Gold@silver bimetal nanoparticles/pyramidal silicon 3D substrate with high reproducibility for high-performance SERS

NASA Astrophysics Data System (ADS)

Zhang, Chao; Jiang, Shou Zhen; Yang, Cheng; Li, Chong Hui; Huo, Yan Yan; Liu, Xiao Yun; Liu, Ai Hua; Wei, Qin; Gao, Sai Sai; Gao, Xing Guo; Man, Bao Yuan

2016-05-01

A novel and efficient surface enhanced Raman scattering (SERS) substrate has been presented based on Gold@silver/pyramidal silicon 3D substrate (Au@Ag/3D-Si). By combining the SERS activity of Ag, the chemical stability of Au and the large field enhancement of 3D-Si, the Au@Ag/3D-Si substrate possesses perfect sensitivity, homogeneity, reproducibility and chemical stability. Using R6G as probe molecule, the SERS results imply that the Au@Ag/3D-Si substrate is superior to the 3D-Si, Ag/3D-Si and Au/3D-Si substrate. We also confirmed these excellent behaviors in theory via a commercial COMSOL software. The corresponding experimental and theoretical results indicate that our proposed Au@Ag/3D-Si substrate is expected to develop new opportunities for label-free SERS detections in biological sensors, biomedical diagnostics and food safety.

Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions.

PubMed

Brun, Emilie; Cloutier, Pierre; Sicard-Roselli, Cécile; Fromm, Michel; Sanche, Léon

2009-07-23

In this study, we show that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions. Five monolayer films of plasmid DNA (3197 base pairs) deposited on glass and gold substrates are irradiated with 1.5 keV X-rays in ultrahigh vacuum and under atmospheric conditions. The total damage is analyzed by agarose gel electrophoresis. The damage produced on the glass substrate is attributed to energy absorption from X-rays, whereas that produced on the gold substrate arises from energy absorption from both the X-ray beam and secondary electrons emitted from the gold surface. By analysis of the energy of these secondary electrons, 96% are found to have energies below 30 eV with a distribution peaking at 1.4 eV. The differences in damage yields recorded with the gold and glass substrates is therefore essentially attributed to the interaction of low-energy electrons with DNA under vacuum and hydrated conditions. From these results, the G values for low-energy electrons are determined to be four and six strand breaks per 100 eV, respectively.

Photoinduced electron transfer through peptide-based self-assembled monolayers chemisorbed on gold electrodes: directing the flow-in and flow-out of electrons through peptide helices.

PubMed

Venanzi, Mariano; Gatto, Emanuela; Caruso, Mario; Porchetta, Alessandro; Formaggio, Fernando; Toniolo, Claudio

2014-08-21

Photoinduced electron transfer (PET) experiments have been carried out on peptide self-assembled monolayers (SAM) chemisorbed on a gold substrate. The oligopeptide building block was exclusively formed by C(α)-tetrasubstituted α-aminoisobutyric residues to attain a helical conformation despite the shortness of the peptide chain. Furthermore, it was functionalized at the C-terminus by a pyrene choromophore to enhance the UV photon capture cross-section of the compound and by a lipoic group at the N-terminus for linking to gold substrates. Electron transfer across the peptide SAM has been studied by photocurrent generation experiments in an electrochemical cell employing a gold substrate modified by chemisorption of a peptide SAM as a working electrode and by steady-state and time-resolved fluorescence experiments in solution and on a gold-coated glass. The results show that the electronic flow through the peptide bridge is strongly asymmetric; i.e., PET from the C-terminus to gold is highly favored with respect to PET in the opposite direction. This effect arises from the polarity of the Au-S linkage (Au(δ+)-S(δ-), junction effect) and from the electrostatic field generated by the peptide helix.

Surface plasmon resonances of protein-conjugated gold nanoparticles on graphitic substrates

NASA Astrophysics Data System (ADS)

Phan, Anh D.; Hoang, Trinh X.; Nghiem, Thi H. L.; Woods, Lilia M.

2013-10-01

We present theoretical calculations for the absorption properties of protein-coated gold nanoparticles on graphene and graphite substrates. As the substrate is far away from nanoparticles, numerical results show that the number of protein bovine serum molecules aggregating on gold surfaces can be quantitatively determined for gold nanoparticles with arbitrary size by means of the Mie theory and the absorption spectra. The presence of a graphene substrate near the protein-conjugated gold nanoparticles results in a red shift of the surface plasmon resonances of the nanoparticles. This effect can be modulated upon changing the graphene chemical potential. Our findings show that the graphene and graphite affect the absorption spectra in a similar way.

Selective DNA-Mediated Assembly of Gold Nanoparticles on Electroded Substrates

DTIC Science & Technology

2008-06-01

might use the Watson - Crick base-pairing of DNA as a means for ultrahigh-precision engineering is well- known.5,6 The idea is to use the highly specific...Selective DNA -Mediated Assembly of Gold Nanoparticles on Electroded Substrates K. E. Sapsford,†,‡,∇ D. Park,§ E. R. Goldman,‡ E. E. Foos,| S. A...electrodes via DNA hybridization. Protocols are demonstrated for maximizing selectivity and coverage using 15mers as the active binding agents. Detailed

Photonics of 2D gold nanolayers on sapphire surface

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

Muslimov, A. E., E-mail: amuslimov@mail.ru; Butashin, A. V.; Nabatov, B. V.

Gold layers with thicknesses of up to several nanometers, including ordered and disordered 2D nanostructures of gold particles, have been formed on sapphire substrates; their morphology is described; and optical investigations are carried out. The possibility of increasing the accuracy of predicting the optical properties of gold layers and 2D nanostructures using quantum-mechanical models based on functional density theory calculation techniques is considered. The application potential of the obtained materials in photonics is estimated.

Substrate decomposition in galvanic displacement reaction: Contrast between gold and silver nanoparticle formation

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

Ghosh, Tapas; Satpati, Biswarup, E-mail: biswarup.satpati@saha.ac.in; Kabiraj, D.

We have investigated substrate decomposition during formation of silver and gold nanoparticles in galvanic displacement reaction on germanium surfaces. Silver and gold nanoparticles were synthesized by electroless deposition on sputter coated germanium thin film (∼ 200 nm) grown initially on silicon substrate. The nanoparticles formation and the substrate corrosion were studied using scanning transmission electron microscopy (STEM) and the energy dispersive X-ray (EDX) spectroscopy.

Self-organization of gold nanoparticles on silanated surfaces

PubMed Central

Kyaw, Htet H; Sellai, Azzouz; Dutta, Joydeep

2015-01-01

Summary The self-organization of monolayer gold nanoparticles (AuNPs) on 3-aminopropyltriethoxysilane (APTES)-functionalized glass substrate is reported. The orientation of APTES molecules on glass substrates plays an important role in the interaction between AuNPs and APTES molecules on the glass substrates. Different orientations of APTES affect the self-organization of AuNps on APTES-functionalized glass substrates. The as grown monolayers and films annealed in ultrahigh vacuum and air (600 °C) were studied by water contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, UV–visible spectroscopy and ultraviolet photoelectron spectroscopy. Results of this study are fundamentally important and also can be applied for designing and modelling of surface plasmon resonance based sensor applications. PMID:26734526

The adsorption and thermal decomposition of tricresylphosphate (TCP) on iron and gold

NASA Technical Reports Server (NTRS)

Wheeler, D. R.; Faut, O. D.

1983-01-01

Because tricresyl-phosphate (TCP) is a common antiwear additive in lubricants, there is great interest in its interactions with metal substrates. The TCP was allowed to adsorb on polycrystalline iron and gold at room temperature. X-ray photoelectron spectroscopy (XPS) was used to analyze the adsorbed species. The substrate was then heated in steps to 330 C, and the changes in the adsorbate were analyzed after each step. On both substrates saturation adsorption occurred at about one monolayer, but the sticking coefficient was less on gold than on iron. Comparison of the XPS spectra of TCP on each substrate with the spectrum from condensed TCP indicated nondissociative adsorption on gold, possibly by dipole-induced dipole interaction. On iron, there was apparently additional interaction between the substrate and the tolyl groups on the TCP molecule. TCP began to desorb molecularly from gold as soon as the gold was heated above room temperature. The desorption was complete by 200 C. However, when the iron substrate was heated, TCP did not desorb but decomposed between 150 and 250 C.

III-V nanowire synthesis by use of electrodeposited gold particles.

PubMed

Jafari Jam, Reza; Heurlin, Magnus; Jain, Vishal; Kvennefors, Anders; Graczyk, Mariusz; Maximov, Ivan; Borgström, Magnus T; Pettersson, Håkan; Samuelson, Lars

2015-01-14

Semiconductor nanowires are great candidates for building novel electronic devices. Considering the cost of fabricating such devices, substrate reuse and gold consumption are the main concerns. Here we report on implementation of high throughput gold electrodeposition for selective deposition of metal seed particles in arrays defined by lithography for nanowire synthesis. By use of this method, a reduction in gold consumption by a factor of at least 300 was achieved, as compared to conventional thermal evaporation for the same pattern. Because this method also facilitates substrate reuse, a significantly reduced cost of the final device is expected. We investigate the morphology, crystallography, and optical properties of InP and GaAs nanowires grown from electrodeposited gold seed particles and compare them with the properties of nanowires grown from seed particles defined by thermal evaporation of gold. We find that nanowire synthesis, as well as the material properties of the grown nanowires are comparable and quite independent of the gold deposition technique. On the basis of these results, electrodeposition is proposed as a key technology for large-scale fabrication of nanowire-based devices.

Gold/silver/gold trilayer films on nanostructured polycarbonate substrates for direct and label-free nanoplasmonic biosensing.

PubMed

López-Muñoz, Gerardo A; Estévez, M-Carmen; Vázquez-García, Marc; Berenguel-Alonso, Miguel; Alonso-Chamarro, Julián; Homs-Corbera, Antoni; Lechuga, Laura M

2018-05-01

Ultrasmooth gold/silver/gold trilayer nanostructured plasmonic sensors were obtained using commercial Blu-ray optical discs as nanoslits-based flexible polymer substrates. A thin gold film was used as an adhesion and nucleation layer to improve the chemical stability and reduce the surface roughness of the overlying silver film, without increasing ohmic plasmon losses. The structures were physically and optically characterized and compared with nanostructures of single gold layer. Ultrasmooth and chemically stable trilayer nanostructures with a surface roughness <0.5 nm were obtained following a simple and reproducible fabrication process. They showed a figure of merit (FOM) value up to 69.2 RIU -1 which is significantly higher (more than 95%) than the gold monolayer counterpart. Their potential for biosensing was demonstrated by employing the trilayer sensor for the direct and refractometric (label-free) detection of C-reactive protein (CRP) biomarker in undiluted urine achieving a Limit of Detection (LOD) in the pM order. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic and electrochemical characterization of interfacial biomimetic assemblies on electrochemically generated gold oxide surfaces.

PubMed

Krysiński, Paweł; Blanchard, G J

2005-04-01

We report on the formation of a gold oxide layer and the reaction of this oxide with an acid chloride to form a stable, relatively complete monolayer bound through an ester-like bond to the gold oxide surface. We have used cyclic voltammetry, FTIR and optical ellipsometry to characterize this novel monolayer structure. The exposed functional groups of this monolayer can participate in subsequent surface reactions, opening the door to the use of oxide-based surface attachment chemistry on metallic substrates. This chemistry will allow for the formation of films tailored to contain both hydrophobic and hydrophilic regions, stacked at predetermined distances from the substrate that may serve as biomembrane mimetic assemblies.

Disposable gold coated pyramidal SERS sensor on the plastic platform.

PubMed

Oo, S Z; Siitonen, S; Kontturi, V; Eustace, D A; Charlton, M D B

2016-01-11

In this paper we investigate suitability of arrays of gold coated pyramids for surface-enhanced Raman scattering (SERS) sensing applications. Pyramidarrays composed of 1000 nm pit size with 1250 nm pitch lengthwerereplicated on a plastic substrate by roll-to-roll (R2R) ultraviolet (UV) embossing. The level of SERS enhancement, and qualitative performance provided by the new substrate is investigated by comparing Raman spectrum of benzenethiol (BTh) test molecules to the benchmark Klarite SERS substrate which comprises inverted pyramid arrays(1500 nm pit size with 2000 nm pitch length) fabricated on a silicon substrate. The new substrate is found to provide upto 11 times increase in signal in comparison to the inverted pyramid (IV-pyramid) arrays fabricated on an identical plastic substrate. Numerical simulation and experimental evidence suggest that strongly confined electromagnetic fields close to the base of the pyramids, are mainly responsible for the Raman enhancement factor, instead of the fields localized around the tip. Unusually strong plasmon fields are projected upto 200nm from the sidewalls at the base of the pyramid increasing the cross sectional sensing volume.

Gold(I)-catalyzed diazo coupling: strategy towards alkene formation and tandem benzannulation.

PubMed

Zhang, Daming; Xu, Guangyang; Ding, Dong; Zhu, Chenghao; Li, Jian; Sun, Jiangtao

2014-10-06

A gold(I)-catalyzed cross-coupling of diazo compounds to afford tetrasubstituted alkenes has been developed by taking advantage of a trivial electronic difference between two diazo substrates. A N-heterocyclic-carbene-derived gold complex is the most effective catalyst for this transformation. Based on this new strategy, a gold(I)-initiated benzannulation has been achieved through a tandem reaction involving a diazo cross-coupling, 6π electrocyclization, and oxidative aromatization. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Scalable creation of gold nanostructures on high performance engineering polymeric substrate

NASA Astrophysics Data System (ADS)

Jia, Kun; Wang, Pan; Wei, Shiliang; Huang, Yumin; Liu, Xiaobo

2017-12-01

The article reveals a facile protocol for scalable production of gold nanostructures on a high performance engineering thermoplastic substrate made of polyarylene ether nitrile (PEN) for the first time. Firstly, gold thin films with different thicknesses of 2 nm, 4 nm and 6 nm were evaporated on a spin-coated PEN substrate on glass slide in vacuum. Next, the as-evaporated samples were thermally annealed around the glass transition temperature of the PEN substrate, on which gold nanostructures with island-like morphology were created. Moreover, it was found that the initial gold evaporation thickness and annealing atmosphere played an important role in determining the morphology and plasmonic properties of the formulated Au NPs. Interestingly, we discovered that isotropic Au NPs can be easily fabricated on the freestanding PEN substrate, which was fabricated by a cost-effective polymer solution casting method. More specifically, monodispersed Au nanospheres with an average size of ∼60 nm were obtained after annealing a 4 nm gold film covered PEN casting substrate at 220 °C for 2 h in oxygen. Therefore, the scalable production of Au NPs with controlled morphology on PEN substrate would open the way for development of robust flexible nanosensors and optical devices using high performance engineering polyarylene ethers.

Surface Attachment of Gold Nanoparticles Guided by Block Copolymer Micellar Films and Its Application in Silicon Etching

PubMed Central

Wei, Mingjie; Wang, Yong

2015-01-01

Patterning metallic nanoparticles on substrate surfaces is important in a number of applications. However, it remains challenging to fabricate such patterned nanoparticles with easily controlled structural parameters, including particle sizes and densities, from simple methods. We report on a new route to directly pattern pre-formed gold nanoparticles with different diameters on block copolymer micellar monolayers coated on silicon substrates. Due to the synergetic effect of complexation and electrostatic interactions between the micellar cores and the gold particles, incubating the copolymer-coated silicon in a gold nanoparticles suspension leads to a monolayer of gold particles attached on the coated silicon. The intermediate micellar film was then removed using oxygen plasma treatment, allowing the direct contact of the gold particles with the Si substrate. We further demonstrate that the gold nanoparticles can serve as catalysts for the localized etching of the silicon substrate, resulting in nanoporous Si with a top layer of straight pores. PMID:28793407

Measurements of stretch lengths of gold mono-atomic wires covered with 1,6-hexanedithiol in 0.1 M NaClO4 with an electrochemical scanning tunneling microscope.

PubMed

Sun, Jian; Akiba, Uichi; Fujihira, Masamichi

2008-09-01

Stretch lengths of pure gold mono-atomic wires have been studied recently with an electrochemical scanning tunneling microscope (STM). Here, we will report a study of stretch lengths of gold mono-atomic wires with and without 1,6-hexanedithiol (HDT) using the STM break-junction method. First, the stretch length was measured as a function of electrode potentials of a bare Au(111) substrate and a gold STM tip in a 0.1 M NaClO4 aqueous solution. Second, a self-assembled monolayer (SAM) was fabricated on an Au(111) substrate by dipping the substrate into a 1 mM HDT ethanol solution. At last, we measured the stretch length of gold mono-atomic wires on a substrate covered with the SAM in place of the bare Au(111) substrate. We compared the electrode potential dependence of the stretch lengths of gold mono-atomic wires covered with and without HDT. We will discuss the effect of the electrode potential on the stretch lengths by taking account of electrocapillarity of gold mono-atomic wires.

Laser Induced Electrodeposition on Polyimide and GaAs Substrates

DTIC Science & Technology

1983-10-01

6 3.1 Laser Gold Plating on Undoped Ga As Substrate ........... 6 3.1.1 Deposit Formation...22 iv LIST OF ILLUSTRATIONS Figure Page 1. Experimental Set-Up . . . . . .................. 4 2. Laser Gold Pla’ting Undoped GaAs (100...9 3. Laser Gold Plating Undoped GaAs (100) Deposit Resistance Measurement ......................... .10 4. Laser Gold Plating on Polyimide

Gold coatings on polymer laser induced periodic surface structures: assessment as substrates for surface-enhanced Raman scattering.

PubMed

Rebollar, Esther; Sanz, Mikel; Pérez, Susana; Hernández, Margarita; Martín-Fabiani, Ignacio; Rueda, Daniel R; Ezquerra, Tiberio A; Domingo, Concepción; Castillejo, Marta

2012-12-05

We report on the fabrication of gold coated nanostructured polymer thin films and on their characterization as substrates for surface enhanced Raman spectroscopy (SERS). Laser induced periodic surface structures (LIPSS) were obtained on thin polymer films of poly(trimethylene terephthalate) (PTT) upon laser irradiation with the fourth harmonic of a Nd:YAG laser (266 nm, pulse duration 6 ns) resulting in a period close to the incident wavelength. The nanostructured polymer substrates were coated with a nanoparticle assembled gold layer by pulsed laser deposition using the fifth harmonic of a Nd:YAG laser (213 nm, pulse duration 15 ns). Different deposition times resulted in thicknesses from a few nanometres up to several tens of nanometres. Analysis by atomic force microscopy and grazing incident small angle X-ray scattering showed that gold coating preserved the LIPSS relief. The capabilities of the produced nanostructures as substrates for SERS have been investigated using benzenethiol as a test molecule. The SERS signal is substantially larger than that observed for a gold-coated flat substrate. Advantages of this new type of SERS substrates are discussed.

Simultaneous recording of electrical activity and the underlying ionic currents in NG108-15 cells cultured on gold substrate.

PubMed

Acosta-García, Ma Cristina; Morales-Reyes, Israel; Jiménez-Anguiano, Anabel; Batina, Nikola; Castellanos, N P; Godínez-Fernández, R

2018-02-01

This paper shows the simultaneous recording of electrical activity and the underlying ionic currents by using a gold substrate to culture NG108-15 cells. Cells grown on two different substrates (plastic Petri dishes and gold substrates) were characterized quantitatively through scanning electron microscopy (SEM) as well as qualitatively by optical and atomic force microscopy (AFM). No significant differences were observed between the surface area of cells cultured on gold substrates and Petri dishes, as indicated by measurements performed on SEM images. We also evaluated the electrophysiological compatibility of the cells through standard patch-clamp experiments by analyzing features such as the resting potential, membrane resistance, ionic currents, etc. Cells grown on both substrates showed no significant differences in their dependency on voltage, as well as in the magnitude of the Na+ and K+ current density; however, cells cultured on the gold substrate showed a lower membrane capacitance when compared to those grown on Petri dishes. By using two separate patch-clamp amplifiers, we were able to record the membrane current with the conventional patch-clamp technique and through the gold substrate simultaneously. Furthermore, the proposed technique allowed us to obtain simultaneous recordings of the electrical activity (such as action potentials firing) and the underlying membrane ionic currents. The excellent conductivity of gold makes it possible to overcome important difficulties found in conventional electrophysiological experiments such as those presented by the resistance of the electrolytic bath solution. We conclude that the technique here presented constitutes a solution to the problem of the simultaneous recording of electrical activity and the underlying ionic currents, which for decades, had been solved only partially.

Tunable optical metamaterial based on liquid crystal-gold nanosphere composite.

PubMed

Pratibha, R; Park, K; Smalyukh, I I; Park, W

2009-10-26

Effect of the surrounding anisotropic liquid crystal medium on the surface plasmon resonance (SPR) exhibited by concentrated suspensions of gold nanospheres has been investigated experimentally and compared with the Mie scattering theory. The observed polarization-sensitive SPR and the red-shift in the SPR wavelength with increasing concentration of the gold nanospheres in the liquid crystal matrix have been explained using calculations based on the Maxwell Garnet effective medium theory. Agglomeration of the gold nanospheres that could also lead to such a red-shift has been ruled out using Atomic force microscopy study of thin nanoparticle-doped smectic films obtained on solid substrates. Our study demonstrates feasibility of obtaining tunable optical bulk metamaterials based on smectic liquid crystal - nanoparticle composites.

N-Heterocycle-Fused Pentalenes by a Gold-Catalyzed Annulation of Diethynyl-Quinoxalines and -Phenazines.

PubMed

Sekine, Kohei; Stuck, Fabian; Schulmeister, Jürgen; Wurm, Thomas; Zetschok, Dominik; Rominger, Frank; Rudolph, Matthias; Hashmi, A Stephen K

2018-06-19

The gold-catalyzed annulation of diethynyl N-heterocycles for the synthesis of quinoxaline-/phenazine-based pentalenes, and the study of their optoelectronic properties is described. The inhibition of the gold catalyst by the nitrogen centers in the substrate and the product could be overcome by increasing the reaction temperature to 130 °C, which in gold catalysis usually leads to catalyst decomposition. At 130 °C 6,7-di(arylethynyl)quinoxalines in chlorobenzene at afford the corresponding pentalenes. The annulation of 2,3-di(arylethynyl)quinoxalines requires an even higher temperature under microwave irradiation. The quinoxaline-based pentalenes showed lower LUMO levels compared to the corresponding naphthalene-based pentalenes. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of substrate on the femtosecond laser-induced damage properties of gold films

NASA Astrophysics Data System (ADS)

Huang, Haopeng; Wang, Leilei; Kong, Fanyu; Xia, Zhilin; Jin, Yunxia; Xu, Jiao; Chen, Junming; Cui, Yun; Shao, Jianda

2018-07-01

In this work, gold films on two different types of substrates were fabricated by electron beam (e-beam) evaporation, and the femtosecond laser-induced damage properties were evaluated. The first sample was gold film deposited on fused silica, whereas the second was gold deposited on photoresist. 1-on-1 damage tests were implemented by an 800 ± 30 nm laser with pulse duration of 30 fs. Different damage thresholds and morphologies were obtained for the two samples. The damage threshold of the gold film on fused silica was 0.64 J/cm2, with the typical damage morphology of thermal ablation and melting; the damage threshold of the gold film on photoresist was 0.30 J/cm2, with the typical damage morphology of blisters or peeling off. In order to better understand the impact of the substrate on the properties of the whole sample, the normalized electric field intensity, temperature, and thermal stress distributions were calculated. The adhesion between the gold film and substrate were measured and the experimental results well agreed with the theoretical analysis. The results indicate that gold films deposited onto grating-structured fused silica will have more powerful laser damage resistance performance.

X-ray Photoelectron Spectroscopy Analysis of Gold Surfaces after Removal of Thiolated DNA Oligomers by Ultraviolet/Ozone Treatment

PubMed Central

Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Sanche, Léon

2012-01-01

Well ordered films of molecular DNA can be formed by the attachment of thiolated DNA oligonucleotides to a supporting gold substrate. The gold substrate represents a significant fraction of the total cost of preparing such films and it is thus important to determine whether such substrates can be reused. Here we investigate with X-ray Photoelectron Spectroscopy the suitability of UV/ozonolysis previously employed to remove alkanethiols from gold, for removing 40-mer, single and double stranded synthetic DNA. We find that while UV/O3 can indeed remove thiolated DNA from gold slides, the treatment times required permit the implantation of additional organic contaminants. PMID:20000594

X-ray photoelectron spectroscopy analysis of gold surfaces after removal of thiolated DNA oligomers by ultraviolet/ozone treatment.

PubMed

Mirsaleh-Kohan, Nasrin; Bass, Andrew D; Sanche, Léon

2010-05-04

Well-ordered films of molecular DNA can be formed by the attachment of thiolated DNA oligonucleotides to a supporting gold substrate. The gold substrate represents a significant fraction of the total cost of preparing such films, and it is thus important to determine whether such substrates can be reused. Here, we investigate with X-ray photoelectron spectroscopy the suitability of UV/ozonolysis previously employed to remove alkanethiols from gold, for removing 40-mer, single- and double-stranded synthetic DNA. We find that while UV/O(3) can indeed remove thiolated DNA from gold slides, the treatment times required permit the implantation of additional organic contaminants.

Simultaneous detection of multiple biomarkers by means of SERS on polymer nanopillar gold arrays

NASA Astrophysics Data System (ADS)

Morasso, Carlo; Picciolini, Silvia; Mehn, Dora; Pellacani, Paola; Frangolho, Ana; Marchesini, Gerardo; Vanna, Renzo; Gualerzi, Alice; Bedoni, Marzia; Marabelli, Franco; Gramatica, Furio

2016-03-01

The detection of biomarkers by means of Surface Enhanced Raman Spectroscopy (SERS) is foreseen to became a very important tool in the clinical practice because of its excellent sensitivity and potential for the simultaneous detection of multiple biomarkers. In the present paper we describe how it was possible to build a sensor for the detection of genetic biomarkers involved in acute myeloid leukemia. The assay is based on the use of a specifically designed SERS substrate made of a 2D crystal structure of polymeric pillars embedded in a gold layer. This substrate is characterized by good enhancing properties coupled with an excellent homogeneity. The SERS substrate was conjugated with DNA probes complementary to a target sequence and used in a sandwich assay with gold nanoparticles labeled with a second DNA probe and a Raman reporter. The so developed assay allowed the detection of a leukemia biomarker (WT1 gene) and an housekeeping gene with low picomolar sensitivity. At last, we optimized the assay in order to tackle one of the main limitations of SERS based assay: the loss of signal that is observed when the Raman spectra are collected in liquid. Combining a preferential functionalization on the polymeric pillars with a different height of the polymer pillars from the gold layer the assay demonstrated its effectiveness even when measured in buffer.

Tribological characteristics of gold films deposited on metals by ion plating and vapor deposition

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1984-01-01

The graded interface between an ion-plated film and a substrate is discussed as well as the friction and wear properties of ion-plated gold. X-ray photoelectron spectroscopy (XPS) depth profiling and microhardness depth profiling were used to investigate the interface. The friction and wear properties of ion-plated and vapor-deposited gold films were studied both in an ultra high vacuum system to maximize adhesion and in oil to minimize adhesion. The results indicate that the solubility of gold on the substrate material controls the depth of the graded interface. Thermal diffusion and chemical diffusion mechanisms are thought to be involved in the formation of the gold-nickel interface. In iron-gold graded interfaces the gold was primarily dispersed in the iron and thus formed a physically bonded interface. The hardness of the gold film was influenced by its depth and was also related to the composition gradient between the gold and the substrate. The graded nickel-gold interface exhibited the highest hardness because of an alloy hardening effect. The effects of film thickness on adhesion and friction were established.

Tribological characteristics of gold films deposited on metals by ion plating and vapor deposition

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1986-01-01

The graded interface between an ion-plated film and a substrate is discussed as well as the friction and wear properties of ion-plated gold. X-ray photoelectron spectroscopy (XPS) depth profiling and microhardness depth profiling were used to investigate the interface. The friction and wear properties of ion-plated and vapor-deposited gold films were studied both in an ultra high vacuum system to maximize adhesion and in oil to minimize adhesion. The results indicate that the solubility of gold on the substrate material controls the depth of the graded interface. Thermal diffusion and chemical diffusion mechanisms are thought to be involved in the formation of the gold-nickel interface. In iron-gold graded interfaces the gold was primarily dispersed in the iron and thus formed a physically bonded interface. The hardness of the gold film was influenced by its depth and was also related to the composition gradient between the gold and the substrate. The graded nickel-gold interface exhibited the highest hardness because of an alloy hardening effect. The effects of film thickness on adhesion and friction were established.

Structural and dynamical characterization of water on the Au (100) and graphene surfaces: A molecular dynamics simulation approach

NASA Astrophysics Data System (ADS)

Foroutan, Masumeh; Darvishi, Mehdi; Fatemi, S. Mahmood

2017-09-01

The positioning, adsorption, and movement of water on substrates is dependent upon the chemical nature and arrangement of the atoms of the surface. Therefore the behavior of water molecules on a substrate is a reflection of properties of the surface. Based on this premise, graphene and gold substrates were chosen to study this subject from a molecular perspective. In this work, the structural and dynamical behaviors of a water nanodroplet on Au (100) and the graphene interfaces have been studied by molecular dynamics simulation. The results have shown how the structural and dynamical behaviors of water molecules at the interface reflect the characteristics of these surfaces. The results have demonstrated that residence time and hydrogen bonds' lifetime at the water-Au (100) interface are bigger than at the water-graphene interface. Energy contour map analysis indicates a more uniform surface energy on graphene than on the gold surface. The obtained results illustrate that water clusters on gold and graphene form tetramer and hexamer structures, respectively. Furthermore, the water molecules are more ordered on the gold surface than on graphene. The study of hydrogen bonds showed that the order, stability, and the number of hydrogen bonds is higher on the gold surface. The positioning pattern of water molecules is also similar to the arrangement of gold atoms while no regularity was observed on graphene. The study of dynamical behavior of water molecules revealed that the movement of water on gold is much less than on graphene which is in agreement with the strong water-gold interaction in comparison to the water-graphene interaction.

Fabrication of patterned surface by soft lithographic technique for confinement of lipid bilayer

NASA Astrophysics Data System (ADS)

Moulick, Ranjita Ghosh; Mayer, Dirk

2018-04-01

In this paper we demonstrated that a 3D pattern can be well transferred from a silicon Master to a gold substrate using µcontact printing. In this process 1-Octadecanthiol served as an ink and printing followed by etching generated the desired pattern on the gold substrate. The prepatterned substrate was also used for lipid vesicle fusion and revealed that lipid molecules selectively bind to the gold layer.

Large area nano-patterning /writing on gold substrate using dip - pen nanolithography (DPN)

NASA Astrophysics Data System (ADS)

Saini, Sudhir Kumar; Vishwakarma, Amit; Agarwal, Pankaj B.; Pesala, Bala; Agarwal, Ajay

2014-10-01

Dip Pen Nanolithography (DPN) is utilized to pattern large area (50μmX50μm) gold substrate for application in fabricating Nano-gratings. For Nano-writing 16-MHA ink coated AFM tip was prepared using double dipping procedure. Gold substrate is fabricated on thermally grown SiO2 substrate by depositing ˜5 nm titanium layer followed by ˜30nm gold using DC pulse sputtering. The gratings were designed using period of 800nm and 25% duty cycle. Acquired AFM images indicate that as the AFM tip proceeds for nano-writing, line width decreases from 190nm to 100nm. This occurs probably due to depreciation of 16-MHA molecules in AFM tip as writing proceeds.

Modeling the electrical resistance of gold film conductors on uniaxially stretched elastomeric substrates

NASA Astrophysics Data System (ADS)

Cao, Wenzhe; Görrn, Patrick; Wagner, Sigurd

2011-05-01

The electrical resistance of gold film conductors on polydimethyl siloxane substrates at stages of uniaxial stretching is measured and modeled. The surface area of a gold conductor is assumed constant during stretching so that the exposed substrate takes up all strain. Sheet resistances are calculated from frames of scanning electron micrographs by numerically solving for the electrical potentials of all pixels in a frame. These sheet resistances agree sufficiently well with values measured on the same conductors to give credence to the model of a stretchable network of gold links defined by microcracks.

Sugar microarray via click chemistry: molecular recognition with lectins and amyloid β (1-42)

NASA Astrophysics Data System (ADS)

Matsumoto, Erino; Yamauchi, Takahiro; Fukuda, Tomohiro; Miura, Yoshiko

2009-06-01

Sugar microarrays were fabricated on various substrates via click chemistry. Acetylene-terminated substrates were prepared by forming self-assembled monolayers (SAMs) on a gold substrate with alkyl-disulfide and on silicon, quartz and glass substrates with a silane-coupling reagent. The gold substrates were subjected to surface plasmon resonance measurements, and the quartz and glass substrates were subjected to spectroscopy measurements and optical microscopy observation. The saccharide-immobilized substrate on the gold substrate showed specific interaction with the corresponding lectin, and the saccharides showed inert surface properties to other proteins with a high signal-to-noise ratio. We also focused on the saccharide-protein interaction on protein amyloidosis of Alzheimer amyloid β. Amyloid β peptide showed conformation transition on the saccharide-immobilization substrate into a β-sheet, and fibril formation and amyloid aggregates were found on the specific saccharides.

Gold coated metal nanostructures grown by glancing angle deposition and pulsed electroplating

NASA Astrophysics Data System (ADS)

Grüner, Christoph; Reeck, Pascal; Jacobs, Paul-Philipp; Liedtke, Susann; Lotnyk, Andriy; Rauschenbach, Bernd

2018-05-01

Nickel based nanostructures are grown by glancing angle deposition (GLAD) on flat and pre-patterned substrates. These fabricated porous thin films were subsequently coated by pulsed electroplating with gold. The morphology and conformity of the gold coating were investigated by scanning electron microscopy and X-ray diffraction. Controlled growth of closed gold layers on the nanostructures could be achieved, while the open-pore structure of the nanosculptured thin films was preserved. Such gold coated nanostructures are a candidate for optical sensing and catalysis applications. The demonstrated method can be applied for numerous material combinations, allowing to provide GLAD thin films with new surface properties.

Rational design of Raman-labeled nanoparticles for a dual-modality, light scattering immunoassay on a polystyrene substrate.

PubMed

Israelsen, Nathan D; Wooley, Donald; Hanson, Cynthia; Vargis, Elizabeth

2016-01-01

Surface-enhanced Raman scattering (SERS) is a powerful light scattering technique that can be used for sensitive immunoassay development and cell labeling. A major obstacle to using SERS is the complexity of fabricating SERS probes since they require nanoscale characterization and optical uniformity. The light scattering response of SERS probes may also be modulated by the substrate used for SERS analysis. A typical SERS substrate such as quartz can be expensive. Polystyrene is a cheaper substrate option but can decrease the SERS response due to interfering Raman emission peaks and high background fluorescence. The goal of this research is to develop an optimized process for fabricating Raman-labeled nanoparticles for a SERS-based immunoassay on a polystyrene substrate. We have developed a method for fabricating SERS nanoparticle probes for use in a light scattering immunoassay on a polystyrene substrate. The light scattering profile of both spherical gold nanoparticle and gold nanorod SERS probes were characterized using Raman spectroscopy and optical absorbance spectroscopy. The effects of substrate interference and autofluorescence were reduced by selecting a Raman reporter with a strong light scattering response in a spectral region where interfering substrate emission peaks are minimized. Both spherical gold nanoparticles and gold nanorods SERS probes used in the immunoassay were detected at labeling concentrations in the low pM range. This analytical sensitivity falls within the typical dynamic range for direct labeling of cell-surface biomarkers using SERS probes. SERS nanoparticle probes were fabricated to produce a strong light scattering signal despite substrate interference. The optical extinction and inelastic light scattering of these probes was detected by optical absorbance spectroscopy and Raman spectroscopy, respectively. This immunoassay demonstrates the feasibility of analyzing strongly enhanced Raman signals on polystyrene, which is an inexpensive yet non-ideal Raman substrate. The assay sensitivity, which is in the low pM range, suggests that these SERS probe particles could be used for Raman labeling of cell or tissue samples in a polystyrene tissue culture plate. With continued development, this approach could be used for direct labeling of multiple cell surface biomarkers on strongly interfering substrate platforms.

Cold welding of gold nanoparticles on mica substrate: Self-adjustment and enhanced diffusion

PubMed Central

Cha, Song-Hyun; Park, Youmie; Han, Jeong Woo; Kim, Kyeounghak; Kim, Hyun-Seok; Jang, Hong-Lae; Cho, Seonho

2016-01-01

From the images of HR-TEM, FE-SEM, and AFM, the cold welding of gold nanoparticles (AuNPs) on a mica substrate is observed. The cold-welded gold nanoparticles of 25 nm diameters are found on the mica substrate in AFM measurement whereas the size of cold welding is limited to 10 nm for nanowires and 2~3 nm for nanofilms. Contrary to the nanowires requiring pressure, the AuNPs are able to rotate freely due to the attractive forces from the mica substrate and thus the cold welding goes along by adjusting lattice structures. The gold nanoparticles on the mica substrate are numerically modeled and whose physical characteristics are obtained by the molecular dynamic simulations of LAMMPS. The potential and kinetic energies of AuNPs on the mica substrate provide sufficient energy to overcome the diffusion barrier of gold atoms. After the cold welding, the regularity of lattice structure is maintained since the rotation of AuNPs is allowed due to the presence of mica substrate. It turns out that the growth of AuNPs can be controlled arbitrarily and the welded region is nearly perfect and provides the same crystal orientation and strength as the rest of the nanostructures. PMID:27597438

Cold welding of gold nanoparticles on mica substrate: Self-adjustment and enhanced diffusion

NASA Astrophysics Data System (ADS)

Cha, Song-Hyun; Park, Youmie; Han, Jeong Woo; Kim, Kyeounghak; Kim, Hyun-Seok; Jang, Hong-Lae; Cho, Seonho

2016-09-01

From the images of HR-TEM, FE-SEM, and AFM, the cold welding of gold nanoparticles (AuNPs) on a mica substrate is observed. The cold-welded gold nanoparticles of 25 nm diameters are found on the mica substrate in AFM measurement whereas the size of cold welding is limited to 10 nm for nanowires and 2~3 nm for nanofilms. Contrary to the nanowires requiring pressure, the AuNPs are able to rotate freely due to the attractive forces from the mica substrate and thus the cold welding goes along by adjusting lattice structures. The gold nanoparticles on the mica substrate are numerically modeled and whose physical characteristics are obtained by the molecular dynamic simulations of LAMMPS. The potential and kinetic energies of AuNPs on the mica substrate provide sufficient energy to overcome the diffusion barrier of gold atoms. After the cold welding, the regularity of lattice structure is maintained since the rotation of AuNPs is allowed due to the presence of mica substrate. It turns out that the growth of AuNPs can be controlled arbitrarily and the welded region is nearly perfect and provides the same crystal orientation and strength as the rest of the nanostructures.

Cold welding of gold nanoparticles on mica substrate: Self-adjustment and enhanced diffusion.

PubMed

Cha, Song-Hyun; Park, Youmie; Han, Jeong Woo; Kim, Kyeounghak; Kim, Hyun-Seok; Jang, Hong-Lae; Cho, Seonho

2016-09-06

From the images of HR-TEM, FE-SEM, and AFM, the cold welding of gold nanoparticles (AuNPs) on a mica substrate is observed. The cold-welded gold nanoparticles of 25 nm diameters are found on the mica substrate in AFM measurement whereas the size of cold welding is limited to 10 nm for nanowires and 2~3 nm for nanofilms. Contrary to the nanowires requiring pressure, the AuNPs are able to rotate freely due to the attractive forces from the mica substrate and thus the cold welding goes along by adjusting lattice structures. The gold nanoparticles on the mica substrate are numerically modeled and whose physical characteristics are obtained by the molecular dynamic simulations of LAMMPS. The potential and kinetic energies of AuNPs on the mica substrate provide sufficient energy to overcome the diffusion barrier of gold atoms. After the cold welding, the regularity of lattice structure is maintained since the rotation of AuNPs is allowed due to the presence of mica substrate. It turns out that the growth of AuNPs can be controlled arbitrarily and the welded region is nearly perfect and provides the same crystal orientation and strength as the rest of the nanostructures.

Surface-enhanced Raman scattering of amorphous silica gel adsorbed on gold substrates for optical fiber sensors

NASA Astrophysics Data System (ADS)

Degioanni, S.; Jurdyc, A. M.; Cheap, A.; Champagnon, B.; Bessueille, F.; Coulm, J.; Bois, L.; Vouagner, D.

2015-10-01

Two kinds of gold substrates are used to produce surface-enhanced Raman scattering (SERS) of amorphous silica obtained via the sol-gel route using tetraethoxysilane Si(OC2H5)4 (TEOS) solution. The first substrate consists of a gold nanometric film elaborated on a glass slide by sputter deposition, controlling the desired gold thickness and sputtering current intensity. The second substrate consists of an array of micrometer-sized gold inverted pyramidal pits able to confine surface plasmon (SP) enhancing electric field, which results in a distribution of electromagnetic energy inside the cavities. These substrates are optically characterized to observe SPR with, respectively, extinction and reflectance spectrometries. Once coated with thin layers of amorphous silica (SiO2) gel, these samples show Raman amplification of amorphous SiO2 bands. This enhancement can occur in SERS sensors using amorphous SiO2 gel as shells, spacers, protective coatings, or waveguides, and represents particularly a potential interest in the field of Raman distributed sensors, which use the amorphous SiO2 core of optical fibers as a transducer to make temperature measurements.

Formation of gold grating structures on fused silica substrates by femtosecond laser irradiation

NASA Astrophysics Data System (ADS)

Takami, Akihiro; Nakajima, Yasutaka; Terakawa, Mitsuhiro

2017-05-01

Despite the attractive optical properties of gold nanostructures for emerging applications, the formation of sharp laser-induced periodic gold structures has not been reported. In this study, we experimentally demonstrate the formation of micro- and nanoscale periodic gold grating structures on fused silica substrates using a femtosecond laser. The experimental and calculated results show good agreement, indicating that the gold grating structures were formed by a beat formed in a gold thin film. We also propose that the beat was formed by interference of two surface plasmon polaritons with different periods excited in a gold thin film and calculated their periods.

Conductive scanning probe microscopy of the semicontinuous gold film and its SERS enhancement toward two-step photo-induced charge transfer and effect of the supportive layer

NASA Astrophysics Data System (ADS)

Sinthiptharakoon, K.; Sapcharoenkun, C.; Nuntawong, N.; Duong, B.; Wutikhun, T.; Treetong, A.; Meemuk, B.; Kasamechonchung, P.; Klamchuen, A.

2018-05-01

The semicontinuous gold film, enabling various electronic applications including development of surface-enhanced Raman scattering (SERS) substrate, is investigated using conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM) to reveal and investigate local electronic characteristics potentially associated with SERS generation of the film material. Although the gold film fully covers the underlying silicon surface, CAFM results reveal that local conductivity of the film is not continuous with insulating nanoislands appearing throughout the surface due to incomplete film percolation. Our analysis also suggests the two-step photo-induced charge transfer (CT) play the dominant role in the enhancement of SERS intensity with strong contribution from free electrons of the silicon support. Silicon-to-gold charge transport is illustrated by KPFM results showing that Fermi level of the gold film is slightly inhomogeneous and far below the silicon conduction band. We propose that inhomogeneity of the film workfunction affecting chemical charge transfer between gold and Raman probe molecule is associated with the SERS intensity varying across the surface. These findings provide deeper understanding of charge transfer mechanism for SERS which can help in design and development of the semicontinuous gold film-based SERS substrate and other electronic applications.

Gold cleaning methods for preparation of cell culture surfaces for self-assembled monolayers of zwitterionic oligopeptides.

PubMed

Enomoto, Junko; Kageyama, Tatsuto; Myasnikova, Dina; Onishi, Kisaki; Kobayashi, Yuka; Taruno, Yoko; Kanai, Takahiro; Fukuda, Junji

2018-05-01

Self-assembled monolayers (SAMs) have been used to elucidate interactions between cells and material surface chemistry. Gold surfaces modified with oligopeptide SAMs exhibit several unique characteristics, such as cell-repulsive surfaces, micropatterns of cell adhesion and non-adhesion regions for control over cell microenvironments, and dynamic release of cells upon external stimuli under culture conditions. However, basic procedures for the preparation of oligopeptide SAMs, including appropriate cleaning methods of the gold surface before modification, have not been fully established. Because gold surfaces are readily contaminated with organic compounds in the air, cleaning methods may be critical for SAM formation. In this study, we examined the effects of four gold cleaning methods: dilute aqua regia, an ozone water, atmospheric plasma, and UV irradiation. Among the methods, UV irradiation most significantly improved the formation of oligopeptide SAMs in terms of repulsion of cells on the surfaces. We fabricated an apparatus with a UV light source, a rotation table, and HEPA filter, to treat a number of gold substrates simultaneously. Furthermore, UV-cleaned gold substrates were capable of detaching cell sheets without serious cell injury. This may potentially provide a stable and robust approach to oligopeptide SAM-based experiments for biomedical studies. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Fabrication of flexible gold nanorods polymer metafilm via phase transfer method as SERS substrate for detecting food contaminants.

PubMed

Yang, Nan; You, Ting-Ting; Gao, Yu-Kun; Zhang, Chen-Meng; Yin, Penggang

2018-06-08

Surface enhanced Raman scattering (SERS) has been widely used in detection of food safety due to the nondestructive examination property. Here, we reported a flexible SERS film based on polymer immobilized gold nanorods polymer metafilm. Polystyrene-polyisoprene-polystyrene (SIS), a transparent and flexible along with excellent elasticity polymer was chosen as main support of gold nanorods. A simple phase transfer progress was adopted to mix the gold nanorods with polymer which can further used in most water-insoluble polymers. The SERS film performed satisfactorily while tested in a series of standard Raman probes like crystal violet (CV) and malachite green (MG). Moreover, the excellent reproducibility and elastic properties make the film promising substrates in practical detection. Hence, the MG detection on fish surface and trace thiram detection on orange pericarp were inspected with the detection result of 1 × 10-10 M and 1 × 10-6 M which below the demand of National standard of China, exactly matching the realistic application requirements.

Nanostructured gold and platinum electrodes on silicon structures for biosensing

NASA Astrophysics Data System (ADS)

Ogurtsov, V. I.; Sheehan, M. M.

2005-01-01

Gold and platinum metal electrodes on Si/SiO2 having undergone anisotropic potassium hydroxide (KOH) etch treatment are considered. This treatment etches at different rates and directions in the material resulting in creation of numerous pyramid shaped holes in the silicon substrate. This surface is used to make metal electrodes with increased electrode efficiency. The electrodes can serve as the sensors or as the sensor substrates (for surface polymer modification) and because both gold and platinum are inert they have applications for food safety biosensing. Wine, an economically significant food product, was chosen as a matrix, and impedance spectroscopy (EIS) was selected as a method of investigation of electrode behaviour. Based on results of EIS, different complexity equivalent circuits were determined by applying fitting mean square root optimisation of sensor complex impedance measurements.

Gold/silver coated nanoporous ceramic membranes: a new substrate for SERS studies

NASA Astrophysics Data System (ADS)

Kassu, A.; Robinson, P.; Sharma, A.; Ruffin, P. B.; Brantley, C.; Edwards, E.

2010-08-01

Surface Enhanced Raman Scattering (SERS) is a recently discovered powerful technique which has demonstrated sensitivity and selectivity for detecting single molecules of certain chemical species. This is due to an enhancement of Raman scattered light by factors as large as 1015. Gold and Silver-coated substrates fabricated by electron-beam lithography on Silicon are widely used in SERS technique. In this paper, we report the use of nanoporous ceramic membranes for SERS studies. Nanoporous membranes are widely used as a separation membrane in medical devices, fuel cells and other studies. Three different pore diameter sizes of commercially available nanoporous ceramic membranes: 35 nm, 55nm and 80nm are used in the study. To make the membranes SERS active, they are coated with gold/silver using sputtering techniques. We have seen that the membranes coated with gold layer remain unaffected even when immersed in water for several days. The results show that gold coated nanoporous membranes have sensitivity comparable to substrates fabricated by electron-beam lithography on Silicon substrates.

High-Performance, Large Format Surfaces for Surface-Enhanced Raman Spectroscopy: Increasing the Accessibility of an Analytical Platform

NASA Astrophysics Data System (ADS)

Kanipe, Katherine Nicole

Although surface-enhanced Raman spectroscopy (SERS) is a spectroscopic technique with unusually high sensitivity and molecular specificity, few practical analytical applications have been implemented that take advantage of its power. Based on what is understood about SERS from the experimental and theoretical research of the past forty years, we developed a few well-defined design principles on the basis of which a reliable and reproducibly manufacturable SERS-active substrate could be fabricated that is highly enhancing, highly uniform, stable, and based on a broad range of metals so that various chemical processes could be probed. Finally, we restricted ourselves to using only readily scalable fabrication techniques. The resulting SERS-active device was a metal over silica, two-dimensional nano-grating that was shown to produce enhancements of ˜107 when compared to a smooth surface of the same metal. This SERS substrate also shows unprecedented signal uniformity over square centimeters, and is fabricated using commonly-available foundry-based approaches exclusively. Initially, we explored the properties of a gold-coated substrates in which a first-order grating resonance due to long-range symmetry is augmented by a local resonance due to the individual core-shell grating elements. The SERS properties of such grating systems were systematically studied as a function of various structural parameters such as the grating pitch, the inter-element gap and the thickness of the metal layer. The most enhancing substrates were found to have a grating parameter with a radiative, rather than evanescent, first-order resonance; a sufficiently small gap between nearest neighbor grating elements to produce near-field interactions; and a gold layer whose thickness was larger than the electronic mean-free-path of the conduction electrons, so as to ensure a high conductivity for the metal layer to sustain strong surface plasmons. We applied these same architectural principles to metals other than gold, and concluded that every workable metal (and virtually any material with sufficiently high electrical conductivity) when appropriately nanostructured, has the potential to be an efficient SERS substrate. The use of materials for SERS beyond silver and gold, has significant advantages, most importantly, allowing SERS to be used to study the surface chemistry and catalysis taking place on metals with more interesting chemistries than those of Au and Ag. Additionally, SERS substrates can be fabricated from high natural abundance, low cost materials. This was illustrated by producing SERS substrates using copper, aluminum, and nickel in addition to silver and gold which were used as benchmarks. All five metals were found to yield high SERS intensities. The variation of the SERS enhancement among them is ascribed mainly to local field effects, with the (larger) grating-based enhancement making an approximately equivalent contribution to the SERS enhancement of the five metals. This conclusion is supported by local electric field simulations. The utility of these new grating-based SERS substrates was demonstrated by implementing them in chemical analysis in both aqueous and gas phases for which, for example, we were able to readily detect opioids such as fentanyl and morphine at concentrations as low as less than one part per billion. Additionally, we have made good progress toward integration of this substrate architecture into a microfluidic channel for a higher degree of sample workup and control.

Sensing based on surface-enhanced Raman scattering using self-forming ZnO nanoarrays coated with gold as substrates

NASA Astrophysics Data System (ADS)

Tang, Feng; Adam, Pierre-Michel; Rogers, David J.; Sandana, Vinod E.; Bove, Philippe; Teherani, Ferechteh H.

2018-03-01

Surface-Enhanced Raman spectroscopy (SERS) is a widely used technique adopted in both academia and industry for the detection of trace quantities of Raman active molecules. This is usually accomplished by functionalizing distributions of plasmonic metal nanoparticles with the analyte molecules. Recently metal-coated nanostructures have been investigated as alternatives to dispersions of metal nanoparticles in order to avoid clustering and homogeneity/reproducibility issues. In this paper, several samples of Au-coated ZnO nanoarrays are adopted as SERS substrates in order to investigate the molecular sensing capacity for methylene blue (MB) molecules. Self-forming ZnO nanoarrays were grown on both c-sapphire and silicon substrates by pulsed laser deposition. The nanoarrays were then coated with 30 nm of gold using thermal evaporation and the SERS signals of MB functionalized samples were obtained with a Raman microspectrometer. The ratio of SERS intensity to that of an MB functionalized glass substrate (ISERS/IRaman) was calculated based on the averaged SERS signals. A relatively good within-wafer homogeneity of the enhancement effect was found with ISERS/IRaman values as high as 64.2 for Au-coated nano ZnO grown on silicon substrates. The experimental results show that the Au-coated ZnO nanoarrays can be excellent SERS substrates for molecular/chemical analyte sensing.

Thermal stability of supported gold nanoparticles

NASA Astrophysics Data System (ADS)

Turba, Timothy Fredrick

Nanoparticle gold is of interest for a wide array of applications including catalysis, gas sensing, and light absorption for color filters and optical switches. Many of these applications are dependent upon the particles having sizes <5nm. In this paper, the thermal stability of nanoparticle gold is evaluated. Unsupported gold nanoparticles can grow (and in some cases double their size) even at room temperature. An important approach to stabilizing gold nanoparticles is through an interaction with a suitable substrate support material. Semiconductor substrates such as GaN are important supports for gold nanoparticles for applications such as sensors, but GaN does not provide a significant stabilizing effect at high temperatures. This paper covers a number of different substrate materials and in particular shows that for some substrates, such as SiO2, gold nanoparticles can be stable at temperatures up to 500°C, which is significantly above the Tammann temperature for bulk gold (395°C). In this dissertation, gold nanoparticles are shown to have complete stability on aluminum-supported silica nanosprings at 550°C in air. This stability window is one of the highest reported for nanoparticle gold and potentially enables a number of applications for this highly active catalyst. X-ray photoelectron spectroscopy measurements were performed before and after heating to 550°C to determine the nature of the interaction between gold and SiO2. A 1.2 eV drop in gold 4f binding energy after heating signified a shift to anionic gold particles (i.e., Au delta-) indicative of strong bonds to oxygen vacancies with neighboring Sidelta+ atoms. Heating in hydrogen at 550°C resulted in a binding energy decrease of 0.4 eV due to an increased fraction of particles with decreased coordination numbers (i.e., more atoms at edges and corners). Lastly, heating gold nanoparticles in an atmosphere of 10% relative humidity at 550°C resulted in apparent encapsulation of the gold.

Simple and rapid mercury ion selective electrode based on 1-undecanethiol assembled Au substrate and its recognition mechanism.

PubMed

Li, Xian-Qing; Liang, Hai-Qing; Cao, Zhong; Xiao, Qing; Xiao, Zhong-Liang; Song, Liu-Bin; Chen, Dan; Wang, Fu-Liang

2017-03-01

A simple and rapid mercury ion selective electrode based on 1-undecanethiol (1-UDT) assembled Au substrate (Au/1-UDT) has been well constructed. 1-UDT was for the purpose of generating self-assembled monolayer on gold surface to recognize Hg 2+ in aqueous solution, which had a working concentration range of 1.0×10 -8 -1.0×10 -4 molL -1 , with a Nernst response slope of 28.83±0.4mV/-pC, a detection limit of 4.5×10 -9 molL -1 , and a good selectivity over the other tested cations. Also, the Au/1-UDT possessed good reproducibility, stability, and short response time. The recovery obtained for the determination of mercury ion in practical tremella samples was in the range of 99.8-103.4%. Combined electrochemical analysis and X-ray photoelectron spectroscopy (XPS) with quantum chemical computation, the probable recognition mechanism of the electrode for selective recognition of Hg 2+ has been investigated. The covalent bond formed between mercury and sulfur is stronger than the one between gold and sulfur and thus prevents the adsorption of 1-UDT molecules on the gold surface. The quantum chemical computation with density functional theory further demonstrates that the strong interaction between the mercury atom and the sulfur atom on the gold surface leads to the gold sulfur bond ruptured and the gold mercury metallophilic interaction. Copyright © 2016 Elsevier B.V. All rights reserved.

Insights on proximity effect and multiphoton induced luminescence from gold nanospheres in far field optical microscopy

NASA Astrophysics Data System (ADS)

Borglin, Johan; Guldbrand, Stina; Evenbratt, Hanne; Kirejev, Vladimir; Grönbeck, Henrik; Ericson, Marica B.

2015-12-01

Gold nanoparticles can be visualized in far-field multiphoton laser-scanning microscopy (MPM) based on the phenomena of multiphoton induced luminescence (MIL). This is of interest for biomedical applications, e.g., for cancer diagnostics, as MPM allows for working in the near-infrared (NIR) optical window of tissue. It is well known that the aggregation of particles causes a redshift of the plasmon resonance, but its implications for MIL applying far-field MPM should be further exploited. Here, we explore MIL from 10 nm gold nanospheres that are chemically deposited on glass substrates in controlled coverage gradients using MPM operating in NIR range. The substrates enable studies of MIL as a function of inter-particle distance and clustering. It was shown that MIL was only detected from areas on the substrates where the particle spacing was less than one particle diameter, or where the particles have aggregated. The results are interpreted in the context that the underlying physical phenomenon of MIL is a sequential two-photon absorption process, where the first event is driven by the plasmon resonance. It is evident that gold nanospheres in this size range have to be closely spaced or clustered to exhibit detectable MIL using far-field MPM operating in the NIR region.

Insights on proximity effect and multiphoton induced luminescence from gold nanospheres in far field optical microscopy

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

Borglin, Johan; Department of Physics, University of Gothenburg, Kemivägen 10, 412 96 Gothenburg; Guldbrand, Stina

Gold nanoparticles can be visualized in far-field multiphoton laser-scanning microscopy (MPM) based on the phenomena of multiphoton induced luminescence (MIL). This is of interest for biomedical applications, e.g., for cancer diagnostics, as MPM allows for working in the near-infrared (NIR) optical window of tissue. It is well known that the aggregation of particles causes a redshift of the plasmon resonance, but its implications for MIL applying far-field MPM should be further exploited. Here, we explore MIL from 10 nm gold nanospheres that are chemically deposited on glass substrates in controlled coverage gradients using MPM operating in NIR range. The substrates enablemore » studies of MIL as a function of inter-particle distance and clustering. It was shown that MIL was only detected from areas on the substrates where the particle spacing was less than one particle diameter, or where the particles have aggregated. The results are interpreted in the context that the underlying physical phenomenon of MIL is a sequential two-photon absorption process, where the first event is driven by the plasmon resonance. It is evident that gold nanospheres in this size range have to be closely spaced or clustered to exhibit detectable MIL using far-field MPM operating in the NIR region.« less

Plasmonic Library Based on Substrate-Supported Gradiential Plasmonic Arrays

PubMed Central

2014-01-01

We present a versatile approach to produce macroscopic, substrate-supported arrays of plasmonic nanoparticles with well-defined interparticle spacing and a continuous particle size gradient. The arrays thus present a “plasmonic library” of locally noncoupling plasmonic particles of different sizes, which can serve as a platform for future combinatorial screening of size effects. The structures were prepared by substrate assembly of gold-core/poly(N-isopropylacrylamide)-shell particles and subsequent post-modification. Coupling of the localized surface plasmon resonance (LSPR) could be avoided since the polymer shell separates the encapsulated gold cores. To produce a particle array with a broad range of well-defined but laterally distinguishable particle sizes, the substrate was dip-coated in a growth solution, which resulted in an overgrowth of the gold cores controlled by the local exposure time. The kinetics was quantitatively analyzed and found to be diffusion rate controlled, allowing for precise tuning of particle size by adjusting the withdrawal speed. We determined the kinetics of the overgrowth process, investigated the LSPRs along the gradient by UV–vis extinction spectroscopy, and compared the spectroscopic results to the predictions from Mie theory, indicating the absence of local interparticle coupling. We finally discuss potential applications of these substrate-supported plasmonic particle libraries and perspectives toward extending the concept from size to composition variation and screening of plasmonic coupling effects. PMID:25137554

A close-space sublimation driven pathway for the manipulation of substrate-supported micro- and nanostructures

NASA Astrophysics Data System (ADS)

Sundar, Aarthi

The ability to fabricate structures and engineer materials on the nanoscale leads to the development of new devices and the study of exciting phenomena. Nanostructures attached to the surface of a substrate, in a manner that renders them immobile, have numerous potential applications in a diverse number of areas. Substrate-supported nanostructures can be fabricated using numerous modalities; however the easiest and most inexpensive technique to create a large area of randomly distributed particles is by the technique of thermal dewetting. In this process a metastable thin film is deposited at room temperature and heated, causing the film to lower its surface energy by agglomerating into droplet-like nanostructures. The main drawbacks of nanostructure fabrication via this technique are the substantial size distributions realized and the lack of control over nanostructure placement. In this doctoral dissertation, a new pathway for imposing order onto the thermal dewetting process and for manipulating the size, placement, shape and composition of preformed templates is described. It sees the confinement of substrate-supported thin films or nanostructure templates by the free surface of a metal film or a second substrate surface. Confining the templates in this manner and heating them to elevated temperatures leads to changes in the characteristics of the nanostructures formed. Three different modalities are demonstrated which alters the preformed structures by: (i) subtracting atoms from the templates, (ii) adding atoms to the template or (iii) simultaneously adding and subtracting atoms. The ability to carry out such processes depends on the choice of the confining surface and the nanostructured templates used. A subtractive process occurs when an electroformed nickel mesh is placed in conformal contact with a continuous gold film while it dewets, resulting in the formation of a periodic array of gold microstructures on an oxide substrate surface. When heated the gold beneath the grid selectively attaches to it due to the surface energy gradient which drives gold from the low surface energy oxide surface to the higher surface energy nickel mesh. With this process being confined to areas adjacent to and in contact with the grid surface the film ruptures at well-defined locations to form isolated islands of gold and subsequently, a periodic array of microstructures. The process can be carried out on substrates of different crystallographic orientations leading to nanostructures which are formed epitaxially and have orientations based on underlying substrate orientations. The process can be extended by placing a metallic foil of Pt or Ni over preformed templates, in which case a reduction in the size of the initial structures is observed. Placing a foil on structures with random placement and a wide size distribution results, not only in a size reduction, but also a narrowed size distribution. Additive processes are carried out by using materials which possess high vapor pressures much below the sublimation temperature of the template materials. In this case a germanium substrate was used as a source of germanium adatoms while gold or silver nanostructures were used as heterogeneous nucleation sites. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface and, hence, resulting in the formation of heterodimers and hollowed metal nanocrescents upon etching away the Ge. A process which combined aspects of the additive and subtractive process was carried out by using a metallic foil with a high vapor pressure and higher surface energy than the substrate surface (in this case Pd foil). This process resulted in the initial preformed gold templates being annihilated and replaced by nanostructures of palladium, thereby altering their chemical composition. The assembly process relies on the concurrent sublimation of palladium and gold which results in the complete transfer of the templated gold from the substrate to the foil, but not before the templates act as heterogeneous nucleation sites for palladium adatoms arriving to the substrate surface. Thus, the process is not only subtractive, but also additive due to the addition of palladium and removal of gold.

Ultra-high sensitive substrates for surface enhanced Raman scattering, made of 3 nm gold nanoparticles embedded on SiO2 nanospheres

NASA Astrophysics Data System (ADS)

Phatangare, A. B.; Dhole, S. D.; Dahiwale, S. S.; Bhoraskar, V. N.

2018-05-01

The surface properties of substrates made of 3 nm gold nanoparticles embedded on SiO2 nanospheres enabled fingerprint detection of thiabendazole (TBZ), crystal violet (CV) and 4-Aminothiophenol (4-ATP) at an ultralow concentration of ∼10-18 M by surface enhanced Raman spectroscopy (SERS). Gold nanoparticles of an average size of ∼3 nm were synthesized and simultaneously embedded on SiO2 nanospheres by the electron irradiation method. The substrates made from the 3 nm gold nanoparticles embedded on SiO2 nanospheres were successfully used for recording fingerprint SERS spectra of TBZ, CV and 4-ATP over a wide range of concentrations from 10-6 M to 10-18 M using 785 nm laser. The unique features of these substrates are roughness near the surface due to the inherent structural defects of 3 nm gold nanoparticles, nanogaps of ≤ 1 nm between the embedded nanoparticles and their high number. These produced an abundance of nanocavities which act as active centers of hot-spots and provided a high electric field at the reporter molecules and thus an enhancement factor required to record the SERS spectra at ultra low concentration of 10-18 M. The SERS spectra recorded by the substrates of 4 nm and 6 nm gold nanoparticles are discussed.

[Monolithic column-gold composite substrate preparation and application to SERS detection of pigment].

PubMed

Xie, Yun-Fei; Li, Yan; Yu, Hui; Qian, He; Yao, Wei-Rong

2014-03-01

In the present study, we developed a novel SERS substrate with the porous monolith material combined with classic gold nanoparticles, and erythrosine as the research object, by adjusting the different experimental conditions for optimal SERS enhancements, including system pH and mixing time, and ultimately selected the optimum pH value 5.06 and mixing time 25 min. Compared with the traditional gold plastic substrate enhancement effect, the experimental conditions were applied to the monolith substrate SERS detection of dye erythrosine, different concentrations of samples were used for erythrosine SERS detection, and the detection limit reached 0.1 g x mL(-1). The method uses the payload of gold nanoparticles in mesoporous materials to effectively enhance the SERS signal. And this method has the advantages of simpleness and good stability, which provides a favorable theoretical basis for the rapid prohibited colorings screening.

IR visible sum-frequency vibrational spectroscopy of Biphenyl-3 methylene thiol monolayer on gold and silver: effect of the visible wavelength on the SFG spectrum

NASA Astrophysics Data System (ADS)

Humbert, C.; Dreesen, L.; Mani, A. A.; Caudano, Y.; Lemaire, J.-J.; Thiry, P. A.; Peremans, A.

2002-04-01

We measured IR-visible sum-frequency generation spectra of CH 3-(C 6H 4) 2-(CH 2) 3-S-H (Biphenyl-3) self-assembled monolayers on a silver and a gold substrate. For the latter substrate, we observed different interference patterns between the resonant signal of the CH vibration and the non-resonant contribution of the substrate as a function of the visible beam wavelength. The non-linear response of the gold substrate is enhanced around 480 nm corresponding to the s-d interband transition. Such effect is not observed for the silver substrate the interband transition of which is located out of the investigated visible spectral range of 450-700 nm.

Highly sensitive and simple SERS substrate based on photochemically generated carbon nanotubes-gold nanorods hybrids.

PubMed

Caires, A J; Vaz, R P; Fantini, C; Ladeira, L O

2015-10-01

We report a simple and easy formation of hybrids between multi-wall carbon nanotubes and gold nanorods by one-pot in situ photochemical synthesis. Measurements of surface-enhanced Raman scattering (SERS) through the effect "coffee ring" in visible and near infrared (NIR) show high sensitivity with detection of nanomolar concentrations of aromatic dyes. The formation of nanocomposites between carbon nanotubes and gold nanorods without chemical binders simplifies the preparation. Photochemical synthesis is an advance over the techniques previously published. Copyright © 2015 Elsevier Inc. All rights reserved.

Plasmonic properties of gold nanoparticles on silicon substrates: Understanding Fano-like spectra observed in reflection

NASA Astrophysics Data System (ADS)

Bossard-Giannesini, Léo; Cruguel, Hervé; Lacaze, Emmanuelle; Pluchery, Olivier

2016-09-01

Gold nanoparticles (AuNPs) are known for their localized surface plasmon resonance (LSPR) that can be measured with UV-visible spectroscopy. AuNPs are often deposited on silicon substrates for various applications, and the LSPR is measured in reflection. In this case, optical spectra are measured by surface differential reflectance spectroscopy (SDRS) and the absorbance exhibits a negative peak. This article studies both experimentally and theoretically on the single layers of 16 nm diameter spherical gold nanoparticles (AuNPs) grafted on silicon. The morphology and surface density of AuNPs were investigated by atomic force microscopy (AFM). The plasmon response in transmission on the glass substrate and in reflection on the silicon substrate is described by an analytical model based on the Fresnel equations and the Maxwell-Garnett effective medium theory (FMG). The FMG model shows a strong dependence to the incidence angle of the light. At low incident angles, the peak appears negatively with a shallow intensity, and at angles above 30°, the usual positive shape of the plasmon is retrieved. The relevance of the FMG model is compared to the Mie theory within the dipolar approximation. We conclude that no Fano effect is responsible for this derivative shape. An easy-to-use formula is derived that agrees with our experimental data.

Straight single-crystalline germanium nanowires and their patterns grown on sol gel prepared gold/silica substrates

NASA Astrophysics Data System (ADS)

Pan, Zheng Wei; Dai, Sheng; Lowndes, Douglas H.

2005-04-01

Straight single-crystalline Ge nanowires with a uniform diameter distribution of 50-80 nm and lengths up to tens of micrometers were grown in a high yield on sol-gel prepared gold/silica substrates by using Ge powder as the Ge source. Detailed electron microscopy analyses show that the nanowires grow through a vapor-liquid-solid growth mechanism with gold nanoparticles located at the nanowire tips. By using transmission electron microscope grids as the shadow mask, the sol-gel technique can be readily adapted to prepare patterned film-like gold/silica substrates, so that regular micropatterns of Ge nanowires were obtained, which could facilitate the integration of Ge nanowires for characterization and devices.

SPM Investigation of Thiolated Gold Nanoparticle Patterns Deposited on Different Self-Assembled Substrates

NASA Astrophysics Data System (ADS)

Sbrana, F.; Parodi, M. T.; Ricci, D.; Di Zitti, E.

We present the results of a Scanning Probe Microscopy (SPM) investigation of ordered nanosized metallo-organic structures. Our aim is to investigate the organization and stability of thiolated gold nanoparticles in a compact pattern when deposited onto gold substrates functionalized with self-assembled monolayers made from two molecules that differ essentially in their terminating group: 1,4-benzenedimethanethiol and 4-methylbenzylthiol.

SERS as analytical tool for detection of bacteria

NASA Astrophysics Data System (ADS)

Cialla, Dana; Rösch, Petra; Möller, Robert; Popp, Jürgen

2007-07-01

The detection of single bacteria should be improved by lowering the acquisition time via the application of SERS (surface enhanced Raman spectroscopy). Nano structured colloids or surfaces consisting of gold or silver can be used as SERS active substrates. However, for biological applications mostly gold is used as SERS active substrate since silver is toxic for bacterial cells. Furthermore, the application of gold as a SERS-active substrate allows the usage of Raman excitation wavelengths in the red part of the electromagnetic spectrum. For the SERS investigations on bacteria different colloids (purchased and self prepared, preaggregated and non-aggregated) are chosen as SERS active substrates. The application of different gold colloids under gently mixing conditions to prevent the bacterial damage allowed the recording of reproducible SERS spectra of bacteria. The SERS spectra of B. pumilus are dominated by contributions of ingredients of the outer cell wall, e.g. the peptidoglycan layer. SEM images of the coated bacteria demonstrate the incomplete adsorption most probably due to variations within the binding affinities between different outer cell components and the gold colloids.

Friction and hardness of gold films deposited by ion plating and evaporation

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1983-01-01

Sliding friction experiments were conducted with ion-plated and vapor-deposited gold films on various substrates in contact with a 0.025-mm-radius spherical silicon carbide rider in mineral oil. Hardness measurements were also made to examine the hardness depth profile of the coated gold on the substrate. The results indicate that the hardness is influenced by the depth of the gold coating from the surface. The hardness increases with an increase in the depth. The hardness is also related to the composition gradient in the graded interface between the gold coating and the substrate. The graded interface exhibited the highest hardness resulting from an alloy hardening effect. The coefficient of friction is inversely related to the hardness, namely, the load carrying capacity of the surface. The greater the hardness that the metal surface possesses, the lower is the coefficient of friction. The graded interface exhibited the lowest coefficient of friction.

Fabrication of novel compound SERS substrates composed of silver nanoparticles and porous gold nanoclusters: A study on enrichment detection of urea

NASA Astrophysics Data System (ADS)

Li, Yali; Li, Qianwen; Sun, Chengbin; Jin, Sila; Park, Yeonju; Zhou, Tieli; Wang, Xu; Zhao, Bing; Ruan, Weidong; Jung, Young Mee

2018-01-01

A new type of surface-enhanced Raman scattering (SERS) substrate was fabricated through the layer-by-layer self-assembly of silver nanoparticles (AgNPs, av. 45 nm in diameter) and porous gold nanoclusters/nanoparticles (AuNPs, av. 143 nm in diameter). The development of the porosity of the AuNPs was investigated, and successful SERS applications of the porous AuNPs were also examined. As compared with AgNP films, the enhancement factor of Ag-Au compound substrates is increased 6 times at the concentration of 10-6 M. This additional enhancement contributes to the trace-amount-detection of target molecules enormously. The contribution is generated through the increase of the usable surface area arising from the nanoscale pores distributed three-dimensionally in the porous AuNPs, which enrich the adsorption sites and hot spots for the adsorption of probe molecules, making the developed nanofilms highly sensitive SERS substrates. The substrates were used for the detection of a physiological metabolite of urea molecules. The results reached to a very low concentration of 1 mM and exhibited good quantitative character over the physiological concentration range (1 ∼ 20 mM) under mimicking biophysical conditions. These results show that the prepared substrate has great potential in the ultrasensitive SERS-based detection and in SERS-based biosensors.

Control of spectral transmission enhancement properties of random anti-reflecting surface structures fabricated using gold masking

NASA Astrophysics Data System (ADS)

Peltier, Abigail; Sapkota, Gopal; Potter, Matthew; Busse, Lynda E.; Frantz, Jesse A.; Shaw, L. Brandon; Sanghera, Jasbinder S.; Aggarwal, Ishwar D.; Poutous, Menelaos K.

2017-02-01

Random anti-reflecting subwavelength surface structures (rARSS) have been shown to suppress Fresnel reflection and scatter from optical surfaces. The structures effectively function as a gradient-refractive-index at the substrate boundary, and the spectral transmission properties of the boundary have been shown to depend on the structure's statistical properties (diameter, height, and density.) We fabricated rARSS on fused silica substrates using gold masking. A thin layer of gold was deposited on the surface of the substrate and then subjected to a rapid thermal annealing (RTA) process at various temperatures. This RTA process resulted in the formation of gold "islands" on the surface of the substrate, which then acted as a mask while the substrate was dry etched in a reactive ion etching (RIE) process. The plasma etch yielded a fused silica surface covered with randomly arranged "rods" that act as the anti-reflective layer. We present data relating the physical characteristics of the gold "island" statistical populations, and the resulting rARSS "rod" population, as well as, optical scattering losses and spectral transmission properties of the final surfaces. We focus on comparing results between samples processed at different RTA temperatures, as well as samples fabricated without undergoing RTA, to relate fabrication process statistics to transmission enhancement values.

The nanocoherer: an electrically and mechanically resettable resistive switching device based on gold clusters assembled on paper

NASA Astrophysics Data System (ADS)

Minnai, Chloé; Mirigliano, Matteo; Brown, Simon A.; Milani, Paolo

2018-03-01

We report the realization of a resettable resistive switching device based on a nanostructured film fabricated by supersonic cluster beam deposition of gold clusters on plain paper substrates. Through the application of suitable voltage ramps, we obtain, in the same device, either a complex pattern of resistive switchings, or reproducible and stable switchings between low resistance and high resistance states, with an amplitude up to five orders of magnitude. Our device retains a state of internal resistance following the history of the applied voltage similar to that reported for memristors. The two different switching regimes in the same device are both stable, the transition between them is reversible, and it can be controlled by applying voltage ramps or by mechanical deformation of the substrate. The device behavior can be related to the formation, growth and breaking of junctions between the loosely aggregated gold clusters forming the nanostructured films. The fact that our cluster-assembled device is mechanically resettable suggests that it can be considered as the analog of the coherer: a switching device based on metallic powders used for the first radio communication system.

Surface Optical Property Measurements on Bark and Leaf Samples

DTIC Science & Technology

1990-12-31

individually positionable in sample measurement position. 100% Value Absolute, or in comparison to high-reflectance evaporated gold reference sample...evaporated gold on a smooth fused silica substrate. The absolute 100% measurement requires removing the sample from the measurement position and...choice is evaporated gold on a polished glass substrate. As- already noted, SOC uses two instruments to cover the full spectral region from 0.2 to 40.0

Fabrication of Gold-Coated Ultra-Thin Anodic Porous Alumina Substrates for Augmented SERS

PubMed Central

Toccafondi, Chiara; Proietti Zaccaria, Remo; Dante, Silvia; Salerno, Marco

2016-01-01

Anodic porous alumina (APA) is a nanostructured material used as a template in several nanotechnological applications. We propose the use of APA in ultra-thin form (<100 nm) for augmented surface-enhanced Raman scattering (SERS). Here, the effect of in-depth thinning of the APA nanostructures for possible maximization of SERS was addressed. Anodization was carried out on ultra-thin films of aluminum on glass and/or silicon, followed by pore-opening. Gold (Au) was overcoated and micro-Raman/SERS measurements were carried out on test target analytes. Finite integration technique simulations of the APA-Au substrate were used both for the experimental design and simulations. It was observed that, under optimized conditions of APA and Au thickness, the SERS enhancement is higher than on standard APA-Au substrates based on thin (~100 nm) APA by up to a factor of ~20 for test molecules of mercaptobenzoic acid. The agreement between model and experimental results confirms the current understanding of SERS as being mainly due to the physical origin of plasmon resonances. The reported results represent one step towards micro-technological, integrated, disposable, high-sensitivity SERS chemical sensors and biosensors based on similar substrates. PMID:28773525

Efficient Surface Enhanced Raman Scattering substrates from femtosecond laser based fabrication

NASA Astrophysics Data System (ADS)

Parmar, Vinod; Kanaujia, Pawan K.; Bommali, Ravi Kumar; Vijaya Prakash, G.

2017-10-01

A fast and simple femtosecond laser based methodology for efficient Surface Enhanced Raman Scattering (SERS) substrate fabrication has been proposed. Both nano scaffold silicon (black silicon) and gold nanoparticles (Au-NP) are fabricated by femtosecond laser based technique for mass production. Nano rough silicon scaffold enables large electromagnetic fields for the localized surface plasmons from decorated metallic nanoparticles. Thus giant enhancement (approximately in the order of 104) of Raman signal arises from the mixed effects of electron-photon-phonon coupling, even at nanomolar concentrations of test organic species (Rhodamine 6G). Proposed process demonstrates the low-cost and label-less application ability from these large-area SERS substrates.

Substrate Dependence in the Growth of Three-Dimensional Gold Nanoparticle Superlattices

DTIC Science & Technology

2001-11-01

the Hamaker constants between gold nanoparticle assemblies and substrates through the suspension. Van der Waals interactions estimated from this...finally dialyzed to remove inorganic (Na, Cl, and B) and organic impurities. The surfactant affects the dispersion of Au nanoparticles in aqueous...be taken into account for complete understanding of the observed substrate dependency. To consider volume interactions, we calculate the Hamaker

Tellurium nano-structure based NO gas sensor.

PubMed

Kumar, Vivek; Sen, Shashwati; Sharma, M; Muthe, K P; Jagannath; Gaur, N K; Gupta, S K

2009-09-01

Tellurium nanotubes were grown on bare and silver/gold nanoparticle (nucleation centers) deposited silicon substrates by vacuum deposition technique at a substrate temperature of 100 degrees C under high vacuum conditions. Silver and gold nanoparticles prepared on (111) oriented silicon substrates were found to act as nucleation centers for growth of Tellurium nanostructures. Density of nanotubes was found to increase while their diameter reduced when grown using metallic nanoparticle template. These Te nanostructures were investigated for their gas sensitivity. Tellurium nanotubes on Ag templates showed better response to NO in comparison to H2S and NH3 gases. Selectivity in response to NO was improved in comparison to Te thin film sensors reported earlier. The gas sensing mechanism was investigated using Raman and X-ray photoelectron spectroscopy techniques. The interaction of NO is seen to yield increased adsorption of oxygen that in turn increases hole density and conductivity in the material.

A high-performance and low cost SERS substrate of plasmonic nanopillars on plastic film fabricated by nanoimprint lithography with AAO template

NASA Astrophysics Data System (ADS)

Liu, Long; Zhang, Qian; Lu, Yuanshen; Du, Wei; Li, Bin; Cui, Yushuang; Yuan, Changsheng; Zhan, Peng; Ge, Haixiong; Wang, Zhenling; Chen, Yanfeng

2017-06-01

As a powerful spectroscopy technique, surface-enhanced Raman scattering (SERS) can provide non-destructive and sensitive characterization down to a single molecular level. Aiming to the main challenges of high-performance SERS-active substrates for their real-world applications involving the ultra-sensitive and reproducible signals detection and signal uniformity with large-area, herein, a facile and reliable strategy based on combination of thermal imprinting polycarbonate (PC) film with porous anodic aluminum oxide (AAO) mold and E-beam evaporation of gold is provided to fabricate a high-quality SERS-active substrate consisting of ultra-dense hot-spots with large-area uniformity. Two kinds of sub-10 nm gaps were obtained, including the nanogaps between the neighboring gold coated PC-nanopillars and those between gold on the top of the nanopillars and that on the base, which actually build up a three-dimensional (3D) hot-spot network for high-performance SERS detection. The effect of structural parameters on SERS enhancement was investigated numerically and experimentally, and by optimizing the structural parameters, a remarkable average SERS enhancement factor up to of 1.4×108 is achieved and it shows an excellent reproducibility with a relative standard deviation of 18%, which allows for enhanced practicability in the application of quantitative biochemical detection.

Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

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

Wong, Sze-Shun Season

1999-12-10

This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end group orientation of monolayer chemisorbed at smooth gold surfaces with micrometer resolution (Chapter 4). The ability to detect the differences in the orientational dispositionmore » is demonstrated by the use PDMS polymer stamp to microcontact print an adlayer of n-alkanethiolate of length n in a predefine pattern onto a gold surface, followed by the solution deposition of a n-alkanethiol of n ± 1 to fill in the areas on the gold surface intentionally not coated by the stamping process. These two-component monolayers can be discriminated by using friction force microscopy which detects differences in friction contributed by the differences in the orientation of the terminal groups at surfaces. This success has recently led to the detection of the orientation differences at nanometer scale. Although the substrates examined in this work consisted entirely of smooth gold films, the same test can be performed on other smooth substrates and monolayer materials.« less

Optimized organic photovoltaics with surface plasmons

NASA Astrophysics Data System (ADS)

Omrane, B.; Landrock, C.; Aristizabal, J.; Patel, J. N.; Chuo, Y.; Kaminska, B.

2010-06-01

In this work, a new approach for optimizing organic photovoltaics using nanostructure arrays exhibiting surface plasmons is presented. Periodic nanohole arrays were fabricated on gold- and silver-coated flexible substrates, and were thereafter used as light transmitting anodes for solar cells. Transmission measurements on the plasmonic thin film made of gold and silver revealed enhanced transmission at specific wavelengths matching those of the photoactive polymer layer. Compared to the indium tin oxide-based photovoltaic cells, the plasmonic solar cells showed overall improvements in efficiency up to 4.8-fold for gold and 5.1-fold for the silver, respectively.

Cell viability monitoring using Fano resonance in gold nanoslit array

NASA Astrophysics Data System (ADS)

Wu, Shu-Han; Hsieh, Shu-Yi; Lee, Kuang-Li; Weng, Ruei-Hung; Chiou, Arthur; Wei, Pei-Kuen

2013-09-01

Cell viability is a crucial issue in biological research. We present label-free monitoring of adhesion cells viability by gold nanoslits-based Fano resonance biosensors. Plastic multiple wells with gold nanoslits substrate were made using a thermal nanoimprint method. Adhesion cells in the wells were treated with doxorubicin for inducing cell death and compared with conventional colorimetric assay. The nanoslits method shows better respones of viability tests under low concentration and short interaction time due to its high surface sensitivies. The vinculin labelling indicates that the measured signals are in good agreement with the adhesion abilities of cells.

Functionalization of nanostructured gold substrates with chiral chromophores for SERS applications: The case of 5-Aza[5]helicene.

PubMed

Zanchi, Chiara; Lucotti, Andrea; Cancogni, Damiano; Fontana, Francesca; Trusso, Sebastiano; Ossi, Paolo M; Tommasini, Matteo

2018-05-31

Nanostructured gold thin films can be fabricated by controlled pulsed laser deposition to get efficient sensors, with uniform morphology and optimized plasmon resonance, to be employed as plasmonic substrates in surface enhanced Raman scattering spectroscopy. By attaching 5-aza[5]helicen-6-yl-6-hexanethiol to such gold nanostructures, used in a previous work for label-free drug sensing with biomedical purposes, we successfully prepared functionalized substrates with remarkable surface enhanced Raman scattering activity. The long-term motivation is to develop probes for drug detection at low concentrations, where sensitivity to specific chiral targets is required. © 2018 Wiley Periodicals, Inc.

Elevated gold ellipse nanoantenna dimers as sensitive and tunable surface enhanced Raman spectroscopy substrates

DOE PAGES

Jubb, A. M.; Jiao, Y.; Eres, Gyula; ...

2016-02-15

Here we demonstrate large area arrays of elevated gold ellipse dimers with precisely controlled gaps for use as sensitive and highly controllable surface enhanced Raman scattering (SERS) substrates. The significantly enhanced Raman signal observed with SERS arises from both localized and long range plasmonic effects. By controlling the geometry of a SERS substrate, in this case the size and aspect ratio of individual ellipses, the plasmon resonance can be tuned in a broad wavelength range, providing a method for designing the response of SERS substrates at different excitation wavelengths. Plasmon effects exhibited by the elevated gold ellipse dimer substrates aremore » also demonstrated and confirmed through finite difference time domain (FDTD) simulations. A plasmon resonance red shift with an increase of the ellipse aspect ratio is observed, allowing systematic control of the resulting SERS signal intensity. Optimized elevated ellipse dimer substrates with 10±2 nm gaps exhibit uniform SERS enhancement factors on the order of 10 9 for adsorbed p-mercaptoaniline molecules.« less

Bio-sensing with butterfly wings: naturally occurring nano-structures for SERS-based malaria parasite detection.

PubMed

Garrett, Natalie L; Sekine, Ryo; Dixon, Matthew W A; Tilley, Leann; Bambery, Keith R; Wood, Bayden R

2015-09-07

Surface enhanced Raman scattering (SERS) is a powerful tool with great potential to provide improved bio-sensing capabilities. The current 'gold-standard' method for diagnosis of malaria involves visual inspection of blood smears using light microscopy, which is time consuming and can prevent early diagnosis of the disease. We present a novel surface-enhanced Raman spectroscopy substrate based on gold-coated butterfly wings, which enabled detection of malarial hemozoin pigment within lysed blood samples containing 0.005% and 0.0005% infected red blood cells.

Ion plated gold films: Properties, tribological behavior and performance

NASA Technical Reports Server (NTRS)

Spalvins, Talivaldis

1987-01-01

The glow discharge energizing favorably modifies and controls the coating/substrate adherence and the nucleation and growth sequence of ion plated gold films. As a result the adherence, coherence, internal stresses, and morphology of the films are significantly improved. Gold ion plated films because of their graded coating/substrate interface and fine uniform densely packed microstructure not only improve the tribological properties but also induce a surface strengthening effect which improves the mechanical properties such as yield, tensile, and fatigue strength. Consequently significant improvements in the tribological performance of ion plated gold films as compared to vapor deposited gold films are shown in terms of decreased friction/wear and prolonged endurance life.

Nanomolar detection of glucose using SERS substrates fabricated with albumin coated gold nanoparticles

NASA Astrophysics Data System (ADS)

Perez-Mayen, Leonardo; Oliva, Jorge; Salas, P.; de La Rosa, Elder

2016-06-01

This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles synthesized by a wet chemical method. The SERS substrates were used for glucose detection for concentrations as low as 10-7 M, which represents an enhancement factor (EF) of 109, as a result of the hot spot formed by the spike termination and appropriate distribution of the gold nanoparticles. An improvement of two orders of magnitude was obtained by coating the gold nanoparticles with albumin with the configuration: glass/Au nanoparticles/albumin. In this case the lowest detection was at a concentration of 10-9 M for an EF of 1011. The albumin molecule allowed us to enhance the Raman signal because of the formation of peptide bonds (COOH-NH2) generated due to the interaction of glucose with albumin, and the appropriate separation distance between the glucose molecules and gold nanoparticles. The presence of such peptide conjugates was confirmed by FTIR spectra. Thus, our results suggest that our SERS substrates can be useful for the detection of very low concentrations of glucose, which is important for the diagnosis of diabetes in the field of medicine.This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles synthesized by a wet chemical method. The SERS substrates were used for glucose detection for concentrations as low as 10-7 M, which represents an enhancement factor (EF) of 109, as a result of the hot spot formed by the spike termination and appropriate distribution of the gold nanoparticles. An improvement of two orders of magnitude was obtained by coating the gold nanoparticles with albumin with the configuration: glass/Au nanoparticles/albumin. In this case the lowest detection was at a concentration of 10-9 M for an EF of 1011. The albumin molecule allowed us to enhance the Raman signal because of the formation of peptide bonds (COOH-NH2) generated due to the interaction of glucose with albumin, and the appropriate separation distance between the glucose molecules and gold nanoparticles. The presence of such peptide conjugates was confirmed by FTIR spectra. Thus, our results suggest that our SERS substrates can be useful for the detection of very low concentrations of glucose, which is important for the diagnosis of diabetes in the field of medicine. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00163g

Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

NASA Astrophysics Data System (ADS)

Zheng, Zhikun; Yang, Menglong; Liu, Yaqing; Zhang, Bailin

2006-11-01

Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip.

Split of surface plasmon resonance of gold nanoparticles on silicon substrate: a study of dielectric functions.

PubMed

Zhu, S; Chen, T P; Cen, Z H; Goh, E S M; Yu, S F; Liu, Y C; Liu, Y

2010-10-11

The split of surface plasmon resonance of self-assembled gold nanoparticles on Si substrate is observed from the dielectric functions of the nanoparticles. The split plasmon resonances are modeled with two Lorentz oscillators: one oscillator at ~1 eV models the polarization parallel to the substrate while the other at ~2 eV represents the polarization perpendicular to the substrate. Both parallel and perpendicular resonances are red-shifted when the nanoparticle size increases. The red shifts in both resonances are explained by the image charge effect of the Si substrate.

Extreme ultraviolet reflectivity studies of gold on glass and metal substrates

NASA Technical Reports Server (NTRS)

Jelinsky, Sharon R.; Malina, Roger F.; Jelinsky, Patrick

1988-01-01

The paper reports measurements of the extreme ultraviolet reflectivity of gold from 44 to 920 A at grazing incidence. Gold was deposited using vacuum evaporation and electroplating on substrates of glass and polished nickel, respectively. Measurements are also presented of the extreme ultraviolet reflectivity of electroless nickel in the same wavelength region, where one of the polished nickel substrates was used as a sample. Derived optical constants for evaporated and electroplated gold and electroless nickel are presented. Additional studies of the effects of various contaminants on the EUV reflectivity are also reported. The variations of the optical constants are discussed in terms of density variations, surface roughness and contamination effects. These results ae reported as part of studies for the Extreme Ultraviolet Explorer satellite program to determine acceptance criteria for the EUV optics, contamination budgets and calibration plans.

Gold nanochestnut arrays as ultra-sensitive SERS substrate for detecting trace pesticide residue.

PubMed

Geng, Fei; Zhao, Huaping; Fu, Qun; Mi, Yan; Miao, Likun; Li, Wei; Dong, Yulian; Wu, Minghong; Lei, Yong

2018-07-20

In comparison to conventional spectroscopic techniques based on chromatography, surface-enhanced Raman spectroscopy (SERS) enables the rapid identification and detection of trace pesticide residues present in trace amounts in the environment and foods. Herein, a facile approach to fabricate unique gold nanochestnuts (GNCs) as an ultra-sensitive SERS substrate for detecting trace pesticide residues has been developed based on anodic aluminum oxide (AAO) templates. The GNCs are synthesized through the galvanic replacement of Ag on the top of Ni nanorod arrays. The as-prepared GNCs have well-controlled structural parameters, and importantly have unique anisotropic morphologies that benefit the enhancement in SERS performance. As a result, rhodamine 6 G (R6G) can be efficiently detected with GNCs as the SERS substrate even with a concentration of only 10 -12 M, and the Raman enhancement factor reaches up to 5.4 × 10 9 at this concentration. Further SERS measurement of thiram indicates a remarkable SERS-active sensitivity of the as-prepared GNCs with a detection limit of thiram up to 10 -14 M. The GNCs also exhibit a high signal-to-noise ratio.

Thin Film Solid Lubricant Development

NASA Technical Reports Server (NTRS)

Benoy, Patricia A.

1997-01-01

Tribological coatings for high temperature sliding applications are addressed. A sputter-deposited bilayer coating of gold and chromium is investigated as a potential solid lubricant for protection of alumina substrates during sliding at high temperature. Evaluation of the tribological properties of alumina pins sliding against thin sputtered gold films on alumina substrates is presented.

Plasmonic improvement of microcavity biomedical sensor spectroscopic characteristics

NASA Astrophysics Data System (ADS)

Saetchnikov, Vladimir A.; Tcherniavskaia, Elina A.; Saetchnikov, Anton V.; Schweiger, Gustav; Ostendorf, Andreas; Ghadiri, Reza

2014-03-01

New opportunity to improve a sensetivity of a label-free biomolecule detection in sensing systems based on microcavity evanescent wave optical sensors has been recently found and is being under intensive development. Novel technique based on combination of optical resonance on microring structures with plasmon resonance. Recently developed tools based on neural network data processing can realize real-time identification of biological agents. So combining advantages of plasmon enhancing optical microcavity resonance with identification tools can give a new platform for ulta sensitive label-free biomedical sensor. Our developed technique used standard glass and polymer microspheres as sensetive elements. They are fixed in the solution flow by adhesive layer on the surface being in the field of evanescence wave. Sensitive layer have been treated by gold nanoparticel (GN) solution. Another technique used thin film gold layers deposited on the substrate below adhesive. The light from a tuneable diode laser is coupled into the microsphere through a prism and was sharply focussed on the single microsphere. Images were recorded by CMOS camera. Normalized by free spectral range resonance shift of whispering gallery mode (WGM) and a relative efficiency of their excitation were used as input data for biomolecule classification. Both biomolecules and NP injection was obtained caused WGM spectra modification. But after NP treatment spectral shift and intensity of WGM resonances in biomolecule solutions increased. WGM resonances in microspheres fixed on substrate with gold layer with optimized layer thickness in biomolecule solutions also had higher intensity and spectra modification then without gold layer.

Paper-based SERS swab for rapid trace detection on real-world surfaces.

PubMed

Lee, Chang H; Tian, Limei; Singamaneni, Srikanth

2010-12-01

One of the important but often overlooked considerations in the design of surface-enhanced Raman scattering (SERS) substrates for trace detection is the efficiency of sample collection. Conventional designs based on rigid substrates such as silicon, alumina, and glass resist conformal contact with the surface under investigation, making the sample collection inefficient. We demonstrate a novel SERS substrate based on common filter paper adsorbed with gold nanorods, which allows conformal contact with real-world surfaces, thus dramatically enhancing the sample collection efficiency compared to conventional rigid substrates. We demonstrate the detection of trace amounts of analyte (140 pg spread over 4 cm2) by simply swabbing the surface under investigation with the novel SERS substrate. The hierarchical fibrous structure of paper serves as a 3D vasculature for easy uptake and transport of the analytes to the electromagnetic hot spots in the paper. Simple yet highly efficient and cost-effective SERS substrate demonstrated here brings SERS-based trace detection closer to real-world applications.

A facile and cost-effective TEM grid approach to design gold nano-structured substrates for high throughput plasmonic sensitive detection of biomolecules.

PubMed

Jia, Kun; Bijeon, Jean Louis; Adam, Pierre Michel; Ionescu, Rodica Elena

2013-02-21

A commercial TEM grid was used as a mask for the creation of extremely well-organized gold micro-/nano-structures on a glass substrate via a high temperature annealing process at 500 °C. The structured substrate was (bio)functionalized and used for the high throughput LSPR immunosensing of different concentrations of a model protein named bovine serum albumin.

A highly sensitive biological detection substrate based on TiO2 nanowires supporting gold nanoparticles

NASA Astrophysics Data System (ADS)

Zeng, Yuan; Tan, Hai-jun; Cheng, Xiu-Lan; Chen, Rui; Wang, Ying

2011-12-01

Surface enhanced Raman scattering (SERS) has attracted widespread concern in the field of bioassay because it can enhance normally weak Raman signal by several orders of magnitude and facilitate the highly sensitive detection of molecules. Conventional SERS substrates are prepared by placing metal nanoparticles on a planar surface. Here we show a unique SERS substrate stacked by disordered TiO2 nanowires (TiO2-NWs) supportig gold nanocrystals. The structure can be easily fabricated by chemical synthesis at low cost. The COMSOL model simulation shows the designed SERS substrate is capable of output high Local Field Enhancement (LFE) in the Near Infrared region (NIR) that is the optimal wavelength in bio-detection because of both the unique coupling enhancement effect amony nearby Au nanocrystals on TiO2-NWs and the Suface Plasmon Resonance (SPR) effect of TiO2 -NWs. The as-prepared transparent and freestanding SERS substrate is capable of detecting extremely low concentration R6G molecular, showing much higher Raman signal because of the extremely large surface area and the uniqueTiO2-NWs self-assemblied by Au nanocrystals. These results provide a new approach to ultrasensitive bioassay device.

Patterning of oxide-hardened gold black by photolithography and metal lift-off

NASA Astrophysics Data System (ADS)

Panjwani, Deep; Yesiltas, Mehmet; Nath, Janardan; Maukonen, D. E.; Rezadad, Imen; Smith, Evan M.; Peale, R. E.; Hirschmugl, Carol; Sedlmair, Julia; Wehlitz, Ralf; Unger, Miriam; Boreman, Glenn

2014-01-01

A method to pattern infrared-absorbing gold black by conventional photolithography and lift-off is described. A photo-resist pattern is developed on a substrate by standard photolithography. Gold black is deposited over the whole by thermal evaporation in an inert gas at ˜1 Torr. SiO2 is then deposited as a protection layer by electron beam evaporation. Lift-off proceeds by dissolving the photoresist in acetone. The resulting sub-millimeter size gold black patterns that remain on the substrate retain high infrared absorption out to ˜5 μm wavelength and exhibit good mechanical stability. This technique allows selective application of gold black coatings to the pixels of thermal infrared imaging array detectors.

Gold sputtered Blu-Ray disks as novel and cost effective sensors for surface enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Nieuwoudt, Michél. K.; Martin, Jacob W.; Oosterbeek, Reece N.; Novikova, Nina I.; Wang, Xindi; Malmström, Jenny; Williams, David E.; Simpson, M. C.

2015-03-01

Surface Enhanced Raman spectroscopy (SERS) offers sensitive and non-invasive detection of a variety of compounds as well as unparalleled information for establishing the molecular identity of both inorganic and organic compounds, not only in biological fluids but in all other aqueous and non-aqueous media. The localized hotspots produced through SERS at the solution/nanostructure interface of clustered gold or silver nano-particles enables detection levels of parts per trillion. Recent developments in advanced fabrication methods have enabled the manufacture of SERS substrates with repeatable surface nanostructures which provide reproducible quantitative analysis, historically a weakness of the SERS technique. In this paper we describe the novel use of gold sputtered Blu-Ray surfaces as SERS substrates. Blu-Ray disks provide ideal surfaces of SERS substrates with their repeatable and regular nano-gratings. We show that the unique surface features and composition of the recording surface enables the formation of gold nano-islands with nanogaps, simply through gold sputtering, and relate this to a 600 fold signal increase of the melamine Raman signal in aqueous solutions and detection to 68 ppb. Melamine is a triazine compound and appears not only as environmental contaminant in environmental groundwater but also as an adulterant in foods due to its high nitrogen content. We have shown significant SERS signal enhancements for spectra of melamine using gold-sputtered Blu-Ray disk surfaces, with reproducibility of 12%. Blu-Ray disks have a unique combination of design, surface features and composition of the recording surface which makes them ideal for preparation of SERS substrates by gold sputter-coating.

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.

The X-ray photoelectron spectroscopy depth profiling and tribological characterization of ion-plated gold on various metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1983-01-01

For the case of ion-plated gold, the graded interface between gold and a nickel substrate and a nickel substrate, such tribological properties as friction and microhardness are examined by means of X-ray photoelectron spectroscopy analysis and depth profiling. Sliding was conducted against SiC pins in both the adhesive process, where friction arises from adhesion between sliding surfaces, and abrasion, in which friction is due to pin indentation and groove-plowing. Both types of friction are influenced by coating depth, but with opposite trends: the graded interface exhibited the highest adhesion, but the lowest abrasion. The coefficient of friction due to abrasion is inversely related to hardness. Graded interface microhardness values are found to be the highest, due to an alloying effect. There is almost no interface gradation between the vapor-deposited gold film and the substrate.

Designing of a novel gold nanodumbbells SERS substrate for detection of prohibited colorants in drinks

NASA Astrophysics Data System (ADS)

Meng, Juan; Qin, Suhua; Zhang, Li; Yang, Liangbao

2016-03-01

It is reported that the use of gold nanodumbbells as surface-enhanced Raman spectroscopy (SERS) substrates for the detection of ultra-low levels of four different food colorants: sunset yellow, lemon yellow, orange II and chrysoidin. Gold nanodumbbells are suitable to on-site detection because which have a λmax of 785 nm that tune the surface plasmon resonance of the nanoparticles to the laser excitation wavelength of the Raman spectrometer equipped with a 785 nm diode laser. In order to investigate the on-site application of the gold nanodumbbells substrate, four pigments in the orange juice and coke were detected by the portable Raman instrument. The results showed that this novel SERS platform can be used as an effective method in detecting prohibited additive colorants in food. This SERS platform provides valuable and powerful analytical tool in real-world applications in food analysis.

LUSH-based SPR sensor for the detection of alcohols and pheromone

NASA Astrophysics Data System (ADS)

Lau, Hui-Chong; Lee, Yeon-Kyung; Kwon, Jae-Young; Sohn, Young-Soo; Lim, Jeong Ok

2013-05-01

Protein is a widely used sensing substrate in the biosensing technology. In the study conducted here, we used odorant binding protein, LUSH from Drosophila as a biosensing substrate in a miniaturized surface plasmon resonance (SPR) sensor. LUSH contains the specific alcohols binding sites, which mediates the detection of alcohols and pheromone. We first modified the surface of the gold sensor chip using the self assembled monolayer in the chloroform solution. The saturated concentration was determined prior to the detection of alcohols and pheromone at various concentrations. The results showed that the LUSH was saturated at 1000 μg/ml on the gold sensor chip. The detection response of LUSH was significant at higher concentration of alcohols. LUSH detected ethanol at concentration >=50% propanol was detected at >=25% whereas pheromone was detected at >=1.25 μg/μl. The results provide some fundamental information on the potential use of LUSH-based SPR as a simple and easy protein-based sensor in the near future.

Plasmonic crystal based solid substrate for biomedical application of SERS

NASA Astrophysics Data System (ADS)

Morasso, Carlo F.; Mehn, Dora; Picciolini, Silvia; Vanna, Renzo; Bedoni, Marzia; Gramatica, Furio; Pellacani, Paola; Frangolho, Ana; Marchesini, Gerardo; Valsesia, Andrea

2014-02-01

Surface Enhanced Raman Spectroscopy is a powerful analytical technique that combines the excellent chemical specificity of Raman spectroscopy with the good sensitivity provided by the enhancement of the signal observed when a molecule is located on (or very close to) the surface of suitable nanostructured metallic materials. The availability of cheap, reliable and easy to use SERS substrates would pave the road to the development of bioanalytical tests that can be used in clinical practice. SERS, in fact, is expected to provide not only higher sensitivity and specificity, but also the simultaneous and markedly improved detection of several targets at the same time with higher speed compared to the conventional analytical methods. Here, we present the SERS activity of 2-D plasmonic crystals made by polymeric pillars embedded in a gold matrix obtained through the combination of soft-lithography and plasma deposition techniques on a transparent substrates. The use of a transparent support material allowed us to perform SERS detection from support side opening the possibility to use these substrates in combination with microfluidic devices. In order to demonstrate the potentialities for bioanalytical applications, we used our SERS active gold surface to detect the oxidation product of apomorphine, a well-known drug molecule used in Parkinson's disease which has been demonstrated being difficult to study by traditional HPLC based approaches.

A sensitive plasmonic copper(II) sensor based on gold nanoparticles deposited on ITO glass substrate.

PubMed

Ding, Lijun; Gao, Yan; Di, Junwei

2016-09-15

Gold nanoparticles (Au NPs) based plasmonic probe was developed for sensitive and selective detection of Cu(2+) ion. The Au NPs were self-assembled on transparent indium tin oxide (ITO) film coated glass substrate using poly dimethyl diallyl ammonium chloride (PDDA) as a linker and then calcined at 400°C to obtain pure Au NPs on ITO surface (ITO/Au NPs). The probe was fabricated by functionalizing l-cysteine (Cys) on to gold surface (ITO/Au NPs/Cys). The strong chelation of Cu(2+) with Cys formed a stable Cys-Cu complex, and resulted in the red-shift of localized surface plasmon resonance (LSPR) peak of the Au NPs. The introduction of bovine serum albumin (BSA) as the second complexant could form complex of Cys-Cu-BAS and further markedly enhanced the red-shift of the LSPR peak. This plasmonic probe provided a highly sensitive and selective detection towards Cu(2+) ions, with a wide linear detection range (10(-11)-10(-5)M) over 6 orders of magnitude. The simple and cost-effective probe was successfully applied to the determination of Cu(2+) in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Paper based Flexible and Conformal SERS Substrate for Rapid Trace Detection on Real-world Surfaces

NASA Astrophysics Data System (ADS)

Singamaneni, Srikanth; Lee, Chang; Tian, Limei

2011-03-01

One of the important but often overlooked considerations in the design of surface enhanced Raman scattering (SERS) substrates for trace detection is the efficiency of sample collection. Conventional designs based on rigid substrates such as silicon, alumina, and glass resist conformal contact with the surface under investigation, making the sample collection inefficient. We demonstrate a novel SERS substrate based on common filter paper adsorbed with gold nanorods, which allows conformal contact with real-world surfaces, thus dramatically enhancing the sample collection efficiency compared to conventional rigid substrates. We demonstrate the detection of trace amounts of analyte (140 pg spread over 4 cm2) by simply swabbing the surface under investigation with the novel SERS substrate. The hierarchical fibrous structure of paper serves as a 3D vasculature for easy uptake and transport of the analytes to the electromagnetic hot spots in the paper. Simple yet highly efficient and cost effective SERS substrate demonstrated here brings SERS based trace detection closer to real-world applications. We acknowledge the financial support from Center for Materials Innovation at Washington University.

Engineered Metallic Nanostructures: Fabrication, Characterization, and Applications

NASA Astrophysics Data System (ADS)

Bohloul, Arash

Metallic nanostructures have garnered a great deal of attention due to their fascinating optical properties, which differ from the bulk metal. They have been proven to exceed expectations in wide variety of applications including chemical and biological sensing. Nevertheless, high-throughput and low cost nanofabrication techniques are required to implant metallic nanostructures in widespread applications. With that vision, this thesis presents a versatile and reliable method for scalable fabrication of gold nanostructures. In this approach, a plasma-treated ordered array of polystyrene nanospheres acts as an initial mask. The key step in this process is the vapor-deposition of nickel as a sacrificial mask. Thereby, gold nanostructures are directly formed on the substrate through the nickel mask. This is an easy, powerful, and straightforward method that offers several degrees of freedom to precisely control the shape and size of nanostructures. We made a library of nanostructures including gold nanocrescents, double crescents, nanorings, and nanodisks with the ability to tune the size in the range of 150 to 650 nm. The fabricated nanostructures are highly packed and uniformly cover the centimeter scale substrate. The optical properties of metallic nanostructures were extensively studied by a combination of UV-Vis-NIR and Fourier transform infrared (FTIR) spectroscopies, and correlation between optical response and geometrical parameters were investigated. In the next part of this thesis, highly sensitive surface enhanced infrared absorption (SEIRA) analysis was demonstrated on gold nanocrescent arrays. Theoretical modeling was confirmed that these substrates provide highly dense and strong hot-spots over the substrate, which is required for surface enhanced spectroscopic studies. Gold nanocrescent arrays exhibit highly tunable plasmon resonance to cover desired molecular vibrational bands. These substrates experimentally illustrated 3 orders of magnitude enhancement of IR signal over the entire substrate and up to 5 orders of magnitude enhancement on hot-spot area. Finally, we showed that fabricated substrates are completely biocompatible for growth, adhesion, and proliferation of human dermal fibroblast cells. Leveraging the capability of gold nanocrescent arrays to enhance IR signals, we developed a real time SEIRA spectroscopic technique for label-free biological cell analysis. The performance of proposed method was assessed by in situ tracking the SEIRA signal of human dermal fibroblast cells cultured on gold nanocrescent arrays.

Orthogonal chemical functionalization of patterned gold on silica surfaces

PubMed Central

Léonard, Didier; Le Mogne, Thierry; Zuttion, Francesca; Chevalier, Céline; Phaner-Goutorbe, Magali; Souteyrand, Éliane

2015-01-01

Summary Single-step orthogonal chemical functionalization procedures have been developed with patterned gold on silica surfaces. Different combinations of a silane and a thiol were simultaneously deposited on a gold/silica heterogeneous substrate. The orthogonality of the functionalization (i.e., selective grafting of the thiol on the gold areas and the silane on the silica) was demonstrated by X-ray photoelectron spectroscopy (XPS) as well as time-of-flight secondary ion mass spectrometry (ToF–SIMS) mapping. The orthogonal functionalization was used to immobilize proteins onto gold nanostructures on a silica substrate, as demonstrated by atomic force microscopy (AFM). These results are especially promising in the development of future biosensors where the selective anchoring of target molecules onto nanostructured transducers (e.g., nanoplasmonic biosensors) is a major challenge. PMID:26734519

Improving surface-enhanced Raman scattering effect using gold-coated hierarchical polystyrene bead substrates modified with postgrowth microwave treatment.

PubMed

Yuen, Clement; Zheng, Wei; Huang, Zhiwei

2008-01-01

We report a novel postgrowth microwave heating implementation by selectively modifying hierarchical polystyrene (PS) bead substrates coated with gold (Au) films to effectively improve the surface-enhanced Raman scattering (SERS) effect on the analytes. The SERS signal of probe molecule rhodamine 6G (Rh 6G) on the microwave-treated Au-PS substrates can be improved by 10-fold, while the detection limit of Rh 6G in concentration can be enhanced by two orders of magnitude compared to the as-growth substrates. The high-quality SERS spectrum of saliva can also be acquired using the modified substrates, demonstrating the potential for the realization of the high-performance SERS substrates for biomedical applications.

Melanin as an active layer in biosensors

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

Piacenti da Silva, Marina, E-mail: marinaness@yahoo.com; Congiu, Mirko, E-mail: congiumat@gmail.com; Oliveira Graeff, Carlos Frederico de, E-mail: graeff@fc.unesp.br

2014-03-15

The development of pH sensors is of great interest due to its extensive application in several areas such as industrial processes, biochemistry and particularly medical diagnostics. In this study, the pH sensing properties of an extended gate field effect transistor (EGFET) based on melanin thin films as active layer are investigated and the physical mechanisms related to the device operation are discussed. Thin films were produced from different melanin precursors on indium tin oxide (ITO) and gold substrates and were investigated by Atomic Force Microscopy and Electrochemical Impedance Spectroscopy. Experiments were performed in the pH range from 2 to 12.more » EGFETs with melanin deposited on ITO and on gold substrates showed sensitivities ranging from 31.3 mV/pH to 48.9 mV/pH, depending on the melanin precursor and the substrate used. The pH detection is associated with specific binding sites in its structure, hydroxyl groups and quinone imine.« less

Aerosol assisted chemical vapour deposition of gas sensitive SnO2 and Au-functionalised SnO2 nanorods via a non-catalysed vapour solid (VS) mechanism

PubMed Central

Vallejos, Stella; Selina, Soultana; Annanouch, Fatima Ezahra; Gràcia, Isabel; Llobet, Eduard; Blackman, Chris

2016-01-01

Tin oxide nanorods (NRs) are vapour synthesised at relatively lower temperatures than previously reported and without the need for substrate pre-treatment, via a vapour-solid mechanism enabled using an aerosol-assisted chemical vapour deposition method. Results demonstrate that the growth of SnO2 NRs is promoted by a compression of the nucleation rate parallel to the substrate and a decrease of the energy barrier for growth perpendicular to the substrate, which are controlled via the deposition conditions. This method provides both single-step formation of the SnO2 NRs and their integration with silicon micromachined platforms, but also allows for in-situ functionalization of the NRs with gold nanoparticles via co-deposition with a gold precursor. The functional properties are demonstrated for gas sensing, with microsensors using functionalised NRs demonstrating enhanced sensing properties towards H2 compared to those based on non-functionalised NRs. PMID:27334232

Highly efficient SERS substrate for direct detection of explosive TNT using popcorn-shaped gold nanoparticle-functionalized SWCNT hybrid.

PubMed

Demeritte, Teresa; Kanchanapally, Rajashekhar; Fan, Zhen; Singh, Anant Kumar; Senapati, Dulal; Dubey, Madan; Zakar, Eugene; Ray, Paresh Chandra

2012-11-07

This paper reports for the first time the development of a large-scale SERS substrate from a popcorn-shaped gold nanoparticle-functionalized single walled carbon nanotubes hybrid thin film for the selective and highly sensitive detection of explosive TNT material at a 100 femtomolar (fM) level.

Au-Assisted Substrate-Faceting for Inclined Nanowire Growth.

PubMed

Kang, Jung-Hyun; Krizek, Filip; Zaluska-Kotur, Magdalena; Krogstrup, Peter; Kacman, Perla; Beidenkopf, Haim; Shtrikman, Hadas

2018-06-12

We study the role of gold droplets in the initial stage of nanowire growth via the vapor-liquid-solid method. Apart from serving as a collections center for growth species, the gold droplets carry an additional crucial role that necessarily precedes the nanowire emergence, that is, they assist the nucleation of nanocraters with strongly faceted {111}B side walls. Only once these facets become sufficiently large and regular, the gold droplets start nucleating and guiding the growth of nanowires. We show that this dual role of the gold droplets can be detected and monitored by high-energy electron diffraction during growth. Moreover, gold-induced formation of craters and the onset of nanowires growth on the {111}B facets inside the craters are confirmed by the results of Monte Carlo simulations. The detailed insight into the growth mechanism of inclined nanowires will help to engineer new and complex nanowire-based device architectures.

Gold nanoparticles deposited on glass: physicochemical characterization and cytocompatibility

PubMed Central

2013-01-01

Properties of gold films sputtered under different conditions onto borosilicate glass substrate were studied. Mean thickness of sputtered gold film was measured by gravimetry, and film contact angle was determined by goniometry. Surface morphology was examined by atomic force microscopy, and electrical sheet resistance was determined by two-point technique. The samples were seeded with rat vascular smooth muscle cells, and their adhesion and proliferation were studied. Gold depositions lead to dramatical changes in the surface morphology and roughness in comparison to pristine substrate. For sputtered gold structures, the rapid decline of the sheet resistance appears on structures deposited for the times above 100 s. The thickness of deposited gold nanoparticles/layer is an increasing function of sputtering time and current. AFM images prove the creation of separated gold islands in the initial deposition phase and a continuous gold coverage for longer deposition times. Gold deposition has a positive effect on the proliferation of vascular smooth muscle cells. Largest number of cells was observed on sample sputtered with gold for 20 s and at the discharge current of 40 mA. This sample exhibits lowest contact angle, low relative roughness, and only mild increase of electrical conductivity. PMID:23705782

A quantitative literature-curated gold standard for kinase-substrate pairs

PubMed Central

2011-01-01

We describe the Yeast Kinase Interaction Database (KID, http://www.moseslab.csb.utoronto.ca/KID/), which contains high- and low-throughput data relevant to phosphorylation events. KID includes 6,225 low-throughput and 21,990 high-throughput interactions, from greater than 35,000 experiments. By quantitatively integrating these data, we identified 517 high-confidence kinase-substrate pairs that we consider a gold standard. We show that this gold standard can be used to assess published high-throughput datasets, suggesting that it will enable similar rigorous assessments in the future. PMID:21492431

Nanoparticle-nanoparticle vs. nanoparticle-substrate hot spot contributions to the SERS signal: studying Raman labelled monomers, dimers and trimers.

PubMed

Sergiienko, Sergii; Moor, Kamila; Gudun, Kristina; Yelemessova, Zarina; Bukasov, Rostislav

2017-02-08

We used a combination of Raman microscopy, AFM and TEM to quantify the influence of dimerization on the surface enhanced Raman spectroscopy (SERS) signal for gold and silver nanoparticles (NPs) modified with Raman reporters and situated on gold, silver, and aluminum films and a silicon wafer. The overall increases in the mean SERS enhancement factor (EF) upon dimerization (up by 43% on average) and trimerisation (up by 96% on average) of AuNPs and AgNPs on the studied metal films are within a factor of two, which is moderate when compared to most theoretical models. However, the maximum ratio of EFs for some dimers to the mean EF of monomers can be as high as 5.5 for AgNPs on a gold substrate. In contrast, for dimerization and trimerization of gold and silver NPs on silicon, the mean EF increases by 1-2 orders of magnitude relative to the mean EF of single NPs. Therefore, hot spots in the interparticle gap between gold nanoparticles rather than hot spots between Au nanoparticles and the substrate dominate SERS enhancement for dimers and trimers on a silicon substrate. However, Raman labeled noble metal nanoparticles on plasmonic metal films generate on average SERS enhancement of the same order of magnitude for both types of hot spot zones (e.g. NP/NP and NP/metal film).

Stable Carboxylate-Terminated Gold Surfaces Produced by Spontaneous Grafting of an Alkyl Tin Compound.

PubMed

Ortiz, Mayreli; Mehdi, Ahmed; Methivier, Christophe; Thorimbert, Serge; Hasenknopf, Bernold; O'Sullivan, Ciara K

2018-05-21

Self-assembled monolayers formed by chemisorption of thiolated molecules on gold surfaces are widely applied for biosensing. Moreover, and due to the low stability of thiol-gold chemistry, contributions to the functionalisation of gold substrates with linkers that provide a more stable platform for the immobilisation of electroactive or biological molecules are highly appreciated. In the work reported here, we demonstrate that a carboxylated organotin compound can be successfully grafted onto gold substrates to form a highly stable organic layer with reactivity for subsequent binding to an aminated molecule. A battery of techniques was used to characterise the surface chemistry. The grafted layer was used to anchor aminoferrocene and subjected to both thermostability tests and long term stability studies over the period of one year, demonstrating thermostability up to 90 oC and storage stability for at least 12 months when stored at 4 oC protected from light. The stable surface tethering of molecules on gold substrates can be exploited in a plethora of applications including molecular techniques such as solid-phase amplification and solid-phase melting curve analysis that require elevated temperature stability, as well as biosensors, which require long-term storage stability. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Determining Concentration of Nanoparticles from Ellipsometry

NASA Technical Reports Server (NTRS)

Venkatasubbarao, Srivatsa; Kempen, Lothar U.; Chipman, Russell

2008-01-01

A method of using ellipsometry or polarization analysis of light in total internal reflection of a surface to determine the number density of gold nanoparticles on a smooth substrate has been developed. The method can be modified to enable determination of densities of sparse distributions of nanoparticles in general, and is expected to be especially useful for measuring gold-nanoparticle-labeled biomolecules on microarrays. The method is based on theoretical calculations of the ellipsometric responses of gold nanoparticles. Elements of the calculations include the following: For simplicity, the gold nanoparticles are assumed to be spherical and to have the same radius. The distribution of gold nanoparticles is assumed to be a sub-monolayer (that is, sparser than a monolayer). The optical response of the sub-monolayer is modeled by use of a thin-island-film theory, according to which the polarizabilities parallel and perpendicular to the substrate are functions of the wavelength of light, the dielectric functions (permittivities expressed as complex functions of frequency or wavelength) of the gold and the suspending medium (in this case, the suspending medium is air), the fraction of the substrate area covered by the nanoparticles, and the radius of the nanoparticles. For the purpose of the thin-island-film theory, the dielectric function of the gold nanoparticles is modeled as the known dielectric function of bulk gold plus a correction term that is necessitated by the fact that the mean free path length for electrons in gold decreases with decreasing radius, in such a manner as to cause the imaginary part of the dielectric function to increase with decreasing radius (see figure). The correction term is a function of the nanoparticle radius, the wavelength of light, the mean free path and the Fermi speed of electrons in bulk gold, the plasma frequency of gold, and the speed of light in a vacuum. These models are used to calculate ellipsometric responses for various concentrations of gold nanoparticles having an assumed radius. The modeled data indicates distinct spectral features for both the real and the imaginary part of the dielectric function. An ellipsometric measurement would determine this distinct feature and thus can be used to measure nanoparticle concentration. By "ellipsometric responses" is meant the intensities of light measured in various polarization states as functions of the angle of incidence and the polarization states of the incident light. These calculated ellipsometric responses are used as calibration curves: Data from subsequent ellipsometric measurements on real specimens are compared with the calibration curves. The concentration of the nanoparticles on a specimen is assumed to be that of the calibration curve that most closely matches the data pertaining to that specimen.

The XPS depth profiling and tribological characterization of ion-plated gold on various metals

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1983-01-01

Friction properties were measured with a gold film; the graded interface between gold and nickel substrate; and the nickel substrate. All sliding was conducted against hard silicon carbide pins in two processes. In the adhesive process, friction arises primarily from adhesion between sliding surfaces. In the abrasion process, friction occurs as a result of the hard pin sliding against the film, indenting into it, and plowing a series of grooves. Copper and 440 C stainless steel substrates were also used. Results indicate that the friction related to both adhesion and abrasion is influenced by coating depth. The trends in friction behavior as a function of film depth are, however, just the opposite. The graded interface exhibited the highest adhesion and friction, while the graded interface resulted in the lowest abrasion and friction. The coefficient of friction due to abrasion is inversely related to the hardness. The greater the hardness of the surface, the lower is the abrasion and friction. The microhardness in the graded interface exhibited the highest hardness due to an alloy hardening effect. Almost no graded interface between the vapor-deposited gold film and the substrates was detected.

Synthesis of Stretchable Gold Films with Nanocracks: Stretched up to 120% Strain while Maintaining Conductivity

NASA Astrophysics Data System (ADS)

Yu, Mei; Wang, Chong; Yang, Cancan; Yu, Zhe

2017-11-01

With the great deformability of stretch, compression, bend and twisting, while preserving electrical property, metal films on elastomeric substrates have many applications for serving as bioelectrical interfaces. However, at present, most polymer-supported thin metal films reported rupture at small elongations (<10%). In this work, highly stretchable thin gold films were fabricated on PDMS substrates by a novel micro-processing technology. The as deposited films can be stretched by a maximum 120% strain while maintaining their electrical conductivity. Electrical characteristics of the gold films under single-cycle and multi-cycle stretch deformations are investigated in this work. SEM images imply that the gold films are under the structure of nanocracks. The mechanisms of the stretchability of the gold films can be explained by the nanocraks, which uniformly distribute with random orientation in the films.

Fountain-pen-based laser microstructuring with gold nanoparticle inks

NASA Astrophysics Data System (ADS)

Choi, Tae Y.; Poulikakos, Dimos; Grigoropoulos, Costas P.

2004-07-01

Employing the fountain-pen principle, a micropipette is used to write an Au nanoparticle ink on glass substrates. A continuous-wave laser (488-515nm) is subsequently used as a controlled, localized energy source to evaporate the carrier liquid (toluene) in the ink and sinter the nanoparticles together thus fabricating continuous gold stripes 5μm in width and a few hundred nanometers in height. The scanning speed, the laser intensity, and the degree of defocusing are identified as important parameters to the successful manufacturing of the gold microstructures. The electrical resistivity of the stripes, within the parametric domain of the present work, is measured to be the order of 10-6Ωm.

Graphene electrodes for stimulation of neuronal cells

NASA Astrophysics Data System (ADS)

Koerbitzer, Berit; Krauss, Peter; Nick, Christoph; Yadav, Sandeep; Schneider, Joerg J.; Thielemann, Christiane

2016-06-01

Graphene has the ability to improve the electrical interface between neuronal cells and electrodes used for recording and stimulation purposes. It provides a biocompatible coating for common electrode materials such as gold and improves the electrode properties. Graphene electrodes are also prepared on SiO2 substrate to benefit from its optical properties like transparency. We perform electrochemical and Raman characterization of gold electrodes with graphene coating and compare them with graphene on SiO2 substrate. It was found that the substrate plays an important role in the performance of graphene and show that graphene on SiO2 substrate is a very promising material combination for stimulation electrodes.

Ten Ghz YBa2Cu3O(7-Delta) Superconducting Ring Resonators on NdGaO3 Substrates

NASA Technical Reports Server (NTRS)

To, H. Y.; Valco, G. J.; Bhasin, K. B.

1993-01-01

YBa2Cu3O(7-delta) thin films were formed on NdGaO3 substrates by laser ablation. Critical temperatures greater than 89 K and critical current densities exceeding 2 x 10(exp 8) Acm(sub -2) at 77 K were obtained. The microwave performance of films patterned into microstrip ring resonators with gold ground planes was measured. An unloaded quality factor six times larger than that of a gold resonator of identical geometry was achieved. The unloaded quality factor decreased below 70 K for both the superconducting and gold resonators due to increasing dielectric losses in the substrate. The temperature dependence of the loss tangent of NdGaO3 was extracted from the measurements.

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands

PubMed Central

Vasconcelos, Helena

2018-01-01

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO2) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency. PMID:29677108

Plasmonic Optical Fiber Sensor Based on Double Step Growth of Gold Nano-Islands.

PubMed

de Almeida, José M M M; Vasconcelos, Helena; Jorge, Pedro A S; Coelho, Luis

2018-04-20

It is presented the fabrication and characterization of optical fiber sensors for refractive index measurement based on localized surface plasmon resonance (LSPR) with gold nano-islands obtained by single and by repeated thermal dewetting of gold thin films. Thin films of gold deposited on silica (SiO₂) substrates and produced by different experimental conditions were analyzed by Scanning Electron Microscope/Dispersive X-ray Spectroscopy (SEM/EDS) and optical means, allowing identifying and characterizing the formation of nano-islands. The wavelength shift sensitivity to the surrounding refractive index of sensors produced by single and by repeated dewetting is compared. While for the single step dewetting, a wavelength shift sensitivity of ~60 nm/RIU was calculated, for the repeated dewetting, a value of ~186 nm/RIU was obtained, an increase of more than three times. It is expected that through changing the fabrication parameters and using other fiber sensor geometries, higher sensitivities may be achieved, allowing, in addition, for the possibility of tuning the plasmonic frequency.

Implementation of molecularly imprinted polymer beads for surface enhanced Raman detection.

PubMed

Kamra, Tripta; Zhou, Tongchang; Montelius, Lars; Schnadt, Joachim; Ye, Lei

2015-01-01

Molecularly imprinted polymers (MIPs) have a predesigned molecular recognition capability that can be used to build robust chemical sensors. MIP-based chemical sensors allow label-free detection and are particularly interesting due to their simple operation. In this work we report the use of thiol-terminated MIP microspheres to construct surfaces for detection of a model organic analyte, nicotine, by surface enhanced Raman scattering (SERS). The nicotine-imprinted microspheres are synthesized by RAFT precipitation polymerization and converted into thiol-terminated microspheres through aminolysis. The thiol groups on the MIP surface allow the microspheres to be immobilized on a gold-coated substrate. Three different strategies are investigated to achieve surface enhanced Raman scattering in the vicinity of the imprinted sites: (1) direct sputtering of gold nanoparticles, (2) immobilization of gold colloids through the MIP's thiol groups, and (3) trapping of the MIP microspheres in a patterned SERS substrate. For the first time we show that large MIP microspheres can be turned into selective SERS surfaces through the three different approaches of assembly. The MIP-based sensing surfaces are used to detect nicotine to demonstrate the proof of concept. As synthesis and surface functionalization of MIP microspheres and nanoparticles are well established, the methods reported in this work are handy and efficient for constructing label-free chemical sensors, in particular for those based on SERS detection.

Dealloying of gold–copper alloy nanowires: From hillocks to ring-shaped nanopores

PubMed Central

Chauvin, Adrien; Delacôte, Cyril; Boujtita, Mohammed; Angleraud, Benoit; Ding, Junjun; Choi, Chang-Hwan; Tessier, Pierre-Yves

2016-01-01

Summary We report on a novel fabrication approach of metal nanowires with complex surface. Taking advantage of nodular growth triggered by the presence of surface defects created intentionally on the substrate as well as the high tilt angle between the magnetron source axis and the normal to the substrate, metal nanowires containing hillocks emerging out of the surface can be created. The approach is demonstrated for several metals and alloys including gold, copper, silver, gold–copper and gold–silver. We demonstrate that applying an electrochemical dealloying process to the gold–copper alloy nanowire arrays allows for transforming the hillocks into ring-like shaped nanopores. The resulting porous gold nanowires exhibit a very high roughness and high specific surface making of them a promising candidate for the development of SERS-based sensors. PMID:27826510

Gold Redox Catalysis through Base-Initiated Diazonium Decomposition toward Alkene, Alkyne, and Allene Activation.

PubMed

Dong, Boliang; Peng, Haihui; Motika, Stephen E; Shi, Xiaodong

2017-08-16

The discovery of photoassisted diazonium activation toward gold(I) oxidation greatly extended the scope of gold redox catalysis by avoiding the use of a strong oxidant. Some practical issues that limit the application of this new type of chemistry are the relative low efficiency (long reaction time and low conversion) and the strict reaction condition control that is necessary (degassing and inert reaction environment). Herein, an alternative photofree condition has been developed through Lewis base induced diazonium activation. With this method, an unreactive Au I catalyst was used in combination with Na 2 CO 3 and diazonium salts to produce a Au III intermediate. The efficient activation of various substrates, including alkyne, alkene and allene was achieved, followed by rapid Au III reductive elimination, which yielded the C-C coupling products with good to excellent yields. Relative to the previously reported photoactivation method, our approach offered greater efficiency and versatility through faster reaction rates and broader reaction scope. Challenging substrates such as electron rich/neutral allenes, which could not be activated under the photoinitiation conditions (<5 % yield), could be activated to subsequently yield the desired coupling products in good to excellent yield. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Ultrasensitive Gold Nanoparticle-based Lateral Flow Test for the Detection of Active Botulinum Neurotoxin Type A

NASA Astrophysics Data System (ADS)

Liu, Jing; Gao, Shan; Kang, Lin; Ji, Bin; Xin, Wenwen; Kang, Jingjing; Li, Ping; Gao, Jie; Wang, Hanbin; Wang, Jinglin; Yang, Hao

2017-03-01

Botulism is a severe and potentially lethal paralytic disease caused by several botulinum neurotoxin-producing Clostridia spp. In China, the majority of the cases caused by botulism were from less-developed rural areas. Here, we designed specific substrate peptides and reconfigured gold nanoparticle-based lateral flow test strip (LFTS) to develop an endopeptidase-based lateral flow assay for the diagnosis of botulism. We performed this lateral flow assay on botulinum neurotoxin-spiked human serum samples. The as-prepared LFTS had excellent performance in the detection of botulinum neurotoxin using only 1 μL of simulated serum, and its sensitivity and specificity were comparable to that of mouse lethality assay. Moreover, the assay takes only half a day and does not require highly trained laboratory staff, specialized facility, or equipment. Finally, our LFTS can be potentially extended to other serotypes of BoNTs by designing specific substrate peptides against the different types of BoNTs. Overall, we demonstrate a strategy by which LFTS and endopeptidase activity assays can be integrated to achieve facile and economic diagnosis of botulism in resource-limited settings.

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

Liu, Fang; Xie, Dong Yue; Majdi, Tahereh

By applying a simple and inexpensive thermal treatment, we synthesized supported gold-oxide nanostructures, which have potential applications to plasmonic devices and biosensors. The regrowth of nominally stable substrates under gold nanoparticles is associated with the appearance of preferential orientations of dewetted nanoparticles and the formation of atomically sharp interfacial monolayers. Steps present at the interfacial monolayer usually occur at defects including the intersection points of twin planes at the interface. They were related to the nucleation and immigration of the interfacial monolayers, prompting the substrate regrowth. Accordingly, we proposed the twin-assisted growth mechanism, which provides insight on the synthesis ofmore » gold-oxide nanostructures. - Highlights: • The twin-assisted growth mechanism is proposed for the abnormal regrowth of substrate underneath Au nanoparticles. • The substrate regrowth is related to the steps and ledges that are present at the Au–MgAl{sub 2}O{sub 4} interfacial monolayers. • Interfacial steps are detected at defects such as the intersecting points of twin planes at the interface.« less

Enhancement of local surface plasmon resonance (LSPR) effect by biocompatible metal clustering based on ZnO nanorods in Raman measurements.

PubMed

Lee, Sanghwa; Lee, Seung Ho; Paulson, Bjorn; Lee, Jae-Chul; Kim, Jun Ki

2018-06-20

The development of size-selective and non-destructive detection techniques for nanosized biomarkers has many reasons, including the study of living cells and diagnostic applications. We present an approach for Raman signal enhancement on biocompatible sensing chips based on surface enhancement Raman spectroscopy (SERS). A sensing chip was fabricated by forming a ZnO-based nanorod structure so that the Raman enhancement occurred at a gap of several tens to several hundred nanometers. The effect of coffee-ring formation was eliminated by introducing the porous ZnO nanorods for the bio-liquid sample. A peculiarity of this approach is that the gold sputtered on the ZnO nanorods initially grows at their heads forming clusters, as confirmed by secondary electron microscopy. This clustering was verified by finite element analysis to be the main factor for enhancement of local surface plasmon resonance (LSPR). This clustering property and the ability to adjust the size of the nanorods enabled the signal acquisition points to be refined using confocal based Raman spectroscopy, which could be applied directly to the sensor chip based on the optimization process in this experiment. It was demonstrated by using common cancer cell lines that cell growth was high on these gold-clad ZnO nanorod-based surface-enhanced Raman substrates. The porosity of the sensing chip, the improved structure for signal enhancement, and the cell assay make these gold-coated ZnO nanorods substrates promising biosensing chips with excellent potential for detecting nanometric biomarkers secreted by cells. Copyright © 2018 Elsevier B.V. All rights reserved.

Directed Self-Assembly of Diblock Copolymer Thin Films on Prepatterned Metal Nanoarrays.

PubMed

Chang, Tongxin; Huang, Haiying; He, Tianbai

2016-01-01

The sequential layer by layer self-assembly of block copolymer (BCP) nanopatterns is an effective approach to construct 3D nanostructures. Here large-scale highly ordered metal nano-arrays prepared from solvent annealed thin films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer are used to direct the assembly of the same BCP. The influence of initial loading concentration of metal precursor, the type of metal nanoparticle (gold, platinum, and silver), and the nanoparticle-substrate interaction on the directed assembly behavior of the upper BCP layer have been focused. It is found that the upper BCP film can be completely directed by the gold nanoarray with P2VP domain exclusively located between two adjacent gold nanowires or nanodots, which behaves the same way as on the platinum nanoarray. While the silver nanoarray can be destroyed during the upper BCP self-assembly with the silver nanoparticles assembled into the P2VP domain. Based on the discussions of the surface energy of nanoparticles and the interplay between nanoparticle-substrate interaction and nanoparticle-polymer interaction, it is concluded that the effect of immobilization of nanoparticles on the substrate, together with entropy effect to minimize the energetically unfavorable chain stretching contributes to the most effective alignment between each layer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Patterning of oxide-hardened gold black by photolithography and metal lift-off

Treesearch

Deep Panjwani; Mehmet Yesiltas; Janardan Nath; D.E. Maukonen; Imen Rezadad; Evan M. Smith; R.E. Peale; Carol Hirschmugl; Julia Sedlmair; Ralf Wehlitz; Miriam Unger; Glenn Boreman

2014-01-01

A method to pattern infrared-absorbing gold black by conventional photolithography and lift-off is described. A photo-resist pattern is developed on a substrate by standard photolithography. Gold black is deposited over the whole by thermal evaporation in an inert gas at

Hot-Electron Bolometer Mixers on Silicon-on-Insulator Substrates for Terahertz Frequencies

NASA Technical Reports Server (NTRS)

Skalare, Anders; Stern, Jeffrey; Bumble, Bruce; Maiwald, Frank

2005-01-01

A terahertz Hot-Electron Bolometer (HEB) mixer design using device substrates based on Silicon-On-Insulator (SOI) technology is described. This substrate technology allows very thin chips (6 pm) with almost arbitrary shape to be manufactured, so that they can be tightly fitted into a waveguide structure and operated at very high frequencies with only low risk for power leakages and resonance modes. The NbTiN-based bolometers are contacted by gold beam-leads, while other beamleads are used to hold the chip in place in the waveguide test fixture. The initial tests yielded an equivalent receiver noise temperature of 3460 K double-sideband at a local oscillator frequency of 1.462 THz and an intermediate frequency of 1.4 GHz.

Templated electrochemical deposition of zirconia thin films on "recordable CDs.".

PubMed

Yu, Hua-Zhong; Rowe, Aaron W; Waugh, Damien M

2002-11-15

In this paper, we describe a practical method of using gold films constructed from recordable compact disks (CD-Rs) as simple, inexpensive, and micropatterned conductive substrates for the fabrication of inorganic material microstructures. Extending from their application for the fabrication of self-assembled monolayers (SAMs) reported recently, bare and SAM-modified CD-R gold substrates have been used for template-directed electrodeposition of zirconia (ZrO2) thin films (i.e., the controlled formation of zirconia thin films on the different areas of the prefabricated, micrometer mountain-valley CD-R gold substrate surfaces). The present results demonstrate that the variation of the functional groups of the selected SAMs combined with electrodynamic control can be very successful to "customize" the formation and microstructure of functional inorganic thin films, which hold promise for modern technological applications.

Gallium arsenide/gold nanostructures deposited using plasma method

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

Mangla, O.; Physics Department, Hindu College, University of Delhi, Delhi, 110007; Roy, S.

2016-05-23

The fabrication of gallium arsenide (GaAs) nanostructures on gold coated glass, quartz and silicon substrates using the high fluence and highly energetic ions has been reported. The high fluence and highly energetic ions are produced by the hot, dense and extremely non-equilibrium plasma in a modified dense plasma focus device. The nanostructures having mean size about 14 nm, 13 nm and 18 nm are deposited on gold coated glass, quartz and silicon substrates, respectively. The optical properties of nanostructures studied using absorption spectra show surface plasmon resonance peak of gold nanoparticles. In addition, the band-gap of GaAs nanoparticles is more than that ofmore » bulk GaAs suggesting potential applications in the field of optoelectronic and sensor systems.« less

Surface Coverage and Structure of Mixed DNA/Alkylthiol Monolayers on Gold: Characterization by XPS, NEXAFS, and Fluorescence Intensity Measurements

PubMed Central

Lee, Chi-Ying; Gong, Ping; Harbers, Gregory M.; Grainger, David W.; Castner, David G.; Gamble, Lara J.

2006-01-01

Self-assembly of thiol-terminated single-stranded DNA (HS-ssDNA) on gold has served as an important model system for DNA immobilization at surfaces. Here, we report a detailed study of the surface composition and structure of mixed self-assembled DNA monolayers containing a short alkylthiol surface diluent [11-mercapto-1-undecanol (MCU)] on gold supports. These mixed DNA monolayers were studied with X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure spectroscopy (NEXAFS), and fluorescence intensity measurements. XPS results on sequentially adsorbed DNA/MCU monolayers on gold indicated that adsorbed MCU molecules first incorporate into the HS-ssDNA monolayer and, upon longer MCU exposures, displace adsorbed HS-ssDNA molecules from the surface. Thus, HS-ssDNA surface coverage steadily decreased with MCU exposure time. Polarization-dependent NEXAFS and fluorescence results both show changes in signals consistent with changes in DNA orientation after only 30 min of MCU exposure. NEXAFS polarization dependence (followed by monitoring the N 1s → π* transition) of the mixed DNA monolayers indicated that the DNA nucleotide base ring structures are oriented more parallel to the gold surface compared to DNA bases in pure HS-ssDNA monolayers. This indicates that HS-ssDNA oligomers reorient toward a more-upright position upon MCU incorporation. Fluorescence intensity results using end-labeled DNA probes on gold show little observable fluorescence on pure HS-ssDNA monolayers, likely due to substrate quenching effects between the fluorophore and the gold. MCU diluent incorporation into HS-ssDNA monolayers initially increases DNA fluorescence signal by densifying the chemisorbed monolayer, prompting an upright orientation of the DNA, and moving the terminal fluorophore away from the substrate. Immobilized DNA probe density and DNA target hybridization in these mixed DNA monolayers, as well as effects of MCU diluent on DNA hybridization in complex milieu (i.e., serum) were characterized by surface plasmon resonance (SPR) and 32P-radiometric assays and reported in a related study PMID:16689533

Thin-film ultraviolet detector and spectrometer

NASA Technical Reports Server (NTRS)

Lewicki, G. W.; Maserjian, J.

1972-01-01

Typical metal-insulator-metal detector device is formed on quartz substrate. Base electrode is 3 to 6 nm aluminum layer, overcoated with 3 to 6 nm aluminum oxide or aluminum nitride, and capped with counter electrode of gold, lead, magnesium, or aluminum. Photoelectric yield data are given for Al-AlN-Au structure.

Self-organized broadband light trapping in thin film amorphous silicon solar cells.

PubMed

Martella, C; Chiappe, D; Delli Veneri, P; Mercaldo, L V; Usatii, I; Buatier de Mongeot, F

2013-06-07

Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p-i-n type thin film a-Si:H solar cells.

Thiolated poly(ɛ-caprolactone) macroligand with vacant coordination sites on gold substrate: Synthesis and surface characterization

NASA Astrophysics Data System (ADS)

Farah, Abdiaziz A.; Zheng, Susan H.; Morin, Sylvie; Bensebaa, Farid; Pietro, William J.

2007-04-01

Surface-confined telechelic poly(ɛ-caprolactone) macroligand with two distinct functional groups per polymeric chain has been synthesized and characterized. The molecular microstructure of the macroligand with regard to the properties of the end-capped functionalities and with those on surface substrate has been studied by solution and surface analytical methods (i.e., X-ray photoelectron spectroscopy (XPS), grazing angle reflectance-Fourier transform IR spectroscopy (GA-FTIR), water contact angle measurements, and atomic force microscopy (AFM)) to elucidate the structure and properties of such multifunctional polymer on gold (1 1 1) substrate.

Surface enhanced Raman spectroscopy analysis of HeLa cells using a multilayer substrate

NASA Astrophysics Data System (ADS)

Aguilar-Hernández, I. A.; Pichardo-Molina, J. L.; Lopez-Luke, T.; Ornelas-Soto, N.

2017-08-01

Single cell analysis can provide important information regarding cell composition, and can be used for biomedical applications. In this work, a SERS active substrate formed by 3 layers of gold nanospheres and a final layer of gold nanocubes was used for the label-free SERS analysis of HeLa cells. Nanocubes were selected due to the high electromagnetic enhancement expected in nanoparticles with sharp corners. Significant improvement in the reproducibility and quality of SERS spectra was found when compared to the spectra obtained using a nanosphere-only substrate and normal Raman spectroscopy.

Characterization of self-assembled monolayers (SAMs) on silicon substrate comparative with polymer substrate for Escherichia coli O157:H7 detection

NASA Astrophysics Data System (ADS)

Moldovan, Carmen; Mihailescu, Carmen; Stan, Dana; Ruta, Lavinia; Iosub, Rodica; Gavrila, Raluca; Purica, Munizer; Vasilica, Schiopu

2009-08-01

This article presents the characterization of two substrates, silicon and polymer coated with gold, that are functionalized by mixed self-assembled monolayers (SAMs) in order to efficiently immobilize the anti- Escherichia coli O157:H7 polyclonal purified antibody. A biosurface functionalized by SAMs (self-assembled monolayers) technique has been developed. Immobilization of goat anti- E. coli O157:H7 antibody was performed by covalently bonding of thiolate mixed self-assembled monolayers (SAMs) realized on two substrates: polymer coated with gold and silicon coated with gold. The F(ab') 2 fragments of the antibodies have been used for eliminating nonspecific bindings between the Fc portions of antibodies and the Fc receptor on cells. The properties of the monolayers and the biofilm formatted with attached antibody molecules were analyzed at each step using infrared spectroscopy (FTIR-ATR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and cyclic voltammetry (CV). In our study the gold-coated silicon substrates approach yielded the best results. These experimental results revealed the necessity to investigate each stage of the immobilization process taking into account in the same time the factors that influence the chemistry of the surface and the further interactions as well and also provide a solid basis for further studies aiming at elaborating sensitive and specific immunosensor or a microarray for the detection of E. coli O157:H7.

Oxide mediated liquid-solid growth of high aspect ratio aligned gold silicide nanowires on Si(110) substrates.

PubMed

Bhatta, Umananda M; Rath, Ashutosh; Dash, Jatis K; Ghatak, Jay; Yi-Feng, Lai; Liu, Chuan-Pu; Satyam, P V

2009-11-18

Silicon nanowires grown using the vapor-liquid-solid method are promising candidates for nanoelectronics applications. The nanowires grow from an Au-Si catalyst during silicon chemical vapor deposition. In this paper, the effect of temperature, oxide at the interface and substrate orientation on the nucleation and growth kinetics during formation of nanogold silicide structures is explained using an oxide mediated liquid-solid growth mechanism. Using real time in situ high temperature transmission electron microscopy (with 40 ms time resolution), we show the formation of high aspect ratio ( approximately 15.0) aligned gold silicide nanorods in the presence of native oxide at the interface during in situ annealing of gold thin films on Si(110) substrates. Steps observed in the growth rate and real time electron diffraction show the existence of liquid Au-Si nano-alloy structures on the surface besides the un-reacted gold nanostructures. These results might enable us to engineer the growth of nanowires and similar structures with an Au-Si alloy as a catalyst.

Gold nanoparticles-based protease assay

PubMed Central

Guarise, Cristian; Pasquato, Lucia; De Filippis, Vincenzo; Scrimin, Paolo

2006-01-01

We describe here a simple assay that allows the visual detection of a protease. The method takes advantage of the high molar absorptivity of the plasmon band of gold colloids and is based on the color change of their solution when treated with dithiols. We used C- and N-terminal cysteinyl derivatives of a peptide substrate exploiting its selective recognition and cleavage by a specific protease. Contrary to the native ones, cleaved peptides are unable to induce nanoparticles aggregation; hence, the color of the solution does not change. The detection of two proteases is reported: thrombin (involved in blood coagulation and thrombosis) and lethal factor (an enzyme component of the toxin produced by Bacillus anthracis). The sensitivity of this nanoparticle-based assay is in the low nanomolar range. PMID:16537471

Gold nanoparticles-based protease assay.

PubMed

Guarise, Cristian; Pasquato, Lucia; De Filippis, Vincenzo; Scrimin, Paolo

2006-03-14

We describe here a simple assay that allows the visual detection of a protease. The method takes advantage of the high molar absorptivity of the plasmon band of gold colloids and is based on the color change of their solution when treated with dithiols. We used C- and N-terminal cysteinyl derivatives of a peptide substrate exploiting its selective recognition and cleavage by a specific protease. Contrary to the native ones, cleaved peptides are unable to induce nanoparticles aggregation; hence, the color of the solution does not change. The detection of two proteases is reported: thrombin (involved in blood coagulation and thrombosis) and lethal factor (an enzyme component of the toxin produced by Bacillus anthracis). The sensitivity of this nanoparticle-based assay is in the low nanomolar range.

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.

Paper-basd surface enhanced Raman spectroscopy of pnenobarbital sodium for point-of-care therapeutic drug monitoring

NASA Astrophysics Data System (ADS)

Yokoyama, Moe; Yamada, Kenji; Nishimura, Takahiro; Kido, Michiko; Jeong, Hieyong; Ohno, Yuko

2015-03-01

Therapeutic drug monitoring (TDM) contributes to safe and effective pharmacotherapy in clinical fields. A simple, rapid, low-cost, and minimally-invasive drug measurement method attracts much interest for point-of-care TDM. Tear fluids can be collected minimally-invasively compared to blood sampling and there is a correlation between a drug concentration in tears and that in bloods. Surface enhanced Raman spectroscopy (SERS) with paper-based substrate is useful for point-of-care TDM owing to inexpensiveness and high-sensitivity. Paper is also a safe tear collection tool. Then we are studying on a paper-based SERS of tear specimen for point-of-care TDM. In this paper, to improve sensitivity in measuring drug concentration in tear fluids, we fabricated a SERS substrate by coating gold nano-rods on a paper substrate and evaluated whether the fabricated substrate can enhance Raman scattering. Sodium phenobarbital (PB), an anti-convulsant agent, was used as a target. In experiment, the fabricated substrate indicated the lower detection limit of PB in a solution than a plain paper substrate. This result showed the potential of the paper based SERS substrate to measure drug concentration in tears simply and inexpensively.

A new technique to detect antibody-antigen reaction (biological interactions) on a localized surface plasmon resonance (LSPR) based nano ripple gold chip

NASA Astrophysics Data System (ADS)

Saleem, Iram; Widger, William; Chu, Wei-Kan

2017-07-01

We demonstrate that the gold nano-ripple localized surface plasmon resonance (LSPR) chip is a low cost and a label-free method for detecting the presence of an antigen. A uniform stable layer of an antibody was coated on the surface of a nano-ripple gold pattern chip followed by the addition of different concentrations of the antigen. A red shift was observed in the LSPR spectral peak caused by the change in the local refractive index in the vicinity of the nanostructure. The LSPR chip was fabricated using oblique gas cluster ion beam (GCIB) irradiation. The plasmon-resonance intensity of the scattered light was measured by a simple optical spectroscope. The gold nano ripple chip shows monolayer scale sensitivity and high selectivity. The LSPR substrate was used to detect antibody-antigen reaction of rabbit X-DENTT antibody and DENTT blocking peptide (antigen).

Bifunctional nanoparticles for surface-enhanced Raman spectroscopy-based leukemia biomarker detection

NASA Astrophysics Data System (ADS)

Mehn, Dora; Morasso, Carlo; Vanna, Renzo; Schiumarini, Domitilla; Bedoni, Marzia; Ciceri, Fabio; Gramatica, Furio

2014-03-01

The Wilms tumor gene (WT1) is a biomarker overexpressed in more than 90% of acute myeloid leukemia patients. Fast and sensitive detection of the WT1 in blood samples would allow monitoring of the minimal residual disease during clinical remission and would permit early detection of a potential relapse in acute myeloid leukemia. In this work, Surface Enhanced Raman Spectroscopy (SERS) based detection of the WT1 sequence using bifunctional, magnetic core - gold shell nanoparticles is presented. The classical co-precipitation method was applied to generate magnetic nanoparticles which were coated with a gold shell after modification with aminopropyltriethoxy silane and subsequent deposition of gold nanoparticle seeds. Simple hydroquinone based reduction procedure was applied for the shell growing in water based reaction mixture at room temperature. Thiolated ssDNA probes of the WT1 sequence were immobilized as capture oligonucleotides on the gold surface. Malachite green was applied both for testing the amplification performance of the core-shell colloidal SERS substrate and also as label dye of the target DNA sequence. The SERS enhancer efficacy of the core-shell nanomaterial was compared with the efficacy of classical spherical gold particles produced using the conventional citrate reduction method. The core-shell particles were found not only to provide an opportunity for facile separation in a heterogeneous reaction system but also to be superior regarding robustness as SERS enhancers.

A practical method to fabricate gold substrates for surface-enhanced Raman spectroscopy.

PubMed

Tantra, Ratna; Brown, Richard J C; Milton, Martin J T; Gohil, Dipak

2008-09-01

We describe a practical method of fabricating surface-enhanced Raman spectroscopy (SERS) substrates based on dip-coating poly-L-lysine derivatized microscope slides in a gold colloidal suspension. The use of only commercially available starting materials in this preparation is particularly advantageous, aimed at both reducing time and the inconsistency associated with surface modification of substrates. The success of colloid deposition has been demonstrated by scanning electron microscopy (SEM) and the corresponding SERS response (giving performance comparable to the corresponding traditional colloidal SERS substrates). Reproducibility was evaluated by conducting replicate measurements across six different locations on the substrate and assessing the extent of the variability (standard deviation values of spectral parameters: peak width and height), in response to either Rhodamine 6G or Isoniazid. Of particular interest is the observation of how some peaks in a given spectrum are more susceptible to data variability than others. For example, in a Rhodamine 6G SERS spectrum, spectral parameters of the peak at 775 cm(-1) were shown to have a relative standard deviation (RSD) % of <10%, while the peak at 1573 cm(-1) has a RSD of >or=10%. This observation is best explained by taking into account spectral variations that arise from the effect of a chemisorption process and the local nature of chemical enhancement mechanisms, which affects the enhancement of some spectral peaks but not others (analogous to resonant Raman phenomenon).

Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

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

Harnisch, Jennifer Anne

2001-01-01

The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic performancemore » both in conventional liquid chromatographic columns and EMLC columns. Additionally, one may also exploit the creation of aryl films to by electroreduction of arenediazonium salts in the creation of nanostructured materials. The formation of mercaptobenzene film on the surface of a GC electrode provides a linking platform for the chemisorption of gold nanoparticles. After deposition of nanoparticles, the surface chemistry of the gold can be further altered by self-assembled monolayer (SAM) formation via the chemisorption of a second thiol species. Finally, the properties of gold films can be altered such that they display carbon-like behavior through the formation of benzenehexathiol (BHT) SAMs. BHT chemisorbs to the gold surface in a previously unprecedented planar fashion. Carbon and gold substrates can be chemically altered by several methodologies resulting in new surface properties. The development of modification protocols and their application in the analytical arena is considered herein.« less

SERS Engineering Collaboration

DTIC Science & Technology

2012-06-01

laser beam. In the second approach, a pulsed laser was used to texture a silicon wafer to form sharp features. Silver was evaporated onto the wafer...orders of magnitude larger than that measured on a gold nanoparticle array on a glass substrate. The largest SERS enhancement for a silver device was...surface plasmons," Yizhuo Chu and Kenneth B. Crozier, Optics Letters vol. 34, 244 (2009) K3. "Gold nanorings as substrates for surface-enhanced Raman

Development of electrodes for the NASA iron/chromium

NASA Technical Reports Server (NTRS)

Swette, L.; Jalan, V.

1984-01-01

This program was directed primarily to the development of the negative (Cr3+/Cr2+) electrode for the NASA chromous/ferric Redox battery. The investigation of the effects of substrate processing and gold/lead catalyzation parameters on electrochemical performance were continued. In addition, the effects of reactant cross-mixing, acidity level, and temperature were examined for both Redox couples. Finally, the performance of optimized electrodes was tested in system hardware (1/3 square foot single cell). The major findings are discussed: (1) The recommended processing temperature for the carbon felt, as a substrate for the negative electrode, is 1650 to 1750 C, (2) The recommended gold catalyzation procedure is essentially the published NASA procedure (NASA TM-82724, Nov. 1981) based on deposition from aqueous methanol solution, with the imposition of a few controls such as temperature (25 C) and precatalyzation pH of the felt (7), (3) Experimental observations of the gold catalyzation process and subsequent electron microscopy indicate that the gold is deposited from the colloidal state, induced by contact of the solution with the carbon felt, (4) Electrodeposited lead appears to be present as a thin uniform layer over the entire surface of the carbon fibers, rather than an discrete particles, and (5) Cross-mixing of reactants (Fe-2+ in negative electrode solution or Cr-3+ in the positive electrode solution) did not appear to produce significant interference at either electrode.

Morphology manipulation of M13 bacteriophage template for nanostructure assembly

NASA Astrophysics Data System (ADS)

Ngo-Duc, Tam-Triet; Zaman, Mohammed S.; Moon, Chung-Hee; Haberer, Elaine D.

2014-08-01

A gold-binding M13 bacteriophage was used as a model system to explore templating of inorganic material on geometrically transformed viruses . Gold-binding filamentous phage were converted to spheroid form with a short chloroform treatment, and the resulting morphology was investigated with electron microscopy. Binding studies revealed that spheroid-shaped gold-binding phage preserved its affinity for gold. Spheroids adhered to a planar substrate assembled clusters or rings of gold nanoparticles. This gold-binding phage served as a demonstration of a highly shape-modifiable viral-template for inorganic materials.

Metal oxide nanorod arrays on monolithic substrates

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

Gao, Pu-Xian; Guo, Yanbing; Ren, Zheng

A metal oxide nanorod array structure according to embodiments disclosed herein includes a monolithic substrate having a surface and multiple channels, an interface layer bonded to the surface of the substrate, and a metal oxide nanorod array coupled to the substrate surface via the interface layer. The metal oxide can include ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide. The substrate can include a glass substrate, a plastic substrate, a silicon substrate, a ceramic monolith, and a stainless steel monolith. The ceramic can include cordierite, alumina, tin oxide, and titania. The nanorod array structure can includemore » a perovskite shell, such as a lanthanum-based transition metal oxide, or a metal oxide shell, such as ceria, zinc oxide, tin oxide, alumina, zirconia, cobalt oxide, and gallium oxide, or a coating of metal particles, such as platinum, gold, palladium, rhodium, and ruthenium, over each metal oxide nanorod. Structures can be bonded to the surface of a substrate and resist erosion if exposed to high velocity flow rates.« less

Gold Nanorods as Surface-Enhanced Raman Spectroscopy Substrates for Rapid and Sensitive Analysis of Allura Red and Sunset Yellow in Beverages.

PubMed

Ou, Yiming; Wang, Xiaohui; Lai, Keqiang; Huang, Yiqun; Rasco, Barbara A; Fan, Yuxia

2018-03-21

Synthetic colorants in food can be a potential threat to human health. In this study, surface-enhanced Raman spectroscopy (SERS) coupled with gold nanorods as substrates is proposed to analyze allura red and sunset yellow in beverages. The gold nanorods with different aspect ratios were synthesized, and their long-term stability, SERS activity, and the effect of the different salts on the SERS signal were investigated. The results demonstrate that gold nanorods have a satisfactory stability (stored up to 28 days). SERS coupled with gold nanorods exhibit stronger sensitivity. MgSO 4 was chosen to improve the SERS signal of sunset yellow, and no salts could enhance the SERS signal of allura red. The lowest concentration was 0.10 mg/L for both colorant standard solutions. The successful prediction results using SERS were much closer to those obtained by high-performance liquid chromatography for the sample in beverages. SERS combined with gold nanorods shows potential for analyzing food colorants and other food additives as a rapid, convenient, and sensitive method.

Xanthan/chitosan gold chip for metal enhanced protein biomarker detection.

PubMed

Domnanich, Patrick; Peña, Dacimoneida Brito; Preininger, Claudia

2011-01-15

Protein microarrays for disease diagnostics are required to accurately quantify analytes in the low pg/mL range. This task is hampered by weak signal strengths and too low detector sensitivity. Herein we present reflective gold chips coated with polyelectrolyte multilayers (PEMs) for signal enhancement in immunoassays for melanoma-relevant biomarkers. Among tested (semi)natural polysaccharides (xanthan, chitosan, carboxymethylcellulose, hyaluronic acid) PEMs composed of xanthan and chitosan performed best in terms of detection of low analyte concentrations (ED10), spot morphology, fluorescence background and variability (<10%). Fluorescence signals on gold slides with a 75 nm coating of seven crosslinked polyelectrolyte double layers were up to 50 times higher than on bare glass slides. In comparison to commercial substrates the signal to noise ratio is enhanced by up to factor 11. Furthermore sandwich assays for interleukins 6, 8, 10, tumour necrosis factor alpha (TNFα), vascular endothelial growth factor A (VEGF-A) and S100B show working ranges which cover significantly lower concentrations (up to 38-fold). Not limited to above assays the presented substrates, which combine a biocompatible interface with metal-based signal amplification, are a valuable tool in a variety of biosensor applications. Copyright © 2010 Elsevier B.V. All rights reserved.

Tailoring uniform gold nanoparticle arrays and nanoporous films for next-generation optoelectronic devices

NASA Astrophysics Data System (ADS)

Farid, Sidra; Kuljic, Rade; Poduri, Shripriya; Dutta, Mitra; Darling, Seth B.

2018-06-01

High-density arrays of gold nanodots and nanoholes on indium tin oxide (ITO)-coated glass surfaces are fabricated using a nanoporous template fabricated by the self-assembly of diblock copolymers of poly (styrene-block-methyl methacrylate) (PS-b-PMMA) structures. By balancing the interfacial interactions between the polymer blocks and the substrate using random copolymer, cylindrical block copolymer microdomains oriented perpendicular to the plane of the substrate have been obtained. Nanoporous PS films are created by selectively etching PMMA cylinders, a straightforward route to form highly ordered nanoscale porous films. Deposition of gold on the template followed by lift off and sonication leaves a highly dense array of gold nanodots. These materials can serve as templates for the vapor-liquid-solid (VLS) growth of semiconductor nanorod arrays for next generation hybrid optoelectronic applications.

Large-area surface-enhanced Raman spectroscopy imaging of brain ischemia by gold nanoparticles grown on random nanoarrays of transparent boehmite.

PubMed

Yamazoe, Shogo; Naya, Masayuki; Shiota, Megumi; Morikawa, Takayuki; Kubo, Akiko; Tani, Takeharu; Hishiki, Takako; Horiuchi, Tadashi; Suematsu, Makoto; Kajimura, Mayumi

2014-06-24

Although SERS spectroscopy, which is sensitive to molecular vibration states, offers label-free visualization of molecules, identification of molecules and their reliable large-area imaging remains to be developed. Limitation comes from difficulties in fabricating a SERS-active substrate with homogeneity over a large area. Here, we overcome this hurdle by utilizing a self-assembled nanostructure of boehmite that is easily achieved by a hydrothermal preparation of aluminum as a template for subsequent gold (Au) deposition. This approach brought about random arrays of Au-nanostructures with a diameter of ∼125 nm and a spacing of <10 nm, ideal for the hot-spots formation. The substrate, which we named "gold nanocoral" (GNC) after its coral reef-like shape, exhibited a small variability of signal intensities (coefficient value <11.2%) in detecting rhodamine 6G molecule when 121 spots were measured over an area of 10 × 10 mm(2), confirming high uniformity. The transparent nature of boehmite enabled us to conduct the measurement from the back-side of the substrate as efficiently as that from the front-side. We then conducted tissue imaging using the mouse ischemic brain adhered on the GNC substrate. Through nontargeted construction of two-dimensional-Raman-intensity map using differential bands from two metabolically distinct regions, that is, ischemic core and contralateral-control areas, we found that mapping using the adenine ring vibration band at 736 cm(-1) clearly demarcated ischemic core where high-energy adenine phosphonucleotides were degraded as judged by imaging mass spectrometry. Such a detection capability makes the GNC-based SERS technology especially promising for revealing acute energy derangement of tissues.

Gold-catalysed oxyarylation of styrenes and mono- and gem-disubstituted olefins facilitated by an iodine(III) oxidant.

PubMed

Ball, Liam T; Lloyd-Jones, Guy C; Russell, Christopher A

2012-03-05

1-Hydroxy-1,2-benziodoxol-3(1H)-one (IBA) is an efficient terminal oxidant for gold-catalysed, three-component oxyarylation reactions. The use of this iodine(III) reagent expands the scope of oxyarylation to include styrenes and gem-disubstituted olefins, substrates that are incompatible with the previously reported Selectfluor-based methodology. Diverse arylsilane coupling partners can be employed, and in benzotrifluoride, homocoupling is substantially reduced. In addition, the IBA-derived co-products can be recovered and recycled. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Observation of phonon-polaritons in thin flakes of hexagonal boron nitride on gold

NASA Astrophysics Data System (ADS)

Ciano, C.; Giliberti, V.; Ortolani, M.; Baldassarre, L.

2018-04-01

Hexagonal Boron Nitride (hBN) is a layered van der Waals material able to sustain hyperbolic phonon-polaritons within its mid-infrared reststrahlen bands. We study the effect of a metallic substrate adjacent to hBN flakes on the polariton dispersion and on the standing wave patterns in nanostructures by means of mid-infrared nanospectroscopy and nanoimaging. We exploit the gold-coated tip apex for atomic force microscopy to launch polaritons in thin hBN flakes. The photo-thermal induced mechanical resonance is used to detect the amplitude profile of polariton standing waves with a lateral resolution of 30 nm. We observe the polariton excitation spectra on hBN flakes as thin as 4 nm, thanks to the infrared field enhancement in the nanogap between the gold-coated tip apex and an ultraflat gold substrate. The data indicate no major effect of remote screening of the free electrons in gold on the phonon-polariton excitation that appears robust also against geometrical imperfections.

Spectroscopy on the wing: naturally inspired SERS substrates for biochemical analysis.

PubMed

Garrett, Natalie L; Vukusic, Peter; Ogrin, Feodor; Sirotkin, Evgeny; Winlove, C Peter; Moger, Julian

2009-03-01

We show that naturally occurring chitinous nanostructures found on the wings of the Graphium butterfly can be used as substrates for surface-enhanced Raman scattering when coated with a thin film of gold or silver. The substrates were found to exhibit excellent biocompatibility and sensitivity, making them ideal for protein assaying. An assay using avidin/biotin binding showed that the substrates could be used to quantify protein binding directly from changes in the surface-enhanced Raman scattering (SERS) spectra and were sensitive over a concentration range comparable with a typical enzyme-linked immunosorbent assays (ELISA) assay. A biomimetic version of the wing nanostructures produced using a highly reproducible, large-scale fabrication process, yielded comparable enhancement factors and biocompatibility. The excellent biocompatibility of the wings and biomimetic substrates is unparalleled by other lithographically produced substrates, and this could pave the way for widespread application of ultrasensitive SERS-based bioassays.

Self-Powered Forward Error-Correcting Biosensor Based on Integration of Paper-Based Microfluidics and Self-Assembled Quick Response Codes.

PubMed

Yuan, Mingquan; Liu, Keng-Ku; Singamaneni, Srikanth; Chakrabartty, Shantanu

2016-10-01

This paper extends our previous work on silver-enhancement based self-assembling structures for designing reliable, self-powered biosensors with forward error correcting (FEC) capability. At the core of the proposed approach is the integration of paper-based microfluidics with quick response (QR) codes that can be optically scanned using a smart-phone. The scanned information is first decoded to obtain the location of a web-server which further processes the self-assembled QR image to determine the concentration of target analytes. The integration substrate for the proposed FEC biosensor is polyethylene and the patterning of the QR code on the substrate has been achieved using a combination of low-cost ink-jet printing and a regular ballpoint dispensing pen. A paper-based microfluidics channel has been integrated underneath the substrate for acquiring, mixing and flowing the sample to areas on the substrate where different parts of the code can self-assemble in presence of immobilized gold nanorods. In this paper we demonstrate the proof-of-concept detection using prototypes of QR encoded FEC biosensors.

Electrical response of culture media during bacterial growth on a paper-based device

NASA Astrophysics Data System (ADS)

Srimongkon, Tithimanan; Buerkle, Marius; Nakamura, Akira; Enomae, Toshiharu; Ushijima, Hirobumi; Fukuda, Nobuko

2017-05-01

In this work, we evaluated the feasibility of a paper-based bacterial detection system. The paper served as a substrate for the measurement electrodes and the culture medium. Using a printing technique, we patterned gold electrodes onto the paper substrate and applied Luria broth (LB) agar gel as a culture medium on top of the electrodes. As the first step towards the development of a bacterial detection system, we determined changes in the surface potential during bacterial growth and monitored these changes over 24 h. This allowed us to correlate changes in the surface potential with the different growth phases of the bacteria.

Flexible and disposable plasmonic refractive index sensor using nanoimprint lithography

NASA Astrophysics Data System (ADS)

Mohapatra, Saswat; Moirangthem, Rakesh S.

2018-03-01

Nanostructure based plasmonic sensors are highly demanding in various areas due to their label-free and real-time detection capability. In this work, we developed an inexpensive flexible plasmonic sensor using optical disc nanograting via soft UV-nanoimprint lithography (UV-NIL). The polydimethylsiloxane (PDMS) stamp was used to transfer the nanograting structure from digital versatile discs (DVDs) to flexible and transparent polyethylene terephthalate (PET) substrate. Further, the plasmonic sensing substrate was obtained after coating a gold thin film on the top of the imprinted sample. The surface plasmon resonance (SPR) modes excited on gold coated nanograting structure appeared as a dip in the reflectance spectra measured at normal incident of white light in ambient air medium. Electromagnetic simulation based on finite element method (FEM) was used to understand and analyze the excited SPR modes and it is a very close agreement with the experimental results. The bulk refractive index (RI) sensing was performed by the sensor chip using water-glycerol mixture with different concentrations. Experimentally, the bulk RI sensitivity was found to be 797+/-17 nm/RIU.

Electromagnetic wave propagation along T and Y-splitters composed of silicon nanorods, gold slots, and silica substrate

NASA Astrophysics Data System (ADS)

Ahmadivand, Arash; Pala, Nezih; Golmohammadi, Saeed

2015-05-01

Silicon nanorods in arrays on a glass substrate that are situated through a gap between two gold slots have been utilized to design efficient long-range optical nanostructures as splitters to function at near infrared spectrum. Designing silicon arrays in T and Y-shape regimes, we examined the optical responses of the proposed devices during guiding of transverse and longitudinal electric modes (TE and LE-modes). Transmission loss factors, group velocity of guided waves, the ratio of transmitted power, and the decay length for both of the devices have been reported using numerical methods. We showed that the proposed structures have strong potentials to employ in designing photonic structures with lower ratio of energy extinction and low radiation losses. The overall length of the structures is 2.2 μm which verifies its compaction in comparison to analogous splitters that are designed based on DLSPPWs and nanoparticle-based waveguides devices. Proposed subwavelength optical power transportation mechanisms are highly compatible to employ in photonic integration circuit (PIC) systems.

Unraveling the complexity of the interactions of DNA nucleotides with gold by single molecule force spectroscopy

NASA Astrophysics Data System (ADS)

Bano, Fouzia; Sluysmans, Damien; Wislez, Arnaud; Duwez, Anne-Sophie

2015-11-01

Addressing the effect of different environmental factors on the adsorption of DNA to solid supports is critical for the development of robust miniaturized devices for applications ranging from biosensors to next generation molecular technology. Most of the time, thiol-based chemistry is used to anchor DNA on gold - a substrate commonly used in nanotechnology - and little is known about the direct interaction between DNA and gold. So far there have been no systematic studies on the direct adsorption behavior of the deoxyribonucleotides (i.e., a nitrogenous base, a deoxyribose sugar, and a phosphate group) and on the factors that govern the DNA-gold bond strength. Here, using single molecule force spectroscopy, we investigated the interaction of the four individual nucleotides, adenine, guanine, cytosine, and thymine, with gold. Experiments were performed in three salinity conditions and two surface dwell times to reveal the factors that influence nucleotide-Au bond strength. Force data show that, at physiological ionic strength, adenine-Au interactions are stronger, asymmetrical and independent of surface dwell time as compared to cytosine-Au and guanine-Au interactions. We suggest that in these conditions only adenine is able to chemisorb on gold. A decrease of the ionic strength significantly increases the bond strength for all nucleotides. We show that moderate ionic strength along with longer surface dwell period suggest weak chemisorption also for cytosine and guanine.Addressing the effect of different environmental factors on the adsorption of DNA to solid supports is critical for the development of robust miniaturized devices for applications ranging from biosensors to next generation molecular technology. Most of the time, thiol-based chemistry is used to anchor DNA on gold - a substrate commonly used in nanotechnology - and little is known about the direct interaction between DNA and gold. So far there have been no systematic studies on the direct adsorption behavior of the deoxyribonucleotides (i.e., a nitrogenous base, a deoxyribose sugar, and a phosphate group) and on the factors that govern the DNA-gold bond strength. Here, using single molecule force spectroscopy, we investigated the interaction of the four individual nucleotides, adenine, guanine, cytosine, and thymine, with gold. Experiments were performed in three salinity conditions and two surface dwell times to reveal the factors that influence nucleotide-Au bond strength. Force data show that, at physiological ionic strength, adenine-Au interactions are stronger, asymmetrical and independent of surface dwell time as compared to cytosine-Au and guanine-Au interactions. We suggest that in these conditions only adenine is able to chemisorb on gold. A decrease of the ionic strength significantly increases the bond strength for all nucleotides. We show that moderate ionic strength along with longer surface dwell period suggest weak chemisorption also for cytosine and guanine. Electronic supplementary information (ESI) available: Details of the data analysis; Fig. S1-S5 histograms of rupture lengths; histograms for Au-adenine and Au-amine interactions; Force-extension curve for MCH-Au interactions; normalized force-extension curves; theoretical length of the DNA oligomers. See DOI: 10.1039/c5nr05695k

Fabrication and modeling of stretchable conductors for traumatic brain injury research

NASA Astrophysics Data System (ADS)

Cao, Wenzhe

Stretchable electronics are an emergent class of electronics that can retain their electric functionality under large mechanical deformation, such as stretching, bending and compression. Like traditional electric circuits, stretchable electronics rely on electrical conductors, but in this specific instance the conductors must also be stretchable. This thesis research had three goals: (1) fabricate elastically stretchable conductors that retain their electrical conductance when stretched by tens of percent of strain; (2) understand the underlying stretching mechanism of gold conductors on polydimethylsiloxane (PDMS) substrates; (3) produce a special device---a stretchable microelectrode array, which contains a matrix of stretchable conductors that enables a new approach to studying traumatic brain injury. We first developed and optimized the micro-fabrication process to make elastically stretchable thin gold film conductors on PDMS substrates. The conductors can retain electrical conduction while being stretched reversibly to 140% uniaxially and 16% radially. We further developed a fabrication process to encapsulate the conductors with either a commercially available photopatternable silicone (PPS) or with PDMS. 100 microm by 100 microm vias were patterned in the encapsulation layer to expose electrical contacts. PPS encapsulated conductors can be stretched uniaxially to 80%, and the PDMS encapsulated conductor can be stretched to ˜15%, without losing electrical conduction. We also introduced acrylate-based shape memory polymers (SMPs) as a new type of substrate for stretchable conductors. Their stiffness can be tuned by varying the monomer composition or by changing the ambient temperature. Thin gold film conductors deposited on pre-strained SMPs remain conductive when first stretched and then relaxed to their pre-strain value. Moreover, an SMP can also serve as a stretchable carrier to make pre-strained conductors on an overlying PDMS membrane. The resistance of gold conductors made on pre-strained PDMS changes less during stretching than that made on non-pre-strained PDMS substrate. We built a model of the electrical resistance in function of strain. The model is based on the topography of the thin gold film on PDMS. This model is a first attempt at predicting electrical resistance of stretchable thin gold film conductors. Lastly, we fabricated stretchable microelectrode arrays (SMEAs). They were utilized at Columbia University to study traumatic brain injury (TBI). Tissues cultured on SMEA remained viable for 19 days, and the electrodes were able to both stimulate and record neural tissue activity before, during and after stretching. Therefore SMEAs are able to bring together mechanical injury, electrophysiological recording and pharmacological studies. The SMEAs could serve as in vitro platforms for high throughput therapeutic screening and discovery for traumatic injury. The ability to reproducibly fabricate stretchable conductors using micro-fabrication technology will facilitate adoption by industry. The ability to understand the stretching mechanism will enable us to design more robust material systems. The SMEA prototypes demonstrate that stretchable conductors are practical, and their mechanical compatibility with biological systems also makes them candidates for use in biomedical devices.

A rapid approach to prepare poly(2-methyl-2-oxazoline)-based antifouling coating by UV irradiation

NASA Astrophysics Data System (ADS)

Zhu, Haikun; Mumtaz, Fatima; Zhang, Chong; Tan, Lin; Liu, Songtao; Zhang, Yalin; Pan, Chao; Wang, Yanmei

2017-12-01

A series of brush copolymers, poly[(2-methyl-2-oxazoline)-random-4-vinylpyridine] (PMOXA-r-4VP), with a variety of compositions was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of the poly(2-methyl-2-oxazoline) methacrylate macromonomer (PMOXA-MA) and 4-vinylpyridine (4VP), and then characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The PMOXA-based coatings on the surfaces of glass, silicon, gold and polydimethylsiloxane (PDMS) substrates were then produced by short-time ultraviolet (UV) irradiation of PMOXA-r-4VP. Water contact angel (WCA), ellipsometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and ζ-potential techniques were used to characterize the coatings. The results showed that copolymers can be successfully bonded on the surfaces of glass, silicon, gold, and PDMS substrate. Besides, the PMOXA-based coatings displayed a superior resistance to bovine serum albumin, human blood platelets, Human Umbilical Vein Endothelial Cells adsorption and good biocompatibility. Finally, stability test indicated that the stability of coatings can be improved with the content of the 4VP segment. Furthermore, PMOXA-r1/2-4VP immobilized surfaces displayed good antifouling property in long-term applications.

Highly sensitive nano-porous lattice biosensor based on localized surface plasmon resonance and interference.

PubMed

Yeom, Se-Hyuk; Kim, Ok-Geun; Kang, Byoung-Ho; Kim, Kyu-Jin; Yuan, Heng; Kwon, Dae-Hyuk; Kim, Hak-Rin; Kang, Shin-Won

2011-11-07

We propose a design for a highly sensitive biosensor based on nanostructured anodized aluminum oxide (AAO) substrates. A gold-deposited AAO substrate exhibits both optical interference and localized surface plasmon resonance (LSPR). In our sensor, application of these disparate optical properties overcomes problems of limited sensitivity, selectivity, and dynamic range seen in similar biosensors. We fabricated uniform periodic nanopore lattice AAO templates by two-step anodizing and assessed their suitability for application in biosensors by characterizing the change in optical response on addition of biomolecules to the AAO template. To determine the suitability of such structures for biosensing applications, we immobilized a layer of C-reactive protein (CRP) antibody on a gold coating atop an AAO template. We then applied a CRP antigen (Ag) atop the immobilized antibody (Ab) layer. The shift in reflectance is interpreted as being caused by the change in refractive index with membrane thickness. Our results confirm that our proposed AAO-based biosensor is highly selective toward detection of CRP antigen, and can measure a change in CRP antigen concentration of 1 fg/ml. This method can provide a simple, fast, and sensitive analysis for protein detection in real-time.

Self-assembled nanospheres with multiple endohedral binding sites pre-organize catalysts and substrates for highly efficient reactions

NASA Astrophysics Data System (ADS)

Wang, Qi-Qiang; Gonell, Sergio; Leenders, Stefan H. A. M.; Dürr, Maximilian; Ivanović-Burmazović, Ivana; Reek, Joost N. H.

2016-03-01

Tuning reagent and catalyst concentrations is crucial in the development of efficient catalytic transformations. In enzyme-catalysed reactions the substrate is bound—often by multiple non-covalent interactions—in a well-defined pocket close to the active site of the enzyme; this pre-organization facilitates highly efficient transformations. Here we report an artificial system that co-encapsulates multiple catalysts and substrates within the confined space defined by an M12L24 nanosphere that contains 24 endohedral guanidinium-binding sites. Cooperative binding means that sulfonate guests are bound much more strongly than carboxylates. This difference has been used to fix gold-based catalysts firmly, with the remaining binding sites left to pre-organize substrates. This strategy was applied to a Au(I)-catalysed cyclization of acetylenic acid to enol lactone in which the pre-organization resulted in much higher reaction rates. We also found that the encapsulated sulfonate-containing Au(I) catalysts did not convert neutral (acid) substrates, and so could have potential in the development of substrate-selective catalysis and base-triggered on/off switching of catalysis.

An evaluation of wear when enamel is opposed by various ceramic materials and gold.

PubMed

Elmaria, Asmaa; Goldstein, Gary; Vijayaraghavan, Therizhandur; Legeros, Raquel Z; Hittelman, Eugene L

2006-11-01

Ceramic restorations have been known to cause wear of opposing enamel. The purpose of this study was to evaluate enamel wear caused by 3 ceramic substrates in the glazed and polished conditions. Sixty ceramic discs (10 x 2 mm)-20 each of Finesse, All-Ceram, and IPS-Empress-were prepared and glazed. Each group of 20 was divided into 2 groups of 10. The surfaces of one group were ground and polished using a porcelain polishing kit (Dialite). The remaining 10 were left as glazed. Ten specimens of a type III gold alloy were cast into rectangular shapes of 10 x 12 x 2 mm and polished. Seventy human cusps were prepared from sound, caries-free, extracted teeth and abraded against the substrates in a wear machine for a total of 10,000 cycles. The cusp height loss was traced before and after the wear test using a profile projector. Mean surface roughness (R(a)) values for the substrates were also recorded with a profilometer before testing. Differences in R(a) were evaluated using 1- and 2-way ANOVA and the Scheffe post hoc test (alpha = .05). One-way ANOVA indicated that enamel height loss was significantly different by material (P < .001) and surface condition (glazed and polished or glazed; P < .05). Gold, polished Finesse, and polished All-Ceram were the least abrasive, whereas glazed IPS-Empress was the most abrasive. There was no significant interaction effect between substrate type and surface condition. Significant differences were found when R(a) of the substrate condition was compared with enamel wear (P < .01). Gold, polished Finesse, and polished All-Ceram caused the least enamel wear, whereas IPS-Empress caused the most wear. Cast gold was significantly different than glazed IPS-Empress (P < .05), whereas other groups overlapped. There was significant correlation between R(a) and enamel wear (P < .01).

New insight into UO 2F 2 particulate structure by micro-Raman spectroscopy

DOE PAGES

Stefaniak, Elzbieta A.; Darchuk, Larysa; Sapundjiev, Danislav; ...

2013-02-19

Uranyl fluoride particles produced via hydrolysis of uranium hexafluoride have been deposited on different substrates: polished graphite disks, silver foil, stainless steel and gold-coated silicon wafer, and measured with micro-Raman spectroscopy (MRS). All three metallic substrates enhanced the Raman signal delivered by UO 2F 2 in comparison to graphite. The fundamental stretching of the U–O band appeared at 867 cm –1 in case of the graphite substrate, while in case of the others it was shifted to lower frequencies (down to 839 cm –1). All applied metallic substrates showed the expected effect of Raman signal enhancement; however the gold layermore » appeared to be most effective. Lastly, application of new substrates provides more information on the molecular structure of uranyl fluoride precipitation, which is interesting for nuclear safeguards and nuclear environmental analysis.« less

Laser writing of single-crystalline gold substrates for surface enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

Singh, Astha; Sharma, Geeta; Ranjan, Neeraj; Mittholiya, Kshitij; Bhatnagar, Anuj; Singh, B. P.; Mathur, Deepak; Vasa, Parinda

2017-07-01

Surface enhanced Raman scattering (SERS) spectroscopy, a powerful contemporary tool for studying low-concentration analytes via surface plasmon induced enhancement of local electric field, is of utility in biochemistry, material science, threat detection, and environmental studies. We have developed a simple, fast, scalable, and relatively low-cost optical method of fabricating and characterizing large-area, reusable and broadband SERS substrates with long storage lifetime. We use tightly focused, intense infra-red laser pulses to write gratings on single-crystalline, Au (1 1 1) gold films on mica which act as SERS substrates. Our single-crystalline SERS substrates compare favourably, in terms of surface quality and roughness, to those fabricated in poly-crystalline Au films. Tests show that our SERS substrates have the potential of detecting urea and 1,10-phenantroline adulterants in milk and water, respectively, at 0.01 ppm (or lower) concentrations.

Stretchable interconnections for flexible electronic systems.

PubMed

Jianhui, Lin; Bing, Yan; Xiaoming, Wu; Tianling, Ren; Litian, Liu

2009-01-01

Sensors, actuators and integrated circuits (IC) can be encapsulated together on an elastic substrate, which makes a flexible electronic system. In this system, electrical interconnections that can sustain large and reversible stretching are in great need. This paper is devoted to the fabrication of highly stretchable metal interconnections. Transfer printing technology is utilized, which mainly involves the transfer of 100-nm-thick gold ribbons from silicon wafers to pre-stretched elastic substrates. After the elastic substrates relax from the pre-strain, the gold ribbons buckle and form wavy geometries. These wavy geometries change in shapes to accommodate the applied strain and can be reversely stretched without cracks or fractures occurring, which will greatly raise the stretchability of the gold ribbons. As an application example, some of these wavy ribbons can accommodate high levels of stretching (up to 100%) and bending (with curvature radius down to 1.20 mm). Moreover, the efficiency and reliability of the transfer, especially for slender ribbons, have been increased due to the improvement of the technology. All the characteristics above will permit making stretchable gold conductors as interconnections for flexible electronic systems such as implantable medical systems and smart clothes.

Threefold growth efficiency improvement of silica nanosprings by using silica nanosprings as a substrate

NASA Astrophysics Data System (ADS)

Corti, Giancarlo; Brown, Justin; Rajabi, Negar; McIlroy, D. N.

2018-03-01

The growth efficiency of one-dimension (1D) nanostructures via the vapor-liquid-solid process is commonly attributed to parameters such as precursor vapor pressure, substrate temperature, and the choice of the catalyst. The work presented herein is an investigation of the use of silica nanosprings (SNs) as a 3D substrate for improving the growth efficiency of SN themselves. SNs are a 1D nanomaterial that form a nonwoven structure with optimal geometric characteristics and surface properties that mitigate collisions between growing nanosprings and ripening of the gold catalyst, which should improve SN yield. Nanospring growth, for an eight hour period, on an SN coated surface relative to an equivalent flat substrate increased from ≈25 mgh-1 to ≈80 mgh-1, respectively. All things being equal, by splitting the typical amount of catalyst, in this case gold, between the first and second growth, the double growth procedure produced more than three times more nanosprings than the equivalent single growth of a SN. In addition, using an SN as a substrate increased the sustained growth condition from four to eight hours, and thus increased by a factor of ten the gravimetric yield of SNs relative to the mass of gold used.

A Mechanistic Investigation of the Gold(III)-Catalyzed Hydrofurylation of C-C Multiple Bonds.

PubMed

Hossein Bagi, Amin; Khaledi, Yousef; Ghari, Hossein; Arndt, Sebastian; Hashmi, A Stephen K; Yates, Brian F; Ariafard, Alireza

2016-11-09

The gold-catalyzed direct functionalization of aromatic C-H bonds has attracted interest for constructing organic compounds which have application in pharmaceuticals, agrochemicals, and other important fields. In the literature, two major mechanisms have been proposed for these catalytic reactions: inner-sphere syn-addition and outer-sphere anti-addition (Friedel-Crafts-type mechanism). In this article, the AuCl 3 -catalyzed hydrofurylation of allenyl ketone, vinyl ketone, ketone, and alcohol substrates is investigated with the aid of density functional theory calculations, and it is found that the corresponding functionalizations are best rationalized in terms of a novel mechanism called "concerted electrophilic ipso-substitution" (CEIS) in which the gold(III)-furyl σ-bond produced by furan auration acts as a nucleophile and attacks the protonated substrate via an outer-sphere mechanism. This unprecedented mechanism needs to be considered as an alternative plausible pathway for gold(III)-catalyzed arene functionalization reactions in future studies.

A nanoforest structure for practical surface-enhanced Raman scattering substrates

NASA Astrophysics Data System (ADS)

Seol, Myeong-Lok; Choi, Sung-Jin; Baek, David J.; Park, Tae Jung; Ahn, Jae-Hyuk; Lee, Sang Yup; Choi, Yang-Kyu

2012-03-01

A nanoforest structure for surface-enhanced Raman scattering (SERS) active substrates is fabricated and analyzed. The detailed morphology of the resulting structure can be easily controlled by modifying the process parameters such as initial gold layer thickness and etching time. The applicability of the nanoforest substrate as a label-free SERS immunosensor is demonstrated using influenza A virus subtype H1N1. Selective binding of the H1N1 surface antigen and the anti-H1 antibody is directly detected by the SERS signal differences. Simple fabrication and high throughput with strong in-plane hot-spots imply that the nanoforest structure can be a practical sensing component of a chip-based SERS sensing system.

Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

NASA Technical Reports Server (NTRS)

Porter, Marc D. (Inventor); Weisshaar, Duane E. (Inventor)

1998-01-01

An electrochemical method for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS--, therein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH.sub.3 or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage.

Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

DOEpatents

Porter, Marc D.; Weisshaar, Duane E.

1998-10-27

An electrochemical method for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS--, therein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH.sub.3 or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage.

Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

DOEpatents

Porter, Marc D.; Weisshaar, Duane E.

1997-06-03

An electrochemical method for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS.sup.-, wherein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH.sub.3 or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage.

Metallic glass as a temperature sensor during ion plating

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1985-01-01

The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

Metallic glass as a temperature sensor during ion plating

NASA Technical Reports Server (NTRS)

Miyoshi, K.; Spalvins, T.; Buckley, D. H.

1984-01-01

The temperature of the interface and/or a superficial layer of a substrate during ion plating was investigated using a metallic glass of the composition Fe67Co18B14Si1 as the substrate and as the temperature sensor. Transmission electron microscopy and diffraction studies determined the microstructure of the ion-plated gold film and the substrate. Results indicate that crystallization occurs not only in the film, but also in the substrate. The grain size of crystals formed during ion plating was 6 to 60 nm in the gold film and 8 to 100 nm in the substrate at a depth of 10 to 15 micrometers from the ion-plated interface. The temperature rise of the substrate during ion plating was approximately 500 C. Discontinuous changes in metallurgical microstructure, and physical, chemical, and mechanical properties during the amorphous to crystalline transition in metallic glasses make metallic glasses extremely useful materials for temperature sensor applications in coating processes.

Remotely adjustable check-valves with an electrochemical release mechanism for implantable biomedical microsystems.

PubMed

Pan, Tingrui; Baldi, Antonio; Ziaie, Babak

2007-06-01

In this paper, we present two remotely adjustable check-valves with an electrochemical release mechanism for implantable biomedical microsystems. These valves allow one to vary the opening pressure set-point and flow resistance over a period of time. The first design consists of a micromachined check-valve array using a SU-8 polymer structural layer deposited on the top of a gold sacrificial layer. The second design is based on a variable length cantilever beam structure with a gold sacrificial layer. The adjustable cantilever-beam structure is fabricated by gold thermo-compression bond of a thin silicon wafer over a glass substrate. In both designs, the evaporated gold can be electrochemically dissolved using a constant DC current via a telemetry link. In the first design the dissolution simply opens up individual outlets, while in the second design, gold anchors are sequentially dissolved hence increasing the effective length of the cantilever beam (reducing the opening pressure). A current density of 35 mA/cm(2) is used to dissolve the gold sacrificial layers. Both gravity and syringe-pump driven flow are used to characterize the valve performance. A multi-stage fluidic performance (e.g. flow resistance and opening pressure) is clearly demonstrated.

Superhydrophobic SERS substrates based on silicon hierarchical nanostructures

NASA Astrophysics Data System (ADS)

Chen, Xuexian; Wen, Jinxiu; Zhou, Jianhua; Zheng, Zebo; An, Di; Wang, Hao; Xie, Weiguang; Zhan, Runze; Xu, Ningsheng; Chen, Jun; She, Juncong; Chen, Huanjun; Deng, Shaozhi

2018-02-01

Silicon nanostructures have been cultivated as promising surface enhanced Raman scattering (SERS) substrates in terms of their low-loss optical resonance modes, facile functionalization, and compatibility with today’s state-of-the-art CMOS techniques. However, unlike their plasmonic counterparts, the electromagnetic field enhancements induced by silicon nanostructures are relatively small, which restrict their SERS sensing limit to around 10-7 M. To tackle this problem, we propose here a strategy for improving the SERS performance of silicon nanostructures by constructing silicon hierarchical nanostructures with a superhydrophobic surface. The hierarchical nanostructures are binary structures consisted of silicon nanowires (NWs) grown on micropyramids (MPs). After being modified with perfluorooctyltriethoxysilane (PFOT), the nanostructure surface shows a stable superhydrophobicity with a high contact angle of ˜160°. The substrate can allow for concentrating diluted analyte solutions into a specific area during the evaporation of the liquid droplet, whereby the analytes are aggregated into a small volume and can be easily detected by the silicon nanostructure SERS substrate. The analyte molecules (methylene blue: MB) enriched from an aqueous solution lower than 10-8 M can be readily detected. Such a detection limit is ˜100-fold lower than the conventional SERS substrates made of silicon nanostructures. Additionally, the detection limit can be further improved by functionalizing gold nanoparticles onto silicon hierarchical nanostructures, whereby the superhydrophobic characteristics and plasmonic field enhancements can be combined synergistically to give a detection limit down to ˜10-11 M. A gold nanoparticle-functionalized superhydrophobic substrate was employed to detect the spiked melamine in liquid milk. The results showed that the detection limit can be as low as 10-5 M, highlighting the potential of the proposed superhydrophobic SERS substrate in practical food safety inspection applications.

Selective Binding, Self-Assembly and Nanopatterning of the Creutz-Taube Ion on Surfaces

PubMed Central

Wang, Yuliang; Lieberman, Marya; Hang, Qingling; Bernstein, Gary

2009-01-01

The surface attachment properties of the Creutz-Taube ion, i.e., [(NH3)5Ru(pyrazine)Ru(NH3)5]5+, on both hydrophilic and hydrophobic types of surfaces were investigated using X-ray photoelectron spectroscopy (XPS). The results indicated that the Creutz-Taube ions only bound to hydrophilic surfaces, such as SiO2 and –OH terminated organic SAMs on gold substrates. No attachment of the ions on hydrophobic surfaces such as –CH3 terminated organic SAMs and poly(methylmethacrylate) (PMMA) thin films covered gold or SiO2 substrates was observed. Further ellipsometric, atomic force microscopy (AFM) and time-dependent XPS studies suggested that the attached cations could form an inorganic analog of the self-assembled monolayer on SiO2 substrate with a “lying-down” orientation. The strong electrostatic interaction between the highly charged cations and the anionic SiO2 surface was believed to account for these observations. Based on its selective binding property, patterning of wide (∼200 nm) and narrow (∼35 nm) lines of the Creutz-Taube ions on SiO2 surface were demonstrated through PMMA electron resist masks written by electron beam lithography (EBL). PMID:19333420

High Temperature Pt/Alumina Co-Fired System for 500 C Electronic Packaging Applications

NASA Technical Reports Server (NTRS)

Chen, Liang-Yu; Neudeck, Philip G.; Spry, David J.; Beheim, Glenn M.; Hunter, Gary W.

2015-01-01

Gold thick-film metallization and 96 alumina substrate based prototype packaging system developed for 500C SiC electronics and sensors is briefly reviewed, the needs of improvement are discussed. A high temperature co-fired alumina material system based packaging system composed of 32-pin chip-level package and printed circuit board is discussed for packaging 500C SiC electronics and sensors.

Gold Nanoparticles on Functionalized Silicon Substrate under Coulomb Blockade Regime: An Experimental and Theoretical Investigation.

PubMed

Pluchery, Olivier; Caillard, Louis; Dollfus, Philippe; Chabal, Yves J

2018-01-18

Single charge electronics offer a way for disruptive technology in nanoelectronics. Coulomb blockade is a realistic way for controlling the electric current through a device with the accuracy of one electron. In such devices the current exhibits a step-like increase upon bias which reflects the discrete nature of the fundamental charge. We have assembled a double tunnel junction on an oxide-free silicon substrate that exhibits Coulomb staircase characteristics using gold nanoparticles (AuNPs) as Coulomb islands. The first tunnel junction is an insulating layer made of a grafted organic monolayer (GOM) developed for this purpose. The GOM also serves for attaching AuNPs covalently. The second tunnel junction is made by the tip of an STM. We show that this device exhibits reproducible Coulomb blockade I-V curves at 40 K in vacuum. We also show that depending on the doping of the silicon substrate, the whole Coulomb staircase can be adjusted. We have developed a simulation approach based on the orthodox theory that was completed by calculating the bias dependent tunnel barriers and by including an accurate calculation of the band bending. This model accounts for the experimental data and the doping dependence of Coulomb oscillations. This study opens new perspectives toward designing new kind of single electron transistors (SET) based on this dependence of the Coulomb staircase with the charge carrier concentration.

Self-assembly of large-scale crack-free gold nanoparticle films using a ‘drain-to-deposit’ strategy

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

Yang, Guang; Hallinan, Daniel T.

2016-04-26

Gold nanoparticles are widely studied due to the ease of controlled synthesis, facile surface modification, and interesting physical properties. However, a technique for depositing large-area, crack-free monolayers on solid substrates is lacking. Herein is presented a method for accomplishing this. Spherical gold nanoparticles were synthesized as an aqueous dispersion. Assembly into monolayers and ligand exchange occurred simultaneously at an organic/aqueous interface. Then the monolayer film was deposited onto arbitrary solid substrates by slowly pumping out the lower, aqueous phase. This allowed the monolayer film (and liquid–liquid interface) to descend without significant disturbance, eventually reaching substrates contained in the aqueous phase.more » The resulting macroscopic quality of the films was found to be superior to films transferred by Langmuir techniques. The surface plasmon resonance and Raman enhancement of the films were evaluated and found to be uniform across the surface of each film.« less

Microfluidic setup for on-line SERS monitoring using laser induced nanoparticle spots as SERS active substrate.

PubMed

Buja, Oana-M; Gordan, Ovidiu D; Leopold, Nicolae; Morschhauser, Andreas; Nestler, Jörg; Zahn, Dietrich R T

2017-01-01

A microfluidic setup which enables on-line monitoring of residues of malachite green (MG) using surface-enhanced Raman scattering (SERS) is reported. The SERS active substrate was prepared via laser induced synthesis of silver or gold nanoparticles spot on the bottom of a 200 μm inner dimension glass capillary, by focusing the laser beam during a continuous flow of a mixture of silver nitrate or gold chloride and sodium citrate. The described microfluidic setup enables within a few minutes the monitoring of several processes: the synthesis of the SERS active spot, MG adsorption to the metal surface, detection of the analyte when saturation of the SERS signal is reached, and finally, the desorption of MG from the spot. Moreover, after MG complete desorption, the regeneration of the SERS active spot was achieved. The detection of MG was possible down to 10 -7 M concentration with a good reproducibility when using silver or gold spots as SERS substrate.

A versatile SERS-based immunoassay for immunoglobulin detection using antigen-coated gold nanoparticles and malachite green-conjugated protein A/G

USDA-ARS?s Scientific Manuscript database

A surface enhanced Raman scattering (SERS) immunoassay for antibody detection in serum is described in the present work. The developed assay is conducted in solution and utilizes Au nanoparticles coated with the envelope (E) protein of West Nile Virus (WNV) as the SERS-active substrate and malachite...

YBCO High-Temperature Superconducting Filters on M-Plane Sapphire Substrates

NASA Technical Reports Server (NTRS)

Sabataitis, J. C.; Mueller, C. H.; Miranda, F. A.; Warner, J.; Bhasin, K. B.

1996-01-01

Since the discovery of High Temperature Superconductors (HTS) in 1986, microwave circuits have been demonstrated using HTS films on various substrates. These HTS-based circuits have proven to operate with less power loss than their metallic film counterparts at 77 K. This translates into smaller and lighter microwave circuits for space communication systems such as multiplexer filter banks. High quality HTS films have conventionally been deposited on lanthanum aluminate (LaAlO3) substrates. However, LaAlO3 has a relative dielectric constant (epsilon(sub r)) of 24. With a epsilon(sub r) approx. 9.4-11.6, sapphire (Al2O3) would be a preferable substrate for the fabrication of HTS-based components since the lower dielectric constant would permit wider microstrip lines to be used in filter design, since the lower dielectric constant would permit wider microstrip lines to be used for a given characteristic impedance (Z(sub 0)), thus lowering the insertion losses and increasing the power handling capabilities of the devices. We report on the fabrication and characterization of YBa2Cu3O(7-delta) (YBCO) on M-plane sapphire bandpass filters at 4.0 GHz. For a YBCO 'hairpin' filter, a minimum insertion loss of 0.5 dB was measured at 77 K as compared with 1.4 dB for its gold counterpart. In an 'edge-coupled' configuration, the insertion loss went down from 0.9 dB for the gold film to 0.8 dB for the YBCO film at the same temperature.

Photothermal effect of gold nanostars inkjet-printed on coated paper substrate under near-infrared irradiation

NASA Astrophysics Data System (ADS)

Borzenkov, Mykola; Chirico, Giuseppe; Collini, Maddalena; Määttänen, Anni; Ihalainen, Petri; Cabrini, Elisa; Dacarro, Giacomo; Pallavicini, Piersandro

2016-04-01

The research and development of personalized medical treatments is increasing steadily fostered by its large societal impact. The ability of non-spherical gold nanoparticles to locally and efficiently release heat when irradiated in Near Infrared (NIR) wavelength region is a promising tool for photothermal medical therapies. In the present work, stable inks containing PEGylated gold nanostars (GNS) were obtained and inkjet-printed on a pigment coated paper substrate. Significant photothermal effect of the printed patterns was observed under Near Infrared (NIR) excitation of the Localized Surface Plasmon Resonance (LSPR) of the GNS. These preliminary results support, in perspective, the application of printed GNS patterns for thermal medical treatments either by direct localized heating, or by temperature triggered drug release.

Effect of mechanical and electrical stimuli in conductive atomic force microscopy with noble metal-coated tips

NASA Astrophysics Data System (ADS)

Zade, Vishal; Kang, Hung-Sen; Lee, Min Hwan

2018-01-01

Conductive atomic force microscopy has been widely employed to study the localized electrical properties of a wide range of substrates in non-vacuum conditions by the use of noble metal-coated tips. However, quantitative characterization of the electrical properties was often precluded by unpredictable changes in the tip apex morphology, and/or electronic transport characteristics of undesired oxide overcoats on the tip. In this paper, the impact of mechanical and electrical stimuli on the apex geometry of gold coated tips and electrical conduction properties at the tip-substrate contact is discussed by choosing gold and highly ordered pyrolytic graphite as the representative tip and substrate materials, respectively.

Molecular self-assembly for biological investigations and nanoscale lithography

NASA Astrophysics Data System (ADS)

Cheunkar, Sarawut

Small, diffusible molecules when recognized by their binding partners, such as proteins and antibodies, trigger enzymatic activity, cell communication, and immune response. Progress in analytical methods enabling detection, characterization, and visualization of biological dynamics at the molecular level will advance our exploration of complex biological systems. In this dissertation, analytical platforms were fabricated to capture membrane-associated receptors, which are essential proteins in cell signaling pathways. The neurotransmitter serotonin and its biological precursor were immobilized on gold substrates coated with self-assembled monolayers (SAMs) of oligo(ethylene glycol)alkanethiols and their reactive derivatives. The SAM-coated substrates present the biologically selective affinity of immobilized molecules to target native membrane-associated receptors. These substrates were also tested for biospecificity using antibodies. In addition, small-molecule-functionalized platforms, expressing neurotransmitter pharmacophores, were employed to examine kinetic interactions between G-protein-coupled receptors and their associated neurotransmitters. The binding interactions were monitored using a quartz crystal microbalance equipped with liquid-flow injection. The interaction kinetics of G-protein-coupled serotonin 1A receptor and 5-hydroxytyptophan-functionalized surfaces were studied in a real-time, label-free environment. Key binding parameters, such as equilibrium dissociation constants, binding rate constants, and dissociative half-life, were extracted. These parameters are critical for understanding and comparing biomolecular interactions in modern biomedical research. By integrating self-assembly, surface functionalization, and nanofabrication, small-molecule microarrays were created for high-throughput screening. A hybrid soft-lithography, called microcontact insertion printing, was used to pattern small molecules at the dilute scales necessary for highly selective biorecognition. By carefully tuning the polar surface energy of polymeric stamps, problems associated with patterning hydrophilic tether molecules inserted into hydrophilic preformed SAMs are surmounted. The patterned substrates presenting neurotransmitter precursors selectively capture membrane-associated receptors. These advances provide new avenues for fabricating small-molecule arrays. Furthermore, a novel strategy based on a conventional microcontact printing, called chemical lift-off lithography, was invented to overcome the micrometer-scale resolution limits of molecular ink diffusion in soft lithography. Self-assembled monolayers of hydroxyl-terminated alkanethiols, preformed on gold substrates, were selectively removed by oxygen-plasma-treated polymeric stamps in a subtractive stamping process with high pattern fidelity. The covalent interactions formed at the stamp-substrate interface are believed to be responsible for removing not only alkanethiol molecules but also a monolayer of gold atoms from the substrates. A variety of high-resolution patterned features were fabricated, and stamps were cleaned and reused many times without feature deterioration. The remaining SAMs acted as resists for etching exposed gold features. Monolayer backfilling into lifted-off areas enabled patterned protein capture, and 40-nanometer chemical patterns were achieved.

Lateral and axial cutting efficiency of instruments manufactured with conventional nickel-titanium and novel gold metallurgy.

PubMed

Vasconcelos, R A; Arias, A; Peters, O A

2018-05-01

To isolate the effect of metallurgy in lateral and axial cutting efficacy against plastic and bovine dentine substrates by comparing two rotary systems with identical design but manufactured with either conventional nickel-titanium or heat-treated gold alloy. A total of 258 ProTaper Universal (PTU) and ProTaper Gold (PTG) Shaping instruments were used. Bending behaviour was assessed to determine the appropriate displacement associated with a 2 N force in lateral cutting. Ten instruments of each type were used in lateral action for 60 s against bovine dentine or plastic substrates four consecutive times producing four notches in each specimen. Ten further instruments of each type were used in on axial action in four standardized simulated root canals fabricated from 4-mm thick plastic or dentine discs. Both tests were performed at 300 rpm in a computer-controlled testing platform. Notch area and torsional load were compared with Student's t-tests. Repeated measures ANOVA was used to compare cutting efficiency across the four different time-points. Pearson correlation coefficients between substrates were also determined. For lateral action, all three PTG instruments cut significantly more effectively (P < 0.05) than PTU on the plastic substrate. S1 and S2 PTG cut significantly more after 120 and 180 s (P < 0.05) on bovine dentine substrate. For axial action, S1 and S2 PTG were significantly more efficient in cutting at 180 s on plastic and 120 s on bovine dentine (P < 0.05). Instruments made from heat-treated nickel-titanium gold alloy had equal or greater cutting efficiency when compared to those made from conventional nickel-titanium. © 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.

Friction fluctuations of gold nanoparticles in the superlubric regime

NASA Astrophysics Data System (ADS)

Dietzel, Dirk; de Wijn, Astrid S.; Vorholzer, Matthias; Schirmeisen, Andre

2018-04-01

Superlubricity, or alternatively termed structural (super)lubrictiy, is a concept where ultra-low friction is expected at the interface between sliding surfaces if these surfaces are incommensurate and thus unable to interlock. In this work, we now report on sudden, reversible, friction changes that have been observed during AFM-based nanomanipulation experiments of gold nanoparticles sliding on highly oriented pyrolythic graphite. These effects can be explained by rotations of the gold nanoparticles within the concept of structural superlubricity, where the occurrence of ultra-low friction can depend extremely sensitively on the relative orientation between the slider and the substrate. From our theoretical simulations it will become apparent how even miniscule magnitudes of rotation are compatible to the observed effects and how size and shape of the particles can influence the dependence between friction and relative orientation.

Preparation and Raman enhancement properties of gold nanostars

NASA Astrophysics Data System (ADS)

Shan, Feng; Zhang, Tong

2018-03-01

Gold nanostars (GNSs) have a series of sharp tips structures, which will produce strong hot spots and have great application potential in Raman enhancement. In this paper, muti-tip GNSs have been prepared experimentally, and the control techniques of their tip and size have been mastered. For the first time, a fast and efficient self-assembly technique without additives has been developed, and a series of Surface Enhanced Raman Scattering (SERS) substrates have been successfully prepared by using this technique. The effect of different GNSs density of substrates on SERS signal is further studied experimentally. The results show that the SERS signal is closely related to the density of particles in the substrate. The higher density of GNSs in the substrate, the more hot spots covered by the incident light plate, and the greater contribution to the SERS signal.

Gold Nanoparticle Labels and Heterogeneous Immunoassays: The Case for the Inverted Substrate.

PubMed

Crawford, Alexis C; Young, Colin C; Porter, Marc D

2018-06-15

This paper examines how the difference in the spatial orientation of the capture substrate influences the analytical sensitivity and limits of detection for immunoassays that use gold nanoparticle labels (AuNPs) and rely on diffusion in quiet solution in the antigen capture and labeling steps. Ideally, the accumulation of both reactants should follow a dependence governed by the rate in which diffusion delivers reactants to the capture surface. In other words, the accumulation of reactants should increase with the square root of the incubation time, i.e., t1/2. The work herein shows, however, that this expectation is only obeyed when the capture substrate is oriented to direct the gravity-induced sedimentation of the AuNP labels away from the substrate. Using an assay for human IgG, the results show that circumventing the sedimentation of the gold nanoparticle labels by substrate inversion enables the dependence of the labeling step on diffusion, reduces nonspecific label adsorption, and improves the estimated detection limit by ~30×. High-density maps of the signal across the two types of substrates also demonstrate that inversion in the labeling step results in a more uniform distribution of AuNP labels across the surface, which translates to a greater measurement reproducibility. These results, which are supported by model simulations via the Mason-Weaver sedimentation-diffusion equation, and their potential implications when using other nanoparticle labels and related materials in diagnostic tests and other applications, are briefly discussed.

Synthesis of icosahedral gold nanocrystals: a thermal process strategy.

PubMed

Zhou, Min; Chen, Shenhao; Zhao, Shiyong

2006-03-16

We demonstrate a one-step thermal process route to the synthesis of icosahedral gold nanocrystals. By regulating the concentrations of poly(vinyl pyrrolidone) (PVP) and HAuCl4 or changing the temperature, we can readily access the shapes of icosahedral nanocrystals with good uniformity. These gold nanostructures, with unique geometrical shapes, might find use in areas that include photonics, optoelectronics, and optical sensing. We also observed that these gold nanocrystals have a strong tendency to be immobilized spontaneously on the glass substrate.

Gold leaf counter electrodes for dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Shimada, Kazuhiro; Toyoda, Takeshi

2018-03-01

In this study, a gold leaf 100 nm thin film is used as the counter electrode in dye-sensitized solar cells. The traditional method of hammering gold foil to obtain a thin gold leaf, which requires only small amounts of gold, was employed. The gold leaf was then attached to the substrate using an adhesive to produce the gold electrode. The proposed approach for fabricating counter electrodes is demonstrated to be facile and cost-effective, as opposed to existing techniques. Compared with electrodes prepared with gold foil and sputtered gold, the gold leaf counter electrode demonstrates higher catalytic activity with a cobalt-complex electrolyte and higher cell efficiency. The origin of the improved performance was investigated by surface morphology examination (scanning electron microscopy), various electrochemical analyses (cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy), and crystalline analysis (X-ray diffractometry).

UV-VIS extinction spectra of gold particle coated by oligonucleotide shell

NASA Astrophysics Data System (ADS)

Bogatyrev, Vladimir A.; Vrublevsky, Stanislav A.; Trachuk, Lyubov A.; Khlebtsov, Nikolai G.

2005-06-01

We describe synthesis process of an oligonucleotide-functionalized colloidal gold marker CG-l5-T28, its optical properties and interaction with poly(A) in solution and on a solid-phase substrate. The marker is a complex of 15 nm diameter colloidal gold nanoparticles with covalently attached 5'-thiolated 28-base oligothymidine macromolecules. A positive hybridization reaction of the marker with poly(A) is observed by solid-phase analysis on hanging a spot color (from red to blue ) or on appearance of a red dye in dot-blot test as compared to control experiments with poly(U) target. The principles of spectrophotometric monitoring all stages of the marker preparation and application of spectrophotometry to detection of the polynucleotide hybridization in vitro are described. Experimental data were compared with theoretical calculations based on Mie theory for 2-layer model of gold core in polymeric shell with imaginary part of refractive index that typical for the real absorption spectra of NA. To explain the aggregation of CG-15-T28 caused by interaction with poly(A) in solution, we suggest a new model differing from a standard model of cross-linker binding.

Christmas-tree Derived Amplification Immuno-strategy for Sensitive Visual Detection of Vibrio parahaemolyticus Based on Gold Label Silver Stain Technology.

PubMed

Song, Xinxin; Wu, Yanjie; Wu, Lin; Hu, Yufang; Li, Wenrou; Guo, Zhiyong; Su, Xiurong; Jiang, Xiaohua

2017-01-01

A developed Christmas-tree derived immunosensor based on a gold label silver stain (GLSS) technique was fabricated for a highly sensitive analysis of Vibrio parahaemolyticu (VP). In this strategy, captured VP antibody (cAb) was immobilized on a solid substrate; then, the VPs were sequentially tagged with a signal probe by incubating the assay with a detection VP antibody (dAb) conjugated gold nanoparticles (AuNPs)-labeled graphite-like carbon nitride (g-C 3 N 4 ). Finally, the attached signal probe could harvest a visible signal by the silver meal deposition, and then followed by homebrew Matlab 6.0 as a grey value acquisition. In addition, the overall design of the biosensor was established in abundant AuNPs and g-C 3 N 4 with a two-dimensional structure, affording a bulb-decorated Christmas-tree model. Moreover, with the optimized conditions, the detection limit of the as-proposed biosensor is as low as 10 2 CFU (Colony-Forming Units) mL -1 , exhibiting an increase of two orders of magnitude compared with the traditional immune-gold method. Additionally, the developed visible immunosensor was also successfully applied to the analysis of complicated samples.

Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems.

PubMed

Tong, Yujin; Zhao, Yanbao; Li, Na; Ma, Yunsheng; Osawa, Masatoshi; Davies, Paul B; Ye, Shen

2010-07-21

In this paper, the results of the modeling calculations carried out for predicting the interference effects expected in the sum frequency generation (SFG) spectra of a specific thin-layer system, described in the accompanying paper, are tested by comparing them with the experimental spectra obtained for a real thin-layer film comprising an organic monolayer/variable thickness dielectric layer/gold substrate. In this system, two contributions to the SFG spectra arise, a resonant contribution from the organic film and a nonresonant contribution from the gold substrate. The modeling calculations are in excellent agreement with the experimental spectra over a wide range of thicknesses and for different polarization combinations. The introduction of another resonant monolayer adjacent to the gold substrate and with the molecules having a reverse orientation has a significant affect on the spectral shapes which is predicted. If a dielectric substrate such as CaF(2) is used instead of a gold substrate, only the spectral intensities vary with the film thickness but not the spectral shapes. The counterpropagating beam geometry will change both the thickness dependent spectral shapes and the intensity of different vibrational modes in comparison with a copropagating geometry. The influences of these experimental factors, i.e., the molecular orientational structure in the thin film, the nature of the substrate, and the selected incident beam geometry, on the experimental SFG spectra are quantitatively predicted by the calculations. The thickness effects on the signals from a SFG active monolayer contained in a thin liquid-layer cell of the type frequently used for in situ electrochemical measurements is also discussed. The modeling calculation is also valid for application to other thin-film systems comprising more than two resonant SFG active interfaces by appropriate choice of optical geometries and relevant optical properties.

Nonlinear optical behavior of DNA-functionalized gold nanoparticles

NASA Astrophysics Data System (ADS)

Kulyk, B.; Krupka, O.; Smokal, V.; Figà, V.; Czaplicki, R.; Sahraoui, B.

2018-03-01

The third-order nonlinear optical properties of gold nanoparticles embedded in the DNA-based composites were investigated by means of the third harmonic generation. With this purpose, the thin films comprising DNA-based complexes and Au nanoparticles were spin-deposited on glass substrate and their optical and nonlinear optical features were studied using the Maker-fringe technique at a laser fundamental wavelength of 1064 nm. The values of the third-order susceptibility χ (3)(- 3ω; ω, ω, ω) of the composite films based on DNA complex doped with 5 wt% of N-ethyl-N-(2-hydroxyethyl)-4-(4-nitrophenylazo)aniline were found to be significantly higher than those for pure composite films. Meanwhile, the presence of Au nanoparticles noticeable decreases the third-order nonlinear response of DNA-based composite mainly due to the enhanced absorption and scattering of laser and generated beam, respectively.

Single cell adhesion force measurement for cell viability identification using an AFM cantilever-based micro putter

NASA Astrophysics Data System (ADS)

Shen, Yajing; Nakajima, Masahiro; Kojima, Seiji; Homma, Michio; Kojima, Masaru; Fukuda, Toshio

2011-11-01

Fast and sensitive cell viability identification is a key point for single cell analysis. To address this issue, this paper reports a novel single cell viability identification method based on the measurement of single cell shear adhesion force using an atomic force microscopy (AFM) cantilever-based micro putter. Viable and nonviable yeast cells are prepared and put onto three kinds of substrate surfaces, i.e. tungsten probe, gold and ITO substrate surfaces. A micro putter is fabricated from the AFM cantilever by focused ion beam etching technique. The spring constant of the micro putter is calibrated using the nanomanipulation approach. The shear adhesion force between the single viable or nonviable cell and each substrate is measured using the micro putter based on the nanorobotic manipulation system inside an environmental scanning electron microscope. The adhesion force is calculated based on the deflection of the micro putter beam. The results show that the adhesion force of the viable cell to the substrate is much larger than that of the nonviable cell. This identification method is label free, fast, sensitive and can give quantitative results at the single cell level.

Optical properties of chitin: surface-enhanced Raman scattering substrates based on antireflection structures on cicada wings

NASA Astrophysics Data System (ADS)

Stoddart, P. R.; Cadusch, P. J.; Boyce, T. M.; Erasmus, R. M.; Comins, J. D.

2006-02-01

The transparent wings of some cicada species present ordered arrays of papillary structures with a spacing of approximately 200 nm. These structures serve an antireflection function, with optical transmission peaking at a value of approximately 98% and rising above 90% over a broad band from 450 to 2500 nm. The dimensions of the papillae are comparable to the roughness scale of surface-enhanced Raman scattering (SERS) substrates. SERS measurements performed on silver- and gold-coated wings display enhancement factors of approximately 106 with no apparent background contribution from the wing.

Electrochemical method of controlling thiolate coverage on a conductive substrate such as gold

DOEpatents

Porter, M.D.; Weisshaar, D.E.

1998-10-27

An electrochemical method is described for forming a partial monomolecular layer of a predetermined extent of coverage of a thiolate of the formula, XRS-, therein R can be a linear or branched chain hydrocarbon or an aromatic or the like and X can be any compatible end group, e.g., OH, COOH, CH{sub 3} or the like, upon a substrate such as gold, which involves applying in an electrochemical system a constant voltage preselected to yield the desired predetermined extent of coverage. 13 figs.

Subwavelength Gold Grating as Polarizers Integrated with InP-Based InGaAs Sensors.

PubMed

Wang, Rui; Li, Tao; Shao, Xiumei; Li, Xue; Huang, Xiaqi; Shao, Jinhai; Chen, Yifang; Gong, Haimei

2015-07-08

There are currently growing needs for polarimetric imaging in infrared wavelengths for broad applications in bioscience, communications and agriculture, etc. Subwavelength metallic gratings are capable of separating transverse magnetic (TM) mode from transverse electric (TE) mode to form polarized light, offering a reliable approach for the detection in polarization way. This work aims to design and fabricate subwavelength gold gratings as polarizers for InP-based InGaAs sensors in 1.0-1.6 μm. The polarization capability of gold gratings on InP substrate with pitches in the range of 200-1200 nm (fixed duty cycle of 0.5) has been systematically studied by both theoretical modeling with a finite-difference time-domain (FDTD) simulator and spectral measurements. Gratings with 200 nm lines/space in 100-nm-thick gold have been fabricated by electron beam lithography (EBL). It was found that subwavelength gold gratings directly integrated on InP cannot be applied as good polarizers, because of the existence of SPP modes in the detection wavelengths. An effective solution has been found by sandwiching the Au/InP bilayer using a 200 nm SiO2 layer, leading to significant improvement in both TM transmission and extinction ratio. At 1.35 μm, the improvement factors are 8 and 10, respectively. Therefore, it is concluded that the Au/SiO2/InP trilayer should be a promising candidate of near-infrared polarizers for the InP-based InGaAs sensors.

Surface-enhanced Raman scattering of amorphous TiO2 thin films by gold nanostructures: Revealing first layer effect with thickness variation

NASA Astrophysics Data System (ADS)

Degioanni, S.; Jurdyc, A.-M.; Bessueille, F.; Coulm, J.; Champagnon, B.; Vouagner, D.

2013-12-01

In this paper, amorphous titanium dioxide (TiO2) thin films have been deposited on a commercially available Klarite substrate using the sol-gel process to produce surface-enhanced Raman scattering (SERS). The substrate consists of square arrays of micrometer-sized pyramidal pits in silicon with a gold coating. Several thin TiO2 layers have been deposited on the surface to study the influence of film thickness. Ultimately, we obtained information on SERS of an amorphous TiO2 layer by gold nanostructures, whose range is less than a few nanometers. Mechanisms responsible for the enhancement are the product of concomitant chemical and electromagnetic effects with an important contribution from plasmon-induced charge transfer.

Hydrophenoxylation of internal alkynes catalysed with a heterobimetallic Cu-NHC/Au-NHC system.

PubMed

Lazreg, Faïma; Guidone, Stefano; Gómez-Herrera, Alberto; Nahra, Fady; Cazin, Catherine S J

2017-02-21

A straightforward method for the hydrophenoxylation of internal alkynes, using N-heterocyclic carbene-based copper(i) and gold(i) complexes, is described. The heterobimetallic catalytic system proceeds via dual activation of the substrates to afford the desired vinylether derivatives. This methodology is shown to be highly efficient and tolerates a wide range of substituted phenols and alkynes.

Synthesis, Structure, Stability and Redispersion of Gold-based Nanoparticles

NASA Astrophysics Data System (ADS)

Tiruvalam, Ram Chandra

Nanoscale gold has been shown to possess an intriguing combination of unexpected optical, photochemical and catalytic properties. The ability to control the size, shape, morphology, composition and dispersion of gold-based nanostructures is key to optimizing their performance for nanotechnology applications. The advanced electron microscopy studies described in this thesis analyze three important aspects of gold and gold-palladium alloy nanoparticles: namely, (i) the ability to synthesize gold nanoparticles of controlled size and shape in an aqueous medium; (ii) the colloidal preparation of designer gold-palladium alloys for selective oxidation catalysis; and (iii) the ability to disperse gold as finely and homogeneously as possible on a metal oxide or carbon support. The ability to exploit the nanoscale properties of gold for various engineering applications often depends on our ability to control size and shape of the nanoscale entity by careful manipulation of the synthesis parameters. We have explored an aqueous based synthesis route, using oleylamine as both a reductant and surfactant, for preparing gold nanostructures. By systematically varying synthesis parameters such as oleylamine concentration, reaction temperature, and aging time it is possible to identify processing regimens that generate Au nanostructures having either pseudo-spherical, faceted polyhedral, nanostar or wire shaped morphologies. Furthermore, by quenching the reaction partway through it is possible to create a class of metastable Au-containing structures such as nanocubes, nanoboxes and nanowires. Possible formation mechanisms for these gold based nano-objects are discussed. There is a growing interest in using supported bimetallic AuPd alloy nanoparticles for selective oxidation reactions. In this study, a systematic series of size controlled AuPd bimetallic particles have been prepared by colloidal synthesis methods. Particles having random alloy structures, as well as `designer' particles with Pd-shell/Au-core and Au-shell/Pd-core morphologies, have been prepared and immobilized on both activated carbon and TiO2 supports. These have subsequently been compared as catalysts for the direct production of H2O2 and for benzyl alcohol oxidation in an attempt to elucidate the optimum particle morphology/support combination for both these reactions. Aberration corrected analytical electron microscopy has been used extensively to characterize these sol-immobilized materials. In particular, the STEM -HAADF technique has provided invaluable new (and often unexpected) information on the atomic structure, elemental distribution within particles, and compositional variations between particles for these controlled catalyst preparations. In addition, we have been able to compare their differing thermal stability and sintering behaviors, and to demonstrate that they have quite varying wetting interactions with activated carbon and TiO2 supports. Over the course of their lifetime, many supported metal catalysts exposed to elevated temperatures tend to de-activate by nanoparticle sintering, which decreases the overall exposed metal surface area and the number of active sites available for catalysis. It is sometimes desirable to devise chemical re-dispersion treatments whereby the mean size of the particles is reduced and the catalytic activity regenerated. In this work, the possibility of re-dispersing gold nanoparticles by a simple low temperature methyl iodide (CH3 I) treatment has been investigated. A variety of characterization techniques, including EXAFS, XRD, XPS, UV-DRS and STEM-HAADF imaging has been applied to samples before and after CH3 I treatment, in an attempt to determine the efficacy of the re-dispersion method. It is shown that re-dispersion of Au nanoparticles on activated carbon, graphite, Al2 O3 and TiO2 substrates is possible to varying degrees. A complete re-dispersion of `bulk' gold nanoparticles down to the atomic scale has been achieved on activated carbon and graphite substrates, with the exclusive formation of isolated gold atoms, dimeric species, and sub-nm clusters.

Enhanced detection of thiophenol adsorbed on gold nanoparticles by SFG and DFG nonlinear optical spectroscopy.

PubMed

Pluchery, Olivier; Humbert, Christophe; Valamanesh, Mehrnoush; Lacaze, Emmanuelle; Busson, Bertrand

2009-09-21

Sum frequency generation (SFG) and difference frequency generation (DFG) are applied to study vibrational resonance of the thiophenol molecule adsorbed on two different gold samples. One sample is made of 17 nm gold nanoparticles (AuNPs) fixed on a silicon substrate that has been previously functionalized with a silane monolayer (aminopropyltriethoxysilane, APTES). This sample is fully characterized through visible reflection spectroscopy and AFM. The second sample is a gold monocrystal also covered with thiophenol molecules. From their comparison, an enhancement factor of 21 is deduced for the SFG signal on AuNPs with respect to the Au(111), related to the surface plasmon resonance (SPR). From a combined analysis of the SFG and DFG spectra, we demonstrate that SFG/DFG spectroscopy is able to identify the nature of the substrate where the molecules are adsorbed. This opens new perspectives for this nonlinear spectroscopy by adding to its well-known intrinsic surface specificity, the ability to selectively probe the chemical layer capping the AuNPs.

Recovery of gold from waste electrical and electronic equipment (WEEE) using ammonium persulfate.

PubMed

Alzate, Andrea; López, Maria Esperanza; Serna, Claudia

2016-11-01

This paper presents a novel methodology to recover gold from waste electrical and electronic equipment (WEEE) using ammonium persulfate ((NH 4 ) 2 S 2 O 8 ). Gold was recovered as a fine coating using substrate oxidation without shredding or grinding process. The WEEE sample was characterized giving values of Au: 1.05g/kg, Fe: 86.00g/kg, Ni: 73.64g/kg, Cu: 26.65g/kg. The effect of (NH 4 ) 2 S 2 O 8 concentration (0.22-1.10M), oxygen (0.0-1.4L/min) and L/S ratio (10-30mL/g) on the main responses (substrate oxidation and Au recovery) was investigated implementing response surface methodology with numerical optimization. A quadratic model was developed and quantities greater than 98% of Au were recovered. The findings presented suggest that, optimized quantities of ammonium persulfate in aqueous highly oxygenated media could be used to extract superficial gold from WEEE. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of nanoscale size and medium on metal work function in oleylamine-capped gold nanocrystals

NASA Astrophysics Data System (ADS)

Abdellatif, M. H.; Ghosh, S.; Liakos, I.; Scarpellini, A.; Marras, S.; Diaspro, A.; Salerno, M.

2016-02-01

The work function is an important material property with several applications in photonics and optoelectronics. We aimed to characterize the work function of clusters resulting from gold nanocrystals capped with oleylamine surfactant and drop-casted onto gold substrate. We used scanning Kelvin probe microscopy to investigate the work function, and complemented our study mainly with X-ray diffraction and X-ray photoelectron spectroscopy. The oleylamine works as an electron blocking layer through which the electrical conduction takes place by tunneling effect. The surface potential appears to depend on the size of the clusters, which can be ascribed to their difference in effective work function with the substrate. The charge state of gold clusters is discussed in comparison with theory, and their capacitance is calculated from a semi-analytical equation. The results suggest that at the nanoscale the work function is not an intrinsic property of a material but rather depends on the size and morphology of the clusters, including also effects of the surrounding materials.

Nanoporous Substrate with Mixed Nanoclusters for Surface Enhanced Raman Scattering.

NASA Astrophysics Data System (ADS)

Chang, Sehoon; Ko, Hyunhyub; Singamaneni, Srikanth; Gunawidjaja, Ray; Tsukruk, Vladimir

2009-03-01

Rapid detection of plastic and liquid explosives is an urgent need due to various societal and technological reasons. We employed a novel design of surface enhanced Raman scattering (SERS)-active substrate based on porous alumina membranes decorated with mixed nanoclusters of gold nanorods and nanoparticles. We demonstrated trace level detection of several important explosives such as dinitrotolene (DNT), trinitrotoluene (TNT), and hexamethylenetriperoxidediamine (HMTD) by fast, sensitive, reliable Raman spectroscopic method. We achieved near molecular-level detection (about 15˜ 30 molecules) of DNT and TNT utilizing the SERS substrate. However, trace level detection is challenging due to the lack of common optical signatures (fluorescence, absorption in UV-vis range) or chemical functionality of peroxide-based explosives such as HMTD. To overcome this, we employed photochemical decomposition approach and analyzed chemical fragments using SERS. We suggest that tailored polymer coating, mixed nanoclusters, and laser-induced photocatalytic decomposition are all critical for achieving this unprecedented sensitivity level..

Improved thermal stability of oxide-supported naked gold nanoparticles by ligand-assisted pinning

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

Moreno, C; Divins, N. J.; Gazquez, Jaume

We report a method to improve the thermal stability, up to 900 C, of bare-metal (naked) gold nanoparticles supported on top of SiO{sub 2} and SrTiO{sub 3} substrates via ligand-assisted pinning. This approach leads to monodisperse naked gold nanoparticles without significant sintering after thermal annealing in air at 900 C. The ligand-assisted pinning mechanism is described.

Spontaneous grafting of diazonium salts: chemical mechanism on metallic surfaces.

PubMed

Mesnage, Alice; Lefèvre, Xavier; Jégou, Pascale; Deniau, Guy; Palacin, Serge

2012-08-14

The spontaneous reaction of diazonium salts on various substrates has been widely employed since it consists of a simple immersion of the substrate in the diazonium salt solution. As electrochemical processes involving the same diazonium salts, the spontaneous grafting is assumed to give covalently poly(phenylene)-like bonded films. Resistance to solvents and to ultrasonication is commonly accepted as indirect proof of the existence of a covalent bond. However, the most relevant attempts to demonstrate a metal-C interface bond have been obtained by an XPS investigation of spontaneously grafted films on copper. Similarly, our experiments give evidence of such a bond in spontaneously grafted films on nickel substrates in acetonitrile. In the case of gold substrates, the formation of a spontaneous film was unexpected but reported in the literature in parallel to our observations. Even if no interfacial bond was observed, formation of the films was explained by grafting of aryl cations or radicals on the surface arising from dediazoniation, the film growing later by azo coupling, radical addition, or cationic addition on the grafted phenyl layer. Nevertheless, none of these mechanisms fits our experimental results showing the presence of an Au-N bond. In this work, we present a fine spectroscopic analysis of the coatings obtained on gold and nickel substrates that allow us to propose a chemical structure of such films, in particular, their interface with the substrates. After testing the most probable mechanisms, we have concluded in favor of the involvement of two complementary mechanisms which are the direct reaction of diazonium salts with the gold surface that accounts for the observed Au-N interfacial bonds as well as the formation of aryl cations able to graft on the substrate through Au-C linkages.

Synthesis, characterization and optical properties of an amino-functionalized gold thiolate cluster: Au10(SPh-pNH2)10.

PubMed

Lavenn, Christophe; Albrieux, Florian; Tuel, Alain; Demessence, Aude

2014-03-15

Research interest in ultra small gold thiolate clusters has been rising in recent years for the challenges they offer to bring together properties of nanoscience and well-defined materials from molecular chemistry. Here, a new atomically well-defined Au10 gold nanocluster surrounded by ten 4-aminothiophenolate ligands is reported. Its synthesis followed the similar conditions reported for the elaboration of Au144(SR)60, but because the reactivity of thiophenol ligands is different from alkanethiol derivates, smaller Au10 clusters were formed. Different techniques, such as ESI-MS, elemental analysis, XRD, TGA, XPS and UV-vis-NIR experiments, have been carried out to determine the Au10(SPh-pNH2)10 formula. Photoemission experiment has been done and reveals that the Au10 clusters are weakly luminescent as opposed to the amino-based ultra-small gold clusters. This observation points out that the emission of gold thiolate clusters is highly dependent on both the structure of the gold core and the type of the ligands at the surface. In addition, ultra-small amino-functionalized clusters offer the opportunity for extended work on self-assembling networks or deposition on substrates for nanotechnologies or catalytic applications. Copyright © 2013 Elsevier Inc. All rights reserved.

Probing the effect of charge transfer enhancement in off resonance mode SERS via conjugation of the probe dye between silver nanoparticles and metal substrates.

PubMed

Selvakannan, Pr; Ramanathan, Rajesh; Plowman, Blake J; Sabri, Ylias M; Daima, Hemant K; O'Mullane, Anthony P; Bansal, Vipul; Bhargava, Suresh K

2013-08-21

The charge transfer-mediated surface enhanced Raman scattering (SERS) of crystal violet (CV) molecules that were chemically conjugated between partially polarized silver nanoparticles and optically smooth gold and silver substrates has been studied under off-resonant conditions. Tyrosine molecules were used as a reducing agent to convert silver ions into silver nanoparticles where oxidised tyrosine caps the silver nanoparticle surface with its semiquinone group. This binding through the quinone group facilitates charge transfer and results in partially oxidised silver. This establishes a chemical link between the silver nanoparticles and the CV molecules, where the positively charged central carbon of CV molecules can bind to the terminal carboxylate anion of the oxidised tyrosine molecules. After drop casting Ag nanoparticles bound with CV molecules it was found that the free terminal amine groups tend to bind with the underlying substrates. Significantly, only those CV molecules that were chemically conjugated between the partially polarised silver nanoparticles and the underlying gold or silver substrates were found to show SERS under off-resonant conditions. The importance of partial charge transfer at the nanoparticle/capping agent interface and the resultant conjugation of CV molecules to off resonant SERS effects was confirmed by using gold nanoparticles prepared in a similar manner. In this case the capping agent binds to the nanoparticle through the amine group which does not facilitate charge transfer from the gold nanoparticle and under these conditions SERS enhancement in the sandwich configuration was not observed.

Plasmon-induced artificial photosynthesis

PubMed Central

Ueno, Kosei; Oshikiri, Tomoya; Shi, Xu; Zhong, Yuqing; Misawa, Hiroaki

2015-01-01

We have successfully developed a plasmon-induced artificial photosynthesis system that uses a gold nanoparticle-loaded oxide semiconductor electrode to produce useful chemical energy as hydrogen and ammonia. The most important feature of this system is that both sides of a strontium titanate single-crystal substrate are used without an electrochemical apparatus. Plasmon-induced water splitting occurred even with a minimum chemical bias of 0.23 V owing to the plasmonic effects based on the efficient oxidation of water and the use of platinum as a co-catalyst for reduction. Photocurrent measurements were performed to determine the electron transfer between the gold nanoparticles and the oxide semiconductor. The efficiency of water oxidation was determined through spectroelectrochemical experiments aimed at elucidating the electron density in the gold nanoparticles. A set-up similar to the water-splitting system was used to synthesize ammonia via nitrogen fixation using ruthenium instead of platinum as a co-catalyst. PMID:26052419

Estimating the concentration of gold nanoparticles incorporated on natural rubber membranes using multi-level starlet optimal segmentation

NASA Astrophysics Data System (ADS)

de Siqueira, A. F.; Cabrera, F. C.; Pagamisse, A.; Job, A. E.

2014-12-01

This study consolidates multi-level starlet segmentation (MLSS) and multi-level starlet optimal segmentation (MLSOS) techniques for photomicrograph segmentation, based on starlet wavelet detail levels to separate areas of interest in an input image. Several segmentation levels can be obtained using MLSS; after that, Matthews correlation coefficient is used to choose an optimal segmentation level, giving rise to MLSOS. In this paper, MLSOS is employed to estimate the concentration of gold nanoparticles with diameter around 47 nm, reduced on natural rubber membranes. These samples were used for the construction of SERS/SERRS substrates and in the study of the influence of natural rubber membranes with incorporated gold nanoparticles on the physiology of Leishmania braziliensis. Precision, recall, and accuracy are used to evaluate the segmentation performance, and MLSOS presents an accuracy greater than 88 % for this application.

Nanomaterial strategies for immunodetection

NASA Astrophysics Data System (ADS)

Porter, M. D.; Granger, M. C.; Siperko, L. M.; Lipert, R. J.

2011-06-01

Metallic nanoparticles are playing increasingly important roles in biodiagnostic platforms. This emergence reflects the need to detect disease indicating entities at increasingly lower levels in human and veterinary diagnostics, homeland security, and food and water safety. To establish this perspective, this paper overviews our recent work using surface enhanced Raman scattering for detection of proteins, viruses, and microorganisms in heterogeneous immunoassays. It describes the assay platform, which is comprised of an antibody-modified capture substrate and gold nanoparticle-based label. The latter draws on the ability to reproducibly construct gold nanoparticles modified with a monolayer of an intrinsically strong Raman scatterer that is then coated with a layer of antibodies. This construct, referred to as an extrinsic Raman label, takes advantage of the signal enhancement of scatterers when coated on nanometer-sized gold particles and the antigenic binding specificity of the immobilized antibody layer. Challenges related to nonspecific adsorption, particle stability, and measurement reproducibility are also briefly examined.

[Oxidation of sulfur-containing substrates by aboriginal and experimentally designed microbial communities].

PubMed

Pivovarova, T A; Bulaev, A G; Roshchupko, P V; Belyĭ, A V; Kondrat'eva, T F

2012-01-01

Aboriginal and experimental (constructed of pure microbial cultures) communities of acidophilic chemolithotrophs have been studied. The oxidation of elemental sulfur, sodium thiosulfate, and potassium tetrathionate as sole sources of energy has been monitored. The oxidation rate of the experimental community is higher as compared to the aboriginal community isolated from a flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore. The degree of oxidation of the mentioned S substrates amounts to 17.91, 68.30, and 93.94% for the experimental microbial community and to 10.71, 56.03, and 79.50% for the aboriginal community, respectively. The degree of oxidation of sulfur sulfide forms in the ore flotation concentrate is 59.15% by the aboriginal microbial community and 49.40% by the experimental microbial community. Despite a higher rate of oxidation of S substrates as a sole source of energy by the experimental microbial community, the aboriginal community oxidizes S substrates at a higher rate in the flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore, from which it was isolated. Bacterial-chemical oxidation of the flotation concentrate by the aboriginal microbial community allows for the extraction of an additional 32.3% of gold from sulfide minerals, which is by 5.7% larger compared to the yield obtained by the experimental microbial community.

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.

High Power Attenuator and Termination.

DTIC Science & Technology

sections are configured from a single thin film series resistor comprised of gold and a plurality of shunt resistors formed from a layer of cermet which...underlies the gold film resistor. The cermet shunt resistors extend away from the series resistor to the side edge of the substrate where they

X Ray Mask Of Gold-Carbon Mixture Absorber On BCN Compound Substrate Fabricated By Plasma Processes

NASA Astrophysics Data System (ADS)

Aiyer, Chandrasekhar R.; Itoh, Satoshi; Yamada, Hitomi; Morita, Shinzo; Hattori, Shuzo

1988-06-01

X-ray mask fabrication based on BCN compound membrane and gold containing polymeric carbon ( Au-C ) absorber by totally dry processes is proposed. The Au-C films were depo-sited by plasma polymerization of propylene or styrene monomers and co-evaporation of gold. These films have 2 to 5 times higher etching rate than that of pure gold for 09 RIE, depending on the Au content. The stress in the films could be reduced to 1.9 E 7 N/m2 by annealing. The BCN films were deposited on silicon wafers by rf (13.56 MHz) plasma CVD with diborane, methane and nitrogen as source gases at typical deposition rate of 30 nm/min. The optical (633nm) and X ray (Pd L~) transparencies were nearly 80% for film thickness of 6 um. Patterning of Au-C was achieved by using tungsten as intermediate layer and PMMA electron beam resist. CF4 RIE was used to etch the tungsten layer which in turn acted as mask for the gold carbide 02 RIE. The process parameters and the characteristics of the Au-C and BCN films are presented.

Synthesis and characterization of gold graphene composite with dyes as model substrates for decolorization: A surfactant free laser ablation approach

NASA Astrophysics Data System (ADS)

Sai Siddhardha, R. S.; Lakshman Kumar, V.; Kaniyoor, Adarsh; Sai Muthukumar, V.; Ramaprabhu, S.; Podila, Ramakrishna; Rao, A. M.; Ramamurthy, Sai Sathish

2014-12-01

A facile surfactant free laser ablation mediated synthesis (LAMS) of gold-graphene composite is reported here. The material was characterized using transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, powdered X-ray diffraction, Raman spectroscopy, Zeta potential measurements and UV-Visible spectroscopic techniques. The as-synthesized gold-graphene composite was effectively utilized as catalyst for decolorization of 4 important textile and laser dyes. The integration of gold nanoparticles (AuNPs) with high surface area graphene has enhanced the catalytic activity of AuNPs. This enhanced activity is attributed to the synergistic interplay of pristine gold's electronic relay and π-π stacking of graphene with the dyes. This is evident when the Rhodamine B (RB) reduction rate of the composite is nearly twice faster than that of commercial citrate capped AuNPs of similar size. In case of Methylene blue (MB) the rate of reduction is 17,000 times faster than uncatalyzed reaction. This synthetic method opens door to laser ablation based fabrication of metal catalysts on graphene for improved performance without the aid of linkers and surfactants.

Green synthesis of gold nanoparticles by Allium sativum extract and their assessment as SERS substrate

NASA Astrophysics Data System (ADS)

Coman, Cristina; Leopold, Loredana Florina; Rugină, Olivia Dumitriţa; Barbu-Tudoran, Lucian; Leopold, Nicolae; Tofană, Maria; Socaciu, Carmen

2014-01-01

A green synthesis was used for preparing stable colloidal gold nanoparticles by using Allium sativum aqueous extract both as reducing and capping agent. The obtained nanoparticles were characterized by UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and transmission electron microscopy. Moreover, their potential to be used as surface-enhanced Raman scattering (SERS) substrate was investigated. The obtained gold nanoparticles have spherical shape with mean diameters of 9-15 nm (depending on the amount of reducing agent used under boiling conditions) and are stable up to several months. FTIR spectroscopy shows that the nanoparticles are capped by protein molecules from the extract. The protein shell offers a protective coating, relatively impervious to external molecules, thus, rendering the nanoparticles stable and quite inert. These nanoparticles have the potential to be used as SERS substrates, both in solution and inside human fetal lung fibroblast HFL-1 living cells. We were able to demonstrate both the internalization of the nanoparticles inside HFL-1 cells and their ability to preserve the SERS signal after cellular internalization.

Removing interference-based effects from the infrared transflectance spectra of thin films on metallic substrates: a fast and wave optics conform solution.

PubMed

Mayerhöfer, Thomas G; Pahlow, Susanne; Hübner, Uwe; Popp, Jürgen

2018-06-25

A hybrid formalism combining elements from Kramers-Kronig based analyses and dispersion analysis was developed, which allows removing interference-based effects in the infrared spectra of layers on highly reflecting substrates. In order to enable a highly convenient application, the correction procedure is fully automatized and usually requires less than a minute with non-optimized software on a typical office PC. The formalism was tested with both synthetic and experimental spectra of poly(methyl methacrylate) on gold. The results confirmed the usefulness of the formalism: apparent peak ratios as well as the interference fringes in the original spectra were successfully corrected. Accordingly, the introduced formalism makes it possible to use inexpensive and robust highly reflecting substrates for routine infrared spectroscopic investigations of layers or films the thickness of which is limited by the imperative that reflectance absorbance must be smaller than about 1. For thicker films the formalism is still useful, but requires estimates for the optical constants.

A nonenzymatic DNA nanomachine for biomolecular detection by target recycling of hairpin DNA cascade amplification.

PubMed

Zheng, Jiao; Li, Ningxing; Li, Chunrong; Wang, Xinxin; Liu, Yucheng; Mao, Guobin; Ji, Xinghu; He, Zhike

2018-06-01

Synthetic enzyme-free DNA nanomachine performs quasi-mechanical movements in response to external intervention, suggesting the promise of constructing sensitive and specific biosensors. Herein, a smart DNA nanomachine biosensor for biomolecule (such as nucleic acid, thrombin and adenosine) detection is developed by target-assisted enzyme-free hairpin DNA cascade amplifier. The whole DNA nanomachine system is constructed on gold nanoparticle which decorated with hundreds of locked hairpin substrate strands serving as DNA tracks, and the DNA nanomachine could be activated by target molecule toehold-mediated exchange on gold nanoparticle surface, resulted in the fluorescence recovery of fluorophore. The process is repeated so that each copy of the target can open multiplex fluorophore-labeled hairpin substrate strands, resulted in amplification of the fluorescence signal. Compared with the conventional biosensors of catalytic hairpin assembly (CHA) without substrate in solution, the DNA nanomachine could generate 2-3 orders of magnitude higher fluorescence signal. Furthermore, the DNA nanomachine could be used for nucleic acid, thrombin and adenosine highly sensitive specific detection based on isothermal, and homogeneous hairpin DNA cascade signal amplification in both buffer and a complicated biomatrix, and this kind of DNA nanomachine could be efficiently applied in the field of biomedical analysis. Copyright © 2018 Elsevier B.V. All rights reserved.

Use of Standing Gold Nanorods for Detection of Malachite Green and Crystal Violet in Fish by SERS.

PubMed

Chen, Xiaowei; Nguyen, Trang H D; Gu, Liqun; Lin, Mengshi

2017-07-01

With growing consumption of aquaculture products, there is increasing demand on rapid and sensitive techniques that can detect prohibited substances in the seafood products. This study aimed to develop a novel surface-enhanced Raman spectroscopy (SERS) method coupled with simplified extraction protocol and novel gold nanorod (AuNR) substrates to detect banned aquaculture substances (malachite green [MG] and crystal violet [CV]) and their mixture (1:1) in aqueous solution and fish samples. Multivariate statistical tools such as principal component analysis (PCA) and partial least squares regression (PLSR) were used in data analysis. PCA results demonstrate that SERS can distinguish MG, CV and their mixture (1:1) in aqueous solution and in fish samples. The detection limit of SERS coupled with standing AuNR substrates is 1 ppb for both MG and CV in fish samples. A good linear relationship between the actual concentration and predicted concentration of analytes based on PLSR models with R 2 values from 0.87 to 0.99 were obtained, indicating satisfactory quantification results of this method. These results demonstrate that the SERS method coupled with AuNR substrates can be used for rapid and accurate detection of MG and CV in fish samples. © 2017 Institute of Food Technologists®.

Comparison of different bonding techniques for efficient strain transfer using piezoelectric actuators

NASA Astrophysics Data System (ADS)

Ziss, Dorian; Martín-Sánchez, Javier; Lettner, Thomas; Halilovic, Alma; Trevisi, Giovanna; Trotta, Rinaldo; Rastelli, Armando; Stangl, Julian

2017-04-01

In this paper, strain transfer efficiencies from a single crystalline piezoelectric lead magnesium niobate-lead titanate substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely, gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the "soft" SU8 bonding in comparison to the "hard" bonding via gold-thermo-compression. A comparison between the XRD results and FEM simulations allows us to explain this unexpected result with the presence of complex interface structures between the different layers.

Comparison of different bonding techniques for efficient strain transfer using piezoelectric actuators

PubMed Central

Ziss, Dorian; Martín-Sánchez, Javier; Lettner, Thomas; Halilovic, Alma; Trevisi, Giovanna; Trotta, Rinaldo; Rastelli, Armando; Stangl, Julian

2017-01-01

In this paper, strain transfer efficiencies from a single crystalline piezoelectric lead magnesium niobate-lead titanate substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely, gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the “soft” SU8 bonding in comparison to the “hard” bonding via gold-thermo-compression. A comparison between the XRD results and FEM simulations allows us to explain this unexpected result with the presence of complex interface structures between the different layers. PMID:28522879

Comparison of different bonding techniques for efficient strain transfer using piezoelectric actuators.

PubMed

Ziss, Dorian; Martín-Sánchez, Javier; Lettner, Thomas; Halilovic, Alma; Trevisi, Giovanna; Trotta, Rinaldo; Rastelli, Armando; Stangl, Julian

2017-04-01

In this paper, strain transfer efficiencies from a single crystalline piezoelectric lead magnesium niobate-lead titanate substrate to a GaAs semiconductor membrane bonded on top are investigated using state-of-the-art x-ray diffraction (XRD) techniques and finite-element-method (FEM) simulations. Two different bonding techniques are studied, namely, gold-thermo-compression and polymer-based SU8 bonding. Our results show a much higher strain-transfer for the "soft" SU8 bonding in comparison to the "hard" bonding via gold-thermo-compression. A comparison between the XRD results and FEM simulations allows us to explain this unexpected result with the presence of complex interface structures between the different layers.

Gold nanostructure-integrated silica-on-silicon waveguide for the detection of antibiotics in milk and milk products

NASA Astrophysics Data System (ADS)

Ozhikandathil, Jayan; Badilescu, Simona; Packirisamy, Muthukumaran

2012-10-01

Antibiotics are extensively used in veterinary medicine for the treatment of infectious diseases. The use of antibiotics for the treatment of animals used for food production raised the concern of the public and a rapid screening method became necessary. A novel approach of detection of antibiotics in milk is reported in this work by using an immunoassay format and the Localized Surface Plasmon Resonance property of gold. An antibiotic from the penicillin family that is, ampicillin is used for testing. Gold nanostructures deposited on a glass substrate by a novel convective assembly method were heat-treated to form a nanoisland morphology. The Au nanostructures were functionalized and the corresponding antibody was absorbed from a solution. Solutions with known concentrations of antigen (antibiotics) were subsequently added and the spectral changes were monitored step by step. The Au LSPR band corresponding to the nano-island structure was found to be suitable for the detection of the antibody antigen interaction. The detection of the ampicillin was successfully demonstrated with the gold nano-islands deposited on glass substrate. This process was subsequently adapted for the integration of gold nanostructures on the silica-on-silicon waveguide for the purpose of detecting antibiotics.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-01

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)—a chelating agent of copper II ions—was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

High sensitive detection of copper II ions using D-penicillamine-coated gold nanorods based on localized surface plasmon resonance.

PubMed

Hong, Yoochan; Jo, Seongjae; Park, Joohyung; Park, Jinsung; Yang, Jaemoon

2018-05-25

In this paper, we describe the development of a nanoplasmonic biosensor based on the localized surface plasmon resonance (LSPR) effect that enables a sensitive and selective recognition of copper II ions. First, we fabricated the nanoplasmonics as LSPR substrates using gold nanorods (GNR) and the nano-adsorption method. The LSPR sensitivity of the nanoplasmonics was evaluated using various solvents with different refractive indexes. Subsequently, D-penicillamine (DPA)-a chelating agent of copper II ions-was conjugated to the surface of the GNR. The limit of detection (LOD) for the DPA-conjugated nanoplasmonics was 100 pM. Furthermore, selectivity tests were conducted using various divalent cations, and sensitivity tests were conducted on the nanoplasmonics under blood-like environments. Finally, the developed nanoplasmonic biosensor based on GNR shows great potential for the effective recognition of copper II ions, even in human blood conditions.

Star tracking reticles

NASA Technical Reports Server (NTRS)

Smith, W. O.; Toft, A. R. (Inventor)

1973-01-01

A method for the production of reticles, particularly those for use in outer space, where the product is a quartz base coated with highly adherent layers of chromium, chromium-silver, and silver vacuum deposited through a mask, and then coated with an electrodeposit of copper from a copper sulfate solution followed by an electrodeposit of black chromium is described. The masks are produced by coating a beryllium-copper alloy substrate with a positive working photoresist, developing the photoresist, according to a pattern to leave a positive mask, plating uncoated areas with gold, removing the photoresist, coating the substrate with a negative working photoresist, developing the negative working photoresist to expose the base metal of the pattern, and chemically etching the unplated side of the pattern to produce the mask.

Back-surface gold mirrors for vibrationally resonant sum-frequency (VR-SFG) spectroscopy using 3-mercaptopropyltrimethoxysilane as an adhesion promoter.

PubMed

Quast, Arthur D; Zhang, Feng; Linford, Matthew R; Patterson, James E

2011-06-01

Back-surface mirrors are needed as reference materials for vibrationally resonant sum-frequency generation (VR-SFG) probing of liquid-solid interfaces. Conventional noble metal mirrors are not suitable for back-surface applications due to the presence of a metal adhesion layer (chromium or titanium) between the window substrate and the reflective metal surface. Using vapor deposited 3-mercaptopropyltrimethoxysilane (MPTMS) as a bi-functional adhesion promoter, gold mirrors were fabricated on fused silica substrates. These mirrors exhibit excellent gold adhesion as determined by the Scotch(®) tape test. They also produce minimal spectroscopic interference in the C-H stretching region (2800-3000 cm(-1)), as characterized by VR-SFG. These mirrors are thus robust and can be used as back-surface mirrors for a variety of applications, including reference mirrors for VR-SFG.

Pulsed laser deposition of plasmonic nanostructured gold on flexible transparent polymers at atmospheric pressure

NASA Astrophysics Data System (ADS)

McCann, Ronán; Hughes, Cian; Bagga, Komal; Stalcup, Apryll; Vázquez, Mercedes; Brabazon, Dermot

2017-06-01

In this paper, we outline a novel technique for the deposition of nanostructured thin films utilizing a modified form of pulsed laser deposition (PLD). We demonstrate confined atmospheric PLD (CAP) for the deposition of gold on cyclic olefin polymer substrates. The deposition process is a simplified form of conventional PLD, with deposition conducted under atmospheric conditions and the substrate and target in close proximity. It was found that this confinement results in the deposition of nanostructured thin films on the substrate. Infrared spectroscopy showed no significant change of polymer surface chemistry as a result of the deposition process, and optical spectroscopy revealed plasmonic behavior of the resulting thin film. The effect of laser fluence on the deposition process was also examined with more uniform films deposited at higher fluences.

Formation and Characterization of Gold Nanoparticles

DTIC Science & Technology

2013-09-01

nanowires are useful because they can be grown almost dislocation free, due to their nano dimension. The quality of crystalline materials is diminished by...real substrate temperature was obtained from the calibration based on the melting points of indium (In), selenium (Se), cadmium (Cd), and zinc (Zn...hydrogen fluoride In indium MBE molecular beam epitaxy NH3OH ammonium hydroxide RHEED reflection high-energy electron diffraction Se selenium SEM

Mid-infrared plasmonic resonances exploiting heavily-doped Ge on Si

NASA Astrophysics Data System (ADS)

Biagioni, P.; Sakat, E.; Baldassarre, L.; Calandrini, E.; Samarelli, A.; Gallacher, K.; Frigerio, J.; Isella, G.; Paul, D. J.; Ortolani, M.

2015-03-01

We address the behavior of mid-infrared localized plasmon resonances in elongated germanium antennas integrated on silicon substrates. Calculations based on Mie theory and on the experimentally retrieved dielectric constant allow us to study the tunability and the figures of merit of plasmon resonances in heavily-doped germanium and to preliminarily compare them with those of the most established plasmonic material, gold.

Solid-State Dewetting of Gold Aggregates/Islands on TiO2 Nanorod Structures Grown by Oblique Angle Deposition.

PubMed

Liu, Shizhao; Plawsky, Joel L

2017-12-12

A composite film made of a stable gold nanoparticle (NP) array with well-controlled separation and size atop a TiO 2 nanorod film was fabricated via the oblique angle deposition (OAD) technique. The fabrication of the NP array is based on controlled, Rayleigh-instability-induced, solid-state dewetting of as-deposited gold aggregates on the TiO 2 nanorods. It was found that the initial spacing between as-deposited gold aggregates along the vapor flux direction should be greater than the TiO 2 interrod spacing created by 80° OAD to control dewetting and produce NP arrays. A numerical investigation of the process was conducted using a phase-field modeling approach. Simulation results showed that coalescence between neighboring gold aggregates is likely to have caused the uncontrolled dewetting in the 80° deposition, and this could be circumvented if the initial spacing between gold aggregates is larger than a critical value s min . We also found that TiO 2 nanorod tips affect dewetting dynamics differently than planar TiO 2 . The topology of the tips can induce contact line pinning and an increase in the contact angle along the vapor flux direction to the supported gold aggregates. These two effects are beneficial for the fabrication of monodisperse NPs based on Rayleigh-instability-governed self-assembly of materials, as they help to circumvent the undesired coalescence and facilitate the instability growth on the supported material. The findings uncover the application potential of OAD as a new method to fabricate structured films as template substrates to mediate dewetting. The reported composite films would have uses in optical coatings and photocatalytic systems, taking advantage of their ability to combine plasmonic nanostructures within a nanostructured dielectric film.

A terahertz-vibration to terahertz-radiation converter based on gold nanoobjects: a feasibility study.

PubMed

Moldosanov, Kamil; Postnikov, Andrei

2016-01-01

The need for practical and adaptable terahertz sources is apparent in the areas of application such as early cancer diagnostics, nondestructive inspection of pharmaceutical tablets, visualization of concealed objects. We outline the operation principle and suggest the design of a simple appliance for generating terahertz radiation by a system of nanoobjects - gold nanobars (GNBs) or nanorings (GNRs) - irradiated by microwaves. Our estimations confirm a feasibility of the idea that GNBs and GNRs irradiated by microwaves could become terahertz emitters with photon energies within the full width at half maximum of the longitudinal acoustic phononic DOS of gold (ca. 16-19 meV, i.e., 3.9-4.6 THz). A scheme of the terahertz radiation source is suggested based on the domestic microwave oven irradiating a substrate with multiple deposited GNBs or GNRs. The size of a nanoobject for optimal conversion is estimated to be approx. 3 nm (thickness) by approx. 100 nm (length of GNB, or along the GNR). This detailed prediction is open to experimental verification. An impact is expected onto further studies of interplay between atomic vibrations and electromagnetic waves in nanoobjects.

Fabrication of a cost-effective polymer nanograting as a disposable plasmonic biosensor using nanoimprint lithography

NASA Astrophysics Data System (ADS)

Mohapatra, Saswat; Kumari, Sudha; Moirangthem, Rakesh S.

2017-07-01

A simple and cost-effective flexible plasmonic sensor is developed using a gold-coated polymer nanograting structure prepared via soft UV nanoimprint lithography. The sub-wavelength nanograting patterns of digital versatile discs were used as a template to prepare the polydimethylsiloxane stamp. The plasmonic sensing substrate was achieved after coating a gold thin film on top of the imprinted nanograting sample. The surface plasmon resonance (SPR) modes excited on the gold-coated nanograting structure appeared as a dip in the reflectance spectrum measured at normal incidence under white light illumination in the ambient air medium. Electromagnetic simulation based on the finite element method was carried out to analyze the excited SPR modes. The simulated result shows very close agreement with the experimental data. The performance of the sensor with respect to changing the surrounding dielectric medium yields a bulk refractive index sensitivity of 788  ±  21 nm per refractive index unit. Further, label-free detection of proteins using a plasmonic sensing substrate was demonstrated by monitoring specific interactions between bovine serum albumin (BSA) and anti-BSA proteins, which gave a detection limit of 123 pg mm-2 with respect to target anti-BSA protein binding. Thus, our proposed plasmonic sensor has potential for the development of an economical and highly sensitive label-free optical biosensing device for biomedical applications.

Amperometric inhibition biosensors based on horseradish peroxidase and gold sononanoparticles immobilized onto different electrodes for cyanide measurements.

PubMed

Attar, Aisha; Cubillana-Aguilera, Laura; Naranjo-Rodríguez, Ignacio; de Cisneros, José Luis Hidalgo-Hidalgo; Palacios-Santander, José María; Amine, Aziz

2015-02-01

New biosensors based on inhibition for the detection of cyanide and the comparison of the analytical performances of nine enzyme biosensor designs by using three different electrodes: Sonogel-Carbon, glassy carbon and gold electrodes were discussed. Three different horseradish peroxidase immobilization procedures with and without gold sononanoparticles were studied. The amperometric measurements were performed at an applied potential of -0.15V vs. Ag/AgCl in 50mM sodium acetate buffer solution pH=5.0. The apparent kinetic parameters (Kmapp, Vmaxapp) of immobilized HRP were calculated in the absence of inhibitor (cyanide) by using caffeic acid, hydroquinone, and catechol as substrates. The presence of gold sononanoparticles enhanced the electron transfer reaction and improved the analytical performance of the biosensors. The HRP kinetic interactions reveal non-competitive binding of cyanide with an apparent inhibition constant (Ki) of 2.7μM and I50 of 1.3μM. The determination of cyanide can be achieved in a dynamic range of 0.1-58.6μM with a detection limit of 0.03μM which is lower than those reported by previous studies. Hence this biosensing methodology can be used as a new promising approach for detecting cyanide. Copyright © 2014. Published by Elsevier B.V.

Interferometric detection of nanoparticles

NASA Astrophysics Data System (ADS)

Hayrapetyan, Karen

Interferometric surfaces enhance light scattering from nanoparticles through constructive interference of partial scattered waves. By placing the nanoparticles on interferometric surfaces tuned to a special surface phase interferometric condition, the particles are detectable in the dilute limit through interferometric image contrast in a heterodyne light scattering configuration, or through diffraction in a homodyne scattering configuration. The interferometric enhancement has applications for imaging and diffractive biosensors. We present a modified model based on Double Interaction (DI) to explore bead-based detection mechanisms using imaging, scanning and diffraction. The application goal of this work is to explore the trade-offs between the sensitivity and throughput among various detection methods. Experimentally we use thermal oxide on silicon to establish and control surface interferometric conditions. Surface-captured gold beads are detected using Molecular Interferometric Imaging (MI2) and Spinning-Disc Interferometry (SDI). Double-resonant enhancement of light scattering leads to high-contrast detection of 100 nm radius gold nanoparticles on an interferometric surface. The double-resonance condition is achieved when resonance (or anti-resonance) from an asymmetric Fabry-Perot substrate coincides with the Mie resonance of the gold nanoparticle. The double-resonance condition is observed experimentally using molecular interferometric imaging (MI2). An invisibility condition is identified for which the gold nanoparticles are optically cloaked by the interferometric surface.

High temperature superconducting thin film microwave circuits: Fabrication, characterization, and applications

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Chorey, C. M.

1990-01-01

Epitaxial YBa2Cu3O7 films were grown on several microwave substrates. Surface resistance and penetration depth measurements were performed to determine the quality of these films. Here the properties of these films on key microwave substrates are described. The fabrication and characterization of a microwave ring resonator circuit to determine transmission line losses are presented. Lower losses than those observed in gold resonator circuits were observed at temperatures lower than critical transition temperature. Based on these results, potential applications of microwave superconducting circuits such as filters, resonators, oscillators, phase shifters, and antenna elements in space communication systems are identified.

High temperature superconducting thin film microwave circuits - Fabrication, characterization, and applications

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Warner, J. D.; Romanofsky, R. R.; Heinen, V. O.; Chorey, C. M.

1990-01-01

Epitaxial YBa2Cu3O7 films were grown on several microwave substrates. Surface resistance and penetration depth measurements were performed to determine the quality of these films. Here, the properties of these films on key microwave substrates are described. The fabrication and characterization of a microwave ring resonator circuit to determine transmission line losses are presented. Lower losses than those observed in gold resonator circuits were observed at temperatures lower than critical transition temperature. Based on these results, potential applications of microwave superconducting circuits such as filters, resonators, oscillators, phase shifters, and antenna elements in space communication systems are identified.

Atomic force measurements of 16-mercaptohexadecanoic acid and its salt with CH 3, OH, and CONHCH 3 functionalized self-assembled monolayers

NASA Astrophysics Data System (ADS)

Morales-Cruz, Angel L.; Tremont, Rolando; Martínez, Ramón; Romañach, Rodolfo; Cabrera, Carlos R.

2005-03-01

Chemical and mechanical properties of different compounds can be elucidated by measuring fundamental forces such as adhesion, attraction and repulsion, between modified surfaces by means of atomic force microscopy (AFM) in force mode calibration. This work presents a combination of AFM, self-assembled monolayers (SAMs), and crystallization techniques to study the forces of interaction between excipients and active ingredients used in pharmaceutical formulations. SAMs of 16-mercaptohexadecanoate, which represent magnesium stereate, were used to modify the probe tip, whereas CH3-, OH- and CONHCH3-functional SAMs were formed on a gold-coated mica substrate, and used as examples of the surfaces of lactose and theophylline. The crystals of lactose and theophylline were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The modification of gold surfaces with 16-mercaptohexadecanoate, 10-mercapto-1-decanol (OH-functional SAM), 1-decanethiol (CH3-functional) and N-methyl-11-mercaptoundecanamide (CONHCH3-functional SAM) was studied by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Fourier transform-infrared spectroscopy (FT-IR) in specular reflectance mode. XPS and AES results of the modified surfaces showed the presence of sulfur binding, and kinetic energies that correspond to the presence of 10-mercapto-1-decanol, 1-decanethiol, N-methyl-11-mercaptoundecanamide and the salt of 16-mercaptohexadecanoic acid. The absorption bands in the IR spectra further confirm the modification of the gold-coated substrates with these compounds. Force versus distance measurements were performed between the modified tip and the modified gold-coated mica substrates. The mean adhesion forces between the COO-Ca2+ functionalized tip and the CH3-, OH-, and CONHCH3-modified substrates were determined to be 4.5, 8.9 and 6.3 nN, respectively. The magnitude of the adhesion force (ion-dipole) interaction between the modified tip and substrate decreases in the following order: COO-Ca2+/OH > COO-Ca2+/CONHCH3 > COO-Ca2+/CH3.

Structure and properties of polyaniline nanocomposite coatings containing gold nanoparticles formed by low-energy electron beam deposition

NASA Astrophysics Data System (ADS)

Wang, Surui; Rogachev, A. A.; Yarmolenko, M. A.; Rogachev, A. V.; Xiaohong, Jiang; Gaur, M. S.; Luchnikov, P. A.; Galtseva, O. V.; Chizhik, S. A.

2018-01-01

Highly ordered conductive polyaniline (PANI) coatings containing gold nanoparticles were prepared by low-energy electron beam deposition method, with emeraldine base and chloroauric acid used as target materials. The molecular and chemical structure of the layers was studied by Fourier transform infrared, Raman, UV-vis and X-ray photoelectron spectroscopy. The morphology of the coatings was investigated by atomic force and transmission electron microscopy. Conductive properties were obtained by impedance spectroscopy method and scanning spreading resistance microscopy mode at the micro- and nanoscale. It was found that the emeraldine base layers formed from the products of electron-beam dispersion have extended, non-conductive polymer chains with partially reduced structure, with the ratio of imine and amine groups equal to 0.54. In case of electron-beam dispersion of the emeraldine base and chloroauric acid, a protoemeraldine structure is formed with conductivity 0.1 S/cm. The doping of this structure was carried out due to hydrochloric acid vapor and gold nanoparticles formed by decomposition of chloroauric acid, which have a narrow size distribution, with the most probable diameter about 40 nm. These gold nanoparticles improve the conductivity of the thin layers of PANI + Au composite, promoting intra- and intermolecular charge transfer of the PANI macromolecules aligned along the coating surface both at direct and alternating voltage. The proposed deposition method of highly oriented, conductive nanocomposite PANI-based coatings may be used in the direct formation of functional layers on conductive and non-conductive substrates.

Nanoplasmonic-gold-cylinder-array-enhanced terahertz source

NASA Astrophysics Data System (ADS)

Zhiguang, Ao; Jinhai, Sun; He, Cai; Guofeng, Song; Jiakun, Song; Yuzhi, Song; Yun, Xu

2016-12-01

Photoconductive antennas (PCAs) based on nanoplasmonic gratings contact electrodes have been proposed to satisfy the demand for high power, efficiency and responsivity terahertz (THz) sources. Reducing the average photo-generated carrier transport path to the photoconductor contact electrodes was previously considered the dominant mechanism to improve PCAs' power. However, considering the bias in a real device, the electric field between gratings is limited and the role of surface plasmonic resonance (SPR) field enhancement is more important in improving THz radiation. This paper, based on SPR, analyzes the interaction between incident light and substrate in nano cylinder array PCAs and clearly shows that the SPR can enhance the light absorption in the substrate. After the optimization of the structure size, the proposed structure can offer 87% optical transmission into GaAs substrate. Compared with conventional PCAs, the optical transmission into the substrate will increase 5.8 times and the enhancement factor of substrate absorption will reach 13.7 respectively. Project supported by the National Basic Research Program of China (Nos. 2015CB351902, 2015CB932402), the National Key Research Program of China (No. 2011ZX01015-001), and the National Natural Science Foundation of China (No. U143231).

Direct mapping of electrical noise sources in molecular wire-based devices

PubMed Central

Cho, Duckhyung; Lee, Hyungwoo; Shekhar, Shashank; Yang, Myungjae; Park, Jae Yeol; Hong, Seunghun

2017-01-01

We report a noise mapping strategy for the reliable identification and analysis of noise sources in molecular wire junctions. Here, different molecular wires were patterned on a gold substrate, and the current-noise map on the pattern was measured and analyzed, enabling the quantitative study of noise sources in the patterned molecular wires. The frequency spectra of the noise from the molecular wire junctions exhibited characteristic 1/f2 behavior, which was used to identify the electrical signals from molecular wires. This method was applied to analyze the molecular junctions comprising various thiol molecules on a gold substrate, revealing that the noise in the junctions mainly came from the fluctuation of the thiol bonds. Furthermore, we quantitatively compared the frequencies of such bond fluctuations in different molecular wire junctions and identified molecular wires with lower electrical noise, which can provide critical information for designing low-noise molecular electronic devices. Our method provides valuable insights regarding noise phenomena in molecular wires and can be a powerful tool for the development of molecular electronic devices. PMID:28233821

SERS as a bioassay platform: fundamentals, design, and applications

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

Porter, M.; Lipert, R.; Siperko, L.

2008-03-18

Bioanalytical science is experiencing a period of unprecedented growth. Drivers behind this growth include the need to detect markers central to human and veterinary diagnostics at ever-lower levels and greater speeds. A set of parallel arguments applies to pathogens with respect to bioterrorism prevention and food and water safety. This tutorial review outlines our recent explorations on the use of surface enhanced Raman scattering (SERS) for detection of proteins, viruses, and microorganisms in heterogeneous immunoassays. It will detail the design and fabrication of the assay platform, including the capture substrate and nanoparticle-based labels. The latter, which is the cornerstone ofmore » our strategy, relies on the construction of gold nanoparticles modified with both an intrinsically strong Raman scatterer and an antibody. This labelling motif, referred to as extrinsic Raman labels (ERLs), takes advantage of the well-established signal enhancement of scatterers when coated on nanometre-sized gold particles, whereas the antibody imparts antigenic specificity. We will also examine the role of plasmon coupling between the ERLs and capture substrate, and challenges related to particle stability, nonspecific adsorption, and assay speed.« less

Direct mapping of electrical noise sources in molecular wire-based devices

NASA Astrophysics Data System (ADS)

Cho, Duckhyung; Lee, Hyungwoo; Shekhar, Shashank; Yang, Myungjae; Park, Jae Yeol; Hong, Seunghun

2017-02-01

We report a noise mapping strategy for the reliable identification and analysis of noise sources in molecular wire junctions. Here, different molecular wires were patterned on a gold substrate, and the current-noise map on the pattern was measured and analyzed, enabling the quantitative study of noise sources in the patterned molecular wires. The frequency spectra of the noise from the molecular wire junctions exhibited characteristic 1/f2 behavior, which was used to identify the electrical signals from molecular wires. This method was applied to analyze the molecular junctions comprising various thiol molecules on a gold substrate, revealing that the noise in the junctions mainly came from the fluctuation of the thiol bonds. Furthermore, we quantitatively compared the frequencies of such bond fluctuations in different molecular wire junctions and identified molecular wires with lower electrical noise, which can provide critical information for designing low-noise molecular electronic devices. Our method provides valuable insights regarding noise phenomena in molecular wires and can be a powerful tool for the development of molecular electronic devices.

Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

PubMed Central

Braun, Kai; Wang, Xiao; Kern, Andreas M; Adler, Hilmar; Peisert, Heiko; Chassé, Thomas; Zhang, Dai

2015-01-01

Summary Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip) of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode) into the highest occupied orbital of the closest substrate-bound molecule (lower level) and radiative recombination with an electron from above the Fermi level (upper level), hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode. PMID:26171286

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.

All-optical in-depth detection of the acoustic wave emitted by a single gold nanorod

NASA Astrophysics Data System (ADS)

Xu, Feng; Guillet, Yannick; Ravaine, Serge; Audoin, Bertrand

2018-04-01

A single gold nanorod dropped on the surface of a silica substrate is used as a transient optoacoustic source of gigahertz hypersounds. We demonstrate the all-optical detection of the as-generated acoustic wave front propagating in the silica substrate. For this purpose, time-resolved femtosecond pump-probe experiments are performed in a reflection configuration. The fundamental breathing mode of the nanorod is detected at 23 GHz by interferometry, and the longitudinal acoustic wave radiated in the silica substrate is detected by time-resolved Brillouin scattering. By tuning the optical probe wavelength from 750 to 900 nm, hypersounds with wavelengths of 260-315 nm are detected in the silica substrate, with corresponding acoustic frequencies in the range of 19-23 GHz. To confirm the origin of these hypersounds, we theoretically analyze the influence of the acoustic excitation spectrum on the temporal envelope of the transient reflectivity. This analysis proves that the acoustic wave detected in the silica substrate results from the excitation of the breathing mode of the nanorod. These results pave the way for performing local in-depth elastic nanoscopy.

Laser-ablative fabrication of nanoparticle inks for 3D inkjetprinting of multifunctional coatings

NASA Astrophysics Data System (ADS)

Ionin, A. A.; Ivanova, A. K.; Khmel'nitskii, R. A.; Klevkov, Yu V.; Kudryashov, S. I.; Mel'nik, N. N.; Nastulyavichus, A. A.; Rudenko, A. A.; Saraeva, I. N.; Smirnov, N. A.; Zayarny, D. A.

2017-12-01

We report the fabrication of multifunctional coatings via inkjet printing using water-based nanoinks in the form of selenium (Se) and gold (Au) nanoparticle (NP) colloids, prepared by laser ablation of solid targets in deionized water or 50%-isopropyl alcohol solution. Nanoparticles and NP-based coatings were deposited onto silver films, magnetronsputtered to silica-glass substrates, and characterized by means of scanning and transmission electron microscopy (SEM, TEM), UV-vis-IR, Raman and energy-dispersive X-ray spectroscopies.

Interfacial chemistry of a perfluoropolyether lubricant studied by XPS and TDS

NASA Technical Reports Server (NTRS)

Herrera-Fierro, Pilar C.; Jones, William R., Jr.; Pepper, Stephen V.

1992-01-01

The interfacial chemistry of Fomblin Z25, a commercial perfluoropolyether used as lubricant for space applications, with different metallic surfaces: 440C steel, gold and aluminum was studied. Thin layers of Fomblin Z25 were evaporated onto the oxide-free substrates and the interfacial chemistry studied using XPS and TDS. The reactions were induced by heating the substrate and by rubbing the substrate with a steel ball. Gold was found to be completely unreactive towards Fomblin at any temperature. Reaction at room temperature was observed only in the case of the aluminum substrate, the most reactive towards Fomblin Z25 of the substrates studied. It was necessary to heat the 440C steel substrate to 190 degree C to induce decomposition of the fluid. The degradation of the fluid was indicated by the formation of a debris layer at the interface. This debris layer, composed of inorganic and organic reaction products, when completely formed, passivated the surface from further attack to the Fromblin on top. The tribologically induced reactions on 440C steel formed a debris layer of similar chemical characteristics to the thermally induced layer. In all cases, the degradation reaction resulted in preferential consumption of the difluoroformyl carbon (-OCF2O-).

Efficient surface enhanced Raman scattering on confeito-like gold nanoparticle-adsorbed self-assembled monolayers.

PubMed

Chang, Chia-Chi; Imae, Toyoko; Chen, Liang-Yih; Ujihara, Masaki

2015-12-28

Confeito-like gold nanoparticles (AuNPs; average diameter = 80 nm) exhibiting a plasmon absorption band at 590 nm were adsorbed through immersion-adsorption on two self-assembled monolayers (SAMs) of 3-aminopropyltriethoxysilane (APTES-SAM) and polystyrene spheres coated with amine-terminated poly(amido amine) dendrimers (DEN/PS-SAM). The surface enhanced Raman scattering (SERS) effect on the SAM substrates was examined using the molecules of a probe dye, rhodamine 6G (R6G). The Raman scattering was strongly intensified on both substrates, but the enhancement factor (>10,000) of the AuNP/DEN/PS-SAM hierarchy substrate was 5-10 times higher than that of the AuNP/APTES-SAM substrate. This strong enhancement is attributed to the large surface area of the substrate and the presence of hot spots. Furthermore, analyzing the R6G concentration dependence of SERS suggested that the enhancement mechanism effectively excited the R6G molecules in the first layer on the hot spots and invoked the strong SERS effect. These results indicate that the SERS activity of confeito-like AuNPs on SAM substrates has high potential in molecular electronic devices and ultrasensitive analyses.

Tribological properties of ceramic-(Ti3Al-Nb) sliding couples for use as candidate seal materials to 700 C

NASA Technical Reports Server (NTRS)

Dellacorte, Christhopher; Steinetz, Bruce M.; Brindley, Pamela K.

1990-01-01

Tribological properties of Ti3Al-Nb intermetallic disks sliding against alumina-boria-silicate fabric were ascertained in air at temperatures from 25 to 700 C. These materials are candidates for sliding seal applications for the National AeroSpace Plane. The tests were done using a pin on disk tribometer. Sliding was unidirectional at 0.27 m/sec under a nominal contact stress of 340 kPa. Gold sputter or ion plating deposited films were used to reduce friction and wear. Rhodium and palladium films were used beneath the gold lubricating films to prevent diffusion of the substrate into the gold at high temperature. The friction and wear of the unlubricated specimens was unacceptable. Friction coefficients were generally greater than 1.0. The ion plated gold films, when used with a rhodium diffusion barrier reduced friction by almost a factor of 2. Wear was also substantially reduced. The sputter deposited films were not adherent unless the substrate was sputter cleaned immediately prior to film deposition. Palladium did not function as a diffusion barrier.

Tribological properties of ceramic/Ti3Al-Nb sliding couples for use as candidate seal materials to 700 deg C

NASA Technical Reports Server (NTRS)

Dellacorte, Christopher; Steinetz, Bruce M.; Brindley, Pamela K.

1989-01-01

Tribological properties of Ti3Al-Nb intermetallic disks sliding against alumina-boria-silicate fabric were ascertained in air at temperatures from 25 to 700 C. These materials are candidates for sliding seal applications for the National AeroSpace Plane. The tests were done using a pin on disk tribometer. Sliding was unidirectional at 0.27 m/sec under a nominal contact stress of 340 kPa. Gold sputter or ion plating deposited films were used to reduce friction and wear. Rhodium and palladium films were used beneath the gold lubricating films to prevent diffusion of the substrate into the gold at high temperature. The friction and wear of the unlubricated specimens was unacceptable. Friction coefficients were generally greater than 1.0. The ion plated gold films, when used with a rhodium diffusion barrier reduced friction by almost a factor of 2. Wear was also substantially reduced. The sputter deposited films were not adherent unless the substrate was sputter cleaned immediately prior to film deposition. Palladium did not function as a diffusion barrier.

SERS activity with tenfold detection limit optimization on a type of nanoporous AAO-based complex multilayer substrate

NASA Astrophysics Data System (ADS)

Sui, Chaofan; Wang, Kaige; Wang, Shuang; Ren, Junying; Bai, Xiaohong; Bai, Jintao

2016-03-01

Most of SERS applications are constricted by heterogeneous hotspots and aggregates of nanostructure, which result in low sensitivity and poor reproducibility of characteristic signals. This work intends to introduce SERS properties of a type of SERS-active substrate, Au-CuCl2-AAO, which is innovatively developed on a porous anodic alumina oxide (AAO) template. Spectral measuring results of Rhodamine 6G (R6G) on this substrate optimized by controlling morphology and gold thickness showed that enhancement factor (2.30 × 107) and detection limit (10-10 M) were both improved and represented better performance than its template AAO. Homogenous hot spots across the region of interest were achieved by scanning SERS intensity distribution for the band at 1505 cm-1 in 5 × 5 μm2 area. Furthermore, the promising SERS activity of the flower-patterned substrate was theoretically explained through simulation of the electromagnetic field distribution. In addition, this SERS substrate is proposed for applications within the field of chemical and biochemical analyses.Most of SERS applications are constricted by heterogeneous hotspots and aggregates of nanostructure, which result in low sensitivity and poor reproducibility of characteristic signals. This work intends to introduce SERS properties of a type of SERS-active substrate, Au-CuCl2-AAO, which is innovatively developed on a porous anodic alumina oxide (AAO) template. Spectral measuring results of Rhodamine 6G (R6G) on this substrate optimized by controlling morphology and gold thickness showed that enhancement factor (2.30 × 107) and detection limit (10-10 M) were both improved and represented better performance than its template AAO. Homogenous hot spots across the region of interest were achieved by scanning SERS intensity distribution for the band at 1505 cm-1 in 5 × 5 μm2 area. Furthermore, the promising SERS activity of the flower-patterned substrate was theoretically explained through simulation of the electromagnetic field distribution. In addition, this SERS substrate is proposed for applications within the field of chemical and biochemical analyses. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06771e

From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

NASA Astrophysics Data System (ADS)

Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V.

2013-05-01

The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources. Electronic supplementary information (ESI) available: The full GISAXS image sequence of the experiment, the model-based IsGISAXS-simulation sequence as movie files for comparison and detailed information about sample cleaning, XRR, FESEM, IsGISAXS, comparison μGIWAXS/μGISAXS, and sampling statistics. See DOI: 10.1039/c3nr34216f

Surface analysis of gold nanoparticles functionalized with thiol-modified glucose SAMs for biosensor applications.

NASA Astrophysics Data System (ADS)

Spampinato, Valentina; Parracino, Mariaantonietta; La Spina, Rita; Rossi, Francois; Ceccone, Giacomo

2016-02-01

In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Principal Component Analysis (PCA) and X-ray Photoelectron Spectroscopy (XPS) have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP). The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules. Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behaviour of the glucose-modified particles in presence of the maltose binding protein.

Surface Analysis of Gold Nanoparticles Functionalized with Thiol-Modified Glucose SAMs for Biosensor Applications

PubMed Central

Spampinato, Valentina; Parracino, Maria Antonietta; La Spina, Rita; Rossi, Francois; Ceccone, Giacomo

2016-01-01

In this work, Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Principal Component Analysis (PCA) and X-ray Photoelectron Spectroscopy (XPS) have been used to characterize the surface chemistry of gold substrates before and after functionalization with thiol-modified glucose self-assembled monolayers and subsequent biochemical specific recognition of maltose binding protein (MBP). The results indicate that the surface functionalization is achieved both on flat and nanoparticles gold substrates thus showing the potential of the developed system as biodetection platform. Moreover, the method presented here has been found to be a sound and valid approach to characterize the surface chemistry of nanoparticles functionalized with large molecules. Both techniques were proved to be very useful tools for monitoring all the functionalization steps, including the investigation of the biological behavior of the glucose-modified particles in the presence of the maltose binding protein. PMID:26973830

Templating effect of the substrate on the structure of Cu-phthalocyanine thin film

NASA Astrophysics Data System (ADS)

Pierantozzi, Gian Marco; Sbroscia, Marco; Ruocco, Alessandro

2018-03-01

An experimental study of electronic properties, structure and morphology of Copper-phthalocyanine films deposited onto Al(100) and Au(110), as a function of thickness up to tens of nanometers, is presented. The monolayers grown on these two model substrates are already known to exhibit very different behavior for what concerns both the degree of interaction with the substrate and the formation of long range order; in this experiment, by means of low energy electron scattering and Electron Energy Loss Spectroscopy (EELS), remarkable differences are revealed also in the successive growth. Exploiting the link between the crystal structure and the lineshape of HOMO-LUMO transition in EELS spectrum, two different structural phases are identified, compatible with α and β phases, respectively in the case of the film grown on aluminum and on gold. Besides, the evolution of the specular reflection elastic peak indicates the formation of islands on the gold substrate and a more homogeneous growth on the aluminum one.

Template-Stripped Tunable Plasmonic Devices on Stretchable and Rollable Substrates

PubMed Central

2015-01-01

We use template stripping to integrate metallic nanostructures onto flexible, stretchable, and rollable substrates. Using this approach, high-quality patterned metals that are replicated from reusable silicon templates can be directly transferred to polydimethylsiloxane (PDMS) substrates. First we produce stretchable gold nanohole arrays and show that their optical transmission spectra can be modulated by mechanical stretching. Next we fabricate stretchable arrays of gold pyramids and demonstrate a modulation of the wavelength of light resonantly scattered from the tip of the pyramid by stretching the underlying PDMS film. The use of a flexible transfer layer also enables template stripping using a cylindrical roller as a substrate. As an example, we demonstrate roller template stripping of metallic nanoholes, nanodisks, wires, and pyramids onto the cylindrical surface of a glass rod lens. These nonplanar metallic structures produced via template stripping with flexible and stretchable films can facilitate many applications in sensing, display, plasmonics, metasurfaces, and roll-to-roll fabrication. PMID:26402066

Amperometric inhibitive biosensor based on horseradish peroxidase-nanoporous gold for sulfide determination

PubMed Central

Sun, Huihui; Liu, Zhuang; Wu, Chao; Xu, Ping; Wang, Xia

2016-01-01

As a well-known toxic pollutant, sulfide is harmful to human health. In this study, a simple and sensitive amperometric inhibitive biosensor was developed for the determination of sulfide in the environment. By immobilizing nanoporous gold (NPG) on glassy carbon electrode (GCE), and encapsulating horseradish peroxidase (HRP) onto NPG, a HRP/NPG/GCE bioelectrode for sulfide detection was successfully constructed based on the inhibition of sulfide on HRP activity with o-Phenylenediamine (OPD) as a substrate. The resulted HRP/NPG/GCE bioelectrode achieved a wide linear range of 0.1–40 μM in sulfide detection with a high sensitivity of 1720 μA mM−1 cm−2 and a low detection limit of 0.027 μM. Additionally, the inhibition of sulfide on HRP is competitive inhibition with OPD as a substrate by Michaelis-Menten analysis. Notably, the recovery of HRP activity was quickly achieved by washing the HRP/NPG/GCE bioelectrode using differential pulse voltammetry (DPV) technique in deaerated PBS (50 mM, pH 7.0) for only 60 s. Furthermore, the real sample analysis of sulfide by the HRP/NPG/GCE bioelectrode was achieved. Based on above results, the HRP/NPG/GCE bioelectrode could be a better choice for the real determination of sulfide compared to inhibitive biosensors previously reported. PMID:27515253

Partially reduced graphene oxide-gold nanorods composite based bioelectrode of improved sensing performance.

PubMed

Nirala, Narsingh R; Abraham, Shiju; Kumar, Vinod; Pandey, Shobhit A; Yadav, Umakant; Srivastava, Monika; Srivastava, S K; Singh, Vidya Nand; Kayastha, Arvind M; Srivastava, Anchal; Saxena, Preeti S

2015-11-01

The present work proposes partially reduced graphene oxide-gold nanorods supported by chitosan (CH-prGO-AuNRs) as a potential bioelectrode material for enhanced glucose sensing. Developed on ITO substrate by immobilizing glucose oxidase on CH-prGO-AuNRs composite, these CH-prGO-AuNRs/ITO bioelectrodes demonstrate high sensitivity of 3.2 µA/(mg/dL)/cm(2) and linear range of 25-200 mg/dL with an ability to detect as low as 14.5 mg/dL. Further, these CH-prGO-AuNRs/ITO based electrodes attest synergistiacally enhanced sensing properties when compared to simple graphene oxide based CH-GO/ITO electrode. This is evident from one order higher electron transfer rate constant (Ks) value in case of CH-prGO-AuNRs modified electrode (12.4×10(-2) cm/s), in contrast to CH-GO/ITO electrode (6×10(-3) cm/s). Additionally, very low Km value [15.4 mg/dL(0.85 mM)] ensures better binding affinity of enzyme to substrate which is desirable for good biosensor stability and resistance to environmental interferences. Hence, with better loading capacity, kinetics and stability, the proposed CH-prGO-AuNRs composite shows tremendous potential to detect several bio-analytes in the coming future. Copyright © 2015 Elsevier B.V. All rights reserved.

Amperometric inhibitive biosensor based on horseradish peroxidase-nanoporous gold for sulfide determination

NASA Astrophysics Data System (ADS)

Sun, Huihui; Liu, Zhuang; Wu, Chao; Xu, Ping; Wang, Xia

2016-08-01

As a well-known toxic pollutant, sulfide is harmful to human health. In this study, a simple and sensitive amperometric inhibitive biosensor was developed for the determination of sulfide in the environment. By immobilizing nanoporous gold (NPG) on glassy carbon electrode (GCE), and encapsulating horseradish peroxidase (HRP) onto NPG, a HRP/NPG/GCE bioelectrode for sulfide detection was successfully constructed based on the inhibition of sulfide on HRP activity with o-Phenylenediamine (OPD) as a substrate. The resulted HRP/NPG/GCE bioelectrode achieved a wide linear range of 0.1-40 μM in sulfide detection with a high sensitivity of 1720 μA mM-1 cm-2 and a low detection limit of 0.027 μM. Additionally, the inhibition of sulfide on HRP is competitive inhibition with OPD as a substrate by Michaelis-Menten analysis. Notably, the recovery of HRP activity was quickly achieved by washing the HRP/NPG/GCE bioelectrode using differential pulse voltammetry (DPV) technique in deaerated PBS (50 mM, pH 7.0) for only 60 s. Furthermore, the real sample analysis of sulfide by the HRP/NPG/GCE bioelectrode was achieved. Based on above results, the HRP/NPG/GCE bioelectrode could be a better choice for the real determination of sulfide compared to inhibitive biosensors previously reported.

Novel photoluminescence enzyme immunoassay based on supramolecular host-guest recognition using L-arginine/6-aza-2-thiothymine-stabilized gold nanocluster.

PubMed

Wang, Youmei; Lu, Minghua; Tang, Dianping

2018-06-30

A new photoluminescence (PL) enzyme immunoassay was designed for sensitive detection of aflatoxin B 1 (AFB 1 ) via an innovative enzyme substrate, 6-aza-2-thiothymine-stabilized gold nanocluster (AAT-AuNC) with L-arginine. The enzyme substrate with strong PL intensity was formed through supramolecular host-guest assembly between guanidine group of L-arginine and AAT capped on the surface of AuNC. Upon arginase introduction, the captured L-arginine was hydrolyzed into ornithine and urea, thus resulting in the decreasing PL intensity. Based on this principle, a novel competitive-type immunoreaction was first carried out on AFB 1 -bovine serum albumin (AFB 1 -BSA) conjugate-coated microplate, using arginase-labeled anti-AFB 1 antibody as the competitor. Under the optimum conditions, the PL intensity increased with the increment of target AFB 1 , and allowed the detection of the analyte at concentrations as low as 3.2 pg mL -1 (ppt). Moreover, L-arginine-AAT-AuNC-based PL enzyme immunoassay afforded good reproducibility and acceptable specificity. In addition, the accuracy of this methodology, referring to commercial AFB 1 ELISA kit, was evaluated to analyze naturally contaminated or spiked peanut samples, giving well-matched results between two methods, thus representing a useful scheme for practical application in quantitative monitoring of mycotoxins in foodstuff. Copyright © 2018 Elsevier B.V. All rights reserved.

Sputtered gold-coated ITO nanowires by alternating depositions from Indium and ITO targets for application in surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Setti, Grazielle O.; Mamián-López, Mónica B.; Pessoa, Priscila R.; Poppi, Ronei J.; Joanni, Ednan; Jesus, Dosil P.

2015-08-01

Indium Tin oxide (ITO) nanowires were deposited by RF sputtering over oxidized silicon using ITO and Indium targets. The nanowires grew on the substrate with a catalyst layer of Indium by the vapor-liquid-solid (VLS) mechanism. Modifications in the deposition conditions affected the morphology and dimensions of the nanowires. The samples, after being covered with gold, were evaluated as surface-enhanced Raman scattering (SERS) substrates for detection of dye solutions and very good intensifications of the Raman signal were obtained. The SERS performance of the samples was also compared to that of a commercial SERS substrate and the results achieved were similar. To the best of our knowledge, this is the first time ITO nanowires were grown by the sputtering technique using oxide and metal targets.

Direct Synthesis of Silicon Nanowires, Silica Nanospheres, Wire-Like Nanosphere Agglomerates, and Silica-Based Nanotubes and Nanofiber Arrays

DTIC Science & Technology

2001-01-01

decades, the vapor-liquid-solid (VLS) process, ’ 2 where gold particles act as a mediating solvent on a silicon substrate, forming a molten alloy, has...34Nanocatalysis: Selective Conversion of Ethanol to Acetaldehyde Using Monoatomically Dispersed Copper on Silica Nanospheres", Journal of Catalysis, submitted. 7.Sales literature, Cabot Corporation. C5.9.8 Nanoparticles in Biology

Toposelective electrochemical desorption of thiol SAMs from neighboring polycrystalline gold surfaces.

PubMed

Tencer, Michal; Berini, Pierre

2008-11-04

We describe a method for the selective desorption of thiol self-assembled monolayers from gold surfaces having micrometer-scale separations on a substrate. In an electrolyte solution, the electrical resistance between the adjacent areas can be much lower than the resistance between a surface and the counter electrode. Also, both reductive and oxidative thiol desorption may occur. Therefore, the potentials of the surfaces must be independently controlled with a multichannel potentiostat and operating windows for a given thiol/electrolyte system must be established. In this study operating windows were established for 1-dodecanethiol-based SAMs in phosphate buffer, phosphate-buffered saline, and sodium hydroxide solution, and selective SAM removal was successfully performed in a four-electrode configuration.

Functionalized gold nanostars for label-free detection of PKA phosphorylation using surface-enhanced Raman spectroscopy

NASA Astrophysics Data System (ADS)

He, Shuai; Kah, James C. Y.

2017-04-01

Protein phosphorylation controls fundamental biological processes. Dysregulation of protein kinase is associated with a series of human diseases including cancer. Protein kinase A (PKA) activity has been reported to serve as a potential prognostic marker for cancer. To this end, we developed a non-radioactive, rapid, cheap and robust scheme based on surface-enhanced Raman spectroscopy (SERS) for label-free detection of PKA phosphorylation using gold nanostars (AuNS) functionalized with BSA-kemptide. While bovine serum albumin (BSA) proteins stabilized the AuNS, kemptide, which is a high affinity substrate peptide specific for PKA, were phosphorylated in vitro to generate Raman signals that were identified by performing principal component analysis (PCA) on the acquired SERS spectra.

Simulation and analysis of Au-MgF2 structure in plasmonic sensor in near infrared spectral region

NASA Astrophysics Data System (ADS)

Sharma, Anuj K.

2018-05-01

Plasmonic sensor based on metal-dielectric combination of gold and MgF2 layers is studied in near infrared (NIR) spectral region. An emphasis is given on the effect of variable thickness of MgF2 layer in combination with operating wavelength and gold layer thickness on the sensor's performance in NIR. It is established that the variation in MgF2 thickness in connection with plasmon penetration depth leads to significant variation in sensor's performance. The analysis leads to a conclusion that taking smaller values of MgF2 layer thickness and operating at longer NIR wavelength leads to enhanced sensing performance. Also, fluoride glass can provide better sensing performance than chalcogenide glass and silicon substrate.

Large surface-enhanced Raman scattering from self-assembled gold nanosphere monolayers

NASA Astrophysics Data System (ADS)

Fontana, Jake; Livenere, John; Bezares, Francisco J.; Caldwell, Joshua D.; Rendell, Ronald; Ratna, Banahalli R.

2013-05-01

We demonstrate an average surface-enhanced Raman scattering enhancement on the order of 108 from benzenethiol molecules using self-assembled, macroscopic, and tunable gold nanosphere monolayers on non-templated substrates. The self-assembly of the nanosphere monolayers uses a simple and efficient technique that allows for the creation of a high-density, chemically functionalized gold nanosphere monolayers with enhancement factors comparable to those produced using top-down fabrication techniques. These films may provide an approach for the future development of portable chemical/biological sensors.

Gold(I)-catalyzed diazo cross-coupling: a selective and ligand-controlled denitrogenation/cyclization cascade.

PubMed

Xu, Guangyang; Zhu, Chenghao; Gu, Weijin; Li, Jian; Sun, Jiangtao

2015-01-12

An unprecedented gold-catalyzed ligand-controlled cross-coupling of diazo compounds by sequential selective denitrogenation and cyclization affords N-substituted pyrazoles in a position-switchable mode. This novel transformation features selective decomposition of one diazo moiety and simultaneous preservation of the other one from two substrates. Notably, the choice of the ancillary ligand to the gold complex plays a pivotal role on the chemo- and regioselectivity of the reactions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

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

Zhu, Jin; Li, Wenbin; Zhu, Mao

2014-03-15

The localized surface plasmon resonances (LSPRs) of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3°) crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis) spectroscopy, and atomic force microscopy (AFM). The results showed that the gold particle coverage decreases with increasing pH value of the gold colloid solution. This phenomenon demonstrates thatmore » self-assembled gold surfaces were formed via the electrostatic adsorption of gold particles on the positively charged, ionized amino groups on the crystal plates in the acidic solution. The spectrum of gold nanoparticles with different coverage degree on the crystal plates showed that the LSPR properties are highly dependent on pH.« less

Electrochemical annealing of nanoporous gold by application of cyclic potential sweeps

PubMed Central

Sharma, Abeera; Bhattarai, Jay K.; Alla, Allan J.; Demchenko, Alexei V.; Stine, Keith J.

2015-01-01

An electrochemical method for annealing the pore sizes of nanoporous gold is reported. The pore sizes of nanoporous gold can be increased by electrochemical cycling with the upper potential limit being just at the onset of gold oxide formation. This study has been performed in electrolyte solutions including potassium chloride, sodium nitrate and sodium perchlorate. Scanning electron microscopy images have been used for ligament and pore size analysis. We examine the modifications of nanoporous gold due to annealing using electrochemical impedance spectroscopy, and cyclic voltammetry and offer a comparison of the surface coverage using the gold oxide stripping method as well as the method in which electrochemically accessible surface area is determined by using a diffusing redox probe. The effect of additives adsorbed on the nanoporous gold surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in nanoporous gold are also reported. The effect of the annealing process on the application of nanoporous gold as a substrate for glucose electro-oxidation is briefly examined. PMID:25649027

Investigation on micro-patterned gold-plated polymer substrate for a micro hydraulic actuator

NASA Astrophysics Data System (ADS)

Sundaresan, Vishnu Baba; Akle, Barbar; Leo, Donald J.

2006-03-01

Plants have the ability to develop large mechanical force from chemical energy available with bio-fuels. The energy released by the cleavage of a terminal phosphate ion during the hydrolysis of a bio-fuel assists the transport of ions and fluids in cellular homeostasis. Materials that develop pressure and hence strain similar to the response of plants to an external stimuli are classified as nastic materials. This new class of actuators use protein transporters as functional units to move species and result in deformation [Leo et al 2005 (Proceedings of IMECE - 06)]. The ion transporters are hydrocarbons which are formed across the cellular membranes. The membranes that house the ion transporters are aggregates of phospholipids rigidized by cytoskeleton. Reconstituting these nano-machines on a harder matrix is quintessential to build a functional device. Artificial phospholipid membranes or Biliayer lipid membranes (BLM) have poor structural integrity and do not adhere to most surfaces. Patterned arrays of pores made on Poly-propylene glycol-diacrylate (PPG-DA) substrate, a photo curable polymer was made available to us for initial design iterations for an actuator. Hydrophobicity of PPG-DA posed initial problems to support a BLM. We modified the surface of micropatterned PPG-DA membrane by gold plating it. The surface of the porous PPG-DA membranes was plated with gold (Au). A 10nm seeding layer of Au was sputtered on the surface of the membrane. Further gold was reduced onto the sputtered gold surface [Supriya et al(Langmuir 2004, 20, 8870-8876)] by suspending the samples in a solution of hydroxylamine and Hydrogen tetrachloroaurate(III) trihydrate [HAuCl4.3H2O]. This reduction process increased the thickness of the gold, enhanced its adhesion to the PPG-DA substrate and improved the shapes of the pores. This surface modification of PPG-DA helped us form stable BLM with 1-Palmitoyl-2-Oleoyl-sn-Glycero-3- [Phospho-L-Serine] (Sodium Salt) (POPS), 1-Palmitoyl-2-Oleoyl-sn-Glycero- 3-Phosphoethanolamine (POPE) lipids. The observed ionic resistance of the BLM remained stable and sustained 4 mm water column for the the four hours observation period. This article describes the procedure we adopted to modify the PPG-DA substrate, form a BLM and the procedure to quantify the stability of the BLM formed with -amine and -thiol head groups in the lipids.

Influence of ionic strength and surfactant concentration on electrostatic surfacial assembly of cetyltrimethylammonium bromide-capped gold nanorods on fully immersed glass.

PubMed

Ferhan, Abdul Rahim; Guo, Longhua; Kim, Dong-Hwan

2010-07-20

The effect of ionic strength as well as surfactant concentration on the surface assembly of cetyltrimethylammonium bromide (CTAB)-capped gold nanorods (GNRs) has been studied. Glass substrates were modified to yield a net negative charge through electrostatic coating of polystyrenesulfonate (PSS) over a self-assembled monolayer (SAM) of positively charged aminopropyltriethoxysilane (APTS). The substrates were then fully immersed in GNR solutions at different CTAB concentrations and ionic strengths. Under slightly excess CTAB concentrations, it was observed that the density of GNRs immobilized on a substrate was predictably tunable through the adjustment of NaCl concentration over a wide range. Motivated by the experimental observation, we hypothesize that electrostatic shielding of charges around the GNRs affects the density of GNR immobilization. This model ultimately explains that at moderate to high CTAB concentrations a second electrostatic shielding effect contributed by excess CTAB molecules occurs, resulting in a parabolic trend of nanorod surface density when ionic strength is continually increased. In contrast, at a low CTAB concentration, the effect of ionic strength becomes much less significant due to insufficient CTAB molecules to provide for the second electrostatic shielding effect. The tunability of electrostatic-based surface assembly of GNRs enables the attainment of a dense surface assembly of nanorods without significant removal of CTAB or any other substituted stabilizing agent, both of which could compromise the stability and morphology of GNRs in solution. An additional study performed to investigate the robustness of such electrostatic-based surface assembly also proved its reliability to be used as biosensing platforms.

Improved Adhesion of Gold Thin Films Evaporated on Polymer Resin: Applications for Sensing Surfaces and MEMS

PubMed Central

Moazzez, Behrang; O'Brien, Stacey M.; Merschrod S., Erika F.

2013-01-01

We present and analyze a method to improve the morphology and mechanical properties of gold thin films for use in optical sensors or other settings where good adhesion of gold to a substrate is of importance and where controlled topography/roughness is key. To improve the adhesion of thermally evaporated gold thin films, we introduce a gold deposition step on SU-8 photoresist prior to UV exposure but after the pre-bake step of SU-8 processing. Shrinkage and distribution of residual stresses, which occur during cross-linking of the SU-8 polymer layer in the post-exposure baking step, are responsible for the higher adhesion of the top gold film to the post-deposition cured SU-8 sublayer. The SU-8 underlayer can also be used to tune the resulting gold film morphology. Our promoter-free protocol is easily integrated with existing sensor microfabrication processes. PMID:23760086

Iodide-induced organothiol desorption and photochemical reaction, gold nanoparticle (AuNP) fusion, and SERS signal reduction in organothiol-containing AuNP aggregates

USDA-ARS?s Scientific Manuscript database

Gold nanoparticles (AuNPs) have been used extensively as surface-enhanced Raman spectroscopic (SERS) substrates for their large SERS enhancements and widely believed chemical stability. Presented is the finding that iodide can rapidly reduce the SERS intensity of the ligands, including organothiols ...

Aqueous Black Colloids of Reticular Nanostructured Gold

NASA Astrophysics Data System (ADS)

Stanca, S. E.; Fritzsche, W.; Dellith, J.; Froehlich, F.; Undisz, A.; Deckert, V.; Krafft, C.; Popp, J.

2015-01-01

Since ancient times, noble gold has continuously contributed to several aspects of life from medicine to electronics. It perpetually reveals its new features. We report the finding of a unique form of gold, reticular nanostructured gold (RNG), as an aqueous black colloid, for which we present a one-step synthesis. The reticules consist of gold crystals that interconnect to form compact strands. RNG exhibits high conductivity and low reflection, and these features, coupled with the high specific surface area of the material, could prove valuable for applications in electronics and catalysis. Due to high absorption throughout the visible and infrared domain, RNG has the potential to be applied in the construction of sensitive solar cells or as a substrate for Raman spectroscopy.

Fabrication of novel plasmonics-active substrates

NASA Astrophysics Data System (ADS)

Dhawan, Anuj; Gerhold, Michael; Du, Yan; Misra, Veena; Vo-Dinh, Tuan

2009-02-01

This paper describes methodologies for fabricating of highly efficient plasmonics-active SERS substrates - having metallic nanowire structures with pointed geometries and sub-5 nm gap between the metallic nanowires enabling concentration of high EM fields in these regions - on a wafer-scale by a reproducible process that is compatible with large-scale development of these substrates. Excitation of surface plasmons in these nanowire structures leads to substantial enhancement in the Raman scattering signal obtained from molecules lying in the vicinity of the nanostructure surface. The methodologies employed included metallic coating of silicon nanowires fabricated by employing deep UV lithography as well as controlled growth of silicon germanium on silicon nanostructures to form diamond-shaped nanowire structures followed by metallic coating. These SERS substrates were employed for detecting chemical and biological molecules of interest. In order to characterize the SERS substrates developed in this work, we obtained SERS signals from molecules such as p-mercaptobenzoic acid (pMBA) and cresyl fast violet (CFV) attached to or adsorbed on the metal-coated SERS substrates. It was observed that both gold-coated triangular shaped nanowire substrates as well as gold-coated diamond shaped nanowire substrates provided very high SERS signals for the nanowires having sub-15 nm gaps and that the SERS signal depends on the closest spacing between the metal-coated silicon and silicon germanium nanowires. SERS substrates developed by the different processes were also employed for detection of biological molecules such as DPA (Dipicolinic Acid), an excellent marker for spores of bacteria such as Anthrax.

Synthesis of gold nanoparticles with graphene oxide.

PubMed

Wang, Wenshuo; He, Dawei; Zhang, Xiqing; Duan, Jiahua; Wu, Hongpeng; Xu, Haiteng; Wang, Yongsheng

2014-05-01

Single sheets of functionalized graphene oxide are derived through chemical exfoliation of natural flake graphite. We present an effective synthetic method of graphene-gold nanoparticles hybrid nanocomposites. AFM (Atomic Force Microscope) was used to measure the thickness of the individual GO nanosheet. FTIR (Fourier transform infrared) spectroscopy was used to verify the attachment of oxygen functionalities on the surface of graphene oxide. TEM (Transmission Electron Microscope) data revealed the average diameters of the gold colloids and characterized the composite particles situation. Absorption spectroscopy showed that before and after synthesis the gold particle size did not change. Our studies indicate that the hybrid is potential substrates for catalysts and biosensors.

SERS-Active Nanoinjector for Intracellular Spectroscopy

NASA Astrophysics Data System (ADS)

Vitol, Elina; Orynbayeva, Zulfiya; Bouchard, Michael; Azizkhan-Clifford, Jane; Friedman, Gary; Gogotsi, Yury

2009-03-01

We developed a multifunctional nanopipette which allows simultaneous cell injection and intacellular surface-enhanced Raman spectroscopy (SERS) analysis. SERS spectra contain the characteristic frequencies of molecular bond vibrations. This is a unique method for studying cell biochemistry and physiology on a single organelle level. Unlike the fluorescence spectroscopy, it does not require any specific staining. The principle of SERS is based on very large electromagnetic field enhancement localized around a nano-rough metallic surface. Gold colloids are widely used SERS substrates. Previously, the colloidal nanoparticles were introduced into a cell by the mechanism of endocytosis. The disadvantage of this method is the uncontrollable aggregation and distribution of gold nanoparticles inside a cell which causes a significant uncertainty in the origin of the acquired data. At the same time, the nanoparticle uptake is irreversible. We present a SERS-active nanoinjector, coated with gold nanoparticles, which enables selective signal acquisition from any point-of-interest inside a cell. The nanoinjector provides a highly localized SERS signal with sub-nanometer resolution in real time.

Gold-Coated M13 Bacteriophage as a Template for Glucose Oxidase Biofuel Cells with Direct Electron Transfer.

PubMed

Blaik, Rita A; Lan, Esther; Huang, Yu; Dunn, Bruce

2016-01-26

Glucose oxidase-based biofuel cells are a promising source of alternative energy for small device applications, but still face the challenge of achieving robust electrical contact between the redox enzymes and the current collector. This paper reports on the design of an electrode consisting of glucose oxidase covalently attached to gold nanoparticles that are assembled onto a genetically engineered M13 bacteriophage using EDC-NHS chemistry. The engineered phage is modified at the pIII protein to attach onto a gold substrate and serves as a high-surface-area template. The resulting "nanomesh" architecture exhibits direct electron transfer (DET) and achieves a higher peak current per unit area of 1.2 mA/cm(2) compared to most other DET attachment schemes. The final enzyme surface coverage on the electrode was calculated to be approximately 4.74 × 10(-8) mol/cm(2), which is a significant improvement over most current glucose oxidase (GOx) DET attachment methods.

Tunable Electromagnetic Coupling in Plasmonic Nanostructures Mediated by Thermoresponsive Polymer Brushes.

PubMed

Nguyen, Mai; Kanaev, Andrei; Sun, Xiaonan; Lacaze, Emmanuelle; Lau-Truong, Stéphanie; Lamouri, Aazdine; Aubard, Jean; Felidj, Nordin; Mangeney, Claire

2015-11-24

A smart and highly SERS-active plasmonic platform was designed by coupling regular arrays of nanotriangles to colloidal gold nanorods via a thermoresponsive polymer spacer (poly(N-isopropylacrylamide), PNIPAM). The substrates were prepared by combining a top-down and a bottom-up approach based on nanosphere lithography, surface-initiated controlled radical polymerization, and colloidal assembly. This multistep strategy provided regular hexagonal arrays of nanotriangles functionalized by polymer brushes and colloidal gold nanorods, confined exclusively on the nanotriangle surface. Interestingly, one could finely tune the gold nanorod impregnation on the polymer-coated nanostructures by adjusting the polymer layer thickness, leading to highly coupled plasmonic systems for intense SERS signal. Moreover, the thermoresponsive properties of the PNIPAM brushes could be wisely handled in order to monitor the SERS activity of the nanostructures coupled via this polymer spacer. The coupled hybrid plasmonic nanostructures designed in this work are therefore very promising smart platforms for the sensitive detection of analytes by SERS.

Platinum nanoparticles decorated dendrite-like gold nanostructure on glassy carbon electrodes for enhancing electrocatalysis performance to glucose oxidation

NASA Astrophysics Data System (ADS)

Jia, Hongmei; Chang, Gang; Lei, Ming; He, Hanping; Liu, Xiong; Shu, Honghui; Xia, Tiantian; Su, Jie; He, Yunbin

2016-10-01

Platinum nanoparticles decorated dendrite-like gold nanostructure, bimetal composite materials on glassy carbon electrode (Pt/DGNs/GC) for enhancing electrocatalysis to glucose oxidation was designed and successfully fabricated by a facile two-step deposition method without any templates, surfactants, or stabilizers. Dendrite-like gold nanostructure was firstly deposited on the GC electrode via the potentiostatic method, and then platinum nanoparticles were decorated on the surface of gold substrate through chemical reduction deposition. X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the evolution of morphology and structure of the as-prepared Pt/DGNs/GC. Based on electrochemical measurements such as cyclic voltammetry, linear voltammetry and chronoamperometry, Pt/DGNs/GC exhibited significantly enhanced electrocatalytic performance to glucose oxidation compared those of pure dendrite-like Au nanoparticles in our previous report. Controlling chemical reduction deposition time, the amount of platinum nanoparticles on Au surface could be regulated, which further tuned electrocatalytic properties toward glucose oxidation. The dendrite-like gold surface partially covered by platinum nanoparticles dramatically enhanced the electrocatalytic performance for the oxidation of glucose because of excellent synergetic effects between gold and platinum species and the increased electrochemical active area from Pt nanoparticles loading. The non-enzymatic glucose biosensor based on Pt/DGNs/GC showed a rapid respond time (within 2 s), wide linear range (from 0.1 mM to 14 mM), low detection limit (0.01 mM), supernal sensitivity (275.44 μA cm-2 mM-1, R = 0.993), satisfactory reproducibility and good stability for glucose sensing. It was demonstrated that Pt/DGNs/GC could work as promising candidate for factual non-enzymatic glucose detection.

Scanning Probe Platform | Materials Science | NREL

Science.gov Websites

level; this image obtained using a scanning tunneling microscope shows gray and white clusters of produce high-resolution color images or maps like this one obtained using scanning tunneling luminescence gray clusters. Gold substrate: (Left) STM image reveals the terraces of the H2 flamed substrate. (Right

A short review on thermosonic flip chip bonding

NASA Astrophysics Data System (ADS)

Suppiah, Sarveshvaran; Ong, Nestor Rubio; Sauli, Zaliman; Sarukunaselan, Karunavani; Alcain, Jesselyn Barro; Shahimin, Mukhzeer Mohamad; Retnasamy, Vithyacharan

2017-09-01

This review is to study the evolution and key findings, critical technical challenges, solutions and bonding equipment of thermosonic flip chip bonding. Based on the review done, it was found that ultrasonic power, bonding time and force are the three main critical parameters need to be optimized in order to achieve sound and reliable bonding between the die and substrate. A close monitoring of the ultrasonic power helped to prevent over bonding phenomena on flexible substrate. Gold stud bumping is commonly used in thermosonic bonding compared to solder due to its better reliability obtained in the LED and optoelectronic packages. The review comprised short details on the available thermosonic bonding equipment in the semiconductor industry as well.

Electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7 - delta interfaces as studied by photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Dessau, D. S.; Shen, Z.-X.; Wells, B. O.; Spicer, W. E.; List, R. S.; Arko, A. J.; Bartlett, R. J.; Fisk, Z.; Cheong, S.-W.; Mitzi, D. B.; Kapitulnik, A.; Schirber, J. E.

1990-07-01

High-resolution photoemission has been used to probe the electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7-δ interface formed by a low-temperature (20 K) gold evaporation on cleaved high quality single crystals. We find that the metallicity of the EuBa2Cu3O7-δ substrate in the near surface region (˜5 Å) is essentially destroyed by the gold deposition, while the near surface region of Bi2Sr2CaCu2O8 remains metallic. This has potentially wide ranging consequences for the applicability of the different types of superconductors in real devices.

Biomedical Applications of Micro-Raman and Surface-Enhanced Raman Scattering (SERS) Technology

DTIC Science & Technology

2012-10-01

to be an effective media for PSA capture. For SERS-based immunoassays, nitrocellulose offers comparable results to those obtained using gold-coated...glass substrates while offering a more cost- effective and time-saving method of detecting minute amounts of PSA; (ii) Micro-Raman imaging...technology was found to be effective in chemical mapping of arteries in the tissues of a post mortem individual whose cause of death was a cardiac event

Interfacial chemistry of a perfluoropolyether lubricant studied by X-ray photoelectron spectroscopy and temperature desorption spectroscopy

NASA Technical Reports Server (NTRS)

Herrera-Fierro, Pilar; Jones, William R., Jr.; Pepper, Stephen V.

1993-01-01

The interfacial chemistry of Fomblin Z25, a commercial perfluoropolyether used as lubricant for space applications was studied with different metallic surfaces: 440C steel, gold, and aluminum. Thin layers of Fomblin Z25 were evaporated onto the oxide-free substrates, and the interfacial chemistry was studied using XPS and TDS. The reactions were induced by heating the substrate and by rubbing the substrate with a steel ball. Gold was found to be completely unreactive towards Fomblin at any temperature. Reaction at room temperature was observed only in the case of the aluminum substrate, the most reactive towards Fomblin Z25 of the substrates studied. It was necessary to heat the 440C steel substrate to 190 C to induce decomposition of the fluid. The degradation of the fluid was indicated by the formation of a debris layer at the interface. This debris layer, composed of inorganic and organic reaction products, when completely formed, passivated the surface from further attack to the Fromblin on top. The tribologically induced reactions on 440C steel formed a debris layer of similar chemical characteristics to the thermally induced layer. In all cases, the degradation reaction resulted in preferential consumption of the difluoroformyl carbon (-OCF2O-).

Electron transport in gold colloidal nanoparticle-based strain gauges.

PubMed

Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

2013-03-08

A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the 'regular island array model' that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy E(C). This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the E(C) values of these 14 nm NPs cannot be neglected in determining the β values.

Electron transport in gold colloidal nanoparticle-based strain gauges

NASA Astrophysics Data System (ADS)

Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M.; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

2013-03-01

A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the ‘regular island array model’ that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy EC. This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the EC values of these 14 nm NPs cannot be neglected in determining the β values.

Coordination-based gold nanoparticle layers.

PubMed

Wanunu, Meni; Popovitz-Biro, Ronit; Cohen, Hagai; Vaskevich, Alexander; Rubinstein, Israel

2005-06-29

Gold nanoparticle (NP) mono- and multilayers were constructed on gold surfaces using coordination chemistry. Hydrophilic Au NPs (6.4 nm average core diameter), capped with a monolayer of 6-mercaptohexanol, were modified by partial substitution of bishydroxamic acid disulfide ligand molecules into their capping layer. A monolayer of the ligand-modified Au NPs was assembled via coordination with Zr4+ ions onto a semitransparent Au substrate (15 nm Au, evaporated on silanized glass and annealed) precoated with a self-assembled monolayer of the bishydroxamate disulfide ligand. Layer-by-layer construction of NP multilayers was achieved by alternate binding of Zr4+ ions and ligand-modified NPs onto the first NP layer. Characterization by atomic force microscopy (AFM), ellipsometry, wettability, transmission UV-vis spectroscopy, and cross-sectional transmission electron microscopy showed regular growth of NP layers, with a similar NP density in successive layers and gradually increased roughness. The use of coordination chemistry enables convenient step-by-step assembly of different ligand-possessing components to obtain elaborate structures. This is demonstrated by introducing nanometer-scale vertical spacing between a NP layer and the gold surface, using a coordination-based organic multilayer. Electrical characterization of the NP films was carried out using conductive AFM, emphasizing the barrier properties of the organic spacer multilayer. The results exhibit the potential of coordination self-assembly in achieving highly controlled composite nanostructures comprising molecules, NPs, and other ligand-derivatized components.

Direct synthesis and morphological characterization of gold-dendrimer nanocomposites prepared using PAMAM succinamic acid dendrimers: preliminary study of the calcification potential.

PubMed

Vasile, E; Serafim, A; Petre, D; Giol, D; Dubruel, P; Iovu, H; Stancu, I C

2014-01-01

Gold-dendrimer nanocomposites were obtained for the first time by a simple colloidal approach based on the use of polyamidoamine dendrimers with succinamic acid terminal groups and dodecanediamine core. Spherical and highly crystalline nanoparticles with dimensions between 3 nm and 60 nm, and size-polydispersity depending on the synthesis conditions, have been generated. The influence of the stoichiometric ratio and the structural and architectural features of the dendrimers on the properties of the nanocomposites has been described. The self-assembling behaviour of these materials produces gold-dendrimer nanostructured porous networks with variable density, porosity, and composition. The investigations of the reaction systems, by TEM, at two postsynthesis moments, allowed to preliminary establish the control over the properties of the nanocomposite products. Furthermore, this study allowed better understanding of the mechanism of nanocomposite generation. Impressively, in the early stages of the synthesis, the organization of gold inside the dendrimer molecules has been evidenced by micrographs. Growth and ripening mechanisms further lead to nanoparticles with typical characteristics. The potential of such nanocomposite particles to induce calcification when coating a polymer substrate was also investigated.

Direct Synthesis and Morphological Characterization of Gold-Dendrimer Nanocomposites Prepared Using PAMAM Succinamic Acid Dendrimers: Preliminary Study of the Calcification Potential

PubMed Central

Vasile, E.; Serafim, A.; Petre, D.; Giol, D.; Dubruel, P.; Iovu, H.; Stancu, I. C.

2014-01-01

Gold-dendrimer nanocomposites were obtained for the first time by a simple colloidal approach based on the use of polyamidoamine dendrimers with succinamic acid terminal groups and dodecanediamine core. Spherical and highly crystalline nanoparticles with dimensions between 3 nm and 60 nm, and size-polydispersity depending on the synthesis conditions, have been generated. The influence of the stoichiometric ratio and the structural and architectural features of the dendrimers on the properties of the nanocomposites has been described. The self-assembling behaviour of these materials produces gold-dendrimer nanostructured porous networks with variable density, porosity, and composition. The investigations of the reaction systems, by TEM, at two postsynthesis moments, allowed to preliminary establish the control over the properties of the nanocomposite products. Furthermore, this study allowed better understanding of the mechanism of nanocomposite generation. Impressively, in the early stages of the synthesis, the organization of gold inside the dendrimer molecules has been evidenced by micrographs. Growth and ripening mechanisms further lead to nanoparticles with typical characteristics. The potential of such nanocomposite particles to induce calcification when coating a polymer substrate was also investigated. PMID:24600316

Photothermal inactivation of bacteria on plasmonic nanostructures

NASA Astrophysics Data System (ADS)

Santos, Greggy M.; Ibañez de Santi Ferrara, Felipe; Zhao, Fusheng; Rodrigues, Debora F.; Shih, Wei-Chuan

2016-03-01

Hospital-acquired bacterial infections are frequently associated with the pathogenic biofilms on surfaces of devices and instruments used in medical procedures. The utilization of thermal plasmonic agents is an innovative approach for sterilizing hospital equipment and for in vivo therapeutic treatment of bacterial infection. A photothermal inactivation technique via array of nanoporous gold disks (NPGDs) has been developed by irradiating near infrared (NIR) light onto deposited bacterial cells (Escherichia coli, Bacillus subtilis, Exiguobacterium AT1B) on the surface of metal nanostructure. The physical and photothermal properties of the NPGD substrate were investigated using topographical scanning electron microscopy (SEM) and thermographic infrared imaging. Bacterial viability studies on NPGD substrates irradiated with and without NIR light were evaluated using a fluorescence-based two-component stain assay. The results show that the heat generated from the NPGD substrate promotes high cell death counts (~100%) at short exposure durations (<25 s) even for thermally-resistant bacterial strains. The photothermal effects on NPGD substrate can lead to point-of-care applications.

The ZnO-FET Biosensor for Cardiac Troponin I

NASA Astrophysics Data System (ADS)

Fathil, M. F. M.; Arshad, M. K. Md; Nuzaihan, M. N. M.; Gopinath, Subash C. B.; Ruslinda, A. R.; Hashim, U.

2018-03-01

This paper investigates the influence of substrate-gate coupling on the ZnO-FET biosensor’s sensitivity for detection of cardiac troponin I (cTnI), a ‘gold standard’ biomarker for acute myocardial infarction (AMI). The FET-based device with introduction of substrate-gate coupling on p-type silicon-on-insulator (SOI) substrate is fabricated using conventional lithography processes. An n-type zinc oxide (ZnO) thin film deposited via electron-beam evaporator is used as transducer for bridging the source and drain regions. Surface modifications via functionalization with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA) as chemical linkers, followed by immobilization of cTnI monoclonal antibody (MAb-cTnI) as bio-receptor on the ZnO thin film allow different concentration of cTnI detection with high selectivity. The device’s sensitivity increases up to 9 %·(g/ml)-1 with the increase of the substrate-gate voltage (VSG) up to -10 V at very low limit of detection (LOD) down to 1.6 fg/ml.

Surface-engineered substrates for improved human pluripotent stem cell culture under fully defined conditions.

PubMed

Saha, Krishanu; Mei, Ying; Reisterer, Colin M; Pyzocha, Neena Kenton; Yang, Jing; Muffat, Julien; Davies, Martyn C; Alexander, Morgan R; Langer, Robert; Anderson, Daniel G; Jaenisch, Rudolf

2011-11-15

The current gold standard for the culture of human pluripotent stem cells requires the use of a feeder layer of cells. Here, we develop a spatially defined culture system based on UV/ozone radiation modification of typical cell culture plastics to define a favorable surface environment for human pluripotent stem cell culture. Chemical and geometrical optimization of the surfaces enables control of early cell aggregation from fully dissociated cells, as predicted from a numerical model of cell migration, and results in significant increases in cell growth of undifferentiated cells. These chemically defined xeno-free substrates generate more than three times the number of cells than feeder-containing substrates per surface area. Further, reprogramming and typical gene-targeting protocols can be readily performed on these engineered surfaces. These substrates provide an attractive cell culture platform for the production of clinically relevant factor-free reprogrammed cells from patient tissue samples and facilitate the definition of standardized scale-up friendly methods for disease modeling and cell therapeutic applications.

Maskless writing of a flexible nanoscale transistor with Au-contacted carbon nanotube electrodes

NASA Astrophysics Data System (ADS)

Dockendorf, Cedric P. R.; Poulikakos, Dimos; Hwang, Gilgueng; Nelson, Bradley J.; Grigoropoulos, Costas P.

2007-12-01

A flexible polymer field effect transistor with a nanoscale carbon nanotube channel is conceptualized and realized herein. Carbon nanotubes (CNTs) were dispersed on a polyimide substrate and marked in an scanning electron microscope with focused ion beam such that they could be contacted with gold nanoink. The CNTs were divided into two parts forming the source and drain of the transistor. A micropipette writing method was used to contact the carbon nanotube electrodes with gold nanoink and to deposit the poly(3-hexylthiophene) as an active layer. The mobility of the transistors is of the order of 10-5cm/Vs. After fabrication, the flexible transistors can be peeled off the substrate.

Particle-Film Plasmons on Periodic Silver Film over Nanosphere (AgFON): A Hybrid Plasmonic Nanoarchitecture for Surface-Enhanced Raman Spectroscopy.

PubMed

Lee, Jiwon; Zhang, Qianpeng; Park, Seungyoung; Choe, Ayoung; Fan, Zhiyong; Ko, Hyunhyub

2016-01-13

Plasmonic systems based on particle-film plasmonic couplings have recently attracted great attention because of the significantly enhanced electric field at the particle-film gaps. Here, we introduce a hybrid plasmonic architecture utilizing combined plasmonic effects of particle-film gap plasmons and silver film over nanosphere (AgFON) substrates. When gold nanoparticles (AuNPs) are assembled on AgFON substrates with controllable particle-film gap distances, the AuNP-AgFON system supports multiple plasmonic couplings from interparticle, particle-film, and crevice gaps, resulting in a huge surface-enhanced Raman spectroscopy (SERS) effect. We show that the periodicity of AgFON substrates and the particle-film gaps greatly affects the surface plasmon resonances, and thus, the SERS effects due to the interplay between multiple plasmonic couplings. The optimally designed AuNP-AgFON substrate shows a SERS enhancement of 233 times compared to the bare AgFON substrate. The ultrasensitive SERS sensing capability is also demonstrated by detecting glutathione, a neurochemical molecule that is an important antioxidant, down to the 10 pM level.

Activation of an intense near band edge emission from ZnTe/ZnMgTe core/shell nanowires grown on silicon.

PubMed

Wojnar, P; Szymura, M; Zaleszczyk, W; Kłopotowski, L; Janik, E; Wiater, M; Baczewski, L T; Kret, S; Karczewski, G; Kossut, J; Wojtowicz, T

2013-09-13

The absence of luminescence in the near band edge energy region of Te-anion based semiconductor nanowires grown by gold catalyst assisted molecular beam epitaxy has strongly limited their applications in the field of photonics. In this paper, an enhancement of the near band edge emission intensity from ZnTe/ZnMgTe core/shell nanowires grown on Si substrates is reported. A special role of the use of Si substrates instead of GaAs substrates is emphasized, which results in an increase of the near band edge emission intensity by at least one order of magnitude accompanied by a simultaneous reduction of the defect related luminescence. A possible explanation of this effect relies on the presence of Ga-related deep level defects in structures grown on GaAs substrates, which are absent when Si substrates are used. Monochromatic mapping of the cathodoluminescence clearly confirms that the observed emission originates, indeed, from the ZnTe/ZnMgTe core/shell nanowires, whereas individual objects are studied by means of microphotoluminescence.

Plasmon-organic fiber interactions in diamond-like carbon coated nanostructured gold films

NASA Astrophysics Data System (ADS)

Cielecki, Paweł Piotr; Sobolewska, Elżbieta Karolina; Kostiuočenko, Oksana; Leißner, Till; Tamulevičius, Tomas; Tamulevičius, Sigitas; Rubahn, Horst-Günter; Adam, Jost; Fiutowski, Jacek

2017-11-01

Gold is the most commonly used plasmonic material, however soft and prone to mechanical deformations. It has been shown that the durability of gold plasmonic substrates can be improved by applying a protective diamond-like carbon (DLC) coating. In this work, we investigate the influence of such protective layers on plasmonic interactions in organic-plasmonic hybrid systems. We consider systems, consisting of 1-Cyano-quaterphenylene nanofibers on top of gold nano-square plasmonic arrays, coated with protective layers of varying thickness. We numerically investigate the spectral position of surface plasmon polariton resonances and electric field intensity, as a function of protective layer thickness, using the finite-difference time-domain method. To confirm the numerically indicated field enhancement preservation on top of protective layers, we experimentally map the second harmonic response of organic nanofibers. Subsequently, we characterize the plasmonic coupling between organic nanofibers and underlying substrates, considered as one of the main loss channels for photoluminescence from nanofibers, by time-resolved photoluminescence spectroscopy. Our findings reveal that, for the investigated system, plasmonic interactions are preserved for DLC coatings up to 55 nm. This is relevant for the fabrication of new passive and active plasmonic components with increased durability and hence prolonged lifetime.

Changing gears from chemical adhesion of cells to flat substrata toward engulfment of micro-protrusions by active mechanisms

NASA Astrophysics Data System (ADS)

Hai, Aviad; Kamber, Dotan; Malkinson, Guy; Erez, Hadas; Mazurski, Noa; Shappir, Joseph; Spira, Micha E.

2009-12-01

Microelectrode arrays increasingly serve to extracellularly record in parallel electrical activity from many excitable cells without inflicting damage to the cells by insertion of microelectrodes. Nevertheless, apart from rare cases they suffer from a low signal to noise ratio. The limiting factor for effective electrical coupling is the low seal resistance formed between the plasma membrane and the electronic device. Using transmission electron microscope analysis we recently reported that cultured Aplysia neurons engulf protruding micron size gold spines forming tight apposition which significantly improves the electrical coupling in comparison with flat electrodes (Hai et al 2009 Spine-shaped gold protrusions improve the adherence and electrical coupling of neurons with the surface of micro-electronic devices J. R. Soc. Interface 6 1153-65). However, the use of a transmission electron microscope to measure the extracellular cleft formed between the plasma membrane and the gold-spine surface may be inaccurate as chemical fixation may generate structural artifacts. Using live confocal microscope imaging we report here that cultured Aplysia neurons engulf protruding spine-shaped gold structures functionalized by an RGD-based peptide and to a significantly lesser extent by poly-l-lysine. The cytoskeletal elements actin and associated protein cortactin are shown to organize around the stalks of the engulfed gold spines in the form of rings. Neurons grown on the gold-spine matrix display varying growth patterns but maintain normal electrophysiological properties and form functioning synapses. It is concluded that the matrices of functionalized gold spines provide an improved substrate for the assembly of neuro-electronic hybrids.

A New-Type of Long-Range Restructuring of Ordered Metal Surfaces Induced by Lateral Adsorbate Interactions: Iodide on AU(110) Electrodes

DTIC Science & Technology

1994-02-01

separated by monoatomic steps. The direction of the (110) gold rows is evident in the atomic- resolution image of a uniform terrace, shown in Fig. 2A...distinguish between the average surface energy of a gold atom within a (110) terrace and at a monoatomic step (edge) site. The difference between these...having (3 x 2) symmetry (coverage - 0.67), is imaged instead of the substrate, with the iodide arranged in parallel close-packed rows in between the gold

Surface-enhanced infrared absorption spectroscopy of cytosine using gold film deposited on CaF2 substrate

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Thomas, S.; Tokas, R. B.; Padma, N.; Kshirsagar, R. J.

2018-04-01

Surface-enhanced infrared absorption (SEIRA) studies of cytosine adsorbed on the thermally evaporated gold film on CaF2 have been carried out in transmission mode. SEIRA spectrum down to 0.1 µM was observed owing to the plasmonic effect of the gold nano film. Cytosine molecules appear to adsorb on the film via C=O and NH groups as evidenced by the red shift observed in the stretching vibrations of the above groups. The molecules assume a perpendicular orientation with respect to the surface.

Experimental and DFT studies of gold nanoparticles supported on MgO(111) nano-sheets and their catalytic activity.

PubMed

Li, Zhi; Ciobanu, Cristian V; Hu, Juncheng; Palomares-Báez, Juan-Pedro; Rodríguez-López, José-Luis; Richards, Ryan

2011-02-21

A wet chemical preparation of MgO with the (111) facet as the primary surface has recently been reported and with alternating layers of oxygen anions and magnesium cations, this material shows unique chemical and physical properties. The potential to utilize the MgO(111) surface for the immobilization of metal particles is intriguing because the surface itself offers a very different environment for the metal particle with an all oxygen interface, as opposed to the typical (100) facet that possesses alternating oxygen anion and magnesium cation sites on the surface. Gold nanoparticles have demonstrated a broad range of interesting catalytic properties, but are often susceptible to aggregation at high temperatures and are very sensitive to substrate effects. Here, we investigate gold-supported on MgO(111) nanosheets as a catalyst system for the aerobic oxidation of benzyl alcohol. Gold nanoparticles deposited on MgO(111) show an increased level of activity in the solvent-free benzyl alcohol aerobic oxidation as compared to gold nanoparticles deposited on a typical MgO aerogel. TEM studies reveal that the gold nanoparticles have a hemispherical shape while sitting on the main surface of MgO(111) nanosheets, with a large Au-MgO interface. Given that the gold nanoparticles deposited on the two types of MgO have similar size, and that the two types of unmodified MgO show almost the same activities in the blank reaction, we infer that the high activity of Au/MgO(111) is due to the properties of the (111) support and/or those of the gold-support interface. To understand the binding of Au on low-index MgO surfaces and the charge distribution at the surface of the support, we have performed density functional theory (DFT) calculations on all low-index MgO substrates (with and without gold), using a model Au(10) cluster. Due to similar lattice constants of Au(111) and MgO(111) planes, the Au cluster retains its structural integrity and binds strongly on MgO(111) with either oxygen or magnesium termination. Furthermore, we have found that for the (001) and (110) substrates the charges of the ions in the top surface layer have similar values as in bulk MgO, but that on (111) surfaces these charges are significantly different. This difference in surface charge determines the direction of the electronic transfer upon adsorption of gold, such transfer occurring so as to restore the bulk MgO charge values. Using the results from theoretical calculations, we provide an explanation of our observations of increased catalytic activity in the case of the Au/MgO(111) system.

Surface plasmon dispersion engineering via double-metallic AU/AG layers for nitride light-emitting diodes

DOEpatents

Tansu, Nelson; Zhao, Hongping; Zhang, Jing; Liu, Guangyu

2014-04-01

A double-metallic deposition process is used whereby adjacent layers of different metals are deposited on a substrate. The surface plasmon frequency of a base layer of a first metal is tuned by the surface plasmon frequency of a second layer of a second metal formed thereon. The amount of tuning is dependent upon the thickness of the metallic layers, and thus tuning can be achieved by varying the thicknesses of one or both of the metallic layers. In a preferred embodiment directed to enhanced LED technology in the green spectrum regime, a double-metallic Au/Ag layer comprising a base layer of gold (Au) followed by a second layer of silver (Ag) formed thereon is deposited on top of InGaN/GaN quantum wells (QWs) on a sapphire/GaN substrate.

Electrochemical Nanoparticle-Enzyme Sensors for Screening Bacterial Contamination in Drinking Water

PubMed Central

Chen, Juhong; Jiang, Ziwen; Ackerman, Jonathan D.; Yazdani, Mahdieh; Hou, Singyuk

2015-01-01

Traditional plating and culturing methods used to quantify bacteria commonly require hours to days from sampling to results. We present here a simple, sensitive and rapid electrochemical method for bacteria detection in drinking water based on gold nanoparticle-enzyme complexes. The gold nanoparticles were functionalized with positively charged quaternary amine headgroups that could bind to enzymes through electrostatic interactions, resulting in inhibition of enzymatic activity. In the presence of bacteria, the nanoparticles released from the enzymes and preferentially bound to the bacteria, resulting in an increase in enzyme activity, releasing a redox-active phenol from the substrate. We employed this strategy for the electrochemical sensing of Escherichia coli and Staphylococcus aureus, resulting in a rapid detection (<1h) with high sensitivity (102 CFU·mL−1). PMID:26042607

Soft nanoimprint lithography on SiO2 sol-gel to elaborate sensitive substrates for SERS detection

NASA Astrophysics Data System (ADS)

Hamouda, Frédéric; Bryche, Jean-François; Aassime, Abdelhanin; Maillart, Emmanuel; Gâté, Valentin; Zanettini, Silvia; Ruscica, Jérémy; Turover, Daniel; Bartenlian, Bernard

2017-12-01

This paper presents a new alternative fabrication of biochemical sensor based on surface enhanced Raman scattering (SERS) by soft nanoimprint lithography (S-NIL) on SiO2 sol-gel. Stabilization of the sol-gel film is obtained by annealing which simplifies the manufacturing of these biosensors and is compatible with mass production at low cost. This detector relies on a specific pattern of gold nanodisks on a thin gold film to obtain a better sensitivity of molecules' detection. Characterizations of SERS devices were performed on a confocal Raman microspectrophotometer after a chemical functionalization. We report a lateral collapse effect on poly(diméthylsiloxane) (PDMS) stamp for specific nanostructure dimensions. This unintentional effect is used to evaluate S-NIL resolution in SiO2 sol-gel.

Modeling of a C-end rule peptide adsorbed onto gold nanoparticles.

PubMed

Triguero, Jordi; Flores-Ortega, Alejandra; Zanuy, David; Alemán, Carlos

2018-01-01

The RPAR peptide, a prototype C-end Rule (CendR) sequence that binds to neuropilin-1 (NRP-1), has potential therapeutic uses as internalization trigger in anticancer nanodevices. Recently, the functionalization of gold nanoparticles with CendR peptides has been proved to be a successful strategy to target the NRP-1 receptor in prostate cancer cells. In this work, we investigate the influence of two gold surface facets, (100) and (111), on the conformational preferences of RPAR using molecular dynamics simulations. Both clustering and conformational analyses revealed that the peptide backbone becomes very rigid upon adsorption onto gold, which is a very fast and favored process, the only flexibility being attributed to the side chains of the two Arg residues. Thus, the different components of RPAR tend to adopt an elongated shape, which is characterized by the pseudo-extended conformation of both the backbone and the Arg side chains. This conformation is very different from the already known bioactive conformation, indicating that RPAR is drastically affected by the substrate. Interestingly, the preferred conformations of the peptide adsorbed onto gold facets are not stabilized by salt bridges and/or specific intramolecular hydrogen bonds, which represent an important difference with respect to the conformations found in other environments (e.g. the peptide in solution and interacting with NRP-1 receptor). However, the conformational changes induced by the substrate are not detrimental for the use of gold nanoparticles as appropriate vehicles for the transport and targeted delivery of the RPAR. Thus, once their high affinity for the NRP-1 receptor induces the targeted delivery of the elongated peptide molecules from the gold nanoparticles, the lack of intramolecular interactions facilitates their evolution towards the bioactive conformation, increasing the therapeutic efficacy of the peptide. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

3D Graphene Oxide-encapsulated Gold Nanoparticles to Detect Neural Stem Cell Differentiation

PubMed Central

Kim, Tae-Hyung; Lee, Ki-Bum; Choi, Jeong-Woo

2013-01-01

Monitoring of stem cell differentiation and pluripotency is an important step for the practical use of stem cells in the field of regenerative medicine. Hence, a new non-destructive detection tool capable of in situ monitoring of stem cell differentiation is highly needed. In this study, we report a 3D graphene oxide-encapsulated gold nanoparticle that is very effective for the detection of the differentiation potential of neural stem cells (NSCs) based on surface-enhanced Raman spectroscopy (SERS). A new material, 3D GO-encapsulated gold nanoparticle, is developed to induce the double enhancement effect of graphene oxide and gold nanoparticle on SERS signals which is only effective for undifferentiated NSCs. The Raman peaks achieved from undifferentiated NSCs on the graphene oxide (GO)-encapsulated gold nanoparticles were 3.5 times higher than peaks obtained from normal metal structures and were clearly distinguishable from those of differentiated cells. The number of C=C bonds and the raman instensity at 1656cm−1 was found to show a positive correlation, which matches the differentiation state of the NSCs. Moreover, the substrate composed of 3D GO-encapsulated gold nanoparticles was also effective at distinguishing the differentiation state of single NSC by using electrochemical and electrical techniques. Hence, the proposed technique can be used as a powerful non-destructive in situ monitoring tool for the identification of the differentiation potential of various kinds of stem cells (mesenchymal, hematopoietic, and neural stem cells). PMID:23937915

Mixed carboranethiol self-assembled monolayers on gold surfaces

NASA Astrophysics Data System (ADS)

Yavuz, Adem; Sohrabnia, Nima; Yilmaz, Ayşen; Danışman, M. Fatih

2017-08-01

Carboranethiol self-assembled monolayers on metal surfaces have been shown to be very convenient systems for surface engineering. Here we have studied pure and mixed self-assembled monolayers (SAMs) of three different carboranethiol (CT) isomers on gold surfaces. The isomers were chosen with dipole moments pointing parallel to (m-1-carboranethiol, M1), out of (m-9-carboranethiol, M9) and into (o-1-carboranethiol, O1) the surface plane, in order to investigate the effect of dipole moment orientation on the film properties. In addition, influence of the substrate surface morphology on the film properties was also studied by using flame annealed (FA) and template stripped (TS) gold surfaces. Contact angle measurements indicate that in M1/M9 and M1/O1 mixed SAMs, M1 is the dominant species on the surface even for low M1 ratio in the growth solution. Whereas for O1/M9 mixed SAMs no clear evidence could be observed indicating dominance of one of the species over the other one. Though contact angle values were lower and hysteresis values were higher for SAMs grown on TS gold surfaces, the trends in the behavior of the contact angles with changing mixing ratio were identical for SAMs grown on both substrates. Atomic force microscopy images of the SAMs on TS gold surfaces indicate that the films have similar morphological properties regardless of mixing ratio.

High reliability bond program using small diameter aluminum wire

NASA Technical Reports Server (NTRS)

Macha, M.; Thiel, R. A.

1975-01-01

The program was undertaken to characterize the performance of small diameter aluminum wire ultrasonically bonded to conductors commonly encountered in hybrid assemblies, and to recommend guidelines for improving this performance. Wire, 25.4, 38.1 and 50.8 um (1, 1.5 and 2 mil), was used with bonding metallization consisting of thick film gold, thin film gold and aluminum as well as conventional aluminum pads on semiconductor chips. The chief tool for evaluating the performance was the double bond pull test in conjunction with a 72 hour - 150 C heat soak and -65 C to +150 C thermal cycling. In practice the thermal cycling was found to have relatively little effect compared to the heat soak. Pull strength will decrease after heat soak as a result of annealing of the aluminum wire; when bonded to thick film gold, the pull strength decreased by about 50% (weakening of the bond interface was the major cause of the reduction). Bonds to thin film gold lost about 30 - 40% of their initial pull strenth; weakening of the wire itself at the bond heel was the predominant cause. Bonds to aluminum substrate metallization lost only about 22%. Bonds between thick and thin film gold substrate metallization and semiconductor chips substantiated the previous conclusions but also showed that in about 20 to 25% of the cases, bond interface failure occurred at the semiconductor chip.

Functional paper-based SERS substrate for rapid and sensitive detection of Sudan dyes in herbal medicine

NASA Astrophysics Data System (ADS)

Wu, Mianmian; Li, Pan; Zhu, Qingxia; Wu, Meiran; Li, Hao; Lu, Feng

2018-05-01

There has been an increasing demand for rapid and sensitive techniques for the identification of Sudan compounds that emerged as the most often illegally added fat-soluble dyes in herbal medicine. In this report, we have designed and fabricated a functionalized filter paper consisting of gold nanorods (GNRs) and mono-6-thio-cyclodextrin (HS-β-CD) as a surface-enhanced Raman spectroscopy (SERS) substrate, in which the GNR provides sufficient SERS enhancement, and the HS-β-CD with strong chemical affinity toward GNR provides the inclusion compound to capture hydrophobic molecules. Moreover, the CD-GNR were uniformly assembled on filter paper cellulose through the electrostatic adsorption and hydrogen bond, so that the CD-GNR paper-based SERS substrate (CD-GNR-paper) demonstrated higher sensitivity for the determination of Sudan III (0.1 μM) and Sudan IV (0.5 μM) than GNRs paper-based SERS substrate (GNR-paper), with high stability after the storage in the open air for 90 days. Importantly, CD-GNR-paper can effectively collect the Sudan dyes from illegally adulterated onto samples of Resina Draconis with a simple operation, further open up new exciting opportunity for SERS detection of more compounds illegally added with high sensitivity and fast signal responses.

Field-assisted nanopatterning of metals, metal oxides and metal salts

NASA Astrophysics Data System (ADS)

Liu, Jun-Fu; Miller, Glen P.

2009-02-01

The tip-based nanofabrication method called field-assisted nanopatterning or FAN has now been extended to the transfer of metals, metal oxides and metal salts onto various receiving substrates including highly ordered pyrolytic graphite, passivated gold and indium-tin oxide. Standard atomic force microscope tips were first dip-coated using suspensions of inorganic compounds in solvent. The films prepared in this manner were non-uniform and contained inorganic nanoparticles. Tip-based nanopatterning on chosen substrates was conducted under high electric field conditions. The same tip was used for both nanofabrication and imaging. Arbitrary patterns were formed with dimensions that ranged from tens of microns to sub-20 nm and were controlled by tuning the tip bias during fabrication. Most tip-based nanopatterning techniques are limited in terms of the type of species that can be deposited and the type of substrates onto which the deposition occurs. With the successful deposition of inorganic species reported here, FAN is demonstrated to be a truly versatile tip-based nanofabrication technique that is useful for the deposition of a wide variety of both organic and inorganic species including small molecules, large molecules and polymers.

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor-liquid-solid technique

NASA Astrophysics Data System (ADS)

LeBoeuf, J. L.; Brodusch, N.; Gauvin, R.; Quitoriano, N. J.

2014-12-01

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor-liquid-solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30% single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the {1 0 0} surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.

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

Schmidtbauer, Jan; Bansen, Roman; Heimburger, Robert

Germanium nanowires (NWs) were grown onto Ge(111) substrates by the vapor-liquid-solid process using gold droplets. The growth was carried out in a molecular beam epitaxy chamber at substrate temperatures between 370 Degree-Sign C and 510 Degree-Sign C. The resulting nanowire growth rate turns out to be highly dependent on the substrate temperature exhibiting the maximum at T = 430 Degree-Sign C. The temperature dependence of growth rate can be attributed to surface diffusion both along the substrate and nanowire sidewalls. Analyzing the diffusive material transport yields a diffusion length of 126 nm at a substrate temperature of 430 Degree-Sign C.

Self-assembled diatom substrates with plasmonic functionality

NASA Astrophysics Data System (ADS)

Kwon, Sun Yong; Park, Sehyun; Nichols, William T.

2014-04-01

Marine diatoms have an exquisitely complex exoskeleton that is promising for engineered surfaces such as sensors and catalysts. For such applications, creating uniform arrays of diatom frustules across centimeter scales will be necessary. Here, we present a simple, low-cost floating interface technique to self-assemble the diatom frustules. We show that well-prepared diatoms form floating hexagonal close-packed arrays at the air-water interface that can be transferred directly to a substrate. We functionalize the assembled diatom surfaces with gold and characterize the plasmonic functionality by using surface enhanced Raman scattering (SERS). Thin gold films conform to the complex, hierarchical diatom structure and produce a SERS enhancement factor of 2 × 104. Small gold nanoparticles attached to the diatom's surface produce a higher enhancement of 7 × 104 due to stronger localization of the surface plasmons. Taken together, the large-scale assembly and plasmonic functionalization represent a promising platform to control the energy and the material flows at a complex surface for applications such as sensors and plasmonic enhanced catalysts.

Spectroscopic ellipsometry investigation of the optical properties of graphene oxide dip-coated on magnetron sputtered gold thin films

NASA Astrophysics Data System (ADS)

Politano, Grazia Giuseppina; Vena, Carlo; Desiderio, Giovanni; Versace, Carlo

2018-02-01

Despite intensive investigations on graphene oxide-gold nanocomposites, the interaction of graphene oxide sheets with magnetron sputtered gold thin films has not been studied yet. The optical constants of graphene oxide thin films dip-coated on magnetron sputtered gold thin films were determined by spectroscopic ellipsometry in the [300-1000] wavelength range. Moreover, the morphologic properties of the samples were investigated by SEM analysis. Graphene oxide absorbs mainly in the ultraviolet region, but when it is dip-coated on magnetron sputtered gold thin films, its optical constants show dramatic changes, becoming absorbing in the visible region, with a peak of the extinction coefficient at 3.1 eV. Using magnetron sputtered gold thin films as a substrate for graphene oxide thin films could therefore be the key to enhance graphene oxide optical sheets' properties for several technological applications, preserving their oxygen content and avoiding the reduction process.

Facile synthesis of dendritic gold nanostructures with hyperbranched architectures and their electrocatalytic activity toward ethanol oxidation.

PubMed

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

2013-09-25

Gold dendritic nanostructures with hyperbranched architectures were synthesized by the galvanic replacement reaction between nickel wire and HAuCl4 in aqueous solution. The study revealed that the morphology of the obtained nanostructures strongly depended on experimental parameters such as the HAuCl4 solution concentration, reaction temperature, and time, as well as stirring or not. According to the investigation of the growth process, it was proposed that gold nanoparticles with rough surfaces were first deposited on the nickel substrate and that subsequent growth preferentially occurred on the preformed gold nanoparticles, finally leading to the formation of hyperbranched gold dendrites via a self-organization process under nonequilibrium conditions. The electrochemical experiment results demonstrated that the as-obtained gold dendrites exhibited high catalytic activity toward ethanol electrooxidation in alkaline solution, indicating that this nanomaterial may be a potential catalyst for direct ethanol fuel cells.

Decoupling of epitaxial graphene via gold intercalation probed by dispersive Raman spectroscopy

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

Pillai, P. B., E-mail: p.pillai@sheffield.ac.uk, E-mail: m.desouza@sheffield.ac.uk; DeSouza, M., E-mail: p.pillai@sheffield.ac.uk, E-mail: m.desouza@sheffield.ac.uk; Narula, R.

Signatures of a superlattice structure composed of a quasi periodic arrangement of atomic gold clusters below an epitaxied graphene (EG) layer are examined using dispersive Raman spectroscopy. The gold-graphene system exhibits a laser excitation energy dependant red shift of the 2D mode as compared to pristine epitaxial graphene. The phonon dispersions in both the systems are mapped using the experimentally observed Raman signatures and a third-nearest neighbour tight binding electronic band structure model. Our results reveal that the observed excitation dependent Raman red shift in gold EG primarily arise from the modifications of the phonon dispersion in gold-graphene and showsmore » that the extent of decoupling of graphene from the underlying SiC substrate can be monitored from the dispersive nature of the Raman 2D modes. The intercalated gold atoms restore the phonon band structure of epitaxial graphene towards free standing graphene.« less

Interface effects in the dissolution of silicon into thin gold films

NASA Technical Reports Server (NTRS)

Sankur, H.; Mccaldin, J. O.

1975-01-01

The dissolution of crystalline Si and amorphous Si substrates into thin films of evaporated Au was studied with an electron microprobe and scanning electron microscopy. The dissolution pattern was found to be nonuniform along the plane of the surface and dependent on the crystalline orientation of the Si substrate. The dissolution is greatly facilitated when a very thin layer of Pd is evaporated between the Si substrate and the Au film.

Design, fabrication, and characterization of metallic nanostructures for surface-enhanced Raman spectroscopy and plasmonic applications

NASA Astrophysics Data System (ADS)

Hao, Qingzhen

Metal/dielectric nanostructures have the ability to sustain coherent electron oscillations known as surface plasmons. Due to their capability of localizing and guiding light in sub-wavelength metal nanostructures beyond diffraction limits, surface plasmon-based photonics, or “plasmonics” has opened new physical phenomena and lead to novel applications in metamaterials, optoelectronics, surface enhanced spectroscopy and biological sensing. This dissertation centers on design, fabrication, characterization of metallic nanostructures and their applications in surface-enhanced Raman spectroscopy (SERS) and actively tunable plasmonics. Metal-dielectric nanostructures are the building blocks for photonic metamaterials. One valuable design guideline for metamaterials is the Babinet’s principle, which governs the optical properties of complementary nanostructures. However, most complementary metamaterials are designed for the far infrared region or beyond, where the optical absorption of metal is small. We have developed a novel dual fabrication method, capable of simultaneously producing optically thin complementary structures. From experimental measurements and theoretical simulations, we showed that Babinet’s principle qualitatively holds in the visible region for the optically thin complements. The complementary structure is also a good platform to study subtle differences between nanoparticles and nanoholes in SERS (a surface sensitive technique, which can enhance the conventional Raman cross-section by 106˜108 fold, thus very useful for highly sensitive biochemical sensing). Through experimental measurement and theoretical analysis, we showed that the SERS enhancement spectrum (plot of SERS enhancement versus excitation wavelengths), dominated by local near-field, for nanoholes closely follows their far-field optical transmission spectrum. However, the enhancement spectrum for nanoparticles red-shifts significantly from their far-field optical extinction spectrum, due to nontrivial high orders of evanescent scattering modes. This study unveils the different near-field properties between nanoparticle and nanohole arrays and adds important details to the conventional wisdom for SERS substrate design. Besides SERS studies on gold substrates, I further extended my research to transition metals, i.e. platinum. I have carried out a comparative study of SERS performance for gold and platinum substrates. The commonly observed low enhancement from a platinum substrate is explained by the larger Fano interference between its free intra-band electrons and its bound inter-band electrons. A major challenge in applying SERS for biochemical sensing is to fabricate substrates with excellent sensitivity and uniform surface functionality. Graphene, a single sheet of carbon atoms with an ideal two-dimensional honeycomb crystal structure, offers excellent surface chemical properties. We synthesized high quality single-layer graphene sheets by chemical vapor deposition (CVD) on copper foils and transferred them to gold nanostructures, i.e., nanoparticle or nanohole arrays. Our experimental data show that graphene coated metallic substrates could achieve higher sensitivity of SERS detection than bare metallic substrates. The combined graphene-nanostructure substrates show about three-fold or nine-fold enhancement in the Raman signal of methylene blue (MB) compared with the bare nanohole or nanoparticle substrates, respectively. The difference in the enhancement factors between the nanohole and nanoparticle substrates is explained by the different coating morphologies of graphene on the two substrates. SERS enhancement of graphene is further investigated on mechanically exfoliated graphene. We found that SERS enhancement of graphene can be tuned by changing its Fermi level through doping. Both molecular doping and gate doping experiments show that hole-doped graphene yields a larger SERS enhancement in MB than electron-doped graphene, which indicates that the SERS enhancement of graphene involves the chemical mechanism. SERS enhancement from metallic nanostructures, on the other hand, is mainly an electromagnetic effect, relying on the plasmonic properties of the nanostructures. Full-wave electromagnetic simulations indicate that graphene does not alter the plasmonic properties of nanostructures significantly, and consequently there is little influence on the electromagnetic SERS enhancement. However, graphene offers additional chemical enhancement which could be combined with the conventional SERS enhancement of bare gold nanostructures to achieve higher detection sensitivity. Besides SERS, plasmonics offers an opportunity to merge photonics and electronics at the nanoscale, namely optoelectronics, to obtain even larger data capacity and speed of operation. As a necessary component for optoelectronic devices, various optical switches have been developed. First, a thin layer of frequency responsive liquid crystals (LCs) is integrated with a gold nanoparticle or nanohole array. The frequency of the applied voltage controls the configuration of LCs to align parallel or perpendicular to the nanoparticle. The transmission spectra of the system shift back and forth as a result of changing effective LCs dielectric function. We demonstrated that this hybrid system is highly reversible and repeatable. We further extend this concept to use photosensitive LCs to change the absorption bands of a plasmonic absorber. We construct a tunable plasmonic absorber by integrating a photosensitive nematic liquid crystal (PNLC) layer onto an asymmetric gold nanodisk array. A repeatable tuning range of ˜ 25 nm in the dual absorption bands of the plasmonic nanodisk array is demonstrated in the near infrared region.

Laser-induced transfer of gel microdroplets for cell printing

NASA Astrophysics Data System (ADS)

Yusupov, V. I.; Zhigar'kov, V. S.; Churbanova, E. S.; Chutko, E. A.; Evlashin, S. A.; Gorlenko, M. V.; Cheptsov, V. S.; Minaev, N. V.; Bagratashvili, V. N.

2017-12-01

We study thermal and transport processes involved in the transfer of gel microdroplets under the conditions of laser cell microprinting. The specific features of the interaction of pulsed laser radiation ( λ = 1.064 µm, pulse duration 4 - 200 ns, energy 2 µJ - 1 mJ) with the absorbing gold film deposited on the glass donor substrate are determined. The investigation of the dynamics of transport processes by means of fast optical video recording and optoacoustic methods makes it possible to determine the characteristics of the produced gel jets as functions of the laser operation regimes. The hydrodynamic process of interaction between the laser radiation and the gold coating with the hydrogel layer on it is considered and the temperature in the region of the laser pulse action is estimated. It is shown that in the mechanism of laser-induced transfer a significant role is played by the processes of explosive boiling of water (in gel) and gold. The amount of gold nanoparticles arriving at the acceptor plate in the process of the laser transfer is determined. For the laser pulse duration 8 ns and small energies (less than 10 µJ), the fraction of gold nanoparticles in the gel microdroplets is negligibly small, and their quantity linearly grows with increasing pulse energy. The performed studies offer a base for optimising the processes of laser transfer of gel microdroplets in the rapidly developing technologies of cell microprinting.

One-pot synthesis of keto thioethers by palladium/gold-catalyzed click and pinacol reactions.

PubMed

Cadu, Alban; Watile, Rahul A; Biswas, Srijit; Orthaber, Andreas; Sjöberg, Per J R; Samec, Joseph S M

2014-11-07

An atom-efficient synthesis of keto thioethers was devised via tandem gold/palladium catalysis. The reaction proceeds through a regioselective thiol attack at the β-position of the alcohol, followed by an alkyl, aryl, or benzyl 1,2-shift. Both acyclic and cyclic systems were studied, in the latter case leading to the ring expansion of cyclic substrates.

Method of Stamping Surface-Enhance Raman Spectroscopy for Label-Free, Multiplexed, Molecular Sensing and Imaging

NASA Technical Reports Server (NTRS)

Shih, Wei-Chuan (Inventor)

2017-01-01

The present disclosure relates the use of a stamping surface enhanced Raman scattering (S-SERS) technique with nanoporous gold disk (NPGD) plasmonic substrates to produce a label-free, multiplexed molecular sensing and imaging technique. A NPGD SERS substrate is stamped onto a surface containing one or more target molecules, followed by SERS measurement of the target molecules located between the surface and SERS substrate. The target molecules may be deposited on the surface, which may be a carrier substrate such as polydimethylsiloxane (PDMS).

Multiplex and high-throughput DNA detection using surface plasmon mediated fluorescence

NASA Astrophysics Data System (ADS)

Mei, Zhong

The overall objective of this research project was to develop a user-friendly and sensitive biosensor for nucleic acid aptamers with multiplexing and high-throughput capability. The sensing was based on the fluorescence signals emitted by the fluorophores coupling with plamonic nanoparticle (gold nanorod) deposited on a patterned substrate. Gold nanorods (GNRs) were synthesized using a binary mixture of hexadecyltrimethylammonium bromide (CTAB) and sodium oleate (NaOL) in seed mediated growth method. Polytetrafluoroethylene (PTFE) printed glass slides were selectively coated with a gold thin-film to define hydrophilic areas for GNR deposition. Due to the wettablity contrast, GNR solution dropped on the slide was induced to assemble exclusively in the hydrophilic spots. By controlling temperature and humidity of the evaporation process, vertically-standing GNR arrays were achieved on the pattered slide. Fluorescence was conjugated to GNR surface via DNA double strand with tunable length. Theoretical simulation predicted a flat layer ( 30 nm thick) of uniform "hot spots" presented on the GNR tips, which could modify the nearby fluorescence. Experimentally, the vertical GNR arrays yielded metallic enhanced fluorescence (MEF) effect, which was dependent on the spectrum overlap and GNR-fluorophore distance. Specifically, the maximum enhancement of Quasar 670 and Alexa 750 was observed when it was coupled with GNR664 (plasmonic wavelength 664 nm) and GNR778 respectively at a distance of 16 nm, while the carboxyfluorescein (FAM) was at maximal intensity when attached to gold nanosphere520. This offers an opportunity for multiplexed DNA sensing. Based on this, we developed a novel GNR mediated fluorescence biosensor for DNA detection. Fluorescence labeled haipin-DNA probes were introduced to designated spots of GNR array with the matching LSPR wavelengths on the substrate. The fluorescence was quenched originally because of Forster resonance energy transfer (FRET) effect. Upon hybridization with their complimentary target DNAs, hairpin structures were opened and the fluorescence enhancement from each GNR sensing spot was measured by fluorescence scanning. We demonstrated multiple DNA sequences were simultaneously detected at a picomolar level with high-throughput capability using the ordered GNR array biochip.

Merely Measuring the UV-Visible Spectrum of Gold Nanoparticles Can Change Their Charge State.

PubMed

Navarrete, Jose; Siefe, Chris; Alcantar, Samuel; Belt, Michael; Stucky, Galen D; Moskovits, Martin

2018-02-14

Metallic nanostructures exhibit a strong plasmon resonance at a wavelength whose value is sensitive to the charge density in the nanostructure, its size, shape, interparticle coupling, and the dielectric properties of its surrounding medium. Here we use UV-visible transmission and reflectance spectroscopy to track the shifts of the plasmon resonance in an array of gold nanoparticles buried under metal-oxide layers of varying thickness produced using atomic layer deposition (ALD) and then coated with bulk layers of one of three metals: aluminum, silver, or gold. A significant shift in the plasmon resonance was observed and a precise value of ω p , the plasmon frequency of the gold comprising the nanoparticles, was determined by modeling the composite of gold nanoparticles and metal-oxide layer as an optically homogeneous film of core-shell particles bounded by two substrates: one of quartz and the other being one of the aforementioned metals, then using a Maxwell-Garnett effective medium expression to extract ω p for the gold nanoparticles before and after coating with the bulk metals. Under illumination, the change in the charge density of the gold nanoparticles per particle determined from the change in the values of ω p is found to be some 50-fold greater than what traditional electrostatic contact electrification models compute based on the work function difference of the two conductive materials. Moreover, when using bulk gold as the capping layer, which should have resulted in a negligible charge exchange between the gold nanoparticles and the bulk gold, a significant charge transfer from the bulk gold layer to the nanoparticles was observed as with the other metals. We explain these observations in terms of the "plasmoelectric effect", recently described by Atwater and co-workers, in which the gold nanoparticles modify their charge density to allow their resonant wavelength to match that of the incident light, thereby achieving, a lower value of the chemical potential due to the entropy increase resulting from the conversion of the plasmon's energy to heat. We conclude that even the act of registering the spectrum of nanoparticles is at times sufficient to alter their charge densities and hence their UV-visible spectra.

Multi-technique characterization of gold electroplating on silver substrates for cultural heritage applications

NASA Astrophysics Data System (ADS)

Ortega-Feliu, I.; Ager, F. J.; Roldán, C.; Ferretti, M.; Juanes, D.; Scrivano, S.; Respaldiza, M. A.; Ferrazza, L.; Traver, I.; Grilli, M. L.

2017-09-01

This work presents a detailed study of a series of silver plates gilded via electroplating techniques in which the characteristics of the coating gold layers are investigated as a function of the electroplating variables (voltage, time, anode surface and temperature). Some reference samples were coated by radio frequency sputtering in order to compare gold layer homogeneity and effective density. Surface analysis was performed by means of atomic and nuclear techniques (SEM-EDX, EDXRF, PIXE and RBS) to obtain information about thickness, homogeneity, effective density, profile concentration of the gold layers and Au-Ag diffusion profiles. The gold layer thickness obtained by PIXE and EDXRF is consistent with the thickness obtained by means of RBS depth profiling. Electroplated gold mass thickness increases with electroplating time, anode area and voltage. However, electrodeposited samples present rough interfaces and gold layer effective densities lower than the nominal density of Au (19.3 g/cm3), whereas sputtering produces uniform layers with nominal density. These analyses provide valuable information to historians and curators and can help the restoration process of gold-plated silver objects.

Heat- and electron-beam-induced transport of gold particles into silicon oxide and silicon studied by in situ high-resolution transmission electron microscopy.

PubMed

Biskupek, Johannes; Kaiser, Ute; Falk, Fritz

2008-06-01

In this study, we describe the transport of gold (Au) nanoparticles from the surface into crystalline silicon (Si) covered by silicon oxide (SiO(2)) as revealed by in situ high-resolution transmission electron microscopy. Complete crystalline Au nanoparticles sink through the SiO(2) layer into the Si substrate when high-dose electron irradiation is applied and temperature is raised above 150 degrees C. Above temperatures of 250 degrees C, the Au nanoparticles finally dissolve into fragments accompanied by crystallization of the amorphized Si substrate around these fragments. The transport process is explained by a wetting process followed by Stokes motion. Modelling this process yields boundaries for the interface energies involved.

Gaseous Oxidized Mercury Flux from Substrates Associated with Industrial Scale Gold Mining in Nevada, USA

NASA Astrophysics Data System (ADS)

Miller, M. B.

2015-12-01

Gaseous elemental and oxidized mercury (Hg) fluxes were measured in a laboratory setting from substrate materials derived from industrial-scale open pit gold mining operations in Nevada, USA. Mercury is present in these substrates at a range of concentrations (10 - 40000 ng g-1), predominantly of local geogenic origin in association with the mineralized gold ores, but altered and redistributed to a varying degree by subsequent ore extraction and processing operations, including deposition of Hg recently emitted to the atmosphere from large point sources on the mines. Waste rock, heap leach, and tailings material usually comprise the most extensive and Hg emission relevant substrate surfaces. All three of these material types were collected from active Nevada mine sites in 2010 for previous research, and have since been stored undisturbed at the University of Nevada, Reno. Gaseous elemental Hg (GEM) flux was previously measured from these materials under a variety of conditions, and was re-measured in this study, using Teflon® flux chambers and Tekran® 2537A automated ambient air analyzers. GEM flux from dry undisturbed materials was comparable between the two measurement periods. Gaseous oxidized Hg (GOM) flux from these materials was quantified using an active filter sampling method that consisted of polysulfone cation-exchange membranes deployed in conjunction with the GEM flux apparatus. Initial measurements conducted within greenhouse laboratory space indicate that in dry conditions GOM is deposited to relatively low Hg cap and leach materials, but may be emitted from the much higher Hg concentration tailings material.

Annealing effects on electrical behavior of gold nanoparticle film: Conversion of ohmic to non-ohmic conductivity

NASA Astrophysics Data System (ADS)

Ebrahimpour, Zeinab; Mansour, Nastaran

2017-02-01

This paper reports on the electrical behavior of self-assembled gold nanoparticle films before and after high-temperature annealing in ambient environment. These films are made by depositing gold nanoparticles from a colloidal solution on glass substrates using centrifuge deposition technique. The current-voltage (I-V) characteristics of these films exhibits ohmic and non-ohmic properties for un-annealed and annealed films respectively. As the annealing time duration increases, the onset of non-ohmic behavior occurs at higher voltages. To understand the underlying mechanisms for the observed electrical conduction behavior in these films and how electrical conduction is effected by film morphology and structural properties before and after annealing, systematic comparative studies based on scanning electron microscopy (SEM), UV-vis absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) have been performed. The morphology of the films shows that the assembled gold nanoparticles are distributed on the substrate in a random way before annealing. After 2 h annealing gold nanoparticles exhibit a higher filling fraction when examined by SEM, which means that they coalesce, upon annealing, with respect to un-annealed films. The UV-vis absorption spectra of the films show that there is a red-shift and broadening in the absorption band for the annealed films. The observed phenomenon is related to the plasmon near-field coupling effect and suggests that the nanoparticle ensembles interspacing has decreased. The structural and crystallinity of the films exhibit amorphous structure before annealing and pure crystalline phases with a preferential growth direction along the (111) plane after annealing. The XPS analysis further suggests the existence of the stable thin oxide layer in the phase of Au2O3 in the annealed films. The I-V characteristics have been described by Simmons' model for tunnel transport through metal-insulator-metal (MIM) junctions. The Fowler-Nordheim (F-N) plots show the transition of the in-plane charge transport mechanism from direct tunneling to field emission in annealed films. Our results suggest that, the formation of a thin layer of Au2O3 , the proximity of the nanoparticles as well as their higher filling fraction are important parameters related with the tunneling process enhancement. The observed non-ohmic conductivity property can make these self-assembled gold nanoparticle films very useful structures in different applications such as sensing, resistors and other nanoelectronic applications.

Anomalous complete opaqueness in a sparse array of gold nanoparticle chains

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

Bai Benfeng; Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084; Department of Physics and Mathematics, University of Eastern Finland, P.O. Box 111, FI-80101 Joensuu

2011-08-22

We report on an anomalous polarization-switching extinction effect in a sparse array of gold nanoparticle chains: under normal incidence of light, the array is almost transparent for one polarization; whereas it is fully opaque (with nearly zero transmittance) for the orthogonal polarization within a narrow band, even though the nanoparticles cover only a tiny fraction (say, 3.5%) of the transparent substrate surface. We reveal that the strong polarization-dependent short-range dipolar coupling and long-range radiative coupling of gold nanoparticles in this highly asymmetric array is responsible for this extraordinary effect.

Metal-assisted chemical etching using sputtered gold: a simple route to black silicon

NASA Astrophysics Data System (ADS)

Kurek, Agnieszka; Barry, Seán T.

2011-08-01

We report an accessible and simple method of producing 'black silicon' with aspect ratios as high as 8 using common laboratory equipment. Gold was sputtered to a thickness of 8 nm using a low-vacuum sputter coater. The structures were etched into silicon substrates using an aqueous H2O2/HF solution, and the gold was then removed using aqua regia. Ultrasonication was necessary to produce columnar structures, and an etch time of 24 min gave a velvety, non-reflective surface. The surface features after 24 min etching were uniformly microstructured over an area of square centimetres.

Correlating single-molecule and ensemble-average measurements of peptide adsorption onto different inorganic materials.

PubMed

Kim, Seong-Oh; Jackman, Joshua A; Mochizuki, Masahito; Yoon, Bo Kyeong; Hayashi, Tomohiro; Cho, Nam-Joon

2016-06-07

The coating of solid-binding peptides (SBPs) on inorganic material surfaces holds significant potential for improved surface functionalization at nano-bio interfaces. In most related studies, the goal has been to engineer peptides with selective and high binding affinity for a target material. The role of the material substrate itself in modulating the adsorption behavior of a peptide molecule remains less explored and there are few studies that compare the interaction of one peptide with different inorganic substrates. Herein, using a combination of two experimental techniques, we investigated the adsorption of a 16 amino acid-long random coil peptide to various inorganic substrates - gold, silicon oxide, titanium oxide and aluminum oxide. Quartz crystal microbalance-dissipation (QCM-D) experiments were performed in order to measure the peptide binding affinity for inorganic solid supports at the ensemble average level, and atomic force microscopy (AFM) experiments were conducted in order to determine the adhesion force of a single peptide molecule. A positive trend was observed between the total mass uptake of attached peptide and the single-molecule adhesion force on each substrate. Peptide affinity for gold was appreciably greater than for the oxide substrates. Collectively, the results obtained in this study offer insight into the ways in which inorganic materials can differentially influence and modulate the adhesion of SBPs.

Combined Thermochromic And Plasmonic: Optical Responses In Novel Nanocomposite Au-VO2 Films Prepared By RF Inverted Cylindrical Magnetron Sputtering

NASA Astrophysics Data System (ADS)

Kana, J. B. Kana; Ndjaka, J. M.; Manyala, N.; Nemraoui, O.; Beye, A. C.; Maaza, M.

2008-09-01

We prepared gold/Vanadium dioxide nanocomposites thin films by the rf reactive inverted cylindrical magnetron sputtering (ICMS) for the first time and report their enhanced surface plasmon resonance (SPR) tunable shift reversibility. ICMS has been attracting much attention for its ability for uniform coating of three-dimensional objects and high-rate deposition of dielectric materials. To investigate the optical properties of gold nanoparticles embedded in an active matrix (VO2) composite film was synthesized on corning glass substrates for several substrate temperatures ranging from 400 °C to 600 °C. The X-ray diffraction results demonstrated that the Au and VO2 were well crystallized. The optical transmission properties were measured from 300nm to 1100nm and the absorption peak due to the surface plasmon resonance (SPR) of Au nanoparticles were observed. Under external temperature stimuli, the tunable reversibility of the SPR shift was observed when the nanocomposites temperature varies from 20 °C to 100 °C. The enhancement of this shift of SPR was observed as the substrate temperature increases and it was found that the shift of SPR increased rapidly with increasing substrate temperature but then remained constant at ˜57 nm for substrate temperature higher than 500 °C.

Substrate solder barriers for semiconductor epilayer growth

DOEpatents

Drummond, Timothy J.; Ginley, David S.; Zipperian, Thomas E.

1989-01-01

During the growth of compound semiconductors by epitaxial processes, substrates are typically mounted to a support. In modular beam epitaxy, mounting is done using indium as a solder. This method has two drawbacks: the indium reacts with the substrate, and it is difficult to uniformly wet the back of a large diameter substrate. Both of these problems have been successfully overcome by sputter coating the back of the substrate with a thin layer of tungsten carbide or tungsten carbide and gold. In addition to being compatible with the growth of high quality semiconductor epilayers this coating is also inert in all standard substrate cleaning etchants used for compound semiconductors, and provides uniform distribution of energy in radiant heating.

Substrate solder barriers for semiconductor epilayer growth

DOEpatents

Drummond, T.J.; Ginley, D.S.; Zipperian, T.E.

1989-05-09

During the growth of compound semiconductors by epitaxial processes, substrates are typically mounted to a support. In modular beam epitaxy, mounting is done using indium as a solder. This method has two drawbacks: the indium reacts with the substrate, and it is difficult to uniformly wet the back of a large diameter substrate. Both of these problems have been successfully overcome by sputter coating the back of the substrate with a thin layer of tungsten carbide or tungsten carbide and gold. In addition to being compatible with the growth of high quality semiconductor epilayers this coating is also inert in all standard substrate cleaning etchants used for compound semiconductors, and provides uniform distribution of energy in radiant heating.

Development of an optical biosensor based on surface-enhanced Raman scattering for DNA analysis

NASA Astrophysics Data System (ADS)

Yigit, Tugce; Akdogan, Ebru; Karagoz, Isık. Didem; Kahraman, Mehmet

2016-03-01

Rapid, accurate and sensitive DNA analysis is critically important for the diagnostic of genetic diseases. The most common method preferred in practice is fluorescence based microarrays to analyze the DNA. However, there exist some disadvantages related to the above-mentioned method such as the overlapping of the fluorescence emission wavelengths that can diminish in the performance of multiplexing, needed to obtain fluorescence spectra from each dye and photo degradation. In this study, a novel SERS based DNA analysis approach, which is Raman active dye-free and independent of SERS substrate properties, is developed. First, the single strand DNA probe is attached to the SERS substrate and half of the complimentary DNA is attached to gold nanoparticles, as well. We hypothesize that in the presence of target DNA, the complimentary DNA coupled colloids will bind to the SERS substrate surface via hybridization of single strand target DNA. To test this hypothesis, we used UV/Vis spectroscopy, atomic for microscopy (AFM) and dynamic light scattering (DLS). DNA analysis is demonstrated by a peak shift of the certain peak of the small molecules attached to the SERS substrate surface instead of SERS spectrum obtained in the presence of target DNA from the Raman reporter molecules. The degree of peak shifting will be used for the quantification of the target DNA in the sample. Plasmonic properties of SERS substrates and reproducibility issues will not be considerable due to the use of peak shifting instead of peak intensity for the qualitative analysis.

A wide range optical pH sensor for living cells using Au@Ag nanoparticles functionalized carbon nanotubes based on SERS signals.

PubMed

Chen, Peng; Wang, Zhuyuan; Zong, Shenfei; Chen, Hui; Zhu, Dan; Zhong, Yuan; Cui, Yiping

2014-10-01

p-Aminothiophenol (pATP) functionalized multi-walled carbon nanotubes (MWCNTs) have been demonstrated as an efficient pH sensor for living cells. The proposed sensor employs gold/silver core-shell nanoparticles (Au@Ag NPs) functionalized MWCNTs hybrid structure as the surface-enhanced Raman scattering (SERS) substrate and pATP molecules as the SERS reporters, which possess a pH-dependent SERS performance. By using MWCNTs as the substrate to be in a state of aggregation, the pH sensing range could be extended to pH 3.0∼14.0, which is much wider than that using unaggregated Au@Ag NPs without MWCNTs. Furthermore, the pH-sensitive performance was well retained in living cells with a low cytotoxicity. The developed SERS-active MWCNTs-based nanocomposite is expected to be an efficient intracellular pH sensor for bio-applications.

Elaboration of a microstructured inkjet-printed carbon electrochemical capacitor

NASA Astrophysics Data System (ADS)

Pech, David; Brunet, Magali; Taberna, Pierre-Louis; Simon, Patrice; Fabre, Norbert; Mesnilgrente, Fabien; Conédéra, Véronique; Durou, Hugo

Carbon-based micro-supercapacitors dedicated to energy storage in self-powered modules were fabricated with inkjet printing technology on silicon substrate. An ink was first prepared by mixing an activated carbon powder with a PTFE polymer binder in ethylene glycol stabilized with a surfactant then deposited by inkjet on patterned gold current collectors with the substrate heated at 140 °C in order to assure a good homogeneity. Electrochemical micro-capacitors with electrodes in an interdigital configuration were fabricated, and characterized using electrochemical techniques in 1 M Et 4NBF 4 propylene carbonate electrolyte. These micro-devices show an excellent capacitive behavior over a wide potential range of 2.5 V for a cell capacitance of 2.1 mF cm -2. The newly developed technology will allow the integration of the storage device as close as possible to the MEMS-based energy harvesting device, minimizing power losses through connections.

The effect of V/III ratio on the morphology and structure of GaAs nanowires by MOCVD

NASA Astrophysics Data System (ADS)

Liu, Yan; Peng, Yan; Guo, Jingwei; La, Dongsheng; Xu, Zhaopeng

2018-05-01

In this paper, GaAs nanowires with different V/III ratios (70, 140, 280 and 560) were vertically grown from bottom to top on GaAs substrates by using metal organic chemical vapor deposition based on gold assisted vapor-liquid-solid mechanism. It is found that the growth rate of nanowires is inversely proportional to their V/III ratio. And the V/III ratio can also change nanowire growth type. For the nanowire with small V/III ratios (≤280), the reactants are most from those atoms merged in the catalyst. But, for the nanowire with V/III ratio 560, the contribution mainly comes from the diffusions of atoms pyrolyzed on the surface of the nanowire and the substrate. A shrunken neck under the catalyst is observed in TEM characterizations. These results will provide a theoretical basis for potential practical applications of nanowire-based devices.

High surface area electrodes by template-free self-assembled hierarchical porous gold architecture.

PubMed

Morag, Ahiud; Golub, Tatiana; Becker, James; Jelinek, Raz

2016-06-15

The electrode active surface area is a crucial determinant in many electrochemical applications and devices. Porous metal substrates have been employed in electrode design, however construction of such materials generally involves multistep processes, generating in many instances electrodes exhibiting incomplete access to internal pore surfaces. Here we describe fabrication of electrodes comprising hierarchical, nano-to-microscale porous gold matrix, synthesized through spontaneous crystallization of gold thiocyanate in water. Cyclic voltammetry analysis revealed that the specific surface area of the conductive nanoporous Au microwires was very high and depended only upon the amount of gold used, not electrode areas or geometries. Application of the electrode in a pseudo-capacitor device is presented. Copyright © 2016 Elsevier Inc. All rights reserved.

Synthesis of gold nanoflowers using deep eutectic solvent with high surface enhanced Raman scattering properties

NASA Astrophysics Data System (ADS)

Aghakhani Mahyari, Farzaneh; Tohidi, Maryam; Safavi, Afsaneh

2016-09-01

A facile, seed-less and one-pot method was developed for synthesis of gold nanoflowers with multiple tips through reduction of HAuCl4 with deep eutectic solvent at room temperature. This solvent is eco-friendly, low-cost, non-toxic and biodegradable and can act as both reducing and shape-controlling agent. In this protocol, highly branched and stable gold nanoflowers were obtained without using any capping agent. The obtained products were characterized by different techniques including, field emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction and UV-vis spectroscopy. The as-prepared gold nanoflowers exhibit efficient surface-enhanced Raman scattering (SERS) properties which can be used as excellent substrates for SERS.

Test Of A Microwave Amplifier With Superconductive Filter

NASA Technical Reports Server (NTRS)

Bhasin, K. B.; Toncich, S. S.; Chorey, C. M.; Bonetti, R. R.; Williams, A. E.

1995-01-01

Report describes design and low-temperature tests of low-noise GaAs microwave amplifier combined with microstrip band-pass filter. Two versions of microstrip filter used in alternate tests; in one version, microstrips formed as films of high-transition-temperature superconductor Y/Ba/Cu/O on lanthanum aluminate substrate with gold film as ground plane. Other version identical except microstrips as well as ground plane made of gold, normally conductive.

Evaluation of coated metallic bipolar plates for polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Yoon, Wonseok; Huang, Xinyu; Fazzino, Paul; Reifsnider, Kenneth L.; Akkaoui, Michael A.

Metallic bipolar plates for polymer electrolyte membrane (PEM) fuel cells typically require coatings for corrosion protection. Other requirements for the corrosion protective coatings include low electrical contact resistance, good mechanical robustness, low material and fabrication cost. The authors have evaluated a number of protective coatings deposited on stainless steel substrates by electroplating and physical vapor deposition (PVD) methods. The coatings are screened with an electrochemical polarization test for corrosion resistance; then the contact resistance test was performed on selected coatings. The coating investigated include Gold with various thicknesses (2 nm, 10 nm, and 1 μm), Titanium, Zirconium, Zirconium Nitride (ZrN), Zirconium Niobium (ZrNb), and Zirconium Nitride with a Gold top layer (ZrNAu). The substrates include three types of stainless steel: 304, 310, and 316. The results show that Zr-coated samples satisfy the DOE target for corrosion resistance at both anode and cathode sides in typical PEM fuel cell environments in the short-term, but they do not meet the DOE contact resistance goal. Very thin gold coating (2 nm) can significantly decrease the electrical contact resistance, however a relatively thick gold coating (>10 nm) with our deposition method is necessary for adequate corrosion resistance, particularly for the cathode side of the bipolar plate.

Polyethylenimine-assisted seed-mediated synthesis of gold nanoparticles for surface-enhanced Raman scattering studies

NASA Astrophysics Data System (ADS)

Philip, Anish; Ankudze, Bright; Pakkanen, Tuula T.

2018-06-01

Large-sized gold nanoparticles (AuNPs) were synthesized with a new polyethylenimine - assisted seed - mediated method for surface-enhanced Raman scattering (SERS) studies. The size and polydispersity of gold nanoparticles are controlled in the growth step with the amounts of polyethylenimine (PEI) and seeds. Influence of three silicon oxide supports having different surface morphologies, namely halloysite (Hal) nanotubes, glass plates and inverse opal films of SiO2, on the performance of gold nanoparticles in Raman scattering of a 4-aminothiophenol (4-ATP) analyte was investigated. Electrostatic interaction between positively charged polyethylenimine-capped AuNPs and negatively charged surfaces of silicon oxide supports was utilized in fabrication of the SERS substrates using deposition and infiltration methods. The Au-photonic crystal of the three SERS substrate groups is the most active one as it showed the highest analytical enhancement factor (AEF) and the lowest detection limit of 1x10-8 M for 4-ATP. Coupling of the optical properties of photonic crystals with the plasmonic properties of AuNPs provided Au-photonic crystals with the high SERS activity. The AuNPs clusters formed both in the photonic crystal and on the glass plate are capable of forming more hot spots as compared to sparsely distributed AuNPs on Hal nanotubes and thereby increasing the SERS enhancement.

Near-field engineering of Fano resonances in a plasmonic assembly for maximizing CARS enhancements.

PubMed

He, Jinna; Fan, Chunzhen; Ding, Pei; Zhu, Shuangmei; Liang, Erjun

2016-02-10

Surface enhanced coherent anti-Stokes Raman scattering (SECARS) is a sensitive tool and promising for single molecular detection and chemical selective imaging. However, the enhancement factors (EF) were only 10~100 for colloidal silver and gold nanoparticles usually used as SECARS substrates. In this paper, we present a design of SECARS substrate consisting of three asymmetric gold disks and strategies for maximizing the EF by engineering near-field properties of the plasmonic Fano nanoassembly. It is found that the E-field "hot spots" corresponding to three different frequencies involved in SECARS process can be brought to the same spatial locations by tuning incident orientations, giving rise to highly confined SECARS "hot spots" with the EF reaching single-molecule sensitivity. Besides, an even higher EF of SECARS is achieved by introducing double Fano resonances in this plasmonic nanoassembly via further enlarging the sizes of the constituent disks. These findings put an important step forward to the plasmonic substrate design for SECARS as well as for other nonlinear optical processes.

Biologically Derived Nanoparticle Arrays via a Site-Specific Reconstitution of Ferritin and their Electrochemistry

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo; Choi, Sang H.; Lillehei, Peter T.; King, Glen C.; Elliott, James R.; Chu, Sang-Hyon; Park, Yeonjoon; Watt, Gerald D.

2004-01-01

Nanoparticle arrays biologically derived from an electrochemically-controlled site-specific biomineralization were fabricated on a gold substrate through the immobilization process of biomolecules. The work reported herein includes the immobilization of ferritin with various surface modifications, the electrochemical biomineralization of ferritins with different inorganic cores, the fabrication of self-assembled arrays with the immobilized ferritin, and the electrochemical characterization of various core materials. Protein immobilization on the substrate is achieved by anchoring ferritins with dithiobis-N-succinimidyl propionate (DTSP). A reconstitution process of electrochemical site-specific biomineralization with a protein cage loads ferritins with different core materials such as Pt, Co, Mn, and Ni. The ferritin acts as a nano-scale template, a biocompatible cage, and a separator between the nanoparticles. The nano-sized metalcored ferritins on a gold substrate displayed a good electrochemical activity for the electron transport and storage, which is suitable for bioelectronics applications such as biofuel cell, bionanobattery, biosensors, etc. Keywords: Ferritin, immobilization, site-specific reconstitution, biomineralization, and bioelectronics

Extraordinary optical transmission in nanopatterned ultrathin metal films without holes

DOE PAGES

Peer, Akshit; Biswas, Rana

2016-02-01

In this study, we experimentally and theoretically demonstrate that a continuous gold film on a periodically textured substrate exhibits extraordinary optical transmission, even though no holes were etched in the film. Our film synthesis started by nanoimprinting a periodic array of nanocups with a period of ~750 nm on a polystyrene film over a glass substrate. A thin non-conformal gold film was sputter-deposited on the polystyrene by angle-directed deposition. The gold film was continuous with spatial thickness variation, the film being thinnest at the bottom of the nanocup. Measurements revealed an extraordinary transmission peak at a wavelength just smaller thanmore » the period, with an enhancement of ~2.5 compared to the classically expected value. Scattering matrix simulations model well the transmission and reflectance measurements when an ultrathin gold layer (~5 nm), smaller than the skin depth is retained at the bottom of the nanocups. Electric field intensities are enhanced by >100 within the nanocup, and ~40 in the ultrathin gold layer causing transmission through it. We show a wavelength red-shift of ~30 nm in the extraordinary transmission peak when the nanocups are coated with a thin film of a few nanometers, which can be utilized for biosensing. The continuous corrugated metal films are far simpler structures to observe extraordinary transmission, circumventing the difficult process of etching the metal film. Such continuous metal films with ultrathin regions are simple platforms for non-linear optics, plasmonics, and biological and chemical sensing.« less

Metal-assisted exfoliation (MAE): green process for transferring graphene to flexible substrates and templating of sub-nanometer plasmonic gaps (Presentation Recording)

NASA Astrophysics Data System (ADS)

Zaretski, Aliaksandr V.; Marin, Brandon C.; Moetazedi, Herad; Dill, Tyler J.; Jibril, Liban; Kong, Casey; Tao, Andrea R.; Lipomi, Darren J.

2015-09-01

This paper describes a new technique, termed "metal-assisted exfoliation," for the scalable transfer of graphene from catalytic copper foils to flexible polymeric supports. The process is amenable to roll-to-roll manufacturing, and the copper substrate can be recycled. We then demonstrate the use of single-layer graphene as a template for the formation of sub-nanometer plasmonic gaps using a scalable fabrication process called "nanoskiving." These gaps are formed between parallel gold nanowires in a process that first produces three-layer thin films with the architecture gold/single-layer graphene/gold, and then sections the composite films with an ultramicrotome. The structures produced can be treated as two gold nanowires separated along their entire lengths by an atomically thin graphene nanoribbon. Oxygen plasma etches the sandwiched graphene to a finite depth; this action produces a sub-nanometer gap near the top surface of the junction between the wires that is capable of supporting highly confined optical fields. The confinement of light is confirmed by surface-enhanced Raman spectroscopy measurements, which indicate that the enhancement of the electric field arises from the junction between the gold nanowires. These experiments demonstrate nanoskiving as a unique and easy-to-implement fabrication technique that is capable of forming sub-nanometer plasmonic gaps between parallel metallic nanostructures over long, macroscopic distances. These structures could be valuable for fundamental investigations as well as applications in plasmonics and molecular electronics.

Rational Design in Catalysis: A Mechanistic Study of β-Hydride Eliminations in Gold(I) and Gold(III) Complexes Based on Features of the Reaction Valley.

PubMed

Castiñeira Reis, Marta; López, Carlos Silva; Kraka, Elfi; Cremer, Dieter; Faza, Olalla Nieto

2016-09-06

β-Hydride eliminations for ethylgold(III) dichloride complexes are identified as reactions with an unusually long prechemical stage corresponding to the conformational preparation of the reaction complex and spanning six phases. The prechemical process is characterized by a geared rotation of the L-Au-L group (L = Cl) driving methyl group rotation and causing a repositioning of the ligands. This requires more than 28 kcal/mol of the total barrier of 34.0 kcal/mol, according to the unified reaction valley approach, which also determines that the energy requirements of the actual chemical process leading to the β-elimination product are only about 5.5 kcal/mol. A detailed mechanistic analysis was used as a basis for a rational design of substrates (via substituents on the ethyl group) and/or ligands, which can significantly reduce the reaction barrier. This strategy takes advantage of either a higher trans activity of the ligands or a tuned electronic demand of the ethyl group. The β-hydride elimination of gold(I) was found to suffer from strong Coulomb and exchange repulsion when a positively charged hydrogen atom enforces a coordination position in a d(10)-configured gold atom, thus triggering an unassisted σ-π Au(I)-C conversion.

Biochemical component identification by plasmonic improved whispering gallery mode optical resonance based sensor

NASA Astrophysics Data System (ADS)

Saetchnikov, Vladimir A.; Tcherniavskaia, Elina A.; Saetchnikov, Anton V.; Schweiger, Gustav; Ostendorf, Andreas

2014-05-01

Experimental data on detection and identification of variety of biochemical agents, such as proteins, microelements, antibiotic of different generation etc. in both single and multi component solutions under varied in wide range concentration analyzed on the light scattering parameters of whispering gallery mode optical resonance based sensor are represented. Multiplexing on parameters and components has been realized using developed fluidic sensor cell with fixed in adhesive layer dielectric microspheres and data processing. Biochemical component identification has been performed by developed network analysis techniques. Developed approach is demonstrated to be applicable both for single agent and for multi component biochemical analysis. Novel technique based on optical resonance on microring structures, plasmon resonance and identification tools has been developed. To improve a sensitivity of microring structures microspheres fixed by adhesive had been treated previously by gold nanoparticle solution. Another technique used thin film gold layers deposited on the substrate below adhesive. Both biomolecule and nanoparticle injections caused considerable changes of optical resonance spectra. Plasmonic gold layers under optimized thickness also improve parameters of optical resonance spectra. Biochemical component identification has been also performed by developed network analysis techniques both for single and for multi component solution. So advantages of plasmon enhancing optical microcavity resonance with multiparameter identification tools is used for development of a new platform for ultra sensitive label-free biomedical sensor.

Development of gold nanoparticle-aptamer-based LSPR sensing chips for the rapid detection of Salmonella typhimurium in pork meat.

PubMed

Oh, Seo Yeong; Heo, Nam Su; Shukla, Shruti; Cho, Hye-Jin; Vilian, A T Ezhil; Kim, Jinwoon; Lee, Sang Yup; Han, Young-Kyu; Yoo, Seung Min; Huh, Yun Suk

2017-08-31

A non-labeled, portable plasmonic biosensor-based device was developed to enable the ultra-sensitive and selective detection of Salmonella typhimurium in pork meat samples. Specifically, a plasmonic sensor, using the self-assembly of gold nanoparticles (AuNPs) to achieve a regulated diameter of 20 nm for the AuNP monolayers, was used to conduct high-density deposition on a transparent substrate, which produced longitudinal wavelength extinction shifts via a localized surface plasmon resonance (LSPR) signal. The developed aptamers conjugated to the LSPR sensing chips revealed an ultra-sensitive upper limit of detection (LOD) of approximately 10 4 cfu/mL for S. typhimurium in pure culture under the optimal assay conditions, with a total analysis time of 30-35 min. When the LSPR sensing chips were applied on artificially contaminated pork meat samples, S. typhimurium in the spiked pork meat samples was also detected at an LOD of 1.0 × 10 4 cfu/mL. The developed method could detect S. typhimurium in spiked pork meat samples without a pre-enrichment step. Additionally, the LSPR sensing chips developed against S. typhimurium were not susceptible to any effect of the food matrix or background contaminant microflora. These findings confirmed that the developed gold nanoparticle-aptamer-based LSPR sensing chips could facilitate sensitive detection of S. typhimurium in food samples.

Investigation into the effect of plasma pretreatment on the adhesion of parylene to various substrates

NASA Technical Reports Server (NTRS)

Riley, T.; Mahuson, T. C.; Seibert, K.

1979-01-01

A procedure is described for using argon and oxygen plasmas to promote adhesion of parylene coatings upon many difficult-to-bond substrates. Substrates investigated were gold, nickel, kovar, teflon (FEP), kapton, silicon, tantalum, titanium, and tungsten. Without plasma treatment, 180 deg peel tests yield a few g/cm (oz/in) strengths. With dc plasma treatment in the deposition chamber, followed by coating, peel strengths are increased by one to two orders of magnitude.

Temperature Dependent Performance of Coplanar Waveguide (CPW) on Substrates of Various Materials

NASA Technical Reports Server (NTRS)

Taub, Susan R.; Young, Paul

1994-01-01

The attenuation (a) and effective dielectric constant (E(sub eff)) of Coplanar Waveguide (CPW) transmission lines on high-resistivity silicon and diamond substrates as a function of both temperature and frequency are presented. The technique used to obtain the values for a and E(sub eff) involves the use of a unique cryogenic probe station designed and built by NASA. Attenuation of gold CPW lines on diamond substrates is compared with that of superconducting CPW lines.

Self-Positioned Nanosized Mask for Transparent and Flexible Ferroelectric Polymer Nanodiodes Array.

PubMed

Hyun, Seung; Kwon, Owoong; Choi, Chungryong; Vincent Joseph, Kanniyambatti L; Kim, Yunseok; Kim, Jin Kon

2016-10-12

High density arrays of ferroelectric polymer nanodiodes have gained strong attention for next-generation transparent and flexible nonvolatile resistive memory. Here, we introduce a facile and innovative method to fabricate ferroelectric polymer nanodiode array on an ITO-coated poly(ethylene terephthalate) (PET) substrate by using block copolymer self-assembly and oxygen plasma etching. First, polystyrene-block-poly(2-vinylpyridine) copolymer (PS-b-P2VP) micelles were spin-coated on poly(vinylidene fluoride-ran-trifluoroethylene) copolymer (P(VDF-TrFE)) film/ITO-coated PET substrate. After the sample was immersed in a gold precursor (HAuCl 4 ) containing solution, which strongly coordinates with nitrogen group in P2VP, oxygen plasma etching was performed. During the plasma etching, coordinated gold precursors became gold nanoparticles (GNPs), which successfully acted as self-positioned etching mask to fabricate a high density array of P(VDF-TrFE)) nanoislands with GNP at the top. Each nanoisland shows clearly individual diode property, as confirmed by current-voltage (I-V) curve. Furthermore, due to the transparent and flexible nature of P(VDF-TrFE)) nanoisland as well as the substrate, the P(VDF-TrFE) nanodiode array was highly tranparent, and the diode property was maintained even after a large number of bendings (for instance, 1000 times). The array could be used as the next-generation tranparent and flexible nonvolatile memory device.

Optimized Model Surfaces for Advanced Atomic Force Microscopy Studies of Surface Nanobubbles.

PubMed

Song, Bo; Zhou, Yi; Schönherr, Holger

2016-11-01

The formation of self-assembled monolayers (SAMs) of binary mixtures of 16-mercaptohexadecanoic acid (MHDA) and 1-octadecanethiol (ODT) on ultraflat template-stripped gold (TSG) surfaces was systematically investigated to clarify the assembly behavior, composition, and degree of possible phase segregation in light of atomic force microscopy (AFM) studies of surface nanobubbles on these substrates. The data for SAMs on TSG were compared to those obtained by adsorption on rough evaporated gold, as reported in a previous study. Quartz crystal microbalance and surface plasmon resonance data acquired in situ on TSG indicate that similar to SAM formation on conventional evaporated gold substrates ODT and MHDA form monolayers and bilayers, respectively. The second layer on MHDA, whose formation is attributed to hydrogen bonding, can be easily removed by adequate rinsing with water. The favorable agreement of the grazing incidence reflection Fourier transform infrared (GIR FTIR) spectroscopy and contact angle data analyzed with the Israelachvili-Gee model suggests that the binary SAMs do not segregate laterally. This conclusion is fully validated by high-resolution friction force AFM observations down to a length scale of 8-10 nm, which is much smaller than the typical observed surface nanobubble radii. Finally, correspondingly functionalized TSG substrates are shown to be valuable supports for studying surface nanobubbles by AFM in water and for addressing the relation between surface functionality and nanobubble formation and properties.

Fabrication and characterization of homogeneous surface-enhanced Raman scattering substrates by single pulse UV-laser treatment of gold and silver films.

PubMed

Christou, Konstantin; Knorr, Inga; Ihlemann, Jürgen; Wackerbarth, Hainer; Beushausen, Volker

2010-12-07

The fabrication of SERS-active substrates, which offer high enhancement factors as well as spatially homogeneous distribution of the enhancement, plays an important role in the expansion of surface-enhanced Raman scattering (SERS) spectroscopy to a powerful, quantitative, and noninvasive measurement technique for analytical applications. In this paper, a novel method for the fabrication of SERS-active substrates by laser treatment of 20, 40, and 60 nm thick gold and of 40 nm thick silver films supported on quartz glass is presented. Single 308 nm UV-laser pulses were applied to melt the thin gold and silver films. During the cooling process of the noble metal, particles were formed. The particle size and density were imaged by atomic force microscopy. By varying the fluence, the size of the particles can be controlled. The enhancement factors of the nanostructures were determined by recording self-assembled monolayers of benzenethiol. The intensity of the SERS signal from benzenethiol is correlated to the mean particle size and thus to the fluence. Enhancement factors up to 10(6) with a high reproducibility were reached. Finally we have analyzed the temperature dependence of the SERS effect by recording the intensity of benzenethiol vibrations from 300 to 120 K. The temperature dependence of the SERS effect is discussed with regard to the metal properties.

Preferred orientations of laterally grown silicon films over amorphous substrates using the vapor–liquid–solid technique

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

LeBoeuf, J. L., E-mail: jerome.leboeuf@mail.mcgill.ca; Brodusch, N.; Gauvin, R.

2014-12-28

A novel method has been optimized so that adhesion layers are no longer needed to reliably deposit patterned gold structures on amorphous substrates. Using this technique allows for the fabrication of amorphous oxide templates known as micro-crucibles, which confine a vapor–liquid–solid (VLS) catalyst of nominally pure gold to a specific geometry. Within these confined templates of amorphous materials, faceted silicon crystals have been grown laterally. The novel deposition technique, which enables the nominally pure gold catalyst, involves the undercutting of an initial chromium adhesion layer. Using electron backscatter diffraction it was found that silicon nucleated in these micro-crucibles were 30%more » single crystals, 45% potentially twinned crystals and 25% polycrystals for the experimental conditions used. Single, potentially twinned, and polycrystals all had an aversion to growth with the (1 0 0) surface parallel to the amorphous substrate. Closer analysis of grain boundaries of potentially twinned and polycrystalline samples revealed that the overwhelming majority of them were of the 60° Σ3 coherent twin boundary type. The large amount of coherent twin boundaries present in the grown, two-dimensional silicon crystals suggest that lateral VLS growth occurs very close to thermodynamic equilibrium. It is suggested that free energy fluctuations during growth or cooling, and impurities were the causes for this twinning.« less

Electrochemistry and speciation of Au(+) in a deep eutectic solvent: growth and morphology of galvanic immersion coatings.

PubMed

Ballantyne, Andrew D; Forrest, Gregory C H; Frisch, Gero; Hartley, Jennifer M; Ryder, Karl S

2015-11-11

In this study we compare the electrochemical and structural properties of three gold salts AuCl, AuCN and KAu(CN)2 in a Deep Eutectic Solvent (DES) electrolyte (Ethaline 200) in order to elucidate factors affecting the galvanic deposition of gold coatings on nickel substrates. A chemically reversible diffusion limited response was observed for AuCl, whereas AuCN and KAu(CN)2 showed much more complicated, kinetically limited responses. Galvanic exchange reactions were performed on nickel substrates from DES solutions of the three gold salts; the AuCN gave a bright gold coating, the KAu(CN)2 solution give a visibly thin coating, whilst the coating from AuCl was dull, friable and poorly adhesive. This behaviour was rationalised by the differing speciation for each of these compounds, as evidenced by EXAFS methods. Analysis of EXAFS data shows that AuCl forms the chlorido-complex [AuCl2](-), AuCN forms a mixed [AuCl(CN)](-) species, whereas KAu(CN)2 maintains its [Au(CN)2](-) structure. The more labile Cl(-) enables easier reduction of Au when compared to the tightly bound cyanide species, hence leading to slower kinetics of deposition and differing electrochemical behaviour. We conclude that metal speciation in DESs is a function of the initial metal salt and that this has a strong influence on the mechanism and rate of growth, as well as on the morphology of the metal deposit obtained. In addition, these coatings are also extremely promising from a technological perspective as Electroless Nickel Immersion Gold (ENIG) finishes in the printed circuit board (PCB) industry, where the elimination of acid in gold plating formulation could potentially lead to more reliable coatings. Consequently, these results are both significant and timely.

Active substrates improving sensitivity in biomedical fluorescence microscopy

NASA Astrophysics Data System (ADS)

Le Moal, E.; Leveque-Fort, S.; Fort, E.; Lacharme, J.-P.; Fontaine-Aupart, M.-P.; Ricolleau, C.

2005-08-01

Fluorescence is widely used as a spectroscopic tool or for biomedical imaging, in particular for DNA chips. In some cases, detection of very low molecular concentrations and precise localization of biomarkers are limited by the weakness of the fluorescence signal. We present a new method based on sample substrates that improve fluorescence detection sensitivity. These active substrates consist in glass slides covered with metal (gold or silver) and dielectric (alumina) films and can directly be used with common microscope set-up. Fluorescence enhancement affects both excitation and decay rates and is strongly dependant on the distance to the metal surface. Furthermore, fluorescence collection is improved since fluorophore emission lobes are advantageously modified close to a reflective surface. Finally, additional improvements are achieved by structuring the metallic layer. Substrates morphology was mapped by Atomic Force Microscopy (AFM). Substrates optical properties were studied using mono- and bi-photonic fluorescence microscopy with time resolution. An original set-up was implemented for spatial radiation pattern's measurement. Detection improvement was then tested on commercial devices. Several biomedical applications are presented. Enhancement by two orders of magnitude are achieved for DNA chips and signal-to-noise ratio is greatly increased for cells imaging.

1-butanethiol vapor sensing based on gold nanoparticle immobilized on glass slide by digital color analysis

NASA Astrophysics Data System (ADS)

Shokoufi, Nader; Adeleh, Sara

2017-12-01

We demonstrate that gold nanoparticles (GNPs) immobilized on silanized glass act as an optical sensor that is able to quantify 1-butanethiol vapor. GNPs optical properties in the visible region are dominated by the surface plasmon resonance (SPR). The high affinity between 1-butanethiol and GNPs through Au-s bond leads to change in plasmon feature of GNPs that immobilized on silanized glass and causes absorption decrease at 542 nm in SPR spectrum of GNPs. It can be used as an optical sensor for quantitative detection. In this research, the glass slide surface activated by aminopropyltriethoxysilane (APTES). Spherical GNPs immobilized on silanized glass by silanization agent. The sensor is based on the spectrophotometry and digital color analysis (DCA) through RGB. We monitored R value and linear range 50-700 µM (R 2  =  0.97) with 2.05% relative standard deviation and 26.5 µM value was achieved, for the limit of detection. This method represents advantages of metal gold nanoparticles and solid substrate stability in one package, being inexpensive and low time consuming is another advantage of our method that can be conducted in petrochemical, pharmaceutical industries, and for detection of rotten food in food industries.

Substrate doping: A strategy for enhancing reactivity on gold nanocatalysts by tuning sp bands

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

Mammen, Nisha; Narasimhan, Shobhana; Gironcoli, Stefano de

2015-10-14

We suggest that the reactivity of Au nanocatalysts can be greatly increased by doping the oxide substrate on which they are placed with an electron donor. To demonstrate this, we perform density functional theory calculations on a model system consisting of a 20-atom gold cluster placed on a MgO substrate doped with Al atoms. We show that not only does such substrate doping switch the morphology of the nanoparticles from the three-dimensional tetrahedral form to the two-dimensional planar form, but it also significantly lowers the barrier for oxygen dissociation by an amount proportional to the dopant concentration. At a dopingmore » level of 2.78%, the dissociation barrier is reduced by more than half, which corresponds to a speeding up of the oxygen dissociation rate by five orders of magnitude at room temperature. This arises from a lowering in energy of the s and p states of Au. The d states are also lowered in energy, however, this by itself would have tended to reduce reactivity. We propose that a suitable measure of the reactivity of Au nanoparticles is the difference in energy of sp and d states.« less

Strain Multiplexed Metasurface Holograms on a Stretchable Substrate.

PubMed

Malek, Stephanie C; Ee, Ho-Seok; Agarwal, Ritesh

2017-06-14

We demonstrate reconfigurable phase-only computer-generated metasurface holograms with up to three image planes operating in the visible regime fabricated with gold nanorods on a stretchable polydimethylsiloxane substrate. Stretching the substrate enlarges the hologram image and changes the location of the image plane. Upon stretching, these devices can switch the displayed holographic image between multiple distinct images. This work opens up the possibilities for stretchable metasurface holograms as flat devices for dynamically reconfigurable optical communication and display. It also confirms that metasurfaces on stretchable substrates can serve as platform for a variety of reconfigurable optical devices.

Real-Time Plasmonic Monitoring of Single Gold Amalgam Nanoalloy Electrochemical Formation and Stripping.

PubMed

Wang, Jun-Gang; Fossey, John S; Li, Meng; Xie, Tao; Long, Yi-Tao

2016-03-01

Direct electrodeposition of mercury onto gold nanorods on an ITO substrate, without reducing agents, is reported. The growth of single gold amalgam nanoalloy particles and subsequent stripping was monitored in real-time monitoring by plasmonic effects and single-nanoparticle dark-field spectroelectrochemistry techniques. Time-dependent scattering spectral information conferred insight into the growth and stripping mechanism of a single nanoalloy particle. Four critical stages were observed: First, rapid deposition of Hg atoms onto Au nanorods; second, slow diffusion of Hg atoms into Au nanorods; third, prompt stripping of Hg atoms from Au nanorods; fourth, moderate diffusion from the inner core of Au nanorods. Under high Hg(2+) concentrations, homogeneous spherical gold amalgam nanoalloys were obtained. These results demonstrate that the morphology and composition of individual gold amalgam nanoalloys can be precisely regulated electrochemically. Moreover, gold amalgam nanoalloys with intriguing optical properties, such as modulated plasmonic lifetimes and quality factor Q, could be obtained. This may offer opportunities to extend applications in photovoltaic energy conversion and chemical sensing.

Transmission Measurement of the Third-Order Susceptibility of Gold

NASA Technical Reports Server (NTRS)

Smith, David D.; Yoon, Youngkwon; Boyd, Robert W.; Crooks, Richard M.; George, Michael

1999-01-01

Gold nanoparticle composites are known to display large optical nonlinearities. In order to assess the validity of generalized effective medium theories (EMT's) for describing the linear and nonlinear optical properties of metal nanoparticle composites, knowledge of the linear and nonlinear susceptibilities of the constituent materials is a prerequisite. In this study the inherent nonlinearity of the metal is measured directly (rather than deduced from a suitable EMT) using a very thin gold film. Specifically, we have used the z-scan technique at a wavelength near the transmission window of bulk gold to measure the third-order susceptibility of a continuous thin gold film deposited on a quartz substrate surface-modified with a self-assembled monolayer to promote adhesion and uniformity without affecting the optical properties. We compare our results with predictions which ascribe the nonlinear response to a Fermi-smearing mechanism. Further, we note that the sign of the nonlinear susceptibility is reversed from that of gold nanoparticle composites.

Simple Fabrication of Gold Nanobelts and Patterns

PubMed Central

Zhang, Renyun; Hummelgård, Magnus; Olin, Håkan

2012-01-01

Gold nanobelts are of interest in several areas; however, there are only few methods available to produce these belts. We report here on a simple evaporation induced self-assembly (EISA) method to produce porous gold nanobelts with dimensions that scale across nanometer (thickness ∼80 nm) and micrometer (width ∼20 µm), to decimeter (length ∼0.15 m). The gold nanobelts are well packed on the beaker wall and can be easily made to float on the surface of the solution for depositing onto other substrates. Microscopy showed that gold nanobelts had a different structure on the two sides of the belt; the density of gold nanowires on one side was greater than on the other side. Electrical measurements showed that these nanobelts were sensitive to compressive or tensile forces, indicating a potential use as a strain sensor. The patterned nanobelts were further used as a template to grow ZnO nanowires for potential use in applications such as piezo-electronics. PMID:22291962

Optimising the visibility of graphene and graphene oxide on gold with multilayer heterostructures

NASA Astrophysics Data System (ADS)

Velický, Matěj; Hendren, William R.; Donnelly, Gavin E.; Katzen, Joel M.; Bowman, Robert M.; Huang, Fumin

2018-07-01

Metals have been increasingly used as substrates in devices based on two-dimensional (2D) materials. However, the high reflectivity of bulk metals results in low optical contrast (<3%) and therefore poor visibility of transparent mono- and few-layer 2D materials on these surfaces. Here we demonstrate that by engineering the complex reflectivity of a purpose-designed multilayer heterostructure composed of thin Au films (2–8 nm) on SiO2/Si substrate, the optical contrast of graphene and graphene oxide (GO) can be significantly enhanced in comparison to bulk Au, up to about 3 and 5 times, respectively. In particular, we achieved ∼17% optical contrast for monolayer GO, which is even 2 times higher than that on bare SiO2/Si substrate. The experimental results are in good agreement with theoretical simulations. This concept is demonstrated for Au, but the methodology is applicable to other metals and can be adopted to design a variety of high-contrast metallic substrates. This will facilitate research and applications of 2D materials in areas such as plasmonics, photonics, catalysis and sensors.

Towards an Integrated QR Code Biosensor: Light-Driven Sample Acquisition and Bacterial Cellulose Paper Substrate.

PubMed

Yuan, Mingquan; Jiang, Qisheng; Liu, Keng-Ku; Singamaneni, Srikanth; Chakrabartty, Shantanu

2018-06-01

This paper addresses two key challenges toward an integrated forward error-correcting biosensor based on our previously reported self-assembled quick-response (QR) code. The first challenge involves the choice of the paper substrate for printing and self-assembling the QR code. We have compared four different substrates that includes regular printing paper, Whatman filter paper, nitrocellulose membrane and lab synthesized bacterial cellulose. We report that out of the four substrates bacterial cellulose outperforms the others in terms of probe (gold nanorods) and ink retention capability. The second challenge involves remote activation of the analyte sampling and the QR code self-assembly process. In this paper, we use light as a trigger signal and a graphite layer as a light-absorbing material. The resulting change in temperature due to infrared absorption leads to a temperature gradient that then exerts a diffusive force driving the analyte toward the regions of self-assembly. The working principle has been verified in this paper using assembled biosensor prototypes where we demonstrate higher sample flow rate due to light induced thermal gradients.

Optimising the visibility of graphene and graphene oxide on gold with multilayer heterostructures.

PubMed

Velický, Matěj; Hendren, William R; Donnelly, Gavin E; Katzen, Joel M; Bowman, Robert M; Huang, Fumin

2018-07-06

Metals have been increasingly used as substrates in devices based on two-dimensional (2D) materials. However, the high reflectivity of bulk metals results in low optical contrast (<3%) and therefore poor visibility of transparent mono- and few-layer 2D materials on these surfaces. Here we demonstrate that by engineering the complex reflectivity of a purpose-designed multilayer heterostructure composed of thin Au films (2-8 nm) on SiO 2 /Si substrate, the optical contrast of graphene and graphene oxide (GO) can be significantly enhanced in comparison to bulk Au, up to about 3 and 5 times, respectively. In particular, we achieved ∼17% optical contrast for monolayer GO, which is even 2 times higher than that on bare SiO 2 /Si substrate. The experimental results are in good agreement with theoretical simulations. This concept is demonstrated for Au, but the methodology is applicable to other metals and can be adopted to design a variety of high-contrast metallic substrates. This will facilitate research and applications of 2D materials in areas such as plasmonics, photonics, catalysis and sensors.

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.

Formation of mono-layered gold nanoparticles in shallow depth of SiO 2 thin film by low-energy negative-ion implantation

NASA Astrophysics Data System (ADS)

Tsuji, H.; Arai, N.; Ueno, K.; Matsumoto, T.; Gotoh, N.; Adachi, K.; Kotaki, H.; Gotoh, Y.; Ishikawa, J.

2006-01-01

Mono-layered gold nanoparticles just below the surface of silicon oxide film have been formed by a gold negative-ion implantation at a very low-energy, where the deviation of implanted atoms was sufficiently narrow comparing to the size of nanoparticles. Gold negative ions were implanted into SiO2 thin films on Si substrate at energies of 35, 15 and 1 keV. The samples were annealed in Ar flow for 1 h at 900 or 1000 °C. Cross-sectional TEM observation for the implantation at 1 keV showed existence of Au nanoparticles aligned in the same depth of 5 nm from the surface. The nanoparticles had almost same diameter of 7 nm. The nanoparticles were found to be gold single crystal from a high-resolution TEM image.

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

Ultrastable gold substrates: Properties of a support for high-resolution electron cryomicroscopy of biological specimens

PubMed Central

Russo, Christopher J.; Passmore, Lori A.

2016-01-01

Electron cryomicroscopy (cryo-EM) allows structure determination of a wide range of biological molecules and specimens. All-gold supports improve cryo-EM images by reducing radiation-induced motion and image blurring. Here we compare the mechanical and electrical properties of all-gold supports to amorphous carbon foils. Gold supports are more conductive, and have suspended foils that are not compressed by differential contraction when cooled to liquid nitrogen temperatures. These measurements show how the choice of support material and geometry can reduce specimen movement by more than an order of magnitude during low-dose imaging. We provide methods for fabrication of all-gold supports and preparation of vitrified specimens. We also analyse illumination geometry for optimal collection of high resolution, low-dose data. Together, the support structures and methods herein can improve the resolution and quality of images from any electron cryomicroscope. PMID:26592474

Large-scale protein/antibody patterning with limiting unspecific adsorption

NASA Astrophysics Data System (ADS)

Fedorenko, Viktoriia; Bechelany, Mikhael; Janot, Jean-Marc; Smyntyna, Valentyn; Balme, Sebastien

2017-10-01

A simple synthetic route based on nanosphere lithography has been developed in order to design a large-scale nanoarray for specific control of protein anchoring. This technique based on two-dimensional (2D) colloidal crystals composed of polystyrene spheres allows the easy and inexpensive fabrication of large arrays (up to several centimeters) by reducing the cost. A silicon wafer coated with a thin adhesion layer of chromium (15 nm) and a layer of gold (50 nm) is used as a substrate. PS spheres are deposited on the gold surface using the floating-transferring technique. The PS spheres were then functionalized with PEG-biotin and the defects by self-assembly monolayer (SAM) PEG to prevent unspecific adsorption. Using epifluorescence microscopy, we show that after immersion of sample on target protein (avidin and anti-avidin) solution, the latter are specifically located on polystyrene spheres. Thus, these results are meaningful for exploration of devices based on a large-scale nanoarray of PS spheres and can be used for detection of target proteins or simply to pattern a surface with specific proteins.

Nanoparticle formation after nanosecond-laser irradiation of thin gold films

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

Ratautas, Karolis; Gedvilas, Mindaugas; Raciukaitis, Gediminas

2012-07-01

Evolution in nanoparticle formation was observed after nanosecond-laser irradiation of thin gold films on a silicon substrate and physical phenomena leading to the formation of nanoparticles were studied. Gold films of different thickness (3, 5, 10, 15, 20, and 25 nm) were evaporated on the silicon (110) substrate and irradiated with the pulsed nanosecond laser using different pulse energies and the number of pulses in a burst. Experimentally morphological changes appeared in the films only when the pulse energy was high enough to initiate the phase transition. The threshold energy density for phase transitions in the films was estimated frommore » the thermal model of the laser beam and sample interaction. With the pulse energy just above the threshold, it was possible to observe evolution of nanoparticle formation from a plane metal film by changing the number of pulses applied, as duration of the pulse burst represented the time how long the liquid phase existed. The final size of nanoparticles was a function of the film thickness and was found to be independent of the pulse energy and the number of pulses.« less

Metallic Nanohole Arrays on Fluoropolymer Substrates as Small Label-Free Real-Time Bioprobes

PubMed Central

Yang, Jiun-Chan; Ji, Jin; Hogle, James M.; Larson, Dale N.

2009-01-01

We describe a nanoplasmonic probing platform that exploits small-dimension (≤ 20 μm2) ordered arrays of subwavelength holes for multiplexed, high spatial resolution, and real-time analysis on biorecognition events. Nanohole arrays are perforated on a super smooth gold surface (roughness RMS < 2.7 Å) attached on a fluoropolymer (FEP) substrate fabricated by a replica technique. The smooth surface of gold provides a superb environment for fabricating nanometer features and uniform immobilization of biomolecules. The refractive index matching between FEP and biological solutions contributes to ∼ 20% improvement on the sensing performance. Spectral studies on a series of small-dimension nanohole arrays from 1 μm2 to 20 μm2 indicate that the plasmonic sensing sensitivity improves as the gold-solution contact area increases. Our results also demonstrate that nanohole arrays with dimension as small as 1 μm2 can be used to effectively detect biomolecular binding events and analyze the binding kinetics. The future scientific opportunities opened by this nanohole platform include highly multiplexed analysis of ligand interactions with membrane proteins on high quality supported lipid bilayers. PMID:18710296

Bottom-up formation of robust gold carbide

PubMed Central

Westenfelder, Benedikt; Biskupek, Johannes; Meyer, Jannik C.; Kurasch, Simon; Lin, Xiaohang; Scholz, Ferdinand; Gross, Axel; Kaiser, Ute

2015-01-01

A new phenomenon of structural reorganization is discovered and characterized for a gold-carbon system by in-situ atomic-resolution imaging at temperatures up to 1300 K. Here, a graphene sheet serves in three ways, as a quasi transparent substrate for aberration-corrected high-resolution transmission electron microscopy, as an in-situ heater, and as carbon supplier. The sheet has been decorated with gold nanoislands beforehand. During electron irradiation at 80 kV and at elevated temperatures, the accumulation of gold atoms has been observed on defective graphene sites or edges as well as at the facets of gold nanocrystals. Both resulted in clustering, forming unusual crystalline structures. Their lattice parameters and surface termination differ significantly from standard gold nanocrystals. The experimental data, supported by electron energy loss spectroscopy and density-functional theory calculations, suggests that isolated gold and carbon atoms form – under conditions of heat and electron irradiation – a novel type of compound crystal, Au-C in zincblende structure. The novel material is metastable, but surprisingly robust, even under annealing condition. PMID:25772348

A spectroscopic study on the interaction between gold nanoparticles and hemoglobin

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

Garabagiu, Sorina, E-mail: sgarabagiu@itim-cj.ro

2011-12-15

Highlights: Black-Right-Pointing-Pointer The interaction was studied using UV-vis and fluorescence spectroscopy. Black-Right-Pointing-Pointer Gold nanoparticles quench the fluorescence emission of hemoglobin solution. Black-Right-Pointing-Pointer The binding and thermodynamic constants were calculated. Black-Right-Pointing-Pointer Major impact: electrochemical applications of the complex onto a substrate. -- Abstract: The interaction between horse hemoglobin and gold nanoparticles was studied using optical spectroscopy. UV-vis and fluorescence spectra show that a spontaneous binding process occurred between hemoglobin and gold nanoparticles. The Soret band of hemoglobin in the presence of gold nanoparticles does not show significant changes, which proves that the protein retained its biological function. A shift to longermore » wavelengths appears in the plasmonic band of gold nanoparticles upon the attachment of hemoglobin molecules. Gold nanoparticles quench the fluorescence emission of tryptophan residues in the structure of hemoglobin. The Stern-Volmer quenching constant, the binding constant and the number of binding sites were also calculated. Thermodynamic parameters indicate that the binding was mainly due to hydrophobic interactions.« less

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

PubMed Central

Hazut, Ori; Agarwala, Arunava; Subramani, Thangavel; Waichman, Sharon; Yerushalmi, Roie

2013-01-01

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms. In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station. PMID:24326774

Advances in maskless and mask-based optical lithography on plastic flexible substrates

NASA Astrophysics Data System (ADS)

Barbu, Ionut; Ivan, Marius G.; Giesen, Peter; Van de Moosdijk, Michel; Meinders, Erwin R.

2009-12-01

Organic flexible electronics is an emerging technology with huge potential growth in the future which is likely to open up a complete new series of potential applications such as flexible OLED-based displays, urban commercial signage, and flexible electronic paper. The transistor is the fundamental building block of all these applications. A key challenge in patterning transistors on flexible plastic substrates stems from the in-plane nonlinear deformations as a consequence of foil expansion/shrinkage, moisture uptake, baking etc. during various processing steps. Optical maskless lithography is one of the potential candidates for compensating for these foil distortions by in-situ adjustment prior to exposure of the new layer image with respect to the already patterned layers. Maskless lithography also brings the added value of reducing the cost-of-ownership related to traditional mask-based tools by eliminating the need for expensive masks. For the purpose of this paper, single-layer maskless exposures at 355 nm were performed on gold-coated poly(ethylenenaphthalate) (PEN) flexible substrates temporarily attached to rigid carriers to ensure dimensional stability during processing. Two positive photoresists were employed for this study and the results on plastic foils were benchmarked against maskless as well as mask-based (ASML PAS 5500/100D stepper) exposures on silicon wafers.

Post-fabrication voltage controlled resonance tuning of nanoscale plasmonic antennas.

PubMed

Lumdee, Chatdanai; Toroghi, Seyfollah; Kik, Pieter G

2012-07-24

Voltage controlled wavelength tuning of the localized surface plasmon resonance of gold nanoparticles on an aluminum film is demonstrated in single particle microscopy and spectroscopy measurements. Anodization of the Al film after nanoparticle deposition forms an aluminum oxide spacer layer between the gold particles and the Al film, modifying the particle-substrate interaction. Darkfield microscopy reveals ring-shaped scattering images from individual Au nanoparticles, indicative of plasmon resonances with a dipole moment normal to the substrate. Single particle scattering spectra show narrow plasmon resonances that can be tuned from ~580 to ~550 nm as the anodization voltage increases to 12 V. All observed experimental trends could be reproduced in numerical simulations. The presented approach could be used as a general postfabrication resonance optimization step of plasmonic nanoantennas and devices.

Surface-enhanced Raman scattering on periodic metal nanotips with tunable sharpness.

PubMed

Linn, Nicholas C; Sun, Chih-Hung; Arya, Ajay; Jiang, Peng; Jiang, Bin

2009-06-03

This paper reports on a scalable bottom-up technology for producing periodic gold nanotips with tunable sharpness as surface-enhanced Raman scattering (SERS) substrates. Inverted silicon pyramidal pits, which are templated from non-close-packed colloidal crystals prepared by a spin-coating technology, are used as structural templates to replicate arrays of polymer nanopyramids with nanoscale sharp tips. The deposition of a thin layer of gold on the polymer nanopyramids leads to the formation of SERS-active substrates with a high enhancement factor (up to 10(8)). The thickness of the deposited metal determines the sharpness of the nanotips and the resulting Raman enhancement factor. Finite-element electromagnetic modeling shows that the nanotips can significantly enhance the local electromagnetic field and the sharpness of nanotips greatly affects the SERS enhancement.

Control of Nanoscale Friction on Gold in an Ionic Liquid by a Potential-Dependent Ionic Lubricant Layer

NASA Astrophysics Data System (ADS)

Sweeney, James; Hausen, Florian; Hayes, Robert; Webber, Grant B.; Endres, Frank; Rutland, Mark W.; Bennewitz, Roland; Atkin, Rob

2012-10-01

The lubricating properties of an ionic liquid on gold surfaces can be controlled through application of an electric potential to the sliding contact. A nanotribology approach has been used to study the frictional behavior of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate ([Py1,4]FAP) confined between silica colloid probes or sharp silica tips and a Au(111) substrate using atomic force microscopy. Friction forces vary with potential because the composition of a confined ion layer between the two surfaces changes from cation-enriched (at negative potentials) to anion-enriched (at positive potentials). This offers a new approach to tuning frictional forces reversibly at the molecular level without changing the substrates, employing a self-replenishing boundary lubricant of low vapor pressure.

3D plasmonic transducer based on gold nanoparticles produced by laser ablation on silica nanowires

NASA Astrophysics Data System (ADS)

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

2016-05-01

Silica two-dimensional substrates and nanowires (NWs) forests have been successfully decorated with Au nanoparticles (NPs) through laser ablation by using a pulsed ArF excimer laser, for sensor applications. A uniform coverage of both substrate surfaces with NPs has been achieved controlling the number of laser pulses. The annealing of the as-deposited particles resulted in a uniform well-defined distribution of spherical NPs with an increased average diameter up to 25 nm. The deposited samples on silica NWs forest present a very good plasmonic resonance which resulted to be very sensitive to the changes of the environment (ethanol/water solutions with increasing concentration of ethanol) allowing the detection of changes on the second decimal digit of the refractive index, demonstrating its potentiality for further biosensing functionalities.

High temperature superconducting YBCO microwave filters

NASA Astrophysics Data System (ADS)

Aghabagheri, S.; Rasti, M.; Mohammadizadeh, M. R.; Kameli, P.; Salamati, H.; Mohammadpour-Aghdam, K.; Faraji-Dana, R.

2018-06-01

Epitaxial thin films of YBCO high temperature superconductor are widely used in telecommunication technology such as microwave filter, antenna, coupler and etc., due to their lower surface resistance and lower microwave loss than their normal conductor counterparts. Thin films of YBCO were fabricated by PLD technique on LAO substrate. Transition temperature and width were 88 K and 3 K, respectively. A filter pattern was designed and implemented by wet photolithography method on the films. Characterization of the filter at 77 K has been compared with the simulation results and the results for a made gold filter. Both YBCO and gold filters show high microwave loss. For YBCO filter, the reason may be due to the improper contacts on the feedlines and for gold filter, low thickness of the gold film has caused the loss increased.

Three-dimensional self-organization of crystalline gold nanoparticles in amorphous alumina

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

Jin Chunming; Zhou Honghui; Wei Wei

Multilayered heterostructures containing gold nanoparticles embedded in amorphous alumina matrices were deposited on silicon (001) substrates using pulsed laser deposition. The three-dimensional ordering of gold nanoparticles within these multilayered heterostructures was investigated using cross-sectional transmission electron microscopy and image Fourier transformation. Self-organization of gold nanoparticles along the vertical direction was observed in films grown at 20 and at 320 deg. C. Self-organization occurred by means of two different growth modes; both vertically correlated growth (top-on-top) and anticorrelated growth (top-on-middle) mechanisms were observed. The results of these studies suggest that the driving force for vertical ordering in this material is relatedmore » to the long-range elastic interactions among the nanoparticles within the growing films.« less

Synthesis and characterization of silicon nanorod on n-type porous silicon.

PubMed

Behzad, Kasra; Mat Yunus, Wan Mahmood; Bahrami, Afarin; Kharazmi, Alireza; Soltani, Nayereh

2016-03-20

This work reports a new method for growing semiconductor nanorods on a porous silicon substrate. After preparation of n-type porous silicon samples, a thin layer of gold was deposited on them. Gold deposited samples were annealed at different temperatures. The structural, thermal, and optical properties of the samples were studied using a field emission scanning electron microscope (FESEM), photoacoustic spectroscopy, and photoluminescence spectroscopy, respectively. FESEM analysis revealed that silicon nanorods of different sizes grew on the annealed samples. Thermal behavior of the samples was studied using photoacoustic spectroscopy. Photoluminescence spectroscopy showed that the emission peaks were degraded by gold deposition and attenuated for all samples by annealing.

One-step synthesis of highly dispersed gold nanocrystals on silica spheres.

PubMed

Phonthammachai, Nopphawan; White, Timothy J

2007-11-06

Highly dispersed gold nanocrystals decorating silica spheres were prepared from HAuCl4 and NaOH via a deposition-precipitation (DP) process, in which the isoelectric point (IEP) of the substrate was adjusted during sphere synthesis by interaction of the surface with ammonia molecules. Through the systematic variation of pH (4-8), reaction temperature (65-96 degrees C), and time (10-30 min), a superior product with small (2-5 nm), homogeneously distributed gold crystals was obtained at pH 7 and a reaction temperature of 96 degrees C. These materials will offer enhanced performance as catalysts and contrast enhancers in biomedical imaging.

Intensity enhancement of vibrational sum frequency generation by gap-mode plasmon resonance

NASA Astrophysics Data System (ADS)

Okuno, Masanari; Tokimoto, Taichi; Eguchi, Miharu; Kano, Hideaki; Ishibashi, Taka-aki

2015-10-01

A metal sphere-plane structure consisting of gold nanoparticles, p-methylbenzenethiol and a gold substrate was measured by vibrational sum frequency generation spectroscopy with four excitation wavelengths, 630, 680, 720, and 780 nm. The enhancement factors of Raman signals were estimated to be 250 and 104 for the 532 and 647 nm excitation. Contrastingly, we found that the enhancements of VSFG signals were much smaller, a factor of 5 at maximum. We speculate that the small enhancement factor of VSFG signals is due to the coherent nature of the VSFG process or the extinction of the infrared laser by the gold nanoparticles.

Surface Functionalization of Diamond Films by Photoreaction of Elemental Sulfur and Their Surface Properties

NASA Astrophysics Data System (ADS)

Nakamura, Takako; Ohana, Tsuguyori

2012-08-01

A useful method for direct sulfurization of diamond film surfaces by photoreaction of elemental sulfur was developed. The introduction of thiol groups onto the diamond films was confirmed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and scanning electron microscopy (SEM) analyses. The sulfur-modified diamond films attached to gold nanoparticles by self-assembly. The degrees of thiol group introduction and gold attachment were found to depend on photoirradiation time by monitoring by XPS. The gold-modified diamond film was observed to act as a surface-enhanced Raman scattering substrate for measurement of picric acid.

System-based approach for an advanced drug delivery platform

NASA Astrophysics Data System (ADS)

Kulinsky, Lawrence; Xu, Han; Tsai, Han-Kuan A.; Madou, Marc

2006-03-01

Present study is looking at the problem of integrating drug delivery microcapsule, a bio-sensor, and a control mechanism into a biomedical drug delivery system. A wide range of medical practices from cancer therapy to gastroenterological treatments can benefit from such novel bio-system. Drug release in our drug delivery system is achieved by electrochemically actuating an array of polymeric valves on a set of drug reservoirs. The valves are bi-layer structures, made in the shape of a flap hinged on one side to a valve seat, and consisting of thin films of evaporated gold and electrochemically deposited polypyrrole (PPy). These thin PPy(DBS) bi-layer flaps cover access holes of underlying chambers micromachined in a silicon substrate. Chromium and polyimide layers are applied to implement "differential adhesion" to obtain a voltage induced deflection of the bilayer away from the drug reservoir. The Cr is an adhesion-promoting layer, which is used to strongly bind the gold layer down to the substrate, whereas the gold adheres weakly to polyimide. Drug actives (dry or wet) were pre-stored in the chambers and their release is achieved upon the application of a small bias (~ 1V). Negative voltage causes cation adsorption and volume change in PPy film. This translates into the bending of the PPy/Au bi-layer actuator and release of the drug from reservoirs. This design of the drug delivery module is miniaturized to the dimensions of 200μm valve diameter. Galvanostatic and potentiostatic PPy deposition methods were compared, and potentiostatic deposition method yields film of more uniform thickness. PPy deposition experiments with various pyrrole and NaDBS concentrations were also performed. Glucose biosensor based on glucose oxidase (GOx) embedded in the PPy matrix during elechtrochemical deposition was manufactured and successfully tested. Multiple-drug pulsatile release and continuous linear release patterns can be implemented by controlling the operation of an array of valves. Varying amounts of drugs, together with more complex controlling strategies would allow creation of more complex drug delivery patterns.

Substrate solder barriers for semiconductor epilayer growth

DOEpatents

Drummond, T.J.; Ginley, D.S.; Zipperian, T.E.

1987-10-23

During the growth of compound semiconductors by epitaxial processes, substrates are typically mounted to a support. In molecular beam epitaxy, mounting is done using indium as a solder. This method has two drawbacks: the indium reacts with the substrate, and it is difficult to uniformly wet the back of a large diameter substrate. Both of these problems have been successfully overcome by sputter coating the back of the substrate with a thin layer of tungsten carbide or tungsten carbide and gold. In addition to being compatible with the growth of high quality semiconductor epilayers this coating is also inert in all standard substate cleaning etchants used for compound semiconductors, and provides uniform distribution of energy in radiant heating. 1 tab.

Modeling of the rough spherical nanoparticles manipulation on a substrate based on the AFM nanorobot

NASA Astrophysics Data System (ADS)

Zakeri, M.; Faraji, J.

2014-12-01

In this paper, dynamic behavior of the rough spherical micro/nanoparticles during pulling/pushing on the flat substrate has been investigated and analyzed. For this purpose, at first, two hexagonal roughness models (George and Cooper) were studied and then evaluations for adhesion force were determined for rough particle manipulation on flat substrate. These two models were then changed by using of the Rabinovich theory. Evaluations were determined for contact adhesion force between rough particle and flat substrate; depth of penetration evaluations were determined by the Johnson-Kendall-Roberts contact mechanic theory and the Schwartz method and according to Cooper and George roughness models. Then, the novel contact theory was used to determine a dynamic model for rough micro/nanoparticle manipulation on flat substrate. Finally, simulation of particle dynamic behavior was implemented during pushing of rough spherical gold particles with radii of 50, 150, 400, 600, and 1,000 nm. Results derived from simulations of particles with several rates of roughness on flat substrate indicated that compared to results for flat particles, inherent roughness on particles might reduce the rate of critical force needed for sliding and rolling given particles. Given a fixed radius for roughness value and increased roughness height, evaluations for sliding and rolling critical forces showed greater reduction. Alternately, the rate of critical force was shown to reduce relative to an increased roughness radius. With respect to both models, based on the George roughness model, the predicted rate of adhesion force was greater than that determined in the Cooper roughness model, and as a result, the predicted rate of critical force based on the George roughness model was closer to the critical force value of flat particle.

Coated substrates and process

DOEpatents

Chu, Wei-kan; Childs, Charles B.

1991-01-01

Disclosed herein is a coated substrate and a process for forming films on substrates and for providing a particularly smooth film on a substrate. The method of this invention involves subjecting a surface of a substrate to contact with a stream of ions of an inert gas having sufficient force and energy to substantially change the surface characteristics of said substrate, and then exposing a film-forming material to a stream of ions of an inert gas having sufficient energy to vaporize the atoms of said film-forming material and to transmit the vaporized atoms to the substrate surface with sufficient force to form a film bonded to the substrate. This process is particularly useful commercially because it forms strong bonds at room temperature. This invention is particularly useful for adhering a gold film to diamond and forming ohmic electrodes on diamond, but also can be used to bond other films to substrates.

Combined Thermochromic And Plasmonic: Optical Responses In Novel Nanocomposite Au-VO{sub 2} Films Prepared By RF Inverted Cylindrical Magnetron Sputtering

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

Kana, J. B. Kana; Department of physics, University of Yaounde I, P.O. Box 812 Yaounde; Ndjaka, J. M.

2008-09-23

We prepared gold/Vanadium dioxide nanocomposites thin films by the rf reactive inverted cylindrical magnetron sputtering (ICMS) for the first time and report their enhanced surface plasmon resonance (SPR) tunable shift reversibility. ICMS has been attracting much attention for its ability for uniform coating of three-dimensional objects and high-rate deposition of dielectric materials. To investigate the optical properties of gold nanoparticles embedded in an active matrix (VO{sub 2}) composite film was synthesized on corning glass substrates for several substrate temperatures ranging from 400 deg. C to 600 deg. C. The X-ray diffraction results demonstrated that the Au and VO{sub 2} weremore » well crystallized. The optical transmission properties were measured from 300nm to 1100nm and the absorption peak due to the surface plasmon resonance (SPR) of Au nanoparticles were observed. Under external temperature stimuli, the tunable reversibility of the SPR shift was observed when the nanocomposites temperature varies from 20 deg. C to 100 deg. C. The enhancement of this shift of SPR was observed as the substrate temperature increases and it was found that the shift of SPR increased rapidly with increasing substrate temperature but then remained constant at {approx}57 nm for substrate temperature higher than 500 deg. C.« less

Molecular response of Escherichia coli adhering onto nanoscale topography

NASA Astrophysics Data System (ADS)

Rizzello, Loris; Galeone, Antonio; Vecchio, Giuseppe; Brunetti, Virgilio; Sabella, Stefania; Pompa, Pier Paolo

2012-10-01

Bacterial adhesion onto abiotic surfaces is an important issue in biology and medicine since understanding the bases of such interaction represents a crucial aspect in the design of safe implant devices with intrinsic antibacterial characteristics. In this framework, we investigated the effects of nanostructured metal substrates on Escherichia coli adhesion and adaptation in order to understand the bio-molecular dynamics ruling the interactions at the interface. In particular, we show how highly controlled nanostructured gold substrates impact the bacterial behavior in terms of morphological changes and lead to modifications in the expression profile of several genes, which are crucially involved in the stress response and fimbrial synthesis. These results mainly demonstrate that E. coli cells are able to sense even slight changes in surface nanotopography and to actively respond by activating stress-related pathways. At the same time, our findings highlight the possibility of designing nanoengineered substrates able to trigger specific bio-molecular effects, thus opening the perspective of smartly tuning bacterial behavior by biomaterial design.

Gold nanoparticles with different capping systems: an electronic and structural XAS analysis.

PubMed

López-Cartes, C; Rojas, T C; Litrán, R; Martínez-Martínez, D; de la Fuente, J M; Penadés, S; Fernández, A

2005-05-12

Gold nanoparticles (NPs) have been prepared with three different capping systems: a tetralkylammonium salt, an alkanethiol, and a thiol-derivatized neoglycoconjugate. Also gold NPs supported on a porous TiO(2) substrate have been investigated. X-ray absorption spectroscopy (XAS) has been used to determine the electronic behavior of the different capped/supported systems regarding the electron/hole density of d states. Surface and size effects, as well as the role of the microstructure, have been also studied through an exhaustive analysis of the EXAFS (extended X-ray absorption fine structure) data. Very small gold NPs functionalized with thiol-derivatized molecules show an increase in d-hole density at the gold site due to Au-S charge transfer. This effect is overcoming size effects (which lead to a slightly increase of the d-electron density) for high S:Au atomic ratios and core-shell microstructures where an atomically abrupt Au-S interface likely does not exist. It has been also shown that thiol functionalization of very small gold NPs is introducing a strong distortion as compared to fcc order. To the contrary, electron transfer from reduced support oxides to gold NPs can produce a higher increase in d-electron density at the gold site, as compared to naked gold clusters.

Ejection of nanoclusters from gold nanoislet layers by 38 keV Au ions in the elastic stopping mode.

PubMed

Baranov, I A; Della-Negra, S; Domaratsky, V P; Chemezov, A V; Kirillov, S N; Novikov, A C; Obnorsky, V V; Pautrat, M; Urbassek, H M; Wien, K; Yarmiychuk, S V; Zhurkin, E E

2009-07-01

Total absolute yields of the ejected gold were obtained regardless of the type of the particles are--atoms, clusters, nanoclusters,--as well as absolute yields of gold nanoclusters, from nanoislet gold targets under bombardment by monoatomic gold ions at 45 degrees to the target surface with the energy 38 keV, i.e., in the "purely" elastic stopping mode -6 keV/nm up to the fluence of 4 x 10(12) cm2. Three targets had gold nanoislets on the substrate surface: 2-12 nm; -18 nm; -35 nm, the most probable sizes being 7.1; 9.4; 17.5 nm respectively. The part of the surface area covered with gold was known. Total transfer of gold was determined by means of the neutron-activation analysis and decreased from 450 to 20 at/ion. The number of the ejected gold nanoclusters was determined using TEM and decreased from approximately 0.06 to < 0.01 per one 38 keV Au ion with the increase of the most probable sizes of the nanoislets on the target from 7.1 to 17.5 nm. The yields appeared to be surprisingly high, which is of scientific and practical importance. Tentative estimations were made using molecular dynamics simulations.

Enhanced optical output power of blue light-emitting diodes with quasi-aligned gold nanoparticles.

PubMed

Jin, Yuanhao; Li, Qunqing; Li, Guanhong; Chen, Mo; Liu, Junku; Zou, Yuan; Jiang, Kaili; Fan, Shoushan

2014-01-06

The output power of the light from GaN-based light-emitting diodes (LEDs) was enhanced by fabricating gold (Au) nanoparticles on the surface of p-GaN. Quasi-aligned Au nanoparticle arrays were prepared by depositing Au thin film on an aligned suspended carbon nanotube thin film surface and then putting the Au-CNT system on the surface of p-GaN and thermally annealing the sample. The size and position of the Au nanoparticles were confined by the carbon nanotube framework, and no other additional residual Au was distributed on the surface of the p-GaN substrate. The output power of the light from the LEDs with Au nanoparticles was enhanced by 55.3% for an injected current of 100 mA with the electrical property unchanged compared with the conventional planar LEDs. The enhancement may originate from the surface plasmon effect and scattering effect of the Au nanoparticles.

Chromogenic Detection of Dipeptidyl Peptidase IV (DPP-IV) Activity using Peptide-Functionalized Gold Nanoparticles

NASA Astrophysics Data System (ADS)

Abul-Huda, Yasin Mohammad

Metal nanoparticles offer a useful platform for a wide range of biological applications especially for biosensing, bioimaging and drug delivery. This thesis presents a body of original research describing the synthesis, characterisation and development of a novel and convenient biosensing assay for detection of dipeptidyl peptidase IV (DPP-IV) enzyme activity using peptide functionalized gold nanoparticles. The distinctive optical and physical properties of gold nanoparticles (Au NP) were harnessed for the development of a colorimetric assay for rapid sensing of DPP-IV activities and screening DPP-IV inhbitors. The citrate reduction method for Au NPs synthesis was optimised and several potential peptide substrates (GPDC, VP-EN-DC, C/G dipeptide, GPG-EN-PEG4-LA, GPDCALNNC) were designed to provide substrates that mimic the DPP-IV natural substrates. The performances of the substrate functionalized Au NPs were assessed for their appropriateness for the detection of the enzyme activity. Addition of DPP-IV to the solutions containing the functionalized Au NPs resulted in cleavage of the substrate and thus causing the aggregation of the Au NPs which in turn led to a shift of the surface plasmon peak toward longer wavelengths, and a change of the colour of the colloidal suspension from red to blue. Overall, real-time detection of DPP-IV activity over a broader range (0-40 U/L) with high selectivity and stability was obtained, thus providing a method that can be used to determine the levels of DPP-IV/CD26 in biological fluids such as serum and plasma. Further assay developments were conducted to overcome limitations encountered with the original Au NP assay, especially the narrow dynamic linear range and stability in high ionic strength solutions. Validation and comparison of the Au NP assay developed has revealed that this method is highly correlated to the gold standard chromogenic Gly-Pro-pNA method for detection of enzyme activity in biological samples. Very good recoveries (in the range 83.6 -114.9%) were obtained in spiked serum samples, which indicate that this assay could provide a suitable alternative for enzyme activity detection with the naked eye and without the need for sophisticated instruments. Investigations into the effects of incorporating different stabilizers in order to improve the stability of the peptide functionalized Au NP in high ionic strength solutions were also investigated. Gold nanoparticles have different shapes and structures and an alternative approach for detection of DPP-IV activity using gold nanorods due to their higher refractive index sensitivities was explored. As a conclusion, three out of five approaches, all utilising Au NP-ligand conjugates were demonstrated useful for the detection of the DPP-IV activity. The system developed here is portable and would permit on-site analysis of samples, which offers a real alternative approach from traditional assays and reduces the need for laboratory testing. The logical next step in this research would be the continuation of experiments to transform this test into a point of care testing device that could offer an early detection tool for disease management.

Polyaminoacid-Induced Growth of Metal Nanoparticles on Layer-by-Layer Templates

DTIC Science & Technology

2008-08-21

15,17 In another study, Zhou et al. used tyrosine residues of silk fibroin for growth of 45 nm core-shell colloidal gold- silk fibroin biocongugates at...fungus,28 or silk fiber-templated29 reduction of gold and silver nanostructures. However, despite the increas- ing interest in using organic substrates...not show any particles on the surface after the identical exposure (Figure 2c). (44) Senior, M.; Gorrell, S.; Hamori, E. Biopolymers 1971, 10, 2387

Surface-enhanced hyper-Raman spectroscopy with a picosecond laser: gold and copper colloids

NASA Astrophysics Data System (ADS)

Lipscomb, Leigh Ann; Nie, Shuming; Feng, Sibo; Yu, Nai-Teng

1990-07-01

We have obtained surface-enhanced hyper-Raman scattering (SEHRS) spectra of crystal violet, rhodamine 6G and Ru(trpy) (BPE) 32+ adsorbed on gold and copper colloidal surfaces (where trpy=2,2',2″-terpyridine, BPE=trans-bis(4-pyridyl)ethylene). Our results demonstrate that the SEHRS effect is not intrinsically restricted to a Ag substrate and that surface enhancements at the emitted hyper-Raman photon frequencies are not required for observing SEHRS signals.

Studies of SERS efficiency of gold coated porous silicon formed on rough silicon backside

NASA Astrophysics Data System (ADS)

Dridi, H.; Haji, L.; Moadhen, A.

2017-12-01

Starting from a rough backside of silicon wafer, we have formed a porous layer by electrochemical anodization and then coated by a thin film of gold. The morphological characteristics of the porous silicon and in turn the metal film are governed by the anodization process and also by the starting surface. So, in order to investigate the Plasmonic aspect of such rough surface which combines roughness inherent to the porous nature and that due to rough starting surface, we have used a dye target molecule to study its SERS signal using a porous silicon layer obtained on the rough backside surface. The use of unusual backside of silicon wafer could be, beside the others, an interesting way to made SERS effective substrate thanks to reproducible rough porous gold on porous layer from this starting face. The morphological results correspond to the silicon rough surface as a function of the crystallographic orientation showed the presence of two different substrate structure. The optical reflectivity results obtained of gold deposited on oxidized porous silicon showed a dependence of its Localized Surface Plasmon band frequency of the deposit time. SERS results, obtained for a dye target molecule (Rhodamine 6G), show a higher intensities in the case of the 〈110〉 orientation, which characterized by the higher roughness surface. Voici "the most relevant and important aspects of our work".

Ductile film delamination from compliant substrates using hard overlayers

PubMed Central

Cordill, M.J.; Marx, V.M.; Kirchlechner, C.

2014-01-01

Flexible electronic devices call for copper and gold metal films to adhere well to polymer substrates. Measuring the interfacial adhesion of these material systems is often challenging, requiring the formulation of different techniques and models. Presented here is a strategy to induce well defined areas of delamination to measure the adhesion of copper films on polyimide substrates. The technique utilizes a stressed overlayer and tensile straining to cause buckle formation. The described method allows one to examine the effects of thin adhesion layers used to improve the adhesion of flexible systems. PMID:25641995

Ductile film delamination from compliant substrates using hard overlayers.

PubMed

Cordill, M J; Marx, V M; Kirchlechner, C

2014-11-28

Flexible electronic devices call for copper and gold metal films to adhere well to polymer substrates. Measuring the interfacial adhesion of these material systems is often challenging, requiring the formulation of different techniques and models. Presented here is a strategy to induce well defined areas of delamination to measure the adhesion of copper films on polyimide substrates. The technique utilizes a stressed overlayer and tensile straining to cause buckle formation. The described method allows one to examine the effects of thin adhesion layers used to improve the adhesion of flexible systems.

Top-down Approach for the Direct Synthesis, Patterning, and Operation of Artificial Micromuscles on Flexible Substrates.

PubMed

Maziz, Ali; Plesse, Cédric; Soyer, Caroline; Cattan, Eric; Vidal, Frédéric

2016-01-27

Recent progress in the field of microsystems on flexible substrates raises the need for alternatives to the stiffness of classical actuation technologies. This paper reports a top-down process to microfabricate soft conducting polymer actuators on substrates on which they ultimately operate. The bending microactuators were fabricated by sequentially stacking layers using a layer polymerization by layer polymerization of conducting polymer electrodes and a solid polymer electrolyte. Standalone microbeams thinner than 10 μm were fabricated on SU-8 substrates associated with a bottom gold electrical contact. The operation of microactuators was demonstrated in air and at low voltage (±4 V).

Microgap x-ray detector

DOEpatents

Wuest, Craig R.; Bionta, Richard M.; Ables, Elden

1994-01-01

An x-ray detector which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope.

Effects of surface tension and viscosity on gold and silver sputtered onto liquid substrates

NASA Astrophysics Data System (ADS)

De Luna, Mark M.; Gupta, Malancha

2018-05-01

In this paper, we study DC magnetron sputtering of gold and silver onto liquid substrates of varying viscosities and surface tensions. We were able to separate the effects of viscosity from surface tension by depositing the metals onto silicone oils with a range of viscosities. The effects of surface tension were studied by depositing the metals onto squalene, poly(ethylene glycol), and glycerol. It was found that dispersed nanoparticles were formed on liquids with low surface tension and low viscosity whereas dense films were formed on liquids with low surface tension and high viscosity. Nanoparticles were formed on both the liquid surface and within the bulk liquid for high surface tension liquids. Our results can be used to tailor the metal and liquid interaction to fabricate particles and films for various applications in optics, electronics, and catalysis.

Microgap x-ray detector

DOEpatents

Wuest, C.R.; Bionta, R.M.; Ables, E.

1994-05-03

An x-ray detector is disclosed which provides for the conversion of x-ray photons into photoelectrons and subsequent amplification of these photoelectrons through the generation of electron avalanches in a thin gas-filled region subject to a high electric potential. The detector comprises a cathode (photocathode) and an anode separated by the thin, gas-filled region. The cathode may comprise a substrate, such a beryllium, coated with a layer of high atomic number material, such as gold, while the anode can be a single conducting plane of material, such as gold, or a plane of resistive material, such as chromium/silicon monoxide, or multiple areas of conductive or resistive material, mounted on a substrate composed of glass, plastic or ceramic. The charge collected from each electron avalanche by the anode is passed through processing electronics to a point of use, such as an oscilloscope. 3 figures.

Soil biological attributes in arsenic-contaminated gold mining sites after revegetation.

PubMed

Dos Santos, Jessé Valentim; de Melo Rangel, Wesley; Azarias Guimarães, Amanda; Duque Jaramillo, Paula Marcela; Rufini, Márcia; Marra, Leandro Marciano; Varón López, Maryeimy; Pereira da Silva, Michele Aparecida; Fonsêca Sousa Soares, Cláudio Roberto; de Souza Moreira, Fatima Maria

2013-12-01

Recovery of arsenic contaminated areas is a challenge society faces throughout the world. Revegetation associated with microbial activity can play an essential role in this process. This work investigated biological attributes in a gold mining area with different arsenic contents at different sites under two types of extant revegetation associated with cover layers of the soil: BS, Brachiaria sp. and Stizolobium sp., and LEGS, Acacia crassicarpa, A. holosericea, A. mangium, Sesbania virgata, Albizia lebbeck and Pseudosamanea guachapele. References were also evaluated, comprising the following three sites: B1, weathered sulfide substrate without revegetation; BM, barren material after gold extraction and PRNH (private reserve of natural heritage), an uncontaminated forest site near the mining area. The organic and microbial biomass carbon contents and substrate-induced respiration rates for these sites from highest to lowest were: PRNH > LEGS > BS > B1 and BM. These attributes were negatively correlated with soluble and total arsenic concentration in the soil. The sites that have undergone revegetation (LEGS and BS) had higher densities of bacteria, fungi, phosphate solubilizers and ammonium oxidizers than the sites without vegetation. Principal component analysis showed that the LEGS site grouped with PRNH, indicating that the use of leguminous species associated with an uncontaminated soil cover layer contributed to the improvement of the biological attributes. With the exception of acid phosphatase, all the biological attributes were indicators of soil recovery, particularly the following: microbial carbon, substrate-induced respiration, density of culturable bacteria, fungi and actinobacteria, phosphate solubilizers and metabolic quotient.

Tribological characteristics of sputtered Au/Cr films on alumina substrates at elevated temperatures

NASA Technical Reports Server (NTRS)

Benoy, P. A.; Dellacorte, C.

1993-01-01

Research to evaluate the tribological properties of alumina pins sliding against thin sputtered gold films deposited on alumina disk substrates is described. A 250 A thick chromium interlayer was first deposited onto the alumina test disks to enhance adhesion and high temperature wetting of the gold films. The Au/Cr films were tribotested in pure sliding in a pin-on-disk tribometer under a 4.9 N load at 1m/s. The test atmosphere was room air at temperatures of 25, 500, and 800 C and the test duration varied from 60 to 540 min. The use of the Au/Cr films reduced friction by about a factor of two compared to the unlubricated alumina sliding couple. The coatings prevented wear of the alumina substrate disks and reduced pin wear by one to two orders of magnitude. In addition, wear lives in excess of 200,000 sliding passes (9 hr) were observed during sliding at 800 C. The results suggest that these films show promise for the practical lubrication of many high temperature sliding components.

Conical Tungsten Tips as Substrates for the Preparation of Ultramicroelectrodes

PubMed Central

Hermans, Andre; Wightman, R. Mark

2008-01-01

Here we describe a simple method to prepare voltammetric microelectrodes using tungsten wires as a substrate. Tungsten wires have high tensile modulus and enable the fabrication of electrodes that have small dimensions overall while retaining rigidity. In this work, 125 μm tungsten wires with a conical tip were employed. For the preparation of gold or platinum ultramicroelectrodes, commercial tungsten microelectrodes, completely insulated except at the tip, were used as substrates. Following removal of oxides from the exposed tungsten, platinum or gold was electroplated yielding surfaces with an electroactive area of between 1×10−6 cm2 to 2×10−6 cm2. Carbon surfaces on the etched tip of tungsten microwires were prepared by coating with photoresist followed by pyrolysis. The entire electrode was then insulated with Epoxylite except the tip yielding an exposed carbon surface with an area of around 4×10−6 cm2 to 6×10−6 cm2. All three types of ultramicroelectrodes fabricated on the tungsten wire had similar electrochemical behavior to electrodes fabricated from wires or fibers insulated with glass tubes. PMID:17129002

SERS activity of silver and gold nanostructured thin films deposited by pulsed laser ablation

NASA Astrophysics Data System (ADS)

Agarwal, N. R.; Tommasini, M.; Fazio, E.; Neri, F.; Ponterio, R. C.; Trusso, S.; Ossi, P. M.

2014-10-01

Nanostructured Au and Ag thin films were obtained by nanosecond pulsed laser ablation in presence of a controlled Ar atmosphere. Keeping constant other deposition parameters such as target-to-substrate distance, incidence angle, laser wavelength and laser fluence, the film morphology, revealed by SEM, ranges from isolated NPs to island structures and sensibly depends on gas pressure (10-100 Pa) and on the laser pulse number (500-3 × 10). The control of these two parameters allows tailoring the morphology and correspondingly the optical properties of the films. The position and width of the surface plasmon resonance peak, in fact, can be varied with continuity. The films showed remarkable surface-enhanced Raman activity (SERS) that depends on the adopted deposition conditions. Raman maps were acquired on micrometer-sized areas of both silver and gold substrates selected among those with the strongest SERS activity. Organic dyes of interest in cultural heritage studies (alizarin, purpurin) have been also considered for bench marking the substrates produced in this work. Also the ability to detect the presence of biomolecules was tested using lysozyme in a label free configuration.

"Self-Peel-Off" Transfer Produces Ultrathin Polyvinylidene-Fluoride-Based Flexible Nanodevices.

PubMed

Tai, Yanlong; Lubineau, Gilles

2017-04-01

Here, a new strategy, self-peel-off transfer, for the preparation of ultrathin flexible nanodevices made from polyvinylidene-fluoride (PVDF) is reported. In this process, a functional pattern of nanoparticles is transferred via peeling from a temporary substrate to the final PVDF film. This peeling process takes advantage of the differences in the work of adhesion between the various layers (the PVDF layer, the nanoparticle-pattern layer and the substrate layer) and of the high stresses generated by the differential thermal expansion of the layers. The work of adhesion is mainly guided by the basic physical/chemical properties of these layers and is highly sensitive to variations in temperature and moisture in the environment. The peeling technique is tested on a variety of PVDF-based functional films using gold/palladium nanoparticles, carbon nanotubes, graphene oxide, and lithium iron phosphate. Several PVDF-based flexible nanodevices are prepared, including a single-sided wireless flexible humidity sensor in which PVDF is used as the substrate and a double-sided flexible capacitor in which PVDF is used as the ferroelectric layer and the carrier layer. Results show that the nanodevices perform with high repeatability and stability. Self-peel-off transfer is a viable preparation strategy for the design and fabrication of flexible, ultrathin, and light-weight nanodevices.

Intermolecular interactions and substrate effects for an adamantane monolayer on a Au(111) surface

NASA Astrophysics Data System (ADS)

Sakai, Yuki; Nguyen, Giang D.; Capaz, Rodrigo B.; Coh, Sinisa; Pechenezhskiy, Ivan V.; Hong, Xiaoping; Wang, Feng; Crommie, Michael F.; Saito, Susumu; Louie, Steven G.; Cohen, Marvin L.

2013-12-01

We study theoretically and experimentally the infrared (IR) spectrum of an adamantane monolayer on a Au(111) surface. Using a STM-based IR spectroscopy technique (IRSTM) we are able to measure both the nanoscale structure of an adamantane monolayer on Au(111) as well as its infrared spectrum, while DFT-based ab initio calculations allow us to interpret the microscopic vibrational dynamics revealed by our measurements. We find that the IR spectrum of an adamantane monolayer on Au(111) is substantially modified with respect to the gas-phase IR spectrum. The first modification is caused by the adamantane-adamantane interaction due to monolayer packing, and it reduces the IR intensity of the 2912 cm-1 peak (gas phase) by a factor of 3.5. The second modification originates from the adamantane-gold interaction, and it increases the IR intensity of the 2938 cm-1 peak (gas phase) by a factor of 2.6 and reduces its frequency by 276 cm-1. We expect that the techniques described here can be used for an independent estimate of substrate effects and intermolecular interactions in other diamondoid molecules and for other metallic substrates.

Microelectromechanical systems-based visible-near infrared Fabry-Perot tunable filters using quartz substrate

NASA Astrophysics Data System (ADS)

Gupta, Neelam; Tan, Songsheng; Zander, Dennis R.

2012-07-01

There is a need to develop miniature optical tunable filters for small hyperspectral imagers. We plan to develop a number of miniature Fabry-Perot tunable filters (FPTFs) using microelectromechanical systems (MEMS) technology, each operating over a different wavelength region, to cover spectral regions from the visible to the longwave infrared (IR). Use of a MEMS-based FPTF as a dispersive element will reduce the size, weight, and power requirements of hyperspectral imagers and make them less expensive. A key requirement for such a filter is a large optical aperture. Recently, we succeeded in fabricating FPTFs with a 6 mm optical aperture operating in the visible to near IR spectral region (400 to 800 nm) using commercially available thin quartz wafers as the substrate. The FPTF design contains one fixed silver (Ag) mirror and one electrostatically movable Ag mirror, each grown on a quartz substrate with a low total thickness variation. Gold (Au) bumps are used to control the initial air gap distance between the two mirrors, and Au-Au bonding is used to bond the device. We describe material selection, device design, modeling, fabrication, interferometric, and spectral characterizations.

The Electronic Structure and Field Effects of an Organic-Based Room Temperature Magnetic Semiconductor

DTIC Science & Technology

2007-01-01

used. Other materials used in this study include: microscope slide glass for transistor substrates (Gold Seal), silicon nitride, Si3N4, sputtering...with the top in place. At LBNL the glass tubes were placed in a nitrogen filled glove bag attached to the XAS sample chamber where they were...valences such as vanadium(II) oxide (VO), vanadium(III) oxide (V2O3), vanadium(IV) oxide (VO2), and vanadium(IV) oxide ( V2O5 ). V2O3 in particular is an

A crystalline germanium flexible thin-film transistor

NASA Astrophysics Data System (ADS)

Higashi, H.; Nakano, M.; Kudo, K.; Fujita, Y.; Yamada, S.; Kanashima, T.; Tsunoda, I.; Nakashima, H.; Hamaya, K.

2017-11-01

We experimentally demonstrate a flexible thin-film transistor (TFT) with (111)-oriented crystalline germanium (Ge) layers grown by a gold-induced crystallization method. Accumulation-mode metal source/drain p-channel Ge TFTs are fabricated on a polyimide film at ≤ 400 ° C . A field-effect mobility (μFE) of 10.7 cm2/Vs is obtained, meaning the highest μFE in the p-TFTs fabricated at ≤ 400 ° C on flexible plastic substrates. This study will lead to high-performance flexible electronics based on an inorganic-semiconductor channel.

HIV‑1 Integrase Strand Transfer Inhibitors with Reduced Susceptibility to Drug Resistant Mutant Integrases | Center for Cancer Research

Cancer.gov

On the cover: Mutant forms of HIV-1 IN reduce the therapeutic effectiveness of integrase strand transfer inhibitors (INSTIs). The cover figure shows the IN of prototype foamy virus complexed to a novel INSTI (gold) that retains potency against resistant mutants of HIV-1 IN. Overlain are the host and viral DNA substrates (blue and green, respectively), showing substrate mimicry

Characterization of the structure of low-e substrates and consequences for IR transflection measurements

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

DeVetter, Brent M.; Kenkel, Seth; Mittal, Shachi

Spectral distortions caused by the electric field standing wave effect were investigated for two commonly used reflective substrates: low-emissivity glass and gold-coated glass. Our analytical calculations showed that spectral distortions may arise for both incoherent and coherent light sources when performing transflectance measurements. We experimentally confirmed our predictions using a commercial mid-infrared quantum cascade laser microscope and an interferometric infrared imaging system.

Surface-enhanced Raman scattering active gold nanoparticle/nanohole arrays fabricated through electron beam lithography

NASA Astrophysics Data System (ADS)

Wu, Tsunghsueh; Lin, Yang-Wei

2018-03-01

Effective surface-enhanced Raman scattering (SERS)-active substrates from gold nanoparticle and gold nanohole arrays were successfully fabricated through electron beam lithography with precise computer-aided control of the unit size and intergap distance. Their SERS performance was evaluated using 4-mercaptobenzoic acid (4-MBA). These gold arrays yielded strong SERS signals under 785 nm laser excitation. The enhancement factors for 4-MBA molecules on the prepared gold nanoparticle and nanohole arrays maxed at 1.08 × 107 and 8.61 × 106, respectively. The observed increase in SERS enhancement was attributed to the localized surface plasmon resonance (LSPR) wavelength shifting toward the near-infrared regime when the gold nanohole diameter increased, in agreement with the theoretical prediction in this study. The contribution of LSPR to the Raman enhancement from nanohole arrays deposited on fluorine-doped tin oxide glass was elucidated by comparing SERS and transmission spectra. This simple fabrication procedure, which entails employing electron beam lithography and the controllability of the intergap distance, suggests highly promising uses of nanohole arrays as functional components in sensing and photonic devices.

The Complete Reconfiguration of Dendritic Gold

NASA Astrophysics Data System (ADS)

Paneru, Govind; Flanders, Bret

2014-03-01

Reconfigurability-by-design is an important strategy in modern materials science, as materials with this capability could potentially be used to confer hydrophobic, lipophobic, or anti-corrosive character to substrates in a regenerative manner. The present work extends the directed electrochemical nanowire assembly (DENA) methodology, which is a technique that employs alternating voltages to grow single crystalline metallic nanowires and nano-dendrites from simple salt solutions, to enable the complete dissolution of macroscopic arrays of metallic dendrites following their growth. Our main finding is that structural reconfiguration of dendritic gold is induced by changes in the MHz-level frequencies of voltages that are applied to the dendrites. Cyclic voltammetry and micro-Raman spectroscopy have been used to show that dendritic gold grows and dissolves by the same chemical mechanisms as bulk gold. Hence, the redox chemistry that occurs at the crystal-solution interface is no different than the established electrochemistry of gold. What differs in this process and allows for reconfiguration to occur is the diffusive behavior of the gold chloride molecules in the solution adjacent to the interface. We will present a simple model that captures the physics of this behavior.

Surface-enhanced Raman spectroscopy on laser-engineered ruthenium dye-functionalized nanoporous gold

NASA Astrophysics Data System (ADS)

Schade, Lina; Franzka, Steffen; Biener, Monika; Biener, Jürgen; Hartmann, Nils

2016-06-01

Photothermal processing of nanoporous gold with a microfocused continuous-wave laser at λ = 532 nm provides a facile means in order engineer the pore and ligament size of nanoporous gold. In this report we take advantage of this approach in order to investigate the size-dependence of enhancement effects in surface-enhanced Raman spectroscopy (SERS). Surface structures with laterally varying pore sizes from 25 nm to ≥200 nm are characterized using scanning electron microscopy and then functionalized with N719, a commercial ruthenium complex, which is widely used in dye-sensitized solar cells. Raman spectroscopy reveals the characteristic spectral features of N719. Peak intensities strongly depend on the pore size. Highest intensities are observed on the native support, i.e. on nanoporous gold with pore sizes around 25 nm. These results demonstrate the particular perspectives of laser-fabricated nanoporous gold structures in fundamental SERS studies. In particular, it is emphasized that laser-engineered porous gold substrates represent a very well defined platform in order to study size-dependent effects with high reproducibility and precision and resolve conflicting results in previous studies.

Acoustic vibrations of single suspended gold nanostructures

NASA Astrophysics Data System (ADS)

Major, Todd A.

The acoustic vibrations for single gold nanowires and gold plates were studied using time-resolved ultrafast transient absorption. The objective of this work was to remove the contribution of the supporting substrate from the damping of the acoustic vibrations of the metal nano-objects. This was achieved by suspending the nano-objects across trenches created by photolithography and reactive ion etching. Transient absorption measurements for single suspended gold nanowires were initially completed in air and water environments. The acoustic vibrations for gold nanowires over the trench in air last typically for several nanoseconds, whereas gold nanowires in water are damped more quickly. Continuum mechanics models suggest that the acoustic impedance mismatch between air and water dominates the damping rate. Later transient absorption studies on single suspended gold nanowires were completed in glycerol and ethylene glycol environments. However, our continuum mechanical model suggests nearly complete damping in glycerol due to its high viscosity, but similar damping rates are seen between the two liquids. The continuum mechanics model thus incorrectly addresses high viscosity effects on the lifetimes of the acoustic vibrations, and more complicated viscoelastic interactions occur for the higher viscosity liquids. (Abstract shortened by UMI.).

Electrodeposition of gold particles on aluminum substrates containing copper.

PubMed

Olson, Tim S; Atanassov, Plamen; Brevnov, Dmitri A

2005-01-27

Electrodeposition of adhesive metal films on aluminum is traditionally preceded by the zincate process, which activates the aluminum surface. This paper presents an alternative approach for activation of aluminum by using films containing 99.5% aluminum and 0.5% copper. Aluminum/copper films are made amenable for subsequent electrodeposition by anodization followed by chemical etching of aluminum oxide. The electrodeposition of gold is monitored with electrochemical impedance spectroscopy (EIS). Analysis of EIS data suggests that electrodeposition of gold increases the interfacial capacitance from values typical for electrodes with thin oxide layers to values typical for metal electrodes. Scanning electron microscopy examination of aluminum/copper films following gold electrodeposition shows the presence of gold particles with densities of 10(5)-10(7) particles cm(-2). The relative standard deviation of mean particle diameters is approximately 25%. Evaluation of the micrographs suggests that the electrodeposition occurs by instantaneous nucleation followed by growth of three-dimensional semispherical particles. The gold particles, which are electrically connected to the conductive aluminum/copper film, support a reversible faradaic process for a soluble redox couple. The deposited gold particles are suitable for subsequent metallization of aluminum and fabrication of particle-type films with interesting catalytic, electrical, and optical properties.

Diameter-dependent optical constants of gold mesoparticles electrodeposited on aluminum films containing copper.

PubMed

Brevnov, Dmitri A; Bungay, Corey

2005-08-04

Electrodeposition of gold mesoparticles on anodized and chemically etched aluminum/copper films deposited on silicon wafers proceeds by instantaneous nucleation and with no diffusion limitations. Both of these phenomena favor the formation of relatively monodispersed gold particles. Under the reported electrodeposition conditions, the relative standard deviation of the particle diameter is 25%. The particle coverage is 7 x 10(8) particles cm(-2). The mean particle diameter varies as a function of electrodeposition time in the range of 40-80 nm. Optical constants of gold mesoparticles are resolved by spectroscopic ellipsometry. A two-layer optical model is constructed to determine both extinction coefficients and refractive indexes of gold mesoparticles as a function of the mean particle diameter. The absorption peak, associated with surface plasmons, is modeled with two Lorentz oscillators. Absorption peak maximums shift from 610 to 675 nm as the mean particle diameter increases from 42 to 74 nm. Electrodeposition of gold particles on technologically relevant substrates, such as aluminum/copper films, is expected to increase the utility of gold particles and facilitate their incorporation in nanostructured materials and a variety of electronic and optical devices.

Diazonium-derived aryl films on gold nanoparticles: evidence for a carbon-gold covalent bond.

PubMed

Laurentius, Lars; Stoyanov, Stanislav R; Gusarov, Sergey; Kovalenko, Andriy; Du, Rongbing; Lopinski, Gregory P; McDermott, Mark T

2011-05-24

Tailoring the surface chemistry of metallic nanoparticles is generally a key step for their use in a wide range of applications. There are few examples of organic films covalently bound to metal nanoparticles. We demonstrate here that aryl films are formed on gold nanoparticles from the spontaneous reduction of diazonium salts. The structure and the bonding of the film is probed with surface-enhanced Raman scattering (SERS). Extinction spectroscopy and SERS show that a nitrobenzene film forms on gold nanoparticles from the corresponding diazonium salt. Comparison of the SERS spectrum with spectra computed from density functional theory models reveals a band characteristic of a Au-C stretch. The observation of this stretch is direct evidence of a covalent bond. A similar band is observed in high-resolution electron energy loss spectra of nitrobenzene layers on planar gold. The bonding of these types of films through a covalent interaction on gold is consistent with their enhanced stability observed in other studies. These findings provide motivation for the use of diazonium-derived films on gold and other metals in applications where high stability and/or strong adsorbate-substrate coupling are required.

Heparin Assisted Photochemical Synthesis of Gold Nanoparticles and Their Performance as SERS Substrates

PubMed Central

Rodríguez-Torres, Maria del Pilar; Díaz-Torres, Luis Armando; Romero-Servin, Sergio

2014-01-01

Reactive and pharmaceutical-grade heparins were used as biologically compatible reducing and stabilizing agents to photochemically synthesize colloidal gold nanoparticles. Aggregates and anisotropic shapes were obtained photochemically under UV black-light lamp irradiation (λ = 366 nm). Heparin-functionalized gold nanoparticles were characterized by Scanning Electron Microscopy and UV-Vis spectroscopy. The negatively charged colloids were used for the Surface Enhanced Raman Spectroscopy (SERS) analysis of differently charged analytes (dyes). Measurements of pH were taken to inspect how the acidity of the medium affects the colloid-analyte interaction. SERS spectra were taken by mixing the dyes and the colloidal solutions without further functionalization or addition of any aggregating agent. PMID:25342319

Plasmonic Paper as a Novel Chem/Bio Detection Platform

NASA Astrophysics Data System (ADS)

Tian, Limei

The time varying electric field of electromagnetic (EM) radiation causes oscillation of conduction electrons of metal nanoparticles. The resonance of such oscillation, termed localized surface plasmon resonance (LSPR), falls into the visible spectral region for noble metals such as gold, silver and copper. LSPR of metal nanostructures is sensitive to numerous factors such as composition, size, shape, dielectric properties of surrounding medium, and proximity to other nanostructures (plasmon coupling). The sensitivity of LSPR to the refractive index of surrounding medium renders it an attractive platform for chemical and biological sensing. When the excitation light is in resonance with the plasmon frequency of the metal nanoparticle, it radiates a characteristic dipolar radiation causing a characteristic spatial distribution in which certain areas show higher EM field intensity, which is manifested as electromagnetic field enhancement. Surface enhanced Raman scattering (SERS) involves dramatic enhancement of the intensity of the Raman scattering from the analyte adsorbed on or in proximity to a nanostructured metal surface exhibiting such strong EM field enhancement. Both LSPR and SERS have been widely investigated for highly sensitive and label-free chemical & biological sensors. Most of the SERS/LSPR sensors demonstrated so far rely on rigid planar substrates (e.g., glass, silicon) owing to the well-established lithographic approaches, which are routinely employed for either fabrication or assembly of plasmonic nanotransducers. In many cases, their rigid nature results in low conformal contact with the sample and hence poor sample collection efficiency. We hypothesized that paper substrates are an excellent alternative to conventional rigid substrates to significantly improve the (multi-)functionality of LSPR/SERS substrates, dramatically simplify the fabrication procedures and lower the cost. The choice of paper substrates for the implementation of SERS/LSPR sensors is rationalized by numerous advantages such as (i) high specific surface area resulting in large dynamic range (ii) excellent wicking properties for rapid uptake and transport of analytes to test domains (iii) compatibility with conventional printing approaches, enabling multi-analyte plasmonic sensors (iv) significant reduction in cost (v) smaller sample volume requirement (vi) easy disposability. In this work, we have introduced novel SERS and LSPR substrates based on conventional filter paper decorated with plasmonic nanostructures, called plasmonic paper. A flexible SERS substrate based on common filter paper adsorbed with gold nanostructures allows conformal contact with real-world surfaces, enabling rapid trace detection. To realize multifunctional SERS substrates, paper substrates were cut into star-shaped structures and the fingers were differentially functionalized with polyelectrolytes that allows separation and pre-concentration of different components of a complex sample in a small surface area by taking advantage of the properties of cellulose paper and shape-enhanced capillary effect. Plasmonic paper can also serve as a novel LSPR biosensing platform by decorating the paper substrate with biofunctionalized nanostructures. Furthermore, calligraphy approach was employed to create well-isolated test domains on paper substrates using functionalized plasmonic nanostructures as ink for multiplexed chemical sensing and label-free biosensing. These plasmonic paper substrates exhibit excellent sample collection efficiency and do not require complex fabrication processes. This class of substrates is expected to have applications not only to first responders and military personal but also to several areas of medical, food analysis, and environmental research.

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

Fibrinogen Motif Discriminates Platelet and Cell Capture in Peptide-Modified Gold Micropore Arrays.

PubMed

Adamson, Kellie; Spain, Elaine; Prendergast, Una; Moran, Niamh; Forster, Robert J; Keyes, Tia E

2018-01-16

Human blood platelets and SK-N-AS neuroblastoma cancer-cell capture at spontaneously adsorbed monolayers of fibrinogen-binding motifs, GRGDS (generic integrin adhesion), HHLGGAKQAGDV (exclusive to platelet integrin α IIb β 3 ), or octanethiol (adhesion inhibitor) at planar gold and ordered 1.6 μm diameter spherical cap gold cavity arrays were compared. In all cases, arginine/glycine/aspartic acid (RGD) promoted capture, whereas alkanethiol monolayers inhibited adhesion. Conversely only platelets adhered to alanine/glycine/aspartic acid (AGD)-modified surfaces, indicating that the AGD motif is recognized preferentially by the platelet-specific integrin, α IIb β 3 . Microstructuring of the surface effectively eliminated nonspecific platelet/cell adsorption and dramatically enhanced capture compared to RGD/AGD-modified planar surfaces. In all cases, adhesion was reversible. Platelets and cells underwent morphological change on capture, the extent of which depended on the topography of the underlying substrate. This work demonstrates that both the nature of the modified interface and its underlying topography influence the capture of cancer cells and platelets. These insights may be useful in developing cell-based cancer diagnostics as well as in identifying strategies for the disruption of platelet cloaks around circulating tumor cells.

A Hydrophobic Gold Surface Triggers Misfolding and Aggregation of the Amyloidogenic Josephin Domain in Monomeric Form, While Leaving the Oligomers Unaffected

PubMed Central

Apicella, Alessandra; Soncini, Monica; Deriu, Marco Agostino; Natalello, Antonino; Bonanomi, Marcella; Dellasega, David; Tortora, Paolo; Regonesi, Maria Elena; Casari, Carlo Spartaco

2013-01-01

Protein misfolding and aggregation in intracellular and extracellular spaces is regarded as a main marker of the presence of degenerative disorders such as amyloidoses. To elucidate the mechanisms of protein misfolding, the interaction of proteins with inorganic surfaces is of particular relevance, since surfaces displaying different wettability properties may represent model systems of the cell membrane. Here, we unveil the role of surface hydrophobicity/hydrophilicity in the misfolding of the Josephin domain (JD), a globular-shaped domain of ataxin-3, the protein responsible for the spinocerebellar ataxia type 3. By means of a combined experimental and theoretical approach based on atomic force microscopy, Fourier transform infrared spectroscopy and molecular dynamics simulations, we reveal changes in JD morphology and secondary structure elicited by the interaction with the hydrophobic gold substrate, but not by the hydrophilic mica. Our results demonstrate that the interaction with the gold surface triggers misfolding of the JD when it is in native-like configuration, while no structural modification is observed after the protein has undergone oligomerization. This raises the possibility that biological membranes would be unable to affect amyloid oligomeric structures and toxicity. PMID:23527026

Theoretical Study of Monolayer and Double-Layer Waveguide Love Wave Sensors for Achieving High Sensitivity.

PubMed

Li, Shuangming; Wan, Ying; Fan, Chunhai; Su, Yan

2017-03-22

Love wave sensors have been widely used for sensing applications. In this work, we introduce the theoretical analysis of the monolayer and double-layer waveguide Love wave sensors. The velocity, particle displacement and energy distribution of Love waves were analyzed. Using the variations of the energy repartition, the sensitivity coefficients of Love wave sensors were calculated. To achieve a higher sensitivity coefficient, a thin gold layer was added as the second waveguide on top of the silicon dioxide (SiO₂) waveguide-based, 36 degree-rotated, Y-cut, X-propagating lithium tantalate (36° YX LiTaO₃) Love wave sensor. The Love wave velocity was significantly reduced by the added gold layer, and the flow of wave energy into the waveguide layer from the substrate was enhanced. By using the double-layer structure, almost a 72-fold enhancement in the sensitivity coefficient was achieved compared to the monolayer structure. Additionally, the thickness of the SiO₂ layer was also reduced with the application of the gold layer, resulting in easier device fabrication. This study allows for the possibility of designing and realizing robust Love wave sensors with high sensitivity and a low limit of detection.

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.

Plasmonic photothermal accumulation of particles by a microfiber decorated with gold nanostructures

NASA Astrophysics Data System (ADS)

Li, Ying; Hu, Yanjun; Wu, Xingda

2017-08-01

This paper introduces an efficient method for accumulation of particles via thermophoresis and thermal convection sustained by localized surface plasmon energy. Gold nanorods were deposited on the designated surface of a microfiber, when a 808 nm laser at an optical power of 12 mV launched into the microfiber, particles dispersed in the water were massively trapped and aggregated on the substrate. This work is envisioned to have application in photothermal cancer therapy, photothermal imaging, and targeted drug delivery.

Performance of a four-element Ka-band high-temperature superconducting microstrip antenna

NASA Technical Reports Server (NTRS)

Richard, M. A.; Bhasin, K. B.; Gilbert, C.; Metzler, S.; Koepf, G.; Claspy, P. C.

1992-01-01

Superconducting four-element microstrip array antennas operating at 30 GHz have been designed and fabricated on a lanthanum aluminate (LaAlO3) substrates. The experimental performance of these thin film Y-Ba-Cu-O superconducting antennas is compared with that of identical antenna patterned with evaporated gold. Efficiency measurements of these antennas show an improvement of 2 dB at 70 K and as much as 3.5 dB at 40 K in the superconducting antenna over the gold antenna.

Functional and Selective Bacterial Interfaces Using Cross-Scaffold Gold Binding Peptides

NASA Astrophysics Data System (ADS)

Adams, Bryn L.; Hurley, Margaret M.; Jahnke, Justin P.; Stratis-Cullum, Dimitra N.

2015-11-01

We investigated the functional and selective activity of three phage-derived gold-binding peptides on the Escherichia coli ( E. coli) bacterial cell surface display scaffold (eCPX) for the first time. Gold-binding peptides, p3-Au12 (LKAHLPPSRLPS), p8#9 (VSGSSPDS), and Midas-2 (TGTSVLIATPYV), were compared side-by-side through experiment and simulation. All exhibited strong binding to an evaporated gold film, with approximately a 4-log difference in binding between each peptide and the control sample. The increased affinity for gold was also confirmed by direct visualization of samples using Scanning Electron Microscopy (SEM). Peptide dynamics in solution were performed to analyze innate structure, and all three were found to have a high degree of flexibility. Preferential binding to gold over silicon for all three peptides was demonstrated, with up to four orders of magnitude selectivity exhibited by p3-Au12. The selectivity was also clearly evident through SEM analysis of the boundary between the gold film and silicon substrate. Functional activity of bound E. coli cells was further demonstrated by stimulating filamentation and all three peptides were characterized as prolific relative to control samples. This work shows great promise towards functional and active bacterial-hybrid gold surfaces and the potential to enable the next generation living material interfaces.

Tuning the EDTA-induced self-assembly and plasmonic spectral properties of gold nanorods: application in surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Li, Jian-jun; Zhang, Ning; Wang, Jingyuan; Yang, Chun-yu; Zhu, Jian; Zhao, Jun-wu

2016-02-01

Self-assembly of cetyl trimethyl ammonium bromide-protected colloidal gold nanorods with different aspect ratios has been studied by adding the ethylene diamine tetraacetic acid (EDTA). Both the assembly strength and assembly configuration fashion of the gold nanorods could be tuned by changing the aspect ratio. For gold nanorods with small aspect ratio, side-by-side assembly takes the major role in the aggregation. In this case, the blue shift of the longitudinal absorption and the increase of the transverse absorption lead to the great uplift of the middle spectrum dip as the EDTA is increased. For gold nanorods with large aspect ratio, end-to-end assembly takes the major role in the aggregation. In this case, the longitudinal absorption peak fades down rapidly and a tailing absorption peak at longer wavelength uplifts greatly as the EDTA is increased. The surface-enhanced Raman scattering (SERS) activity of the assembled gold nanorods has been studied using alpha-fetoprotein (AFP) as the Raman active probe. It has been found that both the side-by-side assembly and end-to-end assembly of the gold nanorods could effectively improve the Raman signal of the AFP. And the gold nanorod substrate with side-by-side assembly has higher SERS activity.

Substrate influence on the interlayer electron-phonon couplings in fullerene films probed with doubly-resonant SFG spectroscopy.

PubMed

Elsenbeck, Dennis; Das, Sushanta K; Velarde, Luis

2017-07-19

We present doubly-resonant sum frequency generation (DR-SFG) spectra of fullerene thin films on metallic and dielectric substrates as a way to investigate the interplay between nuclear and electronic coupling at buried interfaces. Modal and substrate selectivity in the electronic enhancement of the C 60 vibrational signatures is demonstrated for excitation wavelengths spanning the visible range. While the SFG response of the totally symmetric A g (2) mode of fullerene is distinctly coupled to the optically allowed electronic transition corresponding to the HOMO-LUMO+1 of C 60 (ca. 2.6 eV), the T 1u (4) vibrational mode appears to be coupled to a symmetry-forbidden HOMO-LUMO transition at lower energies (ca. 2.0 eV). For dielectric substrates, the DR-SFG intensity of the T 1u (4) mode shows lack of enhancement for upconversion wavelengths off-resonance with the optically-dark LUMO. However, the T 1u (4) mode shows a unique coupling to an intermediate state (∼2.4 eV) only for the fullerene films on the gold substrate. We attribute this coupling to unique interactions at the buried C 60 /gold interface. These results demonstrate the occurrence of clear electron-phonon couplings at the C 60 /substrate interfaces and shed light on the impact of these couplings on the optical response of electronically excited fullerene. This coupling may influence charge and energy transport in organic electronic devices mediated by vibrational motions. We also demonstrate a potential use of this added selectivity in chemical imaging.

Label free detection of lead using impedimetric sensor based on ordered mesoporous carbon-gold nanoparticles and DNAzyme catalytic beacons.

PubMed

Zhou, Yaoyu; Tang, Lin; Zeng, Guangming; Zhang, Chen; Xie, Xia; Liu, Yuanyuan; Wang, Jiajia; Tang, Jing; Zhang, Yi; Deng, Yaocheng

2016-01-01

A novel label-free impedimetric sensing system based on DNAzyme and ordered mesoporous carbon-gold nanoparticle (OMC-GNPs) for the determination of Pb(2+) concentration was developed in the present study. Firstly, gold nanoparticles deposited on the modified electrode surface were employed as a platform for the immobilization of thiolated probe DNA, and then hybridized with DNAzyme catalytic beacons. Subsequently, in the presence of Pb(2+), the DNAzyme could be activated to cleave the substrate strand into two DNA fragments, which causes differences in the electrical properties of the film. Randles equivalent circuit was employed to evaluate the electrochemical impedance spectroscopy (EIS) result. The charge transfer resistance (R(CT)) value for the [Fe(CN)6](3-/4-) redox indicator was remarkably decline after hybridization with Pb(2+). The difference in RCT values before and after hybridization with Pb(2+) showed a linear relation with the concentration of the Pb(2+) in a range of 5×10(-10)-5×10(-5) M, with a detection limit of 2×10(-10) M (S/N=3). Furthermore, with the application of Pb(2+) dependent 8-17DNAzyme, the proposed sensing system exhibited high selectivity without using any labeled probes. This biosensor demonstrated a promising potential for Pb(2+) detection in real sample. Copyright © 2015 Elsevier B.V. All rights reserved.

Modeling of various contact theories for the manipulation of different biological micro/nanoparticles based on AFM

NASA Astrophysics Data System (ADS)

Korayem, M. H.; Taheri, M.

2014-01-01

In this article, the modeling of various contact theories to be applied in the biomanipulation of different micro/nanoparticles based on the atomic force microscope has been studied, and the effect of adhesion force in different contact models on indentation depth and contact angle between tip and substrate has been explored for the target biological micro/nanoparticle. The contact models used in this research include the Hertz, JKR, DMT, BCP, COS, PT, and the SUN models. Also, the target particles comprise the biological micro/nanoparticles of DNA, yeast, platelet, and nanobacterium. Previous research works have investigated the contact models for the manipulation of non-biological gold micro/nanoparticles in the air environment. Since in a real biomanipulation situation, the biological micro/nanoparticles are displaced in biological environments; in this article, various contact theories for the biomanipulation of biological micro/nanoparticles in different biological environments have been modeled and compared for the first time. The results of modeling indicate that the use of Hertz contact model in analyzing the biomanipulation of biological nanoparticles is not appropriate, because it does not take the adhesion force into consideration and thus produces a significant error. Also, all the six contact models developed in this article show larger deformations for studied bionanoparticles in comparison to the gold nanoparticles, which can be justified with regards to the mechanical properties of gold.

Gold nanoparticles on the surface of soda-lime glass: morphological, linear and nonlinear optical characterization.

PubMed

Romani, E C; Vitoreti, Douglas; Gouvêa, Paula M P; Caldas, P G; Prioli, R; Paciornik, S; Fokine, Michael; Braga, Arthur M B; Gomes, Anderson S L; Carvalho, Isabel C S

2012-02-27

Materials presenting high optical nonlinearity, such as materials containing metal nanoparticles (NPs), can be used in various applications in photonics. This motivated the research presented in this paper, where morphological, linear and nonlinear optical characteristics of gold NPs on the surface of bulk soda-lime glass substrates were investigated as a function of nanoparticle height. The NPs were obtained by annealing gold (Au) thin films previously deposited on the substrates. Pixel intensity histogram fitting on Atomic Force Microscopy (AFM) images was performed to obtain the thickness of the deposited film. Image analysis was employed to obtain the statistical distribution of the average height of the NPs. In addition, absorbance spectra of the samples before and after annealing were measured. Finally, the nonlinear refractive index (n2) and the nonlinear absorption index (α2) at 800 nm were obtained before and after annealing by using the thermally managed eclipse Z-scan (TM-EZ) technique with a Ti:Sapphire laser (150 fs pulses). Results show that both n2 and α2 at this wavelength change signs after the annealing and that the samples presented a high nonlinear refractive index.

Use of UO 2 films for electrochemical studies

NASA Astrophysics Data System (ADS)

Miserque, F.; Gouder, T.; Wegen, D. H.; Bottomley, P. D. W.

2001-10-01

UO 2 films have been prepared by dc reactive sputtering of a uranium metal target in an Ar/O 2 atmosphere. We have used the films deposited on gold substrates as working electrodes for electrochemical investigations as simulating the surfaces of fuel pellets. Film composition was determined by photoelectron spectroscopy (XPS and UPS) and X-ray diffraction (XRD). The oxide stoichiometry as a function of deposition conditions was determined and the appropriate conditions for UO 2.0 formation established. AC impedance and cyclic voltammetry measurements were performed. A double RC electrical equivalent circuit was used to fit the data from impedance measurements, similar to those used in unirradiated UO 2 or spent fuel pellets. However due to the porosity or adhesion defects on the thin films that permitted a direct contact between the solution and the gold substrate, we were obliged to add a contribution simulating the water-gold system. Cyclic voltammetry measurements show the influence of pH on the dissolution mechanism. Alkaline solutions permit the formation of an oxidised layer (UO 2.33) which is not present in the acidic solutions. In both pH=2 and pH=6 solutions, a U VI species layer is formed.

Sensitive SERS detection at the single-particle level based on nanometer-separated mushroom-shaped plasmonic dimers

NASA Astrophysics Data System (ADS)

Xiang, Quan; Li, Zhiqin; Zheng, Mengjie; Liu, Qing; Chen, Yiqin; Yang, Lan; Jiang, Tian; Duan, Huigao

2018-03-01

Elevated metallic nanostructures with nanogaps (<10 nm) possess advantages for surface enhanced Raman scattering (SERS) via the synergic effects of nanogaps and efficient decoupling from the substrate through an elevated three-dimensional (3D) design. In this work, we demonstrate a pattern-transfer-free process to reliably define elevated nanometer-separated mushroom-shaped dimers directly from 3D resist patterns based on the gap-narrowing effect during the metallic film deposition. By controlling the initial size of nanogaps in resist structures and the following deposited film thickness, metallic nanogaps could be tuned at the sub-10 nm scale with single-digit nanometer precision. Both experimental and simulated results revealed that gold dimer on mushroom-shaped pillars have the capability to achieve higher SERS enhancement factor comparing to those plasmonic dimers on cylindrical pillars or on a common SiO2/Si substrate, implying that the nanometer-gapped elevated dimer is an ideal platform to achieve the highest possible field enhancement for various plasmonic applications.

Fructose and Pectin Detection in Fruit-Based Food Products by Surface-Enhanced Raman Spectroscopy

PubMed Central

Camerlingo, Carlo; Portaccio, Marianna; Tatè, Rosarita; Lepore, Maria; Delfino, Ines

2017-01-01

Surface-Enhanced Raman Spectroscopy (SERS) enables the investigation of samples with weak specific Raman signals, such as opaque samples, including fruit juices and pulp. In this paper, biological apple juices and apple/pear pulp have been studied in order to evidence the presence of fructose and pectin, which are components of great relevance for quality assessment of these kinds of products. In order to perform SERS measurements a low-cost home-made substrate consisting of a glass slide decorated with 30-nm-sized gold nanoparticles has been designed and used. By employing a conventional micro-Raman spectroscopy set-up and a suitable data treatment based on “wavelet” denoising algorithms and background subtraction, spectra of pectin and fructose with clear Raman features have been obtained. The results have confirmed the potential of SERS in the food industry for product characterization, also considering the low-cost and the relative ease of the fabrication process of the employed SERS substrate. PMID:28398254

Influence of amine and thiol modifications at the 3' ends of single stranded DNA molecules on their adsorption on gold surface and the efficiency of their hybridization.

PubMed

Jaworska, Aleksandra; Jablonska, Anna; Wilanowski, Tomasz; Palys, Barbara; Sek, Slawomir; Kudelski, Andrzej

2018-05-24

Adsorption of molecules of DNA (deoxyribonucleic acid) or modified DNA on gold surfaces is often the first step in construction of many various biosensors, including biosensors for detection of DNA with a particular sequence. In this work we study the influence of amine and thiol modifications at the 3' ends of single stranded DNA (ssDNA) molecules on their adsorption on the surface of gold substrates and on the efficiency of hybridization of immobilized DNA with the complementary single stranded DNA. The characterization of formed layers has been carried out using infrared spectroscopy and atomic force microscopy. As model single stranded DNA we used DNA containing 20 adenine bases, whereas the complementary DNA contained 20 thymine bases. We found that the bands in polarization modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS) spectra of layers formed from thiol-modified DNA are significantly narrower and sharper, indicating their higher regularity in the orientation of DNA on gold surface when using thiol linker. Also, hybridization of the layer of thiol-modified DNA containing 20 adenine bases with the respective DNA containing thymine bases leads to formation of much more organized structures than in the case of unmodified DNA or DNA with the amine linker. We conclude that the thiol-modified ssDNA is more promising for the preparation of biosensors, in comparison with the amine-modified or unmodified ssDNA. We have also found that the above-mentioned modifications at the 3' end of ssDNA significantly influence the IR spectrum (and hence the structure) of polycrystalline films formed from such compounds, even though adsorbed fragments contain less than 5% of the DNA chain. This effect should be taken into account when comparing IR spectra of various polycrystalline films formed from modified and unmodified DNA. Copyright © 2018. Published by Elsevier B.V.

Understanding and Shaping the Morphology of the Barrier Layer of Supported Porous Anodized Alumina on Gold Underlayers.

PubMed

Berger, Nele; Es-Souni, Mohammed

2016-07-12

Large-area ordered nanorod (NR) arrays of various functional materials can be easily and cost-effectively processed using on-substrate anodized porous aluminum oxide (PAO) films as templates. However, reproducibility in the processing of PAO films is still an issue because they are prone to delamination, and control of fabrication parameters such as electrolyte type and concentration and anodizing time is critical for making robust templates and subsequently mechanically reliable NR arrays. In the present work, we systematically investigate the effects of the fabrication parameters on pore base morphology, devise a method to avoid delamination, and control void formation under the barrier layer of PAO films on gold underlayers. Via systematic control of the anodization parameters, particularly the anodization current density and time, we follow the different stages of void development and discuss their formation mechanisms. The practical aspect of this work demonstrates how void size can be controlled and how void formation can be utilized to control the shape of NR bases for improving the mechanical stability of the NRs.

Electrochemical DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles and graphene for sensitive determination of Klebsiella pneumoniae carbapenemase.

PubMed

Pan, Hong-zhi; Yu, Hong-wei; Wang, Na; Zhang, Ze; Wan, Guang-cai; Liu, Hao; Guan, Xue; Chang, Dong

2015-11-20

We describe the fabrication of a sensitive electrochemical DNA biosensor for determination of Klebsiella pneumoniae carbapenemase (KPC). The highly sensitive and selective electrochemical biosensor for DNA detection was constructed based on a glassy carbon electrode (GCE) modified with gold nanoparticles (Au-NPs) and graphene (Gr). Then Au-NPs/Gr/GCE was characterized by scanning electro microscope (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The hybridization detection was measured by diffierential pulse voltammetry (DPV) using methylene blue (MB) as the hybridization indicator. The dynamic range of detection of the sensor for the target DNA sequences was from 1 × 10(-12) to 1 × 10(-7)mol/L, with a detection limit of 2 × 10(-13)mol/L. The DNA biosensor had excellent specificity for distinguishing complementary DNA sequence in the presence of non-complementary and mismatched DNA sequence. The results demonstrated that the Au-NPs/Gr nanocomposite was a promising substrate for the development of high-performance electrocatalysts for determination of KPC. Copyright © 2015 Elsevier B.V. All rights reserved.

Ultrathin free-standing close-packed gold nanoparticle films: Conductivity and Raman scattering enhancement

NASA Astrophysics Data System (ADS)

Yu, Qing; Huang, Hongwen; Peng, Xinsheng; Ye, Zhizhen

2011-09-01

A simple filtration technique was developed to prepare large scale free-standing close-packed gold nanoparticle ultrathin films using metal hydroxide nanostrands as both barrier layer and sacrificial layer. As thin as 70 nm, centimeter scale robust free-standing gold nanoparticle thin film was obtained. The thickness of the films could be easily tuned by the filtration volumes. The electronic conductivities of these films varied with the size of the gold nanoparticles, post-treatment temperature, and thickness, respectively. The conductivity of the film prepared from 20 nm gold nanoparticles is higher than that of the film prepared from 40 nm gold nanoparticle by filtering the same filtration volume of their solution, respectively. Their conductivities are comparable to that of the 220 nm thick ITO film. Furthermore, these films demonstrated an average surface Raman scattering enhancement up to 6.59 × 105 for Rhodamine 6 G molecules on the film prepared from 40 nm gold nanoparticles. Due to a lot of nano interspaces generated from the close-packed structures, two abnormal enhancements and relative stronger intensities of the asymmetrical vibrations at 1534 and 1594 cm-1 of R6G were observed, respectively. These robust free-standing gold nanoparticle films could be easily transferred onto various solid substrates and hold the potential application for electrodes and surface enhanced Raman detectors. This method is applicable for preparation of other nanoparticle free-standing thin films.A simple filtration technique was developed to prepare large scale free-standing close-packed gold nanoparticle ultrathin films using metal hydroxide nanostrands as both barrier layer and sacrificial layer. As thin as 70 nm, centimeter scale robust free-standing gold nanoparticle thin film was obtained. The thickness of the films could be easily tuned by the filtration volumes. The electronic conductivities of these films varied with the size of the gold nanoparticles, post-treatment temperature, and thickness, respectively. The conductivity of the film prepared from 20 nm gold nanoparticles is higher than that of the film prepared from 40 nm gold nanoparticle by filtering the same filtration volume of their solution, respectively. Their conductivities are comparable to that of the 220 nm thick ITO film. Furthermore, these films demonstrated an average surface Raman scattering enhancement up to 6.59 × 105 for Rhodamine 6 G molecules on the film prepared from 40 nm gold nanoparticles. Due to a lot of nano interspaces generated from the close-packed structures, two abnormal enhancements and relative stronger intensities of the asymmetrical vibrations at 1534 and 1594 cm-1 of R6G were observed, respectively. These robust free-standing gold nanoparticle films could be easily transferred onto various solid substrates and hold the potential application for electrodes and surface enhanced Raman detectors. This method is applicable for preparation of other nanoparticle free-standing thin films. Electronic supplementary information (ESI) available: Figure S1, the SEM images and photograph of the films prepared from 10 ml, 20 nm gold nanoparticles. Scheme S1, the vibrations of 1534 and 1594 cm-1 of R6G. See DOI: 10.1039/c1nr10578g

High resolution SEM imaging of gold nanoparticles in cells and tissues.

PubMed

Goldstein, A; Soroka, Y; Frušić-Zlotkin, M; Popov, I; Kohen, R

2014-12-01

The growing demand of gold nanoparticles in medical applications increases the need for simple and efficient characterization methods of the interaction between the nanoparticles and biological systems. Due to its nanometre resolution, modern scanning electron microscopy (SEM) offers straightforward visualization of metallic nanoparticles down to a few nanometre size, almost without any special preparation step. However, visualization of biological materials in SEM requires complicated preparation procedure, which is typically finished by metal coating needed to decrease charging artefacts and quick radiation damage of biomaterials in the course of SEM imaging. The finest conductive metal coating available is usually composed of a few nanometre size clusters, which are almost identical to the metal nanoparticles employed in medical applications. Therefore, SEM monitoring of metal nanoparticles within cells and tissues is incompatible with the conventional preparation methods. In this work, we show that charging artefacts related to non-conductive biological specimen can be successfully eliminated by placing the uncoated biological sample on a conductive substrate. By growing the cells on glass pre-coated with a chromium layer, we were able to observe the uptake of 10 nm gold nanoparticles inside uncoated and unstained macrophages and keratinocytes cells. Imaging in back scattered electrons allowed observation of gold nanoparticles located inside the cells, while imaging in secondary electron gave information on gold nanoparticles located on the surface of the cells. By mounting a skin cross-section on an improved conductive holder, consisting of a silicon substrate coated with copper, we were able to observe penetration of gold nanoparticles of only 5 nm size through the skin barrier in an uncoated skin tissue. The described method offers a convenient modification in preparation procedure for biological samples to be analyzed in SEM. The method provides high conductivity without application of surface coating and requires less time and a reduced use of toxic chemicals. © 2014 The Authors Journal of Microscopy © 2014 Royal Microscopical Society.

Electron transfer of plurimodified DNA SAMs.

PubMed

Rospigliosi, Alessandro; Ehlich, Rudolf; Hoerber, Heinrich; Middelberg, Anton; Moggridge, Geoff

2007-07-17

An STM-based current-voltage (I/V) investigation of deoxyribonucleic acid (DNA) 18 base pair (bp) oligonucleotide monolayers on gold is presented. Three bases of each of the immobilized and complementary strands were modified with either iodine or phenylethylene moieties. The oligonucleotides were immobilized on template stripped gold (tsg) surfaces and characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). AFM imaging showed that monolayers of the expected height were formed. A comparative study of normal, halogenated, and phenyl-modified DNA was made with the STM in tunneling spectroscopy (TS) mode. I/V spectroscopic measurements in the range +/-250 mV on both single- and double-stranded (ds) DNA monolayers (modified and unmodified) showed that for negative substrate bias (U(sub)) electron transfer is more efficient through a phenyl-modified monolayer than through normal or halogenated DNA. This effect was particularly clear below a threshold bias of -100 mV. For positive U(sub), unmodified ds DNA was found to conduct slightly better than the modified strands. This is presumably caused by greater order in the unmodified versus modified DNA monolayers. Modifications on the immobilized (thiolated) strand seem to improve electron transport through the DNA monolayer more than modifications on the complementary (not surface-bound) strand.

A sensitive gold nanoparticles sensing platform based on resonance energy transfer for chemiluminescence light on detection of biomolecules.

PubMed

Qin, Guoxing; Zhao, Shulin; Huang, Yong; Jiang, Jing; Liu, Yi-Ming

2013-08-15

In this article, we report a gold nanoparticles (AuNPs) sensing platform based on chemiluminescence resonance energy transfer (CRET) for light on detection of biomolecules. In designing such a CRET-based biosensing platform, the aptamer was first covalently labeled with a chemiluminescent reagent, N-(4-aminobutyl)-N-ethylisoluminol (ABEI). The ABEI labeled aptamer was then hybridized with AuNPs functionalized ssDNA which was complementary to the aptamer, obtaining the aptasensor. The CRET between ABEI and AuNPs in the aptasensor led to the CL quenching of ABEI. In the presence of a target analyte, it formed a complex with aptamer, and released ABEI-aptamer from AuNPs surface that resulted in CL recovery of ABEI. To test this design, a thrombin (used as a model analyte) aptasensor was prepared and evaluated. The results indicate that the proposed approach is simple and provided a linear range of 50-550 pM for thrombin detection with a detection limit of 15 pM. This new methodology can be easily extended to assay other biomolecules by simply changing the recognition sequence with the substrate aptamer. Copyright © 2013 Elsevier B.V. All rights reserved.

Paper-based immunosensor with signal amplification by enzyme-labeled anti-p16INK4a multifunctionalized gold nanoparticles for cervical cancer screening.

PubMed

Yokchom, Ruchuon; Laiwejpithaya, Somsak; Maneeprakorn, Weerakanya; Tapaneeyakorn, Satita; Rabablert, Jundee; Dharakul, Tararaj

2018-04-01

The aim of this study was to develop a paper-based immunosensor for cervical cancer screening, with signal amplification by multifunctionalized gold nanoparticles (AuNPs). The AuNPs were functionalized with a highly specific antibody to the p16 INK4a cancer biomarker. The signal was amplified using a combination of the peroxidase activity of horseradish peroxidase (HRP) enzyme-antibody conjugate and the peroxidase-like activity of the AuNPs. The immune complex of p16 INK4a protein and multifunctionalized AuNPs was deposited on the nitrocellulose membrane, and a positive result was generated by catalytic oxidation of peroxidase enzyme substrate 3,3',5,5'-Tetramethylbenzidine (TMB). The entire reaction occurred on the membrane within 30 min. Evaluation in clinical samples revealed 85.2% accuracy with a kappa coefficient of 0.69. This proof of concept study demonstrates the successful development of a highly accurate, paper-based immunosensor that is easy to interpret using the naked eye and that is suitable for cervical cancer screening in low-resource settings. Copyright © 2018 Elsevier Inc. All rights reserved.

Thin-film semiconductor rectifier has improved properties

NASA Technical Reports Server (NTRS)

1966-01-01

Cadmium selenide-zinc selenide film is used as a thin film semiconductor rectifier. The film is vapor-deposited in a controlled concentration gradient into a glass substrate to form the required junctions between vapor-deposited gold electrodes.

Microfluidic transmission surface plasmon resonance enhancement for biosensor applications

NASA Astrophysics Data System (ADS)

Lertvachirapaiboon, Chutiparn; Baba, Akira; Ekgasit, Sanong; Shinbo, Kazunari; Kato, Keizo; Kaneko, Futao

2017-01-01

The microfluidic transmission surface plasmon resonance (MTSPR) constructed by assembling a gold-coated grating substrate with a microchannel was employed for biosensor application. The transmission surface plasmon resonance spectrum obtained from the MTSPR sensor chip showed a strong and narrow surface plasmon resonance (SPR) peak located between 650 and 800 nm. The maximum SPR excitation was observed at an incident angle of 35°. The MTSPR sensor chip was employed for glucose sensor application. Gold-coated grating substrates were functionalized using 3-mercapto-1-propanesulfonic acid sodium salt and subsequently functionalized using a five-bilayer poly(allylamine hydrochloride)/poly(sodium 4-styrenesulfonate) to facilitate the coupling/decoupling of the surface plasmon and to prepare a uniform surface for sensing. The detection limit of our developed system for glucose was 2.31 mM. This practical platform represents a high possibility of further developing several biomolecules, multiplex systems, and a point-of-care assay for practical biosensor applications.

Monoatomic and cluster beam effect on ToF-SIMS spectra of self-assembled monolayers on gold

NASA Astrophysics Data System (ADS)

Tuccitto, N.; Torrisi, V.; Delfanti, I.; Licciardello, A.

2008-12-01

Self-assembled monolayers represent well-defined systems that is a good model surface to study the effect of primary ion beams used in secondary ion mass spectrometry. The effect of polyatomic primary beams on both aliphatic and aromatic self-assembled monolayers has been studied. In particular, we analysed the variation of the relative secondary ion yield of both substrate metal-cluster (Au n-) in comparison with the molecular ions (M -) and clusters (M xAu y-) by using Bi +, Bi 3+, Bi 5+ beams. Moreover, the differences in the secondary ion generation efficiency are discussed. The main effect of the cluster beams is related to an increased formation of low-mass fragments and to the enhancement of the substrate related gold-clusters. The results show that, at variance of many other cases, the static SIMS of self-assembled monolayers does not benefit of the use of polyatomic primary ions.

Reversible gating of smart plasmonic molecular traps using thermoresponsive polymers for single-molecule detection

PubMed Central

Zheng, Yuanhui; Soeriyadi, Alexander H.; Rosa, Lorenzo; Ng, Soon Hock; Bach, Udo; Justin Gooding, J.

2015-01-01

Single-molecule surface-enhanced Raman spectroscopy (SERS) has attracted increasing interest for chemical and biochemical sensing. Many conventional substrates have a broad distribution of SERS enhancements, which compromise reproducibility and result in slow response times for single-molecule detection. Here we report a smart plasmonic sensor that can reversibly trap a single molecule at hotspots for rapid single-molecule detection. The sensor was fabricated through electrostatic self-assembly of gold nanoparticles onto a gold/silica-coated silicon substrate, producing a high yield of uniformly distributed hotspots on the surface. The hotspots were isolated with a monolayer of a thermoresponsive polymer (poly(N-isopropylacrylamide)), which act as gates for molecular trapping at the hotspots. The sensor shows not only a good SERS reproducibility but also a capability to repetitively trap and release molecules for single-molecular sensing. The single-molecule sensitivity is experimentally verified using SERS spectral blinking and bianalyte methods. PMID:26549539

Temperature dependent localized surface plasmon resonance properties of supported gold nanoparticles

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

Laha, Ranjit; Ranjan, Pranay

2016-05-23

The well known localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) supported on a dielectric substrate depends on the particle shape, size and type of dielectric material. The particle size and shape mainly vary with the method of preparation and the parameters involved there in. In this report, we show preparation of AuNPs supported on quartz substrate by direct current sputtering followed by thermal annealing at an optimized temperature of 400 °C. The samples were characterized using optical absorption spectra, scanning electron microscopy (SEM) and the energy dispersive x-ray spectrum. The LSPR position could be tuned by varying annealingmore » temperature. The LSPR was found to be blue shifted up to 10 nm with annealing temperature varying from 400 °C to 800 °C. The change in LSPR was ascribed to the morphology of AuNPs over quartz.« less

Temperature dependent localized surface plasmon resonance properties of supported gold nanoparticles

NASA Astrophysics Data System (ADS)

Laha, Ranjit; Ranjan, Pranay

2016-05-01

The well known localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) supported on a dielectric substrate depends on the particle shape, size and type of dielectric material. The particle size and shape mainly vary with the method of preparation and the parameters involved there in. In this report, we show preparation of AuNPs supported on quartz substrate by direct current sputtering followed by thermal annealing at an optimized temperature of 400 °C. The samples were characterized using optical absorption spectra, scanning electron microscopy (SEM) and the energy dispersive x-ray spectrum. The LSPR position could be tuned by varying annealing temperature. The LSPR was found to be blue shifted up to 10 nm with annealing temperature varying from 400 °C to 800 °C. The change in LSPR was ascribed to the morphology of AuNPs over quartz.

Design, synthesis and cytotoxicity of pyrano[4,3-b]indol-1(5H)-ones: A hybrid pharmacophore approach via gold catalyzed cyclization.

PubMed

Praveen, Chandrasekar; Ananth, D Babu

2016-05-15

Reported herein is the gold(III)-catalyzed 6-endo-dig cycloisomerization of 2-alkynyl-indole-3-carboxylic acids to form pyrano[4,3-b]indol-1(5H)-ones, which are pharmaceutically important structural motifs. The hitherto unknown substrates required for this methodology were conveniently synthesized in five steps with good overall yields. The utility of this new cycloisomerization is demonstrated by the excellent regioselectivity obtained using a range of substrates. The mildness of the method allowed functional group compatibility towards hydroxyl tether, displaying exquisite chemoselectivity. All the synthesized compounds were screened for their tumor cell growth inhibitory activity against human cervix adenocarcinoma (HeLa). Compound 7d emerged as the most active (IC50=0.69μM) among the tested series compared to the standard cis-platin (IC50=0.08μM). Copyright © 2016 Elsevier Ltd. All rights reserved.

Antibody immobilization on to polystyrene substrate--on-chip immunoassay for horse IgG based on fluorescence.

PubMed

Darain, Farzana; Gan, Kai Ling; Tjin, Swee Chuan

2009-06-01

A simple microfluidic immunoassay card was developed based on polystyrene (PS) substrate for the detection of horse IgG, an inexpensive model analyte using fluorescence microscope. The primary antibody was captured onto the PS based on covalent bonding via a self-assembled monolayer (SAM) of thiol to pattern the surface chemistry on a gold-coated PS. The immunosensor chip layers were fabricated from sheets by CO(2) laser ablation. The functionalized PS surfaces after each step were characterized by contact angle measurement, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). After the antibody-antigen interaction as a sandwich immunoassay with a fluorescein isothiocyanate (FITC)-conjugated secondary antibody, the intensity of fluorescence was measured on-chip to determine the concentration of the target analyte. The present immunosensor chip showed a linear response range for horse IgG between 1 microg/ml and 80 microg/ml (r = 0.971, n = 3). The detection limit was found to be 0.71 microg/ml. The developed microfluidic system can be extended for various applications including medical diagnostics, microarray detection and observing protein-protein interactions.

Electrodeposition of gold nanoparticles on mesoporous TiO{sub 2} photoelectrode to enhance visible region photocurrent

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

Supriyono,; Krisnandi, Yuni Krisyuningsih; Gunlazuardi, Jarnuzi, E-mail: jarnuzi@ui.ac.id

2016-04-19

Electrodeposition of gold nanoparticles (Au NPs) on the mesoporous TiO{sub 2} photoelectrode to enchance visible region photocurrent have been investigated. Mesoporous TiO{sub 2} was prepared by a sol gel method and immobilized to the fluorine doped tin oxide (FTO) substrate by dip coating technique. Gold nanoparticles were electrodeposited on the TiO{sub 2} surface and the result FTO/TiO{sub 2}/Au was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-Vis diffuse reflectance spectroscopy (DRS), and X-ray diffraction (XRD). The generated photocurrent was evaluated with an electrochemical workstation (e-DAQ/e-recorder 401) using 60 W wolfram lamp as visible lightmore » source. The photoelectrochemical evaluation indicated that the presence of gold nanoparticles on TiO{sub 2} photoelectrode shall enhance the photocurrent up to 50%.« less

Gold Nanohole Array with Sub-1 nm Roughness by Annealing for Sensitivity Enhancement of Extraordinary Optical Transmission Biosensor

NASA Astrophysics Data System (ADS)

Zhang, Jian; Irannejad, Mehrdad; Yavuz, Mustafa; Cui, Bo

2015-05-01

Nanofabrication technology plays an important role in the performance of surface plasmonic devices such as extraordinary optical transmission (EOT) sensor. In this work, a double liftoff process was developed to fabricate a series of nanohole arrays of a hole diameter between 150 and 235 nm and a period of 500 nm in a 100-nm-thick gold film on a silica substrate. To improve the surface quality of the gold film, thermal annealing was conducted, by which an ultra-smooth gold film with root-mean-square (RMS) roughness of sub-1 nm was achieved, accompanied with a hole diameter shrinkage. The surface sensitivity of the nanohole arrays was measured using a monolayer of 16-mercaptohexadecanoic acid (16-MHA) molecule, and the surface sensitivity was increased by 2.5 to 3 times upon annealing the extraordinary optical transmission (EOT) sensor.

Intrinsic stress modulation in diamond like carbon films with incorporation of gold nanoparticles by PLA

NASA Astrophysics Data System (ADS)

Panda, Madhusmita; Krishnan, R.; Krishna, Nanda Gopala; Madapu, Kishore K.; Kamruddin, M.

2018-04-01

Intrinsic stress modulation in the diamond-like carbon (DLC) coatings with incorporation of gold nanoparticles was studied qualitatively from Raman shift. The films were deposited on Si (1 0 0) substrates by using Pulsed laser ablation (PLA) of pure pyrolytic graphite target and with a gold foil on it. Films compositional and chemical behavior was studied by X-ray photoelectron spectroscopy (XPS) and Visible Raman spectroscopy, respectively. The sp3 content obtained from XPS shows dramatic variation in DLC, DLC-Au(100), DLC-Au(200) and DLC-Au(300) as 39%, 41%, 47% and 66% with various gold contentsas 0%, 12%, 7.3% and 4.7%, respectively. The Raman spectra of DLC/Au films showed G-peak shift towards lower wavenumber indicating the reduction of intrinsic stress (internal compressive stress). The sp2, sp3 fraction in the films are also determined from FWHM (G-Peak).

Non-Toxic Gold Nanoclusters for Solution-Processed White Light-Emitting Diodes.

PubMed

Chao, Yu-Chiang; Cheng, Kai-Ping; Lin, Ching-Yi; Chang, Yu-Li; Ko, Yi-Yun; Hou, Tzu-Yin; Huang, Cheng-Yi; Chang, Walter H; Lin, Cheng-An J

2018-06-11

Solution-processed optoelectronic devices are attractive because of the potential low-cost fabrication and the compatibility with flexible substrate. However, the utilization of toxic elements such as lead and cadmium in current optoelectronic devices on the basis of colloidal quantum dots raises environmental concerns. Here we demonstrate that white-light-emitting diodes can be achieved by utilizing non-toxic and environment-friendly gold nanoclusters. Yellow-light-emitting gold nanoclusters were synthesized and capped with trioctylphosphine. These gold nanoclusters were then blended with the blue-light-emitting organic host materials to form the emissive layer. A current efficiency of 0.13 cd/A was achieved. The Commission Internationale de l'Eclairage chromaticity coordinates of (0.27, 0.33) were obtained from our experimental analysis, which is quite close to the ideal pure white emission coordinates (0.33, 0.33). Potential applications include innovative lighting devices and monitor backlight.

In Situ Scanning Tunneling Microscopy Topography Changes of Gold (111) in Aqueous Sulfuric Acid Produced by Electrochemical Surface Oxidation and Reduction and Relaxation Phenomena

NASA Astrophysics Data System (ADS)

Pasquale, M. A.; Nieto, F. J. Rodríguez; Arvia, A. J.

The electrochemical formation and reduction of O-layers on gold (111) films in 1 m sulfuric acid under different potentiodynamic routines are investigated utilizing in situ scanning tunneling microscopy. The surface dynamics is interpreted considering the anodic and cathodic reaction pathways recently proposed complemented with concurrent relaxation phenomena occurring after gold (111) lattice mild disruption (one gold atom deep) and moderate disruption (several atoms deep). The dynamics of both oxidized and reduced gold topographies depends on the potentiodynamic routine utilized to form OH/O surface species. The topography resulting from a mild oxidative disruption is dominated by quasi-2D holes and hillocks of the order of 5 nm, involving about 500-600 gold atoms each, and their coalescence. A cooperative turnover process at the O-layer, in which the anion ad-layer and interfacial water play a key role, determines the oxidized surface topography. The reduction of these O-layers results in gold clusters, their features depending on the applied potential routine. A moderate oxidative disruption produces a surface topography of hillocks and holes several gold atoms high and deep, respectively. The subsequent reduction leads to a spinodal gold pattern. Concurrent coalescence appears to be the result of an Ostwald ripening that involves the surface diffusion of both gold atoms and clusters. These processes produce an increase in surface roughness and an incipient gold faceting. The dynamics of different topographies can be qualitatively explained employing the arguments from colloidal science theory. For 1.1 V ≤ E ≅ Epzc weak electrostatic repulsions favor gold atom/cluster coalescence, whereas for E < Epzc the attenuated electrostatic repulsions among gold surfaces stabilize small clusters over the substrate producing string-like patterns.

Nanoscale patterning of gold-coated optical fibers for improved plasmonic sensing

NASA Astrophysics Data System (ADS)

Antohe, Iulia; Spasic, Dragana; Delport, Filip; Li, Jiaqi; Lammertyn, Jeroen

2017-05-01

Merging surface plasmon resonance (SPR) to fiber optic (FO) technology has brought remarkable achievements in the field by offering attractive advantages over the conventional prism-based SPR platforms, such as simplicity, cost-effectiveness and miniaturization. However, the performance of the existing FO-SPR instruments mainly depends on the device surface condition and in particular on the structural aspect of the thin gold (Au) plasmonic film deposited on the FO substrate. In this work, a simple cost-effective colloidal lithography technique (CLT) was adapted and applied for the first time to the micrometer-sized FO substrate, to design end reflection-type FO-SPR sensors with periodic arrays of Au triangularly-shaped nanostructures on the Au mirror FO tip distal end. The nanopatterned FO-SPR sensor tips were afterwards subjected to refractometric measurements in a sucrose dilution series and subsequently compared with their non-patterned counterparts. It was observed that the spectral dips of the nanopatterned FO-SPR sensor tips were shifted towards longer wavelengths after CLT patterning. Moreover, the sensor sensitivity was improved with up to 25% compared to the conventional non-patterned FO-SPR devices. The obtained results represent important steps in the development of a new generation of FO-SPR sensors with improved performance, which can ultimately be used in various applications, ranging from food analysis and environmental monitoring, to health control and medical diagnosis.

One-pot reaction for the preparation of biofunctionalized self-assembled monolayers on gold surfaces

NASA Astrophysics Data System (ADS)

Raigoza, Annette F.; Fies, Whitney; Lim, Amber; Onyirioha, Kristeen; Webb, Lauren J.

2017-02-01

The Huisgen cycloaddition reaction (;click; chemistry) has been used extensively to functionalize surfaces with macromolecules in a straightforward manner. We have previously developed a procedure using the copper(I)-catalyzed click reaction to tether synthetic α-helical peptides carrying two alkyne groups to a well-ordered azide-terminated alkanethiol self-assembled monolayer (SAM) on a Au(111) surface. While convenient, click-based strategies potentially pose significant problems from reagents, solvents, and reaction temperatures that may irreversibly damage some molecules or substrates. Tuning click chemistry conditions would allow individual optimization of reaction conditions for a wide variety of biomolecules and substrate materials. Here, we explore the utility of simultaneous SAM formation and peptide-attachment chemistry in a one-pot reaction. We demonstrate that a formerly multistep reaction can be successfully carried out concurrently by mixing azide-terminated alkanethiols, CuCl, and a propargylglycine-containing peptide over a bare gold surface in ethanol and reacting at 70 °C. X-ray photoelectron spectroscopy (XPS), surface infrared spectroscopy, surface circular dichroic (CD) spectroscopy, and scanning tunneling microscopy (STM) were used to determine that this one-pot reaction strategy resulted in a high density of surface-bound α-helices without aggregation. This work demonstrates the simplicity and versatility of a SAM-plus-click chemistry strategy for functionalizing Au surfaces with structured biomolecules.

Reconstituting redox active centers of heme-containing proteins with biomineralized gold toward peroxidase mimics with strong intrinsic catalysis and electrocatalysis for H2O2 detection.

PubMed

Zhang, Liyan; Li, Shuai; Dong, Minmin; Jiang, Yao; Li, Ru; Zhang, Shuo; Lv, Xiaoxia; Chen, Lijun; Wang, Hua

2017-01-15

A facile and efficient enzymatic reconstitution methodology has been proposed for high-catalysis peroxidase mimics by remolding the redox active centers of heme-containing proteins with the in-site biomineralized gold using hemoglobin (Hb) as a model. Catalytic hemin (Hem) was extracted from the active centers of Hb for the gold biomineralization and then reconstituted into apoHb to yield the Hem-Au@apoHb nanocomposites showing dramatically improved intrinsic catalysis and electrocatalysis over natural Hb and Hem. The biomineralized gold, on the one hand, would act as "nanowires" to promote the electron transferring of the nanocomposites. On the other hand, it would create a reactivity pathway to pre-organize and accumulate more substrates towards the active sites of the peroxidase mimics. Steady-state kinetics studies indicate that Hem-Au@apoHb could present much higher substrate affinity (lower Michaelis constants) and intrinsic catalysis even than some natural peroxidases. Moreover, the application feasibility of the prepared artificial enzymes was demonstrated by colorimetric assays and direct electrocatalysis for H 2 O 2 sensing, showing a detection limitation low as 0.45μM. Importantly, such a catalysis active-center reconstitution protocol may circumvent the substantial improvement of the intrinsic catalysis and electrocatalysis of diverse heme-containing proteins or enyzmes toward the extensive applications in the chemical, enviromental, and biomedical catalysis fields. Copyright © 2016 Elsevier B.V. All rights reserved.

Fabrication and functionalization of carbon nanotube field effect transistors for bio-sensing applications

NASA Astrophysics Data System (ADS)

Zhou, Jianyun

Single walled carbon nanotube based field effect transistors are fabricated using photolithography and electron beam lithography techniques. First catalyst islands are deposited onto the substrate using standard optical lithographic techniques, and the nanotubes are grown by catalytic chemical vapor deposition from the pre-patterned catalyst islands. After imaging the grown nanotubes, the metal contact electrodes are patterned using lithography, followed by metal deposition using a sputtering technique. Both single nanotube devices and nanotube film devices are fabricated using this method. The single nanotube devices can be semiconducting, ambipolar, or metallic, with the resistance ranging from tens of kilo ohms to a few mega ohms, while the film devices are generally metallic, with only a few kilo ohms of resistance. Semiconducting single nanotube devices are functionalized for sensor applications. An electrodeposition technique was developed to functionalize the nanotube with a few materials, including avidin, chitosan, and metal nanoparticles. Among them, metal nanoparticle deposition is the most successful, and both gold and silver nanoparticles have been successfully deposited onto the sidewalls of the nanotubes from an "in situ" sacrificial electrode. The size and density of the nanoparticles, to some extent, can be tailored by controlling the deposition voltage. The gold nanoparticles are generally spherical, while the silver nanoparticles have branching snowflake shapes. These nanoparticles change the ON-state conductance of the nanotube while maintaining its semiconducting characteristics. The gold nanoparticles on the nanotube sidewalls can serve as anchoring sites for thiol-terminated biomolecules to functionalize the device for biosensing purposes. Results have shown that the thiol-terminated molecules can bind to the Au nanoparticles; however, nonspecific binding to the SiO2 surface is still abundant. Therefore, a self assembled monolayer (SAM) of protein-resistant polyethylene glycol (PEG) is deposited onto the SiO 2 surface to provide protein resistance, which results in selective immobilization of bio-receptors to the gold nanoparticles on the nanotube only. This reduces possible noise signals from the nonspecific substrate binding, and is expected to improve the device sensitivity.

The Self-Assembly of Nanogold for Optical Metamaterials

NASA Astrophysics Data System (ADS)

Nidetz, Robert A.

2011-12-01

Optical metamaterials are an emerging field that enables manipulation of light like never before. Producing optical metamaterials requires sub-wavelength building blocks. The focus here was to develop methods to produce building blocks for metamaterials from nanogold. Electron-beam lithography was used to define an aminosilane patterned chemical template in order to electrostatically self-assemble citrate-capped gold nanoparticles. Equilibrium self-assembly was achieved in 20 minutes by immersing chemical templates into gold nanoparticle solutions. The number of nanoparticles that self-assembled on an aminosilane dot was controlled by manipulating the diameters of the dots and nanoparticles. Adding salt to the nanoparticle solution enabled the nanoparticles to self-assemble in greater numbers on the same sized dot. However, the preparation of the nanoparticle solution containing salt was sensitive to spikes in the salt concentration which led to aggregation of the nanoparticles and non-specific deposition. Gold nanorods were also electrostatically self-assembled. Polyelectrolyte-coated gold nanorods were patterned with limited success. A polyelectrolyte chemical template also patterned gold nanorods, but the gold nanorods preferred to pattern on the edges of the pattern. Ligand-exchanged gold nanorods displayed the best self-assembly, but suffered from slow kinetics. Self-assembled gold nanoparticles were cross-linked with poly(diallyldimethylammonium chloride). The poly(diallyldimethylammonium chloride) allowed additional nanoparticles to pattern on top of the already patterned nanoparticles. Cross-linked nanoparticles were lifted-off of the substrate by sonication in a sodium hydroxide solution. The presence of van der Waals forces and/or amine bonding prevent the nanogold from lifting-off without sonication. A good-solvent evaporation process was used to self-assemble poly(styrene) coated gold nanoparticles into spherical microbead assemblies. The use of larger nanoparticles and larger poly(styrene) ligands resulted in larger and smaller assemblies, respectively. Stirring the solution resulted in a wider size distribution of microbead assemblies due to the stirring's shear forces. Two undeveloped methods to self-assemble nanogold were investigated. One method used block-copolymer thin films as chemical templates to direct the electrostatic self-assembly of nanogold. Another method used gold nanorods that are passivated with different ligands on different faces. The stability of an alkanethiol ligand in different acids and bases was investigated to determine which materials could be used to produce Janus nanorods.

Molecular and supramolecular control of the work function of an inorganic electrode with self-assembled monolayer of umbrella-shaped fullerene derivatives.

PubMed

Lacher, Sebastian; Matsuo, Yutaka; Nakamura, Eiichi

2011-10-26

The surface properties of inorganic substrates can be altered by coating with organic molecules, which may result in the improvement of the properties suitable for electronic or biological applications. This article reports a systematic experimental study on the influence of the molecular and supramolecular properties of umbrella-shaped penta(organo)[60]fullerene derivatives, and on the work function and the water contact angle of indium-tin oxide (ITO) and gold surfaces. We could relate these macroscopic characteristics to single-molecular level properties, such as ionization potential and molecular dipole. The results led us to conclude that the formation of a SAM of a polar compound generates an electronic field through intermolecular interaction of the molecular charges, and this field makes the overall dipole of the SAM much smaller than the one expected from the simple sum of the dipoles of all molecules in the SAM. This effect, which was called depolarization and previously discussed theoretically, is now quantitatively probed by experiments. The important physical properties in surface science such as work function, ionization potential, and water contact angles have been mutually correlated at the level of molecular structures and molecular orientations on the substrate surface. We also found that the SAMs on ITO and gold operate under the same principle except that the "push-back" effect operates specifically for gold. The study also illustrates the ability of the photoelectron yield spectroscopy technique to rapidly measure the work function of a SAM-covered substrate and the ionization potential value of a molecule on the surface.

The synthesis of biocompatible and SERS-active gold nanoparticles using chitosan.

PubMed

Potara, Monica; Maniu, Dana; Astilean, Simion

2009-08-05

In this study we present a clean, nontoxic, environmentally friendly synthesis procedure to generate a large variety of gold nanoparticles (GNPs) by using chitosan, a biocompatible, biodegradable, natural polymer, as reducing and stabilizing agent. The formation of gold-chitosan nanocomposites was characterized by UV-vis absorption spectroscopy, transmission electron microscopy (TEM), x-ray diffraction (XRD) and Raman spectroscopy. The results show that the reaction temperature plays a crucial role in controlling the size, shape and crystalline structure of GNPs. In addition, it is demonstrated that chitosan can perform as a scaffold for the assembly of GNPs, which were successfully applied as substrate for surface-enhanced Raman scattering (SERS). To test the SERS activity, a relevant biological molecule--tryptophan--was adopted as the analyte.

Effect of Gold on the Corrosion Behavior of an Electroless Nickel/Immersion Gold Surface Finish

NASA Astrophysics Data System (ADS)

Bui, Q. V.; Nam, N. D.; Yoon, J. W.; Choi, D. H.; Kar, A.; Kim, J. G.; Jung, S. B.

2011-09-01

The performance of surface finishes as a function of the pH of the utilized plating solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. In addition, the surface finishes were examined by x-ray diffraction (XRD), and the contact angle of the liquid/solid interface was recorded. NiP films on copper substrates with gold coatings exhibited their highest coating performance at pH 5. This was attributed to the films having the highest protective efficiency and charge transfer resistance, lowest porosity value, and highest contact angle among those examined as a result of the strongly preferred Au(111) orientation and the improved surface wettability.

Optimally designed gold nanorattles with strong built-in hotspots and weak polarization dependence

NASA Astrophysics Data System (ADS)

Zhang, Xuemin; Wang, Tieqiang; Li, Yunong; Fu, Yu; Guo, Lei

2017-12-01

Localized electromagnetic fields generated by interparticle plasmon coupling suffer greatly from nonreproducibility because they are extremely sensitive to the nanoparticle aggregation status and the incident polarization. Here, we synthesize gold nanorattles that exhibit inherent aggregation-insensitive hotspots due to the intraparticle core-shell plasmon coupling, and investigate the structural effect on the intraparticle coupling strength and its polarization dependence. Through optimizing the structural parameters, we successfully synthesize gold nanorattles with strong built-in hotspots and weak polarization dependence. These aggregation-insensitive and weakly polarization-dependent hotspots make the Raman enhancement from nanorattle aggregates show an unusual weak dependence on the particle aggregation status, which therefore affords the opportunity to fabricate uniform and reproducible surface enhanced Raman scattering substrates.

X-ray and gamma ray emission from petawatt laser-driven nanostructured metal targets

NASA Astrophysics Data System (ADS)

Hill, Matthew; Allan, Peter; Brown, Colin; Hoarty, David; Hobbs, Lauren; James, Steven; Bargsten, Clayton; Hollinger, Reed; Rocca, Jorge; Park, Jaebum; Chen, Hui; London, Richard; Shepherd, Ronnie; Tommasini, Riccardo; Vinko, Sam; Wark, Justin; Marjoribanks, Robin; Neely, David; Spindloe, Chris

2016-10-01

Nano-wire arrays of nickel and gold have been fired at the Orion laser facility using high contrast 1 ω and 2 ω short pulse beams (0.7 ps pulse length, >1020 W cm-2 intensity). Time-resolved and time-integrated K-shell and M-shell emission have been characterized and compared to those of flat foils, investigating the capability of these metamaterial coatings to enhance laser-target coupling and X-ray emission. Bremsstrahlung emission of gamma rays and associated pair production via the Bethe-Heitler process have also been investigated by use of 1 mm-thick gold substrates attached to the gold nanowires. We present our latest experimental data and outline some potential future applications.

Solid State Research

DTIC Science & Technology

1990-02-15

the magnetic field configuration to obtain a more uniforml sputtering of the target. Substrates of lanthanium aluniinate (LaAIO 3 ), lanthanum gallate ...technologies, we have fabricated all-gold and all-niobium versions of the microstrip filters in order to verify device performance. Lanthanum

A highly oriented hybrid microarray modified electrode fabricated by a template-free method for ultrasensitive electrochemical DNA recognition

NASA Astrophysics Data System (ADS)

Shi, Lei; Chu, Zhenyu; Dong, Xueliang; Jin, Wanqin; Dempsey, Eithne

2013-10-01

Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors.Highly oriented growth of a hybrid microarray was realized by a facile template-free method on gold substrates for the first time. The proposed formation mechanism involves an interfacial structure-directing force arising from self-assembled monolayers (SAMs) between gold substrates and hybrid crystals. Different SAMs and variable surface coverage of the assembled molecules play a critical role in the interfacial directing forces and influence the morphologies of hybrid films. A highly oriented hybrid microarray was formed on the highly aligned and vertical SAMs of 1,4-benzenedithiol molecules with rigid backbones, which afforded an intense structure-directing power for the oriented growth of hybrid crystals. Additionally, the density of the microarray could be adjusted by controlling the surface coverage of assembled molecules. Based on the hybrid microarray modified electrode with a large specific area (ca. 10 times its geometrical area), a label-free electrochemical DNA biosensor was constructed for the detection of an oligonucleotide fragment of the avian flu virus H5N1. The DNA biosensor displayed a significantly low detection limit of 5 pM (S/N = 3), a wide linear response from 10 pM to 10 nM, as well as excellent selectivity, good regeneration and high stability. We expect that the proposed template-free method can provide a new reference for the fabrication of a highly oriented hybrid array and the as-prepared microarray modified electrode will be a promising paradigm in constructing highly sensitive and selective biosensors. Electronic supplementary information (ESI) available: Four-probe method for determining the conductivity of the hybrid crystal (Fig. S1); stability comparisons of the hybrid films (Fig. S2); FESEM images of the hybrid microarray (Fig. S3); electrochemical characterizations of the hybrid films (Fig. S4); DFT simulations (Fig. S5); cross-sectional FESEM image of the hybrid microarray (Fig. S6); regeneration and stability tests of the DNA biosensor (Fig. S7). See DOI: 10.1039/c3nr03097k