On the application potential of gold nanoparticles in nanoelectronics and biomedicine.

PubMed

Homberger, Melanie; Simon, Ulrich

2010-03-28

Ligand-stabilized gold nanoparticles (AuNPs) are of high interest to research dedicated to future technologies such as nanoelectronics or biomedical applications. This research interest arises from the unique size-dependent properties such as surface plasmon resonance or Coulomb charging effects. It is shown here how the unique properties of individual AuNPs and AuNP assemblies can be used to create new functional materials for applications in a technical or biological environment. While the term technical environment focuses on the potential use of AuNPs as subunits in nanoelectronic devices, the term biological environment addresses issues of toxicity and novel concepts of controlling biomolecular reactions on the surface of AuNPs.

Preparation, Modification, Characterization, and Biosensing Application of Nanoporous Gold Using Electrochemical Techniques

PubMed Central

Neupane, Dharmendra; Nepal, Bishal; Mikhaylov, Vasilii; Stine, Keith J.

2018-01-01

Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning pore and ligament sizes. The np-Au electrodes that are prepared using electrochemical techniques are robust and are easier to handle for their use in electrochemical biosensing. Here, we review different electrochemical strategies for the preparation, post-modification, and characterization of np-Au along with the synergistic use of both electrochemistry and np-Au for applications in biosensing. PMID:29547580

Preparation, Modification, Characterization, and Biosensing Application of Nanoporous Gold Using Electrochemical Techniques.

PubMed

Bhattarai, Jay K; Neupane, Dharmendra; Nepal, Bishal; Mikhaylov, Vasilii; Demchenko, Alexei V; Stine, Keith J

2018-03-16

Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning pore and ligament sizes. The np-Au electrodes that are prepared using electrochemical techniques are robust and are easier to handle for their use in electrochemical biosensing. Here, we review different electrochemical strategies for the preparation, post-modification, and characterization of np-Au along with the synergistic use of both electrochemistry and np-Au for applications in biosensing.

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.

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

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.

Multifunctional compact hybrid Au nanoshells: a new generation of nanoplasmonic probes for biosensing, imaging, and controlled release.

PubMed

Jin, Yongdong

2014-01-21

Gold nanoshells (AuNSs) with tunable localized surface plasmon resonance (LSPR) peaks in the near-infrared (NIR) region possess unique optical properties-particularly that soft tissues are "transparent" at these wavelengths-making them of great interest in cancer diagnosis and treatment. Since 1998 when Halas and co-workers invented the first generation of AuNS, with a silica core and Au shell, researchers have studied and designed AuNSs for theranostic-individualized, combination diagnosis and therapy-nanomedicine. As demand has increased for more powerful and practical theranostic applications, so has demand for the next generation of AuNSs-compact yet complex multifunctional AuNSs with finely integrated plasmonic and nonplasmonic inorganic components. For in vivo biomedical applications, such a hybrid AuNS offers the desirable optical properties of NIR LSPR. Size, however, has proved a more challenging parameter to control in hybrid AuNSs. The ideal size of therapeutic NPs is 10-100 nm. Larger particles have limited diffusion in the extracellular space, while particles less than 5 nm are rapidly cleared from the circulation through extravasation or renal clearance. Conventional methods of preparing AuNS have failed to obtain small-sized hybrid AuNSs with NIR LSPR responses. In this Account, we present a new class of multifunctional hybrid AuNSs with ultrathin AuNSs and varied, functional (nonplasmonic) core components ranging from "hard" semiconductor quantum dots (QDs), to superparamagnetic NPs, to "soft" liposomes made using poly-l-histidine as a template to direct Au deposition. The resultant hybrid AuNSs are uniform and compact (typically 15-60 nm) but also preserve the optical properties and shell-type NIR response necessary for biomedical use. We also demonstrate these particles' innovative plasmonic applications in biosensing, multimodal imaging and controlled release. More importantly, the magnetic-plasmonic Fe3O4/Au core-shell NP enables a new biological imaging method-magnetomotive photoacoustic (mmPA) imaging, which suppresses the nonmagnetomotive background and therefore offers remarkable contrast enhancement and improved specificity compared with photoacoustic images using conventional NP contrast agents. The advantages of our AuNSs are obvious: they are monodisperse, small (<100 nm), highly integrated, and have tunable visible-NIR plasmonic responses. All of these properties are crucial for in vitro or in vivo biological/biomedical studies and many applications, especially for studies of single cells or molecules which require particle monodispersity and tight size control. The plasmonic fluorescent QD/Au and the magnetic plasmonic Fe3O4/Au core-shell NPs may also reveal new physical phenomena that may lead to useful applications, owing to their well-defined core-shell nanoarchitectures and underlying nanoscale physical interactions.

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

Ligand-protected gold clusters: the structure, synthesis and applications

NASA Astrophysics Data System (ADS)

Pichugina, D. A.; Kuz'menko, N. E.; Shestakov, A. F.

2015-11-01

Modern concepts of the structure and properties of atomic gold clusters protected by thiolate, selenolate, phosphine and phenylacetylene ligands are analyzed. Within the framework of the superatom theory, the 'divide and protect' approach and the structure rule, the stability and composition of a cluster are determined by the structure of the cluster core, the type of ligands and the total number of valence electrons. Methods of selective synthesis of gold clusters in solution and on the surface of inorganic composites based, in particular, on the reaction of Aun with RS, RSe, PhC≡C, Hal ligands or functional groups of proteins, on stabilization of clusters in cavities of the α-, β and γ-cyclodextrin molecules (Au15 and Au25) and on anchorage to a support surface (Au25/SiO2, Au20/C, Au10/FeOx) are reviewed. Problems in this field are also discussed. Among the methods for cluster structure prediction, particular attention is given to the theoretical approaches based on the density functional theory (DFT). The structures of a number of synthesized clusters are described using the results obtained by X-ray diffraction analysis and DFT calculations. A possible mechanism of formation of the SR(AuSR)n 'staple' units in the cluster shell is proposed. The structure and properties of bimetallic clusters MxAunLm (M=Pd, Pt, Ag, Cu) are discussed. The Pd or Pt atom is located at the centre of the cluster, whereas Ag and Cu atoms form bimetallic compounds in which the heteroatom is located on the surface of the cluster core or in the 'staple' units. The optical properties, fluorescence and luminescence of ligand-protected gold clusters originate from the quantum effects of the Au atoms in the cluster core and in the oligomeric SR(AuSR)x units in the cluster shell. Homogeneous and heterogeneous reactions catalyzed by atomic gold clusters are discussed in the context of the reaction mechanism and the nature of the active sites. The bibliography includes 345 references.

Self-assembled two-dimensional gold nanoparticle film for sensitive nontargeted analysis of food additives with surface-enhanced Raman spectroscopy.

PubMed

Wu, Yiping; Yu, Wenfang; Yang, Benhong; Li, Pan

2018-05-15

The use of different food additives and their active metabolites has been found to cause serious problems to human health. Thus, considering the potential effects on human health, developing a sensitive and credible analytical method for different foods is important. Herein, the application of solvent-driven self-assembled Au nanoparticles (Au NPs) for the rapid and sensitive detection of food additives in different commercial products is reported. The assembled substrates are highly sensitive and exhibit excellent uniformity and reproducibility because of uniformly distributed and high-density hot spots. The sensitive analyses of ciprofloxacin (CF), diethylhexyl phthalate (DEHP), tartrazine and azodicarbonamide at the 0.1 ppm level using this surface-enhanced Raman spectroscopy (SERS) substrate are given, and the results show that Au NP arrays can serve as efficient SERS substrates for the detection of food additives. More importantly, SERS spectra of several commercial liquors and sweet drinks are obtained to evaluate the addition of illegal additives. This SERS active platform can be used as an effective strategy in the detection of prohibited additives in food.

Applications of gold nanoparticles in virus detection

PubMed Central

Draz, Mohamed Shehata; Shafiee, Hadi

2018-01-01

Viruses are the smallest known microbes, yet they cause the most significant losses in human health. Most of the time, the best-known cure for viruses is the innate immunological defense system of the host; otherwise, the initial prevention of viral infection is the only alternative. Therefore, diagnosis is the primary strategy toward the overarching goal of virus control and elimination. The introduction of a new class of nanoscale materials with multiple unique properties and functions has sparked a series of breakthrough applications. Gold nanoparticles (AuNPs) are widely reported to guide an impressive resurgence in biomedical and diagnostic applications. Here, we review the applications of AuNPs in virus testing and detection. The developed AuNP-based detection techniques are reported for various groups of clinically relevant viruses with a special focus on the applied types of bio-AuNP hybrid structures, virus detection targets, and assay modalities and formats. We pay particular attention to highlighting the functional role and activity of each core Au nanostructure and the resultant detection improvements in terms of sensitivity, detection range, and time. In addition, we provide a general summary of the contributions of AuNPs to the mainstream methods of virus detection, technical measures, and recommendations required in guidance toward commercial in-field applications. PMID:29556369

Investigation of transparent zinc oxide-based contacts for high performance III-nitride light emitting diodes

NASA Astrophysics Data System (ADS)

Jung, Sungpyo

In this dissertation, we investigate Al-doped ZnO(AZO) contact structure to a variety of GaN LED structures. Our results show that ZnO is a potentially viable transparent contact for GaN-based LEDs. We began our investigation by depositing AZO and Ni/AZO contacts to p-GaN. However, these contacts are highly resistive. Next, we deposited thin Ni/Au layer, oxidized the Ni/Au layer to form a good ohmic contact to p-GaN, and then followed by the deposition of thick AZO layer. However, the electrical resistance of oxidized Ni/Au-AZO contacts is higher than that of the conventional Ni/Au contacts. We solve the high contact resistance problem by using a two-step thermal annealing process. In this method, Ni/Au layer is deposited first followed by the AZO layer without any annealing step. After finishing the device fabrication, the samples are annealed in air first to achieve low contact resistance with Ni/Au/AZO and p-GaN and then annealed in nitrogen to achieve low sheet resistance for the AZO layer. The improved electrical and optical characteristics of this scheme compared to conventional Ni/Au contact scheme are demonstrated on a variety of GaN LEDs: blue, green, small area, large area and bottom emitting LEDs. The benefits of ZnO-based contacts are more significant in large area LEDs that include lower forward voltage, and higher optical emission, better emission uniformity and reliability. The advantages of ZnO-based contact in terms of lower contact resistance and higher optical emission on LED fabricated on roughened GaN wafers are also demonstrated. For bottom emitting LED structure intended for flip chip applications, our original oxidized Ni/Au layer over coated with either Al or Ag contacts have shown to simultaneously yield superior I-V characteristics and greatly enhanced optical performance compared to conventional LEDs using a thick Ni/Au contact in the flip-chip configuration. However, the contact is unstable at operating temperatures > 100°C due to close proximity of Ag and Al with p-GaN. Here, the ZnO layer probably can be interdiffusion barrier layer of Al into GaN. We have demonstrated low contact resistance and higher light emission by using ZnO as a barrier material between oxidize Ni/Au and Al reflecting layer. In summary, our investigation demonstrates the applicability of ZnO-based transparent contacts for high performance LEDs that will be larger in size and are expected to be operating at higher current for solid-state lighting of the future. (Abstract shortened by UMI.)

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.

Mixed problems for the Korteweg-de Vries equation

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

Faminskii, A V

1999-06-30

Results are established concerning the non-local solubility and wellposedness in various function spaces of the mixed problem for the Korteweg-de Vries equation u{sub t}+u{sub xxx}+au{sub x}+uu{sub x}=f(t,x) in the half-strip (0,T)x(-{infinity},0). Some a priori estimates of the solutions are obtained using a special solution J(t,x) of the linearized KdV equation of boundary potential type. Properties of J are studied which differ essentially as x{yields}+{infinity} or x{yields}-{infinity}. Application of this boundary potential enables us in particular to prove the existence of generalized solutions with non-regular boundary values.

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

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

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

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

Weak convergence of a projection algorithm for variational inequalities in a Banach space

NASA Astrophysics Data System (ADS)

Iiduka, Hideaki; Takahashi, Wataru

2008-03-01

Let C be a nonempty, closed convex subset of a Banach space E. In this paper, motivated by Alber [Ya.I. Alber, Metric and generalized projection operators in Banach spaces: Properties and applications, in: A.G. Kartsatos (Ed.), Theory and Applications of Nonlinear Operators of Accretive and Monotone Type, in: Lecture Notes Pure Appl. Math., vol. 178, Dekker, New York, 1996, pp. 15-50], we introduce the following iterative scheme for finding a solution of the variational inequality problem for an inverse-strongly-monotone operator A in a Banach space: x1=x[set membership, variant]C andxn+1=[Pi]CJ-1(Jxn-[lambda]nAxn) for every , where [Pi]C is the generalized projection from E onto C, J is the duality mapping from E into E* and {[lambda]n} is a sequence of positive real numbers. Then we show a weak convergence theorem (Theorem 3.1). Finally, using this result, we consider the convex minimization problem, the complementarity problem, and the problem of finding a point u[set membership, variant]E satisfying 0=Au.

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.

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.

Light-controlled synthesis of gold nanoparticles using a rigid, photoresponsive surfactant

NASA Astrophysics Data System (ADS)

Huang, Youju; Kim, Dong-Hwan

2012-09-01

We report a new strategy for shape control over the synthesis of gold nanoparticles (AuNPs) by using a photoresponsive surfactant based on a modified seed growth method. Owing to photoresponsive properties of the azo group, the designed surfactant, N1,N3,N5-tris[(4'-azobenzene-4-sulphonic acid)phenyl]benzene-1,3,5-tricarboxamide, exhibits a distinctive molecular configuration under light leading to different growth processes of AuNPs. As a result, the blackberry-like, spherical AuNPs and multilayered Au plates were successfully prepared in high yield under visible and UV light. The size and morphological control of Au nanocrystals are described and the synthesized Au nanocrystals are evaluated for SERS applications.We report a new strategy for shape control over the synthesis of gold nanoparticles (AuNPs) by using a photoresponsive surfactant based on a modified seed growth method. Owing to photoresponsive properties of the azo group, the designed surfactant, N1,N3,N5-tris[(4'-azobenzene-4-sulphonic acid)phenyl]benzene-1,3,5-tricarboxamide, exhibits a distinctive molecular configuration under light leading to different growth processes of AuNPs. As a result, the blackberry-like, spherical AuNPs and multilayered Au plates were successfully prepared in high yield under visible and UV light. The size and morphological control of Au nanocrystals are described and the synthesized Au nanocrystals are evaluated for SERS applications. Electronic supplementary information (ESI) available: The UV-vis spectra, representative field-emission scanning electron microscopy (FESEM) images and size distributions of Au seeds (18 nm) and spherical AuNPs (50 nm), photograph images of AuNPs solution and TEM images of blackberry-like AuNPs. See DOI: 10.1039/c2nr31717f

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.

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.

Shape-Controlled Synthesis of Au Nanostructures Using EDTA Tetrasodium Salt and Their Photothermal Therapy Applications

PubMed Central

Jang, Youngjin; Lee, Nohyun; Kim, Jeong Hyun; Piao, Yuanzhe

2018-01-01

Tuning the optical properties of Au nanostructures is of paramount importance for scientific interest and has a wide variety of applications. Since the surface plasmon resonance properties of Au nanostructures can be readily adjusted by changing their shape, many approaches for preparing Au nanostructures with various shapes have been reported to date. However, complicated steps or the addition of several reagents would be required to achieve shape control of Au nanostructures. The present work describes a facile and effective shape-controlled synthesis of Au nanostructures and their photothermal therapy applications. The preparation procedure involved the reaction of HAuCl4 and ethylenediaminetetraacetic acid (EDTA) tetrasodium salt, which acted as a reducing agent and ligand, at room temperature without the need for any toxic reagent or additives. The morphology control from spheres to branched forms and nanowire networks was easily achieved by varying the EDTA concentration. Detailed investigations revealed that the four carboxylic groups of the EDTA tetrasodium salt are essential for effective growth and stabilization. The produced Au nanowire networks exhibited a broad absorption band in the near-infrared (NIR) region, thereby showing efficient cancer therapeutic performance by inducing the selective photothermal destruction of cancerous glioblastoma cells (U87MG) under NIR irradiation. PMID:29670020

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.

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

A biomimetic synthesis of stable gold nanoparticles derived from aqueous extract of Foeniculum vulgare seeds and evaluation of their catalytic activity

NASA Astrophysics Data System (ADS)

Choudhary, Manoj Kumar; Kataria, Jyoti; Sharma, Shweta

2017-10-01

A facile biomimetic approach for the synthesis of gold nanoparticles (AuNPs) using aqueous extract of fennel ( Foeniculum vulgare) seeds have been reported in this article. The seeds of F. vulgare are rich in various plant secondary metabolites (phytochemicals) such as polyphenolic acids, flavonoids, and saponins. The phytochemicals of F. vulgare seeds play dual role of reducing and stabilizing agents. The formation of gold nanoparticles was evidenced from the appearance of intense purple color at room temperature with λ max around 550 nm in the UV-Vis absorption spectra. The stable AuNPs were further characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) analysis. The synthesized nanoparticles were observed to be polydispersed, spherical and ranged from 10 to 30 nm with an average size of 20 ± 2 nm, as obtained from TEM images. The catalytic activity of gold nanoparticles was investigated by studying the reduction of anthropogenic dyes such as methylene blue (MB) and rhodamine B (Rh-B) with sodium borohydride. Results showed the possible applications of biogenic AuNPs in environment related problems.

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.

Exploration of new methods for growing Ag films on Au(111) studied by ARPES

NASA Astrophysics Data System (ADS)

Luh, Dah-An; Cheng, Cheng-Maw; Tsai, Chi-Ting; Tsuei, Ku-Ding

2007-03-01

Ag/Au(111) thin films have attracted lots of interests as a model system in the past decades. Ag and Au are lattice-matched, and thin Ag films of very high quality are expected to grow on Au(111). However, the intermixing between Ag and Au at elevated temperatures has been a major concern during the growth of Ag films on the Au(111) surface. In many previous studies, Ag was deposited on the Au(111) surface at near room temperature to avoid the intermixing problem. Investigating the results from these studies, the Ag films on Au(111) grown by this recipe still show clear thickness variation. This thickness variation may result from Ag-Au intermixing or film roughening during the process of room temperature deposition. We are revisiting this classical model system with new growth methods. Our goal is to find growth methods that will stop the intermixing between Ag and Au and reduce the variation in the thickness of Ag films. Preliminary results from our study will be presented in this poster.

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.

Designing Plasmonic Materials and Optical Metasurfaces for Light Manipulation and Optical Sensing

NASA Astrophysics Data System (ADS)

Chen, Wenxiang

Metamaterials are artificial materials designed to create optical properties that do not exist in nature. They are assemblies of subwavelength structures that are tailored in size, shape, composition, and orientation to realize the desired property. Metamaterials are promising for applications in diverse areas: optical filters, lenses, holography, sensors, photodetectors, photovoltaics, photocatalysts, medical devices, and many more, because of their excellent abilities in bending, absorbing, enhancing and blocking light. However, the practical use of metamaterials is challenged by the lack of plasmonic materials with proper permittivity for different applications and the slow and expensive fabrication methods available to pattern sub-wavelength structures. We have also only touched the surface in exploring the innovative uses of metamaterials to solve world problems. In this thesis, we study the fundamental optical properties of metamaterial building blocks by designing material permittivity. We continuously tune the interparticle distance in colloidal Au nanocrystal (NC) solids via the partial ligand exchange process. Then we combine top-down nanoimprint lithography with bottom-up assembly of colloidal NCs to develop a large-area, low-cost fabrication method for subwavelength nanostructures. Via this method, we fabricate and characterize nano-antenna arrays of different sizes and demonstrate metasurface quarter wave-plates of different bandwidth, and compare their performances with simulation results. We also integrate the metasurfaces with chemically- and mechanically-responsive polymers for strong-signal sensing. In the first design, we combine ultrathin plasmonic nanorods with hydrogel to fabricate optical moisture sensors for agricultural use. In the second application, we design mechanically tunable Au grating resonances on a polydimethylsiloxane (PDMS) substrate. The dimensions of Au grating are carefully engineered to achieve a hybridized, ultrasharp, and ultrasensitive resonance peak.

Synthesis and characterization of Au-MWCNT/PEDOT: PSS composite film for optoelectronic applications

NASA Astrophysics Data System (ADS)

Jasna, M.; Anjana, R.; Jayaraj, M. K.

2017-08-01

Recently, flexible organic optoelectronics have got great attention because of their light weight, mechanical flexibility and cost effective fabrication process. Conjugated polymers like PEDOT: PSS are widely used for the transparent electrode applications due to its chemical stability, high conductivity, flexibility and optical transparency in the visible region. Conductivity of the PEDOT: PSS polymer can be enhanced by adding organic solvents or conducting nano fillers like CNT, graphene, etc. Carbon nanotubes are good nano fillers to enhance the conductivity and mechanical strength of PEDOT: PSS composite film. Inthe present work, the effect of gold nano particles in PEDOT: PSS/CNT composite is studied. The conductivity enhancement in PEDOT: PSS/CNT thin films can be attributed to the formation of CNT network in the polymer matrix and conformational change of the PEDOT from benzoid to quinoid structure. Even though the conductivity was enhanced, the transparency of the composite thin films decreased with increase in CNT concentration. To overcome this problem, gold nano particles were attached to CNT walls via chemical route. AuMWCNT/PEDOT: PSS composite films were prepared by spin coating method. TEM images confirmed the decoration of gold nano particles on CNT walls. Electrical and optical properties of the composite films were studied. This simple solution processed conducting films are suitable for optoelectronic applications

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

Structure of the Si(111)-(5×2)-Au Surface

NASA Astrophysics Data System (ADS)

Abukawa, Tadashi; Nishigaya, Yoshiki

2013-01-01

The structure of the Si(111)-(5×2)-Au surface, one of the long-standing problems in surface science, has been solved by means of Weissenberg reflection high-energy electron diffraction. The arrangement of the Au atoms and their positions with respect to the substrate were determined from a three-dimensional Patterson function with a lateral resolution of 0.3 Å based on a large amount of diffraction data. The new structural model consists of six Au atoms in a 5×2 unit, which agrees with the recently confirmed Au coverage of 0.6 ML [I. Barke , Phys. Rev. B 79, 155301 (2009).PRBMDO1098-0121]. The model has a distinct ×2 periodicity, and includes a Au dimer. The model is also compatible with previously obtained STM images.

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.

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.

Chemically reduced graphene oxide-P25-Au nanocomposite materials and their photoelectrocatalytic and photocatalytic applications.

PubMed

Praveen, Raju; Ramaraj, Ramasamy

2016-10-05

Visible light active photocatalysts consisting of gold nanoparticle (Au NP) decorated chemically reduced graphene oxide-P25 nanocomposite materials (CRGO-P25-Au NCMs) were prepared through a one-pot chemical reduction method. The nanocomposite materials were characterized using diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and electrochemical impedance spectroscopy (EIS) analyses. The performances of CRGO-P25-Au NCM modified ITO electrodes were evaluated towards the photoelectrochemical oxidation of methanol. The photoelectrode fabricated using CRGO-P25-Au NCM exhibited a higher photocurrent of 293 μA cm -2 compared to other control electrodes. The CRGO-P25-Au NCMs were also used for the photocatalytic reduction of highly toxic chromium(vi) ions to chromium(iii) ions in the presence of oxalic acid as a sacrificial electron donor. The results showed that around 75% of the Cr(vi) ions were photocatalytically reduced to Cr(iii) ions by the CRGO-P25-Au NCM within the light irradiation time of 1 h. In both applications, the enhanced catalytic activity of the CRGO-P25-Au NCM was attributed to the improved visible light absorption and the reduced charge recombination exerted by the interaction of CRGO and Au NPs with P25 and their synergistic effects.

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

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.

First-Principles Study of Thermodynamic and Magnetic Properties of Alloys

NASA Astrophysics Data System (ADS)

Zhuravlev, Ivan

The standard theoretical framework for predicting phase diagrams and other thermodynamic properties of alloys requires an adequate representation of the formation enthalpy. An important part of the formation enthalpy in size-mismatched alloys comes from atomic relaxations. The harmonic Kanzaki-Krivoglaz-Khachaturyan model of strain-induced interaction is generalized to concentrated size-mismatched alloys and adapted to first-principles calculations. The configuration dependence of both Kanzaki forces and force constants is represented by real-space cluster expansions that can be constructed based on the calculated forces. Developed configuration-dependent lattice deformation model is implemented for the fcc lattice and applied to Cu1-x Aux and Fe1-x Ptx alloys for concentrations x = 0.25, 0.5, and 0.75. The model is further adapted to concentration wave analysis and Monte Carlo. Good agreement with experiment is found for all systems except CuAu3 and FePt3. The structural and ordering energetics are studied in Au-Fe alloys by combining DFT calculations with effective Hamiltonian techniques: a cluster expansion with structural filters, and CLDM. The phase separation tendency in Au-Fe persists even if the fcc-bcc decomposition is suppressed. The relative stability of disordered bcc and fcc phases observed in nanoparticles is reproduced, but the fully ordered L10 AuFe, L12 Au3Fe, and L1 2 AuFe3 structures are unstable in DFT. Effects of magnetism on the chemical ordering are also discussed. Magnetocrystalline anisotropy is one of the key properties of a magnetic material. Understanding of its temperature and concentration dependence is a challenging theoretical problem with implications for the design of better materials for permanent magnets and other applications. The origins of the anomalous temperature dependence of magnetocrystalline anisotropy in (Fe 1-xCox)2B alloys are elucidated using first-principles calculations within the disordered local moment model. Excellent agreement with experimental data is obtained. Electronic structure calculations are used to examine the magnetic properties of Fe2P-based alloys and the mechanisms through which the Curie temperature and magnetocrystalline anisotropy can be optimized for specific applications. It is found that at elevated temperatures the magnetic interaction in pure Fe2P develops a pronounced two-dimensional character. Co-alloying of Fe2P with Co (or Ni) and Si is suggested as a strategy for maximizing the magnetocrystalline anisotropy above room temperature.

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

Jiang, Deen

A profound connection has been found between the structures of thiolated gold clusters and the combinatorial problem of pairing up dots on a surface. The bridge is the concept of staple fitness: the fittest combination corresponds to the experimental structure. This connection has been demonstrated for both Au{sub 25}(SR){sub 18} and Au{sub 38}(SR){sub 24} (-SR being a thiolate group) and applied to predict a promising structure for the recently synthesized Au{sub 19}(SR){sub 13}.

Architecture of Pd-Au bimetallic nanoparticles in sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles as investigated by X-ray absorption spectroscopy.

PubMed

Chen, Ching-Hsiang; Sarma, Loka Subramanyam; Chen, Jium-Ming; Shih, Shou-Chu; Wang, Guo-Rung; Liu, Din-Goa; Tang, Mau-Tsu; Lee, Jyh-Fu; Hwang, Bing-Joe

2007-09-01

In this study, we demonstrate the unique application of X-ray absorption spectroscopy (XAS) as a fundamental characterization tool to help in designing and controlling the architecture of Pd-Au bimetallic nanoparticles within a water-in-oil microemulsion system of water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane. Structural insights obtained from the in situ XAS measurements recorded at each step during the formation process revealed that Pd-Au bimetallic clusters with various Pd-Au atomic stackings are formed by properly performing hydrazine reduction and redox transmetalation reactions sequentially within water-in-oil microemulsions. A structural model is provided to explain reasonably each reaction step and to give detailed insight into the nucleation and growth mechanism of Pd-Au bimetallic clusters. The combination of in situ XAS analysis at both the Pd K-edge and the Au L(III)-edge and UV-vis absorption spectral features confirms that the formation of Pd-Au bimetallic clusters follows a (Pd(nuclei)-Au(stack))-Pd(surf) stacking. This result further implies that the thickness of Au(stack) and Pd(surf) layers may be modulated by varying the dosage of the Au precursor and hydrazine, respectively. In addition, a bimetallic (Pd-Au)(alloy) nanocluster with a (Pd(nuclei)-Au(stack))-(Pd-Au(alloy))(surf) stacking was also designed and synthesized in order to check the feasibility of Pd(surf) layer modification. The result reveals that the Pd(surf) layer of the stacked (Pd(nuclei)-Au)(stack) bimetallic clusters can be successfully modified to form a (Au-Pd alloy)(surf) layer by a co-reduction of Pd and Au ions by hydrazine. Further, we demonstrate the alloying extent or atomic distribution of Pd and Au in Pd-Au bimetallic nanoparticles from the derived XAS structural parameters. The complete XAS-based methodology, demonstrated here on the Pd-Au bimetallic system, can easily be extended to design and control the alloying extent or atomic distribution, atomic stacking, and electronic structure to construct many other types of bimetallic systems for interesting applications.

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

Fabrication of fiber-optic localized surface plasmon resonance sensor and its application to detect antibody-antigen reaction of interferon-gamma

NASA Astrophysics Data System (ADS)

Jeong, Hyeon-Ho; Erdene, Norov; Lee, Seung-Ki; Jeong, Dae-Hong; Park, Jae-Hyoung

2011-12-01

A fiber-optic localized surface plasmon (FO LSPR) sensor was fabricated by gold nanoparticles (Au NPs) immobilized on the end-face of an optical fiber. When Au NPs were formed on the end-face of an optical fiber by chemical reaction, Au NPs aggregation occurred and the Au NPs were immobilized in various forms such as monomers, dimers, trimers, etc. The component ratio of the Au NPs on the end-face of the fabricated FO LSPR sensor was slightly changed whenever the sensors were fabricated in the same condition. Including this phenomenon, the FO LSPR sensor was fabricated with high sensitivity by controlling the density of Au NPs. Also, the fabricated sensors were measured for the resonance intensity for the different optical systems and analyzed for the effect on sensitivity. Finally, for application as a biosensor, the sensor was used for detecting the antibody-antigen reaction of interferon-gamma.

The application of aberration-corrected electron microscopy to the characterization of gold-based catalysts

NASA Astrophysics Data System (ADS)

Herzing, Andrew A.

Electron microscopy has long been used to study the morphology of heterogeneous catalysts. Recent advances in electron optics now allow for the correction of the inherent spherical aberration (Cs) produced by the objective lens in the scanning transmission electron microscope (STEM, resulting in a significantly improved spatial resolution as well as the ability to use a much larger probe-current than was previously possible. In this thesis, the combination of high-angle annular dark-field (HAADF) imaging and microanalysis by x-ray energy dispersive spectroscopy (XEDS) in an aberration-corrected STEM has been applied for the first time to the characterization of gold-based heterogeneous catalysts. Multi-variate statistical analysis (MSA) has been employed in order to further improve the STEM-XEDS spectrum image data acquired with this technique. In addition, supplemental analysis using electron-energy loss spectroscopy (EELS) and energy-filtered transmission electron microscopy (EFTEM) in an aberration-corrected instrument has also been attempted. These techniques have proven extremely valuable in providing complimentary information to more traditional catalyst characterization techniques such as x-ray photoelectron spectroscopy and x-ray diffraction in four specific problems relating to catalysis. Firstly, the atomic-scale resolution of Cs-corrected HAADF imaging has been utilized to study Au/FeOx catalysts in order to determine the size and structure of the Au clusters present on the support surface. It was discovered that, while both inactive and active catalysts for low-temperature CO oxidation contained large Au particles (> 5 nm) and individual Au atoms, the active catalyst also contained sub-nm clusters comprised of only a few Au atoms. Secondly, novel CeO2 support materials for Au and Au-Pd catalysts were synthesized by precipitation with supercritical CO2. These supports were found to produce significantly more active catalysts than those based on CeO2 prepared using more traditional methods. The combination of STEM-HAADF imaging and XEDS mapping has been used to characterize these catalysts and a strong correlation between the catalytic activity and the enhanced degree of metal dispersion over the support is demonstrated. Thirdly, a systematic series of Au-Pd/Al2O3 catalysts has been studied in order to characterize the effects of various heat treatments on the development of core-shell morphologies within the bi-metallic particles and its subsequent effect on their catalytic performance for H2O 2 synthesis. STEM-XEDS spectrum imaging was employed in order to determine the degree of alloying and segregation behavior within the individual Au-Pd particles as a function of calcination/reduction temperature. It was found that the as prepared catalyst contained homogeneous Au-Pd alloy particles and that a Pd-rich shell/Au-rich core morphology gradually developed upon calcination. Subsequent reduction of the catalyst caused a large fraction of the particles to invert and form Pd-rich core/Au-rich shell structures. These changes are related to both the activity and stability of the catalyst. Finally, the washing of activated carbon support materials in acid was found to be extremely beneficial for producing Au-Pd catalysts for the direct synthesis of H2O2. STEM-HAADF imaging revealed that the acid-washing treatment increased the dispersion of the metal on the carbon supports. Aberration-corrected STEM-XEDS spectrum imaging demonstrated a strong size dependence of the Au-Pd particle composition. Crucially, the acid-washing pre-treatment enhanced the alloying of Au and Pd by suppressing the formation of large (> 25 nm) Au-rich particles. In summary, the application of aberration-corrected HAADF imaging and STEM-XEDS spectrum imaging to the characterization of Au-based catalysts has enhanced the understanding of the structural and chemical features that determine their catalytic behavior. Specifically, they have allowed us to achieve the following: (a) image individual metal atoms and clusters of just a few atoms dispersed in a real, high surface area catalyst, (b) detect and follow the development of core-shell structures in Au-Pd bi-metallic catalysts, (c) determine composition/size correlations in Au-Pd catalysts, (d) detect minor alloying elements in bi-metallic catalysts, (e) and chemically map atomic or near atomic dispersions of metals on oxide supports.

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.

Comparative study of post-growth annealing of Cu(hfac)2, Co2(CO)8 and Me2Au(acac) metal precursors deposited by FEBID.

PubMed

Puydinger Dos Santos, Marcos Vinicius; Szkudlarek, Aleksandra; Rydosz, Artur; Guerra-Nuñez, Carlos; Béron, Fanny; Pirota, Kleber Roberto; Moshkalev, Stanislav; Diniz, José Alexandre; Utke, Ivo

2018-01-01

Non-noble metals, such as Cu and Co, as well as noble metals, such as Au, can be used in a number modern technological applications, which include advanced scanning-probe systems, magnetic memory and storage, ferroelectric tunnel junction memristors, metal interconnects for high performance integrated circuits in microelectronics and nano-optics applications, especially in the areas of plasmonics and metamaterials. Focused-electron-beam-induced deposition (FEBID) is a maskless direct-write tool capable of defining 3-dimensional metal deposits at nanometre scale for above applications. However, codeposition of organic ligands when using organometallic precursors is a typical problem that limits FEBID of pure metal nanostructures. In this work, we present a comparative study using a post-growth annealing protocol at 100, 200, and 300 °C under high vacuum on deposits obtained from Co 2 (CO) 8 , Cu(II)(hfac) 2 , and Me 2 Au(acac) to study improvements on composition and electrical conductivity. Although the as-deposited material was similar for all precursors, metal grains embedded in a carbonaceous matrix, the post-growth annealing results differed. Cu-containing deposits showed the formation of pure Cu nanocrystals at the outer surface of the initial deposit for temperatures above 100 °C, due to the migration of Cu atoms from the carbonaceous matrix containing carbon, oxygen, and fluorine atoms. The average size of the Cu crystals doubles between 100 and 300 °C of annealing temperature, while the composition remains constant. In contrast, for Co-containing deposits oxygen release was observed upon annealing, while the carbon content remained approximately constant; the cobalt atoms coalesced to form a metallic film. The as-deposited Au-containing material shows subnanometric grains that coalesce at 100 °C, maintaining the same average size at annealing temperatures up to 300 °C. Raman analysis suggests that the amorphous carbonaceous matrix of the as-written Co, Cu and Au deposits turned into nanocrystalline graphite with comparable crystal sizes of 12-14 nm at 300 °C annealing temperature. However, we observed a more effective formation of graphite clusters in Co- than in Cu- and Au-containing deposits. The graphitisation has a minor influence on the electrical conductivity improvements of Co-C deposits, which is attributed to the high as-deposited Co content and the related metal grain percolation. On the contrary, electrical conductivity improvements by factors of 30 and 12 for, respectively, Cu-C and Au-C deposits with low metal content are mainly attributed to the graphitisation. This relatively simple vacuum-based post-growth annealing protocol may be useful for other precursors as it proved to be efficient in reliably tuning the electrical properties of as-deposited FEBID materials. Finally, a H 2 -assisted gold purification protocol is demonstrated at temperatures around 300 °C by fully removing the carbon matrix and drastically reducing the electrical resistance of the deposit.

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.

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.

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.

Investigating the Synthesis, Structure, and Catalytic Properties of Versatile Gold-Based Nanocatalvsts

NASA Astrophysics Data System (ADS)

Pretzer, Lori A.

Transition metal nanomaterials are used to catalyze many chemical reactions, including those key to environmental, medicinal, and petrochemical fields. Improving their catalytic properties and lifetime would have significant economic and environmental rewards. Potentially expedient options to make such advancements are to alter the shape, size, or composition of transition metal nanocatalysts. This work investigates the relationships between structure and catalytic properties of synthesized Au, Pd-on-Au, and Au-enzyme model transition metal nanocatalysts. Au and Pd-on-Au nanomaterials were studied due to their wide-spread application and structure-dependent electronic and geometric properties. The goal of this thesis is to contribute design procedures and synthesis methods that enable the preparation of more efficient transition metal nanocatalysts. The influence of the size and composition of Pd-on-Au nanoparticles (NPs) was systematically investigated and each was found to affect the catalyst's surface structure and catalytic properties. The catalytic hydrodechlorination of trichloroethene and reduction of 4-nitrophenol by Pd-on-Au nanoparticles were investigated as these reactions are useful for environmental and pharmaceutical synthesis applications, respectively. Structural characterization revealed that the dispersion and oxidation state of surface Pd atoms are controlled by the Au particle size and concentration of Pd. These structural changes are correlated with observed Pd-on-Au NP activities for both probe reactions, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. Using the structure-dependent electronic properties of Au NPs, a new type of light-triggered biocatalyst was prepared and used to remotely control a model biochemical reaction. This biocatalyst consists of a model thermophilic glucokinase enzyme covalently attached to the surface of Au nanorods. The rod-like shape of the Au nanoparticles made the thermophilic-enzyme complexes responsive to near infrared electromagnetic radiation, which is absorbed minimally by biological tissues. When enzyme-Au nanorod complexes are illuminated with a near-infrared laser, thermal energy is generated which activates the thermophilic enzyme. Enzyme-Au nanorod complexes encapsulated in calcium alginate are reusable and stable for several days, making them viable for industrial applications. Lastly, highly versatile Au nanoparticles with diameters of ~3-12 nm were prepared using carbon monoxide (CO) to reduce a Au salt precursor onto preformed catalytic Au particles. Compared to other reducing agents used to generate metallic NPs, CO can be used at room temperature and its oxidized form does not interfere with the colloidal stability of NPs suspended in water. Controlled synthesis of different sized particles was verified through detailed ultraviolet-visible spectroscopy, small angle X-ray scattering, and transmission electron microscopy measurements. This synthesis method should be extendable to other monometallic and multimetallic compositions and shapes, and can be improved by using preformed particles with a narrower size distribution.

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

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.

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.

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.

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

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.

Monolayer coated gold nanoparticles for delivery applications

PubMed Central

Rana, Subinoy; Bajaj, Avinash; Mout, Rubul; Rotello, Vincent M.

2011-01-01

Gold nanoparticles (AuNPs) provide attractive vehicles for delivery of drugs, genetic materials, proteins, and small molecules. AuNPs feature low core toxicity coupled with the ability to parametrically control particle size and surface properties. In this review, we focus on engineering of the AuNP surface monolayer, highlighting recent advances in tuning monolayer structures for efficient delivery of drugs and biomolecules. This review covers two broad categories of particle functionalization, organic monolayers and biomolecule coatings, and discusses their applications in drug, DNA/RNA, protein and small molecule delivery. PMID:21925556

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.

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

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.

Environmentally Benign, Rapid, and Selective Extraction of Gold from Ores and Waste Electronic Materials.

PubMed

Yue, Chunlin; Sun, Huaming; Liu, Wen-Jing; Guan, Binbin; Deng, Xudong; Zhang, Xu; Yang, Peng

2017-08-01

The extraction of gold from ores and electronic waste is an important topic worldwide, as this precious metal has immense value in a variety of fields. However, serious environmental pollution and high energy consumption due to the use of toxic oxidation reagents and harsh reaction conditions is a well-known problem in the gold industry. Herein, we report a new chemical method based on the combined use of N-bromosuccinimide (NBS) and pyridine (Py), which has a greatly decreased environmental impact and reagent cost, as well as mild reaction requirements. This method can directly leach Au 0 from gold ore and electronic waste to form Au III in water. The process is achieved in a yield of approximately 90 % at room temperature and a nearly neutral pH. The minimum dose of NBS/Py is as low as 10 mm, which exhibits low toxicity towards mammalian cells and animals as well as aquatic creatures. The high leaching selectivity of Au over other metals during gold leaching is demonstrated, showing that this method has great potential for practical industrial application towards the sustainable refining of gold from ores and electronic waste. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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

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

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.

Development and Characterization of Liquid Crystal-Gold Nanoparticle Hybrid Materials for Optical Applications

NASA Astrophysics Data System (ADS)

Quint, Makiko T.

Hybrid material, mixtures of two or more materials with new properties, represents an exciting class of new materials for a variety of potential applications such as displays, optoelectronics, and sensors due to their unique physical and optical properties. The scope of this dissertation is to produce two new plasmonic applications by combining liquid crystals with gold nanoparticles. The first application is gold nanoparticle coated liquid crystal thin film. Most liquid crystal (LC) thin films require external voltage to reorient LC molecules. Recent advances in optical controlling technology of LC molecule behavior, resulting in the reduction of energy consumption, have stimulated research and development of new LC thin films. In order to re-orient LC molecules by just using light, the common approach is to include either a photo-responsive LC host, one that require high power light and severely narrows the range of usable materials, or add photo-active dye or polymer layer, photodegradation over time. Our work designing an all-optical method for LC re-orientation that overcomes all the limitations mentioned above. We have successfully both in- and out-of-plane spatial orientation of nematic liquid crystal (LC) molecules by leveraging the highly localized electric fields produced in the near-field regime of a gold nanoparticle (AuNP) layer. This re-orientation of LC molecules in thin LC-AuNP film is all-optical, driven by a small resonance excitation power with the localized surface plasmon absorption of the AuNPs at room temperature. The second application is LC mediated nano-assembled gold microcapsules. This application has a potential in controlled-release cargo-style delivery system. Targeted delivery systems with controlled release mechanisms have been the subject of extensive research more than fifty years. One is to control the release process remotely by using optical excitation. Optical actuation of delivery capsules, which plasmonic nanoparticle such as gold, allows rapid release at specific locations and uses the photothermal effect to unload contents. Almost all gold-based delivery applications including Au coated nanocrystals or AuNPs with soft materials like gels and polymers are not suitable for control release applications in real life since these applications do not provide robust leakage-free containment lower than the American National Standards Institute (ANSI) maximum permissible light exposure limit. We have successfully managed the difficulties mentioned above and produced a new gold-based delivery application. The application is spherical capsules with a densely packed wall of AuNPs. The rigid capsule wall allows encapsulation of cargo that can be contained, virtually leakage-free, over several months. Further, by leveraging LSPR of AuNPs, we can rupture the microshells using optical excitation with ultralow power (< 2 mW), controllably and rapidly releasing the encapsulated contents in less than 5 seconds. Our results exhibiting the capture and optically regulated release of encapsulated substances are a novel platform that combines controlled-release cargo-style delivery and photothermal therapy in one versatile and multifunctional unit. Both our applications are overcoming current limitations and promising future research directions towards the next generation of LC-AuNPs hybrid material research and developments.

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.

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.

Long Term Measurement of the Vapor Pressure of Gold in the Au-C System

NASA Technical Reports Server (NTRS)

Copland, Evan H.

2009-01-01

Incorporating the {Au(s,l) + graphite} reference in component activity measurements made with the multiple effusion-cell vapor source mass spectrometry (multicell KEMS) technique provides a fixed temperature defining ITS-90 (T(sub mp)(Au) = 1337.33K) and a systematic method to check accuracy. Over a 2 year period delta H sub(298)Au was determined by the 2nd and 3rd law methods in 25 separate experiments and were in the ranges 362.2 plus or minus 3.3 kJmol(sup -1) and 367.8 plus or minus 1.1 kJmol(sup -1), respectively. This 5 kJmol-1 discrepancy is transferred directly to the measured activities. This is unacceptable and the source of this discrepancy needs to be understood and corrected. Accepting the 2nd law value increases p(Au) by about 50 percent, brings the 2nd and 3rd law values into agreement and removes the T dependence in the 3rd law values. While compelling, there is no way to independently determine instrument sensitivities, S(sub Au), with T in a single experiment with KEMS. This lack of capability is stopping a deeper understanding of this problem. In addition, the Au-C phase diagram suggests a eutectic invariant reaction: L-Au(4.7at%C) = FCC-Au(0.08at%C) + C(graphite) at T(sub e) approximately 1323K. This high C concentration in Au(l) must reduce p(Au) in equilibrium with {Au(s,l) + graphite} and raises some critical questions about the Gibbs free energy functions of Au(s,l) and the Au fixed point (T(sub mp)(Au) = 1337.33K) which is always measured in graphite.

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.

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.

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.

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.

Acoustic emission and acousto-ultrasonic techniques for wood and wood-based composites: a review

Treesearch

Sumire Kawamoto; R. Sam Williams

2002-01-01

This review focuses on the feasibility of acoustic emission (AE) and acousto-ultrasonic (AU) techniques for monitoring defects in wood, particularly during drying. The advantages and disadvantages of AE and AU techniques are described. Particular emphasis is placed on the propagation and attenuation of ultrasonic waves in wood and the associated measurement problems....

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

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.

Galvanic corrosion behaviors of Cu connected to Au on a printed circuit board in ammonia solution

NASA Astrophysics Data System (ADS)

Oh, SeKwon; Kim, YoungJun; Jung, KiMin; Park, MiSeok; Shon, MinYoung; Kwon, HyukSang

2018-01-01

During etching treatments of printed circuit board (PCB) with ammnioa solution, galvanic corrosion occurs between electrically connected gold and copper, and resulting in unexpected over-etching problems. Herein, we determine corrosion of galvanic coupled Cu to Au quantitatively in ammonia solutions, and evaluate factors influencing corrosion of galvanic coupled Cu to Au (i.e., area ratio of anode to cathode and stirring speed). The difference of the corrosion rate (Δi = icouple, (Cu-Au)-icorr, Cu) of Cu connected to Au (117 μA/cm2) and of single Cu (86 μA/cm2) infers the amount of over-etching of Cu resulting from galvanic corrosion in ammonia solution (Δi = 0.31 μA/cm2). As the stirring speed increases from 0 to 400 rpm, the corrosion rate of galvanic coupled Cu to Au increases from 36 to 191 μA/cm2. Furthermore, we confirm that an increase in the area ratio (Au/Cu) from 0.5 to 25 results in a higher rate of corrosion of Cu connected to Au. The corrosion rate of galvanic coupled Cu to Au is approximately 20 times higher when the area ratio of Au to Cu is 25 (1360 μA/cm2) than when the ratio is 0.5 (67 μA/cm2).

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.

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.

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.

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.

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.

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.

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

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

Improving Efficiency in Multi-Strange Baryon Reconstruction in d-Au at STAR

NASA Astrophysics Data System (ADS)

Leight, William

2003-10-01

We report preliminary multi-strange baryon measurements for d-Au collisions recorded at RHIC by the STAR experiment. After using classical topological analysis, in which cuts for each discriminating variable are adjusted by hand, we investigate improvements in signal-to-noise optimization using Linear Discriminant Analysis (LDA). LDA is an algorithm for finding, in the n-dimensional space of the n discriminating variables, the axis on which the signal and noise distributions are most separated. LDA is the first step in moving towards more sophisticated techniques for signal-to-noise optimization, such as Artificial Neural Nets. Due to the relatively low background and sufficiently high yields of d-Au collisions, they form an ideal system to study these possibilities for improving reconstruction methods. Such improvements will be extremely important for forthcoming Au-Au runs in which the size of the combinatoric background is a major problem in reconstruction efforts.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

A Flexible Caterpillar-Like Gold Nanoparticle Assemblies with Ultrasmall Nanogaps for Enhanced Dual-Modal Imaging and Photothermal Therapy.

PubMed

Xia, Yuanzhi; Ma, Xuehua; Gao, Junhua; Chen, Guoxin; Li, Zihou; Wu, Xiaoxia; Yu, Zhangsen; Xing, Jie; Sun, Li; Ruan, Huimin; Luo, Lijia; Xiang, Lingchao; Dong, Chen; Ren, Wenzhi; Shen, Zheyu; Wu, Aiguo

2018-05-01

Gold nanoparticle (AuNP) assemblies (GNAs) have attracted attention since enhanced coupling plasmonic resonance (CPR) emerged in the nanogap between coupling AuNPs. For one dimensional GNAs (1D-GNAs), most CPR from the nanogaps could be easily activated by electromagnetic waves and generate drastically enhanced CPR because the nanogaps between coupling AuNPs are linearly distributed in the 1D-GNAs. The reported studies focus on the synthesis of 1D-GNAs and fundamental exploration of CPR. There are still problems which impede further applications in nanomedicine, such as big size (>500 nm), poor water solubility, and/or poor stability. In this study, a kind of 1D flexible caterpillar-like GNAs (CL-GNAs) with ultrasmall nanogaps, good water solubility, and good stability is developed. The CL-GNAs have a flexible structure that can randomly move to change their morphology, which is rarely reported. Numerous ultrasmall nanogaps (<1 nm) are linearly distributed along the structure of CL-GNAs and generate enhanced CPR. The toxicity assessments in vitro and vivo respectively demonstrate that CL-GNAs have a low cytotoxicity and good biocompatibility. The CL-GNAs can be used as an efficient photothermal agent for photothermal therapy, a probe for Raman imaging and photothermal imaging. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Stabilizing ultrasmall Au clusters for enhanced photoredox catalysis.

PubMed

Weng, Bo; Lu, Kang-Qiang; Tang, Zichao; Chen, Hao Ming; Xu, Yi-Jun

2018-04-18

Recently, loading ligand-protected gold (Au) clusters as visible light photosensitizers onto various supports for photoredox catalysis has attracted considerable attention. However, the efficient control of long-term photostability of Au clusters on the metal-support interface remains challenging. Herein, we report a simple and efficient method for enhancing the photostability of glutathione-protected Au clusters (Au GSH clusters) loaded on the surface of SiO 2 sphere by utilizing multifunctional branched poly-ethylenimine (BPEI) as a surface charge modifying, reducing and stabilizing agent. The sequential coating of thickness controlled TiO 2 shells can further significantly improve the photocatalytic efficiency, while such structurally designed core-shell SiO 2 -Au GSH clusters-BPEI@TiO 2 composites maintain high photostability during longtime light illumination conditions. This joint strategy via interfacial modification and composition engineering provides a facile guideline for stabilizing ultrasmall Au clusters and rational design of Au clusters-based composites with improved activity toward targeting applications in photoredox catalysis.

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...

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

Tunable, biodegradable gold nanoparticles as contrast agents for computed tomography and photoacoustic imaging

PubMed Central

Cheheltani, Rabee; Ezzibdeh, Rami M.; Chhour, Peter; Pulaparthi, Kumidini; Kim, Johoon; Jurcova, Martina; Hsu, Jessica C.; Blundell, Cassidy; Litt, Harold I.; Ferrari, Victor A.; Allcock, Harry R.; Sehgal, Chandra M.; Cormode, David P.

2016-01-01

Gold nanoparticles (AuNP) have been proposed for many applications in medicine. Although large AuNP (>5.5 nm) are desirable for their longer blood circulation and accumulation in diseased tissues, small AuNP (<5.5 nm) are required for excretion via the kidneys. We present a novel platform where small, excretable AuNP are encapsulated into biodegradable poly di(carboxylatophenoxy)phosphazene (PCPP) nanospheres. These larger nanoparticles (Au-PCPP) can perform their function as contrast agents, then subsequently break down into harmless byproducts and release the AuNP for swift excretion. Homogeneous Au-PCPP were synthesized using a microfluidic device. The size of the Au-PCPP can be controlled by the amount of polyethylene glycol-polylysine (PEG-PLL) block co-polymer in the formulation. Synthesis of Au-PCPP nanoparticles and encapsulation of AuNP in PCPP were evaluated using transmission electron microscopy and their biocompatibility and biodegradability confirmed in vitro. The Au-PCPP nanoparticles were found to produce strong computed tomography contrast. The UV-Vis absorption peak of Au-PCPP can be tuned into the near infrared region via inclusion of varying amounts of AuNP and controlling the nanoparticle size. In vitro and in vivo experiments demonstrated the potential of Au-PCPP as contrast agents for photoacoustic imaging. Therefore, Au-PCPP nanoparticles have high potency as contrast agents for two imaging modalities, as well as being biocompatible and biodegradable, and thus represent a platform with potential for translation into the clinic. PMID:27322961

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.

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.

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.

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).

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

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.

A sensitive electrochemical impedance immunosensor for determination of malachite green and leucomalachite green in the aqueous environment.

PubMed

Zhu, Dan; Li, Qiangqiang; Pang, Xiumei; Liu, Yue; Wang, Xue; Chen, Gang

2016-08-01

Application of malachite green (MG) and leucomalachite green (LMG) in fish farm water causes an environmental problem. This study proposes for the first time a sensitive and convenient electrochemical impedance spectroscopy (EIS) method for determining MG and LMG by a bovine serum albumin-decorated gold nanocluster (BSA-AuNC)/antibody composite film-based immunosensor. In order to improve the analytical performance, the glassy carbon electrode (GCE) was modified with 1, 4-phenylenediamine to form a stable layer, and then, BSA-AuNCs were covalently bound to the GCE. An adequate quantity of the polyclonal antibody of LMG was immobilized onto the surface of the BSA-AuNCs by the chemical reaction of EDC/NHS. The sensors can respond to the specific target based on specific covalent bonding. The experimental parameters, such as the pH, incubating concentration, and time, have been investigated and optimized. The calibration curve for LMG was linear in the range of 0.1~10.0 ng/mL with the limit of detection (LOD) 0.03 ng/mL. Furthermore, the sum of MG and LMG was detected in fish farm water by MG reduction. The recovery was between 89.7 % and 99.2 % in spiked samples. The EC sensor method was also compared with the ELISA method and validated by the LC-MS/MS method, which proves its great promise as a field instrument for the rapid monitoring of MG and LMG pollution. Graphical abstract 1, 4-Phenylenediamine and BSA-AuNC/antibody-decorated glassy carbon electrodes have been used for the impedimetric detection of the sum of malachite green and leucomalachite green via specific immuno-binding.

Periodic Trojan-type orbits in the earth-sun system

NASA Technical Reports Server (NTRS)

Weissman, P. R.; Wetherill, G. W.

1974-01-01

Periodic orbits about the triangular equilibrium points are found for the planar restricted three-body problem using the earth-sun system. The maximum semimajor axis for tadpole orbits ranges from the infinitesimal orbit at 1.000 AU to the near-limiting orbit at 1.00285 AU. Horseshoe orbits are found for 1.0029 to 1.0080 AU, larger horseshoes being unstable because of close approaches to the earth. Using stability tests devised by Rabe (1961, 1962), the limit of stability for nonperiodic orbits is found to occur for maximum semimajor axes near 1.0020 AU. In addition, near-periodic tadpole orbits appear to be stable against perturbations by Jupiter and Venus for periods of at least 10,000 yr. The possibility that minor planets actually exist in such orbits is considered.

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.

Fabrication par injection flexible de pieces coniques pour des applications aerospatiales

NASA Astrophysics Data System (ADS)

Shebib Loiselle, Vincent

Les materiaux composites sont presents dans les tuyeres de moteurs spatiaux depuis les annees soixante. Aujourd'hui, l'avenement des tissus tridimensionnels apporte une solution innovatrice au probleme de delamination qui limitait les proprietes mecaniques de ces composites. L'utilisation de ces tissus necessite toutefois la conception de procedes de fabrication mieux adaptes. Une nouvelle methode de fabrication de pieces composites pour des applications aerospatiales a ete etudiee tout au long de ce travail. Celle-ci applique les principes de l'injection flexible (procede Polyflex) a la fabrication de pieces coniques de fortes epaisseurs. La piece de validation a fabriquer represente un modele reduit de piece de tuyere de moteur spatial. Elle est composee d'un renfort tridimensionnel en fibres de carbone et d'une resine phenolique. La reussite du projet est definie par plusieurs criteres sur la compaction et la formation de plis du renfort et sur la formation de porosites de la piece fabriquee. Un grand nombre d'etapes ont ete necessaires avant la fabrication de deux pieces de validation. Premierement, pour repondre au critere sur la compaction du renfort, la conception d'un outil de caracterisation a ete entreprise. L'etude de la compaction a ete effectuee afin d'obtenir les informations necessaires a la comprehension de la deformation d'un renfort 3D axisymetrique. Ensuite, le principe d'injection de la piece a ete defini pour ce nouveau procede. Pour en valider les concepts proposes, la permeabilite du renfort fibreux ainsi que la viscosite de la resine ont du etre caracterisees. A l'aide de ces donnees, une serie de simulations de l'ecoulement pendant l'injection de la piece ont ete realisees et une approximation du temps de remplissage calculee. Apres cette etape, la conception du moule de tuyere a ete entamee et appuyee par une simulation mecanique de la resistance aux conditions de fabrication. Egalement, plusieurs outillages necessaires pour la fabrication ont ete concus et installes au nouveau laboratoire CGD (composites grandes dimensions). En parallele, plusieurs etudes ont ete effectuees pour comprendre les phenomenes influencant la polymerisation de la resine.

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

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.

Characterization of opto-electrical enhancement of tandem photoelectrochemical cells by using photoconductive-AFM

NASA Astrophysics Data System (ADS)

Park, Sun-Young; Elbersen, Rick; Huskens, Jurriaan; Gardeniers, Han; Lee, Joo-Yul; Mul, Guido; Heo, Jinhee

2017-07-01

Solar-to-hydrogen conversion by water splitting in photoelectrochemical cells (PECs) is a promising approach to alleviate problems associated with intermittency in solar energy supply and demand. Several interfacial resistances in photoelectrodes limit the performance of such cells, while the properties of interfaces are not easy to analyze in situ. We applied photoconductive-AFM to analyze the performance of WO3/p+n Si photoanodes, containing an ultra-thin metal interface of either Au or Pt. The Au interface consisted of Au nanoparticles with well-ordered interspacing, while Pt was present in the form of a continuous film. Photoconductive-AFM data show that upon illumination significantly larger currents are measured for the WO3/p+n Si anode equipped with the Au interface, as compared to the WO3/p+n Si anode with the Pt interface, in agreement with the better performance of the former electrode in a photoelectrochemical cell. The remarkable performance of the Au-containing electrode is proposed to be the result of favorable electron-hole recombination rates induced by the Au nanoparticles in a plasmon resonance excited state.

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.

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.

Au-decorated sodium titanate nanotubes as high-performance selective photocatalysts for pollutant degradation

NASA Astrophysics Data System (ADS)

El Rouby, Waleed M. A.; Comesaña-Hermo, Miguel; Testa-Anta, Martín; Carbó-Argibay, Enrique; Salgueiriño, Verónica; Pérez-Lorenzo, Moisés; Correa-Duarte, Miguel A.

2017-04-01

The bioaccumulation of polycyclic aromatic compounds originating from textile processing industries is nowadays a major environmental problem worldwide. In order to tackle this situation, several inorganic semiconductors have been tested as photocatalysts for the degradation of these harmful pollutants in the search of sustainable and cost-effective solutions. Nevertheless, these semiconductor materials often involve important limitations, such as poor efficiency and selectivity, which, in the end, substantially restrict their implementation at the industrial scale. As an alternative, we herein report the fabrication and application of Au-decorated titanate nanotubes (TNTs) as high-performance architectures for the selective degradation of organic contaminants. This synthetic strategy is intended to establish a synergetic integration of the physicochemical and photocatalytic features of these hybrid nanostructures, by combining the remarkable adsorption capabilities of TNTs with the enhanced light-harvesting efficiency provided by the incorporation of a noble metal component. The obtained results evidence the great potential that rationally designed plasmonic composites may have for the development of selective environmental remediation technologies and in particular on the current challenges faced by the wastewater treatment sector.

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.

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.

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

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.

Cu-Au alloy nanostructures coated with aptamers: a simple, stable and highly effective platform for in vivo cancer theranostics

NASA Astrophysics Data System (ADS)

Ye, Xiaosheng; Shi, Hui; He, Xiaoxiao; Yu, Yanru; He, Dinggeng; Tang, Jinlu; Lei, Yanli; Wang, Kemin

2016-01-01

As a star material in cancer theranostics, photoresponsive gold (Au) nanostructures may still have drawbacks, such as low thermal conductivity, irradiation-induced melting effect and high cost. To solve the problem, copper (Cu) with a much higher thermal conductivity and lower cost was introduced to generate a novel Cu-Au alloy nanostructure produced by a simple, gentle and one-pot synthetic method. Having the good qualities of both Cu and Au, the irregularly-shaped Cu-Au alloy nanostructures showed several advantages over traditional Au nanorods, including a broad and intense near-infrared (NIR) absorption band from 400 to 1100 nm, an excellent heating performance under laser irradiation at different wavelengths and even a notable photostability against melting. Then, via a simple conjugation of fluorophore-labeled aptamers on the Cu-Au alloy nanostructures, active targeting and signal output were simultaneously introduced, thus constructing a theranostic platform based on fluorophore-labeled, aptamer-coated Cu-Au alloy nanostructures. By using human leukemia CCRF-CEM cancer and Cy5-labeled aptamer Sgc8c (Cy5-Sgc8c) as the model, a selective fluorescence imaging and NIR photothermal therapy was successfully realized for both in vitro cancer cells and in vivo tumor tissues. It was revealed that Cy5-Sgc8c-coated Cu-Au alloy nanostructures were not only capable of robust target recognition and stable signal output for molecular imaging in complex biological systems, but also killed target cancer cells in mice with only five minutes of 980 nm irradiation. The platform was found to be simple, stable, biocompatible and highly effective, and shows great potential as a versatile tool for cancer theranostics.As a star material in cancer theranostics, photoresponsive gold (Au) nanostructures may still have drawbacks, such as low thermal conductivity, irradiation-induced melting effect and high cost. To solve the problem, copper (Cu) with a much higher thermal conductivity and lower cost was introduced to generate a novel Cu-Au alloy nanostructure produced by a simple, gentle and one-pot synthetic method. Having the good qualities of both Cu and Au, the irregularly-shaped Cu-Au alloy nanostructures showed several advantages over traditional Au nanorods, including a broad and intense near-infrared (NIR) absorption band from 400 to 1100 nm, an excellent heating performance under laser irradiation at different wavelengths and even a notable photostability against melting. Then, via a simple conjugation of fluorophore-labeled aptamers on the Cu-Au alloy nanostructures, active targeting and signal output were simultaneously introduced, thus constructing a theranostic platform based on fluorophore-labeled, aptamer-coated Cu-Au alloy nanostructures. By using human leukemia CCRF-CEM cancer and Cy5-labeled aptamer Sgc8c (Cy5-Sgc8c) as the model, a selective fluorescence imaging and NIR photothermal therapy was successfully realized for both in vitro cancer cells and in vivo tumor tissues. It was revealed that Cy5-Sgc8c-coated Cu-Au alloy nanostructures were not only capable of robust target recognition and stable signal output for molecular imaging in complex biological systems, but also killed target cancer cells in mice with only five minutes of 980 nm irradiation. The platform was found to be simple, stable, biocompatible and highly effective, and shows great potential as a versatile tool for cancer theranostics. Electronic supplementary information (ESI) available: Fig. S1, S2 and Table S1. See DOI: 10.1039/c5nr07017a

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

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.

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

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

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.

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.

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.

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

Multifunctional Au NPs-polydopamine-polyvinylidene fluoride membrane chips as probe for enrichment and rapid detection of organic contaminants.

PubMed

Wang, Saihua; Niu, Hongyun; Cai, Yaqi; Cao, Dong

2018-05-01

High-throughput and rapid detection of hazardous compounds in complicated samples is essential for the solution of environmental problems. We have prepared a "pH-paper-like" chip which can rapidly "indicate" the occurrence of organic contaminants just through dipping the chip in water samples for short time followed by fast analysis with surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS). The chips are composed of polyvinylidene fluoride membrane (PVDFM), polydopamine (PDA) film and Au nanoparticles (Au NPs), which are layer-by-layer assembled according to the adhesion, self-polymerization and reduction property of dopamine. In the Au NPs loaded polydopamine-polyvinylidene fluoride membrane (Au NPs-PDA-PVDFM) chips, PVDFM combined with PDA film are responsible for the enrichment of organic analyte through hydrophobic interactions and π-π stacking; Au NPs serve as effective SALDI matrix for the rapid detection of target analyte. After dipping into water solution for minutes, the Au-PDA-PVDFM chips with enriched organic analytes can be detected directly with SALDI-TOF MS. The good solid-phase extraction performance of the PDA-PVDFM components, remarkable matrix effect of the loaded AuNPs, and sensitivity of the SALDI-TOF MS technique ensure excellent sensitivity and reproducibility for the quantification of trace levels of organic contaminants in environmental water samples. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

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.

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.

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.

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.

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.

Ordered Monolayer Gold Nano-urchin Structures and Their Size Induced Control for High Gas Sensing Performance

PubMed Central

Sabri, Ylias M.; Kandjani, Ahmad Esmaielzadeh; Ippolito, Samuel J.; Bhargava, Suresh K.

2016-01-01

The synthesis of ordered monolayers of gold nano-urchin (Au-NU) nanostructures with controlled size, directly on thin films using a simple electrochemical method is reported in this study. In order to demonstrate one of the vast potential applications, the developed Au-NUs were formed on the electrodes of transducers (QCM) to selectively detect low concentrations of elemental mercury (Hg0) vapor. It was found that the sensitivity and selectivity of the sensor device is enhanced by increasing the size of the nanospikes on the Au-NUs. The Au-NU-12 min QCM (Au-NUs with nanospikes grown on it for a period of 12 min) had the best performance in terms of transducer based Hg0 vapor detection. The sensor had 98% accuracy, 92% recovery, 96% precision (repeatability) and significantly, showed the highest sensitivity reported to date, resulting in a limit of detection (LoD) of only 32 μg/m3 at 75 °C. When compared to the control counterpart, the accuracy and sensitivity of the Au-NU-12 min was enhanced by ~2 and ~5 times, respectively. The results demonstrate the excellent activity of the developed materials which can be applied to a range of applications due to their long range order, tunable size and ability to form directly on thin-films. PMID:27090570

Ordered Monolayer Gold Nano-urchin Structures and Their Size Induced Control for High Gas Sensing Performance

NASA Astrophysics Data System (ADS)

Sabri, Ylias M.; Kandjani, Ahmad Esmaielzadeh; Ippolito, Samuel J.; Bhargava, Suresh K.

2016-04-01

The synthesis of ordered monolayers of gold nano-urchin (Au-NU) nanostructures with controlled size, directly on thin films using a simple electrochemical method is reported in this study. In order to demonstrate one of the vast potential applications, the developed Au-NUs were formed on the electrodes of transducers (QCM) to selectively detect low concentrations of elemental mercury (Hg0) vapor. It was found that the sensitivity and selectivity of the sensor device is enhanced by increasing the size of the nanospikes on the Au-NUs. The Au-NU-12 min QCM (Au-NUs with nanospikes grown on it for a period of 12 min) had the best performance in terms of transducer based Hg0 vapor detection. The sensor had 98% accuracy, 92% recovery, 96% precision (repeatability) and significantly, showed the highest sensitivity reported to date, resulting in a limit of detection (LoD) of only 32 μg/m3 at 75 °C. When compared to the control counterpart, the accuracy and sensitivity of the Au-NU-12 min was enhanced by ~2 and ~5 times, respectively. The results demonstrate the excellent activity of the developed materials which can be applied to a range of applications due to their long range order, tunable size and ability to form directly on thin-films.

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.

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.

Acidifier application rate impacts on ammonia emissions from US roaster chicken houses

NASA Astrophysics Data System (ADS)

Shah, Sanjay B.; Grimes, Jesse L.; Oviedo-Rondón, Edgar O.; Westerman, Philip W.

2014-08-01

Due to its potential environmental and public health impacts, emissions of ammonia (NH3) as well as several other gases from US livestock farms may be regulated. Broiler houses are important sources of NH3 emissions. However, there are no emissions data from roaster (8-12 wk old broilers, ˜4 kg ea.) houses. Producers treat the litter in broiler houses with acidifiers, such as sodium bisulfate (SBS, NaHSO4) to reduce ammonia production and protect bird health. However, there is very little data on the effect of acidifiers, particularly at high application rates on ammonia emissions. The impact of different SBS application rates [High (0.95-1.46 kg m-2, whole house), Medium (0.73 kg m-2, whole house), Low (0.37-0.49 kg m-2, whole house), and Control (0.37-0.49 kg m-2, brood chamber)] on ammonia emissions was evaluated in commercial roaster houses over 22 months spanning eight flocks. Ammonia emission from each fan was measured with an acid scrubber that operated only when the fan operated. Emissions were calculated using >95% measured data with the rest being estimated using robust methods. Exhaust ammonia-N concentrations were inversely correlated with the SBS application rates. Emission rates on animal unit (AU, where 1 AU = 500 kg live-mass) basis (ER, g d-1 AU-1) were reduced by 27, 13, and 5%, respectively, in the High, Medium, and Low treatments vs. the Control treatment (mean: 100 g d-1 AU-1, range: 86-114 g d-1 AU-1). Emission rates for the Control treatment measured in this study on roasters were mostly higher than ERs in the literature. Differences in ERs are not only due to diet, environmental and management conditions, but also due to measurement methods.

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.

Uniform Gold-Nanoparticle-Decorated {001}-Faceted Anatase TiO2 Nanosheets for Enhanced Solar-Light Photocatalytic Reactions.

PubMed

Shi, Huimin; Zhang, Shi; Zhu, Xupeng; Liu, Yu; Wang, Tao; Jiang, Tian; Zhang, Guanhua; Duan, Huigao

2017-10-25

The {001}-faceted anatase TiO 2 micro-/nanocrystals have been widely investigated for enhancing the photocatalysis and photoelectrochemical performance of TiO 2 nanostructures, but their practical applications still require improved energy conversion efficiency under solar-light and enhanced cycling stability. In this work, we demonstrate the controlled growth of ultrathin {001}-faceted anatase TiO 2 nanosheets on flexible carbon cloth for enhancing the cycling stability, and the solar-light photocatalytic performance of the synthesized TiO 2 nanosheets can be significantly improved by decorating with vapor-phase-deposited uniformly distributed plasmonic gold nanoparticles. The fabricated Au-TiO 2 hybrid system shows an 8-fold solar-light photocatalysis enhancement factor in photodegrading Rhodamine B, a high photocurrent density of 300 μA cm -2 under the illumination of AM 1.5G, and 100% recyclability under a consecutive long-term cycling measurement. Combined with electromagnetic simulations and systematic control experiments, it is believed that the tandem-type separation and transition of plasmon-induced hot electrons from Au nanoparticles to the {001} facet of anatase TiO 2 , and then to the neighboring {101} facet, is responsible for the enhanced solar-light photochemical performance of the hybrid system. The Au-TiO 2 nanosheet system addresses well the problems of the limited solar-light response of anatase TiO 2 and fast recombination of photogenerated electron-hole pairs, representing a promising high-performance recyclable solar-light-responding system for practical photocatalytic reactions.

Magnetic gold nanocatalyst (nanocat-Fe–Au): catalytic applications for the oxidative esterification and hydrogen transfer reactions

EPA Science Inventory

An efficient and sustainable protocol is described for the oxidative esterification of aldehydes and the reduction of aromatic nitro compounds that uses magnetically separable and reusable maghemite-supported gold nanocatalyst (nanocat-Fe-Au) under mild conditions. The complex ch...

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.

Biosynthesis of gold nanoparticles by the extreme bacterium Deinococcus radiodurans and an evaluation of their antibacterial properties.

PubMed

Li, Jiulong; Li, Qinghao; Ma, Xiaoqiong; Tian, Bing; Li, Tao; Yu, Jiangliu; Dai, Shang; Weng, Yulan; Hua, Yuejin

Deinococcus radiodurans is an extreme bacterium known for its high resistance to stresses including radiation and oxidants. The ability of D. radiodurans to reduce Au(III) and biosynthesize gold nanoparticles (AuNPs) was investigated in aqueous solution by ultraviolet and visible (UV/Vis) absorption spectroscopy, electron microscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). D. radiodurans efficiently synthesized AuNPs from 1 mM Au(III) solution in 8 h. The AuNPs were of spherical, triangular and irregular shapes with an average size of 43.75 nm and a polydispersity index of 0.23 as measured by DLS. AuNPs were distributed in the cell envelope, across the cytosol and in the extracellular space. XRD analysis confirmed the crystallite nature of the AuNPs from the cell supernatant. Data from the FTIR and XPS showed that upon binding to proteins or compounds through interactions with carboxyl, amine, phospho and hydroxyl groups, Au(III) may be reduced to Au(I), and further reduced to Au(0) with the capping groups to stabilize the AuNPs. Biosynthesis of AuNPs was optimized with respect to the initial concentration of gold salt, bacterial growth period, solution pH and temperature. The purified AuNPs exhibited significant antibacterial activity against both Gram-negative ( Escherichia coli ) and Gram-positive ( Staphylococcus aureus ) bacteria by damaging their cytoplasmic membrane. Therefore, the extreme bacterium D. radiodurans can be used as a novel bacterial candidate for efficient biosynthesis of AuNPs, which exhibited potential in biomedical application as an antibacterial agent.

Au@TiO2 yolk-shell nanostructures for enhanced performance in both photoelectric and photocatalytic solar conversion

NASA Astrophysics Data System (ADS)

He, Qinrong; Sun, Hang; Shang, Yinxing; Tang, Yanan; She, Ping; Zeng, Shan; Xu, Kongliang; Lu, Guolong; Liang, Song; Yin, Shengyan; Liu, Zhenning

2018-05-01

Solar energy conversion is an important field gaining increasing interest. Herein, bio-inspired Au@TiO2 yolk-shell nanoparticles (NPs) have been prepared via a facial one-pot hydrothermal approach. The Au@TiO2 yolk-shell NPs can self-assemble into 3D-structure to form photoelectrode for photoelectric conversion. The obtained photoelectrode demonstrates a swift and stable photocurrent of 3.5 μA/cm2, which is 4.2 and 1.6 times higher than those of the photocurrents generated by the counterparts of commercial TiO2 and Au@TiO2 core-shell NPs, respectively. Moreover, compared to the commercial TiO2 and Au@TiO2 core-shell NPs, the Au@TiO2 yolk-shell NPs also exhibit superior photocatalytic activity, delivering a H2 evolution rate of 4.92 mmol/g h. The performance improvement observed for the Au@TiO2 yolk-shell NPs is likely contributed by two synergistic factors, i.e. the incorporation of AuNPs and the unique hollow structure, which benefit the activity by simultaneously enhancing light utilization, charge separation and reaction site accessibility. The rational design and fabrication of Au@TiO2 yolk-shell NPs hold great promise for future application in efficient solar energy conversion.

Tailor-made Au@Ag core-shell nanoparticle 2D arrays on protein-coated graphene oxide with assembly enhanced antibacterial activity

NASA Astrophysics Data System (ADS)

Wang, Huiqiao; Liu, Jinbin; Wu, Xuan; Tong, Zhonghua; Deng, Zhaoxiang

2013-05-01

Water-dispersible two-dimensional (2D) assemblies of Au@Ag core-shell nanoparticles are obtained through a highly selective electroless silver deposition on pre-assembled gold nanoparticles on bovine serum albumin (BSA)-coated graphene oxide (BSA-GO). While neither BSA-GO nor AuNP-decorated BSA-GO shows any antibacterial ability, the silver-coated GO@Au nanosheets (namely GO@Au@Ag) exhibit an enhanced antibacterial activity against Gram-negative Escherichia coli (E. coli) bacteria, superior to unassembled Au@Ag nanoparticles and even ionic Ag. Such an improvement may be attributed to the increased local concentration of silver nanoparticles around a bacterium and a polyvalent interaction with the bacterial surface. In addition, the colloidal stability of this novel nano-antimicrobial against the formation of random nanoparticle aggregates guarantees a minimized activity loss of the Au@Ag nanoparticles. The antibacterial efficacy of GO@Au@Ag is less sensitive to the existence of Cl-, in comparison with silver ions, providing another advantage for wound dressing applications. Our research unambiguously reveals a strong and very specific interaction between the GO@Au@Ag nanoassembly and E. coli, which could be an important clue toward a rational design, synthesis and assembly of innovative and highly active antibacterial nanomaterials.

Theoretical study on the photocatalytic properties of graphene oxide with single Au atom adsorption

NASA Astrophysics Data System (ADS)

Ju, Lin; Dai, Ying; Wei, Wei; Li, Mengmeng; Jin, Cui; Huang, Baibiao

2018-03-01

The photocatalytic properties of graphene oxide (GO) with single Au atom adsorption are studied via the first-principles calculations based on the density functional theory. The present study addresses the origin of enhancement in photocatalytic efficiency of GO derived from single Au atom depositing. Compared with the clean one, the work function of the single Au atom adsorbed GO is lowered due to the charge transfer from Au to GO, indicating enhanced surface activity. The Au atom plays as an electron trapping center and a mediating role in charge transfer from photon excited GO to target species. The photogenerated electron-hole pairs can be separated effectively. For the GO configuration with atomic Au dispersion, there are some states introduced in the band gap, which are predominantly composed of Au 6s states. Through the in-gap state, the photo-generated electron transfer from the valence band of clean GO to the conductive band more easily. In addition, the reduction of the gap in the system is also presented in the current work, which indicates that the single Au atom adsorption improves light absorption for the GO based photocatalyst. These theoretical results are valuable for the future applications of GO materials as photocatalyst for water splitting.

Enhanced Catalytic Reduction of 4-Nitrophenol Driven by Fe3O4-Au Magnetic Nanocomposite Interface Engineering: From Facile Preparation to Recyclable Application

PubMed Central

Chen, Yue; Zhang, Yuanyuan; Kou, Qiangwei; Liu, Yang; Han, Donglai; Wang, Dandan; Sun, Yantao; Zhang, Yongjun; Wang, Yaxin; Lu, Ziyang; Chen, Lei; Yang, Jinghai; Xing, Scott Guozhong

2018-01-01

In this work, we report the enhanced catalytic reduction of 4-nitrophenol driven by Fe3O4-Au magnetic nanocomposite interface engineering. A facile solvothermal method is employed for Fe3O4 hollow microspheres and Fe3O4-Au magnetic nanocomposite synthesis via a seed deposition process. Complementary structural, chemical composition and valence state studies validate that the as-obtained samples are formed in a pure magnetite phase. A series of characterizations including conventional scanning/transmission electron microscopy (SEM/TEM), Mössbauer spectroscopy, magnetic testing and elemental mapping is conducted to unveil the structural and physical characteristics of the developed Fe3O4-Au magnetic nanocomposites. By adjusting the quantity of Au seeds coating on the polyethyleneimine-dithiocarbamates (PEI-DTC)-modified surfaces of Fe3O4 hollow microspheres, the correlation between the amount of Au seeds and the catalytic ability of Fe3O4-Au magnetic nanocomposites for 4-nitrophenol (4-NP) is investigated systematically. Importantly, bearing remarkable recyclable features, our developed Fe3O4-Au magnetic nanocomposites can be readily separated with a magnet. Such Fe3O4-Au magnetic nanocomposites shine the light on highly efficient catalysts for 4-NP reduction at the mass production level. PMID:29789457

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.

Cu(II)-Doped Polydopamine-Coated Gold Nanorods for Tumor Theranostics.

PubMed

Liu, Shuwei; Wang, Lu; Lin, Min; Wang, Dandan; Song, Ziqi; Li, Shuyao; Ge, Rui; Zhang, Xue; Liu, Yi; Li, Zhimin; Sun, Hongchen; Yang, Bai; Zhang, Hao

2017-12-27

Gold nanorods (AuNRs) are potentially useful in tumor theranostics, but the poor stability, high toxicity, and rapid removal by the immune system seriously limit their theranostic applications. In our study, we demonstrate the fabrication of Cu(II)-doped polydopamine-coated AuNR (AuNR@CuPDA), which significantly improves the potentials in tumor theranostics. Besides the improvement of physiological stability and biocompatibility, the PDA shell increases the photothermal performance and prolongs the blood circulation time of AuNRs. The half-life of AuNRs during blood circulation increases from 0.7 to 4.5 h after PDA coating, and the injected dose per gram of tumor tissue is 4.6% ID g -1 for AuNR@CuPDA. In addition to computer tomography imaging, the loading of Cu(II) in PDA shell endows AuNR@CuPDA with magnetic resonance imaging function. Cu(II) doped in PDA shell also exhibits chemotherapeutic behavior, and the tumor inhibitor rate is 31.2%. Further combining 808 nm laser-driven photothermal therapy, tumors were completely ablated, and no recurrence was observed. Liver and renal functions tests and histological analysis of major organs confirm that AuNR@CuPDA is in good safety.

Piper betle-mediated green synthesis of biocompatible gold nanoparticles

NASA Astrophysics Data System (ADS)

Punuri, Jayasekhar Babu; Sharma, Pragya; Sibyala, Saranya; Tamuli, Ranjan; Bora, Utpal

2012-08-01

Here, we report the novel use of the ethonolic leaf extract of Piper betle for gold nanoparticle (AuNP) synthesis. The successful formation of AuNPs was confirmed by UV-visible spectroscopy, and different parameters such as leaf extract concentration (2%), gold salt concentration (0.5 mM), and time (18 s) were optimized. The synthesized AuNPs were characterized with different biophysical techniques such as transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX). TEM experiments showed that nanoparticles were of various shapes and sizes ranging from 10 to 35 nm. FT-IR spectroscopy revealed that AuNPs were functionalized with biomolecules that have primary amine group -NH2, carbonyl group, -OH groups, and other stabilizing functional groups. EDX showed the presence of the elements on the surface of the AuNPs. FT-IR and EDX together confirmed the presence of biomolecules bounded on the AuNPs. Cytotoxicity of the AuNPs was tested on HeLa and MCF-7 cancer cell lines, and they were found to be nontoxic, indicating their biocompatibility. Thus, synthesized AuNPs have potential for use in various biomedical applications.

The fourth crystallographic closest packing unveiled in the gold nanocluster crystal

NASA Astrophysics Data System (ADS)

Gan, Zibao; Chen, Jishi; Wang, Juan; Wang, Chengming; Li, Man-Bo; Yao, Chuanhao; Zhuang, Shengli; Xu, An; Li, Lingling; Wu, Zhikun

2017-03-01

Metal nanoclusters have recently attracted extensive interest not only for fundamental scientific research, but also for practical applications. For fundamental scientific research, it is of major importance to explore the internal structure and crystallographic arrangement. Herein, we synthesize a gold nanocluster whose composition is determined to be Au60S6(SCH2Ph)36 by using electrospray ionization mass spectrometry and single crystal X-ray crystallography (SCXC). SCXC also reveals that Au60S6(SCH2Ph)36 consists of a fcc-like Au20 kernel protected by a pair of giant Au20S3(SCH2Ph)18 staple motifs, which contain 6 tetrahedral-coordinate μ4-S atoms not previously reported in the Au-S interface. Importantly, the fourth crystallographic closest-packed pattern, termed 6H left-handed helical (6HLH) arrangement, which results in the distinct loss of solid photoluminescence of amorphous Au60S6(SCH2Ph)36, is found in the crystals of Au60S6(SCH2Ph)36. The solvent-polarity-dependent solution photoluminescence is also demonstrated. Overall, this work provides important insights about the structure, Au-S bonding and solid photoluminescence of gold nanoclusters.

RGO/AuNR/HA-5FU nanocomposite with multi-stage release behavior and efficient antitumor activity for synergistic therapy.

PubMed

Yang, Ying; Wang, Yunlong; Zhu, Manzhou; Chen, Yan; Xiao, Yazhong; Shen, Yuhua; Xie, Anjian

2017-05-02

A reduced graphene oxide (RGO)/gold nanorod (AuNR)/hydroxyapatite (HA) nanocomposite was designed and successfully synthesized for the first time. An anticancer drug, 5-fluorouracil (5FU), was chosen as a model drug to be loaded in RGO/AuNR/HA. The fabricated RGO/AuNR/HA-5FU showed robust, selective targeting and penetrating efficiency against HeLa cells due to the good compatibility and nontoxicity of HA, and showed excellent synergetic antitumor effects through combined chemotherapy (CT) by 5FU and photothermal therapy (PTT) by both RGO and AuNRs under near-infrared (NIR) laser irradiation. More importantly, this synergistic dual therapy based on RGO/AuNR/HA can also minimize side effects in normal cells and exhibits greater antitumor activity because of a multi-stage drug release ability triggered by the pH sensitivity of HA in the first stage and the combined photothermal conversion capabilities of RGO and AuNRs by means of the NIR laser irradiation in the second stage. This study suggests that the novel RGO/AuNR/HA multi-stage drug delivery system may represent a promising potential application of multifunctional composite materials in the biomedical field.

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

Simultaneous AuIII Extraction and In Situ Formation of Polymeric Membrane-Supported Au Nanoparticles: A Sustainable Process with Application in Catalysis.

PubMed

Mora-Tamez, Lucía; Esquivel-Peña, Vicente; Ocampo, Ana L; Rodríguez de San Miguel, Eduardo; Grande, Daniel; de Gyves, Josefina

2017-04-10

A polymeric membrane-supported catalyst with immobilized gold nanoparticles (AuNPs) was prepared through the extraction and in situ reduction of Au III salts in a one-step strategy. Polymeric inclusion membranes (PIMs) and polymeric nanoporous membranes (PNMs) were tested as different membrane-support systems. Transport experiments indicated that PIMs composed of cellulose triacetate, 2-nitrophenyloctyl ether, and an aliphatic tertiary amine (Adogen 364 or Alamine 336) were the most efficient supports for Au III extraction. The simultaneous extraction and reduction processes were proven to be the result of a synergic phenomenon in which all the membrane components were involved. Scanning electron microscopy characterization of cross-sectional samples suggested a distribution of AuNPs throughout the membrane. Transmission electron microscopy characterization of the AuNPs indicated average particle sizes of 36.7 and 2.9 nm for the PIMs and PNMs, respectively. AuNPs supported on PIMs allowed for >95.4 % reduction of a 0.05 mmol L -1 4-nitrophenol aqueous solution with 10 mmol L -1 NaBH 4 solution within 25 min. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Branch number matters: Promoting catalytic reduction of 4-nitrophenol over gold nanostars by raising the number of branches and coating with mesoporous SiO2.

PubMed

Ndokoye, Pancras; Zhao, Qidong; Li, Xinyong; Li, Tingting; Tade, Moses O; Wang, Shaobin

2016-09-01

In this study, we demonstrate for the first time that highly branched gold nanostars (AuNSs) and silica-coated AuNSs (AuNSs@mSiO2) could potentially serve as efficient hydrogenation catalysts. The catalytic activity could be promoted by raising the number of tipped-branches of AuNSs, which reveals that the tips play an important role as active sites. The fabricated sharply-pointed AuNSs benefit the electron transfer from BH4 anions to 4-nitrophenol. Coating AuNSs with mesoporous silica (AuNSs@mSiO2) further enhanced the reduction rate and recyclability, and also contributed to reducing the induction period. The AuNSs@mSiO2 (50-100nm in diameter) are large enough to be catalytically inactive, but they consist of sharply-pointed tips with the radius of 2.6-3.6nm, which are rich in coordinately unsaturated sites similar to those of nanoparticles and clusters. Such features in structure and activity would also extend their application range in heterogeneous catalysis. Copyright © 2016 Elsevier Inc. All rights reserved.

High quality gold nanorods and nanospheres for surface-enhanced Raman scattering detection of 2,4-dichlorophenoxyacetic acid

NASA Astrophysics Data System (ADS)

Jia, Jin-Liang; Xu, Han-Hong; Zhang, Gui-Rong; Hu, Zhun; Xu, Bo-Qing

2012-12-01

Nearly monodisperse Au nanorods (NRs) with different aspect ratios were separated from home-synthesized polydisperse samples using a gradient centrifugation method. The morphology, size and its distribution, and photo-absorption property were analyzed by transmission electron microscopy, atomic force microscopy and UV-visible spectroscopy. Subsequently, using colloidal Au NRs (36.2 nm ×10.7 nm) with 97.4% yield after centrifugation and Au nanospheres (NSs) (22.9 ± 1.0 nm in diameter) with 97.6% yield as Au substrates, surface-enhanced Raman scattering (SERS) spectra of 2,4-dichlorophenoxyacetic acid (2,4-D) were recorded using laser excitation at 632.8 nm. Results show that surface enhancement factors (EF) for Au NRs and NSs are 6.2 × 105 and 5.7 × 104 using 1.0 × 10-6 M 2,4-D, respectively, illustrating that EF value is a factor of ˜10 greater for Au NRs substrates than for Au NSs substrates. As a result, large EF are a mainly result of chemical enhancement mechanisms. Thus, it is expected that Au NPs can find a comprehensive SERS application in the trace detection of pesticide residues.

High quality gold nanorods and nanospheres for surface-enhanced Raman scattering detection of 2,4-dichlorophenoxyacetic acid.

PubMed

Jia, Jin-Liang; Xu, Han-Hong; Zhang, Gui-Rong; Hu, Zhun; Xu, Bo-Qing

2012-12-14

Nearly monodisperse Au nanorods (NRs) with different aspect ratios were separated from home-synthesized polydisperse samples using a gradient centrifugation method. The morphology, size and its distribution, and photo-absorption property were analyzed by transmission electron microscopy, atomic force microscopy and UV-visible spectroscopy. Subsequently, using colloidal Au NRs (36.2 nm ×10.7 nm) with 97.4% yield after centrifugation and Au nanospheres (NSs) (22.9 ± 1.0 nm in diameter) with 97.6% yield as Au substrates, surface-enhanced Raman scattering (SERS) spectra of 2,4-dichlorophenoxyacetic acid (2,4-D) were recorded using laser excitation at 632.8 nm. Results show that surface enhancement factors (EF) for Au NRs and NSs are 6.2 × 10(5) and 5.7 × 10(4) using 1.0 × 10(-6) M 2,4-D, respectively, illustrating that EF value is a factor of ~10 greater for Au NRs substrates than for Au NSs substrates. As a result, large EF are a mainly result of chemical enhancement mechanisms. Thus, it is expected that Au NPs can find a comprehensive SERS application in the trace detection of pesticide residues.

Au 133 (SPh - t Bu) 52 Nanomolecules: X-ray Crystallography, Optical, Electrochemical, and Theoretical Analysis

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

Dass, Amala; Theivendran, Shevanuja; Nimmala, Praneeth Reddy

2015-04-15

Crystal structure determination has revolutionized modern science in biology, chemistry, and physics. However, the difficulty in obtaining periodic crystal lattices which are needed for X-ray crystal analysis has hindered the determination of atomic structure in nanomaterials, known as the "nanostructure problem". Here, by using rigid and bulky ligands, we have overcome this limitation and successfully solved the X-ray crystallographic structure of the largest reported thiolated gold nanomolecule, Au133S52. The total composition, Au-133(SPh-tBu)(52), was verified using high resolution electrospray ionization mass spectrometry (ESI-MS). The experimental and simulated optical spectra show an emergent surface plasmon resonance that is more pronounced than inmore » the slightly larger Au-144(SCH2CH2Ph)(60). Theoretical analysis indicates that the presence of rigid and bulky ligands is the key to the successful crystal formation.« less

Au133(SPh-tBu)52 nanomolecules: X-ray crystallography, optical, electrochemical, and theoretical analysis.

PubMed

Dass, Amala; Theivendran, Shevanuja; Nimmala, Praneeth Reddy; Kumara, Chanaka; Jupally, Vijay Reddy; Fortunelli, Alessandro; Sementa, Luca; Barcaro, Giovanni; Zuo, Xiaobing; Noll, Bruce C

2015-04-15

Crystal structure determination has revolutionized modern science in biology, chemistry, and physics. However, the difficulty in obtaining periodic crystal lattices which are needed for X-ray crystal analysis has hindered the determination of atomic structure in nanomaterials, known as the "nanostructure problem". Here, by using rigid and bulky ligands, we have overcome this limitation and successfully solved the X-ray crystallographic structure of the largest reported thiolated gold nanomolecule, Au133S52. The total composition, Au133(SPh-tBu)52, was verified using high resolution electrospray ionization mass spectrometry (ESI-MS). The experimental and simulated optical spectra show an emergent surface plasmon resonance that is more pronounced than in the slightly larger Au144(SCH2CH2Ph)60. Theoretical analysis indicates that the presence of rigid and bulky ligands is the key to the successful crystal formation.

Green chemistry approach for the synthesis and stabilization of biocompatible gold nanoparticles and their potential applications in cancer therapy

NASA Astrophysics Data System (ADS)

Mukherjee, Sudip; Sushma, V.; Patra, Sujata; Barui, Ayan Kumar; Pal Bhadra, Manika; Sreedhar, Bojja; Ranjan Patra, Chitta

2012-11-01

The biological approach to synthesis of AuNPs is eco-friendly and an ideal method to develop environmentally sustainable nanoparticles alternative to existing methods. We have developed a simple, fast, clean, efficient, low-cost and eco-friendly single-step green chemistry approach for the synthesis of biocompatible gold nanoparticles (AuNPs) from chloroauric acid (HAuCl4) using a water extract of Eclipta Alba leaves at room temperature. The AuNPs using Eclipta extract have been formed in very short time, even in less than 10 min. The as-synthesized AuNPs were thoroughly characterized by several physico-chemical techniques. The in vitro stability of as-synthesized AuNPs was studied in different buffer solutions. A plausible mechanism for the synthesis of AuNPs by Eclipta extract has been discussed. The biocompatibility of AuNPs was observed by in vitro cell culture assays. Finally, we have designed and developed a AuNPs-based drug delivery system (DDS) (Au-DOX) containing doxorubicin (DOX), a FDA approved anticancer drug. Administration of this DDS to breast cancer cells (MCF-7 and MDA-MB-231) shows significant inhibition of breast cancer cell proliferation compared to pristine doxorubicin. Therefore we strongly believe that the use of Eclipta Alba offers large-scale production of biocompatible AuNPs that can be used as a delivery vehicle for the treatment of cancer diseases.

Improvement of mimetic peroxidase activity of gold nanoclusters on the luminol chemiluminescence reaction by surface modification with ethanediamine.

PubMed

Han, Lu; Li, Ying; Fan, Aiping

2018-06-01

Peroxidase is a commonly used catalyst in luminol-H 2 O 2 chemiluminescence (CL) reactions. Natural peroxidase has a sophisticated separation process, short shelf life and unstable activity, therefore it is important to develop peroxidases that have both high catalytic activity and good stability as alternatives to the natural enzyme. Gold nanoclusters (Au NCs) are an alternative peroxidase with catalytic activity in the luminol-H 2 O 2 CL reaction. In the present study, ethanediamine was modified on the surface of Au NCs forming cationic Au NCs. The zeta potential of the cationic Au NCs maintained its positive charge when the pH of the solution was between 4 and 9. The cationic Au NCs showed higher catalytic activity in the luminol-H 2 O 2 CL reaction than did unmodified Au NCs. A mechanism study showed that the better performance of cationic Au NCs may be attributed to the generation of 1 O 2 on the surface of cationic Au NCs and a positive surface charge, for better affinity to luminol. Cationic Au NC, acting as a peroxidase mimic, has much better stability than horseradish peroxidase over a wide range of temperatures. We believe that cationic Au NCs may be useful as an artificial peroxidase for a wide range of potential applications in CL and bioanalysis. Copyright © 2018 John Wiley & Sons, Ltd.

Electromagnetic resonance modes on a two-dimensional tandem grating and its application for broadband absorption in the visible spectrum.

PubMed

Han, Sunwoo; Lee, Bong Jae

2016-01-25

In this work, we numerically investigate the electromagnetic resonances on two-dimensional tandem grating structures. The base of a tandem grating consists of an opaque Au substrate, a SiO(2) spacer, and a Au grating (concave type); that is, a well-known fishnet structure forming Au/SiO(2)/Au stack. A convex-type Au grating (i.e., topmost grating) is then attached on top of the base fishnet structure with or without additional SiO(2) spacer, resulting in two types of tandem grating structures. In order to calculate the spectral reflectance and local magnetic field distribution, the finite-difference time-domain method is employed. When the topmost Au grating is directly added onto the base fishnet structure, the surface plasmon and magnetic polariton in the base structure are branched out due to the geometric asymmetry with respect to the SiO(2) spacer. If additional SiO(2) spacer is added between the topmost Au grating and the base fishnet structure, new magnetic resonance modes appear due to coupling between two vertically aligned Au/SiO(2)/Au stacks. With the understanding of multiple electromagnetic resonance modes on the proposed tandem grating structures, we successfully design a broadband absorber made of Au and SiO(2) in the visible spectrum.

Microbial synthesis of core/shell gold/palladium nanoparticles for applications in green chemistry

PubMed Central

Deplanche, Kevin; Merroun, Mohamed L.; Casadesus, Merixtell; Tran, Dung T.; Mikheenko, Iryna P.; Bennett, James A.; Zhu, Ju; Jones, Ian P.; Attard, Gary A.; Wood, J.; Selenska-Pobell, Sonja; Macaskie, Lynne E.

2012-01-01

We report a novel biochemical method based on the sacrificial hydrogen strategy to synthesize bimetallic gold (Au)–palladium (Pd) nanoparticles (NPs) with a core/shell configuration. The ability of Escherichia coli cells supplied with H2 as electron donor to rapidly precipitate Pd(II) ions from solution is used to promote the reduction of soluble Au(III). Pre-coating cells with Pd(0) (bioPd) dramatically accelerated Au(III) reduction, with the Au(III) reduction rate being dependent upon the initial Pd loading by mass on the cells. Following Au(III) addition, the bioPd–Au(III) mixture rapidly turned purple, indicating the formation of colloidal gold. Mapping of bio-NPs by energy dispersive X-ray microanalysis suggested Au-dense core regions and peripheral Pd but only Au was detected by X-ray diffraction (XRD) analysis. However, surface analysis of cleaned NPs by cyclic voltammetry revealed large Pd surface sites, suggesting, since XRD shows no crystalline Pd component, that layers of Pd atoms surround Au NPs. Characterization of the bimetallic particles using X-ray absorption spectroscopy confirmed the existence of Au-rich core and Pd-rich shell type bimetallic biogenic NPs. These showed comparable catalytic activity to chemical counterparts with respect to the oxidation of benzyl alcohol, in air, and at a low temperature (90°C). PMID:22399790

The study on the extraction and recovery of Au from scrap of the used computer using chloride solvent

NASA Astrophysics Data System (ADS)

Oh, Su-ji; Choi, Eunju; Choi, Nagchoul; Park, Cheonyoung

2013-04-01

Recently, due to the realization of environmental problems of cyanide, it is a worldwide quest to find viable alternatives. One of the alternatives is a chloride solvent(chlorine-hypochlorite acid) with an appropriate oxidizing agent. The rate of dissolution of Au by chloride solvent is much faster than that by cyanide. Also, due to presence of chloride ions, there is no passivation of gold surfaces during chlorination. The objective of this work was to investigate the effect of Au extraction efficiency under various experimental conditions(pulp density, chlorine-hypochlorite ratio and concentration of NaCl) from scrap of the used computer by chloride solvent. In addition, the recovery experiment was conducted to examine of the precipitation efficiency of Au under various metabisulfite concentration from extracted solution. In an EDS analysis, valuable metals such as Cu, Sn, Sb, Al, Ni, Pb and Au were observed in scrap of the used computer. The result of extraction experiment showed that the highest extraction rate was obtained under 1% of pulp density with a chlorine-hypochlorite ratio of 2:1, and a concentration of NaCl at 2M. The highest Au recovery(precipitation) rate was observed the addition of sodium metabisulfite at 2M concentration. Under these conditions, chlorine-hypochlorite could effectively Au extraction from scrap of the used computer sections and the additive reagent using sodium metabisulfite could easily precipitate the Au from the chlorine-hypochlorite solution.

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.

Ultrafast Relaxation Dynamics of Au 38 (SC 2 H 4 Ph) 24 Nanoclusters and Effects of Structural Isomerism

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

Zhou, Meng; Tian, Shubo; Zeng, Chenjie

Structural isomerism in nanoparticles has recently emerged as a new topic and stimulated research interest because the atomic structures of ultrasmall nanoparticles may have great impact on their fundamental properties and applications. We report the correlation between ultrafast relaxation dynamics and atomic structures of two isomers of thiolate-protected Au 38(SC 2H 4Ph) 24. The bi-icosahedral Au 38 (denoted as Au 38Q) with a Au 23 inner core in its atomic structure shows rapid decay (1.5 ps) followed by nanosecond relaxation to the ground state, whereas its structural isomer (Au 38T) exhibits similar relaxation processes, but the rapid decay is acceleratedmore » by ~50% (1.0 ps). The picosecond relaxations in both cases can be assigned to core–shell charge transfer or electronic rearrangement within the metal core. The acceleration of the fast decay in Au38T is ascribed to its unique core structure, which is made up of a mono-icosahedral Au 13 capped by a Au 12 tri-tetrahedron by sharing two atoms. Interestingly, coherent phonon emissions (25 cm –1 for Au 38Q, 27 and 60 cm –1 for Au 38T) are observed in both isomers with pumping in the NIR region. These results illustrate for the first time the importance of atomic structures in the photophysics of same sized gold nanoclusters.« less

Factors Influencing the Stability of Au-Incorporated Metal-Oxide Supported Thin Films for Optical Gas Sensing

DOE PAGES

Baltrus, John P.; Holcomb, Gordon R.; Tylczak, Joseph H.; ...

2017-02-24

There is interest in using Au-nanoparticle incorporated oxide films as functional sensor layers for high-temperature applications in optical-based sensors for measurements in both highly-oxidizing and highly-reducing atmospheres at temperatures approaching 900°C-1000°C because of a relatively high melting temperature combined with the inert nature of Au nanoparticles. This study includes a systematic series of experiments and theoretical calculations targeted at further understanding stability of Au-nanoparticle incorporated TiO 2 films as archetype sensing materials. A combination of thermodynamic modeling and long-term exposure tests were utilized to unambiguously determine that gas stream composition-dependent reactive evaporation of Au (to form predominately Au(g) or AuH(g),more » depending upon the environment) at the surface of the nanoparticles is the dominant mechanism for mass loss of Au. Primary factors dictating the rate of reactive evaporation, and hence the associated film stability, were determined to be the gas stream temperature and the concentration of H 2, with the former playing a more significant role over the ranges of temperatures (700°C - 800°C) and H 2 concentrations (1% to 29% H 2 by volume) explored. The mitigation of Au-mass loss through reactive evaporation was also successfully demonstrated by depositing a SiO 2 overlayer on the Au-nanoparticle embedded films to prevent direct Au-nanoparticle/vapor-phase contact.« less

Ultrafast Relaxation Dynamics of Au 38 (SC 2 H 4 Ph) 24 Nanoclusters and Effects of Structural Isomerism

DOE PAGES

Zhou, Meng; Tian, Shubo; Zeng, Chenjie; ...

2016-12-22

Structural isomerism in nanoparticles has recently emerged as a new topic and stimulated research interest because the atomic structures of ultrasmall nanoparticles may have great impact on their fundamental properties and applications. We report the correlation between ultrafast relaxation dynamics and atomic structures of two isomers of thiolate-protected Au 38(SC 2H 4Ph) 24. The bi-icosahedral Au 38 (denoted as Au 38Q) with a Au 23 inner core in its atomic structure shows rapid decay (1.5 ps) followed by nanosecond relaxation to the ground state, whereas its structural isomer (Au 38T) exhibits similar relaxation processes, but the rapid decay is acceleratedmore » by ~50% (1.0 ps). The picosecond relaxations in both cases can be assigned to core–shell charge transfer or electronic rearrangement within the metal core. The acceleration of the fast decay in Au38T is ascribed to its unique core structure, which is made up of a mono-icosahedral Au 13 capped by a Au 12 tri-tetrahedron by sharing two atoms. Interestingly, coherent phonon emissions (25 cm –1 for Au 38Q, 27 and 60 cm –1 for Au 38T) are observed in both isomers with pumping in the NIR region. These results illustrate for the first time the importance of atomic structures in the photophysics of same sized gold nanoclusters.« less

In-depth evolution of chemical states and sub-10-nm-resolution crystal orientation mapping of nanograins in Ti(5 nm)/Au(20 nm)/Cr(3 nm) tri-layer thin films

NASA Astrophysics Data System (ADS)

Zhu, Xiaoli; Todeschini, Matteo; Bastos da Silva Fanta, Alice; Liu, Lintao; Jensen, Flemming; Hübner, Jörg; Jansen, Henri; Han, Anpan; Shi, Peixiong; Ming, Anjie; Xie, Changqing

2018-09-01

The applications of Au thin films and their adhesion layers often suffer from a lack of sufficient information about the chemical states of adhesion layers and about the high-lateral-resolution crystallographic morphology of Au nanograins. Here, we demonstrate the in-depth evolution of the chemical states of adhesive layers at the interfaces and the crystal orientation mapping of gold nanograins with a lateral resolution of less than 10 nm in a Ti/Au/Cr tri-layer thin film system. Using transmission electron microscopy, the variation in the interdiffusion at Cr/Au and Ti/Au interfaces was confirmed. From X-ray photoelectron spectroscopy (XPS) depth profiling, the chemical states of Cr, Au and Ti were characterized layer by layer, suggesting the insufficient oxidation of the adhesive layers. At the interfaces the Au 4f peaks shift to higher binding energies and this behavior can be described by a proposed model based on electron reorganization and substrate-induced final-state neutralization in small Au clusters supported by the partially oxidized Ti layer. Utilizing transmission Kikuchi diffraction (TKD) in a scanning electron microscope, the crystal orientation of Au nanograins between two adhesion layers was non-destructively characterized with sub-10 nm spatial resolution. The results provide nanoscale insights into the Ti/Au/Cr thin film system and contribute to our understanding of its behavior in nano-optic and nano-electronic devices.

Factors Influencing the Stability of Au-Incorporated Metal-Oxide Supported Thin Films for Optical Gas Sensing

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

Baltrus, John P.; Holcomb, Gordon R.; Tylczak, Joseph H.

There is interest in using Au-nanoparticle incorporated oxide films as functional sensor layers for high-temperature applications in optical-based sensors for measurements in both highly-oxidizing and highly-reducing atmospheres at temperatures approaching 900°C-1000°C because of a relatively high melting temperature combined with the inert nature of Au nanoparticles. This study includes a systematic series of experiments and theoretical calculations targeted at further understanding stability of Au-nanoparticle incorporated TiO 2 films as archetype sensing materials. A combination of thermodynamic modeling and long-term exposure tests were utilized to unambiguously determine that gas stream composition-dependent reactive evaporation of Au (to form predominately Au(g) or AuH(g),more » depending upon the environment) at the surface of the nanoparticles is the dominant mechanism for mass loss of Au. Primary factors dictating the rate of reactive evaporation, and hence the associated film stability, were determined to be the gas stream temperature and the concentration of H 2, with the former playing a more significant role over the ranges of temperatures (700°C - 800°C) and H 2 concentrations (1% to 29% H 2 by volume) explored. The mitigation of Au-mass loss through reactive evaporation was also successfully demonstrated by depositing a SiO 2 overlayer on the Au-nanoparticle embedded films to prevent direct Au-nanoparticle/vapor-phase contact.« less

Gold(I) NHC-based homo- and heterobimetallic complexes: synthesis, characterization and evaluation as potential anticancer agents.

PubMed

Bertrand, Benoît; Citta, Anna; Franken, Inge L; Picquet, Michel; Folda, Alessandra; Scalcon, Valeria; Rigobello, Maria Pia; Le Gendre, Pierre; Casini, Angela; Bodio, Ewen

2015-09-01

While N-heterocyclic carbenes (NHC) are ubiquitous ligands in catalysis for organic or industrial syntheses, their potential to form transition metal complexes for medicinal applications has still to be exploited. Within this frame, we synthesized new homo- and heterobimetallic complexes based on the Au(I)-NHC scaffold. The compounds were synthesized via a microwave-assisted method developed in our laboratories using Au(I)-NHC complexes carrying a pentafluorophenol ester moiety and another Au(I) phosphane complex or a bipyridine ligand bearing a pendant amine function. Thus, we developed two different methods to prepare homo- and heterobimetallic complexes (Au(I)/Au(I) or Au(I)/Cu(II), Au(I)/Ru(II), respectively). All the compounds were fully characterized by several spectroscopic techniques including far infrared, and were tested for their antiproliferative effects in a series of human cancer cells. They showed moderate anticancer properties. Their toxic effects were also studied ex vivo using the precision-cut tissue slices (PCTS) technique and initial results concerning their reactivity with the seleno-enzyme thioredoxin reductase were obtained.

Long-term antibacterial characteristics and cytocompatibility of titania nanotubes loaded with Au nanoparticles without photocatalytic effects

NASA Astrophysics Data System (ADS)

Wang, Guomin; Feng, Hongqing; Jin, Weihong; Gao, Ang; Peng, Xiang; Li, Wan; Wu, Hao; Li, Zhou; Chu, Paul K.

2017-08-01

Au nanoparticles (NPs) can endow titania nanotubes (Au@TiO2-NT) with light-independent antibacterial properties which bode well for in vivo application because of the dark environment inside tissues. In this work, the long-term antibacterial bactericidal properties and cytocompatibility of Au@TiO2-NT without photocatalytic effects are studied in details. The materials exhibit antibacterial effects against Staphylococcus aureus according to antibacterial tests carried out for a total time of 21 days, which are normally long enough for early stage tissue healing after surgery. In addition, adhesion and proliferation of MC3T3-E1 osteoblasts on Au@TiO2-NT reveal cytocompatibility comparable to that of TiO2-NT. No reactive oxygen species (ROS) are detected from either the bacteria or MC3T3-E1 cells cultured on the Au@TiO2-NT surface. The absence of ROS, long-term antibacterial properties, and cytocompatibility make Au@TiO2-NT promising biomaterials in orthopedic devices and implants.

Construction of CuS/Au Heterostructure through a Simple Photoreduction Route for Enhanced Electrochemical Hydrogen Evolution and Photocatalysis

NASA Astrophysics Data System (ADS)

Basu, Mrinmoyee; Nazir, Roshan; Fageria, Pragati; Pande, Surojit

2016-10-01

An efficient Hydrogen evolution catalyst has been developed by decorating Au nanoparticle on the surface of CuS nanostructure following a green and environmental friendly approach. CuS nanostructure is synthesized through a simple wet-chemical route. CuS being a visible light photocatalyst is introduced to function as an efficient reducing agent. Photogenerated electron is used to reduce Au(III) on the surface of CuS to prepare CuS/Au heterostructure. The as-obtained heterostructure shows excellent performance in electrochemical H2 evolution reaction with promising durability in acidic condition, which could work as an efficient alternative for novel metals. The most efficient CuS-Au heterostructure can generate 10 mA/cm2 current density upon application of 0.179 V vs. RHE. CuS-Au heterostructure can also perform as an efficient photocatalyst for the degradation of organic pollutant. This dual nature of CuS and CuS/Au both in electrocatalysis and photocatalysis has been unveiled in this study.

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.

Efficient Energy Transfer from Near-Infrared Emitting Gold Nanoparticles to Pendant Ytterbium(III).

PubMed

Crawford, Scott E; Andolina, Christopher M; Kaseman, Derrick C; Ryoo, Bo Hyung; Smith, Ashley M; Johnston, Kathryn A; Millstone, Jill E

2017-12-13

Here, we demonstrate efficient energy transfer from near-infrared-emitting ortho-mercaptobenzoic acid-capped gold nanoparticles (AuNPs) to pendant ytterbium(III) cations. These functional materials combine the high molar absorptivity (1.21 × 10 6 M -1 cm -1 ) and broad excitation features (throughout the UV and visible regions) of AuNPs with the narrow emissive properties of lanthanides. Interaction between the AuNP ligand shell and ytterbium is determined using both nuclear magnetic resonance and electron microscopy measurements. In order to identify the mechanism of this energy transfer process, the distance of the ytterbium(III) from the surface of the AuNPs is systematically modulated by changing the size of the ligand appended to the AuNP. By studying the energy transfer efficiency from the various AuNP conjugates to pendant ytterbium(III) cations, a Dexter-type energy transfer mechanism is suggested, which is an important consideration for applications ranging from catalysis to energy harvesting. Taken together, these experiments lay a foundation for the incorporation of emissive AuNPs in energy transfer systems.

Construction of CuS/Au Heterostructure through a Simple Photoreduction Route for Enhanced Electrochemical Hydrogen Evolution and Photocatalysis

PubMed Central

Basu, Mrinmoyee; Nazir, Roshan; Fageria, Pragati; Pande, Surojit

2016-01-01

An efficient Hydrogen evolution catalyst has been developed by decorating Au nanoparticle on the surface of CuS nanostructure following a green and environmental friendly approach. CuS nanostructure is synthesized through a simple wet-chemical route. CuS being a visible light photocatalyst is introduced to function as an efficient reducing agent. Photogenerated electron is used to reduce Au(III) on the surface of CuS to prepare CuS/Au heterostructure. The as-obtained heterostructure shows excellent performance in electrochemical H2 evolution reaction with promising durability in acidic condition, which could work as an efficient alternative for novel metals. The most efficient CuS-Au heterostructure can generate 10 mA/cm2 current density upon application of 0.179 V vs. RHE. CuS-Au heterostructure can also perform as an efficient photocatalyst for the degradation of organic pollutant. This dual nature of CuS and CuS/Au both in electrocatalysis and photocatalysis has been unveiled in this study. PMID:27703212

An assessment of nitrogen-based manure application rates on 39 U.S. swine operations.

PubMed

Lory, John A; Massey, Raymond E; Zulovich, Joseph M; Hoehne, John A; Schmidt, Amy M; Carlson, Marcia S; Fulhage, Charles D

2004-01-01

Water quality concerns and revised regulations are changing how confined animal feeding operations manage manure. Devising acceptable and feasible changes in manure practices requires a full understanding of the forces shaping current manure management decisions. Previous theoretical models have shown that a wide range of factors influence the lowest cost solution for manure management. We used a mechanistic model to characterize the manure management practices on 39 swine operations (20 unagitated lagoon and 19 slurry operations) in five states (Iowa, Missouri, North Carolina, Oklahoma, and Pennsylvania). Information was collected from each operation about animal numbers, feed and water use, manure handling and storage characteristics, field locations, crop rotation, fertilizer need, and equipment inventory and usage. Collected data were used as input and to validate results from a mechanistic model that determined acres required for manure application, manure application rate, time required for manure application, value of manure, and costs of manure management. The 39 farms had a mean of 984 animal units (AU) per operation, 18.2 AU ha(-1) (7.4 AU acre(-1)), and manure application costs of dollar 10.49 AU(-1) yr(-1). Significant factors affecting manure management included operation size, manure handling system, state, and ownership structure. Larger operations had lower manure management costs (r2 = 0.32). Manure value potentially exceeded manure application costs on 58% of slurry and 15% of lagoon operations. But 38% of slurry operations needed to apply manure off the farm whereas all lagoon operations had sufficient land for N-based manure management. Manure management was a higher percentage of gross income on contract operations compared with independents (P < 0.01). This research emphasized the importance of site-specific factors affecting manure management decisions and the economics of U.S. swine operations.

Direct electrochemical oxidation of S-captopril using gold electrodes modified with graphene-AuAg nanocomposites

PubMed Central

Pogacean, Florina; Biris, Alexandru R; Coros, Maria; Lazar, Mihaela Diana; Watanabe, Fumiya; Kannarpady, Ganesh K; Al Said, Said A Farha; Biris, Alexandru S; Pruneanu, Stela

2014-01-01

In this paper, we present a novel approach for the electrochemical detection of S-captopril based on graphene AuAg nanostructures used to modify an Au electrode. Multi-layer graphene (Gr) sheets decorated with embedded bimetallic AuAg nanoparticles were successfully synthesized catalytically with methane as the carbon source. The two catalytic systems contained 1.0 wt% Ag and 1.0 wt% Au, while the second had a larger concentration of metals (1.5 wt% Ag and 1.5 wt% Au) and was used for the synthesis of the Gr-AuAg-1 and Gr-AuAg-1.5 multicomponent samples. High-resolution transmission electron microscopy analysis indicated the presence of graphene flakes that had regular shapes (square or rectangular) and dimensions in the tens to hundreds of nanometers. We found that the size of the embedded AuAg nanoparticles varied between 5 and 100 nm, with the majority being smaller than 20 nm. Advanced scanning transmission electron microscopy studies indicated a bimetallic characteristic of the metallic clusters. The resulting Gr-AuAg-1 and Gr-AuAg-1.5 samples were used to modify the surface of commonly used Au substrates and subsequently employed for the direct electrochemical oxidation of S-captopril. By comparing the differential pulse voltammograms recorded with the two modified electrodes at various concentrations of captopril, the peak current was determined to be well-defined, even at relatively low concentration (10−5 M), for the Au/Gr-AuAg-1.5 electrode. In contrast, the signals recorded with the Au/Gr-AuAg-1 electrode were poorly defined within a 5×10−6 to 5×10−3 M concentration range, and many of them overlapped with the background. Such composite materials could find significant applications in nanotechnology, sensing, or nanomedicine. PMID:24596464

Dynamic imaging of a single gold nanoparticle in liquid irradiated by off-resonance femtosecond laser

NASA Astrophysics Data System (ADS)

Boutopoulos, Christos; Hatef, Ali; Fortin-Deschênes, Matthieu; Meunier, Michel

2015-07-01

Plasmonic nanoparticles can lead to extreme confinement of the light in the near field. This unique ability of plasmonic nanoparticles can be used to generate nanobubbles in liquid. In this work, we demonstrate with single-particle monitoring that 100 nm gold nanoparticles (AuNPs) irradiated by off-resonance femtosecond (fs) laser in the tissue therapeutic optical window (λ = 800 nm), can act as a durable nanolenses in liquid and provoke nanocavitation while remaining intact. We have employed combined ultrafast shadowgraphic imaging, in situ dark field imaging and dynamic tracking of AuNP Brownian motion to ensure the study of individual AuNPs/nanolenses under multiple fs laser pulses. We demonstrate that 100 nm AuNPs can generate multiple, highly confined (radius down to 550 nm) and transient (life time < 50 ns) nanobubbles. The latter is of significant importance for future development of in vivo AuNP-assisted laser nanosurgery and theranostic applications, where AuNP fragmentation should be avoided to prevent side effects, such as cytotoxicity and immune system's response. The experimental results have been correlated with theoretical modeling to provide an insight to the AuNP-safe cavitation mechanism as well as to investigate the deformation mechanism of the AuNPs at high laser fluences.Plasmonic nanoparticles can lead to extreme confinement of the light in the near field. This unique ability of plasmonic nanoparticles can be used to generate nanobubbles in liquid. In this work, we demonstrate with single-particle monitoring that 100 nm gold nanoparticles (AuNPs) irradiated by off-resonance femtosecond (fs) laser in the tissue therapeutic optical window (λ = 800 nm), can act as a durable nanolenses in liquid and provoke nanocavitation while remaining intact. We have employed combined ultrafast shadowgraphic imaging, in situ dark field imaging and dynamic tracking of AuNP Brownian motion to ensure the study of individual AuNPs/nanolenses under multiple fs laser pulses. We demonstrate that 100 nm AuNPs can generate multiple, highly confined (radius down to 550 nm) and transient (life time < 50 ns) nanobubbles. The latter is of significant importance for future development of in vivo AuNP-assisted laser nanosurgery and theranostic applications, where AuNP fragmentation should be avoided to prevent side effects, such as cytotoxicity and immune system's response. The experimental results have been correlated with theoretical modeling to provide an insight to the AuNP-safe cavitation mechanism as well as to investigate the deformation mechanism of the AuNPs at high laser fluences. Electronic supplementary information (ESI) available: The ESI video 1 shows successive transient bubbles generated by fs laser excitation of a dynamic pair of AuNP at Fpeak = 200 mJ cm-2. Both the camera frame rate and the fs laser repetition rate where synchronized at 10 Hz. The pump-prop delay was set to 10 ns. The ESI video 2 shows the complete dynamic evolution of a transient nanobubble generated around a single AuNP/nanolens, following fs laser excitation at Fpeak = 200 mJ cm-2. See DOI: 10.1039/C5NR02721G

Cytotoxicity, intracellular localization and exocytosis of citrate capped and PEG functionalized gold nanoparticles in human hepatocyte and kidney cells.

PubMed

Tlotleng, Nonhlanhla; Vetten, Melissa A; Keter, Frankline K; Skepu, Amanda; Tshikhudo, Robert; Gulumian, Mary

2016-08-01

Surface-modified gold nanoparticles (AuNPs) are nanomaterials that hold promise in drug delivery applications. In this study, the cytotoxicity, uptake, intracellular localization, and the exocytosis of citrate-stabilized (Cit-AuNP) and polyethylene glycol (PEG)-modified gold nanoparticles with the carboxyl (COOH) terminal functional group were assessed in human embryonic kidney (HEK 293) and the human caucasian hepatocytes carcinoma (Hep G2) cell systems, representing two major accumulation sites for AuNPs. The zeta (ζ)-potential measurements confirmed the negative surface charge of the AuNPs in water and in cell growth medium. The transmission electron microscopy confirmed the size and morphology of the AuNPs. Both types of AuNPs were shown to induce cytotoxic effects in cells. The Hep G2 cells were more sensitive cell type, with the COOH-PEG-AuNPs inducing the highest toxicity at higher concentrations. Dark field microscopy and TEM images revealed that the AuNPs were internalized in cells, mostly as agglomerates. TEM micrographs further revealed that the AuNPs were confined as agglomerates inside vesicle-like compartments, likely to be endosomal and lysosomal structures as well as in the cytosol, mostly as individual particles. The AuNPs were shown to remain in cellular compartments for up to 3 weeks, but thereafter, clearance of the gold nanoparticles from the cells by exocytosis was evident. The results presented in this study may therefore give an indication on the fate of AuNPs on long-term exposure to cells and may also assist in safety evaluation of AuNPs.

Eco-friendly synthesis of TiO2, Au and Pt doped TiO2 nanoparticles for dye sensitized solar cell applications and evaluation of toxicity

NASA Astrophysics Data System (ADS)

Gopinath, K.; Kumaraguru, S.; Bhakyaraj, K.; Thirumal, S.; Arumugam, A.

2016-04-01

Driven by the demand of pure TiO2, Au and Pt doped TiO2 NPs were successfully synthesized using Terminalia arjuna bark extract. The eco-friendly synthesized NPs were characterized by UV-Vis-DRS, ATR-FT-IR, PL, XRD, Raman, SEM with EDX and TEM analysis. The synthesized NPs were investigation for dye sensitized solar cell applications. UV-Vis-Diffused Reflectance Spectra clearly showed that the expected TiO2 inter band absorption below 306 nm, incorporation of gold shows surface plasma resonant (SPR) near 555 nm and platinum incorporated TiO2 NPs shows absorbance at 460 nm. The energy conversion efficiency for Au doped TiO2 NPs when compared to pure and Pt doped TiO2 NPs. In addition to that, Au noble metal present TiO2 matrix and an improve open-circuit voltage (Voc) of DSSC. Synthesized NPs was evaluated into antibacterial and antifungal activities by disk diffusion method. It is observed that NPs have not shown any activities in all tested bacterial and fungal strains. In this eco-friendly synthesis method to provide non toxic and environmental friendly nanomaterials can be used for solar energy device application.

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.

Surface-confined fluorescence enhancement of Au nanoclusters anchoring to a two-dimensional ultrathin nanosheet toward bioimaging

NASA Astrophysics Data System (ADS)

Tian, Rui; Yan, Dongpeng; Li, Chunyang; Xu, Simin; Liang, Ruizheng; Guo, Lingyan; Wei, Min; Evans, David G.; Duan, Xue

2016-05-01

Gold nanoclusters (Au NCs) as ultrasmall fluorescent nanomaterials possess discrete electronic energy and unique physicochemical properties, but suffer from relatively low quantum yield (QY) which severely affects their application in displays and imaging. To solve this conundrum and obtain highly-efficient fluorescent emission, 2D exfoliated layered double hydroxide (ELDH) nanosheets were employed to localize Au NCs with a density as high as 5.44 × 1013 cm-2, by virtue of the surface confinement effect of ELDH. Both experimental studies and computational simulations testify that the excited electrons of Au NCs are strongly confined by MgAl-ELDH nanosheets, which results in a largely promoted QY as well as prolonged fluorescence lifetime (both ~7 times enhancement). In addition, the as-fabricated Au NC/ELDH hybrid material exhibits excellent imaging properties with good stability and biocompatibility in the intracellular environment. Therefore, this work provides a facile strategy to achieve highly luminescent Au NCs via surface-confined emission enhancement imposed by ultrathin inorganic nanosheets, which can be potentially used in bio-imaging and cell labelling.Gold nanoclusters (Au NCs) as ultrasmall fluorescent nanomaterials possess discrete electronic energy and unique physicochemical properties, but suffer from relatively low quantum yield (QY) which severely affects their application in displays and imaging. To solve this conundrum and obtain highly-efficient fluorescent emission, 2D exfoliated layered double hydroxide (ELDH) nanosheets were employed to localize Au NCs with a density as high as 5.44 × 1013 cm-2, by virtue of the surface confinement effect of ELDH. Both experimental studies and computational simulations testify that the excited electrons of Au NCs are strongly confined by MgAl-ELDH nanosheets, which results in a largely promoted QY as well as prolonged fluorescence lifetime (both ~7 times enhancement). In addition, the as-fabricated Au NC/ELDH hybrid material exhibits excellent imaging properties with good stability and biocompatibility in the intracellular environment. Therefore, this work provides a facile strategy to achieve highly luminescent Au NCs via surface-confined emission enhancement imposed by ultrathin inorganic nanosheets, which can be potentially used in bio-imaging and cell labelling. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01624c

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

A nanoparticle-based epigenetic modulator for efficient gene modulation

NASA Astrophysics Data System (ADS)

Pongkulapa, Thanapat

Modulation of gene expression through chromatin remodeling involves epigenetic mechanisms, such as histone acetylation. Acetylation is tightly regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). Molecules that can regulate these enzymes by altering (activating or inhibiting) their functions have become a valuable tool for understanding cell development and diseases. HAT activators, i.e. N-(4-Chloro-(3-trifluoromethyl)phenyl)-2-ethoxybenzamide (CTB), have shown a therapeutic potential for many diseases, including cancer and neurodegeneration. However, these compounds encounter a solubility and a membrane permeability issue, which restricts their full potential for practical usage, especially for in vivo applications. To address this issue, in this work, we developed a nanoparticle-based HAT activator CTB, named Au-CTB, by incorporating a new CTB analogue onto gold nanoparticles (AuNPs) along with a poly(ethylene glycol) moiety and a nuclear localization signal (NLS) peptide to assist with solubility and membrane permeability. We found that our new CTB analogue and Au-CTB could activate HAT activity. Significantly, an increase in potency to activate HAT activity by Au-CTB proved the effectiveness of using the nanoparticle delivery platform. In addition, the versatility of Au-CTB platform permits the attachment of multiple ligands with tunable ratios on the nanoparticle surface via facile surface functionalization of gold nanoparticles. Due to its high delivery efficiency and versatility, Au-CTB can be a powerful platform for applications in epigenetic regulation of gene expression.

Shape and surface chemistry effects on the cytotoxicity and cellular uptake of metallic nanorods and nanospheres.

PubMed

Favi, Pelagie Marlene; Valencia, Mariana Morales; Elliott, Paul Robert; Restrepo, Alejandro; Gao, Ming; Huang, Hanchen; Pavon, Juan Jose; Webster, Thomas Jay

2015-12-01

Metallic nanoparticles (such as gold and silver) have been intensely studied for wound healing applications due to their ability to be easily functionalized, possess antibacterial properties, and their strong potential for targeted drug release. In this study, rod-shaped silver nanorods (AgNRs) and gold nanorods (AuNRs) were fabricated by electron beam physical vapor deposition (EBPVD), and their cytotoxicity toward human skin fibroblasts were assessed and compared to sphere-shaped silver nanospheres (AgNSs) and gold nanospheres (AuNSs). Results showed that the 39.94 nm AgNSs showed the greatest toxicity with fibroblast cells followed by the 61.06 nm AuNSs, ∼556 nm × 47 nm (11.8:1 aspect ratio) AgNRs, and the ∼534 nm × 65 nm (8.2:1 aspect ratio) AuNRs demonstrated the least amount of toxicity. The calculated IC50 (50% inhibitory concentration) value for the AgNRs exposed to fibroblasts was greater after 4 days of exposure (387.3 μg mL(-1)) compared to the AgNSs and AuNSs (4.3 and 23.4 μg mL(-1), respectively), indicating that these spherical metallic nanoparticles displayed a greater toxicity to fibroblast cells. The IC50 value could not be measured for the AuNRs due to an incomplete dose response curve. The reduced cell toxicity with the presently developed rod-shaped nanoparticles suggests that they may be promising materials for use in numerous biomedical applications. © 2015 Wiley Periodicals, Inc.

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.

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.

Polarization properties of fluorescent BSA protected Au25 nanoclusters.

PubMed

Raut, Sangram; Chib, Rahul; Rich, Ryan; Shumilov, Dmytro; Gryczynski, Zygmunt; Gryczynski, Ignacy

2013-04-21

BSA protected gold nanoclusters (Au25) are attracting a great deal of attention due to their unique spectroscopic properties and possible use in biophysical applications. Although there are reports on synthetic strategies, spectroscopy and applications, little is known about their polarization behavior. In this study, we synthesized the BSA protected Au25 nanoclusters and studied their steady state and time resolved fluorescence properties including polarization behavior in different solvents: glycerol, propylene glycol and water. We demonstrated that the nanocluster absorption spectrum can be separated from the extinction spectrum by subtraction of Rayleigh scattering. The nanocluster absorption spectrum is well approximated by three Gaussian components. By a comparison of the emissions from BSA Au25 clusters and rhodamine B in water, we estimated the quantum yield of nanoclusters to be higher than 0.06. The fluorescence lifetime of BSA Au25 clusters is long and heterogeneous with an average value of 1.84 μs. In glycerol at -20 °C the anisotropy is high, reaching a value of 0.35. However, the excitation anisotropy strongly depends on the excitation wavelengths indicating a significant overlap of the different transition moments. The anisotropy decay in water reveals a correlation time below 0.2 μs. In propylene glycol the measured correlation time is longer and the initial anisotropy depends on the excitation wavelength. BSA Au25 clusters, due to long lifetime and high polarization, can potentially be used in studying large macromolecules such as protein complexes with large molecular weight.

Decoration of silica nanowires with gold nanoparticles through ultra-short pulsed laser deposition

NASA Astrophysics Data System (ADS)

Gontad, F.; Caricato, A. P.; Cesaria, M.; Resta, V.; Taurino, A.; Colombelli, A.; Leo, C.; Klini, A.; Manousaki, A.; Convertino, A.; Rella, R.; Martino, M.; Perrone, A.

2017-10-01

The ablation of a metal target at laser energy densities in the range of 1-10 TW/cm2 leads to the generation of nanoparticles (NP) of the ablated material. This aspect is of particular interest if the immobilization of NPs on three-dimensional (3D) substrates is necessary as for example in sensing applications. In this work the deposition of Au NP by irradiation of a Au bulk target with a sub-picosecond laser beam (500 fs; 248 nm; 10 Hz) on 2D (silica and Si(100)) and 3D substrates (silica nanowire forests) is reported for different number of laser pulses (500, 1000, 1500, 2000, 2500). A uniform coverage of small Au NPs (with a diameter of few nm) on both kinds of substrates has been obtained using a suitable number of laser pulses. The presence of spherical droplets, with a diameter ranging from tens of nm up to few μm was also detected on the substrate surface and their presence can be explained by the weak electron-phonon coupling of Au. The optical characterization of the samples on 2D and 3D substrates evidenced the surface plasmon resonance peak characteristic of the Au NPs although further improvements of the size-distribution are necessary for future applications in sensing devices.

Coupling a universal DNA circuit with graphene sheets/polyaniline/AuNPs nanocomposites for the detection of BCR/ABL fusion gene.

PubMed

Chen, Xueping; Wang, Li; Sheng, Shangchun; Wang, Teng; Yang, Juan; Xie, Guoming; Feng, Wenli

2015-08-19

This article described a novel method by coupling a universal DNA circuit with graphene sheets/polyaniline/AuNPs nanocomposites (GS/PANI/AuNPs) for highly sensitive and specific detection of BCR/ABL fusion gene (bcr/abl) in chronic myeloid leukemia (CML). DNA circuit known as catalyzed hairpin assembly (CHA) is enzyme-free and can be simply operated to achieve exponential amplification, which has been widely employed in biosensing. However, application of CHA has been hindered by the need of specially redesigned sequences for each single-stranded DNA input. Herein, a transducer hairpin (HP) was designed to obtain a universal DNA circuit with favorable signal-to-background ratio. To further improve signal amplification, GS/PANI/AuNPs with excellent conductivity and enlarged effective area were introduced into this DNA circuit. Consequently, by combining the advantages of CHA and GS/PANI/AuNPs, bcr/abl could be detected in a linear range from 10 pM to 20 nM with a detection limit of 1.05 pM. Moreover, this protocol showed excellent specificity, good stability and was successfully applied for the detection of real sample, which demonstrated its great potential in clinical application. Copyright © 2015 Elsevier B.V. All rights reserved.

Molecularly stabilised ultrasmall gold nanoparticles: synthesis, characterization and bioactivity

NASA Astrophysics Data System (ADS)

Leifert, Annika; Pan-Bartnek, Yu; Simon, Ulrich; Jahnen-Dechent, Willi

2013-06-01

Gold nanoparticles (AuNPs) are widely used as contrast agents in electron microscopy as well as for diagnostic tests. Due to their unique optical and electrical properties and their small size, there is also a growing field of potential applications in medical fields of imaging and therapy, for example as drug carriers or as active compounds in thermotherapy. Besides their intrinsic optical properties, facile surface decoration with (bio)functional ligands renders AuNPs ideally suited for many industrial and medical applications. However, novel AuNPs may have toxicological profiles differing from bulk and therefore a thorough analysis of the quantitative structure-activity relationship (QSAR) is required. Several mechanisms are proposed that cause adverse effects of nanoparticles in biological systems. Catalytic generation of reactive species due to the large and chemically active surface area of nanomaterials is well established. Because nanoparticles approach the size of biological molecules and subcellular structures, they may overcome natural barriers by active or passive uptake. Ultrasmall AuNPs with sizes of 2 nm or less may even behave as molecular ligands. These types of potential interactions would imply a size and ligand-dependent behaviour of any nanomaterial towards biological systems. Thus, to fully understand their QSAR, AuNPs bioactivity should be analysed in biological systems of increasing complexity ranging from cell culture to whole animal studies.

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 a colloid solution of silica-coated gold nanoparticles for X-ray imaging applications

NASA Astrophysics Data System (ADS)

Kobayashi, Yoshio; Nagasu, Ryoko; Shibuya, Kyosuke; Nakagawa, Tomohiko; Kubota, Yohsuke; Gonda, Kohsuke; Ohuchi, Noriaki

2014-08-01

This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 °C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol-gel process. The sol-gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2-NH2). Surface modification of the Au/SiO2-NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2-NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 ± 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h.

Modification of the internal surface of photonic crystal fibers with Ag and Au nanoparticles for application as sensor elements

NASA Astrophysics Data System (ADS)

Pidenko, Pavel S.; Borzov, Victor M.; Savenko, Olga A.; Skaptsov, Alexander A.; Skibina, Yulia S.; Goryacheva, Irina Yu.; Rusanova, Tatiana Yu.

2017-03-01

Photonic crystal fibers (PCFs) are one of the most promising materials for biosensors construction due to their unique optical properties. The modification of PCF by noble metal nanoparticles (NPs) provides the SPR and SERS signal detection where as the application amino group-containing compounds allows efficient binding of biomolecules. In this work the internal surface of glass hollow core photonic crystal fibers (HC-PCFs) has been modified Ag and Au nanoparticles using three different approaches. PCFs were treated by: 1) mixture of NPs and precursors for silanization (tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES)); 2) alternately deposition of polyelectrolytes and NPs, 3) mixture of chitosan with NPs. The shift of local maxima in the HC-PCF transmission spectrum has been selected as a signal for estimating the amount of NPs on the HC-PCF inner surface. The most efficient techniques were the chitosan application for Ag NPs and silanization for Au NPs. The obtaining PCFs could be useful for creating biosensitive elements.

Characterization of Surface-Enhanced Raman Scattering of Nicotine Utilizing Plasmonic Nanometals for the Applications of Medical and Chemical Sensing

NASA Astrophysics Data System (ADS)

Jackson, Ashley; Rigo, Maria; Seo, Jaetae; HU Team

2011-05-01

Raman spectroscopy has received a great deal of interest for its applications in biological sensing and cell imaging due to the ease with which it can be used to extract significant data from tissue and cells. This study has focused on the application of SERS for nicotine detection. Liquid nicotine was diluted and combined with Au nanoparticles (NPs). The nicotine-gold solution was analyzed by acquiring Raman spectra data using a Delta Nu Spectrometer. Absorption data shows the characteristic peak of Au NPs at ~528 nm while showing successful aggregation of the nicotine particles. Data taken from Raman spectra shows characteristic Raman shifts of nicotine at ~1030 cm-1 and ~1590 cm-1. Currently work is being done to optimize the SERS signal for nicotine in the 1590-1600 region using higher concentrations of nicotine and various sizes of Au NPs. This work at Hampton University was supported by the National Science Foundation (HRD-0734635 and HRD-063037).

A low cost technique for synthesis of gold nanoparticles using microwave heating and its application in signal amplification for detecting Escherichia Coli O157:H7 bacteria

NASA Astrophysics Data System (ADS)

Thanh Ngo, Vo Ke; Giang Nguyen, Dang; Phat Huynh, Trong; Lam, Quang Vinh

2016-09-01

In the present work a low cost technique for preparation of gold nanoparticles (AuNPs) using microwave heating was developed. The effect of different elements (precursor reagents, irradiation time, and microwave radiation power) on the final morphology of AuNPs obtained through the microwave assisted technique has been investigated. The characterization of the samples has been carried out by transmission electron microscopy, UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, and powder x-ray diffraction. The results showed that to some extent the above-mentioned characterizations influenced the size of synthetized nanoparticles and application of microwave heating has many advantages such as low cost, rapid preparation and highly uniform particles. As an application in quartz crystal microbalance (QCM) immunosensor, AuNPs are conjugated with the Escherichia coli (E.coli) O157:H7 antibodies for signal amplification to detect E.coli O157:H7 bacteria residual in QCM system.

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.

Au-assisted fabrication of nano-holes on c-plane sapphire via thermal treatment guided by Au nanoparticles as catalysts

NASA Astrophysics Data System (ADS)

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

2017-01-01

Nanoscale patterning of sapphires is a challenging task due to the high mechanical strength, chemical stability as well as thermal durability. In this paper, we demonstrate a gold droplet assisted approach of nano-hole fabrication on c-plane sapphire via a thermal treatment. Uniformly distributed nano-holes are fabricated on the sapphire surface guided by dome shaped Au nanoparticles (NPs) as catalysts and the patterning process is discussed based on the disequilibrium of vapor, liquid, solid interface energies at the Au NP/sapphire interface induced by the Au evaporation at high temperature. Followed by the re-equilibration of interface energy, transport of alumina from the beneath of NPs to the sapphire surface can occur along the NP/sapphire interface resulting in the formation of nano-holes. The fabrication of nano-holes using Au NPs as catalysts is a flexible, economical and convenient approach and can find applications in various optoelectronics.

ITO/Au/ITO sandwich structure for near-infrared plasmonics.

PubMed

Fang, Xu; Mak, Chee Leung; Dai, Jiyan; Li, Kan; Ye, Hui; Leung, Chi Wah

2014-09-24

ITO/Au/ITO trilayers with varying gold spacer layer thicknesses were deposited on glass substrates by pulsed laser deposition. Transmission electron microscopy measurements demonstrated the continuous nature of the Au layer down to 2.4 nm. XRD patterns clearly showed an enhanced crystallinity of the ITO films promoted by the insertion of the gold layer. Compared with a single layer of ITO with a carrier concentration of 7.12 × 10(20) cm(-3), the ITO/Au/ITO structure achieved an effective carrier concentration as high as 3.26 × 10(22) cm(-3). Transmittance and ellipsometry measurements showed that the optical properties of ITO/Au/ITO films were greatly influenced by the thickness of the inserted gold layer. The cross-point wavelength of the trilayer samples was reduced with increasing gold layer thickness. Importantly, the trilayer structure exhibited a reduced loss (compared with plain Au) in the near-infrared region, suggesting its potential for plasmonic applications in the near-infrared range.

Superparamagnetic Nanoparticles as High Efficiency Magnetic Resonance Imaging T2 Contrast Agent.

PubMed

Sousa, Fernanda; Sanavio, Barbara; Saccani, Alessandra; Tang, Yun; Zucca, Ileana; Carney, Tamara M; Mastropietro, Alfonso; Jacob Silva, Paulo H; Carney, Randy P; Schenk, Kurt; Omrani, Arash O; Huang, Ping; Yang, Lin; Rønnow, Henrik M; Stellacci, Francesco; Krol, Silke

2017-01-18

Nanoparticle-based magnetic resonance imaging T 2 negative agents are of great interest, and much effort is devoted to increasing cell-loading capability while maintaining low cytotoxicity. Herein, two classes of mixed-ligand protected magnetic-responsive, bimetallic gold/iron nanoparticles (Au/Fe NPs) synthesized by a two-step method are presented. Their structure, surface composition, and magnetic properties are characterized. The two classes of sulfonated Au/Fe NPs, with an average diameter of 4 nm, have an average atomic ratio of Au to Fe equal to 7 or 8, which enables the Au/Fe NPs to be superparamagnetic with a blocking temperature of 56 K and 96 K. Furthermore, preliminary cellular studies reveal that both Au/Fe NPs show very limited toxicity. MRI phantom experiments show that r 2 /r 1 ratio of Au/Fe NPs is as high as 670, leading to a 66% reduction in T 2 relaxation time. These nanoparticles provide great versatility and potential for nanoparticle-based diagnostics and therapeutic applications and as imaging contrast agents.

Enhanced Delivery of Gold Nanoparticles with Therapeutic Potential into the Brain using MRI-Guided Focused Ultrasound

PubMed Central

Etame, Arnold B.; Diaz, Roberto J.; O’Reilly, Meaghan A.; Smith, Christian A.; Mainprize, Todd G.; Hynynen, Kullervo; Rutka, James T.

2014-01-01

The blood brain barrier (BBB) is a major impediment to the delivery of therapeutics into the central nervous system (CNS). Gold nanoparticles (AuNPs) have been successfully employed in multiple potential therapeutic and diagnostic applications outside the CNS. However, AuNPs have very limited biodistribution within the CNS following intravenous administration. Magnetic resonance imaging guided focused ultrasound (MRgFUS) is a novel technique that can transiently increase BBB permeability allowing delivery of therapeutics into the CNS. MRgFUS has not been previously employed for delivery of AuNPs into the CNS. This work represents the first demonstration of focal enhanced delivery of AuNPs into the CNS using MRgFUS in a rat model both safely and effectively. Histologic visualization and analytical quantification of AuNPs within the brain parenchyma suggest BBB transgression. These results suggest a role for MRgFUS in the delivery of AuNPs with therapeutic potential into the CNS for targeting neurological diseases. PMID:22349099

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.

SERS-active Au/SiO2 clouds in powder for rapid ex vivo breast adenocarcinoma diagnosis

PubMed Central

Cepeda-Pérez, Elisa; López-Luke, Tzarara; Salas, Pedro; Plascencia-Villa, Germán; Ponce, Arturo; Vivero-Escoto, Juan; José-Yacamán, Miguel; de la Rosa, Elder

2016-01-01

In the present work, we report a dry-based application technique of Au/SiO2 clouds in powder for rapid ex vivo adenocarcinoma diagnosis through surface-enhanced Raman scattering (SERS); using low laser power and an integration time of one second. Several characteristic Raman peaks frequently used for the diagnosis of breast adenocarcinoma in the range of the amide III are successfully enhanced by breading the tissue with Au/SiO2 powder. The SERS activity of these Au/SiO2 powders is attributed to their rapid rehydration upon contact with the wet tissues, which promotes the formation of gold nanoparticle aggregates. The propensity of the Au/SiO2 cloud structures to adsorb biomolecules in the vicinity of the gold nanoparticle clusters promotes the necessary conditions for SERS detection. In addition, electron microscopy, together with elemental analysis, have been used to confirm the structure of the new Au/SiO2 cloud material and to investigate its distribution in breast tissues. PMID:27375955

Gold Nanoparticle Mediated Cancer Immunotherapy

PubMed Central

Almeida, Joao Paulo Mattos; Figueroa, Elizabeth Raquel; Drezek, Rebekah Anna

2013-01-01

Significant progress has been made in the field of cancer immunotherapy, where the goal is to activate or modulate the body’s immune response against cancer. However, current immunotherapy approaches exhibit limitations of safety and efficacy due to systemic delivery. In this context, the use of nanotechnology for the delivery of cancer vaccines and immune adjuvants presents a number of advantages such as targeted delivery to immune cells, enhanced therapeutic effect, and reduced adverse outcomes. Recently, gold nanoparticles (AuNP) have been explored as immunotherapy carriers, creating new AuNP applications that merit a critical overview. This review highlights recent advances in the development of AuNP mediated immunotherapies that harness AuNP biodistribution, optical properties and their ability to deliver macromolecules such as peptides and oligonucleotides. It has been demonstrated that the use of AuNP carriers can improve the delivery and safety of immunotherapy agents, and that AuNP immunotherapies are well suited for synergistic combination therapy with existing cancer therapies like photothermal ablation. PMID:24103304

Crystal phase-based epitaxial growth of hybrid noble metal nanostructures on 4H/fcc Au nanowires

NASA Astrophysics Data System (ADS)

Lu, Qipeng; Wang, An-Liang; Gong, Yue; Hao, Wei; Cheng, Hongfei; Chen, Junze; Li, Bing; Yang, Nailiang; Niu, Wenxin; Wang, Jie; Yu, Yifu; Zhang, Xiao; Chen, Ye; Fan, Zhanxi; Wu, Xue-Jun; Chen, Jinping; Luo, Jun; Li, Shuzhou; Gu, Lin; Zhang, Hua

2018-03-01

Crystal-phase engineering offers opportunities for the rational design and synthesis of noble metal nanomaterials with unusual crystal phases that normally do not exist in bulk materials. However, it remains a challenge to use these materials as seeds to construct heterometallic nanostructures with desired crystal phases and morphologies for promising applications such as catalysis. Here, we report a strategy for the synthesis of binary and ternary hybrid noble metal nanostructures. Our synthesized crystal-phase heterostructured 4H/fcc Au nanowires enable the epitaxial growth of Ru nanorods on the 4H phase and fcc-twin boundary in Au nanowires, resulting in hybrid Au-Ru nanowires. Moreover, the method can be extended to the epitaxial growth of Rh, Ru-Rh and Ru-Pt nanorods on the 4H/fcc Au nanowires to form unique hybrid nanowires. Importantly, the Au-Ru hybrid nanowires with tunable compositions exhibit excellent electrocatalytic performance towards the hydrogen evolution reaction in alkaline media.

Work function tuning at Au-HfO{sub 2} interfaces using organophosphonate monolayers

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

Kwan, Matthew; Cardinal, Thomas; Ramanath, Ganpati, E-mail: Ramanath@rpi.edu

2016-05-09

We show that introducing organophosphonate nanomolecular monolayers (NMLs) at Au-HfO{sub 2} interfaces shift the effective work function by 0.2 eV ≥ ΔΦ{sub eff} ≥ −0.6 eV, due to NML body and bonding dipoles. Electron spectroscopy of NML-Au, NML-HfO{sub 2,} and Au-NML-HfO{sub 2} structures indicate that the Au-NML bond strength is the major factor. Au-NML covalent bonding yields ΔΦ{sub eff} ∼ − 0.2 eV, while weak bonding yields ΔΦ{sub eff} ∼ 0.6 eV. In contrast, NMLs on HfO{sub 2} decrease Φ{sub eff} by ∼0.4 eV due to competing contributions from NML-HfO{sub 2} bonding strength and NML orientation. These findings are relevant for nanomolecularly tailoring the electronic properties of metal–ceramic interfaces for applications.

Real time acousto-ultrasonic NDE technique for monitoring damage in ceramic composites under dynamic loads

NASA Technical Reports Server (NTRS)

Tiwari, Anil

1995-01-01

Research effort was directed towards developing a near real-time, acousto-ultrasonic (AU), nondestructive evaluation (NDE) tool to study the failure mechanisms of ceramic composites. Progression of damage is monitored in real-time by observing the changes in the received AU signal during the actual test. During the real-time AU test, the AU signals are generated and received by the AU transducers attached to the specimen while it is being subjected to increasing quasi-static loads or cyclic loads (10 Hz, R = 1.0). The received AU signals for 64 successive pulses were gated in the time domain (T = 40.96 micro sec) and then averaged every second over ten load cycles and stored in a computer file during fatigue tests. These averaged gated signals are representative of the damage state of the specimen at that point of its fatigue life. This is also the first major attempt in the development and application of real-time AU for continuously monitoring damage accumulation during fatigue without interrupting the test. The present work has verified the capability of the AU technique to assess the damage state in silicon carbide/calcium aluminosilicate (SiC/CAS) and silicon carbide/ magnesium aluminosilicate (SiC/MAS) ceramic composites. Continuous monitoring of damage initiation and progression under quasi-static ramp loading in tension to failure of unidirectional and cross-ply SiC/CAS and quasi-isotropic SiC/MAS ceramic composite specimens at room temperature was accomplished using near real-time AU parameters. The AU technique was shown to be able to detect the stress levels for the onset and saturation of matrix cracks, respectively. The critical cracking stress level is used as a design stress for brittle matrix composites operating at elevated temperatures. The AU technique has found that the critical cracking stress level is 10-15% below the level presently obtained for design purposes from analytical models. An acousto-ultrasonic stress-strain response (AUSSR) model for unidirectional and cross-ply ceramic composites was formulated. The AUSSR model predicts the strain response to increasing stress levels using real-time AU data and classical laminated plate theory. The Weibull parameters of the AUSSR model are used to calculate the design stress for thermo-structural applications. Real-time AU together with the AUSSR model was used to study the failure mechanisms of SiC/CAS ceramic composites under static and fatigue loading. An S-N curve was generated for a cross-ply SiC/CAS ceramic composite material. The AU results are corroborated and complemented by other NDE techniques, namely, in-situ optical microscope video recordings and edge replication.

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.

Three-body Coulomb problem probed by mapping the Bethe surface in ionizing ion-atom collisions.

PubMed

Moshammer, R; Perumal, A; Schulz, M; Rodríguez, V D; Kollmus, H; Mann, R; Hagmann, S; Ullrich, J

2001-11-26

The three-body Coulomb problem has been explored in kinematically complete experiments on single ionization of helium by 100 MeV/u C(6+) and 3.6 MeV/u Au(53+) impact. Low-energy electron emission ( E(e)<150 eV) as a function of the projectile deflection theta(p) (momentum transfer), i.e., the Bethe surface [15], has been mapped with Delta theta(p)+/-25 nanoradian resolution at extremely large perturbations ( 3.6 MeV/u Au(53+)) where single ionization occurs at impact parameters of typically 10 times the He K-shell radius. The experimental data are not in agreement with state-of-the-art continuum distorted wave-eikonal initial state theory.

Dispersed gold nanoparticles potentially ruin gold barley yellow dwarf virus and eliminate virus infectivity hazards

NASA Astrophysics Data System (ADS)

Alkubaisi, Noorah A.; Aref, Nagwa M. A.

2017-02-01

Gold nanoparticles (AuNPs) application melted barley yellow dwarf virus-PAV (BYDV-PAV) spherical nanoparticle capsids. Synergistic therapeutic effects for plant virus resistance were induced by interaction with binding units of prepared AuNPs in a water solution which was characterized and evaluated by zeta sizer, zeta potential and transmission electron microscopy (TEM). The yield of purified nanoparticles of BYDV-PAV was obtained from Hordeum vulgare (Barley) cultivars, local and Giza 121/Justo. It was 0.62 mg/ml from 27.30 g of infected leaves at an A260/A280 ratio. Virus nanoparticle has a spherical shape 30 nm in size by TEM. BYDV-PAV combined with AuNPs to challenge virus function in vivo and in vitro. Dual AuNPs existence in vivo and in vitro affected compacted configuration of viral capsid protein in the interior surface of capsomers, the outer surface, or between the interface of coat protein subunits for 24 and 48 h incubation period in vitro at room temperature. The sizes of AuNPs that had a potentially dramatic deteriorated effect are 3.151 and 31.67 nm with a different intensity of 75.3% for the former and 24.7% for the latter, which enhances optical sensing applications to eliminate virus infectivity. Damages of capsid protein due to AuNPs on the surface of virus subunits caused variable performance in four different types of TEM named puffed, deteriorated and decorated, ruined and vanished. Viral yield showed remarkably high-intensity degree of particle symmetry and uniformity in the local cultivar greater than in Giza 121/Justo cultivar. A high yield of ruined VLPs in the local cultivar than Justo cultivar was noticed. AuNPs indicated complete lysed VLPs and some deteriorated VLPs at 48 h.

Au nanoparticles-ZnO composite nanotubes using natural silk fibroin fiber as template for electrochemical non-enzymatic sensing of hydrogen peroxide.

PubMed

Chen, Liangliang; Xu, Xiaolong; Cui, Feng; Qiu, Qianying; Chen, Xiaojun; Xu, Jinzhong

2018-05-23

A novel electrochemical sensor based on the composite of gold nanoparticles/zinc oxide nanotube (AuNPs/ZnO-NTs) was constructed and its application as hydrogen peroxide (H 2 O 2 ) non-enzymatic sensor was investigated. ZnO-NTs were prepared by a biomineralization strategy in which silk fibroin fiber (SFF) was used as template, and thus the ZnO-NTs inherited the advantages of SFF such as mechanical stability, flexible biomimetic morphology and biocompatibility. The AuNPs/ZnO-NTs was further prepared by the electrostatic absorption of AuNPs onto the surface of ZnO-NTs, and found to be capable to catalyze the reduction of H 2 O 2 . The working potential was 0.05 V, which was far higher than those in literatures, indicating the strong anti-interference ability in the real application. The catalytic current was linearly proportional in the concentration range of 1 μM-3.0 mM with a sensitivity of 1336.7 μA mM -1  cm -2 . The detection limit was estimated to be 0.1 μM (S/N = 3). Such a high sensitivity was attributed to the electrocatalytic property of ZnO and high electron transfer ability of AuNPs/ZnO-NTs structure. Moreover, the final detection results of H 2 O 2 in real samples showed the acceptable accuracy compared with the traditional potassium permanganate titration, exhibiting the prospect to be used as an applicable sensor in actual detections. Copyright © 2018 Elsevier Inc. All rights reserved.

Green synthesis of noble nanometals (Au, Pt, Pd) using glycerol under microwave irradiation conditions

EPA Science Inventory

A newer application of glycerol in the field of nanomaterials synthesis has been developed from both the economic and environmental points of view. Glycerol can act as a reducing agent for the fabrication of noble nanometals, such as Au, Pt, and Pd, under microwave irradiation. T...

BSA modification to reduce CTAB induced nonspecificity and cytotoxicity of aptamer-conjugated gold nanorods

NASA Astrophysics Data System (ADS)

Yasun, Emir; Li, Chunmei; Barut, Inci; Janvier, Denisse; Qiu, Liping; Cui, Cheng; Tan, Weihong

2015-05-01

Aptamer-conjugated gold nanorods (AuNRs) are excellent candidates for targeted hyperthermia therapy of cancer cells. However, in high concentrations of AuNRs, aptamer conjugation alone fails to result in highly cell-specific AuNRs due to the presence of positively charged cetyltrimethylammonium bromide (CTAB) as a templating surfactant. Besides causing nonspecific electrostatic interactions with the cell surfaces, CTAB can also be cytotoxic, leading to uncontrolled cell death. To avoid the nonspecific interactions and cytotoxicity triggered by CTAB, we report the further biologically inspired modification of aptamer-conjugated AuNRs with bovine serum albumin (BSA) protein. Following this modification, interaction between CTAB and the cell surface was efficiently blocked, thereby dramatically reducing the side effects of CTAB. This approach may provide a general and simple method to avoid one of the most serious issues in biomedical applications of nanomaterials: nonspecific binding of the nanomaterials with biological cells.Aptamer-conjugated gold nanorods (AuNRs) are excellent candidates for targeted hyperthermia therapy of cancer cells. However, in high concentrations of AuNRs, aptamer conjugation alone fails to result in highly cell-specific AuNRs due to the presence of positively charged cetyltrimethylammonium bromide (CTAB) as a templating surfactant. Besides causing nonspecific electrostatic interactions with the cell surfaces, CTAB can also be cytotoxic, leading to uncontrolled cell death. To avoid the nonspecific interactions and cytotoxicity triggered by CTAB, we report the further biologically inspired modification of aptamer-conjugated AuNRs with bovine serum albumin (BSA) protein. Following this modification, interaction between CTAB and the cell surface was efficiently blocked, thereby dramatically reducing the side effects of CTAB. This approach may provide a general and simple method to avoid one of the most serious issues in biomedical applications of nanomaterials: nonspecific binding of the nanomaterials with biological cells. Electronic supplementary information (ESI) available: Fig. S-1 to S-6 are included. See DOI: 10.1039/c5nr01704a

A highly crystalline single Au wire network as a high temperature transparent heater

NASA Astrophysics Data System (ADS)

Rao, K. D. M.; Kulkarni, Giridhar U.

2014-05-01

A transparent conductor which can generate high temperatures finds important applications in optoelectronics. In this article, a wire network made of Au on quartz is shown to serve as an effective high temperature transparent heater. The heater has been fabricated by depositing Au onto a cracked sacrificial template. The highly interconnected Au wire network thus formed exhibited a transmittance of ~87% in a wide spectral range with a sheet resistance of 5.4 Ω □-1. By passing current through the network, it could be joule heated to ~600 °C within a few seconds. The extraordinary thermal performance and stability owe much to the seamless junctions present in the wire network. Furthermore, the wire network gets self-annealed through joule heating as seen from its increased crystallinity. Interestingly, both transmittance and sheet resistance improved following annealing to 92% and 3.2 Ω □-1, respectively. A transparent conductor which can generate high temperatures finds important applications in optoelectronics. In this article, a wire network made of Au on quartz is shown to serve as an effective high temperature transparent heater. The heater has been fabricated by depositing Au onto a cracked sacrificial template. The highly interconnected Au wire network thus formed exhibited a transmittance of ~87% in a wide spectral range with a sheet resistance of 5.4 Ω □-1. By passing current through the network, it could be joule heated to ~600 °C within a few seconds. The extraordinary thermal performance and stability owe much to the seamless junctions present in the wire network. Furthermore, the wire network gets self-annealed through joule heating as seen from its increased crystallinity. Interestingly, both transmittance and sheet resistance improved following annealing to 92% and 3.2 Ω □-1, respectively. Electronic supplementary information (ESI) available: Optical micrographs, EDAX, XRD, SEM and TEM images of Au metal wires. See DOI: 10.1039/c4nr00869c

Synthesis of nano-cuboidal gold particles for effective antimicrobial property against clinical human pathogens.

PubMed

Murphin Kumar, Paskalis Sahaya; MubarakAli, Davoodbasha; Saratale, Rijuta Ganesh; Saratale, Ganesh Dattatraya; Pugazhendhi, Arivalagan; Gopalakrishnan, Kumar; Thajuddin, Nooruddin

2017-12-01

Algae could offer a potential source of fine chemicals, pharmaceuticals and biofuels. In this study, a green synthesis of dispersed cuboidal gold nanoparticles (AuNPs) was achieved using red algae, Gelidium amansii reacted with HAuCl 4 . It was found to be 4-7 nm sized cubical nanoparticles with aspect ratio of 1.4 were synthesized using 0.5 mM of HAuCl 4 by HRSEM analysis. The crystalline planes (111), (200), (220), (311) and elemental signal of gold was observed by XRD and EDS respectively. The major constitutes, galactose and 3,6-anhydrogalactose in the alga played a critical role in the synthesis of crystalline AuNPs with cubical dimension. Further, the antibacterial potential of synthesized AuNPs was tested against human pathogens, Escherichia coli and Staphylococcus aureus. The synthesized AuNPs found biocompatible up to 100 ppm and high concentration showed an inhibition against cancer cell. This novel report could be helped to exploration of bioresources to material synthesis for the application of biosensor and biomedical application. Copyright © 2017 Elsevier Ltd. All rights reserved.

Peroxidase-like activity of apoferritin paired gold clusters for glucose detection.

PubMed

Jiang, Xin; Sun, Cuiji; Guo, Yi; Nie, Guangjun; Xu, Li

2015-02-15

The discovery and application of noble metal nanoclusters have received considerable attention. In this paper, we reported that apoferritin paired gold clusters (Au-Ft) could efficiently catalyze oxidation of 3.3',5.5'-tetramethylbenzidine (TMB) by H2O2 to produce a blue color reaction. Compared with natural enzyme, Au-Ft exhibited higher activity near acidic pH and could be used over a wide range of temperatures. Apoferritin nanocage enhanced the reaction activity of substrate TMB by H2O2. The reaction catalyzed by Au-Ft was found to follow a typical Michaelis-Menten kinetics. The kinetic parameters exhibited a lower K(m) value (0.097 mM) and a higher K(cat) value (5.8 × 10(4) s(-1)) for TMB than that of horse radish peroxidase (HRP). Base on these findings, Au-Ft, acting as a peroxidase mimetic, performed enzymatic spectrophotometric analysis of glucose. This system exhibited acceptable reproducibility and high selectivity in biosening, suggesting that it could have promising applications in the future. Copyright © 2014 Elsevier B.V. All rights reserved.

Mixed Phytochemicals Mediated Synthesis of Multifunctional Ag-Au-Pd Nanoparticles for Glucose Oxidation and Antimicrobial Applications.

PubMed

Rao, K Jagajjanani; Paria, Santanu

2015-07-01

The growing awareness toward the environment is increasing commercial demand for nanoparticles by green route syntheses. In this study, alloy-like Ag-Au-Pd trimetallic nanoparticles have been prepared by two plants extracts Aegle marmelos leaf (LE) and Syzygium aromaticum bud extracts (CE). Compositionally different Ag-Au-Pd nanoparticles with an atomic ratio of 5.26:2.16:1.0 (by LE) and 11.36:13.14:1.0 (by LE + CE) of Ag:Au:Pd were easily synthesized within 10 min at ambient conditions by changing the composition of phytochemicals. The average diameters of the nanoparticles by LE and LE + CE are ∼8 and ∼11 nm. The catalytic activity of the trimetallic nanoparticles was studied, and they were found to be efficient catalysts for the glucose oxidation process. The prepared nanoparticles also exhibited efficient antibacterial activity against a model Gram-negative bacteria Escherichia coli. The catalytic and antimicrobial properties of these readymade trimetallic nanoparticles have high possibility to be utilized in diverse fields of applications such as health care to environmental.

Gold Decorated Graphene for Rapid Dye Reduction and Efficient Electro Catalytic Oxidation of Ethanol

NASA Astrophysics Data System (ADS)

Siddhardha, R. S.; Kumar v, Lakshman; Kaniyoor, A.; Podila, R.; Kumar, V. S.; Venkataramaniah, K.; Ramaprabhu, S.; Rao, A.; Ramamurthy, S. S.; Clemson University Team; Sri Sathya Sai Institute of Higher Learning Team; IITMadras Team

2013-03-01

A well known disadvantage in fabrication of metal-graphene composite is the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. Here, we demonstrate a novel one pot synthesis of gold nanoparticles (AuNPs) by laser ablation of gold strip and simultaneous decoration of these on functionalized graphene derivatives. Not only the impregnation of AuNPs was linker free, but also the synthesis by itself was surfactant free. This resulted in in-situ decoration of pristine AuNPs on functionalized graphene derivatives. These materials were well characterized and tested for catalytic applications pertaining to dye reduction and electrooxidation. The catalytic reduction rates are 1.4 x 102 and 9.4x102 times faster for Rhodamine B and Methylene Blue dyes respectively, compared to earlier reports. The enhanced rate involves synergistic interplay of electronic relay between AuNPs and the dye, also charge transfer between the graphene system and dye. In addition, the onset potential for ethanol oxidation was found to be more negative ~ 100 mV, an indication of its promising application in direct ethanol fuel cells.

Gold Nanoparticle-Based Facile Detection of Human Serum Albumin and Its Application as an INHIBIT Logic Gate.

PubMed

Huang, Zhenzhen; Wang, Haonan; Yang, Wensheng

2015-05-06

In this work, a facile colorimetric method is developed for quantitative detection of human serum albumin (HSA) based on the antiaggregation effect of gold nanoparticles (Au NPs) in the presence of HSA. The citrate-capped Au NPs undergo a color change from red to blue when melamine is added as a cross-linker to induce the aggregation of the NPs. Such an aggregation is efficiently suppressed upon the adsorption of HSA on the particle surface. This method provides the advantages of simplicity and cost-efficiency for quantitative detection of HSA with a detection limit of ∼1.4 nM by monitoring the colorimetric changes of the Au NPs with UV-vis spectroscopy. In addition, this approach shows good selectivity for HSA over various amino acids, peptides, and proteins and is qualified for detection of HSA in a biological sample. Such an antiaggregation effect can be further extended to fabricate an INHIBIT logic gate by using HSA and melamine as inputs and the color changes of Au NPs as outputs, which may have application potentials in point-of-care medical diagnosis.

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.

Optical properties of truncated Au nanocages with different size and shape

NASA Astrophysics Data System (ADS)

Chen, Qin; Qi, Hong; Ren, Ya-Tao; Sun, Jian-Ping; Ruan, Li-Ming

2017-06-01

The hollow nanostructures are conducive to applications including drug delivery, energy storage and conversion, and catalysis. In the present work, a versatile type of Au nanoparticles, i.e. nanocage with hollow interior, was studied thoroughly. Simulation of the optical properties of nanocages with different sizes and shapes was presented, which is essential for tuning the localized surface plasmon resonance peak. The edge length, side length of triangle, and wall thickness were used as structural parameters of truncated Au nanocage. The dependence of absorption efficiency, resonant wavelength, and absorption quantum yield on the structural parameters were discussed. Meanwhile, the applications of absorption quantum yield in biomedical imaging and laser induced thermal therapy were investigated. It was found that the phenomenon of multipolar plasmon resonances exists on truncated Au nanocage. Furthermore, the electric field distribution at different resonant wavelengths was also investigated. It is found that the electromagnetic field corresponds to the dipolar mode in an individual nanocage is largely distributed at the corners. Whereas, the electromagnetic field corresponds to the multipolar region is mainly located in the internal corners and edges.

Effect of thione primers on adhesive bonding between an indirect composite material and Ag-Pd-Cu-Au alloy.

PubMed

Imai, Hideyuki; Koizumi, Hiroyasu; Shimoe, Saiji; Hirata, Isao; Matsumura, Hideo; Nikawa, Hiroki

2014-01-01

The current study evaluated the effect of primers on the shear bond strength of an indirect composite material joined to a silverpalladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell). Disk specimens were cast from the alloy and were air-abraded with alumina. Eight metal primers were applied to the alloy surface. A light-polymerized indirect composite material (Solidex) was bonded to the alloy. Shear bond strength was determined both before and after the application of thermocycling. Two groups primed with Metaltite (thione) and M. L. Primer (sulfide) showed the greatest post-thermocycling bond strength (8.8 and 6.5 MPa). The results of the X-ray photoelectron spectroscopic (XPS) analysis suggested that the thione monomer (MTU-6) in the Metaltite primer was strongly adsorbed onto the Ag-Pd-Cu-Au alloy surface even after repeated cleaning with acetone. The application of either the thione (MTU-6) or sulfide primer is effective for enhancing the bonding between a composite material and Ag-Pd-Cu-Au alloy.

Eco-friendly approach for nanoparticles synthesis and mechanism behind antibacterial activity of silver and anticancer activity of gold nanoparticles.

PubMed

Patil, Maheshkumar Prakash; Kim, Gun-Do

2017-01-01

This review covers general information about the eco-friendly process for the synthesis of silver nanoparticles (AgNP) and gold nanoparticles (AuNP) and focuses on mechanism of the antibacterial activity of AgNPs and the anticancer activity of AuNPs. Biomolecules in the plant extract are involved in reduction of metal ions to nanoparticle in a one-step and eco-friendly synthesis process. Natural plant extracts contain wide range of metabolites including carbohydrates, alkaloids, terpenoids, phenolic compounds, and enzymes. A variety of plant species and plant parts have been successfully extracted and utilized for AgNP and AuNP syntheses. Green-synthesized nanoparticles eliminate the need for a stabilizing and capping agent and show shape and size-dependent biological activities. Here, we describe some of the plant extracts involved in nanoparticle synthesis, characterization methods, and biological applications. Nanoparticles are important in the field of pharmaceuticals for their strong antibacterial and anticancer activity. Considering the importance and uniqueness of this concept, the synthesis, characterization, and application of AgNPs and AuNPs are discussed in this review.

Energy level alignment at hybridized organic-metal interfaces from a GW projection approach

NASA Astrophysics Data System (ADS)

Chen, Yifeng; Tamblyn, Isaac; Quek, Su Ying

Energy level alignments at organic-metal interfaces are of profound importance in numerous (opto)electronic applications. Standard density functional theory (DFT) calculations generally give incorrect energy level alignments and missing long-range polarization effects. Previous efforts to address this problem using the many-electron GW method have focused on physisorbed systems where hybridization effects are insignificant. Here, we use state-of-the-art GW methods to predict the level alignment at the amine-Au interface, where molecular levels do hybridize with metallic states. This non-trivial hybridization implies that DFT result is a poor approximation to the quasiparticle states. However, we find that the self-energy operator is approximately diagonal in the molecular basis, allowing us to use a projection approach to predict the level alignments. Our results indicate that the metallic substrate reduces the HOMO-LUMO gap by 3.5 4.0 eV, depending on the molecular coverage/presence of Au adatoms. Our GW results are further compared with those of a simple image charge model that describes the level alignment in physisorbed systems. Syq and YC acknowledge Grant NRF-NRFF2013-07 and the medium-sized centre program from the National Research Foundation, Singapore.

Etude de L'interface Or/silicium Par Analyse de Surface et Microscopie Electronique

NASA Astrophysics Data System (ADS)

Lamontagne, Boris

In order to start with the cleanest c-Si surface achievable, two cleaning procedures have been used and compared: aqueous chemical cleaning with HF, and sputter cleaning followed by high temperature annealing; the former is found to be the most efficient of the two. We have observed the formation of Si-C bonds induced by energetic particles associated to sputtering and sputter deposition. One of the main objectives of this work was to compare the Au/Si interfaces obtained by e-beam evaporation and by sputter deposition; Ag/Si, Cu/Si and Al/Si interfaces have also been examined. X-ray photoelectron diffraction has allowed us to judge the quality of the substrate crystallinity under the metallic overlayer, a method which readily showed the amorphisation of the c-Si substrate induced by sputter deposition. Moreover, XPD has indicated the Au overlayer to be amorphous, while the Ag and Cu appear to grow heteroepitaxially on c-Si(100). A new XPS parameter has been developed to characterize the metal/Si interface state, in particular, broadening of the interface induced by the sputter deposition. For the case of evaporated layers, it indicates that Au/Si and Cu/Si interfaces are diffuse, while Ag/Si and Al/Si interfaces are abrupt. Atomic force microscopy has revealed that sputter deposition reduces the tendency to form metal islands, characteristic of some overlayer/substrate systems such as Ag/Si. Our experiments have illustrated the role of two "new" parameters which lead to better knowledge and control of the sputter deposition process, namely the ion masses and the sample position relative to that of the target position. In the scientific literature, the value of the critical thickness, d_{rm c} , for reaction between Au and Si is still a controversial issue, probably on account of calibration problems. By using newly observed XPS discontinuities, corresponding to the completion of the first and second Au monolayers, we have been able to resolve this problem, and thereby precisely evaluate the critical thickness, d_ {rm c} = 2 ML. We obtained various new information about the Au/Si interface using complementary methods (XPD, XPS, TEM, AFM, etc.) information from which we developed a new model of the Au/Si interface; this so called "cluster model" correlates the observed overlayer structural transition with the beginning of the reaction between Au and Si. It suggests that reconstruction of the overlayer at 2 ML thickness activates the reaction between Si and Au (Si-Si bonds disruption, followed by Si outdiffusion). This model seems to be the only one capable of explaining the difference in reactivity between Au/Si and Ag/Si interfaces. (Abstract shortened by UMI.).

Gold Nanoparticles for Diagnostics: Advances towards Points of Care

PubMed Central

Cordeiro, Mílton; Ferreira Carlos, Fábio; Pedrosa, Pedro; Lopez, António; Baptista, Pedro Viana

2016-01-01

The remarkable physicochemical properties of gold nanoparticles (AuNPs) have prompted developments in the exploration of biomolecular interactions with AuNP-containing systems, in particular for biomedical applications in diagnostics. These systems show great promise in improving sensitivity, ease of operation and portability. Despite this endeavor, most platforms have yet to reach maturity and make their way into clinics or points of care (POC). Here, we present an overview of emerging and available molecular diagnostics using AuNPs for biomedical sensing that are currently being translated to the clinical setting. PMID:27879660

Novel photocatalyst gold nanoparticles with dumbbell-like structure and their superiorly photocatalytic performance for ammonia borane hydrolysis

NASA Astrophysics Data System (ADS)

Zhu, Mingyun; Dai, Yunqian; Fu, Wanlin; Wu, Yanan; Zou, Xixi; You, Tengye; Sun, Yueming

2018-04-01

Gold nanoparticles (Au NPs) have attracted remarkable research interest in heterogeneous catalysis due to their unique physical and chemical properties. However, only small-sized Au NPs (<7 nm) exhibit promising catalytic activity. In this work, dumbbell-like Au NPs (D-Au NPs) with an average size of 37 × 11 nm were prepared by a secondary seed-mediated growth method to serve as novel photocatalysts for ammonia borane (AB) hydrolysis in a solution with a specific pH value. Our results demonstrate that (i) the strengthened localized surface plasmon resonance (LSPR) compensation effect could effectively remedy the loss of catalytic activity resulting from the size enlarging of D-Au NPs, proved by the observation that the heating power of a single Au nanoparticle (Ps) and turnover frequency of AB molecules within 10 min of D-Au NPs are 52.5 and 3.89 times higher, respectively, than those of spherical Au NPs; (ii) the extinction coefficient and Ps of D-Au NPs are almost 2.72 and 2.42 times as high, respectively, as those of rod-like Au NPs, demonstrating the promoting structure-property relationship of the dumbbell-like structure; (iii) when the pH value of the AB solution was lower than 6.0, the hydrolysis rate was highly promoted, indicating that H+ ions play an active role in the hydrolysis process. This work greatly extends the application of noble metals and provides a new insight into AB hydrolysis.

Recent Advances in Laser-Ablative Synthesis of Bare Au and Si Nanoparticles and Assessment of Their Prospects for Tissue Engineering Applications.

PubMed

Al-Kattan, Ahmed; Nirwan, Viraj P; Popov, Anton; Ryabchikov, Yury V; Tselikov, Gleb; Sentis, Marc; Fahmi, Amir; Kabashin, Andrei V

2018-05-24

Driven by surface cleanness and unique physical, optical and chemical properties, bare (ligand-free) laser-synthesized nanoparticles (NPs) are now in the focus of interest as promising materials for the development of advanced biomedical platforms related to biosensing, bioimaging and therapeutic drug delivery. We recently achieved significant progress in the synthesis of bare gold (Au) and silicon (Si) NPs and their testing in biomedical tasks, including cancer imaging and therapy, biofuel cells, etc. We also showed that these nanomaterials can be excellent candidates for tissue engineering applications. This review is aimed at the description of our recent progress in laser synthesis of bare Si and Au NPs and their testing as functional modules (additives) in innovative scaffold platforms intended for tissue engineering tasks.

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.

Improving the contact resistance at low force using gold coated carbon nanotube surfaces

NASA Astrophysics Data System (ADS)

McBride, J. W.; Yunus, E. M.; Spearing, S. M.

2010-04-01

Investigations to determine the electrical contact performance under repeated cycles at low force conditions for carbon-nanotube (CNT) coated surfaces were performed. The surfaces under investigation consisted of multi-walled CNT synthesized on a silicon substrate and coated with a gold film. These planar surfaces were mounted on the tip of a PZT actuator and contacted with a plated Au hemispherical probe. The dynamic applied force used was 1 mN. The contact resistance (Rc) of these surfaces was investigated with the applied force and with repeated loading cycles performed for stability testing. The surfaces were compared with a reference Au-Au contact under the same experimental conditions. This initial study shows the potential for the application of gold coated CNT surfaces as an interface in low force electrical contact applications.

Ultrasensitive luminol electrochemiluminescence for protein detection based on in situ generated hydrogen peroxide as coreactant with glucose oxidase anchored AuNPs@MWCNTs labeling.

PubMed

Cao, Yaling; Yuan, Ruo; Chai, Yaqin; Mao, Li; Niu, Huan; Liu, Huijing; Zhuo, Ying

2012-01-15

In this study, an ultrasensitive luminol electrochemiluminescence (ECL) immunosensor was constructed using carboxyl group functionalized multi-walled carbon nanotubes (MWCNTs) as platform and glucose oxidase (GOD) supported on Au nanoparticles (AuNPs) decorated MWCNTs (AuNPs@MWCNTs-GOD) as labels. Firstly, using poly(ethylenimine) (PEI) as linkage reagents, AuNPs@MWCNTs were prepared and introduced for binding of the secondary antibody (Ab(2)) and glucose oxidase (GOD) with high loading amount and good biological activity due to the improved surface area of AuNPs@MWCNTs and excellent biocompatibility of AuNPs. Then the GOD and Ab(2) labeled AuNPs@MWCNTs were linked to the electrode surface via sandwich immunoreactions. These localized GOD and AuNPs amplified luminol ECL signals dramatically, which was achieved by efficient catalysis of the GOD and AuNPs towards the oxidation of glucose to in situ generate improved amount of hydrogen peroxide (H(2)O(2)) as coreactant and the enhancement of AuNPs to the ECL reaction of luminol-H(2)O(2). The experimental results demonstrated that the proposed immunosensor exhibited sensitive and stable response for the detection of α-1-fetoprotein (AFP), ranging from 0.0001 to 80 ng mL(-1) with a limit of detection down to 0.03 pg mL(-1) (S/N=3). With excellent stability, sensitivity, selectivity and simplicity, the proposed luminol ECL immunosensor showed great potential in clinical applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Rough gold films as broadband absorbers for plasmonic enhancement of TiO2 photocurrent over 400–800 nm

PubMed Central

Tan, Furui; Li, Tenghao; Wang, Ning; Lai, Sin Ki; Tsoi, Chi Chung; Yu, Weixing; Zhang, Xuming

2016-01-01

Recent years have witnessed an increasing interest in highly-efficient absorbers of visible light for the conversion of solar energy into electrochemical energy. This study presents a TiO2-Au bilayer that consists of a rough Au film under a TiO2 film, which aims to enhance the photocurrent of TiO2 over the whole visible region and may be the first attempt to use rough Au films to sensitize TiO2. Experiments show that the bilayer structure gives the optimal optical and photoelectrochemical performance when the TiO2 layer is 30 nm thick and the Au film is 100 nm, measuring the absorption 80–90% over 400–800 nm and the photocurrent intensity of 15 μA·cm−2, much better than those of the TiO2-AuNP hybrid (i.e., Au nanoparticle covered by the TiO2 film) and the bare TiO2 film. The superior properties of the TiO2-Au bilayer can be attributed to the rough Au film as the plasmonic visible-light sensitizer and the photoactive TiO2 film as the electron accepter. As the Au film is fully covered by the TiO2 film, the TiO2-Au bilayer avoids the photocorrosion and leakage of Au materials and is expected to be stable for long-term operation, making it an excellent photoelectrode for the conversion of solar energy into electrochemical energy in the applications of water splitting, photocatalysis and photosynthesis. PMID:27608836

Charge optimized many body (COMB) potentials for Pt and Au.

PubMed

Antony, A C; Akhade, S A; Lu, Z; Liang, T; Janik, M J; Phillpot, S R; Sinnott, S B

2017-06-07

Interatomic potentials for Pt and Au are developed within the third generation charge optimized many-body (COMB3) formalism. The potentials are capable of reproducing phase order, lattice constants, and elastic constants of Pt and Au systems as experimentally measured or calculated by density functional theory. We also fit defect formation energies, surface energies and stacking fault energies for Pt and Au metals. The resulting potentials are used to map a 2D contour of the gamma surface and simulate the tensile test of 16-grain polycrystalline Pt and Au structures at 300 K. The stress-strain behaviour is investigated and the primary slip systems {1 1 1}〈1 [Formula: see text] 0〉 are identified. In addition, we perform high temperature (1800 K for Au and 2300 K for Pt) molecular dynamics simulations of 30 nm Pt and Au truncated octahedron nanoparticles and examine morphological changes of each particle. We further calculate the activation energy barrier for surface diffusion during simulations of several nanoseconds and report energies of [Formula: see text] eV for Pt and [Formula: see text] eV for Au. This initial parameterization and application of the Pt and Au potentials demonstrates a starting point for the extension of these potentials to multicomponent systems within the COMB3 framework.

Effect of Size and Surface Charge of Gold Nanoparticles on their Skin Permeability: A Molecular Dynamics Study

PubMed Central

Gupta, Rakesh; Rai, Beena

2017-01-01

Molecular level understanding of permeation of nanoparticles through human skin establishes the basis for development of novel transdermal drug delivery systems and design and formulation of cosmetics. Recent experiments suggest that surface coated nano-sized gold nanoparticles (AuNPs) can penetrate the rat and human skin. However, the mechanisms by which these AuNPs penetrate are not well understood. In this study, we have carried out coarse grained molecular dynamics simulations to explore the permeation of dodecanethiol coated neutral hydrophobic AuNPs of different sizes (2–5 nm) and surface charges (cationic and anionic) through the model skin lipid membrane. The results indicate that the neutral hydrophobic AuNPs disrupted the bilayer and entered in it with in ~200 ns, while charged AuNPs were adsorbed on the bilayer headgroup. The permeation free energy calculation revealed that at the head group of the bilayer, a very small barrier existed for neutral hydrophobic AuNP while a free energy minimum was observed for charged AuNPs. The permeability was maximum for neutral 2 nm gold nanoparticle (AuNP) and minimum for 3 nm cationic AuNP. The obtained results are aligned with recent experimental findings. This study would be helpful in designing customized nanoparticles for cosmetic and transdermal drug delivery application. PMID:28349970

Green synthesis of gold nanoparticles using a cheap Sphaeranthus indicus extract: Impact on plant cells and the aquatic crustacean Artemia nauplii.

PubMed

Balalakshmi, Chinnasamy; Gopinath, Kasi; Govindarajan, Marimuthu; Lokesh, Ravi; Arumugam, Ayyakannu; Alharbi, Naiyf S; Kadaikunnan, Shine; Khaled, Jamal M; Benelli, Giovanni

2017-08-01

The impact of green-fabricated gold nanoparticles on plant cells and non-target aquatic species is scarcely studied. In this research, we reported an environment friendly technique for the synthesis of gold nanoparticles (Au NPs) using the Sphaeranthus indicus leaf extract. The formation of the metal NPs was characterized by UV-Visible and FT-IR spectroscopy, XRD, SEM and TEM analyses. The UV-Visible spectra of Au NPs showed a surface plasmon resonance peak at 531nm. FT-IR analysis indicated functional bio-molecules associated with Au NPs formation. The crystalline nature of Au nanoparticles was confirmed by their XRD diffraction pattern. TEM revealed the spherical shape with a mean particle size of 25nm. Au NPs was tested at 0, 1, 3, 5, 7 and 10% doses in mitotic cell division assays, pollen germination experiments, and in vivo toxicity trials against the aquatic crustacean Artemia nauplii. Au NPs did not show any toxic effects on plant cells and aquatic invertebrates. Notably, Au NPs promoted mitotic cell division in Allium cepa root tip cells and germination of Gloriosa superba pollen grains. Au NPs showed no mortality on A. nauplii, all the tested animals showed 100% survivability. Therefore, these Au NPs have potential applications in the development of pollen germination media and plant tissue culture. Copyright © 2017 Elsevier B.V. All rights reserved.

Fabrication of Graphene and AuNP Core Polyaniline Shell Nanocomposites as Multifunctional Theranostic Platforms for SERS Real-time Monitoring and Chemo-photothermal Therapy

PubMed Central

Chen, Haolin; Liu, Zhiming; Li, Songyang; Su, Chengkang; Qiu, Xuejun; Zhong, Huiqing; Guo, Zhouyi

2016-01-01

In this work, novel theranostic platforms based on graphene oxide and AuNP core polyaniline shell (GO-Au@PANI) nanocomposites are fabricated for simultaneous SERS imaging and chemo-photothermal therapy. PANI, a new NIR photothermal therapy agent with strong NIR absorption, outstanding stability and low cytotoxicity is decorated on AuNPs by one-pot oxidative polymerization, then the Au@PANI core-shell nanoparticles are attached to the graphene oxide (GO) sheet via π-π stacking and electrostatic interaction. The obtained GO-Au@PANI nanohybirds exhibit excellent NIR photothermal transduction efficiency and ultrahigh drug-loading capacity. The nanocomposites can also serve as novel NIR SERS probes utilizing the intense SERS signals of PANI. Rapid SERS imaging of cancer cells is achieved using this ultrasensitive nanoprobe. GO-Au@PANI also reveals good capability of drug delivery with the DOX-loading efficiency of 189.2% and sensitive NIR/pH-responsive DOX release. The intracellular real-time drug release dynamics from the nanocomposites is monitored by SERS-fluorescence dual mode imaging. Finally, chemo-photothermal ablation of cancer cells is carried out in vitro and in vivo using GO-Au@PANI as high-performance chemo-photothermal therapeutic nanoagent. The theranostic applications of GO-Au@PANI endow it with great potential for personalized and precise cancer medicine. PMID:27279904

In Vitro Study of Influence of Au Nanoparticles on HT29 and SPEV Cell Lines

NASA Astrophysics Data System (ADS)

Pavlovich, Elena; Volkova, Nataliia; Yakymchuk, Elena; Perepelitsyna, Olena; Sydorenko, Michail; Goltsev, Anatoliy

2017-08-01

Cell culture models are excellent tools for potential toxicity of nanoparticles and fundamental investigations in cancer research. Thus, information about AuNP potential toxicity and effects on human health is necessary for the use of nanomaterials in clinical settings. The aim of our research is to examine the effects of AuNPs on the epithelial origin cell lines: continuous and oncogenic. Embryonic porcine kidney epithelial inoculated (SPEV) cell line and colorectal carcinoma cell line (HT29) were used. In the test cultures, the cell proliferation, necrosis/apoptosis, and multicellular spheroids generation were evaluated. We demonstrated that AuNP concentrations of 6-12 μg/ml reduced the proliferation of SPEV and HT29 cells and increased the cell number at early and late stages of apoptosis and necrosis. It was shown that small concentrations of AuNPs (1-3 μg/ml) stimulate multicellular spheroid formation by HT29 and SPEV cells. However, higher AuNP concentrations (6-12 μg/ml) had both cytotoxic and anti-cohesive effects on cell in suspension. The large sensitiveness to the action of AuNPs was shown by the line of HT29 (6 μg/ml) as compared to the SPEV cells (12 μg/ml). This experimental study of the effect of AuNPs on SPEV and HT29 cell lines will justify their further application in AuNP-mediated anticancer treatment.

Comparative study of alkylthiols and alkylamines for the phase transfer of gold nanoparticles from an aqueous phase to n-hexane.

PubMed

Li, Lingxiangyu; Leopold, Kerstin; Schuster, Michael

2013-05-01

An efficient ligand-assisted phase transfer method has been developed to transfer gold nanoparticles (Au-NPs, d: 5-25 nm) from an aqueous solution to n-hexane. Four different ligands, namely 1-dodecanethiol (DDT), 1-octadecanethiol (ODT), dodecylamine (DDA), and octadecylamine (ODA) were investigated, and DDT was found to be the most efficient ligand. It appears that the molar ratio of DDT to Au-NPs is a critical factor affecting the transfer efficiency, and 270-310 is found to be the optimum range, under which the transfer efficiency is >96%. Moreover, the DDT-assisted phase transfer can preserve the shape and size of the Au-NPs, which was confirmed by UV-vis spectra and transmission electron microscopy (TEM). Additionally, the transferred Au-NPs still can be well dispersed in the n-hexane phase and remain stable for at least 2 weeks. On the other hand, the ODT-, DDA-, and ODA-assisted phase transfer is fraught with problems either related to transfer efficiency or NPs aggregation. Overall, the DDT-assisted phase transfer of Au-NPs provides a rapid and efficient method to recover Au-NPs from an aqueous solution to n-hexane. Copyright © 2013 Elsevier Inc. All rights reserved.

High Sensitivity and High Detection Specificity of Gold-Nanoparticle-Grafted Nanostructured Silicon Mass Spectrometry for Glucose Analysis.

PubMed

Tsao, Chia-Wen; Yang, Zhi-Jie

2015-10-14

Desorption/ionization on silicon (DIOS) is a high-performance matrix-free mass spectrometry (MS) analysis method that involves using silicon nanostructures as a matrix for MS desorption/ionization. In this study, gold nanoparticles grafted onto a nanostructured silicon (AuNPs-nSi) surface were demonstrated as a DIOS-MS analysis approach with high sensitivity and high detection specificity for glucose detection. A glucose sample deposited on the AuNPs-nSi surface was directly catalyzed to negatively charged gluconic acid molecules on a single AuNPs-nSi chip for MS analysis. The AuNPs-nSi surface was fabricated using two electroless deposition steps and one electroless etching step. The effects of the electroless fabrication parameters on the glucose detection efficiency were evaluated. Practical application of AuNPs-nSi MS glucose analysis in urine samples was also demonstrated in this study.

Theophylline-assisted, eco-friendly synthesis of PtAu nanospheres at reduced graphene oxide with enhanced catalytic activity towards Cr(VI) reduction.

PubMed

Hu, Ling-Ya; Chen, Li-Xian; Liu, Meng-Ting; Wang, Ai-Jun; Wu, Lan-Ju; Feng, Jiu-Ju

2017-05-01

Theophylline as a naturally alkaloid is commonly employed to treat asthma and chronic obstructive pulmonary disorder. Herein, a facile theophylline-assisted green approach was firstly developed for synthesis of PtAu nanospheres/reduced graphene oxide (PtAu NSs/rGO), without any surfactant, polymer, or seed involved. The obtained nanocomposites were applied for the catalytic reduction and removal of highly toxic chromium (VI) using formic acid as a model reductant at 50°C, showing the significantly enhanced catalytic activity and improved recyclability when compared with commercial Pt/C (50%) and home-made Au nanocrystals supported rGO (Au NCs/rGO). It demonstrates great potential applications of the catalyst in wastewater treatment and environmental protection. The eco-friendly route provides a new platform to fabricate other catalysts with enhanced catalytic activity. Copyright © 2016 Elsevier Inc. All rights reserved.

Comparative study of proteasome inhibitory, synergistic antibacterial, synergistic anticandidal, and antioxidant activities of gold nanoparticles biosynthesized using fruit waste materials.

PubMed

Patra, Jayanta Kumar; Baek, Kwang-Hyun

The aim of this study was to compare the biological synthesis of gold nanoparticles (AuNPs) generated using the aqueous extracts of outer oriental melon peel (OMP) and peach. The synthesized OMP-AuNPs and peach extract (PE)-AuNPs were characterized by ultraviolet-visible spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis, X-ray powder diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The surface plasmon resonance spectra were obtained at 545 nm and 540 nm for OMP-AuNPs and PE-AuNPs, respectively. The estimated absolute crystallite size of the synthesized AuNPs was calculated to be 78.11 nm for OMP-AuNPs and 39.90 nm for PE-AuNPs based on the Scherer equation of the X-ray powder diffraction peaks. Fourier transform infrared spectroscopy results revealed the involvement of bioactive compounds present in OMP and peach extracts in the synthesis and stabilization of synthesized AuNPs. Both the OMP-AuNPs and PE-AuNPs showed a strong antibacterial synergistic activity when combined with kanamycin (9.38-20.45 mm inhibition zones) and rifampicin (9.52-25.23 mm inhibition zones), and they also exerted a strong synergistic anticandidal activity (10.09-15.47 mm inhibition zones) when combined with amphotericin B against five pathogenic Candida species. Both the OMP-AuNPs and PE-AuNPs exhibited a strong antioxidant potential in terms of 1,1-diphenyl-2-picrylhydraxyl radical scavenging, nitric oxide scavenging, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging, and a reducing power, along with a strong proteasome inhibitory potential that could be useful in cancer drug delivery and cancer treatments. The PE-AuNPs showed comparatively higher activity than OMP-AuNPs, which could be attributed to the presence of rich bioactive compounds in the PE that acted as reducing and capping agents in the synthesis of PE-AuNPs. Overall, the results of the current investigation highlighted a novel green technology for the synthesis of AuNPs using food waste materials and their potential applications in the biomedical, pharmaceutical, and cosmetic industries.

Luminescent gold nanoparticles for bioimaging

NASA Astrophysics Data System (ADS)

Zhou, Chen

Inorganic nanoparticles (NPs) with tunable and diverse material properties hold great potential as contrast agents for better disease management. Over the past decades, luminescent gold nanoparticles (AuNPs) with intrinsic emissions ranging from the visible to the near infrared have been synthesized and emerge as a new class of fluorophores for bioimaging. This dissertation aims to fundamentally understand the structure-property relationships in luminescent AuNPs and apply them as contrast agents to address some critical challenges in bioimaging at both the in vitro and in vivo level. In Chapter 2, we described the synthesized ~20 nm polycrystalline AuNPs (pAuNPs), which successfully integrated and enhanced plasmonic and fluorescence properties into a single AuNP through the grain size effect. The combination of these properties in one NP enabled AuNPs to serve as a multimodal contrast agent for in vitro optical microscopic imaging, making it possible to develop correlative microscopic imaging techniques. In Chapters 3-5, we proposed a feasible approach to optimize the in vivo kinetics and clearance profile of nanoprobes for multimodality in vivo bioimaging applications by using straightforward surface chemistry with luminescent AuNPs as a model. Luminescent glutathione-coated AuNPs of ~2 nm were synthesized. Investigation of the biodistribution showed that these glutathione-coated AuNPs (GS-AuNPs) exhibit stealthiness to the reticuloendothelial system (RES) organs and efficient renal clearance, with only 3.7+/-1.9% and 0.3+/-0.1% accumulating in the liver and spleen, and over 65% of the injection dose cleared out via the urine within the first 72 hours. In addition, ~2.5 nm NIR-emitting radioactive glutathione-coated [198Au]AuNPs (GS-[198Au]AuNPs) were synthesized for further evaluation of the pharmacokinetic profile of GS-AuNPs and potential multimodal imaging. The results showed that the GS-[198Au]AuNPs behave like small-molecule contrast agents in pharmacokinetics while remaining renal clearable. With a rapid distribution half-life and a desirable elimination half-life, these NPs are highly promising for single-photon emission computed tomography (SPECT) and fluorescence dual-modality imaging.

Artificial phototropism based on a photo-thermo-responsive hydrogel

NASA Astrophysics Data System (ADS)

Gopalakrishna, Hamsini

Solar energy is leading in renewable energy sources and the aspects surrounding the efforts to harvest light are gaining importance. One such aspect is increasing the light absorption, where heliotropism comes into play. Heliotropism, the ability to track the sun across the sky, can be integrated with solar cells for more efficient photon collection and other optoelectronic systems. Inspired by plants, which optimize incident sunlight in nature, several researchers have made artificial heliotropic and phototropic systems. This project aims to design, synthesize and characterize a material system and evaluate its application in a phototropic system. A gold nanoparticle (Au NP) incorporated poly(N-isopropylacrylamide) (PNIPAAm) hydrogel was synthesized as a photo-thermo-responsive material in our phototropic system. The Au NPs generate heat from the incident via plasmonic resonance to induce a volume phase change of the thermo-responsive hydrogel PNIPAAm. PNIPAAm shrinks or swells at temperature above or below 32°C. Upon irradiation, the Au NP-PNIPAAm micropillar actuates, specifically bending toward the incident light and precisely following the varying incident angle. Swelling ratio tests, bending angle tests with a static incident light and bending tests with varying angles were carried out on hydrogel samples with varying Au NP concentrations. Swelling ratios ranging from 1.45 to 2.9 were recorded for pure hydrogel samples and samples with very low Au NP concentrations. Swelling ratios of 2.41 and 3.37 were calculated for samples with low and high concentrations of Au NPs, respectively. A bending of up to 88° was observed in Au NP-hydrogel pillars with a low Au NP concentration with a 90° incident angle. The light tracking performance was assessed by the slope of the pillar Bending angle (response angle) vs. Incident light angle plot. A slope of 1 indicates ideal tracking with top of the pillar being normal to the incident light, maximizing the photon absorption. Slopes of 0.82 and 0.56 were observed for the low and high Au NP concentration samples. The rapid and precise incident light tracking of our system has shown the promise in phototropic applications.

Use of gold nanoparticles to detect water uptake in vascular plants.

PubMed

Hwang, Bae Geun; Ahn, Sungsook; Lee, Sang Joon

2014-01-01

Direct visualization of water-conducting pathways and sap flows in xylem vessels is important for understanding the physiology of vascular plants and their sap ascent. Gold nanoparticles (AuNPs) combined with synchrotron X-ray imaging technique is a new promising tool for investigating plant hydraulics in opaque xylem vessels of vascular plants. However, in practical applications of AuNPs for real-time quantitative visualization of sap flows, their interaction with a vascular network needs to be verified in advance. In this study, the effect of AuNPs on the water-refilling function of xylem vessels is experimentally investigated with three monocot species. Discrepancy in the water uptakes starts to appear at about 20 min to 40 min after the supply of AuNP solution to the test plant by the possible gradual accumulation of AuNPs on the internal structures of vasculature. However conclusively, it is observed that the water-refilling speeds in individual xylem vessels are virtually unaffected by hydrophilically surface-modified AuNPs (diameter ∼20 nm). Therefore, the AuNPs can be effectively used as flow tracers in the xylem vessels in the first 20∼30 min without any physiological barrier. As a result, AuNPs are found to be useful for visualizing various fluid dynamic phenomena occurring in vascular plants.

Enhanced NO2 sensing characteristics of Au modified porous silicon/thorn-sphere-like tungsten oxide composites

NASA Astrophysics Data System (ADS)

Yuan, Lin; Hu, Ming; Wei, Yulong; Ma, Wenfeng

2016-12-01

The thorn-sphere-like tungsten oxide (WO3) made up by 1D nanorods has been successfully synthesized through hydrothermal method on the Au-modified porous silicon (PS) substrates with seed-layer induction. By using XRD, EDS, FESEM and TEM techniques, we tested and verified that the crystal structure and morphology evolution of WO3 hierarchical nanostructure on the Au-modified PS strongly depend on the Au-sputtering time and hydrothermal reaction time. In addition, by comparing the NO2-sensing properties of the prepared products, we found that the 10 s-Au decorated PS/WO3-3 h (sputtering Au for 10 s and hydrothermal reaction for 3 h) composites sensor behaving as a typical p-type semiconductor and operating at room temperature (RT) exhibits high sensitivity and response characteristics even to ppb-level NO2, which makes this kind of sensor a competitive candidate for NO2-sensing applications. Moreover, the enhanced response may not only due to the high specific surface area but the Au nanoparticles acting as promoters for the spillover effect and forming metal-semiconductor heterojunctions with the PS and WO3. The transmission of electrons and holes in the heterogeneous interface generated among PS, WO3 and Au is proposed to illustrate the p-type response mechanism.

Dynamic imaging of a single gold nanoparticle in liquid irradiated by off-resonance femtosecond laser.

PubMed

Boutopoulos, Christos; Hatef, Ali; Fortin-Deschênes, Matthieu; Meunier, Michel

2015-07-21

Plasmonic nanoparticles can lead to extreme confinement of the light in the near field. This unique ability of plasmonic nanoparticles can be used to generate nanobubbles in liquid. In this work, we demonstrate with single-particle monitoring that 100 nm gold nanoparticles (AuNPs) irradiated by off-resonance femtosecond (fs) laser in the tissue therapeutic optical window (λ = 800 nm), can act as a durable nanolenses in liquid and provoke nanocavitation while remaining intact. We have employed combined ultrafast shadowgraphic imaging, in situ dark field imaging and dynamic tracking of AuNP Brownian motion to ensure the study of individual AuNPs/nanolenses under multiple fs laser pulses. We demonstrate that 100 nm AuNPs can generate multiple, highly confined (radius down to 550 nm) and transient (life time < 50 ns) nanobubbles. The latter is of significant importance for future development of in vivo AuNP-assisted laser nanosurgery and theranostic applications, where AuNP fragmentation should be avoided to prevent side effects, such as cytotoxicity and immune system's response. The experimental results have been correlated with theoretical modeling to provide an insight to the AuNP-safe cavitation mechanism as well as to investigate the deformation mechanism of the AuNPs at high laser fluences.

Green preparation of gold nanoparticles with Tremella fuciformis for surface enhanced Raman scattering sensing

NASA Astrophysics Data System (ADS)

Tang, Bin; Liu, Jun; Fan, Linpeng; Li, Daili; Chen, Xinzhu; Zhou, Ji; Li, Jingliang

2018-01-01

A simple in-situ synthesis method was developed to fabricate complex of Tremella fuciformis (TF) and gold nanoparticles (Au NPs). TF, one of the most popular fungi in the cuisine and medicine, acted as a biomass reducing agent and scaffold in the preparation of Au NPs. The intensities of the localized surface plasmon resonance (LSPR) of the complex of TF and Au NPs (Au@TFs) increased as the complex shrunk due to drying. The textures of TF prevent the aggregation of Au NPs during the drying process. The TFs show strong adsorption capacity for cationic dyes. It is suggested that the adsorption of the dyes onto TFs are achieved through electrostatic interactions between the TF and the dyes. Kinetics studies indicated that adsorption process could be well described by a pseudo-second-order model. Furthermore, the as-prepared Au@TFs were used as surface enhanced Raman scattering (SERS) substrates for analyzing trace dye molecules. The shrinkage of the TFs caused by drying concentrated dyes on their fruiting bodies, which led to the enhancement of Raman signals of dyes. The Au NPs on TF further enhanced the Raman signals. In-situ synthesis of Au NPs on TF may promote the applications of fungus materials in optical sensing of targets.

Size-dependent longitudinal plasmon resonance wavelength and extraordinary scattering properties of Au nanobipyramids.

PubMed

Wang, Wenhao; Yu, Peng; Zhong, Zhiqin; Tong, Xin; Liu, Tianji; Li, Yanbo; Ashalley, Eric; Chen, Huanyang; Wu, Jiang; Wang, Zhiming

2018-08-31

Au nanobipyramids (NBPs) with sharp tips and narrow plasmon linewidths are ideal candidates for plasmonic applications. In this paper, we investigated the influencing factors of longitudinal plasmon resonance wavelength (LPRW) and scattering properties of single Au NBP by simulation. Compared with the volume, we establish the aspect ratio (length/width) as the dominant factor that affects the LPRW of Au NBPs. Plasmonic nanoparticles have been widely used for light-trapping enhancement in photovoltaics. To give a profound understanding of the superior light harvesting properties of Au NBPs, the near-field localization effect and far-field scattering mechanism of Au NBPs were investigated. Under the light injection at LPRW, the tip area shows near-field enhancement and the maximum scattering intensity appears on the side area of the waist owing to the remarkable optical absorption near the tips. Additionally, we confirm the fraction of light scattered into the substrate and angular distribution of the light scattered by the Au NBPs. The fraction of light scattered into the substrate reaches up to 97% from 400-1100 nm and preserves a broadband spectrum. This suggests that the NBP has a predominant forward scattering and reduced backward scattering. The excellent plasmonic scattering properties of Au NBPs are promising in photovoltaic devices and photothermal therapy.

Required Equipment for Photo-Switchable Donor-Acceptor (D-A) Dyad Interfacial Self-Assembled Monolayers for Organic Photovoltaic Cells

DTIC Science & Technology

2014-01-24

Interfacial Tuning via Electron-Blocking/Hole-Transport Layers and Indium Tin Oxide Surface Treatment in Bulk- Heterojunction Organic Photovoltaic Cells...devices Figure 3 shows the compounds we prepared to assemble on gold (Au) surfaces. Results of TPA-C60 dyads (1 and 2) self-assembled on Au electrodes...surface hydroxyl groups, respectively, we decided to prepare compounds 5-7 to attach as SAMs, see Figure 5. Difficulties and unexpected problems

Cooperative plasmonic effect of Ag and Au nanoparticles on enhancing performance of polymer solar cells.

PubMed

Lu, Luyao; Luo, Zhiqiang; Xu, Tao; Yu, Luping

2013-01-09

This article describes a cooperative plasmonic effect on improving the performance of polymer bulk heterojunction solar cells. When mixed Ag and Au nanoparticles are incorporated into the anode buffer layer, dual nanoparticles show superior behavior on enhancing light absorption in comparison with single nanoparticles, which led to the realization of a polymer solar cell with a power conversion efficiency of 8.67%, accounting for a 20% enhancement. The cooperative plasmonic effect aroused from dual resonance enhancement of two different nanoparticles. The idea was further unraveled by comparing Au nanorods with Au nanoparticles for solar cell application. Detailed studies shed light into the influence of plasmonic nanostructures on exciton generation, dissociation, and charge recombination and transport inside thin film devices.

Multifunctional Gold Nanostars for Molecular Imaging and Cancer Therapy

NASA Astrophysics Data System (ADS)

Liu, Yang; Yuan, Hsiangkuo; Fales, Andrew; Register, Janna; Vo-Dinh, Tuan

2015-08-01

Plasmonics-active gold nanoparticles offer excellent potential in molecular imaging and cancer therapy. Among them, gold nanostars (AuNS) exhibit cross-platform flexibility as multimodal contrast agents for macroscopic X-ray computer tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), as well as nanoprobes for photoacoustic tomography (PAT), two-photon photoluminescence (TPL) and surface-enhanced Raman spectroscopy (SERS). Their surfactant-free surface enables versatile functionalization to enhance cancer targeting, and allow triggered drug release. AuNS can also be used as an efficient platform for drug carrying, photothermal therapy, and photodynamic therapy. This review paper presents the latest progress regarding AuNS as a promising nanoplatform for cancer nanotheranostics. Future research directions with AuNS for biomedical applications will also be discussed.

Au nanocage/SiO2 saturable absorber for passive Q-switching Yb-doped fiber laser

NASA Astrophysics Data System (ADS)

Bai, Jinxi; Li, Ping; Guo, Lei; Zhang, Baitao; Hu, Qiongyu; Wang, Lili; Liu, Binghai; Chen, Xiaohan

2018-05-01

Au nanocages/SiO2 (Au-NCs/SiO2) with the surface plasmon resonance peak at 1060 nm were fabricated and experimentally exploited as the saturable absorber in an all-fiber passively Q-switched ytterbium-doped fiber laser for the first time. Under a pump power of 440 mW, the average output power of 10.6 mW was obtained with the pulse duration 1.4 µs and the repetition rate of 126.9 kHz at 1060.5 nm with the 3 dB spectral width of 0.131 nm. The results indicate that Au-NCs/SiO2 exhibits the potential for applications in the field of pulse lasers.

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.

In Situ Synthesis of Reduced Graphene Oxide and Gold Nanocomposites for Nanoelectronics and Biosensing.

PubMed

Dong, Xiaochen; Huang, Wei; Chen, Peng

2011-12-01

In this study, an in situ chemical synthesis approach has been developed to prepare graphene-Au nanocomposites from chemically reduced graphene oxide (rGO) in aqueous media. UV-Vis absorption, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy were used to demonstrate the successful attachment of Au nanoparticles to graphene sheets. Configured as field-effect transistors (FETs), the as-synthesized single-layered rGO-Au nanocomposites exhibit higher hole mobility and conductance when compared to the rGO sheets, promising its applications in nanoelectronics. Furthermore, we demonstrate that the rGO-Au FETs are able to label-freely detect DNA hybridization with high sensitivity, indicating its potentials in nanoelectronic biosensing.

In Situ Synthesis of Reduced Graphene Oxide and Gold Nanocomposites for Nanoelectronics and Biosensing

PubMed Central

2011-01-01

In this study, an in situ chemical synthesis approach has been developed to prepare graphene–Au nanocomposites from chemically reduced graphene oxide (rGO) in aqueous media. UV–Vis absorption, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy were used to demonstrate the successful attachment of Au nanoparticles to graphene sheets. Configured as field-effect transistors (FETs), the as-synthesized single-layered rGO-Au nanocomposites exhibit higher hole mobility and conductance when compared to the rGO sheets, promising its applications in nanoelectronics. Furthermore, we demonstrate that the rGO-Au FETs are able to label-freely detect DNA hybridization with high sensitivity, indicating its potentials in nanoelectronic biosensing. PMID:27502682

Ab initio simulations of scanning-tunneling-microscope images with embedding techniques and application to C58-dimers on Au(111).

PubMed

Wilhelm, Jan; Walz, Michael; Stendel, Melanie; Bagrets, Alexei; Evers, Ferdinand

2013-05-14

We present a modification of the standard electron transport methodology based on the (non-equilibrium) Green's function formalism to efficiently simulate STM-images. The novel feature of this method is that it employs an effective embedding technique that allows us to extrapolate properties of metal substrates with adsorbed molecules from quantum-chemical cluster calculations. To illustrate the potential of this approach, we present an application to STM-images of C58-dimers immobilized on Au(111)-surfaces that is motivated by recent experiments.

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.

Surface plasmon resonance-induced photocatalysis by Au nanoparticles decorated mesoporous g-C{sub 3}N{sub 4} nanosheets under direct sunlight irradiation

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

Tonda, Surendar; Kumar, Santosh; Shanker, Vishnu, E-mail: vishnu@nitw.ac.in

Highlights: • The Au/mp-g-C{sub 3}N{sub 4} was synthesized via a template-free and green in situ strategy. • Au/mp-g-C{sub 3}N{sub 4} nanosheets possesses high surface area and porous structure. • Au/mp-g-C{sub 3}N{sub 4} showed dramatic photocurrent response and photocatalytic activity. • The high performance is due to SPR of Au and mesoporous structure. • Au/mp-g-C{sub 3}N{sub 4} nanosheets exhibited high photostability. - Abstract: In recent years, surface plasmon-induced photocatalytic materials with tunable mesoporous framework have attracted considerable attention in energy conversion and environmental remediation. Herein we report a novel Au nanoparticles decorated mesoporous graphitic carbon nitride (Au/mp-g-C{sub 3}N{sub 4}) nanosheets viamore » a template-free and green in situ photo-reduction method. The synthesized Au/mp-g-C{sub 3}N{sub 4} nanosheets exhibit a strong absorption edge in visible and near-IR region owing to the surface plasmon resonance effect of Au nanoparticles. More attractively, Au/mp-g-C{sub 3}N{sub 4} exhibited much higher photocatalytic activity than that of pure mesoporous and bulk g-C{sub 3}N{sub 4} for the degradation of rhodamine B under sunlight irradiation. Furthermore, the photocurrent and photoluminescence studies demonstrated that the deposition of Au nanoparticles on the surface of mesoporous g-C{sub 3}N{sub 4} could effectively inhibit the recombination of photogenerated charge carriers leading to the enhanced photocatalytic activity. More importantly, the synthesized Au/mp-g-C{sub 3}N{sub 4} nanosheets possess high reusability. Hence, Au/mp-g-C{sub 3}N{sub 4} could be promising photoactive material for energy and environmental applications.« less

Au@Y 2O 3:Eu 3+ rare earth oxide hollow sub-microspheres with encapsulated gold nanoparticles and their optical properties

NASA Astrophysics Data System (ADS)

Min, Yu-Lin; Wan, Yong; Yu, Shu-Hong

2009-01-01

A facile method to synthesize novel Au@Y 2O 3:Eu 3+ hollow sub-microspheres encapsulated with moveable gold nanoparticle core and Y 2O 3:Eu 3+ as shell via two-step coating processes and a succeeding calcination process has been developed. Silica coating on citrate-stabilized gold nanoparticles with a size of 25 nm can be obtained through a slightly modified Stöber process. Gold particles coated with double shell silica and Eu doped Y(OH) 3 can be obtained by coating on the Au@SiO 2 spheres through simply adding Y(NO 3) 3, Eu(NO 3) 3 and an appropriate quantity of NH 3·H 2O. Au@Y 2O 3:Eu 3+ hollow sub-microspheres with moveable individual Au nanoparticle as core can be obtained after calcination of Au@Y 2O 3:Eu 3+ particles at 600 °C for 2 h. These new core-shell structures with encapsulated gold nanoparticles have combined optical properties of both the Au nanoparticles and the Y 2O 3:Eu 3+ phosphor materials which might have potential applications.

Constructing Ordered Three-Dimensional TiO2 Channels for Enhanced Visible-Light Photocatalytic Performance in CO2 Conversion Induced by Au Nanoparticles.

PubMed

Xue, Hairong; Wang, Tao; Gong, Hao; Guo, Hu; Fan, Xiaoli; Gao, Bin; Feng, Yaya; Meng, Xianguang; Huang, Xianli; He, Jianping

2018-03-02

As a typical photocatalyst for CO 2 reduction, practical applications of TiO 2 still suffer from low photocatalytic efficiency and limited visible-light absorption. Herein, a novel Au-nanoparticle (NP)-decorated ordered mesoporous TiO 2 (OMT) composite (OMT-Au) was successfully fabricated, in which Au NPs were uniformly dispersed on the OMT. Due to the surface plasmon resonance (SPR) effect derived from the excited Au NPs, the TiO 2 shows high photocatalytic performance for CO 2 reduction under visible light. The ordered mesoporous TiO 2 exhibits superior material and structure, with a high surface area that offers more catalytically active sites. More importantly, the three-dimensional transport channels ensure the smooth flow of gas molecules, highly efficient CO 2 adsorption, and the fast and steady transmission of hot electrons excited from the Au NPs, which lead to a further improvement in the photocatalytic performance. These results highlight the possibility of improving the photocatalysis for CO 2 reduction under visible light by constructing OMT-based Au-SPR-induced photocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation.

PubMed

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-05-22

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures.

Bare laser-synthesized Au-based nanoparticles as nondisturbing surface-enhanced Raman scattering probes for bacteria identification.

PubMed

Kögler, Martin; Ryabchikov, Yury V; Uusitalo, Sanna; Popov, Alexey; Popov, Anton; Tselikov, Gleb; Välimaa, Anna-Liisa; Al-Kattan, Ahmed; Hiltunen, Jussi; Laitinen, Riitta; Neubauer, Peter; Meglinski, Igor; Kabashin, Andrei V

2018-02-01

The ability of noble metal-based nanoparticles (NPs) (Au, Ag) to drastically enhance Raman scattering from molecules placed near metal surface, termed as surface-enhanced Raman scattering (SERS), is widely used for identification of trace amounts of biological materials in biomedical, food safety and security applications. However, conventional NPs synthesized by colloidal chemistry are typically contaminated by nonbiocompatible by-products (surfactants, anions), which can have negative impacts on many live objects under examination (cells, bacteria) and thus decrease the precision of bioidentification. In this article, we explore novel ultrapure laser-synthesized Au-based nanomaterials, including Au NPs and AuSi hybrid nanostructures, as mobile SERS probes in tasks of bacteria detection. We show that these Au-based nanomaterials can efficiently enhance Raman signals from model R6G molecules, while the enhancement factor depends on the content of Au in NP composition. Profiting from the observed enhancement and purity of laser-synthesized nanomaterials, we demonstrate successful identification of 2 types of bacteria (Listeria innocua and Escherichia coli). The obtained results promise less disturbing studies of biological systems based on good biocompatibility of contamination-free laser-synthesized nanomaterials. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Two-Dimensional Graphene-Gold Interfaces Serve as Robust Templates for Dielectric Capacitors.

PubMed

Teshome, Tamiru; Datta, Ayan

2017-10-04

The electronic structures of novel heterostructures, namely, graphene-Au van der Waals (vdW) interfaces, have been studied using density functional theory. Dispersion-corrected PBE-D2 functionals are used to describe the phonon spectrum and binding energies. Ab initio molecular dynamics simulations reveal that the vdW framework is preserved till 1200 K. Beyond T = 1200 K, a transition of the quasiplanar Au into the three-dimensional cluster-like structure is observed. A dielectric capacitor is designed by placing 1-4 hexagonal boron nitride (h-BN) monolayers between graphene and Au conductive plates. Charge separation between the Au and graphene plates is carried out under the effect of an external field normal to the graphene-h-BN-Au interface. The gravimetric capacitances are computed as C 1 = 7.6 μF/g and C 2 = 3.2 μF/g for h-BN bilayers with the Au-graphene heterostructures. The capacitive behavior shows strong deviations from the classical charging models and exemplifies the importance of quantum phenomenon at short contacts, which eventually nullifies at large interelectrode distances. The graphene-Au interface is predicted to be an exciting vdW heterostructure with a potential application as a dielectric capacitor.

Colorimetric detection of melamine in milk based on Triton X-100 modified gold nanoparticles and its paper-based application

NASA Astrophysics Data System (ADS)

Gao, Nan; Huang, Pengcheng; Wu, Fangying

2018-03-01

In this study, we have developed a method for rapid, highly efficient and selective detection of melamine. The negatively charged citrate ions form an electrostatic layer on gold nanoparticles (AuNPs) and keep the NPs dispersed and stable. When citrate-capped AuNPs were further modified with Triton X-100, it stabilized the AuNPs against the conditions of high ionic strength and a broad pH range. However, the addition of melamine caused the destabilization and aggregation of NPs. This may be attributed to the interaction between melamine and the AuNPs through the ligand exchange with citrate ions on the surface of AuNPs leading Triton X-100 to be removed. As a result, the AuNPs were unstable, resulting in the aggregation. The aggregation induced a wine red-to-blue color change, and a new absorption peak around 630 nm appeared. Triton X-100-AuNPs could selectively detect melamine at the concentration as low as 5.1 nM. This probe was successfully applied to detect melamine in milk. Furthermore, paper-based quantitative detection system using this colorimetric probe was also demonstrated by integrating with a smartphone.

IFLA General Conference, 1984. Bibliographic Control Division. Sections on Bibliography, Cataloging, and Classification. Part 2. Papers.

ERIC Educational Resources Information Center

International Federation of Library Associations, The Hague (Netherlands).

Papers on cataloging and national bibliography presented at the 1984 general conference of IFLA include: (1) "Pratiques et Problemes de Catalogage au Senegal" (Cataloging Practices and Problems in Senegal) (Marietou Diop Diongue, Senegal); (2) "The Consequences of New Technologies in Classification and Subject Cataloging in Third…

Immunosensor based on electrodeposition of gold-nanoparticles and ionic liquid composite for detection of Salmonella pullorum.

PubMed

Wang, Dan; Dou, Wenchao; Zhao, Guangying; Chen, Yan

2014-11-01

In order to increase the reproducibility and stability of electrochemical immunosensor, which is a key issue for its application and popularization, an accurate and stable immunosensor for rapid detection of Salmonella pullorum (S. pullorum) was proposed in this study. The immunosensor was fabricated by modifying Screen-printed Carbon Electrode (SPCE) with electrodeposited gold nanoparticles (AuNPs), HRP-labeled anti-S. pullorum and ionic liquids (ILs) (AuNP/HRP/IL). AuNPs are electrodeposited on the working electrode surface to increase the amount of antibodies that bind to the electrode and then modified with ILs to protect the antibodies from being inactivated in the test environment and maintain their biological activity and the stability of the detection electrode. The electrochemical characteristics of the stepwise modified electrodes and the detection of S. pullorum were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). As shown in the results of the experiments, AuNPs with unique electrochemical properties as well as biocompatibility characteristics have been proven to be able to strengthen the antibody combination effectively and to increase the electrochemical response signal. In addition, a crucial assessment regarding implementation of stability and reproducibility analysis of a range of immunosensors is provided. We found that application of AuNPs/ILs in the immune modified electrodes showed obvious improvement when compared with other groups. Given their high levels of reproducibility, stability, target specificity and sensitivity, AuNPs and ILs were considered to be excellent elements for electrode modification. Copyright © 2014 Elsevier B.V. All rights reserved.

Acousto-ultrasonics to Assess Material and Structural Properties

NASA Technical Reports Server (NTRS)

Kautz, Harold E.

2002-01-01

This report was created to serve as a manual for applying the Acousto-Ultrasonic NDE method, as practiced at NASA Glenn, to the study of materials and structures for a wide range of applications. Three state of the art acousto-ultrasonic (A-U) analysis parameters, ultrasonic decay (UD) rate, mean time (or skewing factor, "s"), and the centroid of the power spectrum, "f(sub c)," have been studied and applied at GRC for NDE interrogation of various materials and structures of aerospace interest. In addition to this, a unique application of Lamb wave analysis is shown. An appendix gives a brief overview of Lamb Wave analysis. This paper presents the analysis employed to calculate these parameters and the development and reasoning behind their use. It also discusses the planning of A-U measurements for materials and structures to be studied. Types of transducer coupling are discussed including contact and non-contact via laser and air. Experimental planning includes matching transducer frequency range to material and geometry of the specimen to be studied. The effect on results of initially zeroing the DC component of the ultrasonic waveform is compared with not doing so. A wide range of interrogation problems are addressed via the application of these analysis parameters to real specimens is shown for five cases: Case 1: Differences in density in [0] SiC/RBSN ceramic matrix composite. Case 2: Effect of tensile fatigue cycling in [+/-45] SiC/SiC ceramic matrix composite. Case 3: Detecting creep life, and failure, in Udimet 520 Nickel-Based Super Alloy. Case 4: Detecting Surface Layer Formation in T-650-35/PMR-15 Polymer Matrix Composites Panels due to Thermal Aging. Case 5: Detecting Spin Test Degradation in PMC Flywheels. Among these cases a wide range of materials and geometries are studied.

Laser ablation synthesis of new gold phosphides using red phosphorus and nanogold as precursors. Laser desorption ionisation time-of-flight mass spectrometry.

PubMed

Panyala, Nagender Reddy; Peña-Méndez, Eladia María; Havel, Josef

2012-05-15

Gold phosphides show unique optical or semiconductor properties and there are extensive high technology applications, e.g. in laser diodes, etc. In spite of the various AuP structures known, the search for new materials is wide. Laser ablation synthesis is a promising screening and synthetic method. Generation of gold phosphides via laser ablation of red phosphorus and nanogold mixtures was studied using laser desorption ionisation time-of-flight mass spectrometry (LDI TOFMS). Gold clusters Au(m)(+) (m = 1 to ~35) were observed with a difference of one gold atom and their intensities were in decreasing order with respect to m. For P(n)(+) (n = 2 to ~111) clusters, the intensities of odd-numbered phosphorus clusters are much higher than those for even-numbered phosphorus clusters. During ablation of P-nanogold mixtures, clusters Au(m)(+) (m = 1-12), P(n)(+) (n = 2-7, 9, 11, 13-33, 35-95 (odd numbers)), AuP(n)(+) (n = 1, 2-88 (even numbers)), Au(2)P(n)(+) (n = 1-7, 14-16, 21-51 (odd numbers)), Au(3)P(n)(+) (n = 1-6, 8, 9, 14), Au(4)P(n)(+) (n = 1-9, 14-16), Au(5)P(n)(+) (n = 1-6, 14, 16), Au(6)P(n)(+) (n = 1-6), Au(7)P(n)(+) (n = 1-7), Au(8)P(n)(+) (n = 1-6, 8), Au(9)P(n)(+) (n = 1-10), Au(10)P(n)(+) (n = 1-8, 15), Au(11)P(n)(+) (n = 1-6), and Au(12)P(n)(+) (n = 1, 2, 4) were detected in positive ion mode. In negative ion mode, Au(m)(-) (m = 1-5), P(n)(-) (n = 2, 3, 5-11, 13-19, 21-35, 39, 41, 47, 49, 55 (odd numbers)), AuP(n)(-) (n = 4-6, 8-26, 30-36 (even numbers), 48), Au(2)P(n)(-) (n = 2-5, 8, 11, 13, 15, 17), A(3) P(n)(-) (n = 6-11, 32), Au(4)P(n)(-) (n = 1, 2, 4, 6, 10), Au(6)P(5)(-), and Au(7)P(8)(-) clusters were observed. In both modes, phosphorus-rich Au(m)P(n) clusters prevailed. The first experimental evidence for formation of AuP(60) and gold-covered phosphorus Au(12)P(n) (n = 1, 2, 4) clusters is given. The new gold phosphides generated might inspire synthesis of new Au-P materials with specific properties. Copyright © 2012 John Wiley & Sons, Ltd.

Development of dihydrochalcone-functionalized gold nanoparticles for augmented antineoplastic activity

PubMed Central

Moolani, Harsh V; Tockstein, Sarah; Thompson, David H; Dakshinamurthy, Rajalingam

2018-01-01

Background Phloridzin, an antidiabetic and antineoplastic agent usually found in fruit trees, is a dihydrochalcone constituent that has a clinical/pharmaceutical significance as a sodium-glucose linked transport 2 (SGLT2) inhibitor. While the aglycone metabolite of phloridzin, phloretin, displays a reduced capacity of SGLT2 inhibition, this nutraceutical displays enhanced antineoplastic activity in comparison to phloridzin. Purpose The objective of this study was to develop gold nanoparticle (AuNP) mediated delivery of phloridzin and phloretin and explore their anticancer mechanism through conjugation of the dihydrochalcones and the AuNP cores. Methods Phloridzin and phloretin conjugated AuNPs (Phl-AuNP and Pht-AuNP) were synthesized in single-step, rapid, biofriendly processes. The synthesized AuNPs morphology was characterized via transmission electron microscopy and ultraviolet-visible spectroscopy. The presence of phloridzin or phloretin was confirmed using scanning electron microscopy-energy dispersive x-ray spectroscopy. The percentage of organic component (phloridzin/phloretin) onto AuNPs surface was characterized using thermogravimetric analysis. Assessment of the antineoplastic potency of the dihydrochalcones conjugated AuNPs against cancerous cell lines (HeLa) was accomplished through monitoring via flow cytometry. Results The functionalized AuNPs were synthesized via a single-step method that relied only upon the redox potential of the conjugate itself and required no toxic chemicals. The synthesized Phl-AuNPs were found to be in the size range of 15±5 nm, whereas the Pht-AuNP were found to be 8±3 nm, placing both conjugated AuNPs well within the size range necessary for successful pharmaceutical applications. These assays demonstrate a significant increase in the cancerous cell toxicities as a result of the conjugation of the drugs to AuNPs, as indicated by the 17.45-fold increase in the efficacy of Pht-AuNPs over pure phloretin, and the 4.49-fold increase in efficacy of Phl-AuNP over pure phloridzin. Conclusion We report a simple, biofriendly process using the reducing and capping potential of the dihydrochalcones, phloridzin and phloretin, to synthesize stable AuNPs that have promising futures as potential antineoplastic agents. PMID:29636609

Development of dihydrochalcone-functionalized gold nanoparticles for augmented antineoplastic activity.

PubMed

Payne, Jason N; Badwaik, Vivek D; Waghwani, Hitesh K; Moolani, Harsh V; Tockstein, Sarah; Thompson, David H; Dakshinamurthy, Rajalingam

2018-01-01

Phloridzin, an antidiabetic and antineoplastic agent usually found in fruit trees, is a dihydrochalcone constituent that has a clinical/pharmaceutical significance as a sodium-glucose linked transport 2 (SGLT2) inhibitor. While the aglycone metabolite of phloridzin, phloretin, displays a reduced capacity of SGLT2 inhibition, this nutraceutical displays enhanced antineoplastic activity in comparison to phloridzin. The objective of this study was to develop gold nanoparticle (AuNP) mediated delivery of phloridzin and phloretin and explore their anticancer mechanism through conjugation of the dihydrochalcones and the AuNP cores. Phloridzin and phloretin conjugated AuNPs (Phl-AuNP and Pht-AuNP) were synthesized in single-step, rapid, biofriendly processes. The synthesized AuNPs morphology was characterized via transmission electron microscopy and ultraviolet-visible spectroscopy. The presence of phloridzin or phloretin was confirmed using scanning electron microscopy-energy dispersive x-ray spectroscopy. The percentage of organic component (phloridzin/phloretin) onto AuNPs surface was characterized using thermogravimetric analysis. Assessment of the antineoplastic potency of the dihydrochalcones conjugated AuNPs against cancerous cell lines (HeLa) was accomplished through monitoring via flow cytometry. The functionalized AuNPs were synthesized via a single-step method that relied only upon the redox potential of the conjugate itself and required no toxic chemicals. The synthesized Phl-AuNPs were found to be in the size range of 15±5 nm, whereas the Pht-AuNP were found to be 8±3 nm, placing both conjugated AuNPs well within the size range necessary for successful pharmaceutical applications. These assays demonstrate a significant increase in the cancerous cell toxicities as a result of the conjugation of the drugs to AuNPs, as indicated by the 17.45-fold increase in the efficacy of Pht-AuNPs over pure phloretin, and the 4.49-fold increase in efficacy of Phl-AuNP over pure phloridzin. We report a simple, biofriendly process using the reducing and capping potential of the dihydrochalcones, phloridzin and phloretin, to synthesize stable AuNPs that have promising futures as potential antineoplastic agents.

Rapid microwave assisted synthesis of graphene nanosheets/polyethyleneimine/gold nanoparticle composite and its application to the selective electrochemical determination of dopamine.

PubMed

Ponnusamy, Vinoth Kumar; Mani, Veerappan; Chen, Shen-Ming; Huang, Wan-Tran; Jen, Jen-Fon

2014-03-01

In this study, a simple and fast microwave assisted chemical reduction method for the preparation of graphene nanosheet/polyethyleneimine/gold nanoparticle (GNS/PEI/AuNP) composite was developed. PEI, a cationic polymer, was used both as a non-covalent functionalizing agent for the graphene oxide nanosheets (GONSs) through electrostatic interactions in the aqueous medium and also as a stabilizing agent for the formation of AuNPs on PEI wrapped GNSs. This preparation method involves a simple mixing step followed by a simultaneous microwave assisted chemical reduction of the GONSs and gold ions. The prepared composite exhibits the dispersion of high density AuNPs which were densely decorated on the large surface area of the PEI wrapped GNS. X-ray photoelectron spectroscopy, powder X-ray diffraction, high-resolution transmission electron microscopy, field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy, and thermo-gravimetric analysis, were used to characterize the properties of the resultant composite. The prepared GNS/PEI/AuNP composite film exhibited excellent electrocatalytical activity towards the selective determination of dopamine in the presence of ascorbic acid, which showed potential application in electrochemical sensors. The applicability of the presented sensor was also demonstrated for the determination of dopamine in human urine samples. © 2013 Elsevier B.V. All rights reserved.

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.

Solvent extraction of gold using ionic liquid based process

NASA Astrophysics Data System (ADS)

Makertihartha, I. G. B. N.; Zunita, Megawati; Rizki, Z.; Dharmawijaya, P. T.

2017-01-01

In decades, many research and mineral processing industries are using solvent extraction technology for metal ions separation. Solvent extraction technique has been used for the purification of precious metals such as Au and Pd, and base metals such as Cu, Zn and Cd. This process uses organic compounds as solvent. Organic solvents have some undesired properties i.e. toxic, volatile, excessive used, flammable, difficult to recycle, low reusability, low Au recovery, together with the problems related to the disposal of spent extractants and diluents, even the costs associated with these processes are relatively expensive. Therefore, a lot of research have boosted into the development of safe and environmentally friendly process for Au separation. Ionic liquids (ILs) are the potential alternative for gold extraction because they possess several desirable properties, such as a the ability to expanse temperature process up to 300°C, good solvent properties for a wide range of metal ions, high selectivity, low vapor pressures, stability up to 200°C, easy preparation, environmentally friendly (commonly called as "green solvent"), and relatively low cost. This review paper is focused in investigate of some ILs that have the potentials as solvent in extraction of Au from mineral/metal alloy at various conditions (pH, temperature, and pressure). Performances of ILs extraction of Au are studied in depth, i.e. structural relationship of ILs with capability to separate Au from metal ions aggregate. Optimal extraction conditon in order to gain high percent of Au in mineral processing is also investigated.

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.

Electron localization in rod-shaped triicosahedral gold nanocluster

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

Zhou, Meng; Jin, Renxi; Sfeir, Matthew Y.

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. There is little known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. We reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ~100-ps localization from the two vertexes of three icosahedrons tomore » one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm -1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The electron localization phenomenon we observed provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.« less

Plasmonic ruler on field-effect devices for kinase drug discovery applications.

PubMed

Bhalla, Nikhil; Formisano, Nello; Miodek, Anna; Jain, Aditya; Di Lorenzo, Mirella; Pula, Giordano; Estrela, Pedro

2015-09-15

Protein kinases are cellular switches that mediate phosphorylation of proteins. Abnormal phosphorylation of proteins is associated with lethal diseases such as cancer. In the pharmaceutical industry, protein kinases have become an important class of drug targets. This study reports a versatile approach for the detection of protein phosphorylation. The change in charge of the myelin basic protein upon phosphorylation by the protein kinase C-alpha (PKC-α) in the presence of adenosine 5'-[γ-thio] triphosphate (ATP-S) was detected on gold metal-insulator-semiconductor (Au-MIS) capacitor structures. Gold nanoparticles (AuNPs) can then be attached to the thio-phosphorylated proteins, forming a Au-film/AuNP plasmonic couple. This was detected by a localized surface plasmon resonance (LSPR) technique alongside MIS capacitance. All reactions were validated using surface plasmon resonance technique and the interaction of AuNPs with the thio-phosphorylated proteins quantified by quartz crystal microbalance. The plasmonic coupling was also visualized by simulations using finite element analysis. The use of this approach in drug discovery applications was demonstrated by evaluating the response in the presence of a known inhibitor of PKC-α kinase. LSPR and MIS on a single platform act as a cross check mechanism for validating kinase activity and make the system robust to test novel inhibitors. Copyright © 2015 Elsevier B.V. All rights reserved.

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

PubMed Central

Zhang, Ri-Chao; Sun, Dan; Zhang, Ruirui; Lin, Wen-Feng; Macias-Montero, Manuel; Patel, Jenish; Askari, Sadegh; McDonald, Calum; Mariotti, Davide; Maguire, Paul

2017-01-01

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces. PMID:28436454

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.

M13 Virus-Incorporated Biotemplates on Electrode Surfaces To Nucleate Metal Nanostructures by Electrodeposition.

PubMed

Manivannan, Shanmugam; Kang, Inhak; Seo, Yeji; Jin, Hyo-Eon; Lee, Seung-Wuk; Kim, Kyuwon

2017-09-27

We report a virus-incorporated biological template (biotemplate) on electrode surfaces and its use in electrochemical nucleation of metal nanocomposites as an electrocatalytic material for energy applications. The biotemplate was developed with M13 virus (M13) incorporated in a silicate sol-gel matrix as a scaffold to nucleate Au-Pt alloy nanostructures by electrodeposition, together with reduced graphene oxide (rGO). The phage when engineered with Y3E peptides could nucleate Au-Pt alloy nanostructures, which ensured adequate packing density, simultaneous stabilization of rGO, and a significantly increased electrochemically active surface area. Investigation of the electrocatalytic activity of the resulting sol-gel composite catalyst toward methanol oxidation in an alkaline medium showed that this catalyst had mass activity greater than that of the biotemplate containing wild-type M13 and that of monometallic Pt and other Au-Pt nanostructures with different compositions and supports. M13 in the nanocomposite materials provided a close contact between the Au-Pt alloy nanostructures and rGO. In addition, it facilitated the availability of an OH - -rich environment to the catalyst. As a result, efficient electron transfer and a synergistic catalytic effect of the Au and Pt in the alloy nanostructures toward methanol oxidation were observed. Our nanocomposite synthesis on the novel biotemplate and its application might be useful for developing novel clean and green energy-generating and energy-storage materials.

Electron localization in rod-shaped triicosahedral gold nanocluster

DOE PAGES

Zhou, Meng; Jin, Renxi; Sfeir, Matthew Y.; ...

2017-05-30

Atomically precise gold nanocluster based on linear assembly of repeating icosahedrons (clusters of clusters) is a unique type of linear nanostructure, which exhibits strong near-infrared absorption as their free electrons are confined in a one-dimensional quantum box. There is little known about the carrier dynamics in these nanoclusters, which limit their energy-related applications. We reported the observation of exciton localization in triicosahedral Au37 nanoclusters (0.5 nm in diameter and 1.6 nm in length) by measuring femtosecond and nanosecond carrier dynamics. Upon photoexcitation to S1 electronic state, electrons in Au37 undergo ~100-ps localization from the two vertexes of three icosahedrons tomore » one vertex, forming a long-lived S1* state. Such phenomenon is not observed in Au25 (dimer) and Au13 (monomer) consisting of two and one icosahedrons, respectively. We have further observed temperature dependence on the localization process, which proves it is thermally driven. Two excited-state vibration modes with frequencies of 20 and 70 cm -1 observed in the kinetic traces are assigned to the axial and radial breathing modes, respectively. The electron localization is ascribed to the structural distortion of Au37 in the excited state induced by the strong coherent vibrations. The electron localization phenomenon we observed provides unique physical insight into one-dimensional gold nanoclusters and other nanostructures, which will advance their applications in solar-energy storage and conversion.« less

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.

Gold nanoparticle-polymer nanocomposites synthesized by room temperature atmospheric pressure plasma and their potential for fuel cell electrocatalytic application

NASA Astrophysics Data System (ADS)

Zhang, Ri-Chao; Sun, Dan; Zhang, Ruirui; Lin, Wen-Feng; Macias-Montero, Manuel; Patel, Jenish; Askari, Sadegh; McDonald, Calum; Mariotti, Davide; Maguire, Paul

2017-04-01

Conductive polymers have been increasingly used as fuel cell catalyst support due to their electrical conductivity, large surface areas and stability. The incorporation of metal nanoparticles into a polymer matrix can effectively increase the specific surface area of these materials and hence improve the catalytic efficiency. In this work, a nanoparticle loaded conductive polymer nanocomposite was obtained by a one-step synthesis approach based on room temperature direct current plasma-liquid interaction. Gold nanoparticles were directly synthesized from HAuCl4 precursor in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The resulting AuNPs/PEDOT:PSS nanocomposites were subsequently characterized under a practical alkaline direct ethanol fuel cell operation condition for its potential application as an electrocatalyst. Results show that AuNPs sizes within the PEDOT:PSS matrix are dependent on the plasma treatment time and precursor concentration, which in turn affect the nanocomposites electrical conductivity and their catalytic performance. Under certain synthesis conditions, unique nanoscale AuNPs/PEDOT:PSS core-shell structures could also be produced, indicating the interaction at the AuNPs/polymer interface. The enhanced catalytic activity shown by AuNPs/PEDOT:PSS has been attributed to the effective electron transfer and reactive species diffusion through the porous polymer network, as well as the synergistic interfacial interaction at the metal/polymer and metal/metal interfaces.

One-dimensional fossil-like γ-Fe2O3@carbon nanostructure: preparation, structural characterization and application as adsorbent for fast and selective recovery of gold ions from aqueous solution

NASA Astrophysics Data System (ADS)

Gunawan, Poernomo; Xiao, Wen; Hao Chua, Marcus Wen; Poh-Choo Tan, Cheryl; Ding, Jun; Zhong, Ziyi

2016-10-01

One-dimensional (1D) magnetic nanostructures with high thermal stability have important industrial applications, but their fabrication remains a big challenge. Herein we demonstrate a scalable approach for the preparation of stable 1D γ-Fe2O3@carbon, which is also applicable for other metal oxide-core and carbon-shell nanostructures, such as 1D TiO2@carbon. One-dimensional ferric oxyhydroxide (α-FeO(OH)) was initially prepared by a hydrothermal method, followed by carbon coating through hydrothermal treatment of the resulting metal oxide in glucose solution. After calcination in N2 gas at 500 °C and subsequent exposure to air, the initial carbon-coated 1D α-Fe2O3 was converted to 1D γ-Fe2O3@carbon, which was very stable without any observed changes even after 1.5 years of storage under ambient conditions. The materials were then used as adsorbents and found to be highly selective towards Au (III) adsorption, of which the maximum adsorption capacity is about 600 mg Au/g sorbent (1132 mg Au/g carbon). The spent sorbent containing Au after adsorption can be readily collected by applying a magnetic field due to the presence of the magnetic core, and the adsorbed Au particles are subsequently recovered after the combustion and dissolution of the sorbent. This work demonstrates not only a facile approach to the fabrication of robust 1D magnetic materials with a stable carbon shell, but also a possible cyanide-free process for the fast and selective recovery of gold from electronic waste and industrial water.

Multi-Agent Coordination Techniques for Naval Tactical Combat Resources Management

DTIC Science & Technology

2008-07-01

resource coordination and cooperation problems. The combat resource allocation planning problem is treated in the companion report [2]. 2.3 Resource...report focuses on the resource coordination problem, while allocation algorithms are discussed in the companion report [2]. First, coordination in...classification of each should be indicated as with the title.) Canada’s Leader in Defence and National Security Science and Technology Chef de file au Canada en

Influence of the Debye length on the interaction of a small molecule-modified Au nanoparticle with a surface-bound bioreceptor.

PubMed

Bukar, Natalia; Zhao, Sandy Shuo; Charbonneau, David M; Pelletier, Joelle N; Masson, Jean-Francois

2014-05-18

We report that a shorter Debye length and, as a consequence, decreased colloidal stability are required for the molecular interaction of folic acid-modified Au nanoparticles (Au NPs) to occur on a surface-bound receptor, human dihydrofolate reductase (hDHFR). The interaction measured using surface plasmon resonance (SPR) sensing was optimal in a phosphate buffer at pH 6 and ionic strength exceeding 300 mM. Under these conditions, the aggregation constant of the Au NPs was approximately 10(4) M(-1) s(-1) and the Debye length was below 1 nm, on the same length scale as the size of the folate anion (approximately 0.8 nm). Longer Debye lengths led to poorer SPR responses, revealing a reduced affinity of the folic acid-modified Au NPs for hDHFR. While high colloidal stability of Au NPs is desired in most applications, these conditions may hinder molecular interactions due to Debye lengths exceeding the size of the ligand and thus preventing close interactions with the surface-bound molecular receptor.

Efficient DFT+U calculations of ballistic electron transport: Application to Au monatomic chains with a CO impurity

NASA Astrophysics Data System (ADS)

Sclauzero, Gabriele; Dal Corso, Andrea

2013-02-01

An efficient method for computing the Landauer-Büttiker conductance of an open quantum system within DFT+U is presented. The Hubbard potential is included in electronic-structure and transport calculations as a simple renormalization of the nonlocal pseudopotential coefficients by restricting the integration for the onsite occupations within the cutoff spheres of the pseudopotential. We apply the methodology to the case of an Au monatomic chain in the presence of a CO molecule adsorbed on it. We show that the Hubbard U correction removes the spurious magnetization in the pristine Au chain at the equilibrium spacing, as well as the unphysical contribution of d electrons to the conductance, resulting in a single (spin-degenerate) transmission channel and a more realistic conductance of 1G0. We find that the conductance reduction due to CO adsorption is much larger for the atop site than for the bridge site, so that the general picture of electron transport in stretched Au chains given by the local density approximation remains valid at the equilibrium Au-Au spacing within DFT+U.

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.

Preparation and characterization of AuNPs/CNTs-ErGO electrochemical sensors for highly sensitive detection of hydrazine.

PubMed

Zhao, Zhenting; Sun, Yongjiao; Li, Pengwei; Zhang, Wendong; Lian, Kun; Hu, Jie; Chen, Yong

2016-09-01

A highly sensitive electrochemical sensor of hydrazine has been fabricated by Au nanoparticles (AuNPs) coating of carbon nanotubes-electrochemical reduced graphene oxide composite film (CNTs-ErGO) on glassy carbon electrode (GCE). Cyclic voltammetry and potential amperometry have been used to investigate the electrochemical properties of the fabricated sensors for hydrazine detection. The performances of the sensors were optimized by varying the CNTs to ErGO ratio and the quantity of Au nanoparticles. The results show that under optimal conditions, a sensitivity of 9.73μAμM(-1)cm(-2), a short response time of 3s, and a low detection limit of 0.065μM could be achieved with a linear concentration response range from 0.3μM to 319μM. The enhanced electrochemical performances could be attributed to the synergistic effect between AuNPs and CNTs-ErGO film and the outstanding catalytic effect of the Au nanoparticles. Finally, the sensor was successfully used to analyse the tap water, showing high potential for practical applications. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

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.

Formation of oligonucleotide-gated silica shell-coated Fe₃O₄-Au core-shell nanotrisoctahedra for magnetically targeted and near-infrared light-responsive theranostic platform.

PubMed

Li, Wei-Peng; Liao, Pei-Yi; Su, Chia-Hao; Yeh, Chen-Sheng

2014-07-16

A new multifunctional nanoparticle to perform a near-infrared (NIR)-responsive remote control drug release behavior was designed for applications in the biomedical field. Different from the previous studies in formation of Fe3O4-Au core-shell nanoparticles resulting in a spherical morphology, the heterostructure with polyhedral core and shell was presented with the truncated octahedral Fe3O4 nanoparticle as the core over a layer of trisoctahedral Au shell. The strategy of Fe3O4@polymer@Au was adopted using poly-l-lysine as the mediate layer, followed by the subsequent seeded growth of Au nanoparticles to form a Au trisoctahedral shell. Fe3O4@Au trisoctahedra possess high-index facets of {441}. To combine photothermal and chemotherapy in a remote-control manner, the trisoctahedral core-shell Fe3O4@Au nanoparticles were further covered with a mesoporous silica shell, yielding Fe3O4@Au@mSiO2. The bondable oligonucleotides (referred as dsDNA) were used as pore blockers of the mesoporous silica shell that allowed the controlled release, resulting in a NIR-responsive DNA-gated Fe3O4@Au@mSiO2 nanocarrier. Taking advantage of the magnetism, remotely triggered drug release was facilitated by magnetic attraction accompanied by the introduction of NIR radiation. DNA-gated Fe3O4@Au@mSiO2 serves as a drug control and release carrier that features functions of magnetic target, MRI diagnosis, and combination therapy through the manipulation of a magnet and a NIR laser. The results verified the significant therapeutic effects on tumors with the assistance of combination therapy consisting of magnetic guidance and remote NIR control.

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).

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.

Mesoporous gold sponges: electric charge-assisted seed mediated synthesis and application as surface-enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Yi, Zao; Luo, Jiangshan; Tan, Xiulan; Yi, Yong; Yao, Weitang; Kang, Xiaoli; Ye, Xin; Zhu, Wenkun; Duan, Tao; Yi, Yougen; Tang, Yongjian

2015-11-01

Mesoporous gold sponges were prepared using 4-dimethylaminopyridine (DMAP)-stabilized Au seeds. This is a general process, which involves a simple template-free method, room temperature reduction of HAuCl4·4H2O with hydroxylamine. The formation process of mesoporous gold sponges could be accounted for the electrostatic interaction (the small Au nanoparticles (~3 nm) and the positively charged DMAP-stabilized Au seeds) and Ostwald ripening process. The mesoporous gold sponges had appeared to undergo electrostatic adsorption initially, sequentially linear aggregation, welding and Ostwald ripening, then, they randomly cross link into self-supporting, three-dimensional networks with time. The mesoporous gold sponges exhibit higher surface area than the literature. In addition, application of the spongelike networks as an active material for surface-enhanced Raman scattering has been investigated by employing 4-aminothiophenol (4-ATP) molecules as a probe.

Nanoantenna-Microcavity Hybrids with Highly Cooperative Plasmonic-Photonic Coupling

NASA Astrophysics Data System (ADS)

Liu, Jui-Nung; Huang, Qinglan; Liu, Keng-Ku; Singamaneni, Srikanth; Cunningham, Brian T.

2017-12-01

Nanoantennas concentrate electromagnetic energy into deep-subwavelength volumes (hotspot), which benefits a wide range of applications such as spontaneous emission enhancement, nonlinear optics, nanolaser, and surface-enhanced Raman scattering (SERS). To increase hotspot intensity, methods for sculpting individual nanoantenna resonance have been previously explored. Here, we study a nanoantenna-microcavity hybrid approach for highly cooperative hotspot enhancement, combining gold nanorods (AuNRs) for nanometer-scale light concentration and a resonant photonic crystal (PC) slab for efficient near-field excitation and optical feedback. We experimentally validate the predicted synergistic hybrid enhancement with SERS, and demonstrate that coupling to the modest-Q PC guided resonance (PCGR) boosts the hotspot intensity of the AuNR by at least one order of magnitude in comparison to the Fabry-Perot cavity enhanced (~5X) AuNR. These results exhibit a dissimilar hybrid cooperativity versus previously reported nanoantenna-cavity systems, and pave the new way to further facilitate light-nanoantenna interaction for many applications.

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.

Mesoporous gold sponges: electric charge-assisted seed mediated synthesis and application as surface-enhanced Raman scattering substrates

PubMed Central

Yi, Zao; Luo, Jiangshan; Tan, Xiulan; Yi, Yong; Yao, Weitang; Kang, Xiaoli; Ye, Xin; Zhu, Wenkun; Duan, Tao; Yi, Yougen; Tang, Yongjian

2015-01-01

Mesoporous gold sponges were prepared using 4-dimethylaminopyridine (DMAP)-stabilized Au seeds. This is a general process, which involves a simple template-free method, room temperature reduction of HAuCl4·4H2O with hydroxylamine. The formation process of mesoporous gold sponges could be accounted for the electrostatic interaction (the small Au nanoparticles (~3 nm) and the positively charged DMAP-stabilized Au seeds) and Ostwald ripening process. The mesoporous gold sponges had appeared to undergo electrostatic adsorption initially, sequentially linear aggregation, welding and Ostwald ripening, then, they randomly cross link into self-supporting, three-dimensional networks with time. The mesoporous gold sponges exhibit higher surface area than the literature. In addition, application of the spongelike networks as an active material for surface-enhanced Raman scattering has been investigated by employing 4-aminothiophenol (4-ATP) molecules as a probe. PMID:26538365

Synthesis and antimicrobial activity of gold/silver-tellurium nanostructures.

PubMed

Chang, Hsiang-Yu; Cang, Jinshun; Roy, Prathik; Chang, Huan-Tsung; Huang, Yi-Cheng; Huang, Chih-Ching

2014-06-11

Gold-tellurium nanostructures (Au-Te NSs), silver-tellurium nanostructures (Ag-Te NSs), and gold/silver-tellurium nanostructures (Au/Ag-Te NSs) have been prepared through galvanic reactions of tellurium nanotubes (Te NTs) with Au(3+), Ag(+), and both ions, respectively. Unlike the use of less environmentally friendly hydrazine, fructose as a reducing agent has been used to prepare Te NTs from TeO2 powders under alkaline conditions. The Au/Ag-Te NSs have highly catlaytic activity to convert nonfluorescent Amplex Red to form fluorescent product, revealing their great strength of generating reactive oxygen species (ROS). Au/Ag-Te NSs relative to the other two NSs exhibit greater antimicrobial activity toward the growth of E. coli, S. enteritidis, and S. aureus; the minimal inhibitory concentration (MIC) values of Au/Ag-Te NSs were much lower (>10-fold) than that of Ag-Te NSs and Au-Te NSs. The antibacterial activity of Au/Ag-Te NSs is mainly due to the release of Ag(+) ions and Te-related ions and also may be due to the generated ROS which destroys the bacteria membrane. In vitro cytotoxicity and hemolysis analyses have revealed their low toxicity in selected human cell lines and insignificant hemolysis in red blood cells. In addition, inhibition zone measurements using a Au/Ag-Te NSs-loaded konjac jelly film have suggested that it has great potential in practial application such as wound dressing for reducing bacterial wound infection. Having great antibacterial activitiy and excellent biocompatibility, the low-cost Au/Ag-Te NSs hold great potential as effective antimicrobial drugs.

Gold(III) bis-thiosemicarbazonato complexes: synthesis, characterization, radiochemistry and X-ray crystal structure analysis.

PubMed

Bottenus, Brienne N; Kan, Para; Jenkins, Tyler; Ballard, Beau; Rold, Tammy L; Barnes, Charles; Cutler, Cathy; Hoffman, Timothy J; Green, Mark A; Jurisson, Silvia S

2010-01-01

A variety of (bis)thiosemicarbazone-based ligand systems have been investigated as chelating agents for Au(III) complexes with potential radiotherapeutic applications. Ligand systems containing an ethyl, propyl or butyl backbone between the two imine N donors have been synthesized to evaluate chelate ring size effects on the resultant Au(III) complex stability at the macroscopic and radiotracer levels. The Au(III) complexes were synthesized and characterized by NMR, electrospray ionization mass spectra, elemental analysis and X-ray crystallography. The (198)Au complexes were evaluated in vitro at the tracer level for stability in phosphate-buffered saline at pH 7.4 and 37 degrees C. One of these complexes [(198)Au(3,4-HxTSE)] showed high in vitro stability and was further evaluated in vivo in normal mice. [Au(ATSM)]AuCl(4).2CH(3)OH, (ATSM=diacetyl-bis(N(4)-methylthiosemicarbazone)) H(14)C(8)N(6)O(2)S(2)Cl(4)Au(2).2CH(3)OH, crystallized from methanol in the monoclinic space group P21/n with a=14.7293(13) A, b=7.7432(7) A, c=20.4363(18) A, beta=100.140(2) degrees, V=2294.4 (4) A(3), Z=4; [Au(3,4-HxTSE)]Cl.CH(3)CH(2)OH/AuCl(2), (3,4-HxTSE=3,4-hexanedione-bis(N(4)-ethylthiosemicarbazone)) H(26)C(13.6)N(6)O(0.8)S(2)Cl(1.2)Au(1.2), crystallized from ethanol in the monoclinic space group P21/c with a=10.1990(10) A, b=13.8833(14) A, c=15.1752(15) A, beta=99.353(2) degrees , V=2120.2 (4) A(3), Z=4. These studies revealed poor stability of the [(198)Au][Au(3,4-HxTSE)](+) complex; however, crystal structure data suggest potential alterations to the ligand backbone may increase stability. Copyright 2010 Elsevier Inc. All rights reserved.

Charge transfer process at the Ag/MPH/TiO2 interface by SERS: alignment of the Fermi level.

PubMed

Zhang, Xiaolei; Sui, Huimin; Wang, Xiaolei; Su, Hongyang; Cheng, Weina; Wang, Xu; Zhao, Bing

2016-11-02

A nanoscale metal-molecule-semiconductor assembly (Ag/4-mercaptophenol/TiO 2 ) has been fabricated over Au nanoparticle (NP) films as a model to study the interfacial charge transfer (CT) effects involved in Ag/MPH/TiO 2 . Due to the interaction between Au NPs and Ag NPs, some distinct differences occur in the SERS spectra. We also measured the SERS of Ag/MPH (4-mercaptophenol), Ag/MPH/TiO 2 , and Au/Ag/MPH/TiO 2 assemblies at excitation wavelengths of 477, 514, 532, 633, and 785 nm. We found that the changes in the CT process, caused by the introduction of TiO 2 and Au, can be reflected in SERS. Then in combination with other detection methods, we proposed a possible CT process involved in the Ag/MPH, Ag/MPH/TiO 2 , and Au/Ag/MPH/TiO 2 assemblies. A Pt/Ag/MPH/TiO 2 assembly was also constructed to verify our proposed CT mechanism. This work not only provides more details about CT between metal-molecule-semiconductor interfaces but also aids in constructing nanoscale models to study interfacial problems with the SERS technique.

Synthesis of a novel Au nanoparticles decorated Ni-MOF/Ni/NiO nanocomposite and electrocatalytic performance for the detection of glucose in human serum.

PubMed

Chen, Jingyuan; Xu, Qin; Shu, Yun; Hu, Xiaoya

2018-07-01

A nonenzymatic glucose electrochemical sensor was constructed based on Au nanoparticles (AuNPs) decorated Ni metal-organic-framework (MOF)/Ni/NiO nanocomposite. Ni-MOF/Ni/NiO nanocomposite was synthesized by one-step calcination of Ni-MOF. Then AuNPs were loaded onto the Ni-based nanocomposites' surface through electrostatic adsorption. Through characterization by transmission electron microscopy (TEM), high resolution TEM (HRTEM) and energy disperse spectroscopy (EDS) mapping, it is found that the AuNPs were well distributed on the surface of Ni-based nanocomposite. Cyclic voltammetric (CV) study showed the electrocatalytic activity of Au-Ni nanocomposite was highly improved after loading AuNPs onto it. Amperometric study demonstrated that the Au-Ni nanocomposites modified glassy carbon electrode (GCE) exhibited a high sensitivity of 2133.5 mA M -1 cm -2 and a wide linear range (0.4-900 μM) toward the oxidation of glucose with a detection limit as low as 0.1 μM. Moreover, the reproducibility, selectivity and stability of the sensor all exhibited outstanding performance. We applied the as-fabricated high performance sensor to measure the glucose levels in human serum and obtained satisfactory results. It is believed that AuNPs decorated Ni MOF/Ni/NiO nanocomposite provides a new platform for developing highly performance electrochemical sensors in practical applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Optimization of anti-cancer drugs and a targeting molecule on multifunctional gold nanoparticles.

PubMed

Rizk, Nahla; Christoforou, Nicolas; Lee, Sungmun

2016-05-06

Breast cancer is the most common and deadly cancer among women worldwide. Currently, nanotechnology-based drug delivery systems are useful for cancer treatment; however, strategic planning is critical in order to enhance the anti-cancer properties and reduce the side effects of cancer therapy. Here, we designed multifunctional gold nanoparticles (AuNPs) conjugated with two anti-cancer drugs, TGF-β1 antibody and methotrexate, and a cancer-targeting molecule, folic acid. First, optimum size and shape of AuNPs was selected by the highest uptake of AuNPs by MDA-MB-231, a metastatic human breast cancer cell line. It was 100 nm spherical AuNPs (S-AuNPs) that were used for further studies. A fixed amount (900 μl) of S-AuNP (3.8 × 10(8) particles/ml) was conjugated with folic acid-BSA or methotrexate-BSA. Methotrexate on S-AuNP induced cellular toxicity and the optimum amount of methotrexate-BSA (2.83 mM) was 500 μl. Uptake of S-AuNPs was enhanced by folate conjugation that binds to folate receptors overexpressed by MDA-MB-231 and the optimum uptake was at 500 μl of folic acid-BSA (2.83 mM). TGF-β1 antibody on S-AuNP reduced extracellular TGF-β1 of cancer cells by 30%. Due to their efficacy and tunable properties, we anticipate numerous clinical applications of multifunctional gold nanospheres in treating breast cancer.

Optimization of anti-cancer drugs and a targeting molecule on multifunctional gold nanoparticles

NASA Astrophysics Data System (ADS)

Rizk, Nahla; Christoforou, Nicolas; Lee, Sungmun

2016-05-01

Breast cancer is the most common and deadly cancer among women worldwide. Currently, nanotechnology-based drug delivery systems are useful for cancer treatment; however, strategic planning is critical in order to enhance the anti-cancer properties and reduce the side effects of cancer therapy. Here, we designed multifunctional gold nanoparticles (AuNPs) conjugated with two anti-cancer drugs, TGF-β1 antibody and methotrexate, and a cancer-targeting molecule, folic acid. First, optimum size and shape of AuNPs was selected by the highest uptake of AuNPs by MDA-MB-231, a metastatic human breast cancer cell line. It was 100 nm spherical AuNPs (S-AuNPs) that were used for further studies. A fixed amount (900 μl) of S-AuNP (3.8 × 108 particles/ml) was conjugated with folic acid-BSA or methotrexate-BSA. Methotrexate on S-AuNP induced cellular toxicity and the optimum amount of methotrexate-BSA (2.83 mM) was 500 μl. Uptake of S-AuNPs was enhanced by folate conjugation that binds to folate receptors overexpressed by MDA-MB-231 and the optimum uptake was at 500 μl of folic acid-BSA (2.83 mM). TGF-β1 antibody on S-AuNP reduced extracellular TGF-β1 of cancer cells by 30%. Due to their efficacy and tunable properties, we anticipate numerous clinical applications of multifunctional gold nanospheres in treating breast cancer.

Orientation sensors by defocused imaging of single gold nano-bipyramids

NASA Astrophysics Data System (ADS)

Zhang, Fanwei; Li, Qiang; Rao, Wenye; Hu, Hongjin; Gao, Ye; Wu, Lijun

2018-01-01

Optical probes for nanoscale orientation sensing have attracted much attention in the field of single-molecule detections. Noble metal especially Au nanoparticles (NPs) exhibit extraordinary plasmonic properties, great photostability, excellent biocompatibility and nontoxicity, and thereby could be alternative labels to conventional applied organic dyes or quantum dots. One type of the most interesting metallic NPs is Au nanorods (AuNRs). Its anisotropic emission accompanied with anisotropic shape is potentially applicable in orientation sensing. Recently, we resolved the 3D orientation of single AuNRs within one frame by deliberately introducing an aberration (slight shift of the dipole away from the focal plane) to the imaging system1 . This defocused imaging technique is based on the electron transition dipole approximation and the fact that the dipole radiation exhibits an angular anisotropy. Since the photoluminescence quantum yield (PLQY) can be enhanced by the "lightning rod effect" (at a sharp angled surface) and localized SPR modes, that of the single Au nano-bipyramid (AuNB) with more sharp tips or edges was found to be doubled comparing to AuNRs with a same effective size2. Here, with a 532 nm excitation, we find that the PL properties of individual AuNBs can be described by three perpendicularly-arranged dipoles (with different ratios). Their PL defocused images are bright, clear and exhibit obvious anisotropy. These properties suggest that AuNBs are excellent candidates for orientation sensing labels in single molecule detections.

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.

Selection of Optical Cavity Surface Coatings for 1micron Laser Based Missions

NASA Technical Reports Server (NTRS)

Hedgeland, Randy J.; Straka, Sharon; Matsumura, Mark; Hammerbacher, Joseph

2004-01-01

The particulate surface cleanliness level on several coatings for aluminum and beryllium substrates were examined for use in the optical cavities of high pulse energy Nd:YAG Q-switched, diode-pumped lasers for space flight applications. Because of the high intensity of the lasers, any contaminants in the laser beam path could damage optical coatings and limit the instrument mission objectives at the operating wavelength of 1 micron (micrometer). Our goal was to achieve an EST-STD-CC1246D Level 100 particulate distribution or better to ensure particulate redistribution during launch would not adversely affect the performance objectives. Tapelifts were performed to quantify the amount of particles using in-house developed procedures. The primary candidate coatings included chromate conversion coating aluminum (Al), uncoated Al electroless Nickel (Ni) on Al, Ni-gold (Au) on Al, anodized Al, and gold (Au)/Ni on Beryllium (Be). The results indicate that there were advantages in Ni and Au coating applications for the two major substrates, Al and Be, when considering applications that need to meet launch environments.

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

Xanthan gum stabilized PEGylated gold nanoparticles for improved delivery of curcumin in cancer

NASA Astrophysics Data System (ADS)

Swami Muddineti, Omkara; Kumari, Preeti; Ajjarapu, Srinivas; Manish Lakhani, Prit; Bahl, Rishabh; Ghosh, Balaram; Biswas, Swati

2016-08-01

In recent years, gold nanoparticles (AuNPs) have received immense interest in various biomedical applications including drug delivery, photothermal ablation of cancer and imaging agent for cancer diagnosis. However, the synthesis of AuNPs poses challenges due to the poor reproducibility and stability of the colloidal system. In the present work, we developed a one step, facile procedure for the synthesis of AuNPs from hydrogen tetrachloroaurate (III) hydrate (HAuCl4. 3H2O) by using ascorbic acid and xanthan gum (XG) as reducing agent and stabilizer, respectively. The effect of concentrations of HAuCl4, 3H2O, ascorbic acid and methoxy polyethylene glycol-thiol (mPEG800-SH) were optimized and it was observed that stable AuNPs were formed at concentrations of 0.25 mM, 50 μM and 1 mM for HAuCl4.3H2O, ascorbic acid, and mPEG800-SH, respectively. The XG stabilized, deep red wine colored AuNPs (XG-AuNPs) were obtained by drop-wise addition of aqueous solution of ascorbic acid (50 mM) and XG (1.5 mg ml-1). Synthesized XG-AuNPs showed λmax at 540 nm and a mean hydrodynamic diameter of 80 ± 3 nm. PEGylation was performed with mPEG800-SH to obtain PEGylated XG-AuNPs (PX-AuNPs) and confirmed by Ellman’s assay. No significant shift observed in λmax and hydrodynamic diameter between XG-AuNPs and PX-AuNPs. Colloidal stability of PX-AuNPs was studied in normal saline, buffers within a pH range of 1.2-7.4, DMEM complete medium and in normal storage condition at 4 ˚C. Further, water soluble curcumin was prepared using PVP-K30 as solid dispersion and loaded on to PX-AuNPs (CPX-AuNPs), and evaluated for cellular uptake and cytotoxicity in Murine melanoma (B16F10) cells. Time and concentration dependent studies using CPX-AuNPs showed efficient uptake and decreased cell viability compared to free curcumin.

A sensitive and selective resonance Rayleigh scattering method for quick detection of avidin using affinity labeling Au nanoparticles

NASA Astrophysics Data System (ADS)

Wang, Qi; Huang, Xi; Fu, Xuan; Deng, Huan; Ma, Meihu; Cai, Zhaoxia

2016-06-01

Avidin is a glycoprotein with antinutritional property, which should be limited in daily food. We developed an affinity biosensor system based on resonance Rayleigh scattering (RRS) and using affinity biotin labeling Au nanoparticles (AuNPs). This method was selective and sensitive for quick avidin detection due to the avidin-biotin affinitive interaction. Under optimal conditions, RRS intensity of biotin-AuNPs increase linearly with an increasing concentration of avidin from 5 to 160 ng/mL. The lower limit of detection was 0.59 ng/mL. This rapid and selective avidin detection method was used in synthetic samples and egg products with recoveries of between 102.97 and 107.92%, thereby demonstrating the feasible and practical application of this assay.

Gold nanoworms immobilized graphene oxide polymer brush nanohybrid for catalytic degradation studies of organic dyes

NASA Astrophysics Data System (ADS)

Mogha, Navin Kumar; Gosain, Saransh; Masram, Dhanraj T.

2017-02-01

In the present work, we report gold nanoparticles (AuNPs) on poly (dimethylaminoethyl methacrylate) (PDMAEMA) brushes immobilized reduced graphene oxide (Au/PDMAEMA/RGO) as catalyst for degradation kinetic studies of Rhodamine B (RB), Methyl Orange (MO) and Eosine Y (EY) dyes, having an excellent catalytic activity, as evident by the apparent rate constant (kapp), which is found to be 21.8, 26.2, and 8.7 (×10-3 s-1), for RB, MO and EY respectively. Au/PDMAEMA/RGO catalyst is easy to use, highly efficient, recyclable, which make it suitable for applications in waste water management. Foremost, synthesis of PDMAEMA brushes on graphene oxide is accomplished by Atom transfer radical polymerization method (ATRP), whereas AuNPs are synthesized by simple chemical reduction method.

Self-assembled vertically aligned Au nanorod arrays for surface-enhanced Raman scattering (SERS) detection of Cannabinol

NASA Astrophysics Data System (ADS)

Milliken, Sarah; Fraser, Jeff; Poirier, Shawn; Hulse, John; Tay, Li-Lin

2018-05-01

Self-assembled multi-layered vertically aligned gold nanorod (AuNR) arrays have been fabricated by a simple preparation process that requires a balance between the particle concentration and the ionic strength of the solvent. An experimentally determined critical AuNR concentration of 2.0 nM and 50 mM NaCl produces well-ordered vertically aligned hexagonally close-packed AuNR arrays. We demonstrate surface treatment via UV Ozone cleaning of such samples to allow introduction of analyte molecules (benzenethiol and cannabinol) for effective surface enhanced Raman scattering detection. This is the first demonstration of the SERS analysis of cannabinol. This approach demonstrates a cost-effective, high-yield and simple fabrication route to SERS sensors with application in the screening for the cannabinoids.

Ultra-fast electron capture by electrosterically-stabilized gold nanoparticles.

PubMed

Ghandi, Khashayar; Findlater, Alexander D; Mahimwalla, Zahid; MacNeil, Connor S; Awoonor-Williams, Ernest; Zahariev, Federico; Gordon, Mark S

2015-07-21

Ultra-fast pre-solvated electron capture has been observed for aqueous solutions of room-temperature ionic liquid (RTIL) surface-stabilized gold nanoparticles (AuNPs; ∼9 nm). The extraordinarily large inverse temperature dependent rate constants (k(e)∼ 5 × 10(14) M(-1) s(-1)) measured for the capture of electrons in solution suggest electron capture by the AuNP surface that is on the timescale of, and therefore in competition with, electron solvation and electron-cation recombination reactions. The observed electron transfer rates challenge the conventional notion that radiation induced biological damage would be enhanced in the presence of AuNPs. On the contrary, AuNPs stabilized by non-covalently bonded ligands demonstrate the potential to quench radiation-induced electrons, indicating potential applications in fields ranging from radiation therapy to heterogeneous catalysis.

Inspection of baked carbon anodes using a combination of multi-spectral acousto-ultrasonic techniques and principal component analysis.

PubMed

Boubaker, Moez Ben; Picard, Donald; Duchesne, Carl; Tessier, Jayson; Alamdari, Houshang; Fafard, Mario

2018-05-17

This paper reports on the application of an acousto-ultrasonic (AU) scheme for the inspection of industrial-size carbon anode blocks used in the production of primary aluminium by the Hall-Héroult process. A frequency-modulated wave is used to excite the anode blocks at multiple points. The collected attenuated AU signals are decomposed using the Discrete Wavelet Transform (DTW) after which vectors of features are calculated. Principal Component Analysis (PCA) is utilized to cluster the AU responses of the anodes. The approach allows locating cracks in the blocks and the AU features were found sensitive to crack severity. The results are validated using images collected after cutting some anodes. Copyright © 2018 Elsevier B.V. All rights reserved.

NaNO3/NaCl Oxidant and Polyethylene Glycol (PEG) Capped Gold Nanoparticles (AuNPs) as a Novel Green Route for AuNPs Detection in Electrochemical Biosensors.

PubMed

López-Marzo, Adaris M; Hoyos-de-la-Torre, Raquel; Baldrich, Eva

2018-03-20

Gold nanoparticles (AuNPs) have been exploited as signal-producing tags in electrochemical biosensors. However, the electrochemical detection of AuNPs is currently performed using corrosive acid solutions, which may raise health and environmental concerns. Here, oxidant salts, and specifically the environmentally friendly and occupational safe NaNO 3 /NaCl mixture, have been evaluated for the first time as potential alternatives to the acid solutions traditionally used for AuNPs electrooxidation. In addition, a new strategy to improve the sensitivity of the biosensor through PEG-based ligand exchange to produce less compact and easier to oxidize AuNPs immunoconjugates is presented too. As we show, the electrochemical immunosensor using NaNO 3 /NaCl measurement solution for AuNPs electrooxidation and detection, coupled to the employment of PEG-capped nanoimmunoconjugates, produced results comparable to classical HCl detection. The procedure developed was next tested for human matrix metallopeptidase-9 (hMMP9) analysis, exhibiting a 0.18-23 ng/mL linear range, a detection limit of 0.06 ng/mL, and recoveries between 95 and 105% in spiked human plasma. These results show that the procedure developed is applicable to the analysis of protein biomarkers in blood plasma and could contribute to the development of more environmentally friendly AuNP-based electrochemical biosensors.

Naked eye and spectrophotometric detection of chromogenic insecticide in aquaculture using amine functionalized gold nanoparticles in the presence of major interferents

NASA Astrophysics Data System (ADS)

Loganathan, C.; John, S. Abraham

2017-02-01

Detection of a chromogenic insecticide, malachite green (MG) using 3,5-diamino-1,2,4-triazole capped gold nanoparticles (DAT-AuNPs) by both naked eye and spectrophotometry was described in this paper. The DAT-AuNPs were prepared by wet chemical method and show absorption maximum at 518 nm. The zeta potential of DAT-AuNPs was found to be - 39.9 mV, suggesting that one of the amine groups of DAT adsorbed on the surface of AuNPs and the other amine group stabilizes the AuNPs from aggregation. The wine red color DAT-AuNPs changes to violet while adding 25 μM MG whereas the absorption band at 518 nm was increased and shifted towards longer wavelength. However, addition of 70 μM MG leads to the aggregation of DAT-AuNPs. This is due to strong electrostatic interaction between ammonium ion of MG and the free amine group of DAT. Based on the color change and shift in SPR band, 25 and 5 μM MG can be easily detected by naked eye and spectrophotometry. The DAT-AuNPs show high selectivity towards MG even in the presence of 5000-fold higher concentrations of common interferents. The practical application was successfully demonstrated by determining MG in fish farm water.

Sunlight-Induced photochemical synthesis of Au nanodots on α-Fe2O3@Reduced graphene oxide nanocomposite and their enhanced heterogeneous catalytic properties.

PubMed

Bharath, G; Anwer, Shoaib; Mangalaraja, R V; Alhseinat, Emad; Banat, Fawzi; Ponpandian, N

2018-04-09

In this present study, we report the synthesis of Au nanodots on α-Fe 2 O 3 @reduced graphene oxide (RGO) based hetero-photocatalytic nanohybrids through a chlorophyll mediated photochemical synthesis. In this process, chlorophyll induces a rapid reduction (30 min) of Au 3+ ions to Au° metallic nanodots on α-Fe 2 O 3 @RGO surface under sunlight irradiation. The nucleation growth process, photo-induced electron-transfer mechanism and physico-chemical properties of the Au@α-Fe 2 O 3 @RGO ternary nanocomposites were systematically studied with various analytical techniques. This novel photochemical synthesis process is a cost-effective, convenient, surfactant-less, and scalable method. Moreover, the prepared ternary nanocomposites enhanced catalytic activity as compared to pure α-Fe 2 O 3 and α-Fe 2 O 3 @RGO. The advantages and synergistic effect of Au@α-Fe 2 O 3 @RGO exhibit, (i) a broader range of visible-light absorption due to visible light band gap of α-Fe 2 O 3 , (ii) lower recombination possibility of photo-generated electrons and holes due to effect of Au and (iii) faster electron transfer due to higher conductivity of RGO. Therefore, the prepared Au@α-Fe 2 O 3 @RGO hetero-photocatalytic nanohybrids exhibited a remarkable photocatalytic activity, thus enabling potential active hetero-photocatalyst for industrial and environmental applications.

Aneuploidogenic effects and DNA oxidation induced in vitro by differently sized gold nanoparticles

PubMed Central

Di Bucchianico, Sebastiano; Fabbrizi, Maria Rita; Cirillo, Silvia; Uboldi, Chiara; Gilliland, Douglas; Valsami-Jones, Eugenia; Migliore, Lucia

2014-01-01

Gold nanoparticles (Au NPs) are used in many fields, including biomedical applications; however, no conclusive information on their potential cytotoxicity and genotoxicity mechanisms is available. For this reason, experiments in human primary lymphocytes and murine macrophages (Raw264.7) were performed exposing cells to spherical citrate-capped Au NPs with two different nominal diameters (5 nm and 15 nm). The proliferative activity, mitotic, apoptotic, and necrotic markers, as well as chromosomal damage were assessed by the cytokinesis-block micronucleus cytome assay. Fluorescence in situ hybridization with human and murine pancentromeric probes was applied to distinguish between clastogenic and aneuploidogenic effects. Our results indicate that 5 nm and 15 nm Au NPs are able to inhibit cell proliferation by apoptosis and to induce chromosomal damage, in particular chromosome mis-segregation. DNA strand breaks were detected by comet assay, and the modified protocol using endonuclease-III and formamidopyrimidine-DNA glycosylase restriction enzymes showed that pyrimidines and purines were oxidatively damaged by Au NPs. Moreover, we show a size-independent correlation between the cytotoxicity of Au NPs and their tested mass concentration or absolute number, and genotoxic effects which were more severe for Au NP 15 nm compared to Au NP 5 nm. Results indicate that apoptosis, aneuploidy, and DNA oxidation play a pivotal role in the cytotoxicity and genotoxicity exerted by Au NPs in our cell models. PMID:24855356

Aneuploidogenic effects and DNA oxidation induced in vitro by differently sized gold nanoparticles.

PubMed

Di Bucchianico, Sebastiano; Fabbrizi, Maria Rita; Cirillo, Silvia; Uboldi, Chiara; Gilliland, Douglas; Valsami-Jones, Eugenia; Migliore, Lucia

2014-01-01

Gold nanoparticles (Au NPs) are used in many fields, including biomedical applications; however, no conclusive information on their potential cytotoxicity and genotoxicity mechanisms is available. For this reason, experiments in human primary lymphocytes and murine macrophages (Raw264.7) were performed exposing cells to spherical citrate-capped Au NPs with two different nominal diameters (5 nm and 15 nm). The proliferative activity, mitotic, apoptotic, and necrotic markers, as well as chromosomal damage were assessed by the cytokinesis-block micronucleus cytome assay. Fluorescence in situ hybridization with human and murine pancentromeric probes was applied to distinguish between clastogenic and aneuploidogenic effects. Our results indicate that 5 nm and 15 nm Au NPs are able to inhibit cell proliferation by apoptosis and to induce chromosomal damage, in particular chromosome mis-segregation. DNA strand breaks were detected by comet assay, and the modified protocol using endonuclease-III and formamidopyrimidine-DNA glycosylase restriction enzymes showed that pyrimidines and purines were oxidatively damaged by Au NPs. Moreover, we show a size-independent correlation between the cytotoxicity of Au NPs and their tested mass concentration or absolute number, and genotoxic effects which were more severe for Au NP 15 nm compared to Au NP 5 nm. Results indicate that apoptosis, aneuploidy, and DNA oxidation play a pivotal role in the cytotoxicity and genotoxicity exerted by Au NPs in our cell models.

Electronic Structure of a Self-Assembled Monolayer with Two Surface Anchors: 6-Mercaptopurine on Au(111).

PubMed

Fernández, Cynthia C; Pensa, Evangelina; Carro, Pilar; Salvarezza, Roberto; Williams, Federico J

2018-05-22

The electronic structure of aromatic and aliphatic thiols on Au(111) has been extensively studied in relation to possible applications in molecular electronics. In this work, the effect on the electronic structure of an additional anchor to the S-Au bond using 6-mercaptopurine as a model system has been investigated. Results from X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory (DFT) confirm that this molecule adsorbs on Au(111) with S-Au and iminic N-Au bonds. Combined ultraviolet photoelectron spectroscopy and DFT data reveal that formation of the 6MP self-assembled monolayer generates a molecular dipole perpendicular to the surface, with negative charges residing at the metal/monolayer interface and positive charges at the monolayer/vacuum interface, which lowers the substrate work function. Scanning tunneling microscopy shows two surface molecular domains: a well-ordered rectangular lattice where molecules are tilted on average 30° with respect to the substrate and aligned 6MP islands where molecules are standing upright. Finally, we found a new electronic state located at -1.7 eV with respect to the Fermi level that corresponds to a localized π molecular state, while the state corresponding to the N-Au bond is hybridized with Au d electrons and stabilized at much lower energies (-3 eV).

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.

The effect of particle size on the genotoxicity of gold nanoparticles.

PubMed

Xia, Qiyue; Li, Hongxia; Liu, Ying; Zhang, Shuyang; Feng, Qiyi; Xiao, Kai

2017-03-01

Despite the increasing biomedical applications of gold nanoparticles (AuNPs), their toxicological effects need to be thoroughly understood. In the present study, the genotoxic potential of commercially available AuNPs with varying size (5, 20, and 50 nm) were assessed using a battery of in vitro and in vivo genotoxicity assays. In the comet assay, 20 and 50 nm AuNPs did not induce obvious DNA damage in HepG2 cells at the tested concentrations, whereas 5 nm NPs induced a dose-dependent increment in DNA damage after 24-h exposure. Furthermore, 5 nm AuNPs induced cell cycle arrest in G1 phase in response to DNA damage, and promoted the production of reactive oxygen species (ROS). In the chromosomal aberration test, AuNPs exposure did not increase in the frequency of chromosomal aberrations in Chinese hamster lung (CHL) cells. In the standard in vivo micronucleus test, no obvious increase in the frequency of micronucleus formation was found in mice after 4 day exposure of AuNPs. However, when the exposure period was extended to 14 days, 5 nm AuNPs presented significant clastogenic damage, with a dose-dependent increase of micronuclei frequencies. This finding suggests that particle size plays an important role in determining the genotoxicity of AuNPs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 710-719, 2017. © 2016 Wiley Periodicals, Inc.

No overt structural or functional changes associated with PEG-coated gold nanoparticles accumulation with acute exposure in the mouse heart.

PubMed

Yang, Chengzhi; Yang, Hui; Wu, Jimin; Meng, Zenghui; Xing, Rui; Tian, Aiju; Tian, Xin; Guo, Lijun; Zhang, Youyi; Nie, Guangjun; Li, Zijian

2013-10-24

In this study, we investigated the cardiac biodistribution of polyethylene glycol (PEG)-coated AuNPs and their effects on cardiac function, structure and inflammation in both normal and cardiac remodeling mice. The model of cardiac remodeling was induced by subcutaneously injection of isoproterenol (ISO), a non-selective beta-adrenergic agonist, for 7 days. After AuNPs were injected intravenously in mice for 7 consecutive days, Au content in different organs was determined quantitatively by inductively coupled plasma mass spectrometry (ICP-MS), cardiac function and structure were measured by echocardiography, cardiac fibrosis was examined with picrosirius red staining, the morphology of cardiomyocytes was observed with hematoxylin and eosin (H & E) staining. The accumulation of AuNPs in hearts did not affect cardiac function or induce cardiac hypertrophy, cardiac fibrosis and cardiac inflammation under normal physiological condition. Cardiac AuNPs content was 6-fold higher in the cardiac remodeling mouse than normal mice. However, the increased accumulation of AuNPs in the heart did not aggravate ISO-induced cardiac hypertrophy, cardiac fibrosis or cardiac inflammation. These observations suggest that PEG-coated AuNPs possess excellent biocompatibility under both physiological and pathological conditions. Thus, AuNPs may be safe for cardiac patients and hold great promise for further development for various biomedical applications. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Thin films of Ag–Au nanoparticles dispersed in TiO2: influence of composition and microstructure on the LSPR and SERS responses

NASA Astrophysics Data System (ADS)

Borges, Joel; Ferreira, Catarina G.; Fernandes, João P. C.; Rodrigues, Marco S.; Proença, Manuela; Apreutesei, Mihai; Alves, Eduardo; Barradas, Nuno P.; Moura, Cacilda; Vaz, Filipe

2018-05-01

Thin films containing monometallic (Ag,Au) and bimetallic (Ag–Au) noble nanoparticles were dispersed in TiO2, using reactive magnetron sputtering and post-deposition thermal annealing. The influence of metal concentration and thermal annealing in the (micro)structural evolution of the films was studied, and its correlation with the localized surface plasmon resonance (LSPR) and surface enhanced Raman spectroscopy (SERS) behaviours was evaluated. The Ag/TiO2 films presented columnar to granular microstructures, developing Ag clusters at the surface for higher annealing temperatures. In some cases, the films presented dendrite-type fractal geometry, which led to an almost flat broadband optical response. The Au/TiO2 system revealed denser microstructures, with Au nanoparticles dispersed in the matrix, whose size increased with annealing temperature. This microstructure led to the appearance of LSPR bands, although some Au segregation to the surface hindered this effect for higher concentrations. The structural results of the Ag–Au/TiO2 system suggested the formation of bimetallic Ag–Au nanoparticles, which presence was supported by the appearance of a single narrow LSPR band. In addition, the Raman spectra of Rhodamine-6G demonstrated the viability of these systems for SERS applications, with some indication that the Ag/TiO2 system might be preferential, contrasting to the notorious behaviour of the bimetallic system in terms of LSPR response.

In situ electro-polymerization of nitrogen doped carbon dots and their application in an electrochemiluminescence biosensor for the detection of intracellular lead ions.

PubMed

Xiong, Chengyi; Liang, Wenbin; Wang, Haijun; Zheng, Yingning; Zhuo, Ying; Chai, Yaqin; Yuan, Ruo

2016-04-25

Here, a novel sensitive electrochemiluminescence (ECL) biosensor using N doped carbon dots (N-CDs) in situ electro-polymerized onto a glassy carbon electrode (GCE) as luminophores, and Pd-Au hexoctahedrons (Pd@Au HOHs) as enhancers, was developed for the detection of intracellular lead ions (Pb(2+)).

A plasmonic nanosensor for lipase activity based on enzyme-controlled gold nanoparticles growth in situ

NASA Astrophysics Data System (ADS)

Tang, Yan; Zhang, Wei; Liu, Jia; Zhang, Lei; Huang, Wei; Huo, Fengwei; Tian, Danbi

2015-03-01

A plasmonic nanosensor for lipase activity was developed based on one-pot nanoparticle growth. Tween 80 was selected not only as the substrate for lipase recognition but also as the reducing and stabilizing agent for the sensor fabrication. The different molecular groups in Tween 80 could have different roles in the fabrication procedure; the H2O2 produced by the autoxidation of the ethylene oxide subunits in Tween 80 could reduce the AuCl4- ions to Au atoms, meanwhile, the lipase could hydrolyze its carboxyl ester bond, which could, in turn, control the rate of nucleation of the gold nanoparticles (AuNPs) and tailor the localized surface plasmon resonance (LSPR) of the AuNP transducers. The color changes, which depend on the absence or presence of the lipase, could be used to sense the lipase activity. A linear response ranging from 0.025 to 4 mg mL-1 and a detection limit of the lipase as low as 3.47 μg mL-1 were achieved. This strategy circumvents the problems encountered by general enzyme assays that require sophisticated instruments and complicated assembling steps. The methodology can benefit the assays of heterogeneous-catalyzed enzymes.A plasmonic nanosensor for lipase activity was developed based on one-pot nanoparticle growth. Tween 80 was selected not only as the substrate for lipase recognition but also as the reducing and stabilizing agent for the sensor fabrication. The different molecular groups in Tween 80 could have different roles in the fabrication procedure; the H2O2 produced by the autoxidation of the ethylene oxide subunits in Tween 80 could reduce the AuCl4- ions to Au atoms, meanwhile, the lipase could hydrolyze its carboxyl ester bond, which could, in turn, control the rate of nucleation of the gold nanoparticles (AuNPs) and tailor the localized surface plasmon resonance (LSPR) of the AuNP transducers. The color changes, which depend on the absence or presence of the lipase, could be used to sense the lipase activity. A linear response ranging from 0.025 to 4 mg mL-1 and a detection limit of the lipase as low as 3.47 μg mL-1 were achieved. This strategy circumvents the problems encountered by general enzyme assays that require sophisticated instruments and complicated assembling steps. The methodology can benefit the assays of heterogeneous-catalyzed enzymes. Electronic supplementary information (ESI) available: Zeta potential measurements, optimization of assay conditions, pH-stat method. See DOI: 10.1039/c4nr07579j

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.

Comparison of Practices, Knowledge, Confidence, and Attitude toward Oral Cancer among Oral Health Professionals between Japan and Australia.

PubMed

Haresaku, Satoru; Makino, Michiko; Sugiyama, Seiichi; Naito, Toru; Mariño, Rodrigo Jose

2018-04-01

The purpose of this study was to investigate the practices, knowledge, confidence, and attitude toward oral cancer among Japanese oral health professionals (J-OHPs) and to identify Japanese-specific problems in oral cancer practices by comparing them between Japan and Australia. A questionnaire survey regarding oral cancer practices among Australian oral health professionals (Au-OHPs) was conducted in Australia in 2014-2015. The questionnaire was translated into Japanese, and a Web-based questionnaire survey was conducted among 131 Japanese dentists (J-Dentists) and 131 dental hygienists (J-DHs) in 2016. To compare the J-OHPs' findings with the Au-OHPs', the data of Australian dentists (Au-dentists) and Australian dental hygienists (Au-DHs) were extracted from the Australian survey. Those findings were then compared via a statistical analysis. Eighty-two J-Dentists, 55 J-DHs, 214 Au-Dentists, and 45 Au-DHs participated in this study. Only 34.1 % of J-Dentists and 36.4 % of J-DHs performed oral cancer screenings on their patients; J-OHPs were significantly less likely to perform them than Au-OHPs. The level of knowledge and confidence regarding oral cancer among JOHPs were significantly lower than among Au-OHPs. About 90 % of J-OHPs felt that they needed additional training in oral cancer practices. Less than 40 % of J-OHPs performed oral cancer screenings in their patients. The low level of knowledge and confidence regarding oral cancer among JOHPs may contribute to their low performance of oral cancer practices. Therefore, further education and training programs for oral cancer practices should be provided to Japanese OHPs for the prevention and early detection of oral cancer.

Comparative study of proteasome inhibitory, synergistic antibacterial, synergistic anticandidal, and antioxidant activities of gold nanoparticles biosynthesized using fruit waste materials

PubMed Central

Patra, Jayanta Kumar; Baek, Kwang-Hyun

2016-01-01

The aim of this study was to compare the biological synthesis of gold nanoparticles (AuNPs) generated using the aqueous extracts of outer oriental melon peel (OMP) and peach. The synthesized OMP-AuNPs and peach extract (PE)-AuNPs were characterized by ultraviolet–visible spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray analysis, X-ray powder diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The surface plasmon resonance spectra were obtained at 545 nm and 540 nm for OMP-AuNPs and PE-AuNPs, respectively. The estimated absolute crystallite size of the synthesized AuNPs was calculated to be 78.11 nm for OMP-AuNPs and 39.90 nm for PE-AuNPs based on the Scherer equation of the X-ray powder diffraction peaks. Fourier transform infrared spectroscopy results revealed the involvement of bioactive compounds present in OMP and peach extracts in the synthesis and stabilization of synthesized AuNPs. Both the OMP-AuNPs and PE-AuNPs showed a strong antibacterial synergistic activity when combined with kanamycin (9.38–20.45 mm inhibition zones) and rifampicin (9.52–25.23 mm inhibition zones), and they also exerted a strong synergistic anticandidal activity (10.09–15.47 mm inhibition zones) when combined with amphotericin B against five pathogenic Candida species. Both the OMP-AuNPs and PE-AuNPs exhibited a strong antioxidant potential in terms of 1,1-diphenyl-2-picrylhydraxyl radical scavenging, nitric oxide scavenging, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging, and a reducing power, along with a strong proteasome inhibitory potential that could be useful in cancer drug delivery and cancer treatments. The PE-AuNPs showed comparatively higher activity than OMP-AuNPs, which could be attributed to the presence of rich bioactive compounds in the PE that acted as reducing and capping agents in the synthesis of PE-AuNPs. Overall, the results of the current investigation highlighted a novel green technology for the synthesis of AuNPs using food waste materials and their potential applications in the biomedical, pharmaceutical, and cosmetic industries. PMID:27695326

How lithium atoms affect the first hyperpolarizability of BN edge-doped graphene.

PubMed

Song, Yao-Dong; Wu, Li-Ming; Chen, Qiao-Ling; Liu, Fa-Kun; Tang, Xiao-Wen

2016-01-01

How do lithium atoms affect the first hyperpolarizability (β0) of boron-nitrogen (BN) edge-doped graphene. In this work, using pentacene as graphene model, Lin@BN-1 edge-doped pentacene and Lin@BN-2 edge-doped pentacene (n = 1, 5) were designed to study this problem. First, two models (BN-1 edge-doped pentacene, and BN-2 edge-doped pentacene ) were formed by doping the BN into the pentacene with different order, and then Li@BN-1 edge-doped pentacene and Li@ BN-2 edge-doped pentacene were obtained by substituting the H atom in BN edge-doped pentacene with a Li atom. The results show that the first hyperpolarizabilities of BN-1 edge-doped pentacene and Li@BN-1 edge-doped pentacene were 4059 a.u. and 6249 a.u., respectively; the first hyperpolarizabilities of BN-2 edge-doped pentacene and Li@BN-2 edge-doped pentacene were 2491 a.u. and 4265 a.u., respectively. The results indicate that the effect of Li substitution is to greatly increase the β0 value. To further enhance the first hyperpolarizability, Li5@ BN-1 edge-doped pentacene and Li5@BN-2 edge-doped pentacene were designed, and were found to exhibit considerably larger first hyperpolarizabilities (β0) (12,112 a.u. and 7921a.u., respectively). This work may inspire further study of the nonlinear properties of BN edge-doped graphene.

Multidentate zwitterionic chitosan oligosaccharide modified gold nanoparticles: stability, biocompatibility and cell interactions

NASA Astrophysics Data System (ADS)

Liu, Xiangsheng; Huang, Haoyuan; Liu, Gongyan; Zhou, Wenbo; Chen, Yangjun; Jin, Qiao; Ji, Jian

2013-04-01

Surface engineering of nanoparticles plays an essential role in their colloidal stability, biocompatibility and interaction with biosystems. In this study, a novel multidentate zwitterionic biopolymer derivative is obtained from conjugating dithiolane lipoic acid and zwitterionic acryloyloxyethyl phosphorylcholine to the chitosan oligosaccharide backbone. Gold nanoparticles (AuNPs) modified by this polymer exhibit remarkable colloidal stabilities under extreme conditions including high salt conditions, wide pH range and serum or plasma containing media. The AuNPs also show strong resistance to competition from dithiothreitol (as high as 1.5 M). Moreover, the modified AuNPs demonstrate low cytotoxicity investigated by both MTT and LDH assays, and good hemocompatibility evaluated by hemolysis of human red blood cells. In addition, the intracellular fate of AuNPs was investigated by ICP-MS and TEM. It showed that the AuNPs are uptaken by cells in a concentration dependent manner, and they can escape from endosomes/lysosomes to cytosol and tend to accumulate around the nucleus after 24 h incubation but few of them are excreted out of the cells. Gold nanorods are also stabilized by this ligand, which demonstrates robust dispersion stability and excellent hemocompatibility. This kind of multidentate zwitterionic chitosan derivative could be widely used for stabilizing other inorganic nanoparticles, which will greatly improve their performance in a variety of bio-related applications.Surface engineering of nanoparticles plays an essential role in their colloidal stability, biocompatibility and interaction with biosystems. In this study, a novel multidentate zwitterionic biopolymer derivative is obtained from conjugating dithiolane lipoic acid and zwitterionic acryloyloxyethyl phosphorylcholine to the chitosan oligosaccharide backbone. Gold nanoparticles (AuNPs) modified by this polymer exhibit remarkable colloidal stabilities under extreme conditions including high salt conditions, wide pH range and serum or plasma containing media. The AuNPs also show strong resistance to competition from dithiothreitol (as high as 1.5 M). Moreover, the modified AuNPs demonstrate low cytotoxicity investigated by both MTT and LDH assays, and good hemocompatibility evaluated by hemolysis of human red blood cells. In addition, the intracellular fate of AuNPs was investigated by ICP-MS and TEM. It showed that the AuNPs are uptaken by cells in a concentration dependent manner, and they can escape from endosomes/lysosomes to cytosol and tend to accumulate around the nucleus after 24 h incubation but few of them are excreted out of the cells. Gold nanorods are also stabilized by this ligand, which demonstrates robust dispersion stability and excellent hemocompatibility. This kind of multidentate zwitterionic chitosan derivative could be widely used for stabilizing other inorganic nanoparticles, which will greatly improve their performance in a variety of bio-related applications. Electronic supplementary information (ESI) available: More experimental details for the synthesis of AuNPs and AuNRs. Fig. S1, 1H NMR spectrum of LA-CSO-PC and Fig. S2, FT-IR spectrum of AuNP-LA-CSO-PC. See DOI: 10.1039/c3nr00284e

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.

Preparation and SERS performance of Au NP/paper strips based on inkjet printing and seed mediated growth: The effect of silver ions

NASA Astrophysics Data System (ADS)

Weng, Guojun; Yang, Yue; Zhao, Jing; Zhu, Jian; Li, Jianjun; Zhao, Junwu

2018-04-01

Surface-enhanced Raman scattering (SERS) has been widely used in biomedical sensing with the advantages of high sensitivity and label-free. However, the fabrication of SERS substrates with good Raman activity, reproducibility, and low cost is still under development in practical applications. This paper presents a practicable method for fabricating Au NP/paper strips by using inkjet printing and seed mediated growth. Small gold seed synthesized by borohydride reduction was used as ink and printed on the filter paper. The printed gold seed grew in situ in the growth solution and formed the gold nanoparticle (Au NP)/paper strips. The fabricated paper strip was characterized by diffuse reflectance spectroscopy and scanning electron microscopy (SEM). The diffuse reflectance spectra indicated that the Au NP/paper strips had two local surface plasmon resonance (LSPR) peaks: the short one at around 540 nm and the long one located in the range of 640-840 nm. And the long LSPR peak firstly shifted to red then to blue with the increased concentrations of silver ions in growth solution. From the SEM images, the shape of grown Au NPs was diverse, including sphere, rod, ellipsoid, dimer, trimer, and big aggregates. We thought the short peak came from the LSPR of nanospheres and the transvers LSPR of rod and ellipsoid like particles, while the long peak mainly came from the plasmonic coupling of dimer along the inter-particle axis. The obtained Au NP/paper strip with the long peak located around 650 nm had the highest SERS activity, which could be attributed to the plasmon resonance induced local field enhancement and nanogap effect. Also, the SERS performance results indicated the printed SERS strips exhibited satisfied uniformity and stability, demonstrating the potential of Au NP/paper strip in real-world applications.

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

Alternative catalysts for low-temperature CO-oxidation

NASA Technical Reports Server (NTRS)

Gardner, Steven D.; Hoflund, Gar B.; Schryer, David R.; Schryer, Jacqueline; Upchurch, Billy T.; Brown, David R.

1990-01-01

MnO sub x, Ag/MnO sub x, Cu/MnO sub x, Pt/MnO sub x, Ru/MnO sub x, Au/CeO sub x, and Au/Fe2O3 were synthesized and tested for CO oxidation activity in low concentrations of stoichiometric CO and O2 at 30 to 75 C. Catalytic activity was measured for periods as long as 18000 minutes. At 75 deg Au/MnO sub x is most active sustaining nearly 100 percent CO conversion for 10000 minutes. It also retains high activity at 50 and 30 C with negligible decay in activity. A direct comparison between an unpretreated 10 percent Au/MnO sub x catalyst and an optimized 19.5 percent Pt/SnO sub 2 (pretreated) catalyst shows that the Au/MnO sub x catalyst exhibits much higher catalytic activity and far superior decay characteristics. Other catalysts including Au/CeO sub x and Au/Fe2O3 also perform well. The Cu/MnO sub x exhibits a high initial activity which decays rapidly. After the decay period the activity remains very stable making Cu/MnO sub x a potential candidate for long-term applications such as CO2 lasers in space.

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.

SERS spectral study of HAuCl4-cysteine nanocatalytic reaction and its application for detection of heparin sodium with label-free VB4r molecular probe

NASA Astrophysics Data System (ADS)

Wang, Xiaoliang; Jiang, Caina; Qin, Yanna; Peng, Yutao; Wen, Guiqing; Liang, Aihui; Jiang, Zhiliang

2017-04-01

In the presence of nanocatalyst, L-cysteine reduce HAuCl4 rapidly to form gold nanoparticles (AuNP), and a quick nanocatalytic preparation procedure was established for Au/AuNP sol with highly active surface enhanced Raman scattering (SERS) effect and good stability. The nanoreaction was also studied by absorption, resonance Rayleigh scattering (RRS), transmission electron microscopy (TEM) and energy spectra. In the selected conditions, the analyte heparin sodium (HS) could react with victoria blue 4 R (VB4r) to form associated complexes which have very weak SERS effect to make the SERS signals decrease. The SERS signals at 1617 cm-1 reduced linearly with HS concentration increasing. Upon addition of FeCl3, it hydrolyzed to form stable Fe(OH)3 sol platform that carried SERS active Au/AuNPs to enhance the sensitivity. Accordingly, we established a SERS quantitative analysis method in the sol substrate of Fe(OH)3-Au/AuNPs, with a linear range of 0.5-75 ng/mL HS and a detection limit of 0.2 ng/mL. HS in real samples was determined, with a relative standard deviation of 2.65-7.63% and a recovery of 99.3-101%.

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation

PubMed Central

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-01-01

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures. PMID:25998415

Tailoring plasmonic properties of metal nanoparticle-embedded dielectric thin films: the sandwich method of preparation

NASA Astrophysics Data System (ADS)

Laha, Ranjit; Malar, P.; Osipowicz, Thomas; Kasiviswanathan, S.

2017-09-01

Tailoring of plasmonic properties of metal nanoparticle-embedded dielectric thin films are very crucial for many thin film-based applications. We, herein, investigate the various ways of tuning the plasmonic positions of gold nanoparticles (AuNPs)-embedded indium oxide thin films (Au:IO) through a sequence-specific sandwich method. The sandwich method is a four-step process involving deposition of In2O3 film by magnetron sputtering in first and fourth steps, thermal evaporation of Au on to In2O3 film in second and annealing of Au/In2O3 film in the third step. The Au:IO films were characterized by x-ray diffraction, spectrophotometry and transmission electron microscopy. The size and shape of the embedded nanoparticles were found from Rutherford back-scattering spectrometry. Based on dynamic Maxwell Garnett theory, the observed plasmon resonance position was ascribed to the oblate shape of AuNPs formed in sandwich method. Finally, through experimental data, it was shown that the plasmon resonance position of Au:IO thin films can be tuned by 125 nm. The method shown here can be used to tune the plasmon resonance position over the entire range of visible region for the thin films made from other combinations of metal-dielectric pair.

Inhibition of gold nanoparticles (AuNPs) on pathogenic biofilm formation and invasion to host cells.

PubMed

Yu, Qilin; Li, Jianrong; Zhang, Yueqi; Wang, Yufan; Liu, Lu; Li, Mingchun

2016-05-25

Owing to the growing infectious diseases caused by eukaryotic and prokaryotic pathogens, it is urgent to develop novel antimicrobial agents against clinical pathogenic infections. Biofilm formation and invasion into the host cells are vital processes during pathogenic colonization and infection. In this study, we tested the inhibitory effect of Au nanoparticles (AuNPs) on pathogenic growth, biofilm formation and invasion. Interestingly, although the synthesized AuNPs had no significant toxicity to the tested pathogens, Candida albicans and Pseudomonas aeruginosa, the nanoparticles strongly inhibited pathogenic biofilm formation and invasion to dental pulp stem cells (DPSCs). Further investigations revealed that AuNPs abundantly bound to the pathogen cells, which likely contributed to their inhibitory effect on biofilm formation and invasion. Moreover, treatment of AuNPs led to activation of immune response-related genes in DPSCs, which may enhance the activity of host immune system against the pathogens. Zeta potential analysis and polyethylene glycol (PEG)/polyethyleneimine (PEI) coating tests further showed that the interaction between pathogen cells and AuNPs is associated with electrostatic attractions. Our findings shed novel light on the application of nanomaterials in fighting against clinical pathogens, and imply that the traditional growth inhibition test is not the only way to evaluate the drug effect during the screening of antimicrobial agents.

In Vitro and In Vivo Photothermal Cancer Therapeutic Effects of Gold Nanorods Modified with Mushroom β-Glucan.

PubMed

Li, Xiaojie; Zhou, Jiajing; Dong, Xiaonan; Cheng, Wai-Yin; Duan, Hongwei; Cheung, Peter C K

2018-04-25

The photothermal cancer therapeutic effect of the AuNR-Glu nanohybrids produced by coating native gold nanorods (AuNRs) with a natural mushroom biopolymer from the Pleurotus tuber-regium sclerotia (Glu) were studied in the second near-infrared window (NIR-II). The AuNR-Glu exhibited low cytotoxicity and high biocompatibility due to the surface modification of Glu when compared with the native AuNRs. AuNR-Glu nanohybrids had a high photothermal transduction efficiency (η) of 43.12%, causing effective in vitro cell ablation in both HT-29 (94.2 ± 0.8% cell death) and SW480 (94.8 ± 1.1% cell death) colon cancer cells under 1064 nm NIR-II laser irradiation at 1.0 W/cm 2 . Intravenous injection of AuNR-Glu nanohybrids followed by irradiation from a NIR-II laser at a safe dose (1.0 W/cm 2 for 5 min) in nude mice implanted with HT-29 tumors was effective in significantly reducing the tumor growth, with no obvious harmful side effects, as evidenced by histological analysis of major organs. The present results have shown that AuNRs modified by natural biopolymers from mushroom β-glucans are novel nanomaterials with low cytotoxicity and effective photothermal anticancer agents with potential biomedical applications.

Monolayer-enriched production of Au-decorated WS 2 Nanosheets via Defect Engineering

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

Dunklin, Jeremy R.; Lafargue, Paul; Higgins, Thomas M.

Layered transition metal dichalcogenides (TMDs) represent a diverse, emerging source of two-dimensional (2D) nanostructures with broad application in optoelectronics and energy. Chemical functionalization has evolved into a powerful tool to tailor properties of these 2D TMDs; however, functionalization strategies have been largely limited to the metallic 1T-polytype. The work herein illustrates that 2H-semiconducting liquid-exfoliated tungsten disulfide (WS 2) undergoes a spontaneous redox reaction with gold (III) chloride (AuCl 3). Au nanoparticles (NPs) predominantly nucleate at nanosheet edges with tuneable NP size and density. AuCl 3 is preferentially reduced on multi-layer WS 2 and resulting large Au aggregates are easily separatedmore » from the colloidal dispersion by simple centrifugation. This process may be exploited to enrich the dispersions in laterally large, monolayer nanosheets. It is proposed that thiol groups at edges and defects sides reduce the AuCl 3 to Au 0 and are in turn oxidized to disulfides. Optical emission, i.e. photoluminescence, of the monolayers remained pristine, while the electrocatalytic activity towards the hydrogen evolution reaction is significantly improved. Taken together, these improvements in functionalization, fabrication, and catalytic activity represent an important advance in the study of these emerging 2D nanostructures.« less

Monolayer-enriched production of Au-decorated WS 2 Nanosheets via Defect Engineering

DOE PAGES

Dunklin, Jeremy R.; Lafargue, Paul; Higgins, Thomas M.; ...

2018-04-06

Layered transition metal dichalcogenides (TMDs) represent a diverse, emerging source of two-dimensional (2D) nanostructures with broad application in optoelectronics and energy. Chemical functionalization has evolved into a powerful tool to tailor properties of these 2D TMDs; however, functionalization strategies have been largely limited to the metallic 1T-polytype. The work herein illustrates that 2H-semiconducting liquid-exfoliated tungsten disulfide (WS 2) undergoes a spontaneous redox reaction with gold (III) chloride (AuCl 3). Au nanoparticles (NPs) predominantly nucleate at nanosheet edges with tuneable NP size and density. AuCl 3 is preferentially reduced on multi-layer WS 2 and resulting large Au aggregates are easily separatedmore » from the colloidal dispersion by simple centrifugation. This process may be exploited to enrich the dispersions in laterally large, monolayer nanosheets. It is proposed that thiol groups at edges and defects sides reduce the AuCl 3 to Au 0 and are in turn oxidized to disulfides. Optical emission, i.e. photoluminescence, of the monolayers remained pristine, while the electrocatalytic activity towards the hydrogen evolution reaction is significantly improved. Taken together, these improvements in functionalization, fabrication, and catalytic activity represent an important advance in the study of these emerging 2D nanostructures.« less

Synthesis of double-shelled sea urchin-like yolk-shell Fe3O4/TiO2/Au microspheres and their catalytic applications

NASA Astrophysics Data System (ADS)

Li, Jie; Tan, Li; Wang, Ge; Yang, Mu

2015-03-01

Double-shelled sea urchin-like yolk-shell Fe3O4/TiO2/Au microspheres were successfully synthesized through loading Au nanoparticles on the Fe3O4/TiO2 support by a in situ reduction of HAuCl4 with NaBH4 aqueous solution. These microspheres possess tunable cavity size, adjustable shell layers, high structural stability and large specific surface area. The Au nanoparticles of approximately 5 nm in diameter were loaded both on the TiO2 nanofibers and inside the cavities of sea urchin-like yolk-shell Fe3O4/TiO2 microspheres. The sea urchin-like structure composed of TiO2 nanofibers ensure the good distribution of the Au nanoparticles, while the novel double-shelled yolk-shell structure guarantees the high stability of the Au nanoparticles. Furthermore, the Fe3O4 magnetic core facilitates the convenient recovery of the catalyst by applying an external magnetic field. The Fe3O4/TiO2/Au microspheres display excellent activities and recycling properties in the catalytic reduction of 4-nitrophenol (4-NP): the rate constant is 1.84 min-1 and turnover frequency is 5457 h-1.

Comparison of detection techniques for capillary electrophoresis analysis of gold nanoparticles.

PubMed

Matczuk, Magdalena; Aleksenko, Svetlana S; Matysik, Frank-Michael; Jarosz, Maciej; Timerbaev, Andrei R

2015-05-01

As metallic nanoparticles are growing in importance as analytes in CE, increases an interest in appropriate detection methods for their quantification in various samples. For gold nanoparticles (AuNPs), the most common UV detection poses intricacy of inadequate sensitivity that hinders the applicability of CE. With the objective of resolving this challenge, UV detection was compared with C(4) D and ICP-MS as alternative modes of detection for AuNPs. A C(4) D detector, applied under pressure-driven conditions, exhibited better sensitivity than a UV detector. However, C(4) D turned to be unsatisfactory to differentiate the signal of AuNPs at common CE conditions despite varying the nature of BGE and detection conditions. Due to intrinsic sensitivity and low background levels typical to Au, ICP-MS greatly surpasses UV detection. After optimization trials, CE-ICP-MS gained the LOD of AuNPs as low as 2 × 10(-15) M, as well as an excellent performance in terms of signal stability and linearity. Also importantly, the optimized BGE appears to be well matched to explore the behavior of AuNPs in biologically relevant systems. This was demonstrated by probing the interaction between AuNPs and the main blood-transporting protein, HSA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic field directional discontinuities - Characteristics between 0.46 and 1.0 AU

NASA Technical Reports Server (NTRS)

Lepping, R. P.; Behannon, K. W.

1986-01-01

Based on Mariner 10 data, a statistical survey and an application of the Sonnerup-Cahill variance procedure to a visual identification with 1.2-s averages for time intervals corresponding to the equally spaced heliocentric distances of 1.0, 0.72 and 0.46 AU, are employed to study the characteristics of directional discontinuities (DDs) in the interplanetary magnetic field. Analysis using two methods demonstrated that the ratio of tangential discontinuities (TDs) to rotational discontinuities (RDs) decreased with decreasing radial distance. Decreases in average discontinuity thickness of 41 percent between 1.0 and 0.72 AU, and 56 percent between 1.0 and 0.46 AU, were found for both TDs and RDs, in agreement with Pioneer 10 data between 1 and 5 AU. Normalization of the individual DD thicknesses with respect to the estimated local proton gyroradius (R sub L) gave a nearly constant average thickness at the three locations, 36 + or - 5 R sub L, for both RDs and TDs.