzi

2016-09-12

The integration of drugs with nanomaterials have received significant interest in the efficient drug delivery systems. Conventional treatments with therapeutically active drugs may cause undesired side effects and, thus, novel strategies to perform these treatments with a combinatorial approach of therapeutic modalities are required. In this study, polymethacrylic acid coated gold nanoparticles (AuNP-PMAA), which were synthesized with reversible addition-fragmentation chain transfer (RAFT) polymerization, were combined with doxorubicin (DOX) as a model anticancer drug by creating a pH-sensitive hydrazone linkage in the presence of cysteine (Cys) and a cross-linker. Drug-AuNP conjugates were characterized via spectrofluorimetry, dynamic light scattering and zeta potential measurements as well as X-ray photoelectron spectroscopy. The particle size of AuNP-PMAA and AuNP-PMAA-Cys-DOX conjugate were calculated as found as 104 and 147 nm, respectively. Further experiments with different pH conditions (pH 5.3 and 7.4) also showed that AuNP-PMAA-Cys-DOX conjugate could release the DOX in a pH-sensitive way. Finally, cell culture applications with human cervix adenocarcinoma cell line (HeLa cells) demonstrated effective therapeutic impact of the final conjugate for both chemotherapy and radiation therapy by comparing free DOX and AuNP-PMAA independently. Moreover, cell imaging study was also an evidence that AuNP-PMAA-Cys-DOX could be a beneficial candidate as a diagnostic agent.

Broadening the photoresponsive activity of anatase titanium dioxide particles via decoration with partial gold shells.

PubMed

Khantamat, Orawan; Li, Chien-Hung; Liu, Si-Ping; Liu, Tingting; Lee, Han Ju; Zenasni, Oussama; Lee, Tai-Chou; Cai, Chengzhi; Lee, T Randall

2018-03-01

Titanium dioxide (TiO 2 ) has gained increasing interest in materials research due to its outstanding properties and promising applications in a wide range of fields. From this perspective, we report the synthesis of custom-designed anatase TiO 2 submicrometer particles coated with partial Au shells (ATiO 2 -AuShl). The synthetic strategy used herein yields uniformly shaped monodisperse particles. Amorphous TiO 2 core particles were synthesized using template-free oxidation and hydrolysis of titanium nitride (TiN); subsequent hydrothermal treatment generated anatase TiO 2 (ATiO 2 ) particles. Coating ATiO 2 particles with partial Au shells was accomplished using a simple seeded-growth method. Evaluation of the optical properties of these ATiO 2 -AuShl particles showed that these submicrometer composites exhibited an intense absorption peak for TiO 2 in the UV region (∼326 nm) and a broad extinction band in the visible range (∼650 nm) arising from the incomplete Au shell. These ATiO 2 -AuShl composite particles provide a unique and effective means for broadening the optical response of TiO 2 -based nano- and micron-scale materials. The simplicity of our synthetic method should broaden the application of ATiO 2 -AuShl particles in various visible light-driven technologies. Copyright © 2017 Elsevier Inc. All rights reserved.

Novel electrochemical redox-active species: one-step synthesis of polyaniline derivative-Au/Pd and its application for multiplexed immunoassay

NASA Astrophysics Data System (ADS)

Wang, Liyuan; Feng, Feng; Ma, Zhanfang

2015-11-01

Electrochemical redox-active species play crucial role in electrochemically multiplexed immunoassays. A one-pot method for synthesizing four kinds of new electrochemical redox-active species was reported using HAuCl4 and Na2PdCl4 as dual oxidating agents and aniline derivatives as monomers. The synthesized polyaniline derivative-Au/Pd composites, namely poly(N-methyl-o-benzenediamine)-Au/Pd, poly(N-phenyl-o-phenylenediamine)-Au/Pd, poly(N-phenyl-p-phenylenediamine)-Au/Pd and poly(3,3’,5,5’-tetramethylbenzidine)-Au/Pd, exhibited electrochemical redox activity at -0.65 V, -0.3 V, 0.12 V, and 0.5 V, respectively. Meanwhile, these composites showed high H2O2 electrocatalytic activity because of the presence of Au/Pd. The as-prepared composites were used as electrochemical immunoprobes in simultaneous detection of four tumor biomarkers (carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA199), carbohydrate antigen 72-4 (CA724), and alpha fetoprotein (AFP)). This immunoassay shed light on potential applications in simultaneous gastric cancer (related biomarkers: CEA, CA199, CA724) and liver cancer diagnosis (related biomarkers: CEA, CA199, AFP). The present strategy to the synthesize redox species could be easily extended to other polymers such as polypyrrole derivatives and polythiophene derivatives. This would be of great significance in the electrochemical detection of more analytes.

Solvothermal synthesis of Au@Fe3O4 nanoparticles for antibacterial applications

NASA Astrophysics Data System (ADS)

Kelgenbaeva, Zhazgul; Abdullaeva, Zhypargul; Murzubraimov, Bektemir

2018-04-01

We present Au@Fe3O4 nanoparticles obtained from Fe nanoparticles and HAuCl4 using a simple solvothermal method. Trisodium citrate (C6H5Na3O7*2H2O) served as a reducing agent for Au. X-ray diffraction analysis, electronic microscopes and energy-dispersive X-ray spectroscopy revealed cubic structure, elemental composition (Au, Fe and O) and spherical shape of nanoparticles. Antibacterial activity of the sample was tested against E. coli bacteria and obtained results were discussed.

Mechanical control of the plasmon coupling with Au nanoparticle arrays fixed on the elastomeric film via chemical bond

NASA Astrophysics Data System (ADS)

Bedogni, Elena; Kaneko, Satoshi; Fujii, Shintaro; Kiguchi, Manabu

2017-03-01

We have fabricated Au nanoparticle arrays on the flexible poly(dimethylsiloxane) (PDMS) film. The nanoparticles were bound to the film via a covalent bond by a ligand exchange reaction. Thanks to the strong chemical bonding, highly stable and uniformly dispersed Au nanoparticle arrays were fixed on the PDMS film. The Au nanoparticle arrays were characterized by the UV-vis, scanning electron microscope (SEM) and surface enhanced Raman scattering (SERS). The UV-vis and SEM measurements showed the uniformity of the surface-dispersed Au nanoparticles, and SERS measurement confirmed the chemistry of the PDMS film. Reflecting the high stability and the uniformity of the Au nanoparticle arrays, the plasmon wavelength of the Au nanoparticles reversely changed with modulation of the interparticle distance, which was induced by the stretching of the PDMS film. The plasmon wavelength linearly decreased from 664 to 591 nm by stretching of 60%. The plasmon wavelength shift can be explained by the change in the strength of the plasmon coupling which is mechanically controlled by the mechanical strain.

Enhanced Delivery of Gold Nanoparticles with Therapeutic Potential for Targeting Human Brain Tumors

NASA Astrophysics Data System (ADS)

Etame, Arnold B.

The blood brain barrier (BBB) remains a major challenge to the advancement and application of systemic anti-cancer therapeutics into the central nervous system. The structural and physiological delivery constraints of the BBB significantly limit the effectiveness of conventional chemotherapy, thereby making systemic administration a non-viable option for the vast majority of chemotherapy agents. Furthermore, the lack of specificity of conventional systemic chemotherapy when applied towards malignant brain tumors remains a major shortcoming. Hence novel therapeutic strategies that focus both on targeted and enhanced delivery across the BBB are warranted. In recent years nanoparticles (NPs) have emerged as attractive vehicles for efficient delivery of targeted anti-cancer therapeutics. In particular, gold nanoparticles (AuNPs) have gained prominence in several targeting applications involving systemic cancers. Their enhanced permeation and retention within permissive tumor microvasculature provide a selective advantage for targeting. Malignant brain tumors also exhibit transport-permissive microvasculature secondary to blood brain barrier disruption. Hence AuNPs may have potential relevance for brain tumor targeting. However, the permeation of AuNPs across the BBB has not been well characterized, and hence is a potential limitation for successful application of AuNP-based therapeutics within the central nervous system (CNS). In this dissertation, we designed and characterized AuNPs and assessed the role of polyethylene glycol (PEG) on the physical and biological properties of AuNPs. We established a size-dependent permeation profile with respect to core size as well as PEG length when AuNPs were assessed through a transport-permissive in-vitro BBB. This study was the first of its kind to systematically examine the influence of design on permeation of AuNPs through transport-permissive BBB. Given the significant delivery limitations through the non-transport permissive and intact BBB, we also assessed the role of magnetic resonance imaging (MRI) guided focused ultrasound (MRgFUS) disruption of the BBB in enhancing permeation of AuNPs across the intact BBB and tumor BBB in vivo. MRgFUS is a novel technique that can transiently increase BBB permeability thereby allowing delivery of therapeutics into the CNS. We demonstrated enhanced delivery of AuNPs with therapeutic potential into the CNS via MRgFUS. Our study was the first to establish a definitive role for MRgFUS in delivering AuNPs into the CNS. In summary, this thesis describes results from a series of research projects that have contributed to our understanding of the influence of design features on AuNP permeation through the BBB and also the potential role of MRgFUS in AuNP permeation across the BBB.

Thermally stable silica-coated hydrophobic gold nanoparticles.

PubMed

Kanehara, Masayuki; Watanabe, Yuka; Teranishi, Toshiharu

2009-01-01

We have successfully developed a method for silica coating on hydrophobic dodecanethiol-protected Au nanoparticles with coating thickness ranging from 10 to 40 nm. The formation of silica-coated Au nanoparticles could be accomplished via the preparation of hydrophilic Au nanoparticle micelles by cationic surfactant encapsulation in aqueous phase, followed by hydrolysis of tetraethylorthosilicate on the hydrophilic surface of gold nanoparticle micelles. Silica-coated Au nanoparticles exhibited quite high thermal stability, that is, no agglomeration of the Au cores could be observed after annealing at 600 degrees C for 30 min. Silica-coated Au nanoparticles could serve as a template to derive hollow nanoparticles. An addition of NaCN solution to silica-coated Au nanoparticles led the formation of hollow silica nanoparticles, which were redispersible in deionized water. The formation of the hollow silica nanoparticles results from the mesoporous structures of the silica shell and such a mesoporous structure is applicable to both catalyst support and drug delivery.

Wetting Behavior of Ternary Au-Ge-X (X = Sb, Sn) Alloys on Cu and Ni

NASA Astrophysics Data System (ADS)

Jin, S.; Valenza, F.; Novakovic, R.; Leinenbach, C.

2013-06-01

Au-Ge-based alloys are potential substitutes for Pb-rich solders currently used for high-temperature applications. In the present work, the wetting behavior of two Au-Ge-X (X = Sb, Sn) ternary alloys, i.e., Au-15Ge-17Sb and Au-13.7 Ge-15.3Sn (at.%), in contact with Cu and Ni substrates has been investigated. Au-13.7Ge-15.3Sn alloy showed complete wetting on both Cu and Ni substrates. Total spreading of Au-15Ge-17Sb alloy on Cu was also observed, while the final contact angle of this alloy on Ni was about 29°. Pronounced dissolution of Cu substrates into the solder alloys investigated was detected, while the formation of Ni-Ge intermetallic compounds at the interface of both solder/Ni systems suppressed the dissolution of Ni into the solder.

Effects of the physicochemical properties of gold nanostructures on cellular internalization

PubMed Central

Zhang, Jinchao; Wang, Paul C.; Liang, Xing-Jie

2015-01-01

Unique physicochemical properties of Au nanomaterials make them potential star materials in biomedical applications. However, we still know a little about the basic problem of what really matters in fabrication of Au nanomaterials which can get into biological systems, especially cells, with high efficiency. An understanding of how the physicochemical properties of Au nanomaterials affect their cell internalization is of significant interest. Studies devoted to clarify the functions of various properties of Au nanostructures such as size, shape and kinds of surface characteristics in cell internalization are under way. These fundamental investigations will give us a foundation for constructing Au nanomaterial-based biomedical devices in the future. In this review, we present the current advances and rationales in study of the relationship between the physicochemical properties of Au nanomaterials and cell uptake. We also provide a perspective on the Au nanomaterial-cell interaction research. PMID:26813673

Spectroscopically forbidden infra-red emission in Au-vertical graphene hybrid nanostructures

NASA Astrophysics Data System (ADS)

Sivadasan, A. K.; Parida, Santanu; Ghosh, Subrata; Pandian, Ramanathaswamy; Dhara, Sandip

2017-11-01

Implementation of Au nanoparticles (NPs) is a subject for frontier plasmonic research due to its fascinating optical properties. Herein, the present study deals with plasmonic assisted emission properties of Au NPs-vertical graphene (VG) hybrid nanostructures. The influence of effective polarizability of Au NPs on the surface enhanced Raman scattering and luminescence properties is investigated. In addition, a remarkable infra-red emission in the hybrid nanostructures is observed and interpreted on the basis of intra-band transitions in Au NPs. The flake-like nanoporous VG structure is invoked for the generation of additional confined photons to impart additional momentum and a gradient of confined excitation energy towards initiating the intra-band transitions of Au NPs. Integrating Au plasmonic materials in three-dimensional VG nanostructures enhances the light-matter interactions. The present study provides a new adaptable plasmonic assisted pathway for optoelectronic and sensing applications.

Uniform integration of gold nanoparticles in PDMS microfluidics with 3D micromixing

NASA Astrophysics Data System (ADS)

SadAbadi, H.; Packirisamy, M.; Wuthrich, R.

2015-09-01

The integration of gold nanoparticles (AuNPs) on the surface of polydimethylsiloxane (PDMS) microfluidics for biosensing applications is a challenging task. In this paper we address this issue by integration of pre-synthesized AuNPs (in a microreactor) into a microfluidic system. This method explored the affinity of AuNPs toward the PDMS surface so that the pre-synthesized particles will be adsorbed onto the channel walls. AuNPs were synthesized inside a microreactor before integration. In order to improve the size uniformity of the synthesized AuNPs and also to provide full mixing of reactants, a 3D-micromixer was designed, fabricated and then integrated with the microreactor in a single platform. SEM and UV/Vis spectroscopy were used to characterize the AuNPs on the PDMS surface.

Estimation of spin contamination error in dissociative adsorption of Au2 onto MgO(0 0 1) surface: First application of approximate spin projection (AP) method to plane wave basis

NASA Astrophysics Data System (ADS)

Tada, Kohei; Koga, Hiroaki; Okumura, Mitsutaka; Tanaka, Shingo

2018-06-01

Spin contamination error in the total energy of the Au2/MgO system was estimated using the density functional theory/plane-wave scheme and approximate spin projection methods. This is the first investigation in which the errors in chemical phenomena on a periodic surface are estimated. The spin contamination error of the system was 0.06 eV. This value is smaller than that of the dissociation of Au2 in the gas phase (0.10 eV). This is because of the destabilization of the singlet spin state due to the weakening of the Au-Au interaction caused by the Au-MgO interaction.

Au/Ti resistors used for Nb/Pb-alloy Josephson junctions. II. Thermal stability

NASA Astrophysics Data System (ADS)

Murakami, Masanori; Kim, K. K.

1984-10-01

In the preceding paper bilayered Au/Ti resistors were found to have excellent electrical stability during storage at room temperature after preannealing at an elevated temperature, which is essential to design logic and memory circuits of Nb/Pb-alloy Josephson junction devices. The resistors could contact directly with the Pb-alloy control lines in which Pb and In atoms which are known to intermix easily with Au atoms are contained. Since Pb and In atoms in the control lines are separated from Au atoms of the resistors by thin Ti layers, thermal stability at the contacts is a major concern for use of the Au/Ti resistor material in the Josephson devices. In the present study, surface morphology change and diffusion mechanism at the resistor/control-line contacts were studied using x-ray diffraction and scanning electron microscopy for square-shaped Au/Ti resistors covered by Pb-In layers. The samples were isothermally annealed at temperatures ranging from 353 to 423 K. The diffusion did not occur immediately after annealing at these temperatures. After the incubation period, the interdiffusion was observed to initiate at the edges of the resistors facing to the center of the cathode. Significant amounts of the In atoms in the Pb-In layers were observed to diffuse into the Au layers of the resistors, forming AuIn2 compounds under the Ti layers. By measuring growth rates of the AuIn2 layers, the diffusion coefficients and the activation energy for the layer growth were determined. Also, by analyzing changes in the In concentration in the Pb-In layers during annealing, interdiffusion coefficients of In atoms in the Pb-In layers were determined using a computer simulation technique. The activation energy was about 1.1 eV. Since these diffusion coefficients were found to be very close to those determined previously in bulk materials, the diffusion kinetics is believed to be controlled by the lattice diffusion. Based on the present results, several methods to reduce the interdiffusion between Pb-alloy and Au/Ti resistors were proposed.

Green synthesis of gold nanoparticles using aqueous ethanol extract of Curcuma mangga rhizomes as reducing agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yee, Foo Yiing; Malek, Sri Nurestri Abd; Periasamy, Vengadesh

Green synthesis of gold nanoparticles (AuNPs) had been developed as an alternative to chemical and physical methods due to its simplicity, cost effectiveness and eco-friendliness. The high biocompatibility and biostability features of AuNPs have found importance in biomedical applications in recent years. In this study, aqueous ethanol extract of Curcuma mangga rhizomes which acts as reducing and stabilizing agent was used to synthesize stable AuNPs by bioreduction of chloroauric acid. The formation of AuNPs was highlighted by the color change of the suspension from light yellow to reddish purple. Time-evolution was monitored by UV-visible spectroscopy, while surface plasmon (SP) absorptionmore » band of the AuNPs suspension was observed at a maximum absorption of 540 nm. Hydrodynamic radii and size distribution of the AuNPs in the suspension were evaluated using dynamic light scattering (DLS) and zeta potential measurement demonstrated negative surface charge. The particle size was calculated in the range of 2-30 nm using High Resolution Transmission Electron Microscopy (HRTEM). The morphology and elemental composition were further determined by Field Effect Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy meanwhile was used to confirm the presence of AuNPs and functional groups involved in the gold bio-reduction process. Influence of the volume of extract and concentration of gold (III) chloride trihydrate (HAuCl{sub 4}.3H{sub 2}O) on the synthesis of AuNPs were also investigated. The results obtained indicate potential optimization and functionalization of AuNPs for future applications in bionanotechnology especially in the field of medicine.« less

Green synthesis of gold nanoparticles using aqueous ethanol extract of Curcuma mangga rhizomes as reducing agent

NASA Astrophysics Data System (ADS)

Yee, Foo Yiing; Periasamy, Vengadesh; Malek, Sri Nurestri Abd

2015-04-01

Green synthesis of gold nanoparticles (AuNPs) had been developed as an alternative to chemical and physical methods due to its simplicity, cost effectiveness and eco-friendliness. The high biocompatibility and biostability features of AuNPs have found importance in biomedical applications in recent years. In this study, aqueous ethanol extract of Curcuma mangga rhizomes which acts as reducing and stabilizing agent was used to synthesize stable AuNPs by bioreduction of chloroauric acid. The formation of AuNPs was highlighted by the color change of the suspension from light yellow to reddish purple. Time-evolution was monitored by UV-visible spectroscopy, while surface plasmon (SP) absorption band of the AuNPs suspension was observed at a maximum absorption of 540 nm. Hydrodynamic radii and size distribution of the AuNPs in the suspension were evaluated using dynamic light scattering (DLS) and zeta potential measurement demonstrated negative surface charge. The particle size was calculated in the range of 2-30 nm using High Resolution Transmission Electron Microscopy (HRTEM). The morphology and elemental composition were further determined by Field Effect Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray (EDX) spectroscopy. Fourier transform infrared (FTIR) spectroscopy meanwhile was used to confirm the presence of AuNPs and functional groups involved in the gold bio-reduction process. Influence of the volume of extract and concentration of gold (III) chloride trihydrate (HAuCl4.3H2O) on the synthesis of AuNPs were also investigated. The results obtained indicate potential optimization and functionalization of AuNPs for future applications in bionanotechnology especially in the field of medicine.

Facile preparation of surfactant-free Au NPs/RGO/Ni foam for degradation of 4-nitrophenol and detection of hydrogen peroxide.

PubMed

Liu, Y Y; Guo, X L; Zhao, L; Zhu, L; Chen, Z T; Chen, J; Zhang, Y; Sun, L T; Zhao, Y H

2018-06-08

The application of Au nanoparticles (Au NPs) often requires surface modification with chemical surfactants, which dramatically reduce the surface activity and increase the chemical contamination and cost of Au NPs. In this research, we have developed a novel Au NPs/reduced graphene oxide/Ni foam hybrid (Au NPs/RGO/NiF) by in situ reduction through ascorbic acid and replacement reaction. This method is green, facile and efficient. The Au NPs are free of chemical surfactants and are homogeneously distributed on the surface of the RGO/NiF. The as-prepared Au NPs/RGO/NiF hybrid is uniform, stable and exhibits not only a high reduction efficiency for the reduction of 4-nitrophenol with a catalytic kinetic constant of up to 0.46 min -1 (0.15 cm 3 catalysis) but also a sensitive and selective detection of H 2 O 2 with a detection limit of ∼1.60 μM.

Bio-prospective of Polyscias fruticosa leaf extract as redactor and stabilizer of gold nanoparticles formation

NASA Astrophysics Data System (ADS)

Yulizar, Y.; Ayun, Q.

2017-03-01

Metal nanoparticle is a great interest to researches due to its applications toward catalysis, sensors, and drug delivery. Biosynthesis of gold nanoparticles (AuNPs) using aqueous leaf extract of Polycias fruticosa (PFE) is reported in this article. PFE plays a role as reductor and stabilizer of AuNPs. The formation of PFE-AuNPs under radiation of natrium lamp for 15 min was monitored by UV - Vis spectrophotometer. The growth process and stability of PFE-AuNPs was observed from the colour and absorbance change in the wavelength range of 529-533 nm. The optimum synthesis condition of PFE-AuNPs was obtained at 0.06% (w/v) of PFE concentration. Size and its distribution of PFE-AuNPs were identified by particle size analyzer (PSA) as 35.02 nm and stable up until 21 days. The stable PFE-AuNPs was further characterized by Fourier transform infrared (FT-IR) spectroscopy to identify the functional group in phenolic compound of PFE interact with AuNps.

Exfoliation restacking route to Au nanoparticle-clay nanohybrids

NASA Astrophysics Data System (ADS)

Paek, Seung-Min; Jang, Jae-Up; Hwang, Seong-Ju; Choy, Jin-Ho

2006-05-01

A novel gold-pillared aluminosilicate (Au-PILC) were synthesized with positively charged gold nanoparticles capped by mercaptoammonium and exfoliated silicate layers. Gold nanoparticles were synthesized by NaBH4 reduction of AuCl4- in the presence of N,N,N-Trimethyl (11-mercaptoundecyl)ammonium (HS(CH2)11NMe3+) protecting ligand in an aqueous solution, and purified by dialysis. The resulting positively charged and water-soluble gold nanoparticles were hybridized with exfoliated silicate sheets by electrostatic interaction. The formation of Au clay hybrids could be easily confirmed by the powder X-ray diffraction with the increased basal spacing of clay upon insertion of Au nanoparticles. TEM image clearly revealed that the Au particles with an average size of 4 nm maintain their structure even after intercalation. The Au nanoparticles supported by clay matrix were found to be thermally more stable, suggesting that the Au nanoparticles were homogeneously protected with clay nanoplates. The present synthetic route could be further applicable to various hybrid systems between metal nanoparticles and clays.

Facile preparation of surfactant-free Au NPs/RGO/Ni foam for degradation of 4-nitrophenol and detection of hydrogen peroxide

NASA Astrophysics Data System (ADS)

Liu, Y. Y.; Guo, X. L.; Zhao, L.; Zhu, L.; Chen, Z. T.; Chen, J.; Zhang, Y.; Sun, L. T.; Zhao, Y. H.

2018-06-01

The application of Au nanoparticles (Au NPs) often requires surface modification with chemical surfactants, which dramatically reduce the surface activity and increase the chemical contamination and cost of Au NPs. In this research, we have developed a novel Au NPs/reduced graphene oxide/Ni foam hybrid (Au NPs/RGO/NiF) by in situ reduction through ascorbic acid and replacement reaction. This method is green, facile and efficient. The Au NPs are free of chemical surfactants and are homogeneously distributed on the surface of the RGO/NiF. The as-prepared Au NPs/RGO/NiF hybrid is uniform, stable and exhibits not only a high reduction efficiency for the reduction of 4-nitrophenol with a catalytic kinetic constant of up to 0.46 min‑1 (0.15 cm3 catalysis) but also a sensitive and selective detection of H2O2 with a detection limit of ∼1.60 μM.

22 CFR 62.31 - Au pairs.

Code of Federal Regulations, 2010 CFR

2010-04-01

... designed to measure differences in characteristics among applicants against those characteristics... survey of all host family and au pair participants regarding satisfaction with the program, its strengths... the Department of Homeland Security's Student and Exchange Visitor Information System (SEVIS...

22 CFR 62.31 - Au pairs.

Code of Federal Regulations, 2014 CFR

2014-04-01

... designed to measure differences in characteristics among applicants against those characteristics... survey of all host family and au pair participants regarding satisfaction with the program, its strengths... the Department of Homeland Security's Student and Exchange Visitor Information System (SEVIS...

22 CFR 62.31 - Au pairs.

Code of Federal Regulations, 2011 CFR

2011-04-01

... designed to measure differences in characteristics among applicants against those characteristics... survey of all host family and au pair participants regarding satisfaction with the program, its strengths... the Department of Homeland Security's Student and Exchange Visitor Information System (SEVIS...

22 CFR 62.31 - Au pairs.

Code of Federal Regulations, 2012 CFR

2012-04-01

... designed to measure differences in characteristics among applicants against those characteristics... survey of all host family and au pair participants regarding satisfaction with the program, its strengths... the Department of Homeland Security's Student and Exchange Visitor Information System (SEVIS...

22 CFR 62.31 - Au pairs.

Code of Federal Regulations, 2013 CFR

2013-04-01

... designed to measure differences in characteristics among applicants against those characteristics... survey of all host family and au pair participants regarding satisfaction with the program, its strengths... the Department of Homeland Security's Student and Exchange Visitor Information System (SEVIS...

Properties of Au/Copper oxide nanocomposite prepared by green laser irradiation of the mixture of individual suspensions

NASA Astrophysics Data System (ADS)

Aazadfar, Parvaneh; Solati, Elmira; Dorranian, Davoud

2018-04-01

The fundamental wavelength of a Q-switched pulsed Nd:YAG laser was employed to produce Au and copper oxide nanoparticles via pulsed laser ablation method in water. Different volumetric ratio of nanoparticles were mixed and irradiated by the second harmonic pulses of the Nd:YAG laser to prepare Au/Copper oxide nanocomposite. The experimental investigation was dedicated to study the properties of Au/Copper oxide nanocomposite as a function of volumetric ratio of Au nanoparticles and copper oxide nanoparticles. Nanocomposites of Au and copper oxide were found almost spherical in shape. Adhesion of spherical nanostructure in Au/Copper oxide nanocomposites was decreased with increasing the concentration of Au nanoparticles. Crystalline phase of the Au/Copper oxide nanocomposites differs with the change in the volumetric ratio of Au and copper oxide nanoparticles. The intensity of surface plasmon resonance of Au nanoparticles was decreased after irradiation. Au/Copper oxide nanocomposites suspensions have emissions in the visible range. Results reveal that green laser irradiation of nanoparticle suspensions is an appropriate method to synthesize Au based nanocomposites with controlled composition and size.

Superparamagnetic Au-Fe3O4 nanoparticles: one-pot synthesis, biofunctionalization and toxicity evaluation

NASA Astrophysics Data System (ADS)

Pariti, A.; Desai, P.; Maddirala, S. K. Y.; Ercal, N.; Katti, K. V.; Liang, X.; Nath, M.

2014-09-01

Superparamagnetic Au-Fe3O4 bifunctional nanoparticles have been synthesized using a single step hot-injection precipitation method. The synthesis involved using Fe(CO)5 as iron precursor and HAuCl4 as gold precursor in the presence of oleylamine and oleic acid. Oleylamine helps in reducing Au3+ to Au0 seeds which simultaneously oxidizes Fe(0) to form Au-Fe3O4 bifunctional nanoparticles. Triton® X-100 was employed as a highly viscous solvent to prevent agglomeration of Fe3O4 nanoparticles. Detailed characterization of these nanoparticles was performed by using x-ray powder diffraction, transmission electron microscopy, scanning tunneling electron microscopy, UV-visible spectroscopy, Mössbauer and magnetometry studies. To evaluate these nanoparticles’ applicability in biomedical applications, L-cysteine was attached to the Au-Fe3O4 nanoparticles and cytotoxicity of Au-Fe3O4 nanoparticles was tested using CHO cells by employing MTS assay. L-cysteine modified Au-Fe3O4 nanoparticles were qualitatively characterized using Fourier transform infrared spectroscopy and Raman spectroscopy; and quantitatively using acid ninhydrin assay. Investigations reveal that that this approach yields Au-Fe3O4 bifunctional nanoparticles with an average particle size of 80 nm. Mössbauer studies indicated the presence of Fe in Fe3+ in A and B sites (tetrahedral and octahedral, respectively) and Fe2+ in B sites (octahedral). Magnetic measurements also indicated that these nanoparticles were superparamagnetic in nature due to Fe3O4 region. The saturation magnetization for the bifunctional nanoparticles was observed to be ˜74 emu g-1, which is significantly higher than the previously reported Fe3O4 nanoparticles. Mössbauer studies indicated that there was no significant Fe(0) impurity that could be responsible for the superparamagnetic nature of these nanoparticles. None of the investigations showed any presence of other impurities such as Fe2O3 and FeOOH. These Au-Fe3O4 bifunctional nanoparticles showed no significant cytotoxicity to the CHO cells up to 48 h even at concentrations of 1 mg ml-1 making them suitable for biomedical applications such as local heat generators (hyperthermia) for cancer treatment and drug delivery vehicles.

TiO2-SiO2 Coatings with a Low Content of AuNPs for Producing Self-Cleaning Building Materials

PubMed Central

Gil, M. L. Almoraima; Mosquera, María J.

2018-01-01

The high pollution levels in our cities are producing a significant increase of dust on buildings. An application of photoactive coatings on building materials can produce buildings with self-cleaning surfaces. In this study, we have developed a simple sol-gel route for producing Au-TiO2/SiO2 photocatalysts with application on buildings. The gold nanoparticles (AuNPs) improved the TiO2 photoactivity under solar radiation because they promoted absorption in the visible range. We varied the content of AuNPs in the sols under study, in order to investigate their effect on self-cleaning properties. The sols obtained were sprayed on a common building stone, producing coatings which adhere firmly to the stone and preserve their aesthetic qualities. We studied the decolourization efficiency of the photocatalysts under study against methylene blue and against soot (a real staining agent for buildings). Finally, we established that the coating with an intermediate Au content presented the best self-cleaning performance, due to the role played by its structure and texture on its photoactivity. PMID:29558437

Radiosensitizing effect of gold nanoparticles in carbon ion irradiation of human cervical cancer cells

NASA Astrophysics Data System (ADS)

Kaur, Harminder; Avasthi, D. K.; Pujari, Geetanjali; Sarma, Asitikantha

2013-07-01

Noble metal nanoparticles have received considerable attention in biotechnology for their role in bio sensing due to surface plasmon resonance, medical diagnostics due to better imaging contrast and therapy. The radiosensitization effect of gold nanoparticles (AuNP) has been gaining popularity in radiation therapy of cancer cells. The better depth dose profile of energetic ion beam proves its superiority over gamma radiation for fighting against cancer. In the present work, the glucose capped gold nanoparticles (Glu-AuNP) were synthesised and internalized in the HeLa cells. Transmission electron microscopic analysis of ultrathin sections of Glu-AuNP treated HeLa cells confirmed the internalization of Glu-AuNPs. Control HeLa cells and Glu-AuNp treated HeLa cells were irradiated at different doses of 62 MeV 12C ion beam (LET - 290keV/μm) at BIO beam line of using 15UD Pelletron accelerator at Inter University Accelerator Centre, New Delhi, India. The survival fraction was assessed by colony forming assay which revealed that the dose of carbon ion for 90% cell killing in Glu-AuNP treated HeLa cells and control HeLa cells are 2.3 and 3.2 Gy respectively. This observation shows ˜ 28% reduction of 12C6+ ion dose for Glu-AuNP treated HeLa cells as compared to control HeLa cells.

A rapid green strategy for the synthesis of Au "meatball"-like nanoparticles using green tea for SERS applications

NASA Astrophysics Data System (ADS)

Wu, Shichao; Zhou, Xi; Yang, Xiangrui; Hou, Zhenqing; Shi, Yanfeng; Zhong, Lubin; Jiang, Qian; Zhang, Qiqing

2014-09-01

We report a simple and rapid biological approach to synthesize water-soluble and highly roughened "meatball"-like Au nanoparticles using green tea extract under microwave irradiation. The synthesized Au meatball-like nanoparticles possess excellent monodispersity and uniform size (250 nm in diameter). Raman measurements show that these tea-generated meatball-like gold nanostructures with high active surface areas exhibit a high enhancement of surface-enhanced Raman scattering. In addition, the Au meatball-like nanoparticles demonstrate good biocompatibility and remarkable in vitro stability at the biological temperature. Meanwhile, the factors that influence the Au meatball-like nanoparticles morphology are investigated, and the mechanisms behind the nonspherical shape evolution are discussed.

On the nature of L1{sub 0} ordering in equiatomic AuNi and AuCu thin films grown on Au(001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dynna, M.; Marty, A.; Gilles, B.

1997-01-01

The L1{sub 0} ordering of thin epitaxial films having a (001) surface normal subject to elastic constraints imposed by a similarly oriented substrate has been investigated both experimentally and theoretically. Thin AuNi films grown by MBE at room temperature on Au(001) by means of the alternating deposition of Au and Ni are found to possess a L1{sub 0} structure free of periodic antiphase boundaries when growth is controlled in such a way as to ensure that the quantity of Au or Ni deposited is almost exactly equal to one monolayer. If such control is not exercised during growth, a structuremore » having periodic antiphase boundaries is formed. This behavior stands in contrast to that of AuCu during room temperature MBE growth on Au(001), where a strongly ordered L2{sub 0} structure free of antiphase boundaries is formed even on the codeposition of Au and Cu. The effect of elastic constraints on the state of order in an alloy film which undergoes an L2{sub 0} order-disorder transition is examined as a function of temperature, lattice mismatch, and film thickness within the context of a model which allows for the introduction of dislocations in order to relieve misfit strain. Calculations are performed in detail for the case of AuCu, where particular attention is paid to the coupling between film thickness, the number of misfit dislocations present at equilibrium, and the state of order.« less

Empowered Commanders: The Cornerstone to Agile, Flexible Command and Control

DTIC Science & Technology

2015-02-01

Feb/ SLP -Wilsbach-Lyle.pdf. 4. Gilmary Michael Hostage III and Larry R. Broadwell Jr., "Resilient Command and Control: The Need for Distributed Control...www.au.af.mil / au/ afri/aspj/digital/pdf/ articles/ 2014-Jul-Aug/ SLP -Deptula.pdf. 18. Gen Hawk Carlisle, multiple speeches, November 2012-September

Great improvement in pseudocapacitor properties of nickel hydroxide via simple gold deposition.

PubMed

Kim, Sun-I; Thiyagarajan, Pradheep; Jang, Ji-Hyun

2014-10-21

In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)2) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)2. Au NP-deposited Ni(OH)2 (Au/Ni(OH)2) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)2 synthesized via a hydrothermal method. Compared with pristine Ni(OH)2, Au/Ni(OH)2 shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)2 reached 1927 F g(-1) at 1 A g(-1), which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g(-1) and 5000 cycles while that of pristine Ni(OH)2 was 1363 F g(-1) and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)2 as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)2; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)2 nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I-V characteristic data.

In situ growth of gold nanoparticles on Hg2+-binding M13 phages for mercury sensing.

PubMed

Wang, Xiaoyan; Yang, Ting; Zhang, Xiaoxiao; Chen, Mingli; Wang, Jianhua

2017-11-09

Mercury poses a serious threat to human health and the ecosystem. Its pollution is still prevalent in developing areas, which calls for the development of a simple on-site method for Hg 2+ detection. Plasmonic nanosensors for mercury, especially those based on gold nanoparticles (AuNPs), have been increasingly developed due to the flourish of nanotechnology in the last decade. However, the limitation on either selectivity or stability hindered their practical applications. Herein, by taking advantage of the unique optical properties of AuNPs and the versatility of M13 phages, a novel Hg 2+ sensing strategy is proposed. AuNPs grew in situ on the surface of Hg 2+ -binding M13 phages at room temperature and the resulting AuNP-phage networks were directly used for mercury sensing. Hg 2+ was selectively captured by M13 phages indwelling in the networks and gathered around AuNPs, followed by the reduction into Hg(0) and deposition on the AuNP surfaces, wherein it resulted in a blue shift of the SPR band of AuNPs and an increase in the absorbance. An LOD of 8 × 10 -8 mol L -1 was achieved based on the quantification of the absorption ratio of AuNPs at 525 and 650 nm. As the Hg 2+ recognition was double guaranteed by the capture of Hg 2+ -binding phages as well as the unique affinity between mercury and gold, the sensing system showed a high selectivity and a superior interference tolerance capability, facilitating its practical applications in environmental water bodies without deterioration of the sensing performance.

Optimization of nanocomposite Au/TiO2 thin films towards LSPR optical-sensing

NASA Astrophysics Data System (ADS)

Rodrigues, M. S.; Costa, D.; Domingues, R. P.; Apreutesei, M.; Pedrosa, P.; Martin, N.; Correlo, V. M.; Reis, R. L.; Alves, E.; Barradas, N. P.; Sampaio, P.; Borges, J.; Vaz, F.

2018-04-01

Nanomaterials based on Localized Surface Plasmon Resonance (LSPR) phenomena are revealing to be an important solution for several applications, namely those of optical biosensing. The main reasons are mostly related to their high sensitivity, with label-free detection, and to the simplified optical systems that can be implemented. For the present work, the optical sensing capabilities were tailored by optimizing LSPR absorption bands of nanocomposite Au/TiO2 thin films. These were grown by reactive DC magnetron sputtering. The main deposition parameters changed were the number of Au pellets placed in the Ti target, the deposition time, and DC current applied to the Ti-Au target. Furthermore, the Au NPs clustering, a key feature to have biosensing responses, was induced by several post-deposition in-air annealing treatments at different temperatures, and investigated via SEM analysis. Results showed that the Au/TiO2 thin films with a relatively low thickness (∼100 nm), revealing concentrations of Au close to 13 at.%, and annealed at temperatures above 600 °C, had the most well-defined LSPR absorption band and thus, the most promising characteristics to be explored as optical sensors. The NPs formation studies revealed an incomplete aggregation at 300 and 500 ⁰C and well-defined spheroidal NPs for higher temperatures. Plasma treatment with Ar led to a gradual blue-shift of the LSPR absorption band, which demonstrates the sensitivity of the films to changes in the dielectric environment surrounding the NPs (essential for optical sensing applications) and the exposure of the Au nanoparticles (crucial for a higher sensitivity).

Fluorescence and room temperature activity of Y₂O₃:(Eu³⁺,Au³⁺)/palygorskite nanocomposite.

PubMed

He, Xi; Yang, Huaming

2015-01-28

The fluorescence and room temperature activity of a palygorskite supported Y2O3:(Eu(3+),Au(3+)) nanocomposite were investigated to design a fluorescence-indicated catalyst. The effects of Au(3+) doping on the structure and surface properties of the host material were systematically characterized. The fluorescence intensity of Y2O3:Eu(3+) was affected by Au(3+) doping, which was related to the crystallinity of Y2O3. Excess Au(3+) ions were segregated to the host surface and reduced to metallic Au. The local symmetry of Eu(3+) was reduced by Au(3+) doping, which benefited the energy transfer between Eu(3+) and Au(3+). Energy absorbed by Eu(3+) was transferred from Au(3+) to metallic Au, where electrons were produced. These electrons were absorbed by O2 to change into O2(-), which acted as the oxidant for ortho-dichlorobenzene (o-DCB). The variation of fluorescence intensity during the catalytic reaction was observed. The room temperature catalytic activity of the nanocomposite under UV irradiation was revealed. The as-synthesized nanocomposite might have potential applications in environmental fields.

Nano-bio assemblies for artificial light harvesting systems

NASA Astrophysics Data System (ADS)

Bain, Dipankar; Maity, Subarna; Patra, Amitava

2018-02-01

Ultrasmall fluorescent gold nanoclusters (Au NCs) have drawn considerable research interest owing to their molecular like properties such as d-sp and sp-sp transitions, and intense fluorescence. Fluorescent Au NCs have especial attraction in biological system owing to their biocompatibility and high photostability. Recently, several strategies have been adapted to design an artificial light-harvesting system using Au NCs for potential applications. Here, we have designed Au nanoclusters based dsDNA (double stranded deoxyribonucleic acid) nano assemblies where the Au nanocluster is covalently attached with Alexa Fluor 488 (A488) dye tagged dsDNA. Investigation reveals that the incorporation of Ag+ into dsDNA enhances the rate of energy transfer from A488 to Au NCs. In addition cadmium telluride quantum dot (CdTe QDs) based Au NCs hybrid material shows the significant enhancement of energy transfer 35% to 83% with changing the capping ligand of Au NCs from glutathione (GSH) to bovine serum albumin (BSA) protein. Another hybrid system is developed using carbon dots and dye encapsulated BSA-protein capped Au NCs for efficient light harvesting system with 83% energy transfer efficiency. Thus, Au NCs base nano bio assemblies may open up new possibilities for the construction of artificial light harvesting system.

In Situ Synthesis of Gold Nanoparticles on Wool Powder and Their Catalytic Application.

PubMed

Tang, Bin; Zhou, Xu; Zeng, Tian; Lin, Xia; Zhou, Ji; Ye, Yong; Wang, Xungai

2017-03-15

Gold nanoparticles (AuNPs) were synthesized in situ on wool powder (WP) under heating conditions. Wool powder not only reduced Au ions to AuNPs, but also provided a support for as-synthesized AuNPs. WPs were treated under different concentrations of Au ions, and corresponding optical features and morphologies of the treated WPs were investigated by UV-VIS diffuse reflectance absorption spectroscopy and scanning electron microscopy (SEM). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscope (TEM) were also employed to characterize the WP treated with AuNPs. The results demonstrate that AuNPs were produced in the presence of WP and distributed over the wool particles. The porous structure led to the synthesis of AuNPs in the internal parts of WP. Acid conditions and high temperature facilitated the synthesis of AuNPs by WP in aqueous solution. The reducibility of wool was improved after being converted to powder from fibers, due to exposure of more active groups. Moreover, the obtained AuNP-WP complexes showed significant catalytic activity to accelerate the reduction reaction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH₄).

A physical model for the acousto-ultrasonic method. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Kiernan, Michael T.; Duke, John C., Jr.

1990-01-01

A basic physical explanation, a model, and comments on NDE application of the acousto-ultrasonic (AU) method for composite materials are presented. The basis of this work is a set of experiments where a sending and a receiving piezoelectric transducer were both oriented normal to the surface, at different points, on aluminum plates, various composite plates, and a tapered aluminum plate. The purpose and basic idea is introduced. Also, general comments on the AU method are offered. A literature review is offered for areas pertinent, such as composite materials, wave propagation, ultrasonics, and the AU. Special emphasis is given to theory which is used later on and past experimental results that are important to the physical understanding of the AU method. The experimental set-up, procedure, and the ensuing analysis are described. The experimental results are presented in both a quantitative and qualitative manner. A physical understanding of experimental results based on elasticity solution is furnished. Modeling and applications of the AU method is discussed for composite material and general conclusions are stated. The physical model of the AU method for composite materials is offered, something which has been much needed and sorely lacking. This physical understanding is possible due to the extensive set of experimental measurements, also reported.

Facile fabrication of gold nanoparticles-poly(vinyl alcohol) electrospun water-stable nanofibrous mats: efficient substrate materials for biosensors.

PubMed

Wang, Juan; Yao, Hong-Bin; He, Dian; Zhang, Chuan-Ling; Yu, Shu-Hong

2012-04-01

Electrospun nanofibrous mats are intensively studied as efficient scaffold materials applied in the fields of tissue engineering, catalysis, and biosensors due to their flexibility and porosity. In this paper, we report a facile route to fabricate gold nanoparticles-poly(vinyl alcohol) (Au NPs-PVA) hybrid water stable nanofibrous mats with tunable densities of Au NPs and further demonstrate the potential application of as-prepared Au NPs-PVA nanofibrous mats as efficient biosensor substrate materials. First, through the designed in situ cross-linkage in coelectrospun PVA-glutaraldehyde nanofibers, water insoluble PVA nanofibrous mats with suitable tensile strength were successfully prepared. Then, 3-mercaptopropyltrimethoxysilane (MPTES) was modified on the surface of obtained PVA nanofibrous films, which triggered successful homogeneous decoration of Au NPs through gold-sulfur bonding interactions. Finally, the Au NPs-PVA nanofibrous mats embedded with horseradish peroxidase (HRP) by electrostatic interactions were used as biosensor substrate materials for H(2)O(2) detection. The fabricated HRP-Au NPs/PVA biosensor showed a highly sensitive detection of H(2)O(2) with a detection limit of 0.5 μM at a signal-to-noise ratio of 3. By modifying other different functional nanaoparticles or enzyme on the PVA nanofibrous film will further expand their potential applications as substrate materials of different biosensors.

Application of ToF-SIMS to the study of surfactant removal from AuNbMCM-41 and AuMCM-41 materials

NASA Astrophysics Data System (ADS)

Grams, Jacek; Sobczak, Izabela

2010-01-01

This work is focused on the application of time-of-flight secondary ion mass spectrometry (ToF-SIMS) in investigation of the surfactant removal process from AuNbMCM-41 and AuMCM-41 catalysts (MCM-41 "Mobil Composition of Matter", ordered mesoporous materials discovered by Mobil R&D Corporation). The samples investigated were prepared by co-precipitation in the presence of a cationic surfactant (cetyltrimethylammonium chloride--CH3(CH2)15N(Cl)(CH3)3) and the incipient wetness impregnation methods. The results obtained showed that the time-of-flight secondary ion mass spectrometry appears to be a very useful tool for the investigation of the residual organic template on the surface of ordered mesoporous materials of MCM-41 type. It was demonstrated that the calcination of AuNbMCM-41 and AuMCM-41 catalysts at 550 °C caused a complete removal of the surfactant from the surface of the material investigated. Moreover, it was shown that the use of bismuth liquid metal ion gun in ToF-SIMS experiments permitted obtaining higher emission intensity (more than one order of magnitude when compared to the Ga+ primary ion source) of secondary ions originating from the surfactant molecules and may facilitate an interpretation of the results obtained.

Synthesis and catalytic activity of the metastable phase of gold phosphide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernando, Deshani; Nigro, Toni A.E.; Dyer, I.D.

Recently, transition metal phosphides have found new applications as catalysts for the hydrogen evolution reaction that has generated an impetus to synthesize these materials at the nanoscale. In this work, Au{sub 2}P{sub 3} was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous. Gold nanorods were used as morphological templates with the aim of controlling the shape and size of the resulting gold phosphide particles. We demonstrate that the surface capping ligand of the gold nanoparticle precursors can influence the purity and extent to which the gold phosphide phase will form. Gold nanorods functionalized withmore » 1-dodecanethiol undergo digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanorods are used instead. The Au{sub 2}P{sub 3} nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction. - Graphical abstract: Au{sub 2}P{sub 3} was synthesized utilizing the high temperature decomposition of tri-n-octylphosphine as a source of elemental phosphorous and gold nanoparticles as reactants. We demonstrate that the surface capping ligand of the gold nanoparticle precursors influence the purity and extent to which the Au{sub 2}P{sub 3} phase will form. Gold nanorods functionalized with 1-dodecanethiol undergo digestive ripening to produce discrete spherical particles that exhibit reduced reactivity towards phosphorous, resulting in low yields of the gold phosphide. In contrast, gold phosphide was obtained as a phase pure product when cetyltrimethylammonium bromide functionalized gold nanoparticles are used instead. The Au{sub 2}P{sub 3} nanoparticles exhibited higher activity than polycrystalline gold towards the hydrogen evolution reaction. - Highlights: • The surface chemistry of gold affects the synthetic yields of Au{sub 2}P{sub 3}. • Imaging of Au{sub 2}P{sub 3} with transmission electron microscopy results in decomposition. • Au{sub 2}P{sub 3} nanoparticles exhibit activity towards the hydrogen evolution reaction.« less

Low-Cost, High Efficiency, Silicon Based Photovoltaic Devices

DTIC Science & Technology

2015-08-27

for photovoltaic applications. Figure 14: (a) Absorption and scattering efficiencies versus sizes of Au nanoparticle at 550 nm, (b) scattering...efficiency as a function of wavelength for different Au nanoparticles sizes . 32 Review of plasmonics light trapping for photovoltaic application...ensure that the irradiation variation was within 3%. The external quantum efficiency (EQE) system used a 300W Xenon light source with a spot size of 1mm

Green synthesis and characterization of novel gold nanocomposites for electrochemical sensing applications.

PubMed

Tanwar, Shivani; Ho, Ja-an Annie; Magi, Emanuele

2013-12-15

Synthesis, characterization and application of Au-PANI-Calix and Au-PANI-Nap nanocomposites, is reported herein. An easy template free green synthesis is proposed and discussed for easy expediency. A variety of analytical techniques were used to characterize the nanocomposites: UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Dynamic light scattering (DLS), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were used to characterize the nanocomposites. Surface morphology was studied by transmission electron microscopy (TEM). The nanocomposites were immobilized on screen-printed electrode and showed electroactivity in neutral pH, making them promising candidates for various analytical applications. A sensitive and selective detection of Cu(2+) was perceived on the Au-PANI-Calix modified electrode with no interference from ions K(+), Ni(2+), Co(2+), Pb(2+), Cr(3+) with a detection limit of 10nM. The copper detection is facilitated for accessible ligation with 4-sulfocalix[4]arene, so as the Cu(II)-Calix complex formed. The electrode modified with Au-PANI-Nap showed sensing application towards H2O2 with a detection limit of 1 μM. The modified electrodes were reproducible and stable for 2 months. © 2013 Elsevier B.V. All rights reserved.

Controlling Growth High Uniformity Indium Selenide (In2Se3) Nanowires via the Rapid Thermal Annealing Process at Low Temperature.

PubMed

Hsu, Ya-Chu; Hung, Yu-Chen; Wang, Chiu-Yen

2017-09-15

High uniformity Au-catalyzed indium selenide (In 2 Se 3) nanowires are grown with the rapid thermal annealing (RTA) treatment via the vapor-liquid-solid (VLS) mechanism. The diameters of Au-catalyzed In 2 Se 3 nanowires could be controlled with varied thicknesses of Au films, and the uniformity of nanowires is improved via a fast pre-annealing rate, 100 °C/s. Comparing with the slower heating rate, 0.1 °C/s, the average diameters and distributions (standard deviation, SD) of In 2 Se 3 nanowires with and without the RTA process are 97.14 ± 22.95 nm (23.63%) and 119.06 ± 48.75 nm (40.95%), respectively. The in situ annealing TEM is used to study the effect of heating rate on the formation of Au nanoparticles from the as-deposited Au film. The results demonstrate that the average diameters and distributions of Au nanoparticles with and without the RTA process are 19.84 ± 5.96 nm (30.00%) and about 22.06 ± 9.00 nm (40.80%), respectively. It proves that the diameter size, distribution, and uniformity of Au-catalyzed In 2 Se 3 nanowires are reduced and improved via the RTA pre-treated. The systemic study could help to control the size distribution of other nanomaterials through tuning the annealing rate, temperatures of precursor, and growth substrate to control the size distribution of other nanomaterials. Graphical Abstract Rapid thermal annealing (RTA) process proved that it can uniform the size distribution of Au nanoparticles, and then it can be used to grow the high uniformity Au-catalyzed In 2 Se 3 nanowires via the vapor-liquid-solid (VLS) mechanism. Comparing with the general growth condition, the heating rate is slow, 0.1 °C/s, and the growth temperature is a relatively high growth temperature, > 650 °C. RTA pre-treated growth substrate can form smaller and uniform Au nanoparticles to react with the In 2 Se 3 vapor and produce the high uniformity In 2 Se 3 nanowires. The in situ annealing TEM is used to realize the effect of heating rate on Au nanoparticle formation from the as-deposited Au film. The byproduct of self-catalyzed In 2 Se 3 nanoplates can be inhibited by lowering the precursors and growth temperatures.

Cytotoxicity assay of biosynthesis gold nanoparticles mediated by walnut (Juglans regia) green husk extract

NASA Astrophysics Data System (ADS)

Izadiyan, Zahra; Shameli, Kamyar; Hara, Hirofumi; Mohd Taib, Siti Husnaa

2018-01-01

The unique properties of gold nanoparticles (Au-NPs) produce in plant extract make them attractive for use in medical and industrial applications, it is necessary to develop environmentally friendly methods for their synthesis. This can be accomplished by replacing the traditional chemical compounds for the reduction of the gold ions to Au-NPs during synthesis with natural plant extracts or with plasmas atmospheric pressure. Here, the biosynthesis of Au-NPs using the Juglans regia (J. regia) green husk extract was investigated as the reducing and stabilizing agent. The formation of Au-NPs was initially monitored by visual observation and then characterized with the help of various characterization techniques. UV-vis spectroscopy results showed that Au-NPs synthesized using moderate temperature have a blue shifting, good distribution and smaller size compare with Au-NPs fabricated in room temperature. X-ray diffraction (XRD) results revealed the distinctive formation of the crystalline structure of Au-NPs with a spherical shape. According to transmission electron microscopy (TEM), the mean diameter and standard deviation of Au-NPs at room and moderate temperatures were 19.19 ± 4.7 and 14.32 ± 3.24 nm, respectively. The result of Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) are in good agreement with each other and confirm that by using the moderate temperature compare to the room temperature the yield of reaction increased. Based on the zeta potential result, Au-NPs has sufficient value for the stability of the solution. According to FTIR spectrum, the J. regia would be coated on the gold ions surface in a successful manner. The non-toxic effect of Au-NPs concentration below 250 μg/ml was observed in the studies of in vitro cytotoxicity on normal and cancerous cell lines, respectively. The dose-dependent toxicity made it a suitable candidate for various medical applications.

The Most Effective Gold Nanorod Size for Plasmonic Photothermal Therapy: Theory and In Vitro Experiments

PubMed Central

2015-01-01

The development of new and improved photothermal contrast agents for the successful treatment of cancer (or other diseases) via plasmonic photothermal therapy (PPTT) is a crucial part of the application of nanotechnology in medicine. Gold nanorods (AuNRs) have been found to be the most effective photothermal contrast agents, both in vitro and in vivo. Therefore, determining the optimum AuNR size needed for applications in PPTT is of great interest. In the present work, we utilized theoretical calculations as well as experimental techniques in vitro to determine this optimum AuNR size by comparing plasmonic properties and the efficacy as photothermal contrast agents of three different sizes of AuNRs. Our theoretical calculations showed that the contribution of absorbance to the total extinction, the electric field, and the distance at which this field extends away from the nanoparticle surface all govern the effectiveness of the amount of heat these particles generate upon NIR laser irradiation. Comparing between three different AuNRs (38 × 11, 28 × 8, and 17 × 5 nm), we determined that the 28 × 8 nm AuNR is the most effective in plasmonic photothermal heat generation. These results encouraged us to carry out in vitro experiments to compare the PPTT efficacy of the different sized AuNRs. The 28 × 8 nm AuNR was found to be the most effective photothermal contrast agent for PPTT of human oral squamous cell carcinoma. This size AuNR has the best compromise between the total amount of light absorbed and the fraction of which is converted to heat. In addition, the distance at which the electric field extends from the particle surface is most ideal for this size AuNR, as it is sufficient to allow for coupling between the fields of adjacent particles in solution (i.e., particle aggregates), resulting in effective heating in solution. PMID:24433049

Directed self-assembly of nanogold using a chemically modified nanopatterned surface

NASA Astrophysics Data System (ADS)

Nidetz, Robert; Kim, Jinsang

2012-02-01

Electron-beam lithography (EBL) was used to define an aminosilane nanopatterned surface in order to electrostatically self-assemble gold nanoparticles (Au NPs). The chemically modified nanopatterned surfaces were immersed into a Au NP solution to allow the Au NPs to self-assemble. Equilibrium self-assembly was achieved in only 20 min. The number of Au NPs that self-assembled on an aminosilane dot was controlled by manipulating the diameters of both the Au NPs and the dots. Adding salt to the Au NP solution enabled the Au NPs to self-assemble in greater numbers on the same sized dot. However, the preparation of the Au NP solution containing salt was sensitive to spikes in the salt concentration. These spikes led to aggregation of the Au NPs and non-specific deposition of Au NPs on the substrate. The Au NP patterned surfaces were immersed in a sodium hydroxide solution in order to lift-off the patterned Au NPs, but no lift-off was observed without adequate physical agitation. The van der Waals forces are too strong to allow for lift-off despite the absence of electrostatic forces.

A Bottom-Up Engineered Broadband Optical Nanoabsorber for Radiometry and Energy Harnessing Applications

NASA Technical Reports Server (NTRS)

Kaul, Anupama B.; Coles, James B.; Megerian, Krikor G.; Eastwood, Michael; Green, Robert O.; Bandaru, Prabhakar R.

2013-01-01

Optical absorbers based on vertically aligned multi-walled carbon nanotubes (MWCNTs), synthesized using electric-field assisted growth, are described here that show an ultra-low reflectance, 100X lower compared to Au-black from wavelength lamba approximately 350 nm - 2.5 micron. A bi-metallic Co/Ti layer was shown to catalyze a high site density of MWCNTs on metallic substrates and the optical properties of the absorbers were engineered by controlling the bottom-up synthesis conditions using dc plasma-enhanced chemical vapor deposition (PECVD). Reflectance measurements on the MWCNT absorbers after heating them in air to 400deg showed negligible changes in reflectance which was still low, approximately 0.022 % at lamba approximately 2 micron. In contrast, the percolated structure of the reference Au-black samples collapsed completely after heating, causing the optical response to degrade at temperatures as low as 200deg. The high optical absorption efficiency of the MWCNT absorbers, synthesized on metallic substrates, over a broad spectral range, coupled with their thermal ruggedness, suggests they have promise in solar energy harnessing applications, as well as thermal detectors for radiometry.

Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles.

PubMed

Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

2016-04-06

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO₃ solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system.

Three-dimensional motor schema based navigation

NASA Technical Reports Server (NTRS)

Arkin, Ronald C.

1989-01-01

Reactive schema-based navigation is possible in space domains by extending the methods developed for ground-based navigation found within the Autonomous Robot Architecture (AuRA). Reformulation of two dimensional motor schemas for three dimensional applications is a straightforward process. The manifold advantages of schema-based control persist, including modular development, amenability to distributed processing, and responsiveness to environmental sensing. Simulation results show the feasibility of this methodology for space docking operations in a cluttered work area.

Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties

NASA Astrophysics Data System (ADS)

Li, Cuiling; Dag, Ömer; Dao, Thang Duy; Nagao, Tadaaki; Sakamoto, Yasuhiro; Kimura, Tatsuo; Terasaki, Osamu; Yamauchi, Yusuke

2015-03-01

Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles.

CE-MS analysis of heroin and its basic impurities using a charged polymer-protected gold nanoparticle-coated capillary.

PubMed

Zhang, Zhengxiang; Yan, Bo; Liu, Kelin; Liao, Yiping; Liu, Huwei

2009-01-01

The first application of charged polymer-protected gold nanoparticles (Au NPs) as semi-permanent capillary coating in CE-MS was presented. Poly(diallyldimethylammonium chloride) (PDDA) was the only reducing and stabilizing agent for Au NPs preparation. Stable and repeatable coating with good tolerance to 0.1 M HCl, methanol, and ACN was obtained via a simple rinsing procedure. Au NPs enhanced the coating stability toward flushing by methanol, improved the run-to-run and capillary-to-capillary repeatabilities, and improved the separation efficiency of heroin and its basic impurities for tracing geographical origins of illicit samples. Baseline resolution of eight heroin-related alkaloids was achieved on the PDDA-protected Au NPs-coated capillary under the optimum conditions: 120 mM ammonium acetate (pH 5.2) with addition of 13% methanol, separation temperature 20 degrees C, applied voltage -20 kV, and capillary effective length 60.0 cm. CE-MS analysis with run-to-run RSDs (n=5) of migration time in the range of 0.43-0.62% and RSDs (n=5) of peak area in the range of 1.49-4.68% was obtained. The established CE-MS method would offer sensitive detection and confident identification of heroin and related compounds and provide an alternative to LC-MS and GC-MS for illicit drug control.

Resistive switching behaviors of Au/pentacene/Si-nanowire arrays/heavily doped n-type Si devices for memory applications

NASA Astrophysics Data System (ADS)

Tsao, Hou-Yen; Lin, Yow-Jon

2014-02-01

The fabrication of memory devices based on the Au/pentacene/heavily doped n-type Si (n+-Si), Au/pentacene/Si nanowires (SiNWs)/n+-Si, and Au/pentacene/H2O2-treated SiNWs/n+-Si structures and their resistive switching characteristics were reported. A pentacene memory structure using SiNW arrays as charge storage nodes was demonstrated. The Au/pentacene/SiNWs/n+-Si devices show hysteresis behavior. H2O2 treatment may lead to the hysteresis degradation. However, no hysteresis-type current-voltage characteristics were observed for Au/pentacene/n+-Si devices, indicating that the resistive switching characteristic is sensitive to SiNWs and the charge trapping effect originates from SiNWs. The concept of nanowires within the organic layer opens a promising direction for organic memory devices.

Tri-metallic PtPdAu mesoporous nanoelectrocatalysts.

PubMed

Li, Chunjie; Wang, Hongjing; Li, Yinghao; Yu, Hongjie; Yin, Shuli; Xue, Hairong; Li, Xiaonian; Xu, You; Wang, Liang

2018-06-22

The design of mesoporous materials with multi-metallic compositions is highly important for various electrocatalytic applications. In this paper, we demonstrate an efficient method to directly fabricate tri-metallic PtPdAu mesoporous nanoparticles (PtPdAu MNs) in a high yield, which is simply performed by heating treatment of the reaction mixture aqueous solution at 40 °C for 4 h. Profiting from its mesoporous structure and multi-metallic components, the as-prepared PtPdAu MNs exhibit enhanced electrocatalytic activities toward both methanol oxidation reaction and oxygen reduction reaction in comparison with bi-metallic PtPd MNs and commercial Pt/C catalyst.

Tri-metallic PtPdAu mesoporous nanoelectrocatalysts

NASA Astrophysics Data System (ADS)

Li, Chunjie; Wang, Hongjing; Li, Yinghao; Yu, Hongjie; Yin, Shuli; Xue, Hairong; Li, Xiaonian; Xu, You; Wang, Liang

2018-06-01

The design of mesoporous materials with multi-metallic compositions is highly important for various electrocatalytic applications. In this paper, we demonstrate an efficient method to directly fabricate tri-metallic PtPdAu mesoporous nanoparticles (PtPdAu MNs) in a high yield, which is simply performed by heating treatment of the reaction mixture aqueous solution at 40 °C for 4 h. Profiting from its mesoporous structure and multi-metallic components, the as-prepared PtPdAu MNs exhibit enhanced electrocatalytic activities toward both methanol oxidation reaction and oxygen reduction reaction in comparison with bi-metallic PtPd MNs and commercial Pt/C catalyst.

Biomimetic synthesis of highly biocompatible gold nanoparticles with amino acid-dithiocarbamate as a precursor for SERS imaging

NASA Astrophysics Data System (ADS)

Li, Li; Liu, Jianbo; Yang, Xiaohai; Huang, Jin; He, Dinggeng; Guo, Xi; Wan, Lan; He, Xiaoxiao; Wang, Kemin

2016-03-01

Amino acid-dithiocarbamate (amino acid-DTC) was developed as both the reductant and ligand stabilizer for biomimetic synthesis of gold nanoparticles (AuNPs), which served as an excellent surface-enhanced Raman scattering (SERS) contrast nanoprobe for cell imaging. Glycine (Gly), glutamic acid (Glu), and histidine (His) with different isoelectric points were chosen as representative amino acid candidates to synthesize corresponding amino acid-DTC compounds through mixing with carbon disulfide (CS2), respectively. The pyrogenic decomposition of amino acid-DTC initiated the reduction synthesis of AuNPs, and the strong coordinating dithiocarbamate group of amino acid-DTC served as a stabilizer that grafted onto the surface of the AuNPs, which rendered the as-prepared nanoparticles a negative surface charge and high colloidal stability. MTT cell viability assay demonstrated that the biomimetic AuNPs possessed neglectful toxicity to the human hepatoma cell, which guaranteed them good biocompatibility for biomedical application. Meanwhile, the biomimetic AuNPs showed a strong SERS effect with an enhancement factor of 9.8 × 105 for the sensing of Rhodamine 6G, and two distinct Raman peaks located at 1363 and 1509 cm-1 could be clearly observed in the cell-imaging experiments. Therefore, biomimetic AuNPs can be explored as an excellent SERS contrast nanoprobe for biomedical imaging, and the amino acid-DTC mediated synthesis of the AuNPs has a great potential in bio-engineering and biomedical imaging applications.

Thermally robust Au99(SPh)42 nanoclusters for chemoselective hydrogenation of nitrobenzaldehyde derivatives in water.

PubMed

Li, Gao; Zeng, Chenjie; Jin, Rongchao

2014-03-05

We report the synthesis and catalytic application of thermally robust gold nanoclusters formulated as Au99(SPh)42. The formula was determined by electrospray ionization and matrix-assisted laser desorption ionization mass spectrometry in conjunction with thermogravimetric analysis. The optical spectrum of Au99(SPh)42 nanoclusters shows absorption peaks at ~920 nm (1.35 eV), 730 nm (1.70 eV), 600 nm (2.07 eV), 490 nm (2.53 eV), and 400 nm (3.1 eV) in contrast to conventional gold nanoparticles, which exhibit a plasmon resonance band at 520 nm (for spherical particles). The ceria-supported Au99(SPh)42 nanoclusters were utilized as a catalyst for chemoselective hydrogenation of nitrobenzaldehyde to nitrobenzyl alcohol in water using H2 gas as the hydrogen source. The selective hydrogenation of the aldehyde group catalyzed by nanoclusters is a surprise because conventional nanogold catalysts instead give rise to the product resulting from reduction of the nitro group. The Au99(SPh)42/CeO2 catalyst gives high catalytic activity for a range of nitrobenzaldehyde derivatives and also shows excellent recyclability due to its thermal robustness. We further tested the size-dependent catalytic performance of Au25(SPh)18 and Au36(SPh)24 nanoclusters, and on the basis of their crystal structures we propose a molecular adsorption site for nitrobenzaldehyde. The nanocluster material is expected to find wide application in catalytic reactions.

Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction

NASA Astrophysics Data System (ADS)

Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

2015-12-01

Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

Synthesis of Au@Pt bimetallic nanoparticles with concave Au nanocuboids as seeds and their enhanced electrocatalytic properties in the ethanol oxidation reaction.

PubMed

Tan, Lingyu; Li, Lidong; Peng, Yi; Guo, Lin

2015-12-18

Herein, a new type of uniform and well-structured Au@Pt bimetallic nanoparticles (BNPs) with highly active concave Au nanocuboids (NCs) as seeds was successfully synthesized by using the classic seed-mediated method. Electrochemical measurements were conducted to demonstrate their greatly enhanced catalytic performance in the ethanol oxidation reaction (EOR). It was found that the electrochemical performance for Au@Pt BNPs with the concave Au NCs as seeds, which were enclosed by {611} high-index facets, could be seven times higher than that of the Au@Pt bimetallic nanoparticles with regular spherical Au NPs as seeds. Furthermore, our findings show that the morphology and electrocatalytic activity of the Au@Pt BNPs can be tuned simply by changing the compositional ratios of the growth solution. The lower the amount of H2PtCl6 used in the growth solution, the thinner the Pt shell grew, and the more high-index facets of concave Au NCs seeds were exposed in Au@Pt BNPs, leading to higher electrochemical activity. These as-prepared concave Au@Pt BNPs will open up new strategies for improving catalytic efficiency and reducing the use of the expensive and scarce resource of platinum in the ethanol oxidation reaction, and are potentially applicable as electrochemical catalysts for direct ethanol fuel cells.

Gold nanoparticles stabilized by poly(4-vinylpyridine) grafted cellulose nanocrystals as efficient and recyclable catalysts.

PubMed

Zhang, Zhen; Sèbe, Gilles; Wang, Xiaosong; Tam, Kam C

2018-02-15

pH-responsive poly(4-vinylpyridine) (P4VP) grafted cellulose nanocrystals (P4VP-g-CNC) were prepared by Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) and subsequently used to stabilize gold nanoparticles (Au NPs) as efficient and recyclable nanocatalysts for the reduction of 4-nitrophenol (4NP). The presence of P4VP brushes on the CNC surface controlled the growth of Au NPs yielding smaller averaged diameter compared to Au NPs deposited directly on pristine CNC. The catalytic performances of pristine Au NPs, Au@CNC and Au@P4VP-g-CNC were compared by measuring the turnover frequency (TOF) for the catalytic reduction of 4NP. Compared to pristine Au NPs, the catalytic activity of Au@CNC and Au@P4VP-g-CNC were 10 and 24 times better. Moreover, the Au@P4VP-g-CNC material could be recovered via flocculation at pH>5, and the recycled nanocatalyst remained highly active. Copyright © 2017 Elsevier Ltd. All rights reserved.

A general and high-yield galvanic displacement approach to Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells and enhanced electrocatalytic performances.

PubMed

Kuai, Long; Geng, Baoyou; Wang, Shaozhen; Sang, Yan

2012-07-23

In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au-Au, Au-Pd, and Au-Pt core-shell nanostructures with typical porous shells. Moreover, the Au-Au isomeric core-shell nanostructure is reported for the first time. The lower oxidation states of Au(I), Pd(II), and Pt(II) are supposed to contribute to the formation of porous core-shell nanostructures instead of yolk-shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au-Pd core-shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core-shell nanostructures. As expected, the Au-Pd core-shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I(f)/I(b) is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au-M (M = Au, Pd, and Pt) core-shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface-enhanced Raman scattering, and so forth. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanometer Scale Confined Growth of Single-Crystalline Gold Nanowires via Photocatalytic Reduction.

PubMed

Lee, Seonhee; Bae, Changdeuck; Shin, Hyunjung

2018-06-20

Single-crystalline gold nanowires (Au NWs) are directly synthesized by the photocatalytic reduction of an aqueous HAuCl 4 solution inside high-aspect-ratio TiO 2 nanotubes (NTs). Crystalline TiO 2 (anatase) NTs are prepared by the template-assisted atomic layer deposition technique with a subsequent annealing. Under the irradiation of ultraviolet light, photoexcited electrons are formed on the surfaces of TiO 2 NTs and could reduce Au ions to create nuclei without using any surfactant, reducing agent, and/or seed. Once nucleation occurred, high-aspect-ratio Au NWs are grown inside the TiO 2 NTs in a diffusion-controlled manner. As the solution pH increased, the nucleation/growth rate decreased and twin-free (or not observed), single-crystalline Au NWs are formed. At a pH above 6, the nucleation/growth rates increased and Au nanoparticles are observed both inside and outside of the TiO 2 NTs. The confined nanoscale geometries of the interior of the TiO 2 NTs are found to play a key role in the controlled diffusion of Au species and in determining the crystal morphology of the resulting Au NWs.

Understanding and controlling the structure and segregation behaviour of AuRh nanocatalysts

PubMed Central

Piccolo, Laurent; Li, Z. Y.; Demiroglu, Ilker; Moyon, Florian; Konuspayeva, Zere; Berhault, Gilles; Afanasiev, Pavel; Lefebvre, Williams; Yuan, Jun; Johnston, Roy L.

2016-01-01

Heterogeneous catalysis, which is widely used in the chemical industry, makes a great use of supported late-transition-metal nanoparticles, and bimetallic catalysts often show superior catalytic performances as compared to their single metal counterparts. In order to optimize catalyst efficiency and discover new active combinations, an atomic-level understanding and control of the catalyst structure is desirable. In this work, the structure of catalytically active AuRh bimetallic nanoparticles prepared by colloidal methods and immobilized on rutile titania nanorods was investigated using aberration-corrected scanning transmission electron microscopy. Depending on the applied post-treatment, different types of segregation behaviours were evidenced, ranging from Rh core – Au shell to Janus via Rh ball – Au cup configuration. The stability of these structures was predicted by performing density-functional-theory calculations on unsupported and titania-supported Au-Rh clusters; it can be rationalized from the lower surface and cohesion energies of Au with respect to Rh, and the preferential binding of Rh with the titania support. The bulk-immiscible AuRh/TiO2 system can serve as a model to understand similar supported nanoalloy systems and their synergistic behaviour in catalysis. PMID:27739480

Large-scale, low-cost synthesis of monodispersed gold nanorods using a gemini surfactant

NASA Astrophysics Data System (ADS)

Xu, Yong; Zhao, Yang; Chen, Lei; Wang, Xuchun; Sun, Jianxia; Wu, Haihua; Bao, Feng; Fan, Jian; Zhang, Qiao

2015-04-01

In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ~2.4 to ~6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au3+ to Au+ by the unsaturated C&z.dbd;C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to ``dog-bones'' by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the complex effect between bromide ions and gold ions. This work will not only help to achieve the industrial production of AuNRs, but also promote research into practical applications of various nanomaterials.In this work, we demonstrate that monodispersed gold nanorods (AuNRs) can be obtained in a large-scale and cost-effective way. By using an industrial grade gemini surfactant (P16-8-16), the cost of the synthesis of high-quality AuNRs can be significantly reduced by 90%. The synthesis can be scaled up to over 4 L. The aspect ratio of AuNRs can be well tuned from ~2.4 to ~6.3, resulting in a wide tunability of the SPR properties. Systematic studies reveal that P16-8-16 could have a dual function: it can not only act as a capping ligand to stabilize AuNRs but also it can pre-reduce Au3+ to Au+ by the unsaturated C&z.dbd;C bond. Furthermore, the shape of AuNRs can be tailored from straight nanorods to ``dog-bones'' by simply varying the concentration of the surfactant. A mechanistic study shows that the shape change can be attributed to the presence of excess bromide ions because of the complex effect between bromide ions and gold ions. This work will not only help to achieve the industrial production of AuNRs, but also promote research into practical applications of various nanomaterials. Electronic supplementary information (ESI) available: Digital pictures during the growth process of AuNRs, TEM images of nanoparticles obtained without P16-8-16 or silver, and HRTEM image and SAED patterns of quadrupeds. See DOI: 10.1039/c5nr00343a

Controllable biosynthesis of gold nanoparticles from a Eucommia ulmoides bark aqueous extract

NASA Astrophysics Data System (ADS)

Guo, Mingxia; Li, Wei; Yang, Feng; Liu, Huihong

2015-05-01

The present work reports the green synthesis of gold nanoparticles (AuNPs) by water extract of Eucommia ulmoides (E. ulmoides) bark. The effects of various parameters such as the concentration of reactants, pH of the reaction mixture, temperature and the time of incubation were explored to the controlled formation of gold nanoparticles. The characterization through high resolution-transmission electron microscopic (HRTEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) infer that the as-synthesized AuNPs were spherical in shape with a face cubic crystal (FCC) structure. The results from zeta potential and dynamic light scattering (DLS) suggest the good stability and narrow size distribution of the AuNPs. This method for synthesis of AuNPs is simple, economic, nontoxic and efficient. The as-synthesized AuNPs show excellent catalytic activity for the catalytic reducing decoloration of model compounds of azo-dye: reactive yellow 179 and Congo red.

Application of neural networks in the acousto-ultrasonic evaluation of metal-matrix composite specimens

NASA Technical Reports Server (NTRS)

Cios, Krzysztof J.; Tjia, Robert E.; Vary, Alex; Kautz, Harold E.

1992-01-01

Acousto-ultrasonics (AU) is a nondestructive evaluation (NDE) technique that was devised for the testing of various types of composite materials. A study has been done to determine how effectively the AU technique may be applied to metal-matrix composites (MMCs). The authors use the results and data obtained from that study and apply neural networks to them, particularly in the assessment of mechanical property variations of a specimen from AU measurements. It is assumed that there is no information concerning the important features of the AU signal which relate to the mechanical properties of the specimen. Minimally processed AU measurements are used while relying on the network's ability to extract the significant features of the signal.

Fabrication of Te and Te-Au Nanowires-Based Carbon Fiber Fabrics for Antibacterial Applications

PubMed Central

Chou, Ting-Mao; Ke, Yi-Yun; Tsao, Yu-Hsiang; Li, Ying-Chun; Lin, Zong-Hong

2016-01-01

Pathogenic bacteria that give rise to diseases every year remain a major health concern. In recent years, tellurium-based nanomaterials have been approved as new and efficient antibacterial agents. In this paper, we developed the approach to directly grow tellurium nanowires (Te NWs) onto commercial carbon fiber fabrics and demonstrated their antibacterial activity. Those Te NWs can serve as templates and reducing agents for gold nanoparticles (Au NPs) to deposit. Three different Te-Au NWs with varied concentration of Au NPs were synthesized and showed superior antibacterial activity and biocompability. These results indicate that the as-prepared carbon fiber fabrics with Te and Te-Au NWs can become antimicrobial clothing products in the near future. PMID:26861380

BSA Au clusters as a probe for enhanced fluorescence detection using multipulse excitation scheme.

PubMed

Raut, Sangram L; Rich, Ryan; Fudala, Rafal; Kokate, R; Kimball, J D; Borejdo, Julian; Vishwanatha, Jamboor K; Gryczynski, Zygmunt; Gryczynski, Ignacy

2014-01-01

Although BSA Au clusters fluoresce in red region (λmax: 650 nm), they are of limited use due to low fluorescence quantum yield (~6%). Here we report an enhanced fluorescence imaging application of fluorescent bio-nano probe BSA Au clusters using multipulse excitation scheme. Multipulse excitation takes advantage of long fluorescence lifetime (> 1 µs) of BSA Au clusters and enhances its fluorescence intensity 15 times over short lived cellular auto-fluorescence. Moreover we have also shown that by using time gated detection strategy signal (fluorescence of BSA Au clusters) to noise (auto-fluorescence) ratio can be increased by 30 fold. Thereby with multipulse excitation long lifetime probes can be used to develop biochemical assays and perform optical imaging with zero background.

Reversed nanoscale Kirkendall effect in Au–InAs hybrid nanoparticles

DOE PAGES

Liu, Jing; Amit, Yorai; Li, Yuanyuan; ...

2016-10-10

Metal–semiconductor hybrid nanoparticles (NPs) offer interesting synergistic properties, leading to unique behaviors that have already been exploited in photocatalysis, electrical, and optoelectronic applications. A fundamental aspect in the synthesis of metal–semiconductor hybrid NPs is the possible diffusion of the metal species through the semiconductor lattice. The importance of understanding and controlling the co-diffusion of different constituents is demonstrated in the synthesis of various hollow-structured NPs via the Kirkendall effect. Here, we used a postsynthesis room-temperature reaction between AuCl 3 and InAs nanocrystals (NCs) to form metal–semiconductor core–shell hybrid NPs through the “reversed Kirkendall effect”. In the presented system, the diffusionmore » rate of the inward diffusing species (Au) is faster than that of the outward diffusing species (InAs), which results in the formation of a crystalline metallic Au core surrounded by an amorphous, oxidized InAs shell containing nanoscale voids. We used time-resolved X-ray absorption fine-structure (XAFS) spectroscopy to monitor the diffusion process and found that both the size of the Au core and the extent of the disorder of the InAs shell depend strongly on the Au-to-NC ratio. We have determined, based on multielement fit analysis, that Au diffuses into the NC via the kick-out mechanism, substituting for In host atoms; this compromises the structural stability of the lattice and triggers the formation of In–O bonds. These bonds were used as markers to follow the diffusion process and indicate the extent of degradation of the NC lattice. Time-resolved X-ray diffraction (XRD) was used to measure the changes in the crystal structures of InAs and the nanoscale Au phases. By combining the results of XAFS, XRD, and electron microscopy, we correlated the changes in the local structure around Au, As, and In atoms and the changes in the overall InAs crystal structure. This correlative analysis revealed a co-dependence of different structural consequences when introducing Au into the InAs NCs. As a result this study of diffusion effects in nanocrystals has relevance to powerful concepts in solid-state nanochemistry related to processes of cation exchange, doping reactions, and diffusion mechanisms.« less

Reversed Nanoscale Kirkendall Effect in Au–InAs Hybrid Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jing; Amit, Yorai; Li, Yuanyuan

2016-11-08

Metal–semiconductor hybrid nanoparticles (NPs) offer interesting synergistic properties, leading to unique behaviors that have already been exploited in photocatalysis, electrical, and optoelectronic applications. A fundamental aspect in the synthesis of metal–semiconductor hybrid NPs is the possible diffusion of the metal species through the semiconductor lattice. The importance of understanding and controlling the co-diffusion of different constituents is demonstrated in the synthesis of various hollow-structured NPs via the Kirkendall effect. Here, we used a postsynthesis room-temperature reaction between AuCl 3 and InAs nanocrystals (NCs) to form metal–semiconductor core–shell hybrid NPs through the “reversed Kirkendall effect”. In the presented system, the diffusionmore » rate of the inward diffusing species (Au) is faster than that of the outward diffusing species (InAs), which results in the formation of a crystalline metallic Au core surrounded by an amorphous, oxidized InAs shell containing nanoscale voids. We used time-resolved X-ray absorption fine-structure (XAFS) spectroscopy to monitor the diffusion process and found that both the size of the Au core and the extent of the disorder of the InAs shell depend strongly on the Au-to-NC ratio. We have determined, based on multielement fit analysis, that Au diffuses into the NC via the kick-out mechanism, substituting for In host atoms; this compromises the structural stability of the lattice and triggers the formation of In–O bonds. These bonds were used as markers to follow the diffusion process and indicate the extent of degradation of the NC lattice. Time-resolved X-ray diffraction (XRD) was used to measure the changes in the crystal structures of InAs and the nanoscale Au phases. By combining the results of XAFS, XRD, and electron microscopy, we correlated the changes in the local structure around Au, As, and In atoms and the changes in the overall InAs crystal structure. This correlative analysis revealed a co-dependence of different structural consequences when introducing Au into the InAs NCs. Therefore, this study of diffusion effects in nanocrystals has relevance to powerful concepts in solid-state nanochemistry related to processes of cation exchange, doping reactions, and diffusion mechanisms.« less

NUTS and BOLTS: Applications of Fluorescence Detected Sedimentation

PubMed Central

Kroe, Rachel R.; Laue, Thomas M.

2008-01-01

Analytical ultracentrifugation is a widely used method for characterizing the solution behavior of macromolecules. However, the two commonly used detectors (absorbance and interference) impose some fundamental restrictions on the concentrations and complexity of the solutions that can be analyzed. The recent addition of a fluorescence detector for the XL-I analytical ultracentrifuge (AU-FDS) enables two different types of sedimentation experiments. First, the AU-FDS can detect picomolar concentrations of labeled solutes allowing the characterization of very dilute solutions of macromolecules, applications we call Normal Use Tracer Sedimentation (NUTS). The great sensitivity of NUTS analysis allows the characterization of small quantities of materials and high affinity interactions. Second, AU-FDS allows characterization of trace quantities of labeled molecules in solutions containing high concentrations and complex mixtures of unlabeled molecules, applications we call Biological On Line Tracer Sedimentation (BOLTS). The discrimination of BOLTS enables the size distribution of a labeled macromolecule to be determined in biological milieu such as cell lysates and serum. Examples are presented that embody features of both NUTS and BOLTS applications, along with our observations on these applications. PMID:19103145

Seed-mediated growth of Au nanorings with size control on Pd ultrathin nanosheets and their tunable surface plasmonic properties

NASA Astrophysics Data System (ADS)

Wang, Wenxing; Yan, Yucong; Zhou, Ning; Zhang, Hui; Li, Dongsheng; Yang, Deren

2016-02-01

Nanorings made of noble metals such as Au and Ag have attracted particular interest in plasmonic properties since they allow remarkable tunability of plasmon resonance wavelengths associated with their unique structural features. Unfortunately, most of the syntheses for Au nanorings involve complex procedures and/or require highly specialized and expensive facilities. Here, we report a seed-mediated approach for selective deposition of Au nanorings on the periphery of Pd seeds with the structure of an ultrathin nanosheet through the island growth mode. In combination with selective etching of Pd nanosheets, Au nanorings are eventually produced. We can control the outer diameter and wall thickness of the nanorings by simply varying the size of the Pd nanosheets and reaction time. By taking the advantage of this size controllability, the nanorings show tunable surface plasmonic properties in the near infrared (NIR) region arising from both the in-plane dipole and face resonance modes. Owing to their good surface plasmonic properties, the nanorings show substantially enhanced surface-enhanced Raman spectroscopy (SERS) performance for rhodamine 6G, and are therefore confirmed as good SERS substrates to detect trace amounts of molecules.Nanorings made of noble metals such as Au and Ag have attracted particular interest in plasmonic properties since they allow remarkable tunability of plasmon resonance wavelengths associated with their unique structural features. Unfortunately, most of the syntheses for Au nanorings involve complex procedures and/or require highly specialized and expensive facilities. Here, we report a seed-mediated approach for selective deposition of Au nanorings on the periphery of Pd seeds with the structure of an ultrathin nanosheet through the island growth mode. In combination with selective etching of Pd nanosheets, Au nanorings are eventually produced. We can control the outer diameter and wall thickness of the nanorings by simply varying the size of the Pd nanosheets and reaction time. By taking the advantage of this size controllability, the nanorings show tunable surface plasmonic properties in the near infrared (NIR) region arising from both the in-plane dipole and face resonance modes. Owing to their good surface plasmonic properties, the nanorings show substantially enhanced surface-enhanced Raman spectroscopy (SERS) performance for rhodamine 6G, and are therefore confirmed as good SERS substrates to detect trace amounts of molecules. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08613b

Biosynthesis of size-controlled gold nanoparticles using fungus, Penicillium sp.

PubMed

Zhang, Xiaorong; He, Xiaoxiao; Wang, Kemin; Wang, Yonghong; Li, Huimin; Tan, Weihong

2009-10-01

The unique optoelectronic and physicochemical properties of gold nanoparticles are significantly dependent on the particle size, shape and structure. In this paper, biosynthesis of size-controlled gold nanoparticles using fungus Penicillium sp. is reported. Fungus Penicillium sp. could successfully bioreduce and nucleate AuCl4(-) ions, and lead to the assembly and formation of intracellular Au nanoparticles with spherical morphology and good monodispersity after exposure to HAuCl4 solution. Reaction temperature, as an important physiological parameter for fungus Penicillium sp. growth, could significantly control the size of the biosynthesized Au nanoparticles. The biological compositions and FTIR spectra analysis of fungus Penicillium sp. exposed to HAuCl4 solution indicated the intracellular reducing sugar played an important role in the occurrence of intracellular reduction of AuCl4(-) ions and the growth of gold nanoparticles. Furthermore, the intracellular gold nanoparticles could be easily separated from the fungal cell lysate by ultrasonication and centrifugation.

A facile construction of Au nanoparticles stabilized by thermo-responsive polymer-tethered carbon dots for enhanced catalytic performance

NASA Astrophysics Data System (ADS)

Li, Li; Zhang, Tianyi; Lü, Jianhua; Lü, Changli

2018-10-01

Carbon dots (CDs), the youngest member in the carbon nanomaterial family, have drawn considerable attention due to their interesting optical, physicochemical and electronic properties as well as broad promising applications. Here, we developed a facile and effective strategy for the preparation of Au nanoparticles stabilized by thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) functionalized carbon dots (Au@CD@P) under the gentle water media. The as-designed dopamine(DA)-terminated PNIPAM can be easily anchored to CDs via mussel-inspired chemistry route. Both CD@P and CDs could well stabilize the Au nanoparticles with interesting assembled structure. The as-prepared Au@CD and Au@CD@P nanohybrids with good dispersibility and stability exhibited the intriguing catalytic activity for reduction of p-nitrophenol (p-NP). Especially, Au@CD@P as catalyst also played a switching role in regulating the catalytic rate by temperature. In addition, Au@CD@P exhibited excellent recyclability which may have potential in green chemical industry for developing high-activity catalysts and easy production methods.

Au/Si nanorod-based biosensor for food pathogen detection

USDA-ARS?s Scientific Manuscript database

Technical Abstract Among several potentials of nanotechnology applications for food industry, development of nanoscale sensors for food safety and quality measurement are emerging. A novel biosensor for Salmonella detection was developed using Au/Si nanorods. The Si nanorods were fabricated by gla...

Au/Si Hetero-Nanorod-based Biosensor for Salmonella Detection

USDA-ARS?s Scientific Manuscript database

Technical Abstract Among several potentials of nanotechnology applications for food industry, development of nanoscale sensors for food safety and biosecurity measurement are emerging. A novel biosensor for Salmonella detection was developed using Au/Si nanorods. The Si nanorods were fabricated by...

GMR sensors with linear and unhysteretic R(H) dependences

NASA Astrophysics Data System (ADS)

Stobiecki, F.; Szymański, B.; Luciński, T.; Dubowik, J.; Urbaniak, M.; Schmidt, M.; Röll, K.

2004-05-01

Magnetoresistance effect of Ni-Fe/Au/Co/Au sputtered multilayers was investigated. These new GMR structures, consisting of ferromagnetic layers with alternating in-plane (Ni-Fe) and out-of-plane (Co) magnetization configurations at remanence show magnetoresistive behavior attractive for some applications.

Efficient adsorption of Au(CN)2- from gold cyanidation with graphene oxide-polyethylenimine hydrogel as adsorbent

NASA Astrophysics Data System (ADS)

Yang, Lang; Jia, Feifei; Yang, Bingqiao; Song, Shaoxian

The adsorption of gold cyanide complex ion (Au(CN)2-) on graphene oxide-polyethylenimine hydrogel (GO/PEI hydrogel) from gold cyanidation has been studied to explore the possibility of the application of GO/PEI hydrogel in gold cyanidation process for extracting gold from ores. The adsorption was carried out in artificial Au(CN)2- aqueous solution with GO/PEI hydrogel as adsorbent. The experimental results, as well as IR, XPS and SEM-EDS, have shown that GO/PEI hydrogel exhibited a high adsorption capacity and a fast adsorption rate of Au(CN)2-, suggesting that GO/PEI hydrogel might be a good adsorbent for the recovery of Au(CN)2-. The adsorption of Au(CN)2- on GO/PEI hydrogel obeyed the Langmuir isotherm model and fitted well with the pseudo second order model. The good recovery of Au(CN)2- was largely related to the porous structure, large specific surface area, as well as the oxygenous functional groups on the surface of GO/PEI hydrogel.

In vitro studies on radiosensitization effect of glucose capped gold nanoparticles in photon and ion irradiation of HeLa cells

NASA Astrophysics Data System (ADS)

Kaur, Harminder; Pujari, Geetanjali; Semwal, Manoj K.; Sarma, Asitikantha; Avasthi, Devesh Kumar

2013-04-01

Noble metal nanoparticles are of great interest due to their potential applications in diagnostics and therapeutics. In the present work, we synthesized glucose capped gold nanoparticle (Glu-AuNP) for internalization in the HeLa cell line (human cervix cancer cells). The capping of glucose on Au nanoparticle was confirmed by Raman spectroscopy. The Glu-AuNP did not show any toxicity to the HeLa cell. The γ-radiation and carbon ion irradiation of HeLa cell with and without Glu-AuNP were performed to evaluate radiosensitization effects. The study revealed a significant reduction in radiation dose for killing the HeLa cells with internalized Glu-AuNPs as compared to the HeLa cells without Glu-AuNP. The Glu-AuNP treatment resulted in enhancement of radiation effect as evident from increase in relative biological effectiveness (RBE) values for carbon ion irradiated HeLa cells.

Catalysis of aptamer-modified AuPd nanoalloy probe and its application to resonance scattering detection of trace UO(2)2+.

PubMed

Liang, Aihui; Zhang, Yi; Fan, Yanyan; Chen, Chunqiang; Wen, Guiqing; Liu, Qingye; Kang, Caiyan; Jiang, Zhiliang

2011-08-01

AuPd nanoalloy and nanopalladium with a diameter of 5 nm were prepared, using sodium citrate as the stabilizing agent and NaBH(4) as the reductant. The nanocatalyst containing palladium on the surface exhibited a strong catalytic effect on the slow NiP particle reaction between NiCl(2) and NaH(2)PO(2), and the NiP particle system showed a resonance scattering (RS) peak at 508 nm. The RS results showed that the Pd atom on AuPd nanoalloy surface is the catalytic center. Combining the aptamer cracking reaction of double-stranded DNA (dsDNA)-UO(2)(2+), AuPd nanoalloy aggregation, and AuPd nanoalloy catalysis, both AuPd nanoalloy RS probe and AuPd nanoalloy catalytic RS assays were developed for the determination of 40-250 pmol L(-1) UO(2)(2+) and 5.0-50 pmol L(-1) UO(2)(2+), respectively. This journal is © The Royal Society of Chemistry 2011

Techniques for Accurate Sizing of Gold Nanoparticles Using Dynamic Light Scattering with Particular Application to Chemical and Biological Sensing Based on Aggregate Formation.

PubMed

Zheng, Tianyu; Bott, Steven; Huo, Qun

2016-08-24

Gold nanoparticles (AuNPs) have found broad applications in chemical and biological sensing, catalysis, biomolecular imaging, in vitro diagnostics, cancer therapy, and many other areas. Dynamic light scattering (DLS) is an analytical tool used routinely for nanoparticle size measurement and analysis. Due to its relatively low cost and ease of operation in comparison to other more sophisticated techniques, DLS is the primary choice of instrumentation for analyzing the size and size distribution of nanoparticle suspensions. However, many DLS users are unfamiliar with the principles behind the DLS measurement and are unware of some of the intrinsic limitations as well as the unique capabilities of this technique. The lack of sufficient understanding of DLS often leads to inappropriate experimental design and misinterpretation of the data. In this study, we performed DLS analyses on a series of citrate-stabilized AuNPs with diameters ranging from 10 to 100 nm. Our study shows that the measured hydrodynamic diameters of the AuNPs can vary significantly with concentration and incident laser power. The scattered light intensity of the AuNPs has a nearly sixth order power law increase with diameter, and the enormous scattered light intensity of AuNPs with diameters around or exceeding 80 nm causes a substantial multiple scattering effect in conventional DLS instruments. The effect leads to significant errors in the reported average hydrodynamic diameter of the AuNPs when the measurements are analyzed in the conventional way, without accounting for the multiple scattering. We present here some useful methods to obtain the accurate hydrodynamic size of the AuNPs using DLS. We also demonstrate and explain an extremely powerful aspect of DLS-its exceptional sensitivity in detecting gold nanoparticle aggregate formation, and the use of this unique capability for chemical and biological sensing applications.

An albumin-based gold nanocomposites as potential dual mode CT/MRI contrast agent

NASA Astrophysics Data System (ADS)

Zhao, Wenjing; Chen, Lina; Wang, Zhiming; Huang, Yuankui; Jia, Nengqin

2018-02-01

In pursuit of the biological detection applications, recent years have witnessed the prosperity of novel multi-modal nanoprobes. In this study, biocompatible bovine serum albumin (BSA)-coated gold nanoparticles (Au NPs) containing Gd (III) as the contrast agent for both X-ray CT and T1-weighted MR imaging is reported. Firstly, the Au NPs with BSA coating (Au@BSA) was prepared through a moderate one-pot reduction route in the presence of hydrazine hydrate as reducer. Sequentially, the BSA coating enables modification of diethylenetriaminepentaacetic acid (DTPA) as well as targeting reagent hyaluronic acid (HA), and further chelation of Gd (III) ions led to the formation of biomimetic nanoagent HA-targeted Gd-Au NPs (HA-targeted Au@BSA-Gd-DTPA). Several techniques were used to thoroughly characterize the formed HA-targeted Gd-Au NPs. As expected, the as-prepared nanoagent with mean diameter of 13.82 nm exhibits not only good colloid stablility and water dispersibility, but also satisfying low cytotoxicity and hemocompatibility in the tested concentration range. Additionally, for the CT phantoms, the obtained nanocomplex shows an improved contrast in CT scanning than that of Au@BSA as well as small molecule iodine-based CT contrast agents such as iopromide. Meanwhile, for the T1-weighted MRI images, there is a linear increase of contrast with concentration of Gd for the two cases of HA-targeted Gd-Au NPs and Magnevist. Strikingly, the nanoagent we explored displays a relatively higher r1 relaxivity than that of commercial MR contrast agents. Therefore, this newly constructed nanoagent could be used as contrast agents for synergistically enhanced X-ray CT and MR phantoms, holding promising potential for future biomedical applications.

Visual detection of telomerase activity with a tunable dynamic range by using a gold nanoparticle probe-based hybridization protection strategy

NASA Astrophysics Data System (ADS)

Wang, Jiasi; Wu, Li; Ren, Jinsong; Qu, Xiaogang

2014-01-01

We developed a novel telomere complementary (TC) oligonucleotide modified AuNP probe (TC-AuNPs) for colorimetric analysis of telomerase activity. The mechanism of this method is that the telomerase reaction products (TRP), which can hybridize with the TC-AuNPs, are able to protect the AuNPs from the aggregation induced by salt. It is demonstrated that the colorimetric method enabled the analysis of the telomerase activity in 1000 HeLa cells with the naked eye, and down to 100 HeLa cells with the aid of UV-Vis spectroscopy. This strategy is not only convenient and sensitive, but also has a tunable dynamic range. The platform is also applicable for the initial screening of a telomerase inhibitor to discover new anticancer drugs.We developed a novel telomere complementary (TC) oligonucleotide modified AuNP probe (TC-AuNPs) for colorimetric analysis of telomerase activity. The mechanism of this method is that the telomerase reaction products (TRP), which can hybridize with the TC-AuNPs, are able to protect the AuNPs from the aggregation induced by salt. It is demonstrated that the colorimetric method enabled the analysis of the telomerase activity in 1000 HeLa cells with the naked eye, and down to 100 HeLa cells with the aid of UV-Vis spectroscopy. This strategy is not only convenient and sensitive, but also has a tunable dynamic range. The platform is also applicable for the initial screening of a telomerase inhibitor to discover new anticancer drugs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05185d

Formation of Au nano-patterns on various substrates using simplified nano-transfer printing method

NASA Astrophysics Data System (ADS)

Kim, Jong-Woo; Yang, Ki-Yeon; Hong, Sung-Hoon; Lee, Heon

2008-06-01

For future device applications, fabrication of the metal nano-patterns on various substrates, such as Si wafer, non-planar glass lens and flexible plastic films become important. Among various nano-patterning technologies, nano-transfer print method is one of the simplest techniques to fabricate metal nano-patterns. In nano-transfer printing process, thin Au layer is deposited on flexible PDMS mold, containing surface protrusion patterns, and the Au layer is transferred from PDMS mold to various substrates due to the difference of bonding strength of Au layer to PDMS mold and to the substrate. For effective transfer of Au layer, self-assembled monolayer, which has strong bonding to Au, is deposited on the substrate as a glue layer. In this study, complicated SAM layer coating process was replaced to simple UV/ozone treatment, which can activates the surface and form the -OH radicals. Using simple UV/ozone treatments on both Au and substrate, Au nano-pattern can be successfully transferred to as large as 6 in. diameter Si wafer, without SAM coating process. High fidelity transfer of Au nano-patterns to non-planar glass lens and flexible PET film was also demonstrated.

Structural and morphological peculiarities of hybrid Au/nanodiamond engineered nanostructures

NASA Astrophysics Data System (ADS)

Matassa, Roberto; Orlanducci, Silvia; Reina, Giacomo; Cassani, Maria Cristina; Passeri, Daniele; Terranova, Maria Letizia; Rossi, Marco

2016-08-01

Nanostructured Au nano-platelets have been synthesized from an Au(III) complex by growth process triggered by nanodiamond (ND). An electroless synthetic route has been used to obtain 2D Au/ND architectures, where individual nanodiamond particles are intimately embedded into face-centered cubic Au platelets. The combined use of high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), was able to reveal the unusual organization of these hybrid nanoparticles, ascertaining the existence of preferential crystallographic orientations for both nanocrystalline species and highlighting their mutual locations. Detailed information on the sample microstructure have been gathered by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) of HR-TEM images, allowing us to figure out the role of Au defects, able to anchor ND crystallites and to provide specific sites for heteroepitaxial Au growth. Aggregates constituted by coupled ND and Au, represent interesting systems conjugating the best optoelectronics and plasmonics properties of the two different materials. In order to promote realistically the applications of such outstanding Au/ND materials, the cooperative mechanisms at the basis of material synthesis and their influence on the details of the hybrid nanostructures have to be deeply understood.

Structural and morphological peculiarities of hybrid Au/nanodiamond engineered nanostructures

PubMed Central

Matassa, Roberto; Orlanducci, Silvia; Reina, Giacomo; Cassani, Maria Cristina; Passeri, Daniele; Terranova, Maria Letizia; Rossi, Marco

2016-01-01

Nanostructured Au nano-platelets have been synthesized from an Au(III) complex by growth process triggered by nanodiamond (ND). An electroless synthetic route has been used to obtain 2D Au/ND architectures, where individual nanodiamond particles are intimately embedded into face-centered cubic Au platelets. The combined use of high resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED), was able to reveal the unusual organization of these hybrid nanoparticles, ascertaining the existence of preferential crystallographic orientations for both nanocrystalline species and highlighting their mutual locations. Detailed information on the sample microstructure have been gathered by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) of HR-TEM images, allowing us to figure out the role of Au defects, able to anchor ND crystallites and to provide specific sites for heteroepitaxial Au growth. Aggregates constituted by coupled ND and Au, represent interesting systems conjugating the best optoelectronics and plasmonics properties of the two different materials. In order to promote realistically the applications of such outstanding Au/ND materials, the cooperative mechanisms at the basis of material synthesis and their influence on the details of the hybrid nanostructures have to be deeply understood. PMID:27514638

Facile Syntheses of Monodisperse Ultra-Small Au Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bertino, Massimo F.; Sun, Zhong-Ming; Zhang, Rui

2006-11-02

During our effort to synthesize the tetrahedral Au20 cluster, we found a facile synthetic route to prepare monodisperse suspensions of ultra-small Au clusters AuN (N<12) using diphosphine ligands. In our monophasic and single-pot synthesis, a Au precursor ClAu(I)PPh3 and a bidentate phosphine ligand P(Ph)2(CH2)MP(Ph)2 (Ph = phenyl) are dissolved in an organic solvent. Au(I) is reduced slowly by a borane-tert-butylamine complex to form Au clusters coordinated by the diphosphine ligand. The Au clusters are characterized by both high resolution mass spectrometry and UV-Vis absorption spectroscopy. We found that the mean cluster size obtained depends on the chain length M ofmore » the ligand. In particular, a single monodispersed Au11 cluster is obtained with the P(Ph)2(CH2)3P(Ph)2 ligand, whereas P(Ph)2(CH2)MP(Ph)2 ligands with M = 5 and 6 yield Au10 and Au8 clusters. The simplicity of our synthetic method makes it suitable for large-scale production of nearly monodisperse ultrasmall Au clusters. It is suggested that diphosphines provide a set of flexible ligands to allow size-controlled synthesis of Au nanoparticles.« less

Dark field microscopic analysis of discrete Au nanostructures: Understanding the correlation of scattering with stoichiometry

NASA Astrophysics Data System (ADS)

Wang, Guoqing; Bu, Tong; Zako, Tamotsu; Watanabe-Tamaki, Ryoko; Tanaka, Takuo; Maeda, Mizuo

2017-09-01

Due to the potential of gold nanoparticle (AuNP)-based trace analysis, the discrimination of small AuNP clusters with different assembling stoichiometry is a subject of fundamental and technological importance. Here we prepare oligomerized AuNPs with controlled stoichiometry through DNA-directed assembly, and demonstrate that AuNP monomers, dimers and trimers can be clearly distinguished using dark field microscopy (DFM). The scattering intensity for of AuNP structures with stoichiometry ranging from 1 to 3 agrees well with our theoretical calculations. This study demonstrates the potential of utilizing the DFM approach in ultra-sensitive detection as well as the use of DNA-directed assembly for plasmonic nano-architectures.

Volume-confined synthesis of ligand-free gold nanoparticles with tailored sizes for enhanced catalytic activity

NASA Astrophysics Data System (ADS)

Shaik, Firdoz; Zhang, Weiqing; Niu, Wenxin; Lu, Xianmao

2014-10-01

Ligand-free Au nanoparticles with controlled sizes are synthesized via a volume-confined method. In this synthesis, mesoporous hollow silica shells (mHSS) are used as nano-containers for the impregnation of HAuCl4 solution before they are separated from the bulk solution. With a simple heating process, the Au precursor confined within the cavity of the isolated hollow shells is converted into ligand-free Au nanoparticles. The size of the Au nanoparticles can be tuned precisely by loading HAuCl4 solution of different concentrations, or by using mHSS with different cavity volumes. The ligand-free Au nanoparticles demonstrate superior catalytic activity than sodium citrate-capped Au nanoparticles.

Fabrication and characterization of optical sensors using metallic core-shell thin film nanoislands for ozone detection

NASA Astrophysics Data System (ADS)

Addanki, Satish; Nedumaran, D.

2017-07-01

Core-Shell nanostructures play a vital role in the sensor field owing to their performance improvements in sensing characteristics and well-established synthesis procedures. These nanostructures can be ingeniously tuned to achieve tailored properties for a particular application of interest. In this work, an Ag-Au core-shell thin film nanoislands with APTMS (3-Aminopropyl trimethoxysilane) and PVA (Polyvinyl alcohol) binding agents was modeled, synthesized and characterized. The simulation results were used to fabricate the sensor through chemical route. The results of this study confirmed that the APTMS based Ag-Au core-shell thin film nanoislands offered a better performance over the PVA based Ag-Au core-shell thin film nanoislands. Also, the APTMS based Ag-Au core-shell thin film nanoislands exhibited better sensitivity towards ozone sensing over the other types, viz., APTMS/PVA based Au-Ag core-shell and standalone Au/Ag thin film nanoislands.

Direct patterning of gold nanoparticles using flexographic printing for biosensing applications

NASA Astrophysics Data System (ADS)

Benson, Jamie; Fung, Chung Man; Lloyd, Jonathan Stephen; Deganello, Davide; Smith, Nathan Andrew; Teng, Kar Seng

2015-03-01

In this paper, we have presented the use of flexographic printing techniques in the selective patterning of gold nanoparticles (AuNPs) onto a substrate. Highly uniform coverage of AuNPs was selectively patterned on the substrate surface, which was subsequently used in the development of a glucose sensor. These AuNPs provide a biocompatible site for the attachment of enzymes and offer high sensitivity in the detection of glucose due to their large surface to volume ratio. The average size of the printed AuNPs is less than 60 nm. Glucose sensing tests were performed using printed carbon-AuNP electrodes functionalized with glucose oxidase (GOx). The results showed a high sensitivity of 5.52 μA mM-1 cm-2 with a detection limit of 26 μM. We have demonstrated the fabrication of AuNP-based biosensors using flexographic printing, which is ideal for low-cost, high-volume production of the devices.

Tuning the nonlinear optical absorption in Au/BaTiO3 nanocomposites with gold nanoparticle concentration

NASA Astrophysics Data System (ADS)

Bijeesh, M. M.; Shakhi, P. K.; Varier, Geetha K.; Nandakumar, P.

2018-06-01

We report on the nonlinear optical absorption coefficient of Au/BaTiO3 nanocomposite films and its dependence on gold nanoparticle concentration. Au/BaTiO3 nanocomposite films with different molar ratio of Au/Ba are prepared by sol-gel technique and characterized by X-ray diffraction, UV Visible absorption spectroscopy and high resolution transmission electron microscopy. An open aperture Z-scan technique is employed to study the third order nonlinear optical properties of Au/BaTiO3 thin films. An Nd:YAG laser operating at 532 nm wavelength having a pulse width of 5 ns is used for the measurements. The two-photon absorption coefficient of the films increases linearly with gold nanoparticle concentration and significant enhancement of nonlinear optical absorption is observed. This ability to fine tune the nonlinear optical coefficients of Au/BaTiO3 films would be handy in optical device applications.

Physiological stability and renal clearance of ultrasmall zwitterionic gold nanoparticles: Ligand length matters

NASA Astrophysics Data System (ADS)

Ning, Xuhui; Peng, Chuanqi; Li, Eric S.; Xu, Jing; Vinluan, Rodrigo D.; Yu, Mengxiao; Zheng, Jie

2017-05-01

Efficient renal clearance has been observed from ultrasmall zwitterionic glutathione-coated gold nanoparticles (GS-AuNPs), which have broad preclinical applications in cancer diagnosis and kidney functional imaging. However, origin of such efficient renal clearance is still not clear. Herein, we conducted head-to-head comparison on physiological stability and renal clearance of two zwitterionic luminescent AuNPs coated with cysteine and glycine-cysteine (Cys-AuNPs and Gly-Cys-AuNPs), respectively. While both of them exhibited similar surface charges and the same core sizes, additional glycine slightly increased the hydrodynamic diameter of the AuNPs by 0.4 nm but significantly enhanced physiological stability of the AuNPs as well as altered their clearance pathways. These studies indicate that the ligand length, in addition to surface charges and size, also plays a key role in the physiological stability and renal clearance of ultrasmall zwitterionic inorganic NPs.

Single cytidine units-templated syntheses of multi-colored water-soluble Au nanoclusters.

PubMed

Jiang, Hui; Zhang, Yuanyuan; Wang, Xuemei

2014-09-07

Ultra-small metallic nanoparticles, or so-called "nanoclusters" (NCs), have attracted considerable interest due to their unique optical properties that are different from both larger nanoparticles and single atoms. To prepare high-quality NCs, the stabilizing agent plays an essential role. In this work, we have revealed and validated that cytidine and its nucleotides (cytidine 5'-monophosphate or cytidine 5'-triphosphate) can act as efficient stabilizers for syntheses of multicolored Au NCs. Interestingly, Au NCs with blue, green and yellow fluorescence emissions are simultaneously obtained using various pH environments or reaction times. The transmission electron microscopy verifies that the size of Au NCs ranges from 1.5 to 3 nm. The X-ray photoelectron spectroscopy confirms that only Au (0) species are present in NCs. Generally, the facile preparation of multicolored Au NCs that are stabilized by cytidine units provides access to promising candidates for multiple biolabeling applications.

Application of Direct Current Atmospheric Pressure Glow Microdischarge Generated in Contact with a Flowing Liquid Solution for Synthesis of Au-Ag Core-Shell Nanoparticles

PubMed Central

Dzimitrowicz, Anna; Jamroz, Piotr; Nyk, Marcin; Pohl, Pawel

2016-01-01

A direct current atmospheric pressure glow microdischarge (dc-μAPGD) generated between an Ar nozzle microjet and a flowing liquid was applied to produce Au-Ag core-shell nanoparticles (Au@AgCSNPs) in a continuous flow system. Firstly, operating dc-μAPGD with the flowing solution of the Au(III) ions as the cathode, the Au nanoparticles (AuNPs) core was produced. Next, to produce the core-shell nanostructures, the collected AuNPs solution was immediately mixed with an AgNO3 solution and passed through the system with the reversed polarity to fabricate the Ag nanoshell on the AuNPs core. The formation of Au@AgCSNPs was confirmed using ultraviolet-visible (UV-Vis) absorbance spectrophotometry, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Three localized surface plasmon resonance absorption bands with wavelengths centered at 372, 546, and 675 nm were observed in the UV-Vis spectrum of Au@AgCSNPs, confirming the reduction of both the Au(III) and Ag(I) ions. The right configuration of metals in Au@AgCSNPs was evidenced by TEM. The Au core diameter was 10.2 ± 2.0 nm, while the thickness of the Ag nanoshell was 5.8 ± 1.8 nm. The elemental composition of the bimetallic nanoparticles was also confirmed by EDS. It is possible to obtain 90 mL of a solution containing Au@AgCSNPs per hour using the applied microdischarge system. PMID:28773393

Gallic acid conjugated with gold nanoparticles: antibacterial activity and mechanism of action on foodborne pathogens

PubMed Central

Rattanata, Narintorn; Klaynongsruang, Sompong; Leelayuwat, Chanvit; Limpaiboon, Temduang; Lulitanond, Aroonlug; Boonsiri, Patcharee; Chio-Srichan, Sirinart; Soontaranon, Siriwat; Rugmai, Supagorn; Daduang, Jureerut

2016-01-01

Foodborne pathogens, including Plesiomonas shigelloides and Shigella flexneri B, are the major cause of diarrheal endemics worldwide. Antibiotic drug resistance is increasing. Therefore, bioactive compounds with antibacterial activity, such as gallic acid (GA), are needed. Gold nanoparticles (AuNPs) are used as drug delivery agents. This study aimed to conjugate and characterize AuNP–GA and to evaluate the antibacterial activity. AuNP was conjugated with GA, and the core–shell structures were characterized by small-angle X-ray scattering and transmission electron microscopy. Antibacterial activity of AuNP–GA against P. shigelloides and S. flexneri B was evaluated by well diffusion method. AuNP–GA bactericidal mechanism was elucidated by Fourier transform infrared microspectroscopic analysis. The results of small-angle X-ray scattering showed that AuNP–GA conjugation was successful. Antibacterial activity of GA against both bacteria was improved by conjugation with AuNP because the minimum inhibitory concentration value of AuNP–GA was significantly decreased (P<0.0001) compared to that of GA. Fourier transform infrared analysis revealed that AuNP–GA resulted in alterations of lipids, proteins, and nucleic acids at the bacterial cell membrane. Our findings show that AuNP–GA has potential for further application in biomedical sciences. PMID:27555764

Gallic acid conjugated with gold nanoparticles: antibacterial activity and mechanism of action on foodborne pathogens.

PubMed

Rattanata, Narintorn; Klaynongsruang, Sompong; Leelayuwat, Chanvit; Limpaiboon, Temduang; Lulitanond, Aroonlug; Boonsiri, Patcharee; Chio-Srichan, Sirinart; Soontaranon, Siriwat; Rugmai, Supagorn; Daduang, Jureerut

2016-01-01

Foodborne pathogens, including Plesiomonas shigelloides and Shigella flexneri B, are the major cause of diarrheal endemics worldwide. Antibiotic drug resistance is increasing. Therefore, bioactive compounds with antibacterial activity, such as gallic acid (GA), are needed. Gold nanoparticles (AuNPs) are used as drug delivery agents. This study aimed to conjugate and characterize AuNP-GA and to evaluate the antibacterial activity. AuNP was conjugated with GA, and the core-shell structures were characterized by small-angle X-ray scattering and transmission electron microscopy. Antibacterial activity of AuNP-GA against P. shigelloides and S. flexneri B was evaluated by well diffusion method. AuNP-GA bactericidal mechanism was elucidated by Fourier transform infrared microspectroscopic analysis. The results of small-angle X-ray scattering showed that AuNP-GA conjugation was successful. Antibacterial activity of GA against both bacteria was improved by conjugation with AuNP because the minimum inhibitory concentration value of AuNP-GA was significantly decreased (P<0.0001) compared to that of GA. Fourier transform infrared analysis revealed that AuNP-GA resulted in alterations of lipids, proteins, and nucleic acids at the bacterial cell membrane. Our findings show that AuNP-GA has potential for further application in biomedical sciences.

Fabrication of transition metal-containing nanostructures via polymer templates for a multitude of applications

NASA Astrophysics Data System (ADS)

Lu, Jennifer Qing

Nanostructures such as carbon nanotubes and semiconducting nanowires offer great technological promise due to their remarkable properties. The lack of a rational synthesis method prevents fabricating these nanostructures with desirable and consistent properties at predefined locations for device applications. In this thesis, employing polymer templates, a variety of highly ordered catalytically active transition metal nanostructures, ranging from single metallic nanoparticles of Fe, Co, Ni, Au and bimetallic nanoparticles of Ni/Fe and Co/Mo to Fe-rich silicon oxide nanodomains with uniform and tunable size and spacing have been successfully synthesized. These nanostructures have been demonstrated to be excellent catalyst systems for the synthesis of carbon nanotube and silicon nanowire. High quality, small diameter carbon nanotubes and nanowires with narrow size distribution have been successfully attained. Because these catalytically active nanostructures are uniformly distributed and do not agglomerate at the growth temperatures, uniform, high density and high quality carbon nanotube mats have been obtained. Since this polymer template approach is fully compatible with conventional top-down photolithography, lithographically selective growth of carbon nanotubes on a surface or suspended carbon nanotubes across trenches have been produced by using existing semiconductor processing. We have also shown the feasibility of producing carbon nanotubes and silicon nanowires at predefined locations on a wafer format and established a wafer-level carbon nanotube based device fabrication process. The ability of the polymer template approach to control catalyst systems at the nano-, micro- and macro-scales paves a pathway for commercialization of these 1D nanostructure-enabled devices. Beside producing well-defined, highly ordered discrete catalytically active metal-containing nanostructures by the polymer template approach, Au and Ag nanotextured surfaces have also been attained by using a self-assembled ferrocenylsilane-based inorganic block copolymer template. These Au and Ag nanotextured surfaces exhibit different surface plasmon behavior than the nanotextured surface. Greatly enhanced and uniform Raman scattering have been observed on Ag nanotextured surfaces. Highly sensitive Au nanotextured surfaces suggest their potential application as sensing surfaces for SPR-based biodetection. This simple fabrication technique of producing inorganic nanostructures with adjustable properties such as size, spacing and composition offers great promise for both fundamental research and technological development.

Green synthesis of Au nanoparticles using potato extract: stability and growth mechanism

NASA Astrophysics Data System (ADS)

Castillo-López, D. N.; Pal, U.

2014-08-01

We report on the synthesis of spherical, well-dispersed colloidal gold nanoparticles of 17.5-23.5 nm average sizes in water using potato extract (PE) both as reducing and stabilizing agent. The effects of PE content and the pH value of the reaction mixture have been studied. Formation and growth dynamics of the Au nanoparticles in the colloids were studied using transmission electron microscopy and UV-Vis optical absorption spectroscopy techniques. While the reductor content and, hence, the nucleation and growth rates of the nanoparticles could be controlled by controlling the PE content in the reaction solution, the stability of the nanoparticles depended strongly on the pH of the reaction mixture. The mechanisms of Au ion reduction and stabilization of Au nanoparticles by potato starch have been discussed. The use of common natural solvent like water and biological reductor like PE in our synthesis process opens up the possibility of synthesizing Au nanoparticles in fully green (environmental friendly) way, and the Au nanoparticles produced in such way should have good biocompatibility.

One pot synthesis of dandelion-like polyaniline coated gold nanoparticles composites for electrochemical sensing applications.

PubMed

Lu, Zhiwei; Dai, Wanlin; Liu, Baichen; Mo, Guangquan; Zhang, Junjun; Ye, Jiaping; Ye, Jianshan

2018-04-18

In this work, we report a facile and green strategy for one pot and in-situ synthesis of a dandelion-like conductive polyaniline coated gold nanoparticle nanocomposites (Au@PANI). The Au@PANI was characterized by SEM, TEM, XRD, TGA, FTIR, UV-vis and conductivity measurement, respectively. Newly-designed Au@PANI materials possessed a significantly high conductivity and strong adsorption capability. Thus, the Au@PANI modified glassy carbon electrode (GCE) was utilized for construct a novel electrochemical sensor for the simultaneous assay of Pb 2+ and Cu 2+ using square wave anodic stripping voltammetry (SWASV). Under the optimized conditions, an excellent electrochemical response in the simultaneous of Pb 2+ and Cu 2+ with detection limit of 0.003 and 0.008 μM (S/N = 3), respectively. Moreover, the prepared sensors realized an excellent reproducibility, repeatability and long term stability, as well as reliable practical assays in real water samples. Besides, the possible formation mechanism and sensing mechanism of Au@PANI nanocomposites have been discussed in detail. We believe this study provides a novel method of fabrication of noble metal nanoparticles decorated conducting polymer materials for the electrochemical sensing applications. Copyright © 2018 Elsevier Inc. All rights reserved.

Gold nanorods-enhanced rhodamine B-permanganate chemiluminescence and its analytical application.

PubMed

Hassanzadeh, Javad; Amjadi, Mohammad; Manzoori, Jamshid L; Sorouraddin, Mohammad Hossein

2013-04-15

A novel enhanced chemiluminescence system was developed by applying gold nanorods (Au NRs) as catalysts in rhodamine B-permanganate reaction. Au NRs with three different aspect ratios were synthesized by seed mediated growth method and characterized by UV-Vis spectra and transmission electron microscopy. It was demonstrated that Au NRs have much higher catalytic effect than spherical nanoparticles on rhodamine B-permanganate chemiluminescence reaction. Among various sizes of Au NRs, those with average aspect ratio of 3.0 were found to have the most remarkable catalytic activity. As an analytical application of the new chemiluminescence system, albumin as a model protein was quantified based on its interaction with NRs. Albumin binds to Au NRs active surfaces and inhibits their catalytic action and therefore decreases the intensity of chemiluminescence. This diminution effect is linearly related to the concentration of the human and bovine serum albumin over the ranges of 0.45-90 and 0.75-123 nmol L(-1), respectively with the corresponding limits of detection of 0.18 and 0.30 nmol L(-1). The method was successfully applied to the determination of albumin in human and bovine serum samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Tailoring dispersion and aggregation of Au nanoparticles in the BHJ layer of polymer solar cells: plasmon effects versus electrical effects.

PubMed

Kim, Wanjung; Cha, Bong Geun; Kim, Jung Kyu; Kang, Woonggi; Kim, Eunchul; Ahn, Tae Kyu; Wang, Dong Hwan; Du, Qing Guo; Cho, Jeong Ho; Kim, Jaeyun; Park, Jong Hyeok

2014-12-01

Plasmonic effects that arise from embedding metallic nanoparticles (NPs) in polymer solar cells (PSCs) have been extensively studied. Many researchers have utilized metallic NPs in PSCs by either incorporating them into the PSC interlayers (e.g., the hole extraction and electron extraction layers) or blending them into the bulk heterojunction (BHJ) active layer. In such studies, the dispersity of the metallic NPs in each layer may vary due to both the different nature of the ligands and the amount of ligands on the metallic NPs. This in turn can produce different PSC performance parameters. Here, we systematically control the amount of attached organic ligands on Au NPs to control their dispersion behavior in the BHJ active layer of PSCs. By controlling the number of capping organic ligands on the Au NPs, the dispersity of the NPs in the BHJ layer is also controlled and the positive effects (particularly the plasmonic and electrical effects) of the Au NPs in the PSCs are investigated. From the obtained results, we find that the electrical contribution of the Au NPs is a more dominant factor for enhancing cell efficiency when compared to the plasmonic effect. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

N-Heterocyclic-Carbene-Treated Gold Surfaces in Pentacene Organic Field-Effect Transistors: Improved Stability and Contact at the Interface.

PubMed

Lv, Aifeng; Freitag, Matthias; Chepiga, Kathryn M; Schäfer, Andreas H; Glorius, Frank; Chi, Lifeng

2018-04-16

N-Heterocyclic carbenes (NHCs), which react with the surface of Au electrodes, have been successfully applied in pentacene transistors. With the application of NHCs, the charge-carrier mobility of pentacene transistors increased by five times, while the contact resistance at the pentacene-Au interface was reduced by 85 %. Even after annealing the NHC-Au electrodes at 200 °C for 2 h before pentacene deposition, the charge-carrier mobility of the pentacene transistors did not decrease. The distinguished performance makes NHCs as excellent alternatives to thiols as metal modifiers for the application in organic field-effect transistors (OFETs). © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

DNA hydrogel as a template for synthesis of ultrasmall gold nanoparticles for catalytic applications.

PubMed

Zinchenko, Anatoly; Miwa, Yasuyuki; Lopatina, Larisa I; Sergeyev, Vladimir G; Murata, Shizuaki

2014-03-12

DNA cross-linked hydrogel was used as a matrix for synthesis of gold nanoparticles. DNA possesses a strong affinity to transition metals such as gold, which allows for the concentration of Au precursor inside a hydrogel. Further reduction of HAuCl4 inside DNA hydrogel yields well dispersed, non-aggregated spherical Au nanoparticles of 2-3 nm size. The average size of these Au nanoparticles synthesized in DNA hydrogel is the smallest reported so far for in-gel metal nanoparticles synthesis. DNA hybrid hydrogel containing gold nanoparticles showed high catalytic activity in the hydrogenation reaction of nitrophenol to aminophenol. The proposed soft hybrid material is promising as environmentally friendly and sustainable material for catalytic applications.

Photoinduced RNA interference.

PubMed

Matsushita-Ishiodori, Yuka; Ohtsuki, Takashi

2012-07-17

Because RNA interference (RNAi) can be applied to any gene, this technique has been widely used for studying gene functions. In addition, many researchers are attempting to use RNAi technology in RNAi-based therapies. However, several challenging and controversial issues have arisen during the widespread application of RNAi including target gene specificity, target cell specificity, and spatiotemporal control of gene silencing. To address these issues, several groups have utilized photochemistry to control the RNA release, both spatially and temporally. In this Account, we focus on recent studies using photocleavable protecting groups, photosensitizers, Hand gold nanoparticles for photoinduced RNAi. In 2005 the first report of photoinduced RNAi used a caged short interfering RNA (siRNA), an siRNA carrying a photocleavable protecting group. Caging groups block the bioactivities of target molecules, but allow for complete recovery of these functions via photoactivation. However, some RNAi activity can occur in these caged siRNAs, so it will be necessary to decrease this "leakage" and raise the RNAi activity restored after irradiation. This technique also uses UV light around 350 nm, which is cytotoxic, but in the near future we expect that it will be possible to use visible and near-infrared light We also examine the application of photochemical internalization (PCI) to RNAi technology, which involves a combination of photosensitizers and light. Instead of inducing RNAi using light, the strategy behind this method was to enhance RNAi using RNA carriers. Many wellknown RNA carriers deliver siRNAs into cells by endocytosis. The siRNAs are trapped in endocytic vesicles and have to be released into the cytoplasm in order to express their activity. To achieve the endosomal escape of siRNAs, PCI technology employed photosensitizers to generate light-dependent reactive oxygen species (ROS) that disrupted the endocytic vesicles. In most studies, RNAi-mediated knockdown of the target gene was detected even without PCI. Recently, a polymer capable of trapping the siRNA in endocytic vesicles controlled RNAi almost entirely by light. CLIP-RNAi uses photosensitizing carrier proteins that can be activated over a wide range of visible light wavelengths. With this method RNA carrier/siRNA complexes are completely trapped within endosomes, and RNAi is controlled strictly by light. Such precise, light-dependent control will open up new possibilities for cellular and molecular biology and therapy. Most recently, gold nanoparticles (AuNPs) conjugated to siRNA have provided temporal and spatial control of RNAi. The light-dependent melting of AuNPs accompanied by a shape transformation induces the release of thiolated siRNAs from AuNPs. In this method, the unique optical properties of the AuNP enable deep penetration of the excitation light into tissues at nearinfrared wavelengths. The development of photoinduced RNAi technology will lead to novel insights into gene functions and selective drug delivery, and many other scientific fields will continue to influence its progress.

Nonlinear absorption enhancement of AuNPs based polymer nanocomposites

NASA Astrophysics Data System (ADS)

Zulina, Natalia A.; Baranov, Mikhail A.; Kniazev, Kirill I.; Kaliabin, Viacheslav O.; Denisyuk, Igor Yu.; Achor, Susan U.; Sitnikova, Vera E.

2018-07-01

Au nanoparticles (AuNPs) based polymer nanocomposites with high nonlinear absorption coefficient were synthesized by UV-photocuring. AuNPs were synthesized by laser ablation method in liquid monomer isodecyl acrylate (IDA). In this research, two colloids with 70 nm and 20 nm nanoparticles average sizes were studied. Size control was performed with SEM and STEM. Prepared nanomaterials exhibit strong third-order nonlinear optical responses under CW laser irradiation at 532 nm, which was estimated by using z-scan technique performed with open aperture. It was found experimentally that nonlinear absorption β is almost twice higher for nanocomposites with smaller AuNPs.

Dispersion and alignment of nanorods in cylindrical block copolymer thin films.

PubMed

Rasin, Boris; Chao, Huikuan; Jiang, Guoqian; Wang, Dongliang; Riggleman, Robert A; Composto, Russell J

2016-02-21

Although significant progress has been made in controlling the dispersion of spherical nanoparticles in block copolymer thin films, our ability to disperse and control the assembly of anisotropic nanoparticles into well-defined structures is lacking in comparison. Here we use a combination of experiments and field theoretic simulations to examine the assembly of gold nanorods (AuNRs) in a block copolymer. Experimentally, poly(2-vinylpyridine)-grafted AuNRs (P2VP-AuNRs) are incorporated into poly(styrene)-b-poly(2-vinylpyridine) (PS-b-P2VP) thin films with a vertical cylinder morphology. At sufficiently low concentrations, the AuNRs disperse in the block copolymer thin film. For these dispersed AuNR systems, atomic force microscopy combined with sequential ultraviolet ozone etching indicates that the P2VP-AuNRs segregate to the base of the P2VP cylinders. Furthermore, top-down transmission electron microscopy imaging shows that the P2VP-AuNRs mainly lie parallel to the substrate. Our field theoretic simulations indicate that the NRs are strongly attracted to the cylinder base where they can relieve the local stretching of the minority block of the copolymer. These simulations also indicate conditions that will drive AuNRs to adopt a vertical orientation, namely by increasing nanorod length and/or reducing the wetting of the short block towards the substrate.

Synthesis of Gold Mediated Biocompatible Nanocomposite of Lactone Enriched Fraction from Sahadevi (Vernonia cinerea Lees): An Assessment of Antimalarial Potential.

PubMed

Jyotshna; Shanker, Karuna; Khare, Puja; Tiwari, Nimisha; Mohanty, Shilpa; Bawankule, Dnyaneshwar U; Pal, Anirban

2016-01-01

Metals reduction into submicro/nano size through bhasma preparations for therapeutic use is well established in ancient traditional system of Indian medicines i.e. Ayurveda. Recently, nanotechnology has drawn the attention of researchers to develeope various size and shape nanoparicles / composite for number of applications.In this article, we report the enrichment of lactone enriched fraction (LEF) by liquid-liquid portioning of Vernonia cinerea metabolic extract and sysnthesis of mediated nano-gold composite (LEF-AuNPs) in single step process. The morphological characteristic based on transmission electron microscope (TEM) image analysis showed that LEF-AuNPs were predominantly nanopolygons and nanobots in shapes ranging from 50-200 nm in size. Abundance of phytochemicals in both LEF and LEF-AuNPs was dissimilar. In LEF, montanol- a diterpenoid, while in LEF-AuNPs, neophytadiene- a phytanes was the major compound. HPLC profile of relatively polar compounds also varied drastically. In-vitro biocompatibility, cytotoxicity [MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) based assay] and storage stabilitiy of LEF-AuNPs were evaluated. The moderate ability of LEF-AuNPs to restrict parasitaemia, extended mean survival time of mice infected with Plasmodium berghei and lack of any evident toxicity provides new opportunities for the safe delivery and applications of such nanocomposites in malaria therapy.

Bio-synthesis of triangular and hexagonal gold nanoparticles using palm oil fronds’ extracts at room temperature

NASA Astrophysics Data System (ADS)

Usman, Adamu Ibrahim; Aziz, Azlan Abdul; Abu Noqta, Osama

2018-01-01

Development of bio-reduction techniques for nanoparticles (NPs) synthesis in medical application remains a challenge to numerous researchers. This work reports a novel technique for the synthesis of triangular and hexagonal gold nanoparticles (AuNP) using palm oil fronds’ (POFs) extracts. The functional groups in the POFs’ extracts operate as a persuasive capping and reducing agent to growth AuNPs. The prepared AuNPs were characterized using UV-vis spectrophotometry, Fourier-transform infrared (FTIR) spectroscopy, dynamic light scattering, energy filtered transmission electron microscopy (EFTEM), and x-ray diffraction (XRD). The analysis of FTIR validates the coating of alkynes and phenolic composites on the AuNPs. This shows a feasible function of biomolecules for efficient stabilization of the AuNPs. EFTEM clearly show the triangular and hexagonal shapes of the prepared AuNPs. The XRD patterns display the peaks of fcc crystal structures at (111), (200), (220), (311) and (222), with average particle sizes of 66.7 and 79.02 nm for 1% and 5% POFs extracts concentrations respectively at room temperature. While at 120 °C the average particles size recorded for 1% and 5% of POFs extract concentrations were 32.17 nm and 45.66 nm respectively, and the reaction completed in less than 2 min. The prepared NPs could be potentially applied in biomedical application, due to their excellent stability and refine morphology without agglomeration.

The effects of gold nanoparticles in wound healing with antioxidant epigallocatechin gallate and α-lipoic acid.

PubMed

Leu, Jyh-Gang; Chen, Siang-An; Chen, Han-Min; Wu, Wen-Mein; Hung, Chi-Feng; Yao, Yeong-Der; Tu, Chi-Shun; Liang, Yao-Jen

2012-07-01

Topical applications of antioxidant agents in cutaneous wounds have attracted much attention. Gold nanoparticles (AuNPs), epigallocatechin gallate (EGCG), and α-lipoic acid (ALA) were shown to have antioxidative effects and could be helpful in wound healing. Their effects in Hs68 and HaCaT cell proliferation and in mouse cutaneous wound healing were studied. Both the mixture of EGCG + ALA (EA) and AuNPs + EGCG + ALA (AuEA) significantly increased Hs68 and HaCaT proliferation and migration. Topical AuEA application accelerated wound healing on mouse skin. Immunoblotting of wound tissue showed significant increase of vascular endothelial cell growth factor and angiopoietin-1 protein expression, but no change of angiopoietin-2 or CD31 after 7 days. After AuEA treatment, CD68 protein expression decreased and Cu/Zn superoxide dismutase increased significantly in the wound area. In conclusion, AuEA significantly accelerated mouse cutaneous wound healing through anti-inflammatory and antioxidation effects. This study may support future studies using other antioxidant agents in the treatment of cutaneous wounds. In this study, topically applied gold nanoparticles with epigallocatechin gallate and alpha-lipoic acid were studied regarding their effects in wound healing in cell cultures. Significant acceleration was demonstrated in wound healing in a murine model. Copyright © 2012 Elsevier Inc. All rights reserved.

Ambient, rapid and facile deposition of polymer brushes for immobilization of plasmonic nanoparticles

NASA Astrophysics Data System (ADS)

Yilmaz, Hatice; Pekdemir, Sami; Ipekci, Hasan H.; Kiremitler, N. Burak; Hancer, Mehmet; Onses, M. Serdar

2016-11-01

The immobilization of nanoparticles (NPs) is of great interest to many technological applications and scientific fields. Methods to immobilize NPs either lack the uniformity, robustness and controllability or require complex and impractical preparation techniques. This paper aims in closing this gap by presenting practical routes in preparation of poly(2-vinyl pyridine) (P2VP) brush grafted silicon oxide terminated substrates for immobilization of NPs. Here, we demonstrate that hydroxyl-terminated P2VP can be deposited using different coating techniques and grafted in air at processing times as short as a few minutes. The grafted P2VP brushes can immobilize spherical Au nanoparticles that are 20 nm in diameter, on the surface of substrates with densities as high as ∼600 particles/μm2. The density of the immobilized NPs can be further tuned with the grafting conditions and duration of the particle treatment. More than 80% of the grafted brushes and Au NPs remain on the substrate following abrasion tests proving mechanical robustness of the coatings. The immobilized Au NPs can impart surface enhanced Raman scattering effects in sensing of molecules, illustrating a representative use of the presented platform.

Quantitative Phase Composition of TiO 2-Coated Nanoporous-Au Monoliths by X-ray Absorption Spectroscopy and Correlations to Catalytic

DOE PAGES

Bagge-Hansen, Michael; Wichmann, Andre; Wittstock, Arne; ...

2014-02-03

Porous titania/metal composite materials have many potential applications in the fields of green catalysis, energy harvesting, and storage in which both the overall morphology of the nanoporous host material and the crystallographic phase of the titania (TiO 2) guest determine the material’s performance. New insights into the structure–function relationships of these materials were obtained by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy that, for example, provides quantitative crystallographic phase composition from ultrathin, nanostructured titania films, including sensitivity to amorphous components. We demonstrate that crystallographic phase, morphology, and catalytic activity of TiO 2-functionalized nanoporous gold (np-Au) can be controlled by amore » simple annealing procedure (T < 1300 K). The material was prepared by atomic layer deposition of ~2 nm thick TiO 2 on millimeter-sized samples of np-Au (40–50 nm mean ligament size) and catalytically investigated with respect to aerobic CO oxidation. Moreover, the annealing-induced changes in catalytic activity are correlated with concurrent morphology and phase changes as provided by cross-sectional scanning electron microscopy, transmission electron microscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.« less

A three-step model for protein-gold nanoparticle adsorption

USDA-ARS?s Scientific Manuscript database

Gold nanoparticles (AuNPs) are an attractive delivery vector in biomedicine because of their low toxicity and unique electronic and chemical properties. AuNP bioconjugates can be used in many applications, including nanomaterials, biosensing, and drug delivery. While the phenomenon of spontaneous pr...

Enhancement of the thermal transport in a culture medium with Au nanoparticles

NASA Astrophysics Data System (ADS)

Jiménez-Pérez, J. L.; Fuentes, R. Gutierrez; Alvarado, E. Maldonado; Ramón-Gallegos, E.; Cruz-Orea, A.; Tánori-Cordova, J.; Mendoza-Alvarez, J. G.

2008-11-01

In this work, it is reported the gold nanoparticles synthesis, their characterization, and their application to the enhancement of the thermal transport in a cellular culture medium. The Au nanoparticles (NPs), with average size of 10 nm, contained into a culture medium (DMEM (1)/F12(1)) (CM) increased considerably the heat transfer in the medium. Thermal lens spectrometry (TLS) was used to measure the thermal diffusivity of the nanofluids. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression, for transient thermal lens, to the experimental data. Our results show that the thermal diffusivity of the culture medium is highly sensitive to the Au nanoparticle concentration and size. The ability to modify the thermal properties to nanometer scale becomes very important in medical applications as in the case of cancer treatment by using photodynamic therapy (PDT). A complementary study with UV-vis and TEM techniques was performed to characterize the Au nanoparticles.

Gold-Coated Superparamagnetic Nanoparticles for Single Methyl Discrimination in DNA Aptamers

PubMed Central

Tintoré, Maria; Mazzini, Stefania; Polito, Laura; Marelli, Marcello; Latorre, Alfonso; Somoza, Álvaro; Aviñó, Anna; Fàbrega, Carme; Eritja, Ramon

2015-01-01

Au- and iron-based magnetic nanoparticles (NPs) are promising NPs for biomedical applications due to their unique properties. The combination of a gold coating over a magnetic core puts together the benefits from adding the magnetic properties to the robust chemistry provided by the thiol functionalization of gold. Here, the use of Au-coated magnetic NPs for molecular detection of a single methylation in DNA aptamer is described. Binding of α-thrombin to two aptamers conjugated to these NPs causes aggregation, a phenomenon that can be observed by UV, DLS and MRI. These techniques discriminate a single methylation in one of the aptamers, preventing aggregation due to the inability of α-thrombin to recognize it. A parallel study with gold and ferromagnetic NPs is detailed, concluding that the Au coating of FexOy NP does not affect their performance and that they are suitable as complex biosensors. These results prove the high detection potency of Au-coated SPIONs for biomedical applications especially for DNA repair detection. PMID:26593913

Protein Corona Influences Cellular Uptake of Gold Nanoparticles by Phagocytic and Nonphagocytic Cells in a Size-Dependent Manner.

PubMed

Cheng, Xiaju; Tian, Xin; Wu, Anqing; Li, Jianxiang; Tian, Jian; Chong, Yu; Chai, Zhifang; Zhao, Yuliang; Chen, Chunying; Ge, Cuicui

2015-09-23

The interaction at nanobio is a critical issue in designing safe nanomaterials for biomedical applications. Recent studies have reported that it is nanoparticle-protein corona rather than bare nanoparticle that determines the nanoparticle-cell interactions, including endocytic pathway and biological responses. Here, we demonstrate the effects of protein corona on cellular uptake of different sized gold nanoparticles in different cell lines. The experimental results show that protein corona significantly decreases the internalization of Au NPs in a particle size- and cell type-dependent manner. Protein corona exhibits much more significant inhibition on the uptake of large-sized Au NPs by phagocytic cell than that of small-sized Au NPs by nonphagocytic cell. The endocytosis experiment indicates that different endocytic pathways might be responsible for the differential roles of protein corona in the interaction of different sized Au NPs with different cell lines. Our findings can provide useful information for rational design of nanomaterials in biomedical application.

Adenosine Triphosphate-Encapsulated Liposomes with Plasmonic Nanoparticles for Surface Enhanced Raman Scattering-Based Immunoassays.

PubMed

Pham, Xuan-Hung; Hahm, Eunil; Kim, Tae Han; Kim, Hyung-Mo; Lee, Sang Hun; Lee, Yoon-Sik; Jeong, Dae Hong; Jun, Bong-Hyun

2017-06-23

In this study, we prepared adenosine triphosphate (ATP) encapsulated liposomes, and assessed their applicability for the surface enhanced Raman scattering (SERS)-based assays with gold-silver alloy (Au@Ag)-assembled silica nanoparticles (NPs; SiO₂@Au@Ag). The liposomes were prepared by the thin film hydration method from a mixture of l-α-phosphatidylcholine, cholesterol, and PE-PEG2000 in chloroform; evaporating the solvent, followed by hydration of the resulting thin film with ATP in phosphate-buffered saline (PBS). Upon lysis of the liposome, the SERS intensity of the SiO₂@Au@Ag NPs increased with the logarithm of number of ATP-encapsulated liposomes after lysis in the range of 8 × 10⁶ to 8 × 10 10 . The detection limit of liposome was calculated to be 1.3 × 10 -17 mol. The successful application of ATP-encapsulated liposomes to SiO₂@Au@Ag NPs based SERS analysis has opened a new avenue for Raman label chemical (RCL)-encapsulated liposome-enhanced SERS-based immunoassays.

Recognition-mediated activation of therapeutic gold nanoparticles inside living cells

NASA Astrophysics Data System (ADS)

Kim, Chaekyu; Agasti, Sarit S.; Zhu, Zhengjiang; Isaacs, Lyle; Rotello, Vincent M.

2010-11-01

Supramolecular chemistry provides a versatile tool for the organization of molecular systems into functional structures and the actuation of these assemblies for applications through the reversible association between complementary components. Use of this methodology in living systems, however, represents a significant challenge owing to the chemical complexity of cellular environments and lack of selectivity of conventional supramolecular interactions. Herein, we present a host-guest system featuring diaminohexane-terminated gold nanoparticles (AuNP-NH2) and complementary cucurbit[7]uril (CB[7]). In this system, threading of CB[7] on the particle surface reduces the cytotoxicity of AuNP-NH2 through sequestration of the particle in endosomes. Intracellular triggering of the therapeutic effect of AuNP-NH2 was then achieved through the administration of 1-adamantylamine (ADA), removing CB[7] from the nanoparticle surface, causing the endosomal release and concomitant in situ cytotoxicity of AuNP-NH2. This supramolecular strategy for intracellular activation provides a new tool for potential therapeutic applications.

Electrochemical Sensing toward Trace As(III) Based on Mesoporous MnFe₂O₄/Au Hybrid Nanospheres Modified Glass Carbon Electrode.

PubMed

Zhou, Shaofeng; Han, Xiaojuan; Fan, Honglei; Liu, Yaqing

2016-06-22

Au nanoparticles decorated mesoporous MnFe₂O₄ nanocrystal clusters (MnFe₂O₄/Au hybrid nanospheres) were used for the electrochemical sensing of As(III) by square wave anodic stripping voltammetry (SWASV). Modified on a cheap glass carbon electrode, these MnFe₂O₄/Au hybrid nanospheres show favorable sensitivity (0.315 μA/ppb) and limit of detection (LOD) (3.37 ppb) toward As(III) under the optimized conditions in 0.1 M NaAc-HAc (pH 5.0) by depositing for 150 s at the deposition potential of -0.9 V. No obvious interference from Cd(II) and Hg(II) was recognized during the detection of As(III). Additionally, the developed electrode displayed good reproducibility, stability, and repeatability, and offered potential practical applicability for electrochemical detection of As(III) in real water samples. The present work provides a potential method for the design of new and cheap sensors in the application of electrochemical determination toward trace As(III) and other toxic metal ions.

Inorganic colloidal nanocrystals: Synthesis and bioapplications

NASA Astrophysics Data System (ADS)

Wu, Huimeng

Nanocrystals (NCs) are very small particles, which contain from a few hundred to thousands of atoms depending on the size of NCs. Because of their special properties compared with the bulk materials, NCs have found many promising applications in areas, such as biomedical diagnosis, catalysis, plasmonics, high-density data storage and solar energy conversion. This dissertation presents studies on the syntheses of metal oxide NCs and hybrid NCs, the surface functionalization of NCs by dual-interaction ligands, and gold-NC-based assay for the detection of beta-galactosidase. Monodisperse colloidal uranium dioxide NCs (UO2 NCs) were synthesized by decomposition of uranyl acetylacetonate. By changing the amount of added surfactant, the sizes of the NCs could vary from 2 ˜ 8 nm. Mechanistic studies of the formation of UO2 NCs showed that the condensation product (amide) of oleic acid and oleylamine plays an important role in controlling the particle size. Normally, high-quality NCs are synthesized in organic phase, but most of NC-based bio-applications require water-soluble NCs. To convert these hydrophobic NCs to hydrophilic particles, surface modification is employed. Here dual interaction ligands based on the Tween-derivatives (TDs) were synthesized. Stability tests on TD-capped NCs showed that these dual interaction ligands can significantly increase the stability of NCs compared to single interaction ligands. Further, These TD-capped QDs were further tested as fluorescent labels to detect virusprotein expression in cells. To exploit bio-applications of nanocrystals, gold nanocrystal-based assay to detect enzyme activity was designed. The optical properties of Au-NCs are not only dependent on the particle sizes and shapes, but also the distances between the particles. Here, Lipoic acid-tyramine-beta-galactopyranosyl (LTbeta-gal) was synthesized, as ligands, to cap Au-NCs; and the resultant LTbeta-gal-capped Au-NCs could disperse in water. After the hydrolysis of the ligands with beta-galactosidase, these Au-NCs become to aggregate, which exhibit a red-shift in the absorption spectrum of the Au-NC suspension. The detection of beta-galactosidase was further studies by varying the amounts of beta-galactosidase. Hybrid nanocrystals (HNCs) are attractive candidates for advanced nanomaterials because they contain two or more different nanoscale functionalities, which are expected to possess novel physical and chemical properties. Two kinds of heterodimers (FePt/In2O3 and UO2/In 2O3) were prepared using a similar procedure and the synthesized HNCs exhibited different shapes. The studies of high-resolution transmission electron microscopy (HRTEM) indicate that the shapes of these two dimers were controlled by the interfacial structures. The amorphous iron oxide layers on the FePt NC surfaces act as glue to interconnect the FePt with the indium oxide parts and led to a core-seed-shaped heterodimer. Using completely crystalline UO2 NCs as seeds resulted in a peanut-shapd HNC.

Advances in Gold Catalysis and Understanding the Catalytic Mechanism.

PubMed

Ishida, Tamao; Koga, Hiroaki; Okumura, Mitsutaka; Haruta, Masatake

2016-10-01

When gold is deposited as nanoparticles (NPs) with mean diameters of 2-5 nm or clusters with mean diameters below 2 nm onto a variety of supports such as metal oxides, carbons, polymers, etc., the supported Au NPs exhibit unique catalytic properties, while bulk Au is almost inert as a catalyst. A lot of research works indicate that the key factors of the catalysis by supported Au NPs are the selection of the supports, the control of the Au NP size, the shape of the Au NPs, and the strong junction between Au NPs and the supports, because the perimeter zone around Au NPs acts as the active site for many reactions. In order to elucidate the origin of catalysis by supported Au NPs, the interplay between physicochemical analysis, computational studies, and rational experiments for catalysis by supported Au NPs is becoming more and more important. This article summarizes our experiences and progress in such interplay. © 2016 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Green synthesis of size controllable gold nanoparticles

NASA Astrophysics Data System (ADS)

Mohan Kumar, Kesarla; Mandal, Badal Kumar; Kiran Kumar, Hoskote A.; Maddinedi, Sireesh Babu

2013-12-01

A facile rapid green eco-friendly method to synthesize gold nanoparticles (Au NPs) of tunable size using aqueous Terminalia arjuna fruit extracts has been demonstrated herein. Formation of Au NPs was confirmed by Surface Plasmon Resonance (SPR) study at 528 nm using UV-visible spectrophotometer. The time of reduction, size and morphological variations of Au NPs were studied with varying quantities of T. arjuna fruit aqueous extracts. Synthesized Au NPs were characterized using UV-visible spectroscopy, Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Energy dispersive X-ray spectroscopy (EDAX). Polyphenols responsible for reduction of Au3+ to Au0 were identified using High Performance Liquid Chromatography (HPLC) as ascorbic acid, gallic acid and pyrogallol. The oxidized forms of polyphenols formed coordination with surface of Au NPs which protected their further growth and aggregation. We also propose a plausible mechanism how to tune size and shape of Au NPs by varying the quantity of extracts. Thus obtained Au NPs were stable for more than four months.

Shape-engineering substrate-based plasmonic nanomaterials

NASA Astrophysics Data System (ADS)

Gilroy, Kyle D.

The advancement of next generation technologies is reliant on our ability to engineer matter at the nanoscale. Since the morphological features of nanomaterials dictate their chemical and physical properties, a significant effort has been put forth to develop syntheses aimed at fine tuning their size, shape and composition. This massive effort has resulted in a maturing colloidal chemistry containing an extensive collection of morphologies with compositions nearly spanning the entire transition of the periodic table. While colloidal nanoparticles have opened the door to promising applications in fields such as cancer theranostics, drug delivery, catalysis and sensing; the synthetic protocols for the placement of nanomaterials on surfaces, a requisite for chip-based devices, are ill-developed. This dissertation serves to address this limitation by highlighting a series of syntheses related to the design of substrate-based nanoparticles whose size, shape and composition are controllably engineered to a desired endpoint. The experimental methods are based on a template-mediated approach which sees chemical modifications made to prepositioned thermally assembled metal nanostructures which are well bonded to a sapphire substrate. The first series of investigations will highlight synthetic routes utilizing galvanic replacement reactions, where the prepositioned templates are chemically transformed into hollow nanoshells. Detailed studies are provided highlighting discoveries related to (i) hollowing, (ii) defect transfer, (iii) strain induction, (iv) interdiffusion, (v) crystal structure and (vi) the localized surface plasmon resonance (LSPR). The second series of investigations, based on heterogeneous nucleation, have Au templates serve as nucleation sites for metal atoms arriving in either the solution- or vapor phase. The solution-phase heterogeneous nucleation of Ag on Au reveals that chemical kinetics (injection rate & precursor concentration) can be used to control the nature of how Ag atoms grow on the Au template. It was discovered that (i) slow kinetics leads to an anisotropic growth mode (heterodimeric structures), (ii) fast kinetics causes a very uniform deposition (Au-Ag coreshell morphology, or Au Ag) and (iii) medium kinetics produces structures with an intermediate morphology (truncated octahedron). In the second case, where the nucleation event is carried out at high temperatures, the Ag vapor is sourced from a sublimating foil onto adjacent Au templates. This process drives the composition and morphology from a Au Wulff-shape to a homogeneous Au-Ag nanoprism. By tracking over time the (i) morphological features, (ii) LSPR and (iii) composition; insights into the fundamental atomic scale growth mechanisms are elucidated. Overall, substrate-based template-mediated syntheses have proven to be an effective route for directing growth pathways toward a desired endpoint giving rise to an impressive new group of complex substrate-based nanostructures with asymmetric, core-shell and hollowed morphologies. While this dissertation is focused heavily on the development of synthetic procedures aimed at generating substrate-based plasmonic nanomaterials, the last chapter will serve to highlight a series of on-going studies aimed at defining these nanomaterials as highly effective heterogeneous catalysts. Several examples are shown including (i) nanoparticle films synthesize via sputter deposition, (ii) mechanically induced nanotexturing of bulk copper foils, (iii) ultra-small AuPd nanoparticles synthesized via pulse laser, (iv) substrate-based AuCu nanoprisms and (v) the Wulff in a Cage Morphology.

Analyses of protein corona on bare and silica-coated gold nanorods against four mammalian cells.

PubMed

Das, Minakshi; Yi, Dong Kee; An, Seong Soo A

2015-01-01

The purpose of this study was to investigate the mechanisms responsible for the toxic effects of gold nanorods (AuNRs). Here, a comprehensive study was performed by examining the effects of bare (uncoated) AuNRs and AuNRs functionalized with silica (SiO2-AuNRs) against various mammalian cell lines, including cervical cancer cells, fibroblast cells, human umbilical vein endothelial cells, and neuroblastoma cells. The interactions between AuNRs and mammalian cells were investigated with cell viability and mortality assays. Dihydrorhodamine-123 assay was carried out for evaluating reactive oxygen species (ROS) generation, along with mass spectroscopy analysis for determining the composition of the protein corona. Our results suggest that even the lowest concentrations of AuNRs (0.7 μg/mL) induced ROS production leading to cell mortality. On the other hand, cellular viability and ROS production were maintained even at a higher concentration of SiO2-coated AuNRs (12 μg/mL). The increased production of ROS by AuNRs seemed to cause the toxicity observed in all four mammalian cell types. The protein corona on the bare AuNRs did not appear to reduce ROS generation; however, different compositions of the protein corona on bare and SiO2-coated AuNRs may affect cellular behavior differently. Therefore, it was determined that SiO2-coated AuNRs would be more advantageous than bare AuNRs for cellular applications.

Synergistic Use of Gold Nanoparticles (AuNPs) and “Capillary Enzyme-Linked Immunosorbent Assay (ELISA)” for High Sensitivity and Fast Assays

PubMed Central

Kim, Wan-Joong; Cho, Hyo Young; Jeong, Bongjin; Byun, Sangwon; Huh, JaeDoo; Kim, Young Jun

2017-01-01

Using gold nanoparticles (AuNPs) on “capillary enzyme-linked immunosorbent assay (ELISA)”, we produced highly sensitive and rapid assays, which are the major attributes for point-of-care applications. First, in order to understand the size effect of AuNPs, AuNPs of varying diameters (5 nm, 10 nm, 15 nm, 20 nm, 30 nm, and 50 nm) conjugated with Horseradish Peroxidase (HRP)-labeled anti-C reactive protein (antiCRP) (AuNP•antiCRP-HRP) were used for well-plate ELISA. AuNP of 10 nm produced the largest optical density, enabling detection of 0.1 ng/mL of CRP with only 30 s of incubation, in contrast to 10 ng/mL for the ELISA run in the absence of AuNP. Then, AuNP of 10 nm conjugated with antiCRP-HRP (AuNP•antiCRP-HRP) was used for “capillary ELISA” to detect as low as 0.1 ng/mL of CRP. Also, kinetic study on both 96-well plates and in a capillary tube using antiCRP-HRP or AuNP•antiCRP-HRP showed a synergistic effect between AuNP and the capillary system, in which the fastest assay was observed from the “AuNP capillary ELISA”, with its maximum absorbance reaching 2.5 min, while the slowest was the typical well-plate ELISA with its maximum absorbance reaching in 13.5 min. PMID:29278402

Enhanced middle-infrared light transmission through Au/SiO(x)N(y)/Au aperture arrays.

PubMed

Xiao, Gongli; Yao, Xiang; Ji, Xinming; Zhou, Jia; Bao, Zongming; Huang, Yiping

2011-12-01

The enhanced middle-infrared light transmission through Au/SiO(x)N(y)/Au aperture arrays by changing the refractive index and the thickness of a dielectric layer was studied experimentally. The results indicated that the transmission spectra was highly dependent on the refractive index and the thickness of SiO(x)N(y). We found that the transmission peaks redshifted regularly along with the refractive index from 1.6 to 1.8, owing to the role of surface plasmon polaritons (SPP) coupling in the Au/SiO(x)N(y)/Au cascaded metallic structure. Simultaneously, a higher transmission efficiency and narrower transmission peak was obtained in Au/SiO2.1N0.3/Au cascaded metallic structure with small refractive index (1.6) than in Au/SiO0.6N1/Au cascaded metallic structure with large refractive index (1.8). When the thickness of SiO(x)N(y) changes from 0.2 to 0.4 microm, the shape of transmission spectra exhibits a large change. It was found that a higher transmission efficiency and narrower transmission peak was obtained in Au/SiO(x)N(y)/Au cascaded metallic structure with a thin dielectric film (0.2 microm), with the increase of SiO(x)N(y) film's thickness, the transmission peak gradually widened and disappeared finally. This effect is useful in applications of biochemical sensing and tunable integrated plasmonic devices in the middle-infrared region.

Gold Nanoparticle-Quantum Dot Fluorescent Nanohybrid: Application for Localized Surface Plasmon Resonance-induced Molecular Beacon Ultrasensitive DNA Detection

NASA Astrophysics Data System (ADS)

Adegoke, Oluwasesan; Park, Enoch Y.

2016-11-01

In biosensor design, localized surface plasmon resonance (LSPR)-induced signal from gold nanoparticle (AuNP)-conjugated reporter can produce highly sensitive nanohybrid systems. In order to retain the physicochemical properties of AuNPs upon conjugation, high colloidal stability in aqueous solution is needed. In this work, the colloidal stability with respect to the zeta potential (ZP) of four negatively charged thiol-functionalized AuNPs, thioglycolic (TGA)-AuNPs, 3-mercaptopropionic acid (MPA)-AuNPs, l-cysteine-AuNPs and l-glutathione (GSH)-AuNPs, and a cationic cyteamine-capped AuNPs was studied at various pHs, ionic strength, and NP concentration. A strong dependence of the ZP charge on the nanoparticle (NP) concentration was observed. High colloidal stability was exhibited between pH 3 and 9 for the negatively charged AuNPs and between pH 3 and 7 for the cationic AuNPs. With respect to the ionic strength, high colloidal stability was exhibited at ≤104 μM for TGA-AuNPs, l-cysteine-AuNPs, and GSH-AuNPs, whereas ≤103 μM is recommended for MPA-AuNPs. For the cationic AuNPs, very low ionic strength of ≤10 μM is recommended due to deprotonation at higher concentration. GSH-AuNPs were thereafter bonded to SiO2-functionalized alloyed CdZnSeS/ZnSe1.0S1.3 quantum dots (SiO2-Qdots) to form a plasmon-enhanced AuNP-SiO2-Qdots fluorescent nanohybrid. The AuNP-SiO2-Qdots conjugate was afterward conjugated to a molecular beacon (MB), thus forming an ultrasensitive LSPR-induced SiO2-Qdots-MB biosensor probe that detected a perfect nucleotide DNA sequence at a concentration as low as 10 fg/mL. The limit of detection was 11 fg/mL (1.4 fM) while the biosensor probe efficiently distinguished between single-base mismatch and noncomplementary sequence target.

Fluidic Manufacture of Star-Shaped Gold Nanoparticles.

PubMed

Silvestri, Alessandro; Lay, Luigi; Psaro, Rinaldo; Polito, Laura; Evangelisti, Claudio

2017-07-21

Star-shaped gold nanoparticles (StarAuNPs) are extremely attractive nanomaterials, characterized by localized surface plasmon resonance which could be potentially employed in a large number of applications. However, the lack of a reliable and reproducible synthetic protocols for the production of StarAuNPs is the major limitation to their spreading. For the first time, here we present a robust protocol to manufacture reproducible StarAuNPs by exploiting a fluidic approach. Star-shaped AuNPs have been synthesized by means of a seed-less protocol, employing ascorbic acid as reducing agent at room temperature. Moreover, the versatility of the bench-top microfluidic protocol has been exploited to afford hydrophilic, hydrophobic and solid-supported engineered StarAuNPs, by avoiding intermediate NP purifications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrafast strong broadband light source generated in nanoscale plasmonic Au-AAO-Al structures

NASA Astrophysics Data System (ADS)

Han, Junbo; Yao, Linhua; Ma, Zongwei

we demonstrate an ultrafast strong broadband photoluminescence (PL) from Au-AAO-Al composite under low excitation power intensity of 3.8 34.5 GW /cm2. The emission wavelength is in the range of 450-1050 nm and the lifetime is under sub-nanosecond. Comparative studies of PL in Au-AAO-Al with different Au rod length and Au-AAO without Al coupling layer, together with the finite difference time domain (FDTD) calculations, present that the fast PL originates from the surface plasmon enhanced supercontinuum generation (SCG) in AAO membrane. The observations indicate that strong SCG could be realized in nanoscale plasmonic structures, which have promise applications in the minimization and integration of ultrafast lighting sources in photonic devices. National Natural Scientific Foundation of China (11404124).

Design and development of a field applicable gold nanosensor for the detection of luteinizing hormone.

PubMed

Zambre, Ajit; Chanda, Nripen; Prayaga, Sudhirdas; Almudhafar, Rosana; Afrasiabi, Zahra; Upendran, Anandhi; Kannan, Raghuraman

2012-11-06

In this paper, we describe a novel strategy for the fabrication of a nanosensor for detecting luteinizing hormone (LH) of sheep using a gold nanoparticle-peptide conjugate. A new peptide sequence "CDHPPLPDILFL" (leutinizing hormone peptide, LHP) has been identified, using BLAST and Clustal W analysis, to detect antibody of LH (sheep). LHP has been synthesized and characterized, and their affinity toward anti-LH was established using enzyme linked immunosorbant assay (ELISA) technique. The thiol group in LHP directly binds with gold nanoparticles (AuNPs) to yield AuNP-LHP construct. Detailed physicochemical analysis of AuNP-LHP construct was determined using various analytical techniques. Nanosensor using gold nanoparticle peptide conjugate was developed on the basis of competitive binding of AuNP-LHP and LH toward anti-LH. Nitrocellulose membrane, precoated with anti-LH, was soaked in the mixture of AuNP-LHP and sample of analysis (LH). In the absence of LH (sheep), anti-LH coated on the membrane binds with AuNP-LHP, leading to a distinctive red color, while in the presence of LH, no color appeared in the membrane due to the interaction of anti-LH with LH thereby preventing the binding of AuNP-LHP with membrane bound anti-LH. The sensor assay developed in this study can detect LH (sheep) up to a minimal concentration of ∼50 ppm with a high degree of reproducibility and selectivity. The gold-nanoparticle-peptide based nanosensor would be a simple, portable, effective, and low cost technique for infield applications.

Gold nanoparticle enhancement of stereotactic radiosurgery for neovascular age-related macular degeneration

NASA Astrophysics Data System (ADS)

Ngwa, Wilfred; Makrigiorgos, G. Mike; Berbeco, Ross I.

2012-10-01

Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries for people over the age of 50. In this work, the dosimetric feasibility of using gold nanoparticles (AuNP) as radiosensitizers to enhance kilovoltage stereotactic radiosurgery for neovascular AMD is investigated. Microdosimetry calculations at the sub-cellular level were carried out to estimate the radiation dose enhancement to individual nuclei in neovascular AMD endothelial cells (nDEF) due to photon-induced photo-/Auger electrons from x-ray-irradiated AuNP. The nDEF represents the ratio of radiation doses to the endothelial cell nuclei with and without AuNP. The calculations were carried out for a range of feasible AuNP local concentrations using the clinically applicable 100 kVp x-ray beam parameters employed by a commercially available x-ray therapy system. The results revealed nDEF values of 1.30-3.26 for the investigated concentration range of 1-7 mg g-1, respectively. In comparison, for the same concentration range, nDEF values of 1.32-3.40, 1.31-3.33, 1.29-3.19, 1.28-3.12 were calculated for 80, 90, 110 and 120 kVp x-rays, respectively. Meanwhile, calculations as a function of distance from the AuNP showed that the dose enhancement, for 100 kVp, is markedly confined to the targeted neovascular AMD endothelial cells where AuNP are localized. These findings provide impetus for considering the application of AuNP to enhance therapeutic efficacy during stereotactic radiosurgery for neovascular AMD.

Femtosecond laser generated gold nanoparticles and their plasmonic properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Rupali, E-mail: phz148121@iitd.ac.in; Navas, M. P.; Soni, R. K.

The pulsed laser ablation in liquid medium is now commonly used to generate stable colloidal nanoparticles (NPs) in absence of any chemical additives or stabilizer with diverse applications. In this paper, we report generation of gold NPs (Au NPs) by ultra-short laser pulses. Femtosecond (fs) laser radiation (λ = 800 nm) has been used to ablate a gold target in pure de-ionized water to produce gold colloids with smallsize distribution. The average size of the particles can be further controlled by subjecting to laser-induced post-irradiation providing a versatile physical method of size-selected gold nanoparticles. The optical extinction and morphological dimensions weremore » investigated with UV-Vis spectroscopy and Transmission Electron Microscopy measurements, respectively. Finite difference time domain (FDTD) method is employed to calculate localized surface plasmon (LSPR) wavelength and the near-field generated by Au NPs and their hybrids.« less

Photocatalytically Renewable Micro-electrochemical Sensor for Real-Time Monitoring of Cells.

PubMed

Xu, Jia-Quan; Liu, Yan-Ling; Wang, Qian; Duo, Huan-Huan; Zhang, Xin-Wei; Li, Yu-Tao; Huang, Wei-Hua

2015-11-23

Electrode fouling and passivation is a substantial and inevitable limitation in electrochemical biosensing, and it is a great challenge to efficiently remove the contaminant without changing the surface structure and electrochemical performance. Herein, we propose a versatile and efficient strategy based on photocatalytic cleaning to construct renewable electrochemical sensors for cell analysis. This kind of sensor was fabricated by controllable assembly of reduced graphene oxide (RGO) and TiO2 to form a sandwiching RGO@TiO2 structure, followed by deposition of Au nanoparticles (NPs) onto the RGO shell. The Au NPs-RGO composite shell provides high electrochemical performance. Meanwhile, the encapsulated TiO2 ensures an excellent photocatalytic cleaning property. Application of this renewable microsensor for detection of nitric oxide (NO) release from cells demonstrates the great potential of this strategy in electrode regeneration and biosensing. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A microRNA-initiated DNAzyme motor operating in living cells

NASA Astrophysics Data System (ADS)

Peng, Hanyong; Li, Xing-Fang; Zhang, Hongquan; Le, X. Chris

2017-03-01

Synthetic DNA motors have great potential to mimic natural protein motors in cells but the operation of synthetic DNA motors in living cells remains challenging and has not been demonstrated. Here we report a DNAzyme motor that operates in living cells in response to a specific intracellular target. The whole motor system is constructed on a 20 nm gold nanoparticle (AuNP) decorated with hundreds of substrate strands serving as DNA tracks and dozens of DNAzyme molecules each silenced by a locking strand. Intracellular interaction of a target molecule with the motor system initiates the autonomous walking of the motor on the AuNP. An example DNAzyme motor responsive to a specific microRNA enables amplified detection of the specific microRNA in individual cancer cells. Activated by specific intracellular targets, these self-powered DNAzyme motors will have diverse applications in the control and modulation of biological functions.

Self-Assembly of Nanoclusters into Mono-, Few-, and Multilayered Sheets via Dipole-Induced Asymmetric van der Waals Attraction.

PubMed

Wu, Zhennan; Liu, Jiale; Li, Yanchun; Cheng, Ziyi; Li, Tingting; Zhang, Hao; Lu, Zhongyuan; Yang, Bai

2015-06-23

Two-dimensional (2D) nanomaterials possessing regular layered structures and versatile chemical composition are highly expected in many applications. Despite the importance of van der Waals (vdW) attraction in constructing and maintaining layered structures, the origin of 2D anisotropy is not fully understood, yet. Here, we report the 2D self-assembly of ligand-capped Au15 nanoclusters into mono-, few-, and multilayered sheets in colloidal solution. Both the experimental results and computer simulation reveal that the 2D self-assembly is initiated by 1D dipolar attraction common in nanometer-sized objects. The dense 1D attachment of Au15 leads to a redistribution of the surface ligands, thus generating asymmetric vdW attraction. The deliberate control of the coordination of dipolar and vdW attraction further allows to manipulate the thickness and morphologies of 2D self-assembly architectures.

Micropatterned stretchable circuit and strain sensor fabricated by lithography on an electrospun nanofiber mat.

PubMed

Park, Minwoo; Im, Jungkyun; Park, Jongjin; Jeong, Unyong

2013-09-11

This paper describes a novel approach for composite nanofiber mats and its application to fabricate a strain sensor. Electrospun poly(4-vinylpyridine) (P4VP) nanofiber mats are micropatterned by a lithographic approach that includes selective oxidation of the nanofibers and removal of unreacted fibers. The P4VP/HAuCl4 complex is converted to P4VP/Au composites by chemical reduction. We investigate the electrical resistivity of the composite mats according to the number of complexation-and-reduction cycles, the thickness of the fiber mats, and the annealing temperatures which control the percolation of the Au nanoparticles in the fiber mats. Nozzle printing of a polymeric solution on the patterned nanofiber mats simply produces an array of strain-sensitive and strain-invariant units. The patterns demonstrate high strain-sensing performance without any mechanical and electrical failure over 200 bending cycles in the strain range of ε<0.17.

Impedance Biosensing to detect food allergens, endocrine disrupting chemicals, and food pathogens

NASA Astrophysics Data System (ADS)

Radhakrishnan, Rajeswaran

Electrochemical impedance biosensors can be viewed as an AC electroanalytical method for the analyte detection in the fields of biomedicine, environmental monitoring, and food and agriculture, amongst others. The most common format for AC impedance biosensing involves surface immobilization of an antibody, receptor protein, DNA strand, or other species capable of bio-recognition, and AC impedance detection of the binding event. Technological application of AC impedance biosensors has been hindered by several obstacles, including the more complex circuitry required for AC relative to DC electrochemistry, chemical and physical interference arising from non-specific adsorption, and the stability and reproducibility of protein immobilization. One focus of these PhD studies is on methods to reduce or compensate for non-specific adsorption, including sample dilution, site blocking with BSA, and the use of control electrodes onto which reference antibodies are immobilized. Examples that will be presented include impedance detection of food pathogens, such as Listeria monocytogenes, using a mouse monoclonal antibody immobilized onto an Au electrode. This yields detection limits of 5 CFU/ml and 4 CFU/ml for ideal solutions and filtered tomato extract, respectively. Control experiments with an Au electrode onto which a mouse monoclonal antibody to GAPDH is immobilized demonstrate that non-specific adsorption is insignificant for the system and methodology studied here. Control experiments with Salmonella enterica demonstrate no cross-reactivity to this food pathogen. In addition, Detection of two endocrine-disrupting chemicals (EDC), norfluoxetine and BDE-47, is reported here by impedance biosensing, with a detection limit of 8.5 and 1.3 ng/ml for norfluoxetine and BDE-47, respectively. Additional research has focused on alternative substrates and linker chemistries for protein immobilization, including the use of degenerate (highly doped) Si and bidendate thiol monolayer onto Au. Advantages of degenerate Si include a simpler equivalent circuit, simple and reproducible surface preparation, easy incorporation into ULSI devices, and the greater strength of Si-C bonds (~520 kJ/mole) relative to Au-S bonds (125-150 kJ/mole). New results demonstrating antibody regeneration atop degenerate (highly doped) Si are also reported. Using 0.2 M KSCN and 10 mM HF for antibody regeneration, peanut protein Ara h 1 is detected daily during a thirty-day trial. An impedance biosensor is reported that employs the bidentate thiol 16-[3,5-bis(mercaptomethyl)phenoxy]-hexadecanoic acid (BMPHA) to immobilize the mouse monoclonal antibody to peanut protein Ara h 1. The detection limit for Ara h 1 is approximately 0.71 ng/mL (0.01 nM), which is about one order of magnitude lower than that obtained for antibody immobilization atop the monodendate thiol, 16-mercaptohexadecanoic acid (16 MHA). Antibody regeneration was studied daily using a gentle denaturing agent, 0.2 M KSCN at pH 7.3. The antibody-coated on Au electrodes retained activity towards Ara h1 for 10 and 20 days of regeneration of the monodendate- and BMPHA-coated Au electrodes, respectively. This prolonged activity illustrates the superior stability of protein films atop the BMPHA bidentate thiol- coated Au electrode relative to the 16-MHA monodendate thiol-coated Au electrode.