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Sample records for gold surfaces investigated

  1. Surface science investigations of oxidative chemistry on gold.

    PubMed

    Gong, Jinlong; Mullins, C Buddie

    2009-08-18

    Because of gold's resistance to oxidation and corrosion, historically chemists have considered this metal inert. However, decades ago, researchers discovered that highly dispersed gold particles on metal oxides are highly chemically active, particularly in low-temperature CO oxidations. These seminal findings spurred considerable interest in investigations and applications of gold-based materials. Since the discovery of gold's chemical activity at the nanoscale, researchers found that bulk gold also has interesting catalytic properties. Thus, it is important to understand and contrast the intrinsic chemical properties of bulk gold with those of nanoparticle Au. Despite numerous studies, the structure and active site of supported Au nanoclusters and the active oxygen species remain elusive, and model studies under well-controlled conditions could help identify these species. The {111} facet has the lowest surface energy and is the most stable and prevalent configuration of most supported gold nanoparticles. Therefore, a molecular-level understanding of the physical properties and surface chemistry of Au(111) could provide mechanistic details regarding the nature of Au-based catalysts and lead to improved catalytic processes. This Account focuses on our current understanding of oxidative chemistry on well-defined gold single crystals, predominantly from recent investigations on Au(111) that we have performed using modern surface science techniques. Our model system strategy allows us to control reaction conditions, which assists in the identification of reaction intermediates, the determination of the elementary reaction steps, and the evaluation of reaction energetics for rate-limiting steps. We have employed temperature-programmed desorption (TPD), molecular beam reactive scattering (MBRS), and Auger electron spectroscopy (AES) to evaluate surface oxidative chemistry. In some cases, we have combined these results with density functional theory (DFT) calculations

  2. Interactions of Bacterial Lipopolysaccharides with Gold Nanorod Surfaces Investigated by Refractometric Sensing.

    PubMed

    Abadeer, Nardine S; Fülöp, Gergő; Chen, Si; Käll, Mikael; Murphy, Catherine J

    2015-11-11

    The interface between nanoparticles and bacterial surfaces is of great interest for applications in nanomedicine and food safety. Here, we demonstrate that interactions between gold nanorods and bacterial surface molecules are governed by the nanoparticle surface coating. Polymer-coated gold nanorod substrates are exposed to lipopolysaccharides extracted from Pseudomonas aeruginosa, Salmonella enterica and Escherichia coli, and attachment is monitored using localized surface plasmon resonance refractometric sensing. The number of lipopolysaccharide molecules attached per nanorod is calculated from the shift in the plasmon maximum, which results from the change in refractive index after analyte binding. Colloidal gold nanorods in water are also incubated with lipopolysaccharides to demonstrate the effect of lipopolysaccharide concentration on plasmon shift, ζ-potential, and association constant. Both gold nanorod surface charge and surface chemistry affect gold nanorod-lipopolysaccharide interactions. In general, anionic lipopolysaccharides was found to attach more effectively to cationic gold nanorods than to neutral or anionic gold nanorods. Some variation in lipopolysaccharide attachment is also observed between the three strains studied, demonstrating the potential complexity of bacteria-nanoparticle interactions.

  3. Electrochemical investigations of 3-(3-thienyl) acrylic acid protected nanoclusters and planar gold surfaces.

    PubMed

    Nirmal, R G; Kavitha, A L; Berchmans, Sheela; Yegnaraman, V

    2007-06-01

    Formation of self assembled monolayers on gold surface by thiols and disulphides is a well known phenomenon and extensive research work has been carried out in this area with envisaged applications in the area of sensors, molecular electronics, lithography, device fabrication using bottom-up approach, etc. Recently, it has been established that thiophene molecules can self assemble on gold surface due to Au-S interactions. 3-(3-thienyl) acrylic acid, a bifunctional ligand is used in this work to form self-assembled monolayers on planar gold surfaces (two dimensional assemblies) and to prepare monolayer protected gold nano clusters (three-dimensional assemblies). The electron transfer blocking properties of the two-dimensional monolayers were evaluated by using standard redox probes like ferrocyanide anions and Ruthenium hexamine cations. The functionalisation of the two-dimensional and three-dimensional assemblies has been carried out with ferrocene carboxylic acid and the functionalised monolayers were characterized by Cyclic voltammetry. The formation of thienyl acrylic acid protected nanoclusters has been verified by TEM and surface plasmon resonance absorption. It has been observed that when thiophene based ligands are used as stabilizers for the formation of metal nanoparticles, they tend to aggregate as a result of pi-pi interactions between adjacent thiophene ligands. In this case it is found that aggregation is prevented. The substituent at the thiophene ring hinders pi-pi interactions. The quantised nature of electrochemical charging of these nanoparticles has been demonstrated by differential pulse voltammetry (DPV), which exhibit peak like features (coulomb's staircase). This work also explores the possibility of using 3-(3-thienyl) acrylic acid as building blocks or spacers on planar and colloidal gold surfaces for potential applications in the field of sensors and devices.

  4. In situ investigation of the mobility of small gold clusters on cleaved MgO surfaces

    NASA Technical Reports Server (NTRS)

    Metois, J. J.; Heinemann, K.; Poppa, H.

    1976-01-01

    The mobility of small clusters of gold (about 10 A in diameter) on electron-beam-cleaved MgO surfaces was studied by in situ transmission electron microscopy under controlled vacuum and temperature conditions. During the first 10 min following a deposition at room temperature, over 10 per cent of the crystallites moved over short distances (about 20 A) discontinuously, with a velocity greater than 150 A/sec. Eighty per cent of the mobility events were characterized by the avoidance of proximity of other crystallites, and this was tentatively explained as the result of repulsive elastic forces between the interacting crystallites.

  5. Surface-stabilized gold nanocatalysts

    DOEpatents

    Dai, Sheng [Knoxville, TN; Yan, Wenfu [Oak Ridge, TN

    2009-12-08

    A surface-stabilized gold nanocatalyst includes a solid support having stabilizing surfaces for supporting gold nanoparticles, and a plurality of gold nanoparticles having an average particle size of less than 8 nm disposed on the stabilizing surfaces. The surface-stabilized gold nanocatalyst provides enhanced stability, such as at high temperature under oxygen containing environments. In one embodiment, the solid support is a multi-layer support comprising at least a first layer having a second layer providing the stabilizing surfaces disposed thereon, the first and second layer being chemically distinct.

  6. Investigation of splashing phenomena during the impact of molten sub-micron gold droplets on solid surfaces.

    PubMed

    Shen, Daozhi; Zou, Guisheng; Liu, Lei; Duley, Walter W; Norman Zhou, Y

    2016-01-01

    The dynamics of splashing accompanying the impact of molten 800 nm diameter gold droplets on silicon, gold coated silicon, gold coated glass and polished solid gold surfaces has been studied. A novel method based on laser induced forward transfer has been developed to generate single submicron molten gold droplets. Splashing morphology has been characterized using Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) techniques. It is found that the splashing of submicron gold droplets upon impact is enhanced by high droplet impact energy achieved by reducing the droplet flight distance and that an air layer resulting in a bubble becomes trapped under the impacting droplets even when the size of the droplet is less than one micron. Our results show that, under these conditions, heat transfer between the submicron droplet and the solid substrate is more important than surface roughness and surface tension in the evolution of splashing. A theoretical model has been developed to simulate the splashing characteristics of submicron gold droplets during impact. Both the experimental data and the analytical model show that splashing is enhanced by high heat transfer rates to the surface.

  7. Cytochrome C on a gold surface: investigating structural relaxations and their role in protein-surface electron transfer by molecular dynamics simulations.

    PubMed

    Siwko, Magdalena E; Corni, Stefano

    2013-04-28

    Proteins immobilized on inorganic surfaces are important in technological fields such as biosensors, enzymatic biofuel cells and biomolecular electronics. In these frameworks, it has been demonstrated that some proteins are able to keep their functionality, although the latter may be somewhat modified by the interaction with the surface. Cytochrome C, an heme-based electron transfer protein, has been found to be able to exchange electrons with the gold surface on which it is immobilized, but some deviations from the expected electron transfer rates were evidenced [C. A. Bortolotti, et al., J. Phys. Chem. C 2007, 111, 12100-12105]. In this work we have used molecular dynamics simulations of (native and mutated) yeast cytochrome C supported on Au(111) to investigate the microscopic picture behind the experimental behavior of the molecule. In particular, we have focused on the structural re-arrangements due to the interactions with the surface. We found that, despite being secondary-structure preserving, they can profoundly affect protein-surface electronic coupling and, in turn, electron transfer rates, explaining experimental findings. The conformational flexibility of the protein in the region of the protein-surface bond is thus pivotal in determining the resulting ET functionality of the immobilized protein.

  8. High-resolution imaging of gold clusters on KBr(001) surfaces investigated by dynamic scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Barth, Clemens; Henry, Claude R.

    2004-09-01

    Dynamic scanning force microscopy (dynamic SFM) images of (001) surfaces of KBr which have been prepared by cleavage and further decorated by nanometre-sized gold clusters in UHV are presented. During scanning we could achieve atomic resolution on the KBr substrate surface; however, the clusters mostly appeared as hemisphere-like or fuzzy objects exhibiting only a few details of their internal structure. We performed force spectroscopy measurements above single clusters which might point to a charging of the clusters. We anticipate that mainly a long-range electrostatic interaction between the cluster and the macroscopic tip apex determines the appearance of the clusters. Information on the interior of the clusters can be gained only for short tip-cluster distances in the presence of a short-range, chemical interaction between the cluster and the tip atoms closest to the surface.

  9. Gold nanodisk array surface plasmon resonance sensor

    NASA Astrophysics Data System (ADS)

    Tian, Xueli

    Surface plasmon resonances in periodic metal nanostructures have been investigated for sensing applications over the last decade. The resonance wavelengths of the nanostructures are usually measured in the transmission or reflection spectrum for chemical and biological sensing. In this thesis, I introduce a nanoscale gap mediated surface plasmon resonance nanodisk array for displacement sensing and a super-period gold nanodisk grating enabled surface plasmon resonance spectrometer sensor. The super-period gold nanodisk grating has a small subwavelength period and a large diffraction grating period. Surface plasmon resonance spectra are measured in the first order diffraction spatial profiles captured by a charge-coupled device (CCD). A surface plasmon resonance sensor for the bovine serum albumin (BSA) protein nanolayer bonding is demonstrated by measuring the surface plasmon resonance shift in the first order diffraction spatial intensity profiles captured by the CCD.

  10. In situ synthesis and surface functionalization of gold nanoparticles with curcumin and their antioxidant properties: an experimental and density functional theory investigation

    NASA Astrophysics Data System (ADS)

    Singh, Dheeraj K.; Jagannathan, Ramya; Khandelwal, Puneet; Abraham, Priya Mary; Poddar, Pankaj

    2013-02-01

    Curcumin ((1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is an active component of turmeric; it is responsible for its characteristic yellow color and therapeutic potential, but its poor bioavailability remains a major challenge. In order to improve the bioavailability of curcumin, various approaches have been used. One of the possible approaches to increase the bioavailability of curcumin is its conjugation on the surface of metal nanoparticles. Therefore, in the present study, we report the binding of curcumin on the surface of gold nanoparticles (AuNPs). The AuNPs were synthesized by the direct reduction of HAuCl4 using curcumin in the aqueous phase, without the use of any other reducing agents. We found that curcumin acts both as a reducing and capping agent, stabilizing the gold sol for many months. Moreover, these curcumin-capped AuNPs also show good antioxidant activity which was confirmed by the DPPH (2,2-diphenyl-l-picrylhydrazyl) radical test. Thus, the surface functionalization of AuNPs with curcumin may pave a new way of using the curcuminoids towards possible drug delivery and therapeutics. Apart from the experimental study, a detailed quantum chemical calculation using density functional theory (DFT) has been performed, in order to investigate the formation of a complex of curcumin with Au3+ ions in different possible conformational isomeric forms. Our theoretical calculations indicate the evidence of electron transfer from curcumin into the Au center and essentially indicate that as a consequence of complexation, Au3+ ions are reduced to Au0. Our theoretical results also propose that it is the breakage of intramolecular H-bonding that probably leads to the increased availability of curcumin in the presence of gold ions and water molecules.Curcumin ((1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione) is an active component of turmeric; it is responsible for its characteristic yellow color and therapeutic

  11. Tuning plasmonic interaction between gold nanorings and a gold film for surface enhanced Raman scattering

    SciTech Connect

    Ye Jian; Lodewijks, Kristof; Lagae, Liesbet; Van Dorpe, Pol; Shioi, Masahiko; Kawamura, Tatsuro

    2010-10-18

    We investigate the plasmonic properties of gold nanorings in close proximity to a gold film. The rings have been fabricated using nanosphere lithography and are optimized to boost their near-infrared surface enhanced Raman scattering (SERS) effects. A SERS enhancement factor as large as 1.4x10{sup 7} has been achieved by tuning the separation between the gold nanorings and the gold film. In addition, we have numerically and experimentally demonstrated an enhanced tunability of the plasmon resonance wavelength and a narrowing of the plasmon linewidth for increasing ring-film interaction.

  12. Formation, structure, and orientation of gold silicide on gold surfaces

    NASA Technical Reports Server (NTRS)

    Green, A. K.; Bauer, E.

    1976-01-01

    The formation of gold silicide on Au films evaporated onto Si(111) surfaces is studied by Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED). Surface condition, film thickness, deposition temperature, annealing temperature, and heating rate during annealing are varied. Several oriented crystalline silicide layers are observed.

  13. Gold nanoparticles in the engineering of antibacterial and anticoagulant surfaces.

    PubMed

    Ehmann, Heike M A; Breitwieser, Doris; Winter, Sascha; Gspan, Christian; Koraimann, Günther; Maver, Uros; Sega, Marija; Köstler, Stefan; Stana-Kleinschek, Karin; Spirk, Stefan; Ribitsch, Volker

    2015-03-01

    Simultaneous antibacterial and anticoagulant surfaces have been prepared by immobilization of engineered gold nanoparticles onto different kinds of surfaces. The gold nanoparticle core is surrounded by a hemocompatible, anticoagulant polysaccharide, 6-O chitosan sulfate, which serves as reduction and stabilizing agent for the generation of gold nanoparticles in a microwave mediated reaction. The particle suspension shows anticoagulant activity, which is investigated by aPTT and PT testing on citrated blood samples of three patients suffering from congenital or acquired bleeding disorders. The amount of nanoparticles deposited on the surfaces is quantified by a quartz crystal microbalance with dissipation unit. All gold containing surfaces exhibit excellent antimicrobial properties against the chosen model organism, Escherichia coli MG 1655 [R1-16]. Moreover, blood plasma coagulation times of the surfaces are increased after deposition of the engineered nanoparticles as demonstrated by QCM-D.

  14. Electrically Conductive Polyimide Films Containing Gold Surface

    NASA Technical Reports Server (NTRS)

    Caplan, Maggie L.; Stoakley, Diane M.; St. Clair, Anne K.

    1994-01-01

    Polyimide films exhibiting high thermo-oxidative stability and including electrically conductive surface layers containing gold made by casting process. Many variations of basic process conditions, ingredients, and sequence of operations possible, and not all resulting versions of process yield electrically conductive films. Gold-containing layer formed on film surface during cure. These metallic gold-containing polyimides used in film and coating applications requiring electrical conductivity, high reflectivity, exceptional thermal stability, and/or mechanical integrity. They also find commercial potential in areas ranging from thin films for satellite antennas to decorative coatings and packaging.

  15. Surface plasmons in porous gold films

    NASA Astrophysics Data System (ADS)

    Rudenko, S. P.; Stetsenko, M. O.; Krishchenko, I. M.; Maksimenko, L. S.; Kaganovich, E. B.; Serdega, B. K.

    2016-04-01

    The surface plasmon resonance effects in porous gold (por-Au) films—nanocomposite porous films containing an ensemble of disordered gold nanoparticles—have been investigated by modulation-polarization spectroscopy. Por-Au films have been obtained by pulsed laser deposition (using a direct particle flow from an erosion torch formed by a YAG:Nd3+ laser in argon). The spectral and angular dependences of the polarization difference ρ(λ, θ) of internal-reflection coefficients of s- and p-polarized radiation in the Kretschmann geometry and the spectral dependences of isotropic reflection angles at ρ(θ) = 0 are measured. Two types of surface plasmon resonance are found: one occurs on isolated nanoparticles (dipole and multipole modes), and the other is due to the dipole-dipole interaction of neighboring nanoparticles. The frequency of electron plasma oscillations for the nanoparticle ensemble and the frequencies and decay parameters of resonances are determined. Dispersion relations for the radiative and nonradiative modes are presented. The negative sign of the dispersion branch of nonradiative modes of dipole-dipole interaction is explained by the spatial dispersion of permittivity. The relationships between the formation conditions of the films, their structure, and established resonance parameters (determining the resonant-optical properties of films) are discussed.

  16. Adsorption of human insulin on single-crystal gold surfaces investigated by in situ scanning tunnelling microscopy and electrochemistry.

    PubMed

    Welinder, Anna C; Zhang, Jingdong; Steensgaard, Dorte B; Ulstrup, Jens

    2010-09-14

    We have explored the adsorption of zinc-free human insulin on the three low-index single-crystalline Au(111)-, Au(100)- and Au(110)-surfaces in aqueous buffer (KH(2)PO(4), pH 5) by a combination of electrochemical scanning tunnelling microscopy (in situ STM) at single-molecule resolution and linear sweep, LSV, cyclic, CV, and square wave (SQWV) voltammetry.Multifarious electrochemical patterns were observed. Most attention was given to reductive desorption caused by insulin binding to the Au-surfaces via up to three disulfide groups per insulin monomer, presumably converted to single Au-S links. SQWV suggested the Au-S bond strength order Au(111) > Au(110) > Au(100) based on the reductive desorption potentials. The voltammetric diversity was paralleled by different in situ STM insulin adsorption modes on the three surfaces. Single-molecule resolution was achieved in all cases. The coverage followed the order Au(110) > Au(100) > Au(111) and differs from the reductive desorption order that records the Au-S bonding element. Evenly distributed single molecules were scattered over large Au(111)-terraces, with intriguing molecular arrays disclosed near the terrace edges. In comparison, high-density molecular scale structures were observed both over the terraces and across terrace edges on Au(100). Larger rectangular structures also appeared (8-12% coverage). These are Au-islands from the lift of the reconstruction. Notably, 10 x 10 nm(2) patches of highly ordered much smaller structures, possibly from insulin decomposition emerged sporadically within the dense insulin adlayer. Insulin adsorbed in highest coverage on the Au(110) and followed the directional surface topology with insulin molecules aligned in the Au(110)-surface grooves, occasionally "spilling over" and merging into larger structures.Adsorption, Au-S binding, and insulin unfolding are all parts of insulin surface behaviour and reflected in both voltammetry and in situ STM. In spite of these complications

  17. Topological states on the gold surface

    PubMed Central

    Yan, Binghai; Stadtmüller, Benjamin; Haag, Norman; Jakobs, Sebastian; Seidel, Johannes; Jungkenn, Dominik; Mathias, Stefan; Cinchetti, Mirko; Aeschlimann, Martin; Felser, Claudia

    2015-01-01

    Gold surfaces host special electronic states that have been understood as a prototype of Shockley surface states. These surface states are commonly employed to benchmark the capability of angle-resolved photoemission spectroscopy (ARPES) and scanning tunnelling spectroscopy. Here we show that these Shockley surface states can be reinterpreted as topologically derived surface states (TDSSs) of a topological insulator (TI), a recently discovered quantum state. Based on band structure calculations, the Z2-type invariants of gold can be well-defined to characterize a TI. Further, our ARPES measurement validates TDSSs by detecting the dispersion of unoccupied surface states. The same TDSSs are also recognized on surfaces of other well-known noble metals (for example, silver, copper, platinum and palladium), which shines a new light on these long-known surface states. PMID:26658826

  18. Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds.

    PubMed

    Abyaneh, Majid K; Parisse, Pietro; Casalis, Loredana

    2016-01-01

    Herein, we present the formation of gold nanorods (GNRs) on novel gold-poly(methyl methacrylate) (Au-PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (M w) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au-PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer M w and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower M w PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method. PMID:27547597

  19. Silicide surface phases on gold

    NASA Technical Reports Server (NTRS)

    Green, A. K.; Bauer, E.

    1981-01-01

    The crystalline silicide layers formed on (111) and (100) surfaces of Au films on various Si single-crystal substrates are studied by LEED and AES in conjunction with sputter-depth profiling as a function of annealing temperature. On the (111) surface, three basic silicide structures are obtained corresponding to layers of various thicknesses as obtained by different preparation conditions. The (100) surface shows only two different structures. None of the structures is compatible with the various bulk silicide structures deduced from X-ray diffraction. Using LEED as a criterion for the presence or absence of silicide on the surface, smaller layer thicknesses are obtained than reported previously on the basis of AES studies.

  20. Immobilization of gold nanoparticles on cell culture surfaces for safe and enhanced gold nanoparticle-mediated laser transfection.

    PubMed

    Kalies, Stefan; Heinemann, Dag; Schomaker, Markus; Gentemann, Lara; Meyer, Heiko; Ripken, Tammo

    2014-01-01

    In comparison to standard transfection methods, gold nanoparticle-mediated laser transfection has proven to be a versatile alternative. This is based on its minor influence on cell viability and its high efficiency, especially for the delivery of small molecules like small interfering RNA. However, in order to transfer it to routine usage, a safety aspect is of major concern: The avoidance of nanoparticle uptake by the cells is desired. The immobilization of the gold nanoparticles on cell culture surfaces can address this issue. In this study, we achieved this by silanization of the appropriate surfaces and the binding of gold nanoparticles to them. Comparable perforation efficiencies to the previous approaches of gold nanoparticle-mediated laser transfection with free gold nanoparticles are demonstrated. The uptake of the immobilized particles by the cells is unlikely. Consequently, these investigations offer the possibility of bringing gold nanoparticle-mediated laser transfection closer to routine usage.

  1. Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds

    PubMed Central

    Parisse, Pietro; Casalis, Loredana

    2016-01-01

    Summary Herein, we present the formation of gold nanorods (GNRs) on novel gold–poly(methyl methacrylate) (Au–PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (M w) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer M w and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower M w PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method. PMID:27547597

  2. Electrochemical assembling of methionine-gold nanoparticles and catalysis on the surface of glassy carbon electrode

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Wang, J. H.; Zhang, X. M.; Cao, W.; Ge, A.; Zhou, L.

    2014-12-01

    In this paper cyclic voltammetry was used for the synthesis of linear array spherical gold nanoparticles on the surface of glassy carbon electrode using methionine as a stable reagent. The methionine-gold nanoparticles on the surface of glassy electrode were obtained. The methionine-gold nanoparticles were characterized by cyclic voltammetry, scanning electron microscopy, energy dispersive spectrometry and powder X-ray diffraction. Electrochemical behavior of methionine at methionine-gold nanoparticle modified electrode was investigated. It was demonstrated that the methionine-gold nanoparticles can catalyze electrochemical transformations of methionine.

  3. Radiotracer investigation in gold leaching tanks.

    PubMed

    Dagadu, C P K; Akaho, E H K; Danso, K A; Stegowski, Z; Furman, L

    2012-01-01

    Measurement and analysis of residence time distribution (RTD) is a classical method to investigate performance of chemical reactors. In the present investigation, the radioactive tracer technique was used to measure the RTD of aqueous phase in a series of gold leaching tanks at the Damang gold processing plant in Ghana. The objective of the investigation was to measure the effective volume of each tank and validate the design data after recent process intensification or revamping of the plant. I-131 was used as a radioactive tracer and was instantaneously injected into the feed stream of the first tank and monitored at the outlet of different tanks. Both sampling and online measurement methods were used to monitor the tracer concentration. The results of measurements indicated that both the methods provided identical RTD curves. The mean residence time (MRT) and effective volume of each tank was estimated. The tanks-in-series model with exchange between active and stagnant volume was used and found suitable to describe the flow structure of aqueous phase in the tanks. The estimated effective volume of the tanks and high degree of mixing in tanks could validate the design data and confirmed the expectation of the plant engineer after intensification of the process.

  4. Control of gold surface diffusion on si nanowires.

    PubMed

    den Hertog, Martien I; Rouviere, Jean-Luc; Dhalluin, Florian; Desré, Pierre J; Gentile, Pascal; Ferret, Pierre; Oehler, Fabrice; Baron, Thiery

    2008-05-01

    Silicon nanowires (NW) were grown by the vapor-liquid-solid mechanism using gold as the catalyst and silane as the precursor. Gold from the catalyst particle can diffuse over the wire sidewalls, resulting in gold clusters decorating the wire sidewalls. The presence or absence of gold clusters was observed either by high angle annular darkfield scanning transmission electron microscopy images or by scanning electron microscopy. We find that the gold surface diffusion can be controlled by two growth parameters, the silane partial pressure and the growth temperature, and that the wire diameter also affects gold diffusion. Gold clusters are not present on the NW side walls for high silane partial pressure, low temperature, and small NW diameters. The absence or presence of gold on the NW sidewall has an effect on the sidewall morphology. Different models are qualitatively discussed. The main physical effect governing gold diffusion seems to be the adsorption of silane on the NW sidewalls. PMID:18422363

  5. Molecular Dynamics Studies of Gold Surfaces

    NASA Astrophysics Data System (ADS)

    Ercolessi, F.; Bartolini, A.; Garofalo, M.; Parrinello, M.; Tosatti, E.

    1987-01-01

    In the glue model the total cohesion of a metal is determined by a pairwise atom-atom effective interaction plus a many-body force (the "glue") which is introduced to ensure optimal coordination. Using parameters optimized for gold, we have studied the structural behaviour of the low index surfaces Au(100), Au(110) and Au(111). We have used a simulated annealing strategy based on molecular dynamics to search the lowest surface energy configuration. In all cases the optimal structures are found to be reconstructed, and remarkably similar to some experimentally suggested reconstruction models. The main driving mechanism is the formation of close-packed triangular surface layers favoured by the glue term.

  6. Probing the Surface Properties of Gold at Low Electrolyte Concentration.

    PubMed

    Tivony, Ran; Klein, Jacob

    2016-07-26

    Using the surface force balance (SFB), we studied the surface properties of gold in aqueous solution with low electrolyte concentration (∼10(-5) M and pH = 5.8), i.e., water with no added salt, by directly measuring the interaction between an ultrasmooth gold surface (ca. 0.2 nm rms roughness) and a mica surface. Under these conditions, specific adsorption of ions is minimized and its influence on the surface charge and surface potential of gold is markedly reduced. At open circuit potential, the electrostatic interaction between gold and mica was purely attractive and gold was found to be positively charged. This was further confirmed by force measurements against a positively charged surface, poly-l-lysine coated mica. Successive force measurements unambiguously showed that once gold and mica reach contact all counterions are expelled from the gap, confirming that at contact the surface charge of gold is equal and opposite in charge to that of mica. Further analysis of adhesion energy between the surfaces indicated that adhesion is mostly governed by vdW dispersion force and to a lesser extent by electrostatic interaction. Force measurements under external applied potentials showed that the gold-mica interaction can be regulated as a function of applied potential even at low electrolyte concentration. The gold-mica interaction was described very precisely by the nonlinearized Poisson-Boltzmann (PB) equation, where one of the surfaces is at constant charge, i.e., mica, and the other, i.e., gold, is at constant potential. Consequently, the gold surface potential could be determined accurately both at open circuit potential (OCP) and under different applied potentials. Using the obtained surface potentials, we were able to derive fundamental characteristics of the gold surface, e.g., its surface charge density and potential of zero charge (PZC), at very low electrolyte concentration. PMID:27357375

  7. Physiological investigation of gold nanorods toward watermelon.

    PubMed

    Wan, Yujie; Li, Junli; Ren, Hongxuan; Huang, Jin; Yuan, Hong

    2014-08-01

    The objective of the present study was to evaluate the phytotoxicity and oxidant stress of the gold nanorods toward watermelon, and hence give a quantitative risk assessment of both seeds and plants phase. The seed germination, the activity of antioxidant enzymes, and the contents of soluble protein and malondialdehyde (MDA) have been measured while the plant roots were observed by transmission electron microscopy (TEM). It was found that the gold nanorods significantly promoted the root elongation. Furthermore, the results on the enzymes activities of plant indicated that oxidative stress happened in the plant treated with gold nanorods. However, the gold nanorods resulted in the phytotoxicity toward plant especially at high concentration. The TEM images of the plant roots with and without the treatment of gold nanorods showed the significant different size of starch granules. In conclusion, significant physiological changes of plant occurred after treatment with the gold nanorods. PMID:25936063

  8. Thin gold layer in Ni electroforming process: optical surface characterization

    NASA Astrophysics Data System (ADS)

    Sironi, G.; Spiga, D.; Pareschi, G.; Missaglia, N.; Paganini, L.

    2009-08-01

    Mandrel replication by Nickel electroforming is a well-suited process to manufacture X-ray mirrors, making use of Gold layer playing the twofold role of release agent and reflective coating. To increase the optical performances of mirrors it is crucial to minimize the impact of X-ray scattering effects related to surface microroughness, especially when the mirror is intended to operate in hard X-rays. In this case, the Gold layer simply acts as release agent because the reflection is demanded to interferential over-coatings. Even though the replicated optical surface is usually believed to reproduce the smooth topography of the master, a surface degradation is commonly observed. Such a worsening can also suffer from a contribution from the spontaneous roughness growth of the Gold layer itself: if this is the case, the mirror's optical quality could potentially benefit from the utilization of a thin Gold layer (< 100 nm) instead of the traditional thick gold layer (> 100 nm). To prove the effectiveness of the Gold thickness reduction, a microroughness characterization of replicated thin gold layers has been achieved. We report here a preliminary roughness study of 3 electroformed Ni samples replicated from a super-polished Zerodur flat master with various Gold layer thicknesses, in the spectral range 0.02-1000 μm. The study is organized as follows: (a) characterization of the 3 replicated samples; (b) comparison of the Gold roughness for thin vs. thick layers; (c) comparison of the two sides of Gold layers.

  9. Impedimetric investigation of gold nanoparticles - guanine modified electrode

    NASA Astrophysics Data System (ADS)

    Vulcu, A.; Pruneanu, S.; Berghian-Grosan, C.; Olenic, L.; Muresan, L. M.; Barbu-Tudoran, L.

    2013-11-01

    In this paper we report the preparation of a modified electrode with gold nanoparticles and guanine. The colloidal suspension of gold nanoparticles was obtained by Turkevich method and was next analyzed by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The gold electrode was modified by self-assembling the gold nanoparticles with guanine, the organic molecule playing also the role of linker. The electrochemical characteristics of the bare and modified electrode were investigated by Electrochemical Impedance Spectroscopy (EIS). A theoretical model was developed based on an electrical equivalent circuit which contain solution resistance (Rs), charge transfer resistance (Rct), Warburg impedance (ZW) and double layer capacitance (Cdl).

  10. Influence of surface potential on the adhesive force of radioactive gold surfaces.

    PubMed

    Kweon, Hyojin; Yiacoumi, Sotira; Lee, Ida; McFarlane, Joanna; Tsouris, Costas

    2013-09-24

    Radioactive particles may acquire surface potential through self-charging, and thus can behave differently from natural aerosols in atmospheric systems with respect to aggregation, deposition, resuspension, and transport to areas surrounding a radioactive source. This work focuses on the adhesive force between radioactive particles and metallic surfaces, which relates to the deposition and resuspension of particles on surrounding surfaces. Scanning surface potential microscopy was employed to measure the surface potential of radioactive gold foil. Atomic force microscopy was used to investigate the adhesive force for gold that acquired surface charge either by irradiation or by application of an equivalent electrical bias. Overall, the adhesive force increases with increasing surface potential or relative humidity. However, a behavior that does not follow the general trend was observed for the irradiated gold at a high decay rate. A comparison between experimental measurements and calculated values revealed that the surface potential promotes adhesion. The contribution of the electrostatic force at high levels of relative humidity was lower than the one found using theoretical calculations due to the effects caused by enhanced adsorption rate of water molecules under a high surface charge density. The results of this study can be used to provide a better understanding of the behavior of radioactive particles in atmospheric systems.

  11. Ultrafast Imaging of Surface Plasmons Propagating on a Gold Surface

    SciTech Connect

    Gong, Yu; Joly, Alan G.; Hu, Dehong; El-Khoury, Patrick Z.; Hess, Wayne P.

    2015-05-13

    We record time-resolved nonlinear photoemission electron microscopy (tr-PEEM) images of propagating surface plasmons (PSPs) launched from a lithographically patterned rectangular trench on a flat gold surface. Our tr-PEEM scheme involves a pair of identical, spatially separated, and interferometrically-locked femtosecond laser pulses. Power dependent PEEM images provide experimental evidence for a sequential coherent nonlinear photoemission process, in which one laser source creates a PSP polarization state through a linear interaction, and the second subsequently probes the prepared state via two photon photoemission. The recorded time-resolved movies of a PSP allow us to directly measure various properties of the surface-bound wave packet, including its carrier wavelength (785 nm) and group velocity (0.95c). In addition, tr-PEEM in concert with finite-difference time domain simulations together allow us to set a lower limit of 75 μm for the decay length of the PSP on a 100 nm thick gold film.

  12. Surface enhanced Raman scattering investigation of the halide anion effect on the adsorption of 1,2,3-triazole on silver and gold colloidal nanoparticles.

    PubMed

    Pergolese, Barbara; Muniz-Miranda, Maurizio; Bigotto, Adriano

    2005-05-19

    The halide anion effect on the adsorption of 1,2,3-triazole on Ag and Au colloidal nanoparticles has been investigated by means of surface enhanced Raman scattering (SERS), UV-visible absorption spectroscopy, and scanning electron microscopy. To interpret the SERS spectra, the vibrational spectra of 1,2,3-triazole were assigned with the help of density functional theoretical (DFT) calculations of the two tautomers of 1,2,3-triazole, both free and bound to Ag and Au adatoms. Upon addition of halide anions, both tautomers interact with the Ag surface through one nitrogen atom. Analogous behavior is observed in the case of basified Au colloids, whereas at the usual pH of these hydrosols (approximately 6) the adsorption of 1,2,3-triazole is the same of that observed in halide-free colloids.

  13. Interaction of Gold Clusters with a Hydroxylated Surface

    SciTech Connect

    Jiang, Deen; Overbury, Steven {Steve} H; Dai, Sheng

    2011-01-01

    We explore the interaction between gold nanoclusters and a fully hydroxylated surface, Mg(OH){sub 2}'s basal plane, by using a density functional theory-enabled local basin-hopping technique for global-minimum search. We find strong interaction of gold nanoclusters with the surface hydroxyls via a short bond between edge Au atoms and O atoms of the -OH groups. We expect that this strong interaction is ubiquitous on hydroxylated support surfaces and helps the gold nanoclusters against sintering, thereby contributing to their CO-oxidation activity at low temperatures.

  14. Atomically precise gold nanocrystal molecules with surface plasmon resonance.

    PubMed

    Qian, Huifeng; Zhu, Yan; Jin, Rongchao

    2012-01-17

    Since Faraday's pioneering work on gold colloids, tremendous scientific research on plasmonic gold nanoparticles has been carried out, but no atomically precise Au nanocrystals have been achieved. This work reports the first example of gold nanocrystal molecules. Mass spectrometry analysis has determined its formula to be Au(333)(SR)(79) (R = CH(2)CH(2)Ph). This magic sized nanocrystal molecule exhibits fcc-crystallinity and surface plasmon resonance at approximately 520 nm, hence, a metallic nanomolecule. Simulations have revealed that atomic shell closing largely contributes to the particular robustness of Au(333)(SR)(79), albeit the number of free electrons (i.e., 333 - 79 = 254) is also consistent with electron shell closing based on calculations using a confined free electron model. Guided by the atomic shell closing growth mode, we have also found the next larger size of extraordinarily stability to be Au(~530)(SR)(~100) after a size-focusing selection--which selects the robust size available in the starting polydisperse nanoparticles. This work clearly demonstrates that atomically precise nanocrystal molecules are achievable and that the factor of atomic shell closing contributes to their extraordinary stability compared to other sizes. Overall, this work opens up new opportunities for investigating many fundamental issues of nanocrystals, such as the formation of metallic state, and will have potential impact on condensed matter physics, nanochemistry, and catalysis as well.

  15. Thin gold layer in NiCo and Ni electroforming process: optical surface characterization

    NASA Astrophysics Data System (ADS)

    Sironi, G.; Spiga, D.; Raimondi, L.; Pareschi, G.; Orlandi, A.; Borghi, G.; Missaglia, N.; Negri, B.

    2010-07-01

    Mandrel replication by NiCo electroforming is an upgrade of the well-suited X-ray mirrors manufacturing process with pure Nickel. In this process, a Gold layer deposited on the mandrel acts as release agent and, at the same time, as reflective coating. To increase the optical performances of X-ray mirrors, the replicated optical surface is meant to reproduce the smooth topography of the mandrel: a surface degradation is commonly observed, indeed. A factor leading to surface smoothness worsening can be the spontaneous roughness growth of the Gold layer itself; therefore, the optical quality of the reflecting surface might be improved by optimizing the Gold layer thickness. A preliminary study, aimed at investigating the effects of Gold thickness reduction (< 100 nm Vs. the usual 200 nm), had already been dealt in the spectral range 0.02-1000 μm: measurements performed on flat electroformed samples showed that the Gold thickness reduction chiefly affects the roughness around 1 μm. Here we presents a study of the effectiveness of a Gold layer with reduced (< 100 nm) thickness in the NiCo X-ray mirrors electroforming, aimed at surface micro-roughness mitigation. The characterization, in the spectral range 0.02-1000 μm, of 3 X-ray mirrors manufactured utilizing Gold layers with different thickness values from a flight mandrel is reported. The performed investigation is organized as follows: (a) characterization of the flight mandrel; (b) dependence of the micro-roughness from different Gold layers thicknesses supported by XRD study; (c) comparison of the micro-roughness of mirrors manufactured in NiCo in Ni, with the same Gold layer thickness. As a conclusive remark the effects of the Gold layer thinning on the angular degradation at high energy are reported.

  16. SERS, XPS, and DFT Study of Adenine Adsorption on Silver and Gold Surfaces.

    PubMed

    Pagliai, Marco; Caporali, Stefano; Muniz-Miranda, Maurizio; Pratesi, Giovanni; Schettino, Vincenzo

    2012-01-19

    The adsorption of adenine on silver and gold surfaces has been investigated combining density functional theory calculations with surface-enhanced Raman scattering and angle-resolved X-ray photoelectron spectroscopy measurements, obtaining useful insight into the orientation and interaction of the nucleobase with the metal surfaces.

  17. Nanomechanics of Bidentate Thiolate Ligands on Gold Surfaces

    NASA Astrophysics Data System (ADS)

    Zoloff Michoff, Martin E.; Ribas-Arino, Jordi; Marx, Dominik

    2015-02-01

    The effect of the chain length separating sulfur atoms in bidentate thiols attached to defective gold surfaces on the rupture of the respective molecule-gold junctions has been studied computationally. Thermal desorption always yields cyclic disulfides. In contrast, mechanochemical desorption leads to cyclic gold complexes, where metal atoms are extracted from the surface and kept in tweezer-like arrangements by the sulfur atoms. This phenomenon is rationalized in terms of directional mechanical manipulation of Au-Au bonds and Au-S coordination numbers. Moreover, the flexibility of the chain is shown to crucially impact on the mechanical strength of the junction.

  18. Investigations of corrosion phenomena on gold coins with SIMS

    NASA Astrophysics Data System (ADS)

    Mayerhofer, K. E.; Piplits, K.; Traum, R.; Griesser, M.; Hutter, H.

    2005-09-01

    In order to establish a new handling procedure for contaminated coins, the Coin Cabinet and the Conservation Science Department of the Kunsthistorisches Museum, Vienna, initiated a research project on corrosion effects of gold coins. By now, investigations on historic and contemporary coins included optical microscopy, scanning electron microscopy (SEM), Auger electron microscopy (AES), X-ray photoelectron microscopy (XPS), and electrochemical methods showing the distribution of pollutants. This work focuses on secondary ion mass spectrometry (SIMS) investigations merely showing the distribution of electronegative elements, such as sulfur, oxygen, and chlorine on the surface. Sulfur is highly suspected of causing the observed corrosion phenomena, and is indeed enriched near polluting splints. Since SIMS is a destructive method, the investigated samples are test coins with intentionally added impurities. These coins were manufactured in cooperation with the Austrian Mint. They were treated with potassium polysulfide (K 2S x) for 8 h gaining a rapid corrosion of the surface. SIMS mass spectra, depth profiles, and images were done (a) at non-polluted areas, (b) near polluted areas with slight coloring, and (c) directly at polluting stains showing enrichments of sulfur and chlorine. Due to the success of these investigations further studies on historic coins are intended.

  19. Competition between surface trapping and nonradiative energy transfer to gold nanofilm

    PubMed Central

    Yang, Zhenling; Liu, Yuqiang; He, Xing; Wen, Yanan; Yang, Yanqiang

    2010-01-01

    Nonradiative resonant energy transfer from CdSeS quantum dot to gold nanofilm was investigated by taking nanosecond and picosecond time resolved photoluminescence measurements. Surface plasma resonant absorption peak of gold nanofilm was adjusted to meet the near resonant conditions with the fluorescence peak of quantum dot by changing the thickness. Surface trapping state was proved to be the origin of the long lifetime component by comparing fresh and eight months aged quantum dot. It was observed that the excitonic state lifetime of the quantum dots was reduced by nonradiative resonant energy transfer to gold nanofilm. Nonradiative resonant energy transfer time, which was comparable with the surface trapping time, was calculated based on the data of picosecond photoluminescence measurements. No nonradiative energy transfer from surface trapping state to gold nanofilm, thus the lifetime of surface trapping state was not affected obviously. It is suggested that in the assembly combined with quantum dot and gold nanostructure, nonradiative energy transfer will occur after the population of excitonic state, and compete with surface trapping process. The interactions between surface trapping state and gold nanoflim were not exhibited. PMID:21124724

  20. Characterization of single- and double-stranded DNA on gold surfaces.

    PubMed

    Moses, Selina; Brewer, Scott H; Lowe, Lisa B; Lappi, Simon E; Gilvey, Lauren B G; Sauthier, Marc; Tenent, Robert C; Feldheim, Daniel L; Franzen, Stefan

    2004-12-01

    Single- and double-stranded deoxy ribonucleic acid (DNA) molecules attached to self-assembled monolayers (SAMs) on gold surfaces were characterized by a number of optical and electronic spectroscopic techniques. The DNA-modified gold surfaces were prepared through the self-assembly of 6-mercapto-1-hexanol and 5'-C(6)H(12)SH -modified single-stranded DNA (ssDNA). Upon hybridization of the surface-bound probe ssDNA with its complimentary target, formation of double-stranded DNA (dsDNA) on the gold surface is observed and in a competing process, probe ssDNA is desorbed from the gold surface. The competition between hybridization of ssDNA with its complimentary target and ssDNA probe desorption from the gold surface has been investigated in this paper using X-ray photoelectron spectroscopy, chronocoulometry, fluorescence, and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS). The formation of dsDNA on the surface was identified by PM-IRRAS by a dsDNA IR signature at approximately 1678 cm(-)(1) that was confirmed by density functional theory calculations of the nucleotides and the nucleotides' base pairs. The presence of dsDNA through the specific DNA hybridization was additionally confirmed by atomic force microscopy through colloidal gold nanoparticle labeling of the target ssDNA. Using these methods, strand loss was observed even for DNA hybridization performed at 25 degrees C for the DNA monolayers studied here consisting of attachment to the gold surfaces by single Au-S bonds. This finding has significant consequence for the application of SAM technology in the detection of oligonucleotide hybridization on gold surfaces.

  1. Investigation of gold embrittlement in connector solder joints

    NASA Technical Reports Server (NTRS)

    Lane, F. L.

    1972-01-01

    An investigation was performed to determine to what extent typical flight connector solder joints may be embrittled by the presence of gold. In addition to mapping of gold content in connector solder joints by an electron microprobe analyzer, metallographic examinations and mechanical tests (thermal shock, vibration, impact and tensile strength) were also conducted. A description of the specimens and tests, a discussion of the data, and some conclusions are presented.

  2. Tailoring surface plasmon resonance and dipole cavity plasmon modes of scattering cross section spectra on the single solid-gold/gold-shell nanorod

    NASA Astrophysics Data System (ADS)

    Chou Chau, Yuan-Fong; Lim, Chee Ming; Lee, Chuanyo; Huang, Hung Ji; Lin, Chun-Ting; Kumara, N. T. R. N.; Yoong, Voo Nyuk; Chiang, Hai-Pang

    2016-09-01

    Tunable surface plasmon resonance (SPR) and dipole cavity plasmon modes of the scattering cross section (SCS) spectra on the single solid-gold/gold-shell nanorod have been numerically investigated by using the finite element method. Various effects, such as the influence of SCS spectra under x- and y-polarizations on the surface of the single solid-gold/gold-shell nanorod, are discussed in detail. With the single gold-shell nanorod, one can independently tune the relative SCS spectrum width by controlling the rod length and rod diameter, and the surface scattering by varying the shell thickness and polarization direction, as well as the dipole peak energy. These behaviors are consistent with the properties of localized SPRs and offer a way to optically control and produce selected emission wavelengths from the single solid-gold/gold-shell nanorod. The electric field and magnetic distributions provide us a qualitative idea of the geometrical properties of the single solid-gold/gold-shell nanorod on plasmon resonance.

  3. Influence of supported gold particles on the surface reactions of diethylamine on TiO2

    NASA Astrophysics Data System (ADS)

    Sarmiento-Lopez, Adan G.; Berumen-España, Gerardo; Lopez-Serrano, Cesar; Fierro-Gonzalez, Juan C.

    2016-11-01

    The adsorption and reactions of diethylamine on the surfaces of TiO2 and TiO2-supported gold samples were investigated by infrared (IR) spectroscopy and mass spectrometry. IR spectra measured as the samples were treated in flowing diethylamine at room temperature indicate that the amine was preferentially adsorbed molecularly on surface Ti4 + sites. Thermal treatment of the samples with flowing diethylamine led to the formation of ethylene and acetonitrile as dehydrogenation products. The data show that the reactions occurred at lower temperatures in the presence of supported gold samples than on TiO2, and IR spectra recorded under reaction conditions show evidence of amine-derived surface species bonded to gold nanoparticles that could be regarded as reaction intermediates. The results indicate that the gold nanoparticles provide sites for subtraction and recombination of hydrogen atoms from the amine, ensuing its dehydrogenation.

  4. Femtosecond laser-induced periodic surface structural formation on sapphire with nanolayered gold coating

    NASA Astrophysics Data System (ADS)

    Yin, Kai; Wang, Cong; Duan, Ji'an; Guo, Chunlei

    2016-09-01

    Sapphire has a potential as a new generation of electronics display. However, direct processing of sapphire surface by visible or near-IR laser light is challenging since sapphire is transparent to these wavelengths. In this study, we investigate the formation of femtosecond laser-induced periodic surface structures (LIPSSs) on sapphire coated with nanolayered gold film. We found a reduced threshold by about 25 % in generating uniform LIPSSs on sapphire due to the nanolayered gold film. Different thickness of nanolayered gold films are studied, and it is shown that the change in thickness does not significantly affect the threshold reduction. It is believed that the diffusion of hot electrons in the gold films increases interfacial carrier density and electron-phonon coupling that results in a reduced threshold and more uniform periodic surface structure generation.

  5. Nitrite-triggered surface plasmon-assisted catalytic conversion of p-aminothiophenol to p,p'-dimercaptoazobenzene on gold nanoparticle: surface-enhanced Raman scattering investigation and potential for nitrite detection.

    PubMed

    Liu, Xiangjiang; Tang, Longhua; Niessner, Reinhard; Ying, Yibin; Haisch, Christoph

    2015-01-01

    The stunning large enhancement factor (∼10(8)) of the surface-enhanced Raman scattering (SERS) effect leads people to wonder about the underlying enhancement mechanisms of the effect. But, a strong evidence of the existence of one commonly accepted mechanism (chemical enhancement), the origin of the symbolic "b2" bands (ca. 1140,1390, 1432 cm(-1)) of p-aminothiophenol (PATP), was recently found to be a false explanation, which were actually arisen from the product of a surface plasmon-assisted coupling reaction of PATP, p,p'-dimercaptoazobenzene (DMAB). However, the debate is far from over, especially because the mechanism of the above reaction has not been fully understood yet. In this paper, we for the first time report a new surface plasmon-assisted catalytic conversion of PATP to DMAB that NO2(-) ions can trigger the formation of DMAB on gold nanoparticles (GNPs) suspension under light illumination. The mechanism of the conversion is also discussed. All relevant data suggest the nitrite-triggered conversion of PATP to DMAB on GNPs is a surface plasmon-assisted oxidation reaction, involving transfer of multiple electrons from PATP to NO2(-) (electron acceptors) and protons, leading to the formation of DMAB. The proposed mechanisms may also help to understand the unclear surface plasmon-assisted catalytic coupling of PATP on the SERS substrates. Furthermore, inspired by the high selectivity of the above nitrite-triggered catalysis reaction, a simple and fast nitrite screening method was also developed, exhibiting good sensitivity. Considering other advantages of the assay, such as rapidness, simplicity of the detection procedures, and requirement of no sample pretreatment, it is a promising method for on-site fast screening or point-of-care application. PMID:25437255

  6. Electrical bending actuation of gold-films with nanotextured surfaces

    NASA Astrophysics Data System (ADS)

    Kwan, K. W.; Gao, P.; Martin, C. R.; Ngan, A. H. W.

    2015-01-01

    An actuating material system comprising a gold-film with nanotextured surface was fabricated. Using electroless gold plating onto a substrate of porous anodized aluminum oxide, a thin film of gold with a high density of short gold nanofibers on its surface was made. When one end of such a film was connected to an ion generator, bending was achieved upon electrical charging in air. Experiments showed that the free end of an 8 mm film could be displaced by more than 1.6 mm with a bending strain of 0.08%. In contrast with other types of thin-film artificial muscle materials, the present Au-film did not require any electrolyte to function. With the relatively easy fabrication method, this nanotextured film shows promising actuation behavior in air.

  7. Impedimetric investigation of gold nanoparticles - guanine modified electrode

    SciTech Connect

    Vulcu, A.; Pruneanu, S.; Berghian-Grosan, C.; Olenic, L.; Muresan, L. M.; Barbu-Tudoran, L.

    2013-11-13

    In this paper we report the preparation of a modified electrode with gold nanoparticles and guanine. The colloidal suspension of gold nanoparticles was obtained by Turkevich method and was next analyzed by UV-Vis spectroscopy and Transmission Electron Microscopy (TEM). The gold electrode was modified by self-assembling the gold nanoparticles with guanine, the organic molecule playing also the role of linker. The electrochemical characteristics of the bare and modified electrode were investigated by Electrochemical Impedance Spectroscopy (EIS). A theoretical model was developed based on an electrical equivalent circuit which contain solution resistance (R{sub s}), charge transfer resistance (R{sub ct}), Warburg impedance (Z{sub W}) and double layer capacitance (C{sub dl})

  8. Approach and Coalescence of Gold Nanoparticles Driven by Surface Thermodynamic Fluctuations and Atomic Interaction Forces.

    PubMed

    Wang, Jiadao; Chen, Shuai; Cui, Kai; Li, Dangguo; Chen, Darong

    2016-02-23

    The approach and coalescence behavior of gold nanoparticles on a silicon surface were investigated by experiments and molecular dynamics simulations. By analyzing the behavior of the atoms in the nanoparticles in the simulations, it was found that the atoms in a single isolated nanoparticle randomly fluctuated and that the surface atoms showed greater fluctuation. The fluctuation increased as the temperature increased. When there were two or more neighboring nanoparticles, the fluctuating surface atoms of the nanoparticles "flowed" toward the neighboring nanoparticle because of atomic interaction forces between the nanoparticles. With the surface atoms "flowing", the gold nanoparticles approached and finally coalesced. The simulation results were in good agreement with the experimental results. It can be concluded that surface thermodynamic fluctuations and atomic interaction forces are the causes of the approach and coalescence behavior of the gold nanoparticles. PMID:26756675

  9. Electrochemical accumulation of visible gold on pyrite and arsenopyrite surfaces

    NASA Astrophysics Data System (ADS)

    Möller, P.; Kersten, G.

    1994-09-01

    In galvanic cell arrangements gold is electrochemically deposited on semiconducting sulfide minerals (pyrite, arsenopyrite, chalcopyrite) from aerated as well as H2S-saturated, gold-bearing 1 M KCl solutions. Observed cell potential differences of about 0.4 0.6 V in setups with one sulfide in aerated (cathode) and the other in H2S-saturated (anode) solutions are comparable with known “self-potentials” of natural sulfide ore bodies. Gold preferentially accumulates on the cathode, i.e. under oxidizing conditions. Linked sulfides of variable composition in the same environment, either oxidizing or reducing, yield potential differences up to 20 mV. Such assemblages simulate conditions typically occurring at surfaces of chemically inhomogeneous single crystals (e.g. zonation). Depending on chemical composition, sulfide minerals show either n- or p-type conductivity. Visible gold is preferentially accumulated on individual domains of sulfide surfaces that act as cathodes, i.e. p-type conductors in n-p junctions. The experimental results are discussed in view of electrochemical accumulation of visible gold on sulfides in nature. Arsenic is the most important element in establishing p-type conductivity of pyrite and arsenopyrite. This feature may explain why As is such a powerful pathfinder in gold exploration.

  10. Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO.

    PubMed

    Pabisiak, Tomasz; Winiarski, Maciej J; Ossowski, Tomasz; Kiejna, Adam

    2016-07-21

    Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster.

  11. Adsorption of gold subnano-structures on a magnetite(111) surface and their interaction with CO.

    PubMed

    Pabisiak, Tomasz; Winiarski, Maciej J; Ossowski, Tomasz; Kiejna, Adam

    2016-07-21

    Gold deposited on iron oxide surfaces can catalyze the oxidation of carbon monoxide. The adsorption of gold subnano-structures on the Fe-rich termination of the magnetite(111) surface has been investigated using density functional theory. The structural, energetic, and electronic properties of gold/magnetite systems have been examined for vertical and flattened configurations of adsorbed Aun (n = 1-4) species. Single gold adatoms strongly bonded to the iron atoms of the Fe3O4(111) surface appear to be negatively charged, and consequently increase the work function. For a more stable class of larger, flattened Aun structures the adsorption binding energy per adatom is substantially increased. The structures exhibit a net positive charge, with the Au atoms binding with the oxide having distinctly cationic character. A charge transfer from the larger gold structures to the substrate is consistent with the lowering of the work function. The bonding of a CO molecule to a Au monomer on the Fe3O4(111) surface has been found nearly as strong as that to the iron site of the bare Fe-terminated surface. However, CO bonding to larger, oxide supported Aun structures is distinctly stronger than that to the bare oxide surface. Upon CO adsorption all Aun structures are cationic and CO shows a tendency to bind to the most cationic atom of the Aun cluster. PMID:27332962

  12. Organometallic Chemistry and catalysis on gold metal surfaces

    SciTech Connect

    Angelici, Robert J.

    2007-11-21

    As in transition metal complexes, C{triple_bond}N-R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of C{triple_bond}N-R, primary amines (R{prime}NH{sub 2}) and O{sub 2} to give carbodiimides (R{prime}-N{double_bond}C{double_bond}N-R). An analogous reaction of C{triple_bond}O, RNH{sub 2}, and O{sub 2} gives isocyanates (R-N{double_bond}C{double_bond}O), which react with additional amine to give urea (RNH){sub 2}C{double_bond}O products. The gold-catalyzed reaction of C{triple_bond}N-R with secondary amines (HNR{prime}{sub 2}) and O{sub 2} gives mixed ureas RNH(CO)NR{prime}{sub 2}. In another type of gold-catalyzed reaction, secondary amines HN(CH{sub 2}R){sub 2} react with O{sub 2} to undergo dehydrogenation to the imine product, RCH{double_bond}N(CH{sub 2}R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.

  13. Sputtered gold films for surface-enhanced Raman scattering

    SciTech Connect

    Maya, L.; Vallet, C.E.; Lee, Y.H.

    1997-03-01

    Sputtered gold films in a pure form or as nanocomposites in silica or silicon nitride were screened for surface-enhanced Raman scattering (SERS) activity using Rhodamine 6G as a probe. The films were prepared by sputtering pure gold or solidified Au{endash}Si alloys in plasmas generated in a dc glow discharge apparatus. The plasmas were produced with argon, nitrogen, or argon{endash}oxygen as the sputtering gas to directly deposit gold films or in the latter case a gold oxide intermediate. The alloys produce nanocomposite films in a silicon nitride or silica matrix depending on the plasma gas. SERS activity was detected in some of the films thus leading to a search for the critical parameters that controlled this phenomenon. The films were characterized by profilometry, x-ray diffraction, and atomic force microscopy. SERS activity was found to be correlated to crystallite size in the 10{endash}25 nm range and to roughness larger than 15 nm, and it was independent of film thickness. Sputtered gold films, particularly those containing the gold as a nanocomposite in silica are attractive media for SERS because of excellent adherence, ruggedness, and simplicity in preparation. {copyright} {ital 1997 American Vacuum Society.}

  14. Ultralow fouling polyacrylamide on gold surfaces via surface-initiated atom transfer radical polymerization.

    PubMed

    Liu, Qingsheng; Singh, Anuradha; Lalani, Reza; Liu, Lingyun

    2012-04-01

    In this work, polyacrylamide is investigated as an ultralow fouling surface coating to highly resist protein adsorption, cell adhesion, and bacterial attachment. Polyacrylamide was grafted on gold surfaces via surface-initiated atom transfer radical polymerization (ATRP). Protein adsorption from a wide range of biological media, including single protein solutions of fibrinogen, bovine serum albumin, and lysozyme, dilute and undiluted human blood serum, and dilute and undiluted human blood plasma, was studied by surface plasmon resonance (SPR). Dependence of the protein resistance on polyacrylamide film thickness was examined. With the optimal film thickness, the adsorption amount of all three single proteins on polyacrylamide-grafted surfaces was <3 pg/mm(2), close to the detection limit of SPR. The average nonspecific adsorptions from 10% plasma, 10% serum, 100% plasma, and 100% serum onto the polyacrylamide-grafted surfaces were 5, 6.5, 17, and 28 pg/mm(2), respectively, comparable (if not better) than the adsorption levels on poly(ethylene glycol) (PEG) and zwitterionic poly(sulfobetaine methacrylate) surfaces, the best antifouling materials known to date. The polyacrylamide-grafted surfaces were also shown strongly resistant to adhesion from bovine aortic endothelial cells and two bacterial species, Gram-positive Staphylococcus epidermidis ( S. epidermidis ) and Gram-negative Pseudomonas aeruginosa ( P. aeruginosa ). Strong hydrogen bond with water is considered the key attribute for the ultralow fouling properties of polyacrylamide. This is the first work to graft gold surfaces with polyacrylamide brushes via ATRP to achieve ultralow fouling surfaces, demonstrating that polyacrylamide is a promising alternative to traditional PEG-based antifouling materials. PMID:22385371

  15. Analytical performance of molecular beacons on surface immobilized gold nanoparticles of varying size and density.

    PubMed

    Uddayasankar, Uvaraj; Krull, Ulrich J

    2013-11-25

    The high quenching efficiency of metal nanoparticles has facilitated its use as quenchers in molecular beacons. To optimize this system, a good understanding of the many factors that influence molecular beacon performance is required. In this study, molecular beacon performance was evaluated as a function of gold nanoparticle size and its immobilization characteristics. Gold nanoparticles of 4 nm, 15 nm and 87 nm diameter, were immobilized onto glass slides. Each size regime offered distinctive optical properties for fluorescence quenching of molecular dyes that were conjugated to oligonucleotides that were immobilized to the gold nanoparticles. Rigid double stranded DNA was used as a model to place fluorophores at different distances from the gold nanoparticles. The effect of particle size and also the immobilization density of nanoparticles was evaluated. The 4 nm and 87 nm gold nanoparticles offered the highest sensitivity in terms of the change in fluorescence intensity as a function of distance (3-fold improvement for Cy5). The optical properties of the molecular fluorophore was of significance, with Cy5 offering higher contrast ratios than Cy3 due to the red-shifted emission spectrum relative to the plasmon peak. A high density of gold nanoparticles reduced contrast ratios, indicating preference for a monolayer of immobilized nanoparticles when considering analytical performance. Molecular beacon probes were then used in place of the double stranded oligonucleotides. There was a strong dependence of molecular beacon performance on the length of a linker used for attachment to the nanoparticle surface. The optimal optical performance was obtained with 4 nm gold nanoparticles that were immobilized as monolayers of low density (5.7×10(11)particles cm(-2)) on glass surfaces. These nanoparticle surfaces offered a 2-fold improvement in analytical performance of the molecular beacons when compared to other nanoparticle sizes investigated. The principles developed

  16. Shape and surface effects on the cytotoxicity of nanoparticles: Gold nanospheres versus gold nanostars.

    PubMed

    Favi, Pelagie Marlene; Gao, Ming; Johana Sepúlveda Arango, Liuda; Ospina, Sandra Patricia; Morales, Mariana; Pavon, Juan Jose; Webster, Thomas Jay

    2015-11-01

    Gold nanoparticles are materials with unique optical properties that have made them very attractive for numerous biomedical applications. With the increasing discovery of techniques to synthesize novel nanoparticles such as star-shaped gold nanoparticles for biomedical applications, the safety and performance of these new nanomaterials must be systematically assessed before use. In this study, gold nanostars (AuNSTs) with multibranched surface structures were synthesized, and their influence on the cytotoxicity of human skin fibroblasts and rat fat pad endothelial cells (RFPECs) were assessed and compared with that of gold nanospheres (AuNSPs) with unbranched surfaces. Results showed that the AuNSPs with diameters of approximately 61.46 nm showed greater toxicity with fibroblast cells and RFPECs compared with the synthesized AuNSTs with diameters of approximately 33.69 nm. The AuNSPs were lethal at concentrations of 40 μg/mL for both cell lines, whereas the AuNSTs were less toxic at higher concentrations (400 μg/mL). The calculated IC50 (50% inhibitory concentration) values of the AuNSPs exposed to fibroblast cells were greater at 1 and 4 days of culture (26.4 and 27.7 μg/mL, respectively) compared with the RFPECs (13.6 and 13.8 μg/mL, respectively), indicating that the AuNSPs have a greater toxicity to endothelial cells. It was proposed that possible factors that could be promoting the reduced toxicity effects of the AuNSTs to fibroblast cells and RFPECs, compared with the AuNSPs may be size, surface chemistry, and shape of the gold nanoparticles. The reduced cell toxicity observed with the AuNSTs suggests that AuNSTs may be a promising material for use in biomedical applications. PMID:25904210

  17. Shape and surface effects on the cytotoxicity of nanoparticles: Gold nanospheres versus gold nanostars.

    PubMed

    Favi, Pelagie Marlene; Gao, Ming; Johana Sepúlveda Arango, Liuda; Ospina, Sandra Patricia; Morales, Mariana; Pavon, Juan Jose; Webster, Thomas Jay

    2015-11-01

    Gold nanoparticles are materials with unique optical properties that have made them very attractive for numerous biomedical applications. With the increasing discovery of techniques to synthesize novel nanoparticles such as star-shaped gold nanoparticles for biomedical applications, the safety and performance of these new nanomaterials must be systematically assessed before use. In this study, gold nanostars (AuNSTs) with multibranched surface structures were synthesized, and their influence on the cytotoxicity of human skin fibroblasts and rat fat pad endothelial cells (RFPECs) were assessed and compared with that of gold nanospheres (AuNSPs) with unbranched surfaces. Results showed that the AuNSPs with diameters of approximately 61.46 nm showed greater toxicity with fibroblast cells and RFPECs compared with the synthesized AuNSTs with diameters of approximately 33.69 nm. The AuNSPs were lethal at concentrations of 40 μg/mL for both cell lines, whereas the AuNSTs were less toxic at higher concentrations (400 μg/mL). The calculated IC50 (50% inhibitory concentration) values of the AuNSPs exposed to fibroblast cells were greater at 1 and 4 days of culture (26.4 and 27.7 μg/mL, respectively) compared with the RFPECs (13.6 and 13.8 μg/mL, respectively), indicating that the AuNSPs have a greater toxicity to endothelial cells. It was proposed that possible factors that could be promoting the reduced toxicity effects of the AuNSTs to fibroblast cells and RFPECs, compared with the AuNSPs may be size, surface chemistry, and shape of the gold nanoparticles. The reduced cell toxicity observed with the AuNSTs suggests that AuNSTs may be a promising material for use in biomedical applications.

  18. Shape and surface structure of gold nanoparticles under oxidizing conditions

    NASA Astrophysics Data System (ADS)

    Shi, Hongqing; Stampfl, Catherine

    2008-03-01

    We perform density-functional theory calculations to investigate the adsorption of oxygen at the Au(100) and Au(110) surfaces. For the clean surfaces, we find that the added-row (5×1)/Au(100) structure is more stable than the unreconstructed (1×1)/Au(100) surface and the missing-row (2×1)/Au(110) structure is more stable than the unreconstructed (1×1)/Au(110) surface, which is consistent with experimental results. For oxygen adsorption on Au(100), the most stable structure is predicted to be a low coverage ( ˜0.1 ML) on the added-row reconstructed surface, while for adsorption on Au(110), the most stable configuration of those considered is a (2×1) missing-row structure with 1 ML coverage of oxygen. From these results, together with those of our previous investigations into the O/Au(111) system, we use the Wulff construction to predict the nanoparticle shape as a function of oxygen chemical potential, which we correlate with pressure (p) and temperature (T) . For low values of the oxygen chemical potential ( <-0.6eV , corresponding, e.g., to p=1atm and T>600K ), the nanoparticle consists of clean (111) facets. For slightly higher values, clean (111) facets still dominate but there are small regions of (110) facets, which are covered with the (2×1)-2O reconstruction. With progressively increasing values of the chemical potential (e.g., from -0.4to-0.18eV , corresponding to, e.g., p=1atm and T=420-200K ), the (111) facets become covered with a thin oxide-like structure, and the (110) regions with the (2×1)-2O/(110) surface reconstruction become larger and finally dominate. These findings indicate that for low temperature oxidation reactions, where gold nanoparticles have been reported to be surprisingly active, such thin “surface-oxide-like” structures on the (111) and (110) surfaces could possibly play a role in the behavior of the nanogold catalysts.

  19. Surface functionalities of gold nanoparticles impact embryonic gene expression responses

    PubMed Central

    Truong, Lisa; Tilton, Susan C.; Zaikova, Tatiana; Richman, Erik; Waters, Katrina M.; Hutchison, James E.; Tanguay, Robert L.

    2012-01-01

    Incorporation of gold nanoparticles (AuNPs) into consumer products is increasing; however, there is a gap in available toxicological data to determine the safety of AuNPs. In this study, we utilised the embryonic zebrafish to investigate how surface functionalisation and charge influence molecular responses. Precisely engineered AuNPs with 1.5 nm cores were synthesised and functionalized with three ligands: 2-mercaptoethanesulfonic acid (MES), N,N,N-trimethylammoniumethanethiol (TMAT), or 2-(2-(2-mercaptoethoxy)ethoxy)ethanol. Developmental assessments revealed differential biological responses when embryos were exposed to the functionalised AuNPs at the same concentration. Using inductively coupled plasma–mass spectrometry, AuNP uptake was confirmed in exposed embryos. Following exposure to MES- and TMAT-AuNPs from 6 to 24 or 6 to 48 h post fertilisation, pathways involved in inflammation and immune response were perturbed. Additionally, transport mechanisms were misregulated after exposure to TMAT and MES-AuNPs, demonstrating that surface functionalisation influences many molecular pathways. PMID:22263968

  20. Surface chemistry-mediated penetration and gold nanorod thermotherapy in multicellular tumor spheroids.

    PubMed

    Jin, Shubin; Ma, Xiaowei; Ma, Huili; Zheng, Kaiyuan; Liu, Juan; Hou, Shuai; Meng, Jie; Wang, Paul C; Wu, Xiaochun; Liang, Xing-Jie

    2013-01-01

    We investigated the penetration and thermotherapy efficiency of different surface coated gold nanorods (Au NRs) in multicellular tumor spheroids. The current data show that negatively charged Au NRs, other than positively charged Au NRs, can penetrate deep into the tumor spheroids and achieve a significant thermal therapeutic benefit.

  1. Assessment of modified gold surfaced titanium implants on skeletal fixation.

    PubMed

    Zainali, Kasra; Danscher, Gorm; Jakobsen, Thomas; Baas, Jorgen; Møller, Per; Bechtold, Joan E; Soballe, Kjeld

    2013-01-01

    Noncemented implants are the primary choice for younger patients undergoing total hip replacements. However, the major concern in this group of patients regarding revision is the concern from wear particles, periimplant inflammation, and subsequently aseptic implant loosening. Macrophages have been shown to liberate gold ions through the process termed dissolucytosis. Furthermore, gold ions are known to act in an anti-inflammatory manner by inhibiting cellular NF-κB-DNA binding. The present study investigated whether partial coating of titanium implants could augment early osseointegration and increase mechanical fixation. Cylindrical porous coated Ti-6Al-4V implants partially coated with metallic gold were inserted in the proximal region of the humerus in ten canines and control implants without gold were inserted in contralateral humerus. Observation time was 4 weeks. Biomechanical push out tests and stereological histomorphometrical analyses showed no statistically significant differences in the two groups. The unchanged parameters are considered an improvement of the coating properties, as a previous complete gold-coated implant showed inferior mechanical fixation and reduced osseointegration compared to control titanium implants in a similar model. Since sufficient early mechanical fixation is achieved with this new coating, it is reasonable to investigate the implant further in long-term studies. PMID:22847873

  2. Surface modified gold nanowires for mammalian cell transfection

    NASA Astrophysics Data System (ADS)

    Kuo, Chiung-Wen; Lai, Jun-Jung; Wei, Kung Hwa; Chen, Peilin

    2008-01-01

    Aminothiol modified gold nanowires have been used as vectors for the delivery of plasmid DNA into two different types of mammalian cells: 3T3 and HeLa. It was measured that positively charged gold nanowires with a diameter of 200 nm and a length around 5 µm were capable of carrying 1 pg of plasmid DNA per nanowire into cells. Compared with other transfection reagents, the gold nanowires exhibited the highest transfection efficiency while almost no cytotoxicity was observed. In addition, it has been shown that individual nanowires can be visualized with sub-micrometer resolution, which may allow the use of functionalized multi-segment nanowires as local probes for the investigation of the microenvironment inside cells.

  3. Surface Plasmon-Driven Water Reduction: Gold Nanoparticle Size Matters

    SciTech Connect

    Qian, Kun; Sweeny, Brendan C.; Johnston-Peck, Aaron C.; Niu, Wenxin; Graham, Jeremy O.; DuChene, Joseph S.; Qiu, Jingjing; Wang, Yi-Chung; Engelhard, Mark H.; Su, Dong; Stach, Eric A.; Wei, Wei

    2014-07-16

    Water reduction under two visible light ranges (λ > 400 and λ > 435 nm) was investigated using gold-loaded titanium dioxide (Au-TiO2) with different sizes of Au nanoparticles (NPs). Two different mechanisms have been determined to clarify the specific role of Au NPs in visible light-induced photocatalytic reactions. Our study provides solid evidences showing that Au NPs sizes are essential for the surface plasmon-driven water reduction under λ > 435 nm. More specifically, we have demonstrated that the Au NPs sizes are vital for the SPR mediated electron transfer efficiency and play a critical role in determining the reduction potential of the transferred electrons in the TiO2 conduction band (CB) and their following activities. Our discovery provides a facile way to manipulate the reduction potential of transferred electrons by simply varying the Au NPs sizes, which will greatly facilitate the design of suitable plasmonic photocatalysts for water reduction and other valuable solar-to-fuel reactions.

  4. Influence of ultrathin water layer on the van der Waals/Casimir force between gold surfaces

    SciTech Connect

    Palasantzas, G.; Zwol, P. J. van; Svetovoy, V. B.

    2009-06-15

    In this paper we investigate the influence of ultrathin water layer ({approx}1-1.5 nm) on the van der Waals/Casimir force between gold surfaces. Adsorbed water is inevitably present on gold surfaces at ambient conditions as jump-up-to contact during adhesion experiments demonstrate. Calculations based on the Lifshitz theory give very good agreement with the experiment in the absence of any water layer for surface separations d > or approx. 10 nm. However, a layer of thickness h < or approx. 1.5 nm is allowed by the error margin in force measurements. At shorter separations, d < or approx. 10 nm, the water layer can have a strong influence as calculations show for flat surfaces. Nonetheless, in reality the influence of surface roughness must also be considered, and it can overshadow any water layer influence at separations comparable to the total sphere-plate rms roughness w{sub shp}+w.

  5. Surface charge of gold nanoparticles mediates mechanism of toxicity

    NASA Astrophysics Data System (ADS)

    Schaeublin, Nicole M.; Braydich-Stolle, Laura K.; Schrand, Amanda M.; Miller, John M.; Hutchison, Jim; Schlager, John J.; Hussain, Saber M.

    2011-02-01

    Recently gold nanoparticles (Au NPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their biocompatibility in the event that they come into contact with a biological system. In the present study, we have investigated whether modulating the surface charge of 1.5 nm Au NPs induced changes in cellular morphology, mitochondrial function, mitochondrial membrane potential (MMP), intracellular calcium levels, DNA damage-related gene expression, and of p53 and caspase-3 expression levels after exposure in a human keratinocyte cell line (HaCaT). The evaluation of three different Au NPs (positively charged, neutral, and negatively charged) showed that cell morphology was disrupted by all three NPs and that they demonstrated a dose-dependent toxicity; the charged Au NPs displayed toxicity as low as 10 µg ml-1 and the neutral at 25 µg ml-1. Furthermore, there was significant mitochondrial stress (decreases in MMP and intracellular Ca2+ levels) following exposure to the charged Au NPs, but not the neutral Au NPs. In addition to the differences observed in the MMP and Ca2+ levels, up or down regulation of DNA damage related gene expression suggested a differential cell death mechanism based on whether or not the Au NPs were charged or neutral. Additionally, increased nuclear localization of p53 and caspase-3 expression was observed in cells exposed to the charged Au NPs, while the neutral Au NPs caused an increase in both nuclear and cytoplasmic p53 expression. In conclusion, these results indicate that surface charge is a major determinant of how Au NPs impact cellular processes, with the charged NPs inducing cell death through apoptosis and neutral NPs leading to necrosis.Recently gold nanoparticles (Au NPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their biocompatibility in the

  6. Selective Deposition of Gold Particles on Dip-Pen Nanolithography Patterns on Silicon Dioxide Surfaces

    NASA Astrophysics Data System (ADS)

    Sheu, Jeng‑Tzong; Wu, Chia‑Hao; Chao, Tieng‑Sheng

    2006-04-01

    We report a novel platform to perform selective deposition of gold nanoparticles on dip-pen nanolithographic patterns on SiO2 surfaces. An “inked” atomic force microscope (AFM) tip was adopted to deposit 2.2 mM organic N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS) molecules in nanopatterns through a water meniscus onto a SiO2 substrate under ambient conditions; the molecules act as linkers for the selective deposition of gold nanoparticles on the SiO2 surface. Conditions for dip-pen nanolithography of organic nanopatterns of AEAPTMS were investigated. In addition, gold nano-particles with negatively-charged citrate surfaces were deposited selectively on top of the organic patterns. X-ray photoelectron spectroscopy was then used to evaluate the presence of gold nanoparticles on the SiO2 surface. Lateral force microscopy was utilized to differentiate the surface between oxidized semiconductors and patterned areas with monolayer of AEAPTMS. Linewidths down to 60 nm have been successfully achieved by this method.

  7. Adsorption of vapreotide on gold colloids studied by surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Gómez, J. A.; Cabanzo, R.; Mejia Ospino, E.

    2016-02-01

    Surface Enhanced Raman Spectroscopy (SERS) has been used to investigate the somatostatin (SST) analogue Vapreotide (VAP) in gold colloids. The optimum conditions to detect SERS signals of VAP have been studied. The observed SERS bands correspond to different vibrational modes of the peptide; being the most dominant SERS signals the ones derived from the aromatic amino acids Tryptophan (Trp), Phenylalanine (Phe) and Tyrosine (Tyr). Changes in enhancement and wavenumber of the proper bands upon adsorption on gold colloid are consistent with VAP adsorption, primarily through Tryptophan residues.

  8. 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.

  9. Critical role of surface hydration on the dynamics of serum adsorption studied with monoethylene glycol adlayers on gold.

    PubMed

    Avci, Ceren; Sheikh, Sonia; Blaszykowski, Christophe; Thompson, Michael

    2013-01-18

    The dynamics of serum adsorption on bare and monoethylene glycol adlayer-modified gold surfaces is investigated using acoustic wave physics. Hydration experiments support the pivotal role ascribed to water in the antifouling of surfaces. Behavioural discrepancy is interpreted in terms of difference in water structuring properties (surface kosmotropicity).

  10. Toward spatial control of gold nanorod surface functionalization

    NASA Astrophysics Data System (ADS)

    Eller, Jonathan R.

    Gold nanorods (GNRs) show much promise for applications in biological, optoelectronic and energy applications. The resonant generation of a localized surface plasmon resonance (LSPR) at the GNR surface results in interesting optical properties and unique interactions with molecules. Combined with their biocompatibility, ease of synthesis and facile surface functionalization, these anisotropic metal particles are excellent scaffolds for the study of the interactions between nanoscale surfaces and their chemical/biological environments. Regardless of the application, however, GNR utility will not be fully realized until the chemical nature of the surface is understood and controlled. GNRs can enhance various photophysical properties of molecules. In the case of two-photon absorption (TPA), cross-section enhancements have been shown to increase with strong distance-dependence. Here, a dual approach for the conjugation of a TPA chromophore to GNRs is presented, relying on layer-by- layer (LbL) polymer wrapping and direct thiol coating of the same parent chromophore structure. Together, these approaches allow for estimated chromophore-particle distances from <1nm to more than 15 nm. Composites were confirmed using conventional nanoparticle characterization methods. Imaging of GNR polymer shells indicated anisotropic composite structures, as confirmed by both conventional and cryo-TEM. Optical characterizations were performed using two-photon excited fluorescence and Z-scan techniques, to probe the TPA enhancement. The intrinsic nonlinear optical properties of GNRs is shown to contribute strongly to these measurements, suggesting the utility of these materials for bi-modal imaging platforms. GNR properties, like their shape, are anisotropic. The LSPR-induced near- fields are heterogeneously distributed on the nanorod surface, with the tips being much "hotter" than the sides. To understand and utilize fully the spatially- dependent interactions of GNRs with their

  11. Ultraviolet Photostability of Adenine on Gold and Silicon Surfaces

    NASA Astrophysics Data System (ADS)

    Mateo-Martí, Eva; Pradier, Claire-Marie; Martín-Gago, Jose-Angel

    2009-08-01

    The adenine molecule is a DNA nucleobase, an essential component of genetic material. Because of the important role of DNA nucleobases in terrestrial biochemistry, we have studied the molecular adsorption, orientation, and chemical binding of adenine on metallic and semiconducting surfaces, such as gold and silicon, respectively, and their stability toward ultraviolet radiation by X-ray photoelectron spectroscopy (XPS) and reflection absorption infrared spectroscopy (RAIRS) techniques. We have exposed the adenine surface system to UV radiation (200-400 nm) under a high-vacuum environment (10-7 mbar) to study the photostability and photochemistry of adenine on different surfaces. After 10 or 24 hours of exposure under interplanetary space conditions, UV radiation induces desorption and partial dissociation of the molecule, which is dependant on the nature of the surface. The electronic excitations, induced in the material by UV absorption, play a major role in the photodestruction of the absorbed molecules on the solid surfaces.

  12. Adsorption and surface-enhanced Raman of dyes on silver and gold sols

    SciTech Connect

    Lee, P.C.; Meisel, D.

    1982-08-19

    Several negatively charged dyes were investigated for their possible adsorption on the surface of silver and gold colloidal particles. Those dyes that were found to adsorb on the particles were then checked for surface enhancement of Raman scattering. Highly efficient surface-enhanced Raman scattering (SERS) was observed from a carbocyanine dye in both sols. Excitation-dependence studies as well as adsorption studies confirm the SERS nature of the Raman spectra obtained. The dye is probably aggregated on adsorption and is probably attached through the naphthalene side moiety to the surface. Less efficient SERS was also observed for copper phthalocyanine.

  13. Gold

    USGS Publications Warehouse

    Kirkemo, Harold; Newman, William L.; Ashley, Roger P.

    1998-01-01

    Through the ages, men and women have cherished gold, and many have had a compelling desire to amass great quantities of it -- so compelling a desire, in fact, that the frantic need to seek and hoard gold has been aptly named "gold fever." Gold was among the first metals to be mined because it commonly occurs in its native form -- that is, not combined with other elements -- because it is beautiful and imperishable, and because exquisite objects can be made from it.

  14. Surface Plasmon's Dispersion Properties of Porous Gold Films.

    PubMed

    Stetsenko, M O; Maksimenko, L S; Rudenko, S P; Krishchenko, I M; Korchovyi, A A; Kryvyi, S B; Kaganovich, E B; Serdega, B K

    2016-12-01

    Nanostructure porous films with arrays of gold nanoparticles (Au NPs) have been produced by pulsed laser deposition. Dispersion properties of surface plasmons have been studied by the modulation-polarization spectroscopy technique. The dispersion relations for radiative modes and two types of non-radiative modes of localized and propagating surface plasmons were obtained. The branches of propagating modes were characterized by negative group velocity caused by spatial dispersion of dielectric function. The propagating modes are caused by dipole-dipole interactions between adjacent Au NPs. The frequencies and relaxation parameters of surface plasmon resonances and the plasma frequencies for Αu NPs were obtained. The relation between the surface plasmon's properties and formation conditions of films with arrays of Αu NPs is discussed. PMID:26925864

  15. Surface-modified gold nanorods for specific cell targeting

    NASA Astrophysics Data System (ADS)

    Wang, Chan-Ung; Arai, Yoshie; Kim, Insun; Jang, Wonhee; Lee, Seonghyun; Hafner, Jason H.; Jeoung, Eunhee; Jung, Deokho; Kwon, Youngeun

    2012-05-01

    Gold nanoparticles (GNPs) have unique properties that make them highly attractive materials for developing functional reagents for various biomedical applications including photothermal therapy, targeted drug delivery, and molecular imaging. For in vivo applications, GNPs need to be prepared with very little or negligible cytotoxicitiy. Most GNPs are, however, prepared using growth-directing surfactants such as cetyl trimethylammonium bromide (CTAB), which are known to have considerable cytotoxicity. In this paper, we describe an approach to remove CTAB to a non-toxic concentration. We optimized the conditions for surface modification with methoxypolyethylene glycol thiol (mPEG), which replaced CTAB and formed a protective layer on the surface of gold nanorods (GNRs). The cytotoxicities of pristine and surface-modified GNRs were measured in primary human umbilical vein endothelial cells and human cell lines derived from hepatic carcinoma cells, embryonic kidney cells, and thyroid papillary carcinoma cells. Cytotoxicity assays revealed that treating cells with GNRs did not significantly affect cell viability except for thyroid papillary carcinoma cells. Thyroid cancer cells were more susceptible to residual CTAB, so CTAB had to be further removed by dialysis in order to use GNRs for thyroid cell targeting. PEGylated GNRs are further modified to present monoclonal antibodies that recognize a specific surface marker, Na-I symporter, for thyroid cells. Antibody-conjugated GNRs specifically targeted human thyroid cells in vitro.

  16. Comparative hyperthermia effects of silica-gold nanoshells with different surface coverage of gold clusters on epithelial tumor cells.

    PubMed

    Park, Sang-Eun; Lee, Jaewon; Lee, Taeksu; Bae, Saet-Byeol; Kang, Byunghoon; Huh, Yong-Min; Lee, Sang-Wha; Haam, Seungjoo

    2015-01-01

    Silica-gold nanoshell (SGNS), which is a silica core surrounded by a gold layer, was synthesized by seed-mediated coalescence of gold clusters in an electroless plating solution. SGNS variations with different surface coverage of gold clusters were prepared by adjusting the amounts of gold salts in the presence of formaldehyde-reducing agents. Fully covered SGNS (f-SGNS) with connected gold clusters exhibited stronger intensity and more redshift of plasmon bands located around 820 nm than those of partially covered SGNS (p-SGNS) with disconnected gold clusters. Upon irradiation with near-infrared light (30 W/cm(2), 700-800 nm), f-SGNS caused a larger hyperthermia effect, generating a large temperature change (ΔT =42°C), as compared to the relatively small temperature change (ΔT =24°C) caused by p-SGNS. The therapeutic antibody, Erbitux™ (ERB), was further conjugated to SGNS for specific tumor cell targeting. The f-ERB-SGNS showed excellent therapeutic efficacy based on the combined effect of both the therapeutic antibody and the full hyperthermia dose under near-infrared irradiation. Thus, SGNS with well-controlled surface morphology of gold shells may be applicable for near-infrared-induced hyperthermia therapy with tunable optical properties. PMID:26425093

  17. Comparative hyperthermia effects of silica–gold nanoshells with different surface coverage of gold clusters on epithelial tumor cells

    PubMed Central

    Park, Sang-Eun; Lee, Jaewon; Lee, Taeksu; Bae, Saet-Byeol; Kang, Byunghoon; Huh, Yong-Min; Lee, Sang-Wha; Haam, Seungjoo

    2015-01-01

    Silica–gold nanoshell (SGNS), which is a silica core surrounded by a gold layer, was synthesized by seed-mediated coalescence of gold clusters in an electroless plating solution. SGNS variations with different surface coverage of gold clusters were prepared by adjusting the amounts of gold salts in the presence of formaldehyde-reducing agents. Fully covered SGNS (f-SGNS) with connected gold clusters exhibited stronger intensity and more redshift of plasmon bands located around 820 nm than those of partially covered SGNS (p-SGNS) with disconnected gold clusters. Upon irradiation with near-infrared light (30 W/cm2, 700–800 nm), f-SGNS caused a larger hyperthermia effect, generating a large temperature change (ΔT =42°C), as compared to the relatively small temperature change (ΔT =24°C) caused by p-SGNS. The therapeutic antibody, Erbitux™ (ERB), was further conjugated to SGNS for specific tumor cell targeting. The f-ERB-SGNS showed excellent therapeutic efficacy based on the combined effect of both the therapeutic antibody and the full hyperthermia dose under near-infrared irradiation. Thus, SGNS with well-controlled surface morphology of gold shells may be applicable for near-infrared-induced hyperthermia therapy with tunable optical properties. PMID:26425093

  18. Morphology modification of gold nanoparticles from nanoshell to C-shape: Improved surface enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Xing, Ting-Yang; Zhu, Jian; Li, Jian-Jun; Zhao, Jun-Wu

    2016-06-01

    Morphology modification of nanostructures is of great interest, because it can be used to fabricate nanostructures which are hard to be done using other methods. Different from traditional lithographic technique which is slow and expensive, morphology modification is easy, cheap, and reproducible. In this paper, modification of the optical and morphological properties of a hollow gold nanoshell (HGNS) is achieved by using H2O2 as an oxidizer. The reshaping of these nanostructures has been demonstrated as a consequence of an oxidation process in which HGNSs are dissolved by H2O2 under the acidic conditions provided by HCl. We investigate the oxidation process by a transmission electron microscope and propose a reshaping model involving four different shapes (HGNS, HGNS with hole, gold nanoring, and C-shaped gold nanoparticle) which are corresponding to the oxidation products of HGNSs at different pH values. Besides, the surface enhanced Raman scattering (SERS) activity of each oxidation product has been evaluated by using rhodamine 6G as the Raman active probe. It has been observed that the C-shaped gold nanoparticles which are corresponding to the oxidation products at the minimum pH value have the highest SERS activity and this result can also be interpreted by discrete-dipole approximation simulations. We demonstrate that the morphology modification of HGNSs becomes possible in a controlled manner using wet chemistry and can be used in preparation of gold nanoparticles such as HGNS with hole, gold nanoring, and C-shaped gold nanoparticle with large SERS activity. These nanostructures must have potential use in many plasmonic areas, including sensing, catalysis, and biomedicine.

  19. Surface-Enhanced Raman Spectroscopy of Polyelectrolyte-Wrapped Gold Nanoparticles in Colloidal Suspension

    PubMed Central

    Sivapalan, Sean T.; DeVetter, Brent M.; Yang, Timothy K.; Schulmerich, Matthew V.; Bhargava, Rohit; Murphy, Catherine J.

    2013-01-01

    The rapidly expanding field of surface-enhanced Raman spectroscopy (SERS) has helped fuel an intense interest in noble metal nanoparticle synthesis. An in-suspension approach for quantifying SERS enhancement and relating that enhancement to a spontaneous Raman equivalent signal is described. Gold nanoparticles of various shapes were wrapped with polyelectrolyte multilayers that trapped Raman reporter molecules at defined distances from the metal core. Electrospray ionization liquid chromatography mass spectrometry (ESI-LC-MS) on digested samples was employed to measure the average number of bound Raman reporter molecules per gold nanoparticle, and inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the average number of gold atoms per nanoparticle. Using these data, SERS signal intensity was compared to a spontaneous Raman calibration curve to compute a spontaneous Raman equivalent factor. Three different geometries of gold nanoparticles (cubes, spheres, and trisoctahedra) were synthesized to investigate edge and corner effects using these quantitative techniques. Finite element method (FEM) electromagnetic simulations examined the relationship between the different geometries and the observed SERS signal intensities. The experimental observations and theoretical results indicate that cubic gold nanoparticles have the highest effective signal. PMID:24224064

  20. 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

  1. Observation of surface states on gold films by electron tunneling spectroscopy

    NASA Technical Reports Server (NTRS)

    Lambe, J.; Thakoor, A. P.; Khanna, S. K.

    1984-01-01

    It is pointed out that inelastic electron tunneling spectroscopy (IETS) is a useful technique for the study of vibrational modes of molecules adsorbed on the surface of the insulating layer in a metal-insulator-metal tunnel junction. A detailed study of electron tunneling in aluminum-aluminum oxide-gold (Al-Al2O3-Au) tunnel junctions has been conducted with an overall goal of exploring possible mechanisms in such a thin film device useful for chemical sensing. For an understanding of the electronic effects in the presence of chemicals in a junction, the electronic surface properties of the metallic films in a clean tunnel junction must be established. The present investigation is concerned with room temperature observations of electronic states on the surface of highly oriented gold film in Al-Al2O3-Au junctions.

  2. Surface chemistry-mediated penetration and gold nanorod thermotherapy in multicellular tumor spheroids

    NASA Astrophysics Data System (ADS)

    Jin, Shubin; Ma, Xiaowei; Ma, Huili; Zheng, Kaiyuan; Liu, Juan; Hou, Shuai; Meng, Jie; Wang, Paul C.; Wu, Xiaochun; Liang, Xing-Jie

    2012-12-01

    We investigated the penetration and thermotherapy efficiency of different surface coated gold nanorods (Au NRs) in multicellular tumor spheroids. The current data show that negatively charged Au NRs, other than positively charged Au NRs, can penetrate deep into the tumor spheroids and achieve a significant thermal therapeutic benefit.We investigated the penetration and thermotherapy efficiency of different surface coated gold nanorods (Au NRs) in multicellular tumor spheroids. The current data show that negatively charged Au NRs, other than positively charged Au NRs, can penetrate deep into the tumor spheroids and achieve a significant thermal therapeutic benefit. Electronic supplementary information (ESI) available: Materials and methods section. See DOI: 10.1039/c2nr31877f

  3. Surface-enhanced Raman spectroscopic analysis of maleic hydrazide adsorbed on gold surface.

    PubMed

    Wang, Can; Gu, Huaimin; Lv, Meng; He, Ruoyu; Zhang, Juling

    2014-03-25

    In this paper, surface-enhanced Raman scattering (SERS) spectra of maleic hydrazide (MH, 6-hydroxy-3(2H)-pyridazinone) were studied by using citrate-reduced gold colloidal nanoparticles. Comparisons between the prominent SERS bands and the precise mode descriptions predicted through density functional theory (DFT) simulations at the B3LYP/6-311++g(d,p) level allowed an in-depth orientation analysis of the adsorbed species on gold surfaces. And main forms of hydrogen bonds in the solid state of MH were also determined to be O-H⋯O. Furthermore, the effects of concentration and pH on the SERS spectra of the molecule were discussed. It is found that with the different adsorbate concentration, the SERS spectra of MH show significant changes in their features, indicating different orientations and adsorption sites of the molecule on the gold colloidal surface. The SERS and absorption spectra under different pH conditions show that a basic environment leads to the deprotonation of N2 and the nearly parallel orientation of the MH molecule on the gold surface. Moreover, the enhanced characteristic bands were observed at MH concentrations down to about 1 ppm with the gold colloids, demonstrating a potential of the technique in the analysis of MH residues. PMID:24295778

  4. Surface Coating by Gold Nanoparticles on Functional Polymers: On-Demand Portable Catalysts for Suzuki Reactions.

    PubMed

    García-Calvo, José; García-Calvo, Víctor; Vallejos, Saúl; García, Félix C; Avella, Manuel; García, José-Miguel; Torroba, Tomás

    2016-09-28

    We have developed new functionalized polymers capable of being easily coated by gold nanoparticles, uniformly distributed on the surface of the polymers, by simply adding a gold(III) solution in water to the polymers. The polymer-supported gold nanoparticle material was used as an efficient portable and reusable catalyst for Suzuki reactions in mixed organic-aqueous solvents. PMID:27617785

  5. An investigation of the impedance properties of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Callaghan, Martina F.; Lund, Torben; Hashemzadeh, Parham; Roitt, Ivan M.; Bayford, Richard H.

    2010-04-01

    Over recent years there has been rapid growth in the research being carried out on nanoparticles. In the field of medical imaging, this interest has focussed primarily on the potential for drug delivery and using nanoparticles as a contrast agent, e.g. super-paramagnetic iron-oxide (SPIO) particles in MRI. More recently gold nanoparticles have been used in radiotherapy treatment of tumours to provide dose enhancement by increasing the efficacy of the radiation absorption. Nanoparticles coated with molecules such as glucose or cancer-specific antibodies can be directed towards specific cancer cells in vivo. Such targeting combined with the properties of nanoparticles shows great promise for localised therapy of tumours while leaving neighbouring healthy tissue unaffected. However, on the nanoparticle scale of sub-100nm the weighting of various factors and inter-atomic interactions which determine the bulk properties of a material changes. Many properties of the bulk material no longer hold. As such, each aspect of nanoparticle behaviour must be investigated afresh to explore the full extent of their potential. The property of nanoparticles we wish to explore and characterise is impedance. Bulk gold is well known to be highly conductive. If this were to remain the case on the nanoscale, it could be highly effective as a contrast agent for electrical impedance tomography, particularly when combined with tumour targeting.

  6. Surface plasma resonant effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Meen, Teen-Hang; Tsai, Jenn-Kai; Chao, Shi-Mian; Lin, Yu-Chien; Wu, Tien-Chuan; Chang, Tang-Yun; Ji, Liang-Wen; Water, Walter; Chen, Wen-Ray; Tang, I.-Tseng; Huang, Chien-Jung

    2013-10-01

    In this study, we prepared different shapes of gold nanoparticles by seed-mediated growth method and applied them on the photoelectrodes of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) effect of gold nanoparticles on the photoelectrodes of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy show that the average diameter of the spherical gold nanoparticles is 45 nm, the average length and width of the short gold nanorods were 55 and 22 nm, respectively, and the average length and width of the long gold nanorods were 55 and 14 nm, respectively. The aspect ratio of the short and long gold nanorods was about 2.5 and 4, respectively. The results of ultraviolet-visible absorption spectra show that the absorption wavelength is about 540 nm for spherical gold nanoparticles, and the absorption of the gold nanorods reveals two peaks. One is about 510 to 520 nm, and the other is about 670 and 710 nm for the short and long gold nanorods, respectively. The best conversion efficiency of the dye-sensitized solar cells with spherical gold nanoparticles and short and long gold nanorods added in is 6.77%, 7.08%, and 7.29%, respectively, and is higher than that of the cells without gold nanoparticles, which is 6.21%. This result indicates that the effect of gold nanoparticles on the photoelectrodes can increase the conductivity and reduce the recombination of charges in the photoelectrodes, resulting in the increase of conversion efficiency for DSSCs. In addition, the long gold nanorods have stronger SPR effect than the spherical gold nanoparticles and short gold nanorods at long wavelength. This may be the reason for the higher conversion efficiency of DSSCs with long gold nanorods than those of the cells with spherical gold nanoparticles and short gold nanorods.

  7. Single particle optical investigation of gold shell enhanced upconverted fluorescence emission

    NASA Astrophysics Data System (ADS)

    Green, Kory; Lim, Shuang Fang; Hallen, Hans

    2014-03-01

    Upconverting nanoparticles (UCNPs) excited in the near IR offer novel advantages as fluorescent contrast agents, allowing for background free bio-imaging. However, their fluorescence brightness is hampered by low quantum efficiency due to the low absorption cross section of Ytterbium and Erbium ions in the near IR. We enhance the efficiency of these particles by investigating the plasmonic coupling of 30nm diameter core NaYF4: Yb, Er upconverting particles (UCNPs) with a gold shell coating. An enhancement of green emission by a factor of five and a three times overall increase in emission intensity has been achieved for single particle spectra. UV-Vis absorption has confirmed the surface plasmon resonance (SPR) of the gold shell to the near IR and transmission electron microscope (TEM) images demonstrates successful growth of a gold shell around the upconversion particle. Time-resolved spectroscopy shows that gold shell coupling changes the lifetime of the energy levels of the Erbium ion that are relevant to the emission process.

  8. An in-vitro investigation of skin tissue soldering using gold nanoshells and diode laser.

    PubMed

    Nourbakhsh, Mohammad S; Khosroshahi, Mohammad E

    2011-01-01

    Gold-coated silica core nanoparticles have an optical response dictated by the plasmon resonance (PR). The wavelength at which the resonance occurs depends on the core and shell size, allowing nanoshells to be tailored for particular applications. The purpose of this study is to synthesize and use different concentrations of gold nanoshells as exogenous material for in-vitro skin tissue soldering and also to examine the effect of laser-soldering parameters on the properties of repaired skin. Two mixtures of albumin solder and different concentrations of gold nanoshells were prepared. A full-thickness incision of 2 × 20 mm(2) was made on the surface and after addition of mixtures it was irradiated by an 810-nm diode laser at different power densities. The changes of tensile strength σ(t) due to temperature rise, number of scan (N(s)), and scan velocity (V(s)) were investigated. The results showed at constant laser power density (I), σ(t) of repaired incisions increases by increasing the concentration of gold nanoshells, N(s) and decreasing V(s). It is therefore important to consider the trade-off between the scan velocity and the skin temperature for achieving an optimum operating condition. In our case, this corresponds to σ(t) = 1,610 g/cm(2) at I ∼ 60 Wcm(-2), T ∼ 65°C, Ns = 10 and Vs = 0.2 mms(-1). PMID:20623244

  9. Analysis of surface stains on modern gold coins

    NASA Astrophysics Data System (ADS)

    Corregidor, V.; Alves, L. C.; Cruz, J.

    2013-07-01

    It is a mandatory practice in the European Mint Houses to provide a certificate of guarantee of their products specially when issuing commemorative gold or silver coins. This practise should assure satisfaction and trust both for the mint house and for the demanding numismatic collector. For these reasons the Mint Houses follow a strict quality control in all the production steps in order to ensure a no-defect, fully supervised output. In spite of all the undertaken precautions, different surface stains with diverse origin on gold coins recently minted in Europe were observed. Those were compositionally studied by means of IBA techniques at the end-stage nuclear microprobe installed at IST/ITN. From this study it was possible to identify several possible sources for these stains. The presence of defects at the surface of these commemorative coins address the need of improving the quality control system and the results here presented point out where these improvements should occur, in order to reduce/eliminate them and give the customer a product that with time probably will be revalued.

  10. SURFACE COATING EFFECTS ON THE ASSEMBLY OF GOLD NANOSPHERES

    SciTech Connect

    Meyer, Kent A; Shuford, Kevin L; Whitten, William B; Shaw, Robert W

    2010-01-01

    Optical spectra and atomic force microscopy (AFM) images of individually selected spheres and mechanically assembled silica-coated gold nanosphere pairs were recorded. The 10-nm spacing of the spheres allowed discrete dipole approximation (DDA) computational simulations to provide a meaningful results regarding the dimers. Both the data and simulation indicate that the silica shell integrity was maintained throughout the assembly, so that the shell therefore served as a means of rigid control of the spacing between the metal cores. Optical perturbative effects due to the presence of the fused silica substrate were negligible. Experimental investigations regarding less rigid polyvinylpyrrolidone (PVP) coatings also were performed and some comparisons were made.

  11. Surface coating effects on the assembly of gold nanospheres.

    PubMed

    Meyer, Kent A; Polemi, Alessia; Shuford, Kevin L; Whitten, William B; Shaw, Robert W

    2010-10-15

    Optical spectra and atomic force microscopy (AFM) images of individually selected spheres and mechanically assembled silica-coated gold nanosphere pairs were recorded. The shell served as a means of rigid control of the minimum spacing between the metal cores. The spectra of the assembled spheres were simulated using classical electrodynamics. The observed spectra resulted in superior characterization of the particle assembly geometry, relative to the AFM data. Experimental investigations regarding less-rigid polyvinylpyrrolidone (PVP) sphere coatings were also performed and some comparisons were made.

  12. Attaching Thiolated Superconductor Grains on Gold Surfaces for Nanoelectronics Applications

    NASA Astrophysics Data System (ADS)

    De Los Santos Valladares, Luis; Bustamante Dominguez, Angel; Llandro, Justin; Suzuki, Seiichi; Mitrelias, Thanos; Bellido Quispe, Richard; Barnes, Crispin H. W.; Majima, Yutaka

    2010-09-01

    We report that the high critical temperature superconductor (HTCS) LaCaBaCu3O7 in the form of nanograins can be linked to Au(111) surfaces through self assembled monolayers (SAMs) of HS-C8H16-HS [octane (di)thiol]. We show that La1113 particles (100 nm mean diameter) can be functionalized by octane (di)thiol without affecting their superconducting critical temperature (TC=80 K). X-ray photoemission spectroscopy (XPS) analysis reveals that the thiol functional heads link the superconducting grain surfaces creating sulfonates and we deduce that bonding between the S atoms and Cu(1) atoms of the La1113 structure would be formed. We suggest a design for a superconducting transistor fabricated by immobilized La1113 nanograins in between two gold electrodes which could be controlled by an external magnetic field gate.

  13. 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

  14. Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

    NASA Astrophysics Data System (ADS)

    Sivakumar, Manickam; Venkatakrishnan, Krishnan; Tan, Bo

    2011-12-01

    In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The radiation fluence used was 0.5 J/cm2 at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200), (211), and (321) reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4 f and Si 2 p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure.

  15. Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

    PubMed Central

    2011-01-01

    In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The radiation fluence used was 0.5 J/cm2 at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200), (211), and (321) reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4f and Si 2p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure. PMID:21711595

  16. Synthesis of gold microstructures with surface nanoroughness using a deep eutectic solvent for catalytic and diagnostic applications.

    PubMed

    Oh, Ju-Hwan; Lee, Jae-Seung

    2014-05-01

    We synthesized highly monodisperse gold microparticles (AuMPs) using a deep eutectic solvent (DES) which composed of choline chloride and malonic acid as both a reaction medium and structure-directing agent. These microparticles exhibit distinctive surface nanoroughness and highly defined diameters that can be precisely controlled over a range of a few micrometers under different reductive conditions. The internal and external structures of the particles are thoroughly investigated by electron microscopy, which is further analyzed in association with their optical properties. We also investigate the gold microparticle concentration-dependent catalytic property employing a reductive reaction of 4-nitrophenol to 4-aminopenol as a model system. Importantly, the gold microparticles are densely functionalized with DNA and reversibly assemble with DNA-gold nanoparticle conjugate probes for the colorimetric detection of target DNA sequences, demonstrating that these novel structures can be utilized as platforms that quickly regulate the optical properties of plasmonic nanoparticles for diagnostic applications.

  17. Investigation of Hemoglobin/Gold Nanoparticle Heterolayer on Micro-Gap for Electrochemical Biosensor Application

    PubMed Central

    Lee, Taek; Kim, Tae-Hyung; Yoon, Jinho; Chung, Yong-Ho; Lee, Ji Young; Choi, Jeong-Woo

    2016-01-01

    In the present study, we fabricated a hemoglobin/gold nanoparticle (Hb/GNP) heterolayer immobilized on the Au micro-gap to confirm H2O2 detection with a signal-enhancement effect. The hemoglobin which contained the heme group catalyzed the reduction of H2O2. To facilitate the electron transfer between hemoglobin and Au micro-gap electrode, a gold nanoparticle was introduced. The Au micro-gap electrode that has gap size of 5 µm was fabricated by conventional photolithographic technique to locate working and counter electrodes oppositely in a single chip for the signal sensitivity and reliability. The hemoglobin was self-assembled onto the Au surface via chemical linker 6-mercaptohexanoic acid (6-MHA). Then, the gold nanoparticles were adsorbed onto hemoglobin/6-MHA heterolayers by the layer-by-layer (LbL) method. The fabrication of the Hb/GNP heterolayer was confirmed by atomic force microscopy (AFM) and surface-enhanced Raman spectroscopy (SERS). The redox property and H2O2 detection of Hb/GNP on the micro-gap electrode was investigated by a cyclic voltammetry (CV) experiment. Taken together, the present results show that the electrochemical signal-enhancement effect of a hemoglobin/nanoparticle heterolayer was well confirmed on the micro-scale electrode for biosensor applications. PMID:27171089

  18. Role of surface plasmon in second harmonic generation from gold nanorods

    SciTech Connect

    Hubert, C.; Billot, L.; Adam, P.-M.; Bachelot, R.; Royer, P.; Grand, J.; Gindre, D.; Dorkenoo, K. D.; Fort, A.

    2007-04-30

    The role of surface plasmon in second harmonic generation from arrays of gold nanorod particles excited by femtosecond laser pulses is investigated as a function of incident light polarization and irradiation wavelength. In addition to photoluminescence, a peak of second harmonic is observed and is found to depend on the polarization and wavelength of the fundamental frequency laser beam. In particular, the authors found similarities between extinction spectra of the nanoparticles and spectra of emmitted second harmonic. This behavior can be explained by resonant excitation of localized surface plasmon resonances.

  19. Gold nanoaggregates for probing single-living cell based on surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Lu, Peng; Wang, Jing; Lin, Jinyong; Lin, Juqiang; Liu, Nenrong; Huang, Zufang; Li, Buhong; Zeng, Haishan; Chen, Rong

    2015-05-01

    Gold nanoparticles are delivered into living cells by transient electroporation method to obtain intracellular surface-enhanced Raman spectroscopy (SERS). The subcellular localization of gold nanoparticles is characterized by transmission electron microscopy, and the forming large gold nanoaggregates are mostly found in the cytoplasm. The SERS detection of cells indicates that this kind of gold nanostructures induces a high signal enhancement of cellular chemical compositions, in addition to less cellular toxicity than that of silver nanoparticles. These results demonstrate that rapid incorporation of gold nanoparticles by electroporation into cells has great potential applications in the studies of cell biology and biomedicine.

  20. Sulfur-induced structural motifs on copper and gold surfaces

    NASA Astrophysics Data System (ADS)

    Walen, Holly

    The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. We choose very specific conditions: very low temperature (5 K), and very low sulfur coverage (≤ 0.1 monolayer). In this region of temperature-coverage space, which has not been examined previously for these adsorbate-metal systems, the effects of individual interactions between metals and sulfur are most apparent and can be assessed extensively with the aid of theory and modeling. Furthermore, at this temperature diffusion is minimal and relatively-mobile species can be isolated, and at low coverage the structures observed are not consumed by an extended reconstruction. The primary experimental technique is scanning tunneling microscopy (STM). The experimental observations presented here---made under identical conditions---together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.

  1. Orthogonal, three-component, alkanethiol-based surface-chemical gradients on gold.

    PubMed

    Beurer, Eva; Venkataraman, Nagaiyanallur V; Rossi, Antonella; Bachmann, Florian; Engeli, Roman; Spencer, Nicholas D

    2010-06-01

    An orthogonal surface-chemical gradient composed of self-assembled monolayers on gold has been prepared by successive, controlled immersions in orthogonal directions into dilute solutions of dodecanethiol and perfluorododecanethiol. The resulting two-component orthogonal gradient in surface coverage was backfilled with 11-mercaptoundecanol, leading to a two-directional, three-component surface-chemical gradient. Water and hexadecane show distinctly different wetting behaviors on the gradient surface because of the differences in the hydrophobic and oleophobic natures of the three different constituents. These results are correlated with the chemical composition maps of the surface obtained by X-ray photoelectron spectroscopy. The homogeneity and the ordering of the self-assembled monolayer were investigated by dynamic water contact angle measurements and polarization-modulation infrared reflection-absorption spectroscopy. PMID:20166727

  2. Orthogonal, three-component, alkanethiol-based surface-chemical gradients on gold.

    PubMed

    Beurer, Eva; Venkataraman, Nagaiyanallur V; Rossi, Antonella; Bachmann, Florian; Engeli, Roman; Spencer, Nicholas D

    2010-06-01

    An orthogonal surface-chemical gradient composed of self-assembled monolayers on gold has been prepared by successive, controlled immersions in orthogonal directions into dilute solutions of dodecanethiol and perfluorododecanethiol. The resulting two-component orthogonal gradient in surface coverage was backfilled with 11-mercaptoundecanol, leading to a two-directional, three-component surface-chemical gradient. Water and hexadecane show distinctly different wetting behaviors on the gradient surface because of the differences in the hydrophobic and oleophobic natures of the three different constituents. These results are correlated with the chemical composition maps of the surface obtained by X-ray photoelectron spectroscopy. The homogeneity and the ordering of the self-assembled monolayer were investigated by dynamic water contact angle measurements and polarization-modulation infrared reflection-absorption spectroscopy.

  3. Enhanced surface plasmon resonance by Au nanoparticles immobilized on a dielectric SiO2 layer on a gold surface.

    PubMed

    Jung, Jaeyeon; Na, Kyunga; Lee, Jonghwan; Kim, Ki-Woo; Hyun, Jinho

    2009-09-28

    This paper introduces strategies for enhancement of a surface plasmon resonance (SPR) signal by adopting colloidal gold nanoparticles (AuNPs) and a SiO(2) layer on a gold surface. AuNPs on SiO(2) on a gold surface were compared with an unmodified gold surface and a SiO(2) layer on a gold surface with no AuNPs attached. The modified surfaces showed significant changes in SPR signal when biomolecules were attached to the surface as compared with an unmodified gold surface. The detection limit of AuNPs immobilized on a SPR chip was 0.1 ng mL(-1) for the prostate-specific antigen (PSA), a cancer marker, as measured with a spectrophotometer. Considering that the conventional ELISA method can detect approximately 10 ng mL(-1) of PSA, the strategy described here is much more sensitive (approximately 100 fold). The enhanced shift of the absorption curve resulted from the coupling of the surface and particle plasmons by the SiO(2) layer and the AuNPs on the gold surface.

  4. Surface enhanced Raman scattering, antibacterial and antifungal active triangular gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Smitha, S. L.; Gopchandran, K. G.

    2013-02-01

    Shape controlled syntheses of gold nanoparticles have attracted a great deal of attention as their optical, electronic, magnetic and biological properties are strongly dependent on the size and shape of the particles. Here is a report on the surface enhanced Raman scattering (SERS) activity of Cinnamomum zeylanicum leaf broth reduced gold nanoparticles consisting of triangular and spherical like particles, using 2-aminothiophenol (2-ATP) and crystal violet (CV) as probe molecules. Nanoparticles prepared with a minimum leaf broth concentration, having a greater number of triangular like particles exhibit a SERS activity of the order of 107. The synthesized nanoparticles exhibit efficient antibacterial activity against the tested gram negative bacterium Escherichia coli and gram positive bacterium Staphylococcus aureus. Investigations on the antifungal activity of the synthesized nanoparticles against Aspergillus niger and Fusarium oxysporum positive is also discussed.

  5. Effect of Ti adhesive layer on individual gold nanodisk surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Debu, Desalegn Tadesse; Ghosh, Pijush; French, David; Bauman, Stephen; Herzog, Joseph B.

    We investigate localized surface plasmon resonance (SPR) of gold nanodisks of various diameter and height fabricated on extremely thin Ti adhesive layers. Dark field scattering measurements reveal significant dependence of SPR in the size nano structures and polarization of the light. Comparisons of peak resonance extracted from spectra using Gaussian fitting of different Ti adhesive layer thickness indicates significant red shifting and damping of the plasmon mode. Experimental results are supported by numerical simulation based on three dimensional finite element time domain analysis. From the simulation and experimental results we quantitatively developed optimized model equation of resonance mode of the nanodisks with respect to adhesive layer thickness and broadening effect of the line shape. Such optimized model is very helpful in guiding targeted nanofabrication such as gold nanodisk antennas or biosensors.

  6. Electrochemical preparation of silver and gold nanoparticles: Characterization by confocal and surface enhanced Raman microscopy

    NASA Astrophysics Data System (ADS)

    Plieth, W.; Dietz, H.; Anders, A.; Sandmann, G.; Meixner, A.; Weber, M.; Kneppe, H.

    2005-12-01

    Localized silver and gold nanoparticles, electrochemically prepared by means of the double-pulse technique, were investigated with respect to their optical and spectroscopic properties by scanning confocal microscopy combined with surface enhanced Raman spectroscopy (SERS) and subsequent comparison with the local image of scanning electron microscopy (SEM). Analogous to the silver cluster preparation technique, controlled electrodeposition of gold nanoparticles was demonstrated, varying size from 10 to 500 nm and particle density. The maximum SERS enhancement factors found in the measurements were: (i) 10 10 for silver particles and (ii) 10 8 for gold particles. The optical and spectroscopic data of the local nanoparticle structures investigated showed that SERS is a local phenomenon, because (i) only few particles are Raman active particles, (ii) strongest enhancements in SERS are obtained from particle agglomerates, (iii) typically the Raman radiation is emitted from irregular structures like the necks between two or more particles agglomerated. In the investigated range from 10 to 500 nm no significant influence of the particle size was observed.

  7. Gold cluster coatings enhancing Raman scattering from surfaces: Ink analysis and document identification

    NASA Astrophysics Data System (ADS)

    Luo, Zhixun; Smith, Jordan C.; Goff, Trevor M.; Adair, James H.; Castleman, A. W.

    2013-09-01

    Based on the method of laser-ablation in liquids (LAL) with a strategy of bubbling nitrogen through a custom-made chamber, we prepared chemically-pure gold clusters which were found to be metastable for an extensive period of time beyond months. A practical use of discrimination among different surfaces is demonstrated here by applying the gold clusters as surface coatings which result in surface-enhanced Raman scattering (SERS) due to the surface plasmon resonance (SPR). This technique identifies various documents from different printers/copiers and written with different pen-inks. The stable and additive-free gold clusters enable repetitive examinations without impurity interference.

  8. DFT study of cysteine adsorbtion on gold defect surfaces

    NASA Astrophysics Data System (ADS)

    Buimaga-Iarinca, Luiza; Tosa, Nicoleta

    2012-02-01

    The controlled self-assembly of functional molecular species on well defined surfaces is a promising approach toward the design of nanoscale architectures. By using this methodology, regular low-dimensional systems such as supramolecular clusters, chains, or nanoporous arrays can be fabricated. Small biological molecules such as amino acids represent an important class of building blocks that are of interest for molecular architecture on surfaces because they inherently qualify for molecular recognition and self-assembly. The interaction between amino acids and solid surfaces is decisive for the development of bioanalytical devices or biocompatible materials as well as for a fundamental understanding of protein-surface bonding. Their practical implementation often involves surface structural defects. We investigated the adsorbtion mechanism of the cysteine on Au(111) defect surfaces by means of crystal orbital overlap population (COOP) analysis and also the dependence of the COOP curves on the type of surface defects.

  9. Sequence and Temperature Influence on Kinetics of DNA Strand Displacement at Gold Electrode Surfaces.

    PubMed

    Biala, Katarzyna; Sedova, Ada; Flechsig, Gerd-Uwe

    2015-09-16

    Understanding complex contributions of surface environment to tethered nucleic acid sensing experiments has proven challenging, yet it is important because it is essential for interpretation and calibration of indispensable methods, such as microarrays. We investigate the effects of DNA sequence and solution temperature gradients on the kinetics of strand displacement at heated gold wire electrodes, and at gold disc electrodes in a heated solution. Addition of a terminal double mismatch (toehold) provides a reduction in strand displacement energy barriers sufficient to probe the secondary mechanisms involved in the hybridization process. In four different DNA capture probe sequences (relevant for the identification of genetically modified maize MON810), all but one revealed a high activation energy up to 200 kJ/mol during hybridization, that we attribute to displacement of protective strands by capture probes. Protective strands contain 4 to 5 mismatches to ease their displacement by the surface-confined probes at the gold electrodes. A low activation energy (30 kJ/mol) was observed for the sequence whose protective strand contained a toehold and one central mismatch, its kinetic curves displayed significantly different shapes, and we observed a reduced maximum signal intensity as compared to other sequences. These findings point to potential sequence-related contributions to oligonucleotide diffusion influencing kinetics. Additionally, for all sequences studied with heated wire electrodes, we observed a 23 K lower optimal hybridization temperature in comparison with disc electrodes in heated solution, and greatly reduced voltammetric signals after taking into account electrode surface area. We propose that thermodiffusion due to temperature gradients may influence both hybridization and strand displacement kinetics at heated microelectrodes, an explanation supported by computational fluid dynamics. DNA assays with surface-confined capture probes and temperature

  10. Geologic, geophysical, and in situ stress investigations in the vicinity of the Dining Car Chimney, Dining Car/Hybla gold tunnels, Nevada Test Site, with sections on geologica investigations, geophysical investigations, and in situ stress investigations

    USGS Publications Warehouse

    Townsend, D.R.; Baldwin, M.J.; Carroll, R.D.; Ellis, W.L.; Magner, J.E.

    1982-01-01

    The Hybla Gold experiment was conducted in the U12e.20 drifts of the E-tunnel complex beneath the surface of Rainier Mesa at the Nevada Test Site. Though the proximity of the Hybla Gold working point to the chimney of the Dining Car event was important to the experiment, the observable geologic effects from Dining Car on the Hybla Gold site were minor. Overburden above the working point is approximately 385 m (1,263 ft). The pre-Tertiary surface, probably quartzite, lies approximately 254 m (833 ft) below the working point. The drifts are mined in zeolitized ash-fall tuffs of tunnel bed 4, subunits K and J, all of Miocene age. The working point is in subunit 4J. Geologic structure in the region around the working point is not complex. The U12e.20 main drift follows the axis of a shallow depositional syncline. A northeast-dipping fault with displacement of approximately 3 m (10 ft) passes within 15.2 m (50 ft) of the Hybla Gold working point. Three faults of smaller displacement pass within 183-290 m (600-950 ft) of the working point, and are antithetic to the 3-m (10-ft) fault. Three exploratory holes were drilled to investigate the chimney of the nearby Dining Car event. Four horizontal holes were drilled during the construction of the U12e.20 drifts to investigate the geology of the Hybla Gold working point.

  11. Geometry and Surface Characteristics of Gold Nanoparticles Influence their Biodistribution and Uptake by Macrophages

    PubMed Central

    Arnida; Janát-Amsbury, M.M.; Ray, A.; Peterson, C. M.; Ghandehari, H.

    2010-01-01

    Spherical and rod-shaped gold nanoparticles with surface poly (ethylene glycol) (PEG) chains were characterized for size, shape, charge, poly dispersity and surface plasmon resonance. The nanoparticles were injected intravenously to 6–8 weeks old female nu/nu mice bearing orthotopic ovarian tumors and their biodistribution in vital organs was compared. Gold nanorods were taken up to a lesser extent by the liver, had longer circulation time in the blood, and higher accumulation in the tumors, compared with their spherical counterparts. The cellular uptake of PEGylated gold nanoparticles by a murine macrophage-like cell line as a function of geometry was examined. Compared to nanospheres, PEGylated gold nanorods were taken up to a lesser extent by macrophages. These studies point to the importance of gold nanoparticle geometry and surface properties on transport across biological barriers. PMID:21093587

  12. Role of nanostructured gold surfaces on monocyte activation and Staphylococcus epidermidis biofilm formation.

    PubMed

    Svensson, Sara; Forsberg, Magnus; Hulander, Mats; Vazirisani, Forugh; Palmquist, Anders; Lausmaa, Jukka; Thomsen, Peter; Trobos, Margarita

    2014-01-01

    The role of material surface properties in the direct interaction with bacteria and the indirect route via host defense cells is not fully understood. Recently, it was suggested that nanostructured implant surfaces possess antimicrobial properties. In the current study, the adhesion and biofilm formation of Staphylococcus epidermidis and human monocyte adhesion and activation were studied separately and in coculture in different in vitro models using smooth gold and well-defined nanostructured gold surfaces. Two polystyrene surfaces were used as controls in the monocyte experiments. Fluorescent viability staining demonstrated a reduction in the viability of S. epidermidis close to the nanostructured gold surface, whereas the smooth gold correlated with more live biofilm. The results were supported by scanning electron microscopy observations, showing higher biofilm tower formations and more mature biofilms on smooth gold compared with nanostructured gold. Unstimulated monocytes on the different substrates demonstrated low activation, reduced gene expression of pro- and anti-inflammatory cytokines, and low cytokine secretion. In contrast, stimulation with opsonized zymosan or opsonized live S. epidermidis for 1 hour significantly increased the production of reactive oxygen species, the gene expression of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, and IL-10, as well as the secretion of TNF-α, demonstrating the ability of the cells to elicit a response and actively phagocytose prey. In addition, cells cultured on the smooth gold and the nanostructured gold displayed a different adhesion pattern and a more rapid oxidative burst than those cultured on polystyrene upon stimulation. We conclude that S. epidermidis decreased its viability initially when adhering to nanostructured surfaces compared with smooth gold surfaces, especially in the bacterial cell layers closest to the surface. In contrast, material surface properties neither strongly

  13. Size-dependent electrocatalytic activity of gold nanoparticles on HOPG and highly boron-doped diamond surfaces.

    PubMed

    Brülle, Tine; Ju, Wenbo; Niedermayr, Philipp; Denisenko, Andrej; Paschos, Odysseas; Schneider, Oliver; Stimming, Ulrich

    2011-12-06

    Gold nanoparticles were prepared by electrochemical deposition on highly oriented pyrolytic graphite (HOPG) and boron-doped, epitaxial 100-oriented diamond layers. Using a potentiostatic double pulse technique, the average particle size was varied in the range from 5 nm to 30 nm in the case of HOPG as a support and between < 1 nm and 15 nm on diamond surfaces, while keeping the particle density constant. The distribution of particle sizes was very narrow, with standard deviations of around 20% on HOPG and around 30% on diamond. The electrocatalytic activity towards hydrogen evolution and oxygen reduction of these carbon supported gold nanoparticles in dependence of the particle sizes was investigated using cyclic voltammetry. For oxygen reduction the current density normalized to the gold surface (specific current density) increased for decreasing particle size. In contrast, the specific current density of hydrogen evolution showed no dependence on particle size. For both reactions, no effect of the different carbon supports on electrocatalytic activity was observed.

  14. Vibrational properties of an adamantane monolayer on a gold surface

    NASA Astrophysics Data System (ADS)

    Sakai, Yuki; Nguyen, Giang D.; Capaz, Rodrigo B.; Coh, Sinisa; Pechenezhskiy, Ivan V.; Hong, Xiaoping; Crommie, Michael F.; Wang, Feng; Saito, Susumu; Louie, Steven G.; Cohen, Marvin L.

    2014-03-01

    We study the vibrational properties of an adamantane monolayer on a Au(111) surface. The IR spectrum of a self-assembled monolayer of adamantane on Au(111) is measured by a newly developed infrared scanning tunneling microscopy (IRSTM) technique. We analyze the IR spectrum of this system by a density functional theory and find that the IR spectrum is severely modified by both adamantane-gold and adamantane-adamantane interactions. One of three gas-phase C-H bond stretching modes is significantly red-shifted due to the molecule-substrate interactions. The intermolecular interactions cause a suppression of the IR intensity of another gas-phase IR peak. The techniques used in this work can be applied for an independent estimate of molecule-substrate and intermolecular interactions in related diamondoid/metal-substrate systems. This work was supported by NSF grant No. DMR10-1006184 and U.S. DOE under Contract No. DE-AC02-05CH11231.

  15. ESSENTIAL ROLE OF SURFACE HYDROXYLS FOR THE STABILIZATION AND CATALYTIC ACTIVITY OF TiO2-SUPPORTED GOLD NANOPARTICLES

    SciTech Connect

    Veith, Gabriel M; Lupini, Andrew R; Dudney, Nancy J

    2009-01-01

    We report the investigation of titania supported gold catalysts prepared by magnetron sputtering. Catalysts grown on natural fumed titania were structurally unstable resulting in the rapid coarsening of 2.3 nm gold clusters into large ~20 nm gold clusters in a few days at room temperature under normal atmospheric conditions. However, treating the titania support powder to a mock-deposition-precipitation process, at pH 4 or pH 10, followed by the subsequent deposition of gold onto this treated powder produced a remarkable enhancement in gold particle stability and a 20-40 fold enhancement of catalytic activity respectively. This enhancement can not be attributed to the formation of oxygen vacancies on the TiO2 surface. Instead, it appears to be associated with the formation of strongly bound hydroxyl species on the TiO2 surface. The formation of surface hydroxyls during the deposition-precipitation method is coincidental and contributes significantly to the properties of Au/TiO2 catalysts.

  16. Gold Nanoparticles with Externally Controlled, Reversible Shifts of Local Surface Plasmon Resonance Bands

    PubMed Central

    Yavuz, Mustafa S.; Jensen, Gary C.; Penaloza, David P.; Seery, Thomas A. P.; Pendergraph, Samuel A.; Rusling, James F.; Sotzing, Gregory A.

    2010-01-01

    We have achieved reversible tunability of local surface plasmon resonance in conjugated polymer functionalized gold nanoparticles. This property was facilitated by the preparation of 3,4-ethylenedioxythiophene (EDOT) containing polynorbornene brushes on gold nanoparticles via surface-initiated ring-opening metathesis polymerization. Reversible tuning of the surface plasmon band was achieved by electrochemically switching the EDOT polymer between its reduced and oxidized states. PMID:19839619

  17. Positively charged supported lipid bilayer formation on gold surfaces for neuronal cell culture.

    PubMed

    Choi, Sung-Eun; Greben, Kyrylo; Wördenweber, Roger; Offenhäusser, Andreas

    2016-06-06

    Supported lipid bilayers are widely used as cell membrane models and sensor platforms, but the usage on gold surface needs additional surface modification or optimized experimental conditions. In this work, the authors show lipid bilayer formation on plasma activated gold surfaces in physiological conditions without any other modification if at least 30% positively charged lipids are present. Details of bilayer formation from small unilamellar vesicles were monitored using quartz crystal microbalance with dissipation in both basic and acidic environment. The authors also confirmed that this positively charged bilayer system can sustain primary cortical neuron growth and lipid transfer. This method will provide simple means to construct biomimetic interface on gold electrodes.

  18. Gold and aluminum based surface plasmon resonance biosensors: sensitivity enhancement

    NASA Astrophysics Data System (ADS)

    Biednov, Mykola; Lebyedyeva, Tetyana; Shpylovyy, Pavlo

    2015-05-01

    In this work we considered Gold and Aluminum thin films coated with additional dielectric layers as sensing platforms. Operation of these sensors is based on measuring shift in the position of the reflectivity dip in angular reflectivity spectrum of the sample. Shift can be caused by changes in the refraction index of either liquid that interacts with sensors surface (refractometric measurements) or thin adjacent biolayer on top of the sensor due to immobilization of the target molecules (biosensing). Calculations based on Fresnel equations and transfer matrix formalism allowed us to make comprehensive analysis of the angular sensitivity, shape of the reflectivity dip and dynamic range of the sensors with different dielectric coatings. Calculations were performed for both cases of bio and refractometric sensing. Results showed different dependence of the sensitivity of Au an Al based sensors upon refraction index of the dielectric coating. For Au-based surface Plasmon resonance sensor up to two times increased sensitivity can be achieved using dielectric coating with high refraction index 2.3 of proper thickness. For sensors based on aluminum we were able to achieve 50% increased angular sensitivity. At the same time width of the reflectivity dip increased proportionally to the optical thickness of the dielectric coating. For estimating sensors quality we analyzed ratio of the angular sensitivity to the width of the reflectivity dip. This ratio decreased with increase in optical thickness of the dielectric, however angular sensitivity of the sensor increased significantly. Deposition of the additional dielectric layer with high refraction index such as Niobium Oxide can also improve chemical and mechanical stability of the sensor.

  19. Quantitative surface acoustic wave detection based on colloidal gold nanoparticles and their bioconjugates.

    PubMed

    Chiu, Chi-Shun; Gwo, Shangjr

    2008-05-01

    The immobilization scheme of monodispersed gold nanoparticles (10-nm diameter) on piezoelectric substrate surfaces using organosilane molecules as cross-linkers has been developed for lithium niobate (LiNbO3) and silicon oxide (SiO2)/gold-covered lithium tantalate (LiTaO3) of Rayleigh and guided shear horizontal- (guided SH) surface acoustic wave (SAW) sensors. In this study, comparative measurements of gold nanoparticle adsorption kinetics using high-resolution field-emission scanning electron microscopy and SAW sensors allow the frequency responses of SAW sensors to be quantitatively correlated with surface densities of adsorbed nanoparticles. Using this approach, gold nanoparticles are used as the "nanosized mass standards" to scale the mass loading in a wide dynamical range. Rayleigh-SAW and guided SH-SAW sensors are employed here to monitor the surface mass changes on the device surfaces in gas and liquid phases, respectively. The mass sensitivity ( approximately 20 Hz.cm2/ng) of Rayleigh-SAW device (fundamental oscillation frequency of 113.3 MHz in air) is more than 2 orders of magnitude higher than that of conventional 9-MHz quartz crystal microbalance sensors. Furthermore, in situ (aqueous solutions), real-time measurements of adsorption kinetics for both citrate-stabilized gold nanoparticles and DNA-gold nanoparticle conjugates are also demonstrated by guided SH-SAW (fundamental oscillation frequency of 121.3 MHz). By comparing frequency shifts between the adsorption cases of gold nanoparticles and DNA-gold nanoparticle conjugates, the average number of bound oligonucleotides per gold nanoparticle can also be determined. The high mass sensitivity ( approximately 6 Hz.cm2/ng) of guided SH-SAW sensors and successful detection of DNA-gold nanoparticle conjugates paves the way for real-time biosensing in liquids using nanoparticle-enhanced SAW devices. PMID:18363384

  20. Gold nanoparticle surface functionalization: a necessary requirement in the development of novel nanotherapeutics.

    PubMed

    Nicol, James R; Dixon, Dorian; Coulter, Jonathan A

    2015-01-01

    With several gold nanoparticle-based therapies currently undergoing clinical trials, these treatments may soon be in the clinic as novel anticancer agents. Gold nanoparticles are the subject of a wide ranging international research effort with preclinical studies underway for multiple applications including photoablation, diagnostic imaging, radiosensitization and multifunctional drug-delivery vehicles. These applications require an increasingly complex level of surface modification in order to achieve efficacy and limit off-target toxicity. This review will discuss the main obstacles in relation to surface functionalization and the chemical approaches commonly utilized. Finally, we review a range of recent preclinical studies that aim to advance gold nanoparticle treatments toward the clinic.

  1. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports.

    PubMed

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H; De Stefano, Luca

    2016-12-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 10(5) is obtained. PMID:27356562

  2. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports

    NASA Astrophysics Data System (ADS)

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H.; De Stefano, Luca

    2016-06-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 105 is obtained.

  3. Electroless Gold-Modified Diatoms as Surface-Enhanced Raman Scattering Supports.

    PubMed

    Pannico, Marianna; Rea, Ilaria; Chandrasekaran, Soundarrajan; Musto, Pellegrino; Voelcker, Nicolas H; De Stefano, Luca

    2016-12-01

    Porous biosilica from diatom frustules is well known for its peculiar optical and mechanical properties. In this work, gold-coated diatom frustules are used as low-cost, ready available, functional support for surface-enhanced Raman scattering. Due to the morphology of the nanostructured surface and the smoothness of gold deposition via an electroless process, an enhancement factor for the p-mercaptoaniline Raman signal of the order of 10(5) is obtained.

  4. Reconnaissance investigation of the placer gold deposits in the Zarkashan Area of Interest, Ghazni Province, Afghanistan

    USGS Publications Warehouse

    Malpeli, Katherine C.; Chirico, Peter G.; McLoughlin, Isabel H.

    2013-01-01

    This study is a reconnaissance investigation of the placer gold deposits in the Zarkashan Area of Interest (AOI) in Ghazni Province, Afghanistan. Detailed investigations of the Zarkashan gold deposits were conducted by Soviet and Afghan geologists in the 1960s and 1970s, prior to the development of satellite-based remote-sensing platforms and new methods of geomorphic mapping. The purpose of this study was to integrate new mapping techniques with previously collected concentration and borehole sampling data and geomorphologic interpretations to reassess the placer gold deposits in the Zarkashan AOI. A methodology combining the collection and analysis of historical sampling data, digital database development, hydrologic analysis, and geomorphic modeling was used. The analysis led to the reinterpretation of four gold-bearing seams along the Zarkashan River, and the calculation of an estimated gold reserve of approximately 3,000 kilograms (kg). This estimate is approximately 1,500 kg greater than the Soviet estimate. The result differs in large part due to the reinterpretation of the seams based on a much lower cutoff grade of 100 mg/m3. Because cutoff grade is dependent in part on the price of gold, the sevenfold increase in the price of gold since the undertaking of the Soviet investigation warranted our re-evaluation of their 500 mg/m3 cutoff grade.

  5. Enhancing the Properties of Carbon and Gold Substrates by Surface Modification

    SciTech Connect

    Jennifer Anne Harnisch

    2002-06-27

    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 performance 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.

  6. Annealing Effects on the Surface Plasmon of MgO Implanted with Gold

    NASA Technical Reports Server (NTRS)

    Ueda, A.; Mu, R.; Tung, Y. -S.; Henderson, D. O.; White, C. W.; Zuhr, R. A.; Zhu, Jane G.; Wang, P. W.

    1997-01-01

    Gold ion implantation was carried out with the energy of 1.1 MeV into (100) oriented MgO single crystal. Implanted doses are 1, 3, 6, 10 x 10(exp 16) ions/sq cm. The gold irradiation results in the formation of gold ion implanted layer with a thickness of 0.2 microns and defect formation. In order to form gold colloids from the as-implanted samples, we annealed the gold implanted MgO samples in three kinds of atmospheres: (1)Ar only, (2)H2 and Ar, and (3)O2 and Ar. The annealing over 1200 C enhanced the gold colloid formation which shows surface plasmon resonance band of gold. The surface plasmon bands of samples annealed in three kinds of atmospheres were found to be at 535 nm (Ar only), 524 nm(H2+Ar), and 560 nm (02+Ar), The band positions of surface plasmon can be reversibly changed by an additional annealing.

  7. Controlling wave-vector of propagating surface plasmon polaritons on single-crystalline gold nanoplates

    PubMed Central

    Luo, Si; Yang, Hangbo; Yang, Yuanqing; Zhao, Ding; Chen, Xingxing; Qiu, Min; Li, Qiang

    2015-01-01

    Surface plasmon polaritons (SPPs) propagating at metal nanostructures play an important role in breaking the diffraction limit. Chemically synthesized single-crystalline metal nanoplates with atomically flat surfaces provide favorable features compared with traditional polycrystalline metal films. The excitation and propagation of leaky SPPs on micrometer sized (10–20 μm) and thin (30 nm) gold nanoplates are investigated utilizing leakage radiation microscopy. By varying polarization and excitation positions of incident light on apexes of nanoplates, wave-vector (including propagation constant and propagation direction) distributions of leaky SPPs in Fourier planes can be controlled, indicating tunable SPP propagation. These results hold promise for potential development of chemically synthesized single-crystalline metal nanoplates as plasmonic platforms in future applications. PMID:26302955

  8. Gold nanoparticles assisted characterization of amine functionalized polystyrene multiwell plate and glass slide surfaces

    NASA Astrophysics Data System (ADS)

    Dharanivasan, Gunasekaran; Rajamuthuramalingam, Thangavelu; Michael Immanuel Jesse, Denison; Rajendiran, Nagappan; Kathiravan, Krishnan

    2015-01-01

    We demonstrated citrate-capped gold nanoparticles assisted characterization of amine functionalized polystyrene plate and glass slide surfaces through AuNPs staining method. The effect of AuNPs concentration on the characterization of amine modified surfaces was also studied with different concentration of AuNPs (ratios 1.0-0.0). 3-Aminopropylyl triethoxy silane has been used as amine group source for the surface modification. The interactions of AuNPs on modified and unmodified surfaces were investigated using atomic force microscopy and the dispersibility, and the aggregation of AuNPs was analyzed using UV-visible spectrophotometer. Water contact angle measurement and X-ray photoelectron spectroscopy (XPS) were used to further confirmation of amine modified surfaces. The aggregation of AuNPs in modified multiwell plate leads to the color change from red to purple and they are found to be adsorped on the modified surfaces. Aggregation and adsorption of AuNPs on the modified surfaces through the electrostatic interactions and the hydrogen bonds were revealed by XPS analysis. Remarkable results were found even in the very low concentration of AuNPs (ratio 0.2). This AuNPs staining method is simple, cost-effective, less time consuming, and required very low concentration of AuNPs. These results can be read out through the naked eye without the help of sophisticated equipments.

  9. Investigation of thiol derivatized gold nanoparticle sensors for gas analysis

    NASA Astrophysics Data System (ADS)

    Stephens, Jared S.

    Analysis of volatile organic compounds (VOCs) in air and exhaled breath by sensor array is a very useful testing technique. It can provide non-invasive, fast, inexpensive testing for many diseases. Breath analysis has been very successful in identifying cancer and other diseases by using a chemiresistor sensor or array with gold nanoparticles to detect biomarkers. Acetone is a biomarker for diabetes and having a portable testing device could help to monitor diabetic and therapeutic progress. An advantage to this testing method is it is conducted at room temperature instead of 200 degrees Celsius. 3. The objective of this research is to determine the effect of thiol derivatized gold nanoparticles based on sensor(s) detection of VOCs. The VOCs to be tested are acetone, ethanol, and a mixture of acetone and ethanol. Each chip is tested under all three VOCs and three concentration levels (0.1, 1, and 5.0 ppm). VOC samples are used to test the sensors' ability to detect and differentiate VOCs. Sensors (also referred to as a chip) are prepared using several types of thiol derivatized gold nanoparticles. The factors are: thiol compound and molar volume loading of the thiol in synthesis. The average resistance results are used to determine the VOC selectivity of the sensors tested. The results show a trend of increasing resistance as VOC concentration is increased relative to dry air; which is used as baseline for VOCs. Several sensors show a high selectivity to one or more VOCs. Overall the 57 micromoles of 4-methoxy-toluenethiol sensor shows the strongest selectivity for VOCs tested. 3. Gerfen, Kurt. 2012. Detection of Acetone in Air Using Silver Ion Exchanged ZSM-5 and Zinc Oxide Sensing Films. Master of Science thesis, University of Louisville.

  10. Electroanalysis using macro-, micro-, and nanochemical architectures on electrode surfaces. Bulk surface modification of glassy carbon microspheres with gold nanoparticles and their electrical wiring using carbon nanotubes.

    PubMed

    Dai, Xuan; Wildgoose, Gregory G; Salter, Chris; Crossley, Alison; Compton, Richard G

    2006-09-01

    Gold nanoparticles (approximately 30-60 nm in diameter) were deposited onto the surface of glassy carbon microspheres (10-20 microm) through electroless plating to produce bulk (i.e., gram) quantities of nanoparticle surface-modified microspheres. The gold nanoparticle-modified powder was then characterized by means of scanning electron microscopy and cyclic voltammetry. The voltammetric response of a macroelectrode consisting of a film of gold nanoparticle-modified glassy carbon microspheres, bound together and "wired-up" using multiwalled carbon nanotubes (MWCNTs), was investigated. We demonstrate that by intelligently exploiting both nano- and microchemical architectures and wiring up the electroactive centers using MWCNTs in this way, we can obtain macroelectrode voltammetric behavior while only using approximately 1% by mass of the expensive gold material that would be required to construct the equivalent gold film macrodisk electrode. The potential utility of electrodes constructed using chemical architectures such as this was demonstrated by applying them to the analytical determination of arsenic(III) concentration. An optimized limit of detection of 2.5 ppb was obtained.

  11. Surface enhanced Raman scattering of amino acids assisted by gold nanoparticles and Gd(3+) ions.

    PubMed

    López-Neira, Juan Pablo; Galicia-Hernández, José Mario; Reyes-Coronado, Alejandro; Pérez, Elías; Castillo-Rivera, Francisco

    2015-05-01

    The surface enhanced raman scattering (SERS) signal from the l-tyrosine (tyr) molecule adsorbed on gold nanoparticles (Au-tyr) is compared with the SERS signal assisted by the presence of gadolinium ions (Gd(3+)) coordinated with the Au-tyr system. An enhancement factor of the SERS signal in the presence of Gd(3+) ions was ∼5 times higher than that produced by l-tyrosine adsorbed on gold nanoparticles. The enhancement of the SERS signal can be attributed to a corresponding increase in the local electric field due to the presence of Gd(3+) ions in the vicinity of a gold dimer configuration. This scenario was confirmed by solving numerically Maxwell equations, showing an increase of 1 order of magnitude in the local electric scattered field when the Gd(3+) ion is located in between a gold dimer compared with naked gold nanoparticles.

  12. Surface Engineering of Triboelectric Nanogenerator with an Electrodeposited Gold Nanoflower Structure

    PubMed Central

    Park, Sang-Jae; Seol, Myeong-Lok; Jeon, Seung-Bae; Kim, Daewon; Lee, Dongil; Choi, Yang-Kyu

    2015-01-01

    A triboelectric nanogenerator composed of gold nanoflowers is demonstrated. The proposed triboelectric nanogenerator creates electricity by contact-separation-based electrification between an anodic metal and a cathodic polymer. For the improvement of output power via the enlargement of the effective surface area in the anodic metal, gold nanoflowers that produce a hierarchical morphology at a micro-to-nano scale by electrodeposition are utilized. The hierarchical morphology is controlled by the applied voltage and deposition time. Even though the triboelectric coefficient of gold is inferior to those of other metals, gold is very attractive to make a flower-like structure by electrodeposition. Moreover, gold is stable against oxidation by oxygen in air. From a reliability and practicality point of view, the aforementioned stability against oxidation is preferred. PMID:26365054

  13. Embrittlement of surface mount solder joints by hot solder-dipped, gold-plated leads

    SciTech Connect

    Vianco, P.T.

    1993-07-01

    The detachment of beam-leaded transistors from several surface mount circuit boards following modest thermal cycling was examined. Microstructural analysis of the package leads and bonding pads from the failed units indicated that gold embrittlement was responsible for a loss of solder joint mechanical integrity that caused detachment of transistors from the circuit boards. An analysis of the hot dipping process used to remove gold from the leads prior to assembly demonstrated that the gold, although dissolved from the lead, remained in the nearby solder and was subsequently retained in the coating formed on the lead upon withdrawal from the bath. This scenario allowed gold to enter the circuit board solder joints. It was hypothesized, and later confirmed by experimental trials, that increasing the number of dips prevented gold from entering the solder coatings.

  14. Characterizing Optical Properties of Self-Assembled Gold Nanoparticles for Surface Plasmon Resonance Device Applications

    NASA Astrophysics Data System (ADS)

    Chen, Hsuen-Li; Cheng, Hsu-Chun; Ko, Tsung-Shine; Chuang, Shang-Yu; Chu, Tien-Chi

    2006-09-01

    In this study, the optical constants of gold nanoparticles are evaluated for surface plasmon-based sensor applications. Using an effective medium approximation (EMA) and ellipsometry, approaches to monitor the self-assembly of gold nanoparticles are also demonstrated. Spectroscopic ellipsometric parameters measured (\\tan\\Psi, \\cosΔ) before and after adding gold nanoparticles to a substrate are used to calculate the optical constants of gold nanoparticles. The film thickness is measured by grazing incidence X-ray reflectivity (XRR). The optical constants (refractive index, extinction coefficient) of gold nanoparticles can be obtained from the measured ellipsometric parameters and thickness. We also show that particles density can be well predicted and detected nondestructively by this method.

  15. Investigation of nanoparticle formation in a plasma produced by femtosecond laser ablation of gold

    SciTech Connect

    Spiga, P.; Hermann, J.; Itina, T.; Grojo, D.; Neamtu, D.; Pailharey, D.; Marine, W.

    2005-10-31

    The formation of nanoparticles in a plasma produced by the interaction of ultrashort laser pulses with gold has been investigated. Three different experimental techniques were employed. (i) The plume expansion was characterized using fast imaging with the aid of an intensified charge-coupled device. (ii) The plasma composition was analyzed using time- and space-resolved optical emission spectroscopy. (iii) The ablated material was deposited on mica substrates and analyzed by means of atomic force microscopy. As a result, the size-distribution and the overall number of nanoparticles were determined as a function of the laser energy density incident on the target surface. The detection of particles with sizes in the nanometer range supports theoretical modeling according to which phase explosion is the dominant mechanism of metal ablation by ultrashort laser pulses.

  16. Far- and near-field properties of gold nanoshells studied by photoacoustic and surface-enhanced Raman spectroscopies.

    PubMed

    Weber, V; Feis, A; Gellini, C; Pilot, R; Salvi, P R; Signorini, R

    2015-09-01

    Gold nanoshells, with a silica core and different core and shell dimensions, have been extensively investigated. Optical far-field properties, namely extinction and absorption, have been separately determined by means of spectrophotometry and photoacoustic spectroscopy, respectively, in the 440-900 nm range. The enhancement factor for surface-enhanced Raman scattering, which is related to near-field effects, has been measured from 568 to 920 nm. The absorption contribution to extinction decreases as the overall diameter increases. Moreover, absorption and scattering display different spectral distributions, the latter being red shifted. The Surface Enhanced Raman Scattering enhancement profile, measured using thiobenzoic acid as a Raman probe, is further shifted to the red. The latter result suggests that the enhancement is dominated by the presence of hot spots, which are possibly related to the surface roughness of gold nanoshell particles. PMID:25559555

  17. Investigation of gold-bearing veins using magnetics and TEM

    NASA Astrophysics Data System (ADS)

    Davis, L.; Groom, R.

    2012-12-01

    Gold-bearing fractures have been mined at Charters Towers, Queensland for a century. The ore occurs in quartz-sulfide veins hosted in granitoids. The gold is found in lenses within the veins. The purpose of our work was to determine if geophysical methods could be used to identify and delineate known lode-bearing veins. The study site is around the Warrior Mine immediately south of the town. Two structures are being mined at 100-300 m depth: Warrior and Sons of Freedom. While IP is typically used to locate disseminated sulfides, we used a different approach: we integrated airborne magnetic data with ground TEM data to map the geometries of the gold-bearing fracture zones. TEM is advantageous because it does not involve injection of current into the ground with the uncertainty of current flow patterns in such resistive, fractured rocks. Fixed loop TEM surveying was utilized as this approach is much faster to perform than moving loop surveys. Although TEM is commonly used for mapping layered structures and strong conductors, it is much less used for detecting weak conductors, such as those found in gold exploration, contaminant plumes, or geotechnical applications. Here the fracture zones are highly weathered and wet thus producing weak conductors. Upon mapping the vertical derivative of the RTP magnetic data, many linear anomalies were noted, including over both mined structures. These anomalies all indicate negative susceptibility, as would be expected because the structures are depleted in magnetite with respect to the granitoids. Modeling of the RTP total field and derivatives confirms a negative susceptibility. The RTP data indicate the approximate dip, which agrees with known information. Depth resolution is limited in standard 3D inversions, which utilize orthogonal grids with the normal axis in the vertical direction. In this study, we use a dipping grid which strikes and dips according to known information, and have obtained good results. TEM surveying at

  18. Titanium dental implants surface-immobilized with gold nanoparticles as osteoinductive agents for rapid osseointegration.

    PubMed

    Heo, Dong Nyoung; Ko, Wan-Kyu; Lee, Hak Rae; Lee, Sang Jin; Lee, Donghyun; Um, Soong Ho; Lee, Jung Haeng; Woo, Yi-Hyung; Zhang, Lijie Grace; Lee, Deok-Won; Kwon, Il Keun

    2016-05-01

    Gold nanoparticles (GNPs) are quite attractive materials for use as osteogenic agents due to their potential effects on the stimulation of osteoblast differentiation. In this study, an osseo-integrated titanium (Ti) implant surface coated with GNPs was used for promotion of bone regeneration. We prepared a silanized Ti surface by chemical treatment of (3-Mercaptopropyl) trimethoxysilane (MPTMS) and immobilized the GNP layer (Ti-GNP) on their surfaces via Au-S bonding. The GNP layer is uniformly immobilized on the surface and the layer covers the titanium oxide surface well, as confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Ti-GNP was used to investigate the effectiveness of this system both in vitro and in vivo. The in vitro results showed that the Ti-GNP significantly enhances the osteogenic differentiation with increased mRNA expression of osteogenic differentiation specific genes in human adipose-derived stem cells (ADSCs). Furthermore, the in vivo results showed that Ti-GNP had a significant influence on the osseous interface formation. Through these in vitro and vivo tests, we found that Ti-GNP can be useful as osseo-integration inducing dental implants for formation of an osseous interface and maintenance of nascent bone formation. PMID:26874978

  19. Titanium dental implants surface-immobilized with gold nanoparticles as osteoinductive agents for rapid osseointegration.

    PubMed

    Heo, Dong Nyoung; Ko, Wan-Kyu; Lee, Hak Rae; Lee, Sang Jin; Lee, Donghyun; Um, Soong Ho; Lee, Jung Haeng; Woo, Yi-Hyung; Zhang, Lijie Grace; Lee, Deok-Won; Kwon, Il Keun

    2016-05-01

    Gold nanoparticles (GNPs) are quite attractive materials for use as osteogenic agents due to their potential effects on the stimulation of osteoblast differentiation. In this study, an osseo-integrated titanium (Ti) implant surface coated with GNPs was used for promotion of bone regeneration. We prepared a silanized Ti surface by chemical treatment of (3-Mercaptopropyl) trimethoxysilane (MPTMS) and immobilized the GNP layer (Ti-GNP) on their surfaces via Au-S bonding. The GNP layer is uniformly immobilized on the surface and the layer covers the titanium oxide surface well, as confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Ti-GNP was used to investigate the effectiveness of this system both in vitro and in vivo. The in vitro results showed that the Ti-GNP significantly enhances the osteogenic differentiation with increased mRNA expression of osteogenic differentiation specific genes in human adipose-derived stem cells (ADSCs). Furthermore, the in vivo results showed that Ti-GNP had a significant influence on the osseous interface formation. Through these in vitro and vivo tests, we found that Ti-GNP can be useful as osseo-integration inducing dental implants for formation of an osseous interface and maintenance of nascent bone formation.

  20. Fast self-assembly kinetics of alkanethiols on gold nanoparticles: simulation and characterization by localized surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Asiaei, Sasan; Denomme, Ryan C.; Marr, Chelsea; Nieva, Patricia M.; Vijayan, Mathilakath M.

    2012-03-01

    This study demonstrates improved kinetics for the formation of self-assembled monolayers (SAMs) of alkanethiols on gold nanoparticle substrates. A computational model was developed to predict SAM growth kinetics. Based on the predictions from the model, SAMs of 11-mercaptoundecanoic acid (11-MUA) and 1-octanethiol (1-OT) were formed by incubation of gold nanoparticle chips in an ethanolic 10 mM solution within 20 min. The performance of this novel rapid SAM formation protocol was compared with a conventional 24 hour incubation protocol. Binding capacity of the alkanethiol SAM was investigated for a 20 min incubation protocol using biotin-streptavidin. For this purpose, the SAM loaded gold nanoparticle chips were modified with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) to allow attachment of EZ-Link amine PEG3 biotin to the 11-MUA molecules. Binding reactions were monitored in real time using localized surface plasmon resonance (LSPR) spectroscopy. The resulting LSPR absorbance peak shift was comparable to the experimental results for biotin-streptavidin reported in literature. Results of this study suggest that formation of a high quality alkanethiol SAM within 20 min on gold nanoparticles surfaces is possible and could greatly reduce the time and cost compared to conventional 24 h incubation protocols.

  1. 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.

  2. Ammonia gas sensing behavior of graphene surface decorated with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Gautam, Madhav; Jayatissa, Ahalapitiya H.

    2012-12-01

    Ammonia gas sensing behavior of graphene synthesized by CVD on copper substrate using a methane and hydrogen gas mixture was investigated. The Raman spectroscopy was used to monitor the quality of graphene films transferred onto SiO2/Si substrates. The sensitivity and the recovery time of the device were enhanced by the deposition of gold nanoparticles on the surface of graphene films. The dependence of the sensing response with the operating temperature was studied. The adsorption and desorption curves were analyzed using Langmuir kinetic theory and Freundlich isotherm for the adsorption of ammonia gas. The activation energy and the heat of adsorption were estimated to be around 38 and 41 meV, respectively for NH3 gas concentration of 58 ppm at room temperature.

  3. Anisotropic shift of surface plasmon resonance of gold nanoparticles doped in nematic liquid crystal.

    PubMed

    Choudhary, Amit; Li, Guoqiang

    2014-10-01

    Study of the liquid crystal (LC) director around nanoparticles has been an important topic of research very recently, since it allows design and fabrication of next-generation LC devices that are impossible in the past. In our experiment, alkanethiol-capped gold nanoparticles (GNPs) were dispersed in nematic LC. Analysis of the LC director around GNPs was performed by investigating the behavior of surface plasmon polariton (SPP) absorption peaks of the GNPs using spectrophotometry technique. It is found that the incident linearly polarized light orientated at 0°, 45°, and 90° angles with respect to the rubbing direction experiences varying interaction with the LC medium. The corresponding transmission of light reveals the anisotropic shift in wavelength of SPP peak. The anisotropic behavior of SPPs of the GNPs is in agreement with theoretical calculations. PMID:25322010

  4. Anisotropic shift of surface plasmon resonance of gold nanoparticles doped in nematic liquid crystal

    PubMed Central

    Choudhary, Amit; Li, Guoqiang

    2014-01-01

    Study of the liquid crystal (LC) director around nanoparticles has been an important topic of research very recently, since it allows design and fabrication of next-generation LC devices that are impossible in the past. In our experiment, alkanethiol-capped gold nanoparticles (GNPs) were dispersed in nematic LC. Analysis of the LC director around GNPs was performed by investigating the behavior of surface plasmon polariton (SPP) absorption peaks of the GNPs using spectrophotometry technique. It is found that the incident linearly polarized light orientated at 0°, 45°, and 90° angles with respect to the rubbing direction experiences varying interaction with the LC medium. The corresponding transmission of light reveals the anisotropic shift in wavelength of SPP peak. The anisotropic behavior of SPPs of the GNPs is in agreement with theoretical calculations. PMID:25322010

  5. Surface-enhanced Raman scattering from finite arrays of gold nano-patches

    SciTech Connect

    Vincenti, M. A.; Ceglia, D. de; Grande, M.; Petruzzelli, V.; D'Orazio, A.; Bianco, G. V.; Bruno, G.; Stomeo, T.; De Vittorio, M.; Scalora, M.

    2013-01-07

    We experimentally investigate the surface-enhanced Raman scattering (SERS) response of a 2D-periodic array of square gold nano-patches, functionalized by means of a conjugated, rigid thiol. We measure a Raman signal enhancement up to 200 times more intense compared to other plasmon-based nanostructures functionalized with the same molecule, and show that the enhancement is not strictly correlated to the presence of plasmonic resonances. The agreement between experimental and theoretical results reveals the importance of a full-wave analysis based on the inclusion of the actual scattering cross section of the molecule. The proposed numerical approach may serve not only as a tool to predict the enhancement of Raman signal scattered from strongly resonant nanostructure but also as an effective instrument to engineer SERS platforms that target specific molecules.

  6. Slanted gold mushroom array: a switchable bi/tridirectional surface plasmon polariton splitter.

    PubMed

    Shen, Yang; Fang, Guisheng; Cerjan, Alexander; Chi, Zhenguo; Fan, Shanhui; Jin, Chongjun

    2016-08-25

    Surface plasmon polaritons (SPPs) show great promise in providing an ultracompact platform for integrated photonic circuits. However, challenges remain in easily and efficiently coupling light into and subsequently routing SPPs. Here, we theoretically propose and experimentally demonstrate a switchable bi/tridirectional beam splitter which can simultaneously perform both tasks. The photonic device consists of a periodic array of slanted gold 'mushrooms' composed of angled dielectric pillars with gold caps extruding from a periodic array of perforations in a gold film. The unidirectional coupling results from the interference of the in-plane guided modes scattered by a pair of dislocated gold gratings, while the output channel is determined by the polarization of the incident beam. This device, in combination with dynamic polarization modulation techniques, has the potential to serve as a router or switch in plasmonic integrated circuits. PMID:27523083

  7. Monitoring Gold Nanorod Synthesis based on their Localized Surface Plasmon Resonance

    NASA Astrophysics Data System (ADS)

    Gulati, Amneet; Liao, Hongwei; Hafner, Jason

    2006-03-01

    The extinction spectra of structurally anisotropic gold nanoparticles exhibit surface plasmon resonances that may be tuned through the visible and near-infrared portions of the electromagnetic spectrum by controlling their geometry. Gold nanorods, whose longitudinal extinction peak is proportional to their aspect ratio, are synthesized by reduction of gold chloride onto gold seed nanoparticles. While growth anisotropy is known to be induced by a surfactant (cetyltrimethylammonium bromide), the detailed growth mechanism is poorly understood. Here, we study the growth kinetics of nanorods by continually monitoring their extinction spectra during synthesis. The spectra are analyzed by Rayleigh-Gans theory to determine the instantaneous length and diameter of the growing nanorods. This data yields microscopic growth rates which provide insight into the mechanism of nanorod synthesis.

  8. Gold nanonetwork film on the ITO surface exhibiting one-dimensional optical properties

    PubMed Central

    2012-01-01

    A network of gold nanostructures exhibiting one-dimensional gold nanostructure properties may become a prospective novel structure for optical, electrical and catalytic applications benefited by its unusual characteristics resulting from the collective properties of individual nanostructures in the network. In this paper, we demonstrate a facile method for the formation of high-density gold nanonetwork film on the substrate surface composed of quasi-1D nanoparticles (typically fusiform) with length ca. 10 nm - via reduction of gold ions in the presence of nanoseeds attached surface, binary surfactants of cetyltrimethylammonium bromide and hexamethyleneteramine and Ag+ ions. The length of the nanonetworks can be up to ca. 100 nm, which corresponds to the aspect ratio of ca. 10. The quasi-1D gold nanostructures as well as the nanonetworks were found to be sensitive to the binary surfactants system and the Ag+ ions as they can only be formed if all the chemicals are available in the reaction. The nanonetworks exhibit unique 1D optical properties with the presence of transverse and longitudinal surface plasmon resonance absorption. Owing to their peculiar structures that are composed of small quasi-1D nanoparticles, the nanonetworks may produce unusual optical and catalytic properties, which are potentially used in surface-enhanced Raman scattering, catalysis and optical and non-linear optical applications. PMID:22587640

  9. Shallow to near-surface, vein-type epithermal gold mineralization at Lalab in the Sibutad gold deposit, Zamboanga del Norte, Mindanao, Philippines

    NASA Astrophysics Data System (ADS)

    Jimenez, F. A.; Yumul, G. P.; Maglambayan, V. B.; Tamayo, R. A.

    2002-12-01

    The Sibutad vein-type epithermal gold deposit is the most promising economically feasible gold mineralization found in recent years in Zamboanga del Norte province in Zamboanga Peninsula, Mindanao island. The Sibutad gold deposit occurs in Pliocene to Pleistocene volcanic rocks, resting on a deformed island arc block to the east of the tectonically active Sindangan-Cotabato-Daguma Lineament. The host rocks are the Malindang Volcanics, composed of lower and upper members, which are both intruded by andesite porphyry. The lower member is made up of andesite flows, dacite tuff and tuffite, whereas volcanic breccia and tuff breccia characterize the upper member. The Sibutad gold deposit is subdivided into the Larayan and Lalab prospects. In Lalab, which is the prospect studied, hydrothermal activity and gold mineralization occur in the andesite flows. The geology, alteration and mineralization of the Lalab orebody are of adularia-sericite type that suggests the gold was precipitated from reduced, near-neutral pH solutions within a shallow to near-surface environment. The following events produced the Lalab orebody: (1) pre-breccia wallrock alteration, (2) hydrothermal brecciation, (3) post-breccia wallrock alteration, and (4) gold mineralization. Gold precipitated in quartz veins was a response to boiling, followed by fluid mixing. Prolific gold zones occur between 30 m below sea level and 200 m above sea level.

  10. Charge Retention by Gold Clusters on Surfaces Prepared Using Soft Landing of Mass Selected Ions

    SciTech Connect

    Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

    2012-01-24

    Monodisperse gold clusters have been prepared on surfaces in different charge states through soft landing of mass-selected ions. Ligand-stabilized gold clusters were prepared in methanol solution by reduction of chloro(triphenylphosphine)gold(I) with borane tert-butylamine complex in the presence of 1,3-bis(diphenylphosphino)propane. Electrospray ionization was used to introduce the clusters into the gas-phase and mass-selection was employed to isolate a single ionic cluster species (Au11L53+, L = 1,3-bis(diphenylphosphino)propane) which was delivered to surfaces at well controlled kinetic energies. Using in-situ time of flight secondary ion mass spectrometry (TOF-SIMS) it is demonstrated that the Au11L53+ cluster retains its 3+ charge state when soft landed onto the surface of a 1H,1H,2H,2H-

  11. Efficient coupling and transport of a surface plasmon at 780 nm in a gold nanostructure

    NASA Astrophysics Data System (ADS)

    Gong, Yu; Joly, Alan G.; El-Khoury, Patrick Z.; Hess, Wayne P.

    2015-08-01

    We study plasmonic nanostructures in single-crystal gold with scanning electron and femtosecond photoemission electron microscopies. We design an integrated laser coupling and nanowire waveguide structure by focused ion beam lithography in single-crystal gold flakes. The photoemission results show that the laser field is efficiently coupled into a propagating surface plasmon by a simple hole structure and propagates efficiently in an adjacent nano-bar waveguide. A strong local field is created by the propagating surface plasmon at the nano-bar tip. A similar structure, with a decreased waveguide width and thickness, displayed significantly more intense photoemission indicating enhanced local electric field at the sharper tip.

  12. Anchoring gold nanoparticles onto a mica surface by oxygen plasma ashing for sequential nanocomponent assembly

    NASA Astrophysics Data System (ADS)

    Takagi, Akihiko; Ojima, Kaoru; Mikamo, Eriko; Matsumoto, Takuya; Kawai, Tomoji

    2007-01-01

    Water-soluble gold nanoparticles were immobilized in both polar (water) and nonpolar (chloroform) liquids on hydrophilic mica surface by oxygen plasma ashing. It is then demonstrated that a DNA with a thiol at an extremity is attached to the immobilized nanoparticles due to the gold-thiol coupling and stretched in the flow direction of the following water rinse. This technique allows a sequential integration of nanoparticles and molecules for various solutions, since the nanoparticles remain on a solid surface rather than dissolve into the solution.

  13. Efficient Coupling and Transport of a Surface Plasmon at 780 nm in a Gold Nanostructure

    SciTech Connect

    Gong, Yu; Joly, Alan G.; El-Khoury, Patrick Z.; Hess, Wayne P.

    2015-08-28

    We studied plasmonic nanostructures in single-crystal gold with scanning electron and femtosecond photoemission electron microscopies. We designed an integrated laser coupling and nanowire waveguide structure by focused ion beam lithography in single-crystal gold flakes. The photoemission results show that the laser field is efficiently coupled into a propagating surface plasmon by a simple hole structure and propagates efficiently in an adjacent nano-bar waveguide. A strong local field is created by the propagating surface plasmon at the nano-bar tip. A similar structure, with a decreased waveguide width and thickness, displayed significantly more intense photoemission indicating enhanced local electric field at the sharper tip.

  14. Anchoring gold nanoparticles onto a mica surface by oxygen plasma ashing for sequential nanocomponent assembly

    SciTech Connect

    Takagi, Akihiko; Ojima, Kaoru; Mikamo, Eriko; Matsumoto, Takuya; Kawai, Tomoji

    2007-01-22

    Water-soluble gold nanoparticles were immobilized in both polar (water) and nonpolar (chloroform) liquids on hydrophilic mica surface by oxygen plasma ashing. It is then demonstrated that a DNA with a thiol at an extremity is attached to the immobilized nanoparticles due to the gold-thiol coupling and stretched in the flow direction of the following water rinse. This technique allows a sequential integration of nanoparticles and molecules for various solutions, since the nanoparticles remain on a solid surface rather than dissolve into the solution.

  15. Super-Period Gold Nanodisc Grating-Enabled Surface Plasmon Resonance Spectrometer Sensor.

    PubMed

    Tian, Xueli; Guo, Hong; Bhatt, Ketan H; Zhao, Song Q; Wang, Yi; Guo, Junpeng

    2015-10-01

    We experimentally demonstrate a surface plasmon resonance spectrometer sensor by using an e-beam-patterned super-period gold nanodisc grating on a glass substrate. The super-period gold nanodisc grating has a small subwavelength period and a large diffraction grating period. The small subwavelength period enhances localized surface plasmon resonance, and the large diffraction grating period diffracts surface plasmon resonance radiation into different directions corresponding to different wavelengths. Surface plasmon resonance spectra are measured in the first order diffraction spatial profiles captured by a charge-coupled device (CCD) in addition to the traditional way of measurement using an external optical spectrometer in the zeroth order transmission. A surface plasmon resonance sensor for the bovine serum albumin protein nanolayer bonding is demonstrated by measuring the surface plasmon resonance shift in the first order diffraction spatial intensity profiles captured by the CCD.

  16. Mechanically tunable surface plasmon resonance based on gold nanoparticles and elastic membrane polydimethylsiloxane composite

    NASA Astrophysics Data System (ADS)

    Chiang, Yu-Lun; Chen, Chih-Wei; Wang, Chun-Hsiung; Hsieh, Chun-Yi; Chen, Yung-Ting; Shih, Han-Yu; Chen, Yang-Fang

    2010-01-01

    Surface plasmon in nanoscaled materials has recently attracted a great deal of attention due to its possibility in a wide range of application. From a practical standpoint, it is desirable for the devices having a tunability of surface plasmon frequency. To achieve this goal, in this study, a composite consisting of two-dimensional gold nanoparticles array embedded in elastic polydimethylsiloxane (PDMS) membrane has been synthesized. Because the elastic PDMS membrane has a high malleability, with an external stress, it is very easy to regulate the interparticle distance in the gold nanoparticle array. The change in the distance between each nanoparticle will alter the surface plasmon interaction, and hence surface plasmon frequency can be manipulated. It is found that when the interparticle distance increases, the enhanced surface plasma mutual coupling will cause the blueshift of surface plasmon resonance frequency. The observed result satisfies the forecast based on electromagnetic theory.

  17. Do particle size and surface functionality affect uptake and depuration of gold nanoparticles by aquatic invertebrates?

    PubMed

    Park, Sujung; Woodhall, James; Ma, Guibin; Veinot, Jonathan G C; Boxall, Alistair B A

    2015-04-01

    Because of the widespread use of engineered nanoparticles (ENPs) in consumer and industrial products, it is inevitable that these materials will enter the environment. It is often stated that the uptake of ENPs into organisms in the environment is related to the particle size and surface functionality. To test this assumption, the present study investigated the uptake and depuration of gold nanoparticle (Au NPs) coated with either citrate (Au-citrate NPs), mercaptoundecanoic acid (Au-MUDA NPs), amino polyethylene glycol (PEG) thiol (Au-NH2 NPs), or PEG (Au-PEG NP) by the aquatic invertebrate Gammarus pulex. The studies were performed using a range of standard ecotoxicity media and natural waters, resulting in varying degrees of aggregation of the different NPs. Uptake of gold by G. pulex varied depending on the surface coatings, with Au-MUDA and Au-citrate NPs being taken up to a greater extent than Au-NH2 and Au-PEG NPs in all test media and natural waters. In all test media evaluated, higher amounts of amino and PEG-coated ENPs were eliminated compared with MUDA- and citrate-coated ENPs. No obvious relationships were seen between the aggregation state of the different Au NPs in treatment and uptake, suggesting that the widely accepted assumption that Au NP uptake is related to particle size does not hold for the range of aggregation states studied (67.1-178.8 nm). Positive correlations between particle number concentration in the media and uptake were observed, indicating that this factor might partly explain the differences in uptake of a particle from different media types.

  18. Photothermal investigation of the laser-induced modification of a single gold nano-particle in a silica film

    NASA Astrophysics Data System (ADS)

    Bertussi, B.; Natoli, J.-Y.; Commandre, M.; Rullier, J.-L.; Bonneau, F.; Combis, P.; Bouchut, P.

    2005-10-01

    Absorbing defects are believed to induce thermal effects that lead to laser damage, but the correlation between defect absorption and damage has not been clearly demonstrated. A model system consisting of a thin-film of silica containing gold nano-particles serving as nano-scale absorbing defects is investigated. For this purpose, a photothermal microscope coupled with a pulsed Nd:YAG laser allow us to follow the evolution of gold inclusion absorption before and after laser irradiation, without repositioning the sample. The "pre-damage" threshold had been defined previously as the laser fluence causing localized modification of the defect absorption without any surface modification. Thanks to the high sensitivity of photothermal microscopy, we find this threshold to be sevenfold less than that for the appearance of surface cracks. Numerical simulations are performed to evaluate the thermal evolution of the inclusion as a function of the laser fluence. From the comparison of experimental and theoretical results, we observe that the pre-damage threshold is closely linked to the melting of the metallic inclusion. Furthermore, the effect of repetitive shots on the evolution of gold inclusion absorption is examined experimentally and discussed.

  19. Geometric effect on surface enhanced Raman scattering of nanoporous gold: Improving Raman scattering by tailoring ligament and nanopore ratios

    SciTech Connect

    Lang, X. Y.; Chen, L. Y.; Guan, P. F.; Fujita, T.; Chen, M. W.

    2009-05-25

    We have synthesized nanoporous gold (NPG) films with a nanostructure consisting of small nanopores and large gold ligaments by the combination of chemical dealloying and electroless plating. The NPG films exhibit dramatic improvement in surface enhanced Raman scattering (SERS) in comparison with the conventional NPG. The superior SERS effect of the NPG films results from the confluence effect of enhanced local surface plasmon fields and electromagnetic coupling between ligaments, as well as the weak plasmon damping with increasing gold ligament sizes.

  20. Surface plasmon enhanced heating of gold nanoparticles: A plasmonic optical switch

    NASA Astrophysics Data System (ADS)

    Evans, Philip G.

    Recent work by Lereu et al. (Appl. Phys. Lett. Vol. 86, 154101, 2005) demonstrates a method of all-optical transfer of modulation signals using surface plasmon excitation on thin gold films. Localized heating of the film, resulting from surface plasmon decay, alter the optical properties of the device. A similar optical modulation method is now presented using gold nanoparticles. Computational models are used to generate realistic values of the thermo-optical response of gold and the thermal dynamics of a hot nanoparticle-substrate device. Differential pump-probe reflectivity measurements were perferomed and demonstrate modulation frequencies of upto 10kHz, an improvement of two orders of magnitude over the thin-film device. Sample fabrication techniques using physical vapor deposition and interference lithography, and heat transport on the nanoscale are also discussed.

  1. Gold nanodome-patterned microchips for intracellular surface-enhanced Raman spectroscopy.

    PubMed

    Wuytens, Pieter C; Subramanian, Ananth Z; De Vos, Winnok H; Skirtach, Andre G; Baets, Roel

    2015-12-21

    While top-down substrates for surface-enhanced Raman spectroscopy (SERS) offer outstanding control and reproducibility of the gold nanopatterns and their related localized surface plasmon resonance, intracellular SERS experiments heavily rely on gold nanoparticles. These nanoparticles often result in varying and uncontrollable enhancement factors. Here we demonstrate the use of top-down gold-nanostructured microchips for intracellular sensing. We develop a tunable and reproducible fabrication scheme for these microchips. Furthermore we observe the intracellular uptake of these structures, and find no immediate influence on cell viability. Finally, we perform a proof-of-concept intracellular SERS experiment by the label-free detection of extraneous molecules. By bringing top-down SERS substrates to the intracellular world, we set an important step towards time-dependent and quantitative intracellular SERS.

  2. Site-specific immobilization of protein layers on gold surfaces via orthogonal sortases.

    PubMed

    Raeeszadeh-Sarmazdeh, Maryam; Parthasarathy, Ranganath; Boder, Eric T

    2015-04-01

    We report a site-specific, sortase-mediated ligation to immobilize proteins layer-by-layer on a gold surface. Recombinant fluorescent proteins with a Sortase A recognition tag at the C-terminus were immobilized on peptide-modified gold surfaces. We used two sortases with different substrate specificities (Streptococcus pyogenes Sortase A and Staphylococcus aureus Sortase A) to immobilize layers of GFP and mCherry site-specifically on the gold surface. Surfaces were characterized using fluorescence and atomic force microscopy after immobilizing each layer of protein. Fluorescent micrographs showed that both protein immobilization on the modified gold surface and protein oligomerization are sortase-dependent. AFM images showed that either homogenous protein monolayers or layers of protein oligomers can be generated using appropriately tagged substrate proteins. Using Sortase A variants with orthogonal peptide substrate specificities, site-specific immobilization of appropriately tagged GFP onto a layer of immobilized mCherry was achieved without disruption of the underlying protein layer.

  3. In situ surface characterization and oxygen reduction reaction on shape-controlled gold nanoparticles.

    PubMed

    Hernández, J; Solla-Gullón, J; Herrero, E; Feliu, J M; Aldaz, A

    2009-04-01

    Gold nanoparticles of different shapes/surface structures were synthesized and electrochemically characterized. An in-situ surface characterization of the Au nanoparticles, which was able to obtain qualitative information about the type and relative sizes of the different facets present in the surface of the Au nanoparticles, was carried out by using Pb Under Potential Deposition (UPD) in alkaline solutions as a surface sensitive tool. The results obtained show that the final atomic arrangement on the surface can be different from that expected from the bulk structure of the well-defined shape Au nanoparticles. In this way, the development of precise in-situ methods to measure the distribution of the different sites on the nanoparticle surface, as lead UPD on gold surfaces, is highlighted. Oxygen Reduction Reaction (ORR) was performed on the different Au nanoparticles. In agreement with the particular sensitivity of the oxygen reduction to the presence of Au(100) surface domains, cubic Au nanoparticles show much better electrocatalytic activity for ORR than small spherical particles and long nanorods, in agreement with the presence of a great fraction of (100) terrace sites on the surface of cubic gold nanoparticles. PMID:19437963

  4. Optimization of second harmonic generation of gold nanospheres and nanorods in aqueous solution: the dominant role of surface area.

    PubMed

    Ngo, Hoang Minh; Nguyen, Phuong Phong; Ledoux-Rak, Isabelle

    2016-01-28

    Size and shape of gold nanoparticles (AuNPs) have a strong influence on their second order nonlinear optical properties. In this work, we propose a systematic investigation of surface and shape effects in the case of small gold nanoparticles. Colloidal solutions on AuNPs with different sizes and shapes have been synthesized, i.e. nanospheres (diameters 3.0; 11.6; 15.8; 17.4; 20.0 and 43 nm) and nanorods (aspect ratios 1.47; 1.63 and 2.30). The first hyperpolarizability β values of these AuNPs have been measured by harmonic light scattering (HLS) at 1064 nm. For nanospheres and nanorods, we found that their β values are governed by a purely local, dipolar contribution, as confirmed by their surface area dependence. As an important consequence of these surface effects, we have revisited the previously reported aspect ratio dependence of β values for gold nanorods, and evidenced the predominant influence of nanoparticle area over aspect ratio considerations.

  5. Surface modification of adamantane-terminated gold nanoclusters using cyclodextrins.

    PubMed

    Yan, Chunyang; Liu, Chao; Abroshan, Hadi; Li, Zhimin; Qiu, Renhua; Li, Gao

    2016-08-17

    The surface functionality of Au38S2(SAdm)20 nanoclusters (-SAdm = adamantanethiolate) in the presence of α-, β-, and γ-cyclodextrins (CDs) is studied. The supramolecular chemistry and host-guest interactions of CDs and the protecting ligands of nanoclusters are investigated using UV-vis and NMR spectroscopies, MALDI mass spectrometry, and molecular dynamics simulations. In contrast to α- and γ-CDs, the results show that β-CDs are capable of efficiently chemisorbing onto the Au38S2(SAdm)20 nanoclusters to yield Au38S2(SAdm)20-(β-CD)2 conjugates. MD simulations revealed that two -SAdm ligands of the nanoparticle with the least steric hindrance are capable to selectively be accommodated into hydrophobic cavity of β-CDs, as furthermore confirmed by NMR spectroscopy. The conjugates largely improve the stability of the nanoclusters in the presence of strong oxidants (e.g., TBHP). Further, the electrochemical properties of Au38S2(SAdm)20 nanoclusters and Au38S2(SAdm)20-(β-CD)2 conjugates are compared. The charge transfer to the redox probe molecules (e.g., K3Fe(CN)6) in solution was monitored by cyclic voltammetry. It is found that β-CDs act as an umbrella to cover the fragile metal cores of the nanoclusters, thereby blocking direct interaction with destabilizing agents and hence quenching the charge transfer process.

  6. Surface modification of adamantane-terminated gold nanoclusters using cyclodextrins.

    PubMed

    Yan, Chunyang; Liu, Chao; Abroshan, Hadi; Li, Zhimin; Qiu, Renhua; Li, Gao

    2016-08-17

    The surface functionality of Au38S2(SAdm)20 nanoclusters (-SAdm = adamantanethiolate) in the presence of α-, β-, and γ-cyclodextrins (CDs) is studied. The supramolecular chemistry and host-guest interactions of CDs and the protecting ligands of nanoclusters are investigated using UV-vis and NMR spectroscopies, MALDI mass spectrometry, and molecular dynamics simulations. In contrast to α- and γ-CDs, the results show that β-CDs are capable of efficiently chemisorbing onto the Au38S2(SAdm)20 nanoclusters to yield Au38S2(SAdm)20-(β-CD)2 conjugates. MD simulations revealed that two -SAdm ligands of the nanoparticle with the least steric hindrance are capable to selectively be accommodated into hydrophobic cavity of β-CDs, as furthermore confirmed by NMR spectroscopy. The conjugates largely improve the stability of the nanoclusters in the presence of strong oxidants (e.g., TBHP). Further, the electrochemical properties of Au38S2(SAdm)20 nanoclusters and Au38S2(SAdm)20-(β-CD)2 conjugates are compared. The charge transfer to the redox probe molecules (e.g., K3Fe(CN)6) in solution was monitored by cyclic voltammetry. It is found that β-CDs act as an umbrella to cover the fragile metal cores of the nanoclusters, thereby blocking direct interaction with destabilizing agents and hence quenching the charge transfer process. PMID:27498695

  7. Selective electrowinning of mercury from gold cyanide solutions. Report of investigations/1988

    SciTech Connect

    Sheya, S.A.N.; Maysilles, J.H.; Sandberg, R.G.

    1988-01-01

    An investigation was undertaken by the Bureau of Mines to develop techniques for removing mercury from cyanide mill solutions by selective electrowinning to reduce the potential hazards. Sixty-five percent of the mercury was selectively electrowon from synthetic-carbon strip solution at applied potentials of 1.00 to 1.50 V when using a mercury-coated platinum or copper-plate cathode. Increasing the active surface area by using mercury-coated copper wool resulted in up to 96 pct of the mercury being electrowon from mill carbon strip solutions that contained 1.9 to 20 ppm Hg, 20 to 345 ppm Au, and 0.35 to 39.5 ppm Ag. About 98 pct of the silver was electrowon with the mercury onto the mercury cathode. Gold extraction ranged between 0 and 20 pct. Results of the investigation showed that choice of cathode material was critical to the success of the process. Selectivity was not achieved using uncoated steel wool cathodes.

  8. Gold nanomolecules: Developing synthetic protocols, characterization and investigating the ligand effects on structure and properties

    NASA Astrophysics Data System (ADS)

    Nimmala, Praneeth Reddy

    The term "Nano" in chemistry refers to particles/molecules in the size range 1 to 100 nm. Gold nanoparticles were used in ancient times in making decorative glass as they produce vibrant, size dependent, colors upon interaction with light. Gold is a preferred choice of metal for the synthesis of nanoparticles mainly due to its inertness to atmospheric conditions and most chemicals. Gold thiolate nanomolecules, which is the primary focus of this dissertation research, are chemical molecules with a fixed number of gold atoms and organo-thiolate ligands. They are of the form Aux(SR)y and possess molecule-like properties as a result of distinctive quantum confinement effects occurring at the nanoscale size. The optical and electronic properties of these molecules change as a function of "x" and "y" in the formulation Aux(SR) y. The stability of these nanomolecules can be attributed due in part to their symmetrical geometry as evidenced by the X-ray crystallography. Recent research in the field has focused on exploiting the size-dependent properties of gold nanomolecules in applications like nano-electronics, biological sensing and catalysis. But much of the hindrance to these advances come from the lack of established protocols to synthesize monodisperse nanomolecules in high yields. Brust-schiffrin protocol for the synthesis of nanomolecules yields stable products in a two-phase system which can be dried and re-dispersed without affecting the stability. But the protocol has a major drawback of producing a polydisperse mixture of different sizes of nanomolecules. A major portion of my dissertation focuses on addressing this issue of polydispersity of products. In this regard, I have investigated the one-phase synthesis protocol for synthesis of gold-thiolate nanomolecules wherein the gold salt and the capping ligands are essentially dissolved in a single solvent system. This protocol is peculiar in that it yields various sizes which are otherwise not observed.

  9. Influence of cross sectional geometry on surface plasmon polariton propagation in gold nanowires.

    PubMed

    Nauert, Scott; Paul, Aniruddha; Zhen, Yu-Rong; Solis, David; Vigderman, Leonid; Chang, Wei-Shun; Zubarev, Eugene R; Nordlander, Peter; Link, Stephan

    2014-01-28

    We investigated the effects of cross sectional geometry on surface plasmon polariton propagation in gold nanowires (NWs) using bleach-imaged plasmon propagation and electromagnetic simulations. Chemically synthesized NWs have pentagonally twinned crystal structures, but recent advances in synthesis have made it possible to amplify this pentagonal shape to yield NWs with a five-pointed-star cross section and sharp end tips. We found experimentally that NWs with a five-pointed-star cross section, referred to as SNWs, had a shorter propagation length for surface plasmon polaritons at 785 nm, but a higher effective incoupling efficiency compared to smooth NWs with a pentagonal cross section, labeled as PNWs. Electromagnetic simulations revealed that the electric fields were localized at the sharp ridges of the SNWs, leading to higher absorptive losses and hence shorter propagation lengths compared to PNWs. On the other hand, scattering losses were found to be relatively uncorrelated with cross sectional geometry, but were strongly dependent on the plasmon mode excited. Our results provide insight into the shape-dependent waveguiding properties of chemically synthesized metal NWs and the mode-dependent loss mechanisms that govern surface plasmon polariton propagation. PMID:24308802

  10. Single-step, high yield synthesis of gold nanoworms and their surface enhanced Raman scattering properties

    NASA Astrophysics Data System (ADS)

    Ahmed, Waqqar; van Ruitenbeek, Jan M.

    Rod-shaped gold nanoparticles have attracted enormous attention owing to their interesting optical properties arising from the surface plasmon resonances. Slight deviation from the rod morphology can markedly change the optical properties. For-example, worm-shaped gold nanoparticles can have more than two plasmon peaks. Furthermore, they show much higher local field enhancements as compared to their rod-shaped counterparts. We have devised a simple seedless, high-yield protocol for the synthesis of gold nanoworms (NWs). NWs were grown simply by reducing HAuCl4 with ascorbic acid in a high pH reaction medium, and in the presence of growth directional agents, cetyltrimethylammonium bromide and AgNO3. In contrast to the seed-mediated growth of gold nanorods where a seed grows into a rod, NWs grow by oriental attachment of nanoparticles. By varying different reaction parameters we were able to control the length of NWs from a few nanometers to micrometers. Furthermore, the aspect ratio can also be tuned over a wide range. Gold NWs show excellent surface enhanced Raman scattering (SERS) properties. Ultra-low concentrations of various target molecules were detected using NWs based SERS substrates.

  11. Investigation of the influence of protein corona composition on gold nanoparticle bioactivity using machine learning approaches.

    PubMed

    Papa, E; Doucet, J P; Sangion, A; Doucet-Panaye, A

    2016-07-01

    The understanding of the mechanisms and interactions that occur when nanomaterials enter biological systems is important to improve their future use. The adsorption of proteins from biological fluids in a physiological environment to form a corona on the surface of nanoparticles represents a key step that influences nanoparticle behaviour. In this study, the quantitative description of the composition of the protein corona was used to study the effect on cell association induced by 84 surface-modified gold nanoparticles of different sizes. Quantitative relationships between the protein corona and the activity of the gold nanoparticles were modelled by using several machine learning-based linear and non-linear approaches. Models based on a selection of only six serum proteins had robust and predictive results. The Projection Pursuit Regression method had the best performances (r(2) = 0.91; Q(2)loo = 0.81; r(2)ext = 0.79). The present study confirmed the utility of protein corona composition to predict the bioactivity of gold nanoparticles and identified the main proteins that act as promoters or inhibitors of cell association. In addition, the comparison of several techniques showed which strategies offer the best results in prediction and could be used to support new toxicological studies on gold-based nanomaterials.

  12. Investigation of the influence of protein corona composition on gold nanoparticle bioactivity using machine learning approaches.

    PubMed

    Papa, E; Doucet, J P; Sangion, A; Doucet-Panaye, A

    2016-07-01

    The understanding of the mechanisms and interactions that occur when nanomaterials enter biological systems is important to improve their future use. The adsorption of proteins from biological fluids in a physiological environment to form a corona on the surface of nanoparticles represents a key step that influences nanoparticle behaviour. In this study, the quantitative description of the composition of the protein corona was used to study the effect on cell association induced by 84 surface-modified gold nanoparticles of different sizes. Quantitative relationships between the protein corona and the activity of the gold nanoparticles were modelled by using several machine learning-based linear and non-linear approaches. Models based on a selection of only six serum proteins had robust and predictive results. The Projection Pursuit Regression method had the best performances (r(2) = 0.91; Q(2)loo = 0.81; r(2)ext = 0.79). The present study confirmed the utility of protein corona composition to predict the bioactivity of gold nanoparticles and identified the main proteins that act as promoters or inhibitors of cell association. In addition, the comparison of several techniques showed which strategies offer the best results in prediction and could be used to support new toxicological studies on gold-based nanomaterials. PMID:27329717

  13. Adhesion and Atomic Structures of Gold on Ceria Nanostructures: The Role of Surface Structure and Oxidation State of Ceria Supports.

    PubMed

    Lin, Yuyuan; Wu, Zili; Wen, Jianguo; Ding, Kunlun; Yang, Xiaoyun; Poeppelmeier, Kenneth R; Marks, Laurence D

    2015-08-12

    We report an aberration-corrected electron microscopy analysis of the adhesion and atomic structures of gold nanoparticle catalysts supported on ceria nanocubes and nanorods. Under oxidative conditions, the as-prepared gold nanoparticles on the ceria nanocubes have extended atom layers at the metal-support interface. In contrast, regular gold nanoparticles and rafts are present on the ceria nanorod supports. Under the reducing conditions of water-gas shift reaction, the extended gold atom layers and rafts vanish. In addition, the gold particles on the nanocubes change in morphology and increase in size while those on the nanorods are almost unchanged. The size, morphology, and atomic interface structures of gold strongly depend on the surface structures of ceria supports ((100) surface versus (111) surface) and the reaction environment (reductive versus oxidative). These findings provide insights into the deactivation mechanisms and the shape-dependent catalysis of oxide supported metal catalysts.

  14. Template-stripped, ultraflat gold surfaces with coplanar, embedded titanium micropatterns.

    PubMed

    Venkataraman, Nagaiyanallur V; Pei, Jia; Cremmel, Clément V M; Rossi, Antonella; Spencer, Nicholas D

    2013-08-01

    Ultraflat gold surfaces with coplanar, embedded titanium micropatterns, exhibiting extremely low roughness over the entire surface, have been obtained by a modified template-stripping procedure. Titanium is deposited onto photolithographically predefined regions of a silicon template. Following photoresist lift-off, the entire surface is backfilled with gold, template stripping is conducted, and an ultraflat micropatterned surface is revealed. Atomic force microscopy confirms a roughness of <0.5 nm RMS on both Ti and Au regions, with a topographically indistinguishable gold-titanium interface. Detailed surface-chemical maps of the patterned surfaces have been obtained by means of imaging X-ray photoelectron spectroscopy (i-XPS) as well as time-of-flight secondary-ion mass spectrometry (ToF-SIMS). They confirm the presence of well-separated Ti and Au regions, with a chemical contrast that is sharp (as determined by ToF-SIMS) and complete (as determined by i-XPS) across the Ti-Au interface. Thus, a surface has been fabricated that is physically homogeneous down to the nanoscale incorporating chemically distinct micropatterns consisting of two different metals, with totally contrasting surface chemistries.

  15. Influence of surface charge on the rate, extent, and structure of adsorbed Bovine Serum Albumin to gold electrodes.

    PubMed

    Beykal, Burcu; Herzberg, Moshe; Oren, Yoram; Mauter, Meagan S

    2015-12-15

    The objective of this work is to investigate the rate, extent, and structure of amphoteric proteins with charged solid surfaces over a range of applied potentials and surface charges. We use Electrochemical Quartz Crystal Microbalance with Dissipation Monitoring (E-QCM-D) to investigate the adsorption of amphoteric Bovine Serum Albumin (BSA) to a gold electrode while systematically varying the surface charge on the adsorbate and adsorbent by manipulating pH and applied potential, respectively. We also perform cyclic voltammetry-E-QCM-D on an adsorbed layer of BSA to elucidate conformational changes in response to varied applied potentials. We confirm previous results demonstrating that increasing magnitude of applied potential on the gold electrode is positively correlated with increasing mass adsorption when the protein and the surface are oppositely charged. On the other hand, we find that the rate of BSA adsorption is not governed by simple electrostatics, but instead depends on solution pH, an observation not well documented in the literature. Cyclic voltammetry with simultaneous E-QCM-D measurements suggest that BSA protein undergoes a conformational change as the surface potential varies.

  16. The surface plasmon modes of self-assembled gold nanocrystals

    NASA Astrophysics Data System (ADS)

    Barrow, Steven J.; Wei, Xingzhan; Baldauf, Julia S.; Funston, Alison M.; Mulvaney, Paul

    2012-12-01

    The three-dimensional (3D) self-assembly of nanocrystals constitutes one of the most important challenges in materials science. A key milestone is the synthesis of simple, regular structures, such as platonic solids, composed of nanocrystal building blocks. Such objects are predicted to have unique optical and electronic properties such as polarization-independent light-scattering and intense local fields. Here we present a two-stage process for fabricating well-defined and highly symmetric, 3D gold nanocrystal structures, including tetrahedra, 3D pentamers and 3D hexamers. Polarized scattering spectra are used to elucidate the plasmon modes present in each structure, and these are compared with computational models. We conclude that self-assembly of highly symmetric, polarization-independent structures with interparticle spacings of order 0.5 nm can now be fabricated. Drastically, enhanced local fields, 1000 times higher than the incident field strength, are produced within the interstices. Fano resonances are generated if the symmetry is broken.

  17. Switching of localized surface plasmon resonance of gold nanoparticles on a GeSbTe film mediated by nanoscale phase change and modification of surface morphology

    SciTech Connect

    Hira, T.; Homma, T.; Uchiyama, T.; Kuwamura, K.; Saiki, T.

    2013-12-09

    As a platform for active nanophotonics, localized surface plasmon resonance (LSPR) switching via interaction with a chalcogenide phase change material (GeSbTe) was investigated. We performed single-particle spectroscopy of gold nanoparticles placed on a GeSbTe thin film. By irradiation with a femtosecond pulsed laser for amorphization and a continuous wave laser for crystallization, significant switching behavior of the LSPR band due to the interaction of GeSbTe was observed. The switching mechanism was explained in terms of both a change in the refractive index and a modification of surface morphology accompanying volume expansion and reduction of GeSbTe.

  18. Watching single gold nanorods grow.

    PubMed

    Wei, Zhongqing; Qi, Hua; Li, Min; Tang, Bochong; Zhang, Zhengzheng; Han, Ruiling; Wang, Jiaojiao; Zhao, Yuliang

    2012-05-01

    The consecutive evolution process of single gold nanorods is monitored using atomic force microscopy (AFM). The single-crystal gold nanorods investigated are grown directly on surfaces to which gold seed particles are covalently linked. The growth kinetics for single nanorods is derived from the 3D information recorded by AFM. A better understanding of the seed-mediated growth mechanism may ultimately lead to the direct growth of aligned nanorods on surfaces. PMID:22378704

  19. Surface plasmon resonance of silver and gold nanoparticles in the proximity of graphene studied using the discrete dipole approximation method.

    PubMed

    Amendola, Vincenzo

    2016-01-21

    The integration of silver and gold nanoparticles with graphene is frequently sought for the realization of hybrid materials with superior optical, photoelectric and photocatalytic performances. A crucial aspect for these applications is how the surface plasmon resonance of metal nanoparticles is modified after assembly with graphene. Here, we used the discrete dipole approximation method to study the surface plasmon resonance of silver and gold nanoparticles in the proximity of a graphene flake or embedded in graphene structures. Surface plasmon resonance modifications were investigated for various shapes of metal nanoparticles and for different morphologies of the nanoparticle-graphene nanohybrids, in a step-by-step approach. Calculations show that the surface plasmon resonance of Ag nanoparticles is quenched in nanohybrids, whereas either surface plasmon quenching or enhancement can be obtained with Au nanoparticles, depending on the configuration adopted. However, graphene effects on the surface plasmon resonance are rapidly lost already at a distance of the order of 5 nm. These results provide useful indications for characterization and monitoring the synthesis of hybrid nanostructures, as well as for the development of hybrid metal nanoparticle/graphene nanomaterials with desired optical properties.

  20. Impact of surface steps and oxygen pre-coverage on the adsorption of methylamine on gold.

    PubMed

    Lewoczko, April D; BelBruno, Joseph J

    2013-04-01

    Using density functional theory calculations, we report on the adsorption of methylamine on gold and compare its adsorption to a selection of alkylamines, methanol and methanethiol. On the (111) surface, the amines, thiol and alcohol bind in the ontop site with a preference over hollow and bridge sites of 0.3 eV, 0.2 eV and 0.1 eV for methylamine, methanethiol and methanol, respectively. The effect of steps is considered on the (211) surface of gold and we find that methylamine adsorbs 0.2 eV more strongly in the step ontop site of the surface than on the (111) surface. For oxygen atom pre-coverages of 0.04-0.25 ML on the (111) surface, we find cooperative adsorption of amines and oxygen atoms. The energetic costs of adsorbate tilt from the surface normal and of rotation about the gold-heteroatom bond are compared among the studied surfaces and conditions.

  1. Effect of Pore Size and Film Thickness on Gold-Coated Nanoporous Anodic Aluminum Oxide Substrates for Surface-Enhanced Raman Scattering Sensor.

    PubMed

    Kassu, Aschalew; Farley, Carlton; Sharma, Anup; Kim, Wonkyu; Guo, Junpeng

    2015-11-30

    A sensitive surface enhanced Raman scattering chemical sensor is demonstrated by using inexpensive gold-coated nanoporous anodic aluminum oxide substrates. To optimize the performance of the substrates for sensing by the Surface-enhanced Raman scattering (SERS) technique, the size of the nanopores is varied from 18 nm to 150 nm and the gold film thickness is varied from 30 nm to 120 nm. The sensitivity of gold-coated nanoporous surface enhanced Raman scattering sensor is characterized by detecting low concentrations of Rhodamine 6G laser dye molecules. The morphology of the SERS substrates is characterized by atomic force microscopy. Optical properties of the nanoporous SERS substrates including transmittance, reflectance, and absorbance are also investigated. Relative signal enhancement is plotted for a range of substrate parameters and a detection limit of 10(-6) M is established.

  2. Effect of Pore Size and Film Thickness on Gold-Coated Nanoporous Anodic Aluminum Oxide Substrates for Surface-Enhanced Raman Scattering Sensor.

    PubMed

    Kassu, Aschalew; Farley, Carlton; Sharma, Anup; Kim, Wonkyu; Guo, Junpeng

    2015-01-01

    A sensitive surface enhanced Raman scattering chemical sensor is demonstrated by using inexpensive gold-coated nanoporous anodic aluminum oxide substrates. To optimize the performance of the substrates for sensing by the Surface-enhanced Raman scattering (SERS) technique, the size of the nanopores is varied from 18 nm to 150 nm and the gold film thickness is varied from 30 nm to 120 nm. The sensitivity of gold-coated nanoporous surface enhanced Raman scattering sensor is characterized by detecting low concentrations of Rhodamine 6G laser dye molecules. The morphology of the SERS substrates is characterized by atomic force microscopy. Optical properties of the nanoporous SERS substrates including transmittance, reflectance, and absorbance are also investigated. Relative signal enhancement is plotted for a range of substrate parameters and a detection limit of 10(-6) M is established. PMID:26633402

  3. Effect of Pore Size and Film Thickness on Gold-Coated Nanoporous Anodic Aluminum Oxide Substrates for Surface-Enhanced Raman Scattering Sensor

    PubMed Central

    Kassu, Aschalew; Farley, Carlton; Sharma, Anup; Kim, Wonkyu; Guo, Junpeng

    2015-01-01

    A sensitive surface enhanced Raman scattering chemical sensor is demonstrated by using inexpensive gold-coated nanoporous anodic aluminum oxide substrates. To optimize the performance of the substrates for sensing by the Surface-enhanced Raman scattering (SERS) technique, the size of the nanopores is varied from 18 nm to 150 nm and the gold film thickness is varied from 30 nm to 120 nm. The sensitivity of gold-coated nanoporous surface enhanced Raman scattering sensor is characterized by detecting low concentrations of Rhodamine 6G laser dye molecules. The morphology of the SERS substrates is characterized by atomic force microscopy. Optical properties of the nanoporous SERS substrates including transmittance, reflectance, and absorbance are also investigated. Relative signal enhancement is plotted for a range of substrate parameters and a detection limit of 10−6 M is established. PMID:26633402

  4. Wrinkled nanoporous gold films with ultrahigh surface-enhanced Raman scattering enhancement.

    PubMed

    Zhang, Ling; Lang, Xingyou; Hirata, Akihiko; Chen, Mingwei

    2011-06-28

    Amplified by plasomonic nanostructured metals, Raman intensity of organic molecules and biomolecules can be dramatically improved, particularly at "hot spots" where intense electromagnetic fields are produced in the vicinity of narrow nanogaps between metallic nanostructures. Therefore, developing new substrates with a high density of "hot spots" has been the recent topic of intense study. Here we report wrinkled nanoporous gold films that contain abundant Raman-active nanogaps produced by deformation and fracture of nanowire-like gold ligaments. This novel nanostructure yields ultrahigh surface enhanced Raman scattering for molecule detection.

  5. Adsorption and dehydrogenation of 2-propanol on the surface of γ-Al2O3-supported gold

    NASA Astrophysics Data System (ADS)

    Martinez-Ramirez, Z.; Gonzalez-Calderon, J. A.; Almendarez-Camarillo, A.; Fierro-Gonzalez, J. C.

    2012-08-01

    The adsorption and reactions of 2-propanol on γ-Al2O3 and γ-Al2O3-supported gold samples were investigated by infrared (IR) spectroscopy, modulated differential scanning calorimetry (MDSC) and mass spectrometry. Adsorption of the alcohol on the samples at room temperature led to formation of molecularly adsorbed 2-propanol and 2-propoxide species bonded to Al3+ sites. Treatment of γ-Al2O3 after alcohol adsorption in flowing He from 25 to 300 °C led to 2-propanol desorption, without evidence of surface reactions. In contrast, when supported gold samples were exposed to the same thermal treatment, formation of acetone and H2 was observed by mass spectra of the effluent gases from the flow reactor. Concomitantly, IR spectra of the samples showed the appearance of a band at 1698 cm- 1, assigned to νCO vibrations of adsorbed acetone. The formation of acetone occurred by the dehydrogenation of 2-propoxide species bonded to Al3+ sites, as evidenced by (a) the decrease in the intensities of their IR bands and (b) the presence of a MDSC peak at approximately the same temperature as that at which acetone was formed and the 2-propoxide species were consumed. It is proposed that gold particles on the γ-Al2O3 surface facilitate breaking of the β-Csbnd H bond of neighboring surface 2-propoxide species to give acetone. Our results emphasize the bifunctional character of supported gold catalysts for the dehydrogenation of alcohols.

  6. Nonionic Brij surfactant-mediated synthesis of raspberry-like gold nanoparticles with high surface area.

    PubMed

    Jang, Min Hoon; Kim, Jin Kyung; Yoo, Hyojong

    2012-05-01

    We report a rapid, simple, single-step, and high-yielding solution-phase synthesis of raspberry-like gold nanoparticles (Au RLNPs) with rich edges and high surface areas. Au RLNPs were synthesized through the reduction of HAuCl4 simply mediated by nonionic Brij surfactant in basic conditions without any other reducing agents or organic molecules. The synthesized nanoparticles possessed high surface areas and were stable in basic or neutral conditions, which are potentially useful structural factors for the applications. The unique, highly red-shifted surface plasmon resonances (SPRs) of Au RLNPS originate from their rough, raspberry-like surfaces. The sizes of Au RLNPs were controllable by varying the amounts of NaOH and HAuCl4. However, there are very few reported facile syntheses of size-controlled multi-branched gold nanoparticles simply mediated by surfactant without any other reducing agents or organic molecules.

  7. Nonlinear effects in propagation of long-range surface plasmon polaritons in gold strip waveguides

    NASA Astrophysics Data System (ADS)

    Lysenko, Oleg; Bache, Morten; Malureanu, Radu; Lavrinenko, Andrei

    2016-04-01

    This paper is devoted to experimental and theoretical studies of nonlinear propagation of a long-range surface plasmon polariton (LRSPP) in gold strip waveguides. The plasmonic waveguides are fabricated in house, and contain a gold layer, tantalum pentoxide adhesion layers, and silicon dioxide cladding. The optical characterization was performed using a high power picosecond laser at 1064 nm. The experiments reveal two nonlinear optical effects: nonlinear power transmission and spectral broadening of the LRSPP mode in the waveguides. Both nonlinear optical effects depend on the gold layer thickness. The theoretical model of these effects is based on the third-order susceptibility of the constituent materials. The linear and nonlinear parameters of the LRSPP mode are obtained, and the nonlinear Schrödinger equation is solved. The dispersion length is much larger than the waveguides length, and the chromatic dispersion does not affect the propagation of the plasmonic mode. We find that the third-order susceptibility of the gold layer has a dominant contribution to the effective third-order susceptibility of the LRSPP mode. The real part of the effective third-order susceptibility leads to the observed spectral broadening through the self-phase modulation effect, and its imaginary part determines the nonlinear absorption parameter and leads to the observed nonlinear power transmission. The experimental values of the third-order susceptibility of the gold layers are obtained. They indicate an effective enhancement of the third-order susceptibility for the gold layers, comparing to the bulk gold values. This enhancement is explained in terms of the change of the electrons motion.

  8. Off-Resonant Optical Excitation of Gold Nanorods: Nanoscale Imprint of Polarization Surface Charge Distribution.

    PubMed

    Deeb, Claire; Zhou, Xuan; Gérard, Davy; Bouhelier, Alexandre; Jain, Prashant K; Plain, Jérôme; Soppera, Olivier; Royer, Pascal; Bachelot, Renaud

    2011-01-01

    We report on the nanoscale optical characterization of gold nanorods irradiated out of their plasmonic resonance. Our approach is based on the reticulation of a photopolymerizable formulation locally triggered by enhanced electromagnetic fields. The tiny local field enhancement stems from the surface polarization charges associated with the electric field discontinuity at the metal/dielectric interface. This allows us to get a nanoscale signature of the spatial distribution of the surface charge density in metallic nanoparticles irradiated off-resonance.

  9. Single-particle Raman measurements of gold nanoparticles used in surface-enhanced Raman scattering (SERS)-based sandwich immunoassays

    NASA Astrophysics Data System (ADS)

    Park, Hye-Young; Lipert, Robert J.; Porter, Marc D.

    2004-12-01

    The effect of particle size on the intensity of surface-enhanced Raman scattering (SERS) using labeled gold nanoparticles has been investigated. Two sets of experiments were preformed, both of which employed 632.8-nm laser excitation. The first entailed a sandwich immunoassay in which an antibody coupled to a smooth gold substrate selectively captured free-prostate specific antigen (f-PSA) from buffered aqueous solutions. The presence of captured f-PSA was then detected by the response of Raman-labeled immunogold nanoparticles with nominal diameters of 30, 40, 50, 60, or 80 nm. The resulting SERS responses were correlated to particle densities, which were determined by atomic force microscopy, by calculating the average response per particle after accounting for differences in particle surface area. This analysis showed that the magnitude of the SERS response increased with increasing particle size. The second set of experiments examined the response of individual nanoparticles. These experiments differed in that the labeled nanoparticles were coupled to the smooth gold substrate by an amine-terminated thiolate, yielding a much smaller average separation between the particles and substrate. The results revealed that particles with a diameter of ~70 nm exhibited the largest enhancement. The origin of the difference in the two sets of findings, which is attributed to the distance dependence of the plasmon coupling between the nanoparticles and underlying substrate, is briefly discussed.

  10. Spectroscopic and microscopic investigations of phthalocyanine aggregates on Gold(111)

    NASA Astrophysics Data System (ADS)

    Nishida, Krista Rachel Akiko

    Self-assembled organic pi systems are of interest because of their potential applications in light harvesting and electron transfer. Phthalocyanines (Pc) demonstrate desirable photonic and electronic properties, thus making them excellent candidates for functional nanostructures. The specific focus of this research has been the nanoscale aggregation of a metal-free organic dye, tetrasulfonic acid phthalocyanine (TSPc) and includes the use of UV-visible Spectroscopy, Resonance Light Scattering Spectroscopy (RLS), X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and ambient and ultra-high-vacuum Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS). The UV-visible absorption studies show that TSPc aggregates upon dissolution in water and obeys Beer's Law within the concentration range of 10 -7M to 10-4M, indicating that TSPc concentration has no further effect on aggregation in aqueous solution. In addition, both ionic strength in NaCl and pH changes in the presence of NaOH, HCl or acetic acid (HAc) do affect aggregation. The RSL studies confirm these effects of pH only in the presence of HAc. The XPS studies show that the ratio of non-protonated to protonated nitrogens does not change with decreasing solution pH. STM images of TSPc deposited from pH<1 solutions reveal ordered branched web-like assemblies hundreds of nanometers in length, generally 2 nm tall and having variable widths. STM imaging shows TSPc aggregates decrease in order as pH increases. STM images of TSPc deposited from solutions with pH>10 show monolayer coverage of TSPc in salt form. High-resolution UHV-STM images of TSPc aggregates deposited from pH 0 solution on Au(111) reveal detailed coherent columnar architecture with the phthalocyanine macrocycles orientated parallel to the substrate surface. OMTS was used to identify the HOMO and LUMO of the TSPc aggregates and the results are contrasted with the same molecular states in unsubstituted metallated

  11. 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.

  12. Self-Catalyzed Carbon Dioxide Adsorption by Metal-Organic Chains on Gold Surfaces

    SciTech Connect

    Feng, Min; Sun, Hao; Zhao, Jin; Petek, Hrvoje

    2014-08-26

    Efficient capture of CO2 by chemical means requires a microscopic understanding of the interactions of the molecule-substrate bonding and adsorption-induced collective phenomena. By molecule-resolved imaging with scanning tunneling microscopy (STM), we investigate self-catalyzed CO2 adsorption on one-dimensional (1D) substrates composed of self-assembled metal-organic chains (MOCs) supported on gold surfaces. CO2 adsorption turns on attractive interchain interactions, which induce pronounced surface structural changes; the initially uniformly dispersed chains gather into close packed bundles, which are held together by highly ordered, single molecule wide CO2 ranks. CO2 molecules create more favorable adsorption sites for further CO2 adsorption by mediating the interchain attraction, thereby self-catalyzing their capture. The release of CO2 molecules by thermal desorption returns the MOCs to their original structure, indicating that the CO2 capture and release are reversible processes. The real space microscopic characterization of the self-catalyzed CO2 adsorption on 1D substrates could be exploited as platform for design of molecular materials for CO2 capture and reduction.

  13. Surface-enhanced Raman spectroscopic detection of Bacillus subtilis spores using gold nanoparticle based substrates.

    PubMed

    Cheng, Han-Wen; Chen, Yuan-Yuan; Lin, Xin-Xin; Huan, Shuang-Yan; Wu, Hai-Long; Shen, Guo-Li; Yu, Ru-Qin

    2011-11-30

    The detection of bacterial spores requires the capability of highly sensitive and biocompatible probes. This report describes the findings of an investigation of surface-enhanced Raman spectroscopic (SERS) detection of Bacillus subtilis spores using gold-nanoparticle (Au NP) based substrates as the spectroscopic probe. The SERS substrates are shown to be highly sensitive for the detection of B. subtilis spores, which release calcium dipicolinate (CaDPA) as a biomarker. The SERS bands of CaDPA released from the spores by extraction using nitric acid provide the diagnostic signal for the detection, exhibiting a limit of detection (LOD) of 1.5×10(9) spores L(-1) (or 2.5×10(-14) M). The LOD for the Au NP based substrates is quite comparable with that reported for Ag nanoparticle based substrates for the detection of spores, though the surface adsorption equilibrium constant is found to be smaller by a factor of 1-2 orders of magnitude than the Ag nanoparticle based substrates. The results have also revealed the viability of SERS detection of CaDPA released from the spores under ambient conditions without extraction using any reagents, showing a significant reduction of the diagnostic peak width for the detection. These findings have demonstrated the viability of Au NP based SERS substrates for direct use with high resolution and sensitivity as a biocompatible probe for the detection of bacterial spores.

  14. Experimental investigations of creep in gold RF-MEMS microstructures

    NASA Astrophysics Data System (ADS)

    Somà, Aurelio; De Pasquale, Giorgio; Saleem, Muhammad Mubasher

    2015-05-01

    Lifetime prediction and reliability evaluation of micro-electro-mechanical systems (MEMS) are influenced by permanent deformations caused by plastic strain induced by creep. Creep in microstructures becomes critical in those applications where permanent loads persist for long times and thermal heating induces temperature increasing respect to the ambient. Main goal of this paper is to investigate the creep mechanism in RF-MEMS microstructures by means of experiments. This is done firstly through the detection of permanent deformation of specimens and, then, by measuring the variation of electro-mechanical parameters (resonance frequency, pull-in voltage) that provide indirect evaluation of mechanical stiffness alteration from creep. To prevent the errors caused be cumulative heating of samples and dimensional tolerances, three specimens with the same nominal geometry have been tested per each combination of actuation voltage and temperature. Results demonstrated the presence of plastic deformation due to creep, combined with a component of reversible strain linked to the viscoelastic behavior of the material.

  15. Deep eutectic solvents for the self-assembly of gold nanoparticles: a SAXS, UV-Vis, and TEM investigation.

    PubMed

    Raghuwanshi, Vikram Singh; Ochmann, Miguel; Hoell, Armin; Polzer, Frank; Rademann, Klaus

    2014-06-01

    In this work, we report the formation and growth mechanisms of gold nanoparticles (AuNPs) in eco-friendly deep eutectic solvents (DES; choline chloride and urea). AuNPs are synthesized on the DES surface via a low-energy sputter deposition method. Detailed small angle X-ray scattering (SAXS), UV-Vis, and cryogenic transmission electron microscopy (cryo-TEM) investigations show the formation of AuNPs of 5 nm diameter. Data analysis reveals that for a prolonged gold-sputtering time there is no change in the size of the particles. Only the concentration of AuNPs increases linearly in time. More surprisingly, the self-assembly of AuNPs into a first and second shell ordered system is observed directly by in situ SAXS for prolonged gold-sputtering times. The self-assembly mechanism is explained by the templating nature of DES combined with the equilibrium between specific physical interaction forces between the AuNPs. A disulfide-based stabilizer, bis((2-mercaptoethyl)trimethylammonium) disulfide dichloride, was applied to suppress the self-assembly. Moreover, the stabilizer even reverses the self-assembled or agglomerated AuNPs back to stable 5 nm individual particles as directly evidenced by UV-Vis. The template behavior of DES is compared to that of nontemplating solvent castor oil. Our results will also pave the way to understand and control the self-assembly of metallic and bimetallic nanoparticles. PMID:24814886

  16. In situ controlled sputtering deposition of gold nanoparticles on MnO2 nanorods as surface-enhanced Raman scattering substrates for molecular detection.

    PubMed

    Jiang, Tao; Zhang, Li; Jin, Han; Wang, Xiaolong; Zhou, Jun

    2015-04-28

    Single-crystal tetragonal α-MnO2 nanorods with different amounts of gold nanoparticles (NPs) attached were successfully prepared by a facile sputtering deposition technique. Initially, the morphology and crystal structure of the bare α-MnO2 nanorods synthesized via a hydrothermal approach were investigated. Then, the amount of gold NPs at different sputtering times was analyzed. It was confirmed that the amount of the decorated gold NPs increased with the lengthening of the sputtering time until they completely covered the α-MnO2 nanorods. Theoretical calculation results indicated the advantages of the composite structure by showing the enhanced electromagnetic fields around both the bare α-MnO2 nanorods and the gold NP decorated ones. The surface-enhanced Raman scattering (SERS) efficiency of these nanocomposites was evaluated using methylene blue and 4-mercaptobenzoic acid as Raman probe molecules. It was found that the SERS intensity of the substrates strongly depended on the degree of aggregation of the gold NPs. Uniform SERS signals across the entire surface of these samples were obtained. Moreover, a typical chemical toxin, methyl parathion, was effectively detected over a broad concentration range from 1 × 10(-3) to 100 ppm using the gold NP decorated α-MnO2 nanorods, suggesting this hybrid structure is highly valuable for further applications on the rapid detection of organic environmental pollutants.

  17. Laser irradiation—an effective means to create an anti-tarnishing surface on purple gold substrate

    NASA Astrophysics Data System (ADS)

    Jiang, Huixin; Li, Zhongli; Hong, Liang; Liu, Zhaolin; Guo, Bing

    2004-02-01

    Purple gold (PG) has emerged as a colored gold product for use in decorating jewelry items. However, PG possesses little chemical stability in the ambient environments and undergoes noticeable decolorizing in a few months. This work uses the 4th harmonic Nd:YAG laser as a new measure instead of conventional coating technique to generate an anti-tarnishing layer on PG. The laser beam brings about instant melting at the irradiated surface of PG and re-solidification of the melt leads to a dense overlaying thin layer, of which the structure is contingent on the laser parameters and thermodynamic properties of the treated surface. This thin layer possesses very different properties from the non-irradiated surface. An investigation of laser-irradiation effect by varying its scanning speed and scanning repetitions were carried out to determine an optimal treatment condition. In conjunction with this investigation, scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) were employed as well. The dependence of surface morphology and composition on the setting of parameters has been discovered through this work.

  18. Regenerating Titanium Ventricular Assist Device Surfaces after Gold/ Palladium Coating for Scanning Electron Microscopy

    PubMed Central

    Achneck, Hardean E.; Serpe, Michael J; Jamiolkowski, Ryan; Eibest, Leslie M.; Craig, Stephen L.; Lawson, Jeffrey H.

    2014-01-01

    Titanium is one of the most commonly used materials for implantable devices in human s. Scanning electron microscopy (SEM) serves as an important tool for imaging titanium surfaces and analyzing cells and other organic matter adhering to titanium implants. However, high-vacuum SEM imaging of a non-conductive sample requires a conductive coating on the surface. A gold/ palladium coating is commonly used and to date no method has been described to ‘clean’ such gold/ palladium covered surfaces for repeated experiments without etching the titanium itself. This constitutes a major problem with titanium based implantable devices which are very expensive and thus in short supply. Our objective was to devise a protocol to regenerate titanium surfaces after SEM analysis. In a series of experiments, titanium samples from implantable cardiac assist devices were coated with fibronectin, seeded with cells and then coated with gold/palladium for SEM analysis. X-ray photoelectron spectroscopy spectra were obtained before and after five different cleaning protocols. Treatment with aqua regia (a 1:3 solution of concentrated nitric and hydrochloric acid), with or without ozonolysis, followed by sonication in soap solution and sonication in deionized water, allowed regenerating titanium surfaces to their original state. Atomic force microscopy confirmed that the established protocol did not alter the titanium microstructure. The protocol described herein is applicable to almost all titanium surfaces used in biomedical sciences and because of its short exposure time to aqua regia, will likely work for many titanium alloys as well. PMID:19642216

  19. Catalytic and surface properties of nanocrystalline gold water gas shift catalysts

    NASA Astrophysics Data System (ADS)

    Kim, Chang Hwan

    A series of CeO2 supported gold catalysts were prepared and found to possess a high activities for the water gas shift reaction (WGS), a critical step in the production of H2 for use in petroleum refining, chemicals synthesis, and proton exchange membrane fuel cells. The deposition-precipitation method was employed in synthesizing these highly active, nanocrystalline gold catalysts. X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and dynamic sorption analyses were performed to characterize the gold catalysts. While some of these catalysts were initially four times more active than a commercial Cu-based catalyst, they were susceptible to deactivation. Characterization using techniques including temperature programmed oxidation, XPS, and FT-IR indicated that the deactivation was caused primarily by blockage of the active sites by carbonates and/or formates. Formation of these carbonaceous species appeared to be facilitated by oxygen deficient sites on the ceria surface and may have been associated with hydroxyl groups formed on the nanocrystalline gold particles under the H2 rich conditions. The deactivation could be managed by conditioning the CeO2 surface or adding constituents to minimize oxygen deficiency. The catalytic activity was fully recovered by calcining the deactivated materials in flowing air at elevated temperatures. The gold catalyst was washcoated onto microporous Fe-Al alloy foams for use in a micro-channel WGS reactor. The performance of these coated foams was inferior to that of the powder catalyst; however, a two stage micro-channel WGS reactor employing the gold catalyst was sufficient for a 100 W fuel processor system.

  20. Effects of surface charges of gold nanoclusters on long-term in vivo biodistribution, toxicity, and cancer radiation therapy

    PubMed Central

    Wang, Jun-Ying; Chen, Jie; Yang, Jiang; Wang, Hao; Shen, Xiu; Sun, Yuan-Ming; Guo, Meili; Zhang, Xiao-Dong

    2016-01-01

    Gold nanoclusters (Au NCs) have exhibited great advantages in medical diagnostics and therapies due to their efficient renal clearance and high tumor uptake. The in vivo effects of the surface chemistry of Au NCs are important for the development of both nanobiological interfaces and potential clinical contrast reagents, but these properties are yet to be fully investigated. In this study, we prepared glutathione-protected Au NCs of a similar hydrodynamic size but with three different surface charges: positive, negative, and neutral. Their in vivo biodistribution, excretion, and toxicity were investigated over a 90-day period, and tumor uptake and potential application to radiation therapy were also evaluated. The results showed that the surface charge greatly influenced pharmacokinetics, particularly renal excretion and accumulation in kidney, liver, spleen, and testis. Negatively charged Au NCs displayed lower excretion and increased tumor uptake, indicating a potential for NC-based therapeutics, whereas positively charged clusters caused transient side effects on the peripheral blood system. PMID:27555769

  1. Effects of surface charges of gold nanoclusters on long-term in vivo biodistribution, toxicity, and cancer radiation therapy.

    PubMed

    Wang, Jun-Ying; Chen, Jie; Yang, Jiang; Wang, Hao; Shen, Xiu; Sun, Yuan-Ming; Guo, Meili; Zhang, Xiao-Dong

    2016-01-01

    Gold nanoclusters (Au NCs) have exhibited great advantages in medical diagnostics and therapies due to their efficient renal clearance and high tumor uptake. The in vivo effects of the surface chemistry of Au NCs are important for the development of both nanobiological interfaces and potential clinical contrast reagents, but these properties are yet to be fully investigated. In this study, we prepared glutathione-protected Au NCs of a similar hydrodynamic size but with three different surface charges: positive, negative, and neutral. Their in vivo biodistribution, excretion, and toxicity were investigated over a 90-day period, and tumor uptake and potential application to radiation therapy were also evaluated. The results showed that the surface charge greatly influenced pharmacokinetics, particularly renal excretion and accumulation in kidney, liver, spleen, and testis. Negatively charged Au NCs displayed lower excretion and increased tumor uptake, indicating a potential for NC-based therapeutics, whereas positively charged clusters caused transient side effects on the peripheral blood system. PMID:27555769

  2. Investigation of Mercury Reduction in Gold Stripping Process at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Pramudya, Irawan

    Mercury is present in many gold ores. By processing these ores, there is a potential of emitting mercury to the environment. Carbon regeneration kiln stacks have been observed as one of the primary source of mercury emission into the atmosphere. Before it is recycled back into the carbon in leach (CIL) or carbon in columns (CIC), carbon used in the gold extraction process needs to be reactivated thermally. Emission of mercury can be minimized by keeping the mercury left in the carbon low before it goes to the carbon regeneration kiln stacks. The objective of this study is establishing the optimum elution conditions of mercury cyanide from loaded carbon (which includes the eluent, concentration, temperature and elution time) with respect to gold stripping. Several methods such as acid washing (UNR-100, HCl or ethanol/UNR-100) were investigated prior to the stripping process. Furthermore, conventional pressurized Zadra and modified Zadra were also studied with regards to mercury concentration in the solution and vapor state as well as maximizing the gold stripping from industrial loaded carbon. 7% UNR-100 acid washing of loaded carbon at 80°C was able to wash out approximately 90% of mercury while maintaining the gold adsorption on the carbon (selective washing). The addition of alcohol in the UNR-100 acid washing solution was able to enhance mercury washing from 90% to 97%. Furthermore, mercury stripping using conventional pressurized (cyanide-alkaline) Zadra was best performed at 80°C (minimal amount of mercury reduced and volatilized) whereas using the same process only 40% of gold was stripped, which makes this process not viable. When alcohol was added to the stripping solution, at 80°C, 95% of gold was detected in the solution while keeping the reduction and volatilization of mercury low. The outcome of this study provides a better understanding of mercury behavior during the acid washing and stripping processes so that the risk of mercury exposure and

  3. Gold Incorporated Mesoporous Silica Thin Film Model Surface as a Robust SERS and Catalytically Active Substrate.

    PubMed

    Sunil Sekhar, Anandakumari Chandrasekharan; Vinod, Chathakudath Prabhakaran

    2016-01-01

    Ultra-small gold nanoparticles incorporated in mesoporous silica thin films with accessible pore channels perpendicular to the substrate are prepared by a modified sol-gel method. The simple and easy spin coating technique is applied here to make homogeneous thin films. The surface characterization using FESEM shows crack-free films with a perpendicular pore arrangement. The applicability of these thin films as catalysts as well as a robust SERS active substrate for model catalysis study is tested. Compared to bare silica film our gold incorporated silica, GSM-23F gave an enhancement factor of 10³ for RhB with a laser source 633 nm. The reduction reaction of p-nitrophenol with sodium borohydride from our thin films shows a decrease in peak intensity corresponding to -NO₂ group as time proceeds, confirming the catalytic activity. Such model surfaces can potentially bridge the material gap between a real catalytic system and surface science studies. PMID:27213321

  4. Electrodeposition of gold nanoparticles on aryl diazonium monolayer functionalized HOPG surfaces.

    PubMed

    González, M C R; Orive, A G; Salvarezza, R C; Creus, A H

    2016-01-21

    Gold nanoparticle electrodeposition on a modified HOPG surface with a monolayer organic film based on aryl diazonium chemistry has been studied. This organic monolayer is electrochemically grown with the use of 2,2-diphenyl-1-picrylhydrazyl (DPPH), a radical scavenger. The electrodeposition of gold on this modified surface is highly favored resulting in an AuNP surface density comparable to that found on glassy carbon. AuNPs grow only in the areas covered by the organic monolayer leaving free clean HOPG zones. A progressive mechanism for the nucleation and growth is followed giving hemispherical AuNPs, homogeneously distributed on the surface and their sizes can be well controlled by the applied electrodeposition potential. By using AFM, C-AFM and electrochemical measurements with the aid of two redox probes, namely Fe(CN)6(4-)/Fe(CN)6(3-) and dopamine, relevant results about the electrochemical modified surface as well as the gold nanoparticles electrodeposited on them are obtained.

  5. Influence of attachment strategy on the thermal stability of hybridized DNA on gold surfaces.

    PubMed

    Petty, Tyler J; Wagner, Caleb E; Opdahl, Aric

    2014-12-23

    The thermal stabilities of double-stranded DNA hybrids immobilized on gold surfaces are shown to be significantly affected by the conformation of the hybrid. To analyze this behavior, DNA probes were immobilized using attachment strategies where the nucleotides within the strand had varying levels of interactions with the gold substrate. The abilities of these probes to form double-stranded hybrids with solution DNA targets were evaluated by surface plasmon resonance (SPR) over a temperature range 25-60 °C. The measurements were used to construct thermal stability profiles for hybrids in each conformation. We observe that DNA hybrids formed with probe strands that interact extensively with the gold surface have stability profiles that are shifted lower by 5-10 °C compared to hybrids formed with end-tethered probes that have fewer interactions with the surface. The results provide an understanding of the experimental conditions in which these weaker DNA hybrids can form and show the additional complexity of evaluating denaturation profiles generated from DNA on surfaces.

  6. Star-like gold nanoparticles as highly active substrate for surface enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Morasso, Carlo; Mehn, Dora; Vanna, Renzo; Bedoni, Marzia; Pascual García, César; Prosperi, Davide; Gramatica, Furio

    2013-02-01

    Surface Enhanced Raman Spectroscopy (SERS) is a popular method in bio-analytical chemistry and a potentially powerful enabling technology for in vitro diagnostics. SERS combines the excellent chemical specificity of Raman spectroscopy with the good sensitivity provided by enhancement of the signal that is observed when a molecule is located on (or very close to) the surface of nanostructured metallic materials. Star-like gold nanoparticles (SGN) are a new class of multibranched nanoparticles that in the last few years have attracted the attention of SERS community for their plasmonic properties. In this work we present a new method to prepare star-like gold nanoparticles with a simple one step protocol at room temperature using hydroquinone as reducing agent. Besides we compare the enhancement of Raman signal of malachite green, a dye commonly employed as label in biological studies, by star-like gold nanoparticles having different size, directly in liquid. This study shows that SGN provide good enhancement of Raman signal and that the effect of their dimension is strongly dependent on the wavelength used. Moreover preliminary results suggest that SGN produced using this method are characterized by good physical-chemical properties and they can be functionalized using the standard thiol chemistry. Overall, these results suggest that star-like gold nanoparticles produced through this method could be used for the further development of highly specific and sensitive SERS-based bio-analytical tests.

  7. Layered Gold and Titanium Dioxide Substrates for Improved Surface Enhanced Raman Spectroscopic Sensing.

    PubMed

    Strobbia, Pietro; Henegar, Alex J; Gougousi, Theodosia; Cullum, Brian M

    2016-08-01

    This manuscript describes a simple process for fabricating gold-based, multi-layered, surface-enhanced Raman scattering (SERS) substrates that can be applied to a variety of different nanostructures, while still providing multi-layer enhancement factors comparable to those previously achieved only with optimized silver/silver oxide/silver substrates. In particular, gold multi-layered substrates generated by atomic layer deposition (ALD) have been fabricated and characterized in terms of their optimal performance, revealing multi-layer enhancements of 2.3-fold per spacer layer applied. These substrates were fabricated using TiO2 as the dielectric spacer material between adjacent gold layers, with ALD providing a conformal thin film with high surface coverage and low thickness. By varying the spacer layer thicknesses from sub-monolayer (non-contiguous) films through multiple TiO2 layer thick films, the non-monotonic spacer layer thickness response has been elucidated, revealing the importance of thin, contiguous dielectric spacer layers for optimal enhancement. Furthermore, the extended shelf life of these gold multi-layered substrates was characterized, demonstrating usable lifetimes (i.e. following storage in ambient conditions) of greater than five months, with the further potential for simple limited electrochemical regeneration even after this time. PMID:27329834

  8. Monolithic nanoporous gold disks with large surface area and high-density plasmonic hot-spots

    NASA Astrophysics Data System (ADS)

    Zhao, Fusheng; Zeng, Jianbo; Arnob, Md Masud Parvez; Santos, Greggy M.; Shih, Wei-Chuan

    2015-03-01

    Plasmonic metal nanostructures have shown great potential in sensing, photovoltaics, imaging and biomedicine, principally due to enhancement of the local electric field by light-excited surface plasmons, the collective oscillation of conduction band electrons. Thin films of nanoporous gold have received a great deal of interest due to the unique 3- dimensional bicontinuous nanostructures with high specific surface area. However, in the form of semi-infinite thin films, nanoporous gold exhibits weak plasmonic extinction and little tunability in the plasmon resonance, because the pore size is much smaller than the wavelength of light. Here we show that by making nanoporous gold in the form of disks of sub-wavelength diameter and sub-100 nm thickness, these limitations can be overcome. Nanoporous gold disks (NPGDs) not only possess large specific surface area but also high-density, internal plasmonic "hot-spots" with impressive electric field enhancement, which greatly promotes plasmon-matter interaction as evidenced by spectral shifts in the surface plasmon resonance. In addition, the plasmonic resonance of NPGD can be easily tuned from 900 to 1850 nm by changing the disk diameter from 300 to 700 nm. The coupling between external and internal nanoarchitecture provides a potential design dimension for plasmonic engineering. The synergy of large specific surface area, high-density hot spots, and tunable plasmonics would profoundly impact applications where plasmonic nanoparticles and non-plasmonic mesoporous nanoparticles are currently employed, e.g., in in-vitro and in-vivo biosensing, molecular imaging, photothermal contrast agents, and molecular cargos.

  9. Hydrogen Spillover between Single Gold Nanorods and Metal Oxide Supports: A Surface Plasmon Spectroscopy Study.

    PubMed

    Collins, Sean S E; Cittadini, Michela; Pecharromán, Carlos; Martucci, Alessandro; Mulvaney, Paul

    2015-08-25

    We used dark field spectroscopy to monitor the dissociation of hydrogen on single gold nanoparticles embedded in metal oxide supports. Individual gold nanorods were monitored in real time to reveal the peak position, the full width at half-maximum, and the relative intensity of the surface plasmon resonances during repeated N2-H2-N2 and air-H2-air cycles. Shifts in the spectra are shown to be due to changes in electron density and not to refractive index shifts in the environment. We demonstrate that hydrogen does not dissociate on gold nanorods (13 nm × 40 nm) at room temperature when in contact with silica and that electrons or hydrogen atoms migrate from Pt nanoparticles to Au nanoparticles through the supporting metal oxide at room temperature. However, this spillover mechanism only occurs for semiconducting oxides (anatase TiO2 and ZnO) and does not occur for Au and Pt nanoparticles embedded in silica. Finally, we show that hydrogen does dissociate directly on anatase surfaces at room temperature during air-H2-air cycles. Our results show that hydrogen spillover, surface dissociation of reactants, and surface migration of chemical intermediates can be detected and monitored in real time at the single particle level.

  10. Surface modification of gold nanoparticles and their monolayer behavior at the air/water interface

    NASA Astrophysics Data System (ADS)

    Hsu, Chaio-Ling; Wang, Ke-Hsuan; Chang, Chien-Hsiang; Hsu, Wen-Ping; Lee, Yuh-Lang

    2011-01-01

    Gold nanoparticles were prepared by two different methods. The first method was chemically grafting the particles with different lengths of alkylthiol (C6SH, C12SH and C18SH). For the second method, the Au particles were surface modified first by mercaptosuccinic acid (MSA) to render a surface with carboxylic acid groups which play a role to physically adsorb cationic surfactant in chloroform. This method was termed physical/chemical method. In the first method, the effects of alkyl chain length and dispersion solvent on the monolayer behavior of surface modified gold nanoparticles was evaluated. The gold nanoparticles prepared by 1-hexanthiol demonstrated the narrowest size distribution. Most of them showed narrower particle size distributions in chloroform than in hexane. For the physical/chemical method, the particles can spread more uniformly on the water surface which is attributed to the amphiphilic character of the particles at the air/water interface. However, the particles cannot pack closely due to the relatively weak particle-particle interaction. The effect of alkyl chain length was also assessed for the second method.

  11. Surface-enhanced plasmon splitting in a liquid-crystal-coated gold nanoparticle.

    PubMed

    Park, Sung Yong; Stroud, D

    2005-06-01

    We show that, when a gold nanoparticle is coated by a thin layer of nematic liquid crystal, the nanoparticle surface has a strong effect on the director orientation, but, surprisingly, this deformation can enhance the surface plasmon splitting. We consider three plausible liquid crystal director configurations in zero electric field: boojum pair (north-south pole configuration), baseball (tetrahedral), and homogeneous. From the discrete dipole approximation, we find that the surface plasmon splitting is largest for the boojum pair, and this result is in good agreement with experiment.

  12. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    PubMed

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor. PMID:26165282

  13. Precise modulation of gold nanorods aspect ratio based on localized surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Wen, Xiaoyan; Shuai, Huang; Min, Li

    2016-10-01

    Gold nanorods (GNRs) aspect ratio is significant to GNRs-based biomedical sensors. In this paper precise modulation of GNRs aspect ratio was realized by H2O2 oxidation based on localized surface plasmon resonance (LSPR) of GNRs. The oxidation process was studied in detail. A linear relationship was revealed between H2O2 oxidation time and the longitudinal LSPR wavelength of GNR, the latter depending on GNRs aspect ratio. Using the relationship GNRs aspect ratios could be modulated by H2O2 oxidation time. Oxidation time deduced aspect ratio was verified by transmission electron microscope (TEM) characterization and the average error is 2.92%. Influences of temperature and pH value on the modulation process were investigated. Increase in temperature (from 30 °C to 60 °C) or solution acidity (pH value from 2.6 to 1.2) facilitated the oxidation process. The proposed method is characterized by its simplicity and efficiency, and would find extensive application prospects in GNRs-based biomedical sensing fields.

  14. Pulse Laser Deposition Fabricating Gold Nanoclusters on a Glassy Carbon Surface for Nonenzymatic Glucose Sensing.

    PubMed

    Shu, Honghui; Chang, Gang; Wang, Zhiqiang; Li, Pai; Zhang, Yuting; He, Yunbin

    2015-01-01

    A One-step technique for depositing gold nanoclusters (GNCs) onto the surface of a glassy carbon (GC) plate was developed by using pulse laser deposition (PLD) with appropriate process parameters. The method is simple and clean without using any templates, surfactants, or stabilizers. The experimental factors (pulse laser number and the pressure of inert gas (Ar)) that affect the morphology and structure of GNCs, and thus affect the electrocatalytic oxidation performance towards glucose were systematically investigated by means of transmission electron microscopy (TEM) and electrochemical methods (cyclic voltammograms (CV) and chronoamperometry methods). The GC electrode modified by GNCs exhibited a rapid response time (about 2 s), a broad linear range (0.1 to 20 mM), and good stability. The sensitivity was estimated to be 31.18 μA cm(-2) mM(-1) (vs. geometric area), which is higher than that of the Au bulk electrode. It has a good resistance to the common interfering species, such as ascorbic acid (AA), uric acid (UA) and 4-acetaminophen (AP). Therefore, this work has demonstrated a simple and effective sensing platform for the nonenzymatic detection of glucose, and can be used as a new material for a novel non-enzymatic glucose sensor.

  15. Biotin avidin amplified magnetic immunoassay for hepatitis B surface antigen detection using GoldMag nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, An; Geng, Tingting; Fu, Qiang; Chen, Chao; Cui, Yali

    2007-04-01

    Using GoldMag (Fe3O4/Au) nanoparticles as a carrier, a biotin-avidin amplified ELISA was developed to detect hepatitis B surface antigen (HBsAg). A specific antibody was labeled with biotin and then used to detect the antigen with an antibody coated on GoldMag nanoparticles by a sandwich ELISA assay. The results showed that 5 mol of biotin were surface bound per mole of antibody. The biotin-avidin amplified ELISA assay has a higher sensitivity than that of the direct ELISA assay. There is 5-fold difference between HBsAg positive and negative serum even at dilution of 1:10000, and the relative standard deviation of the parallel positive serum at dilution of 1:4000 is 5.98% (n=11).

  16. Surface enhanced Raman scattering detection of single R6G molecules on nanoporous gold films

    NASA Astrophysics Data System (ADS)

    Liu, Hongwen; Zhang, L.; Yamaguchi, Y.; Iwasaki, H.; Inouye, Y.; Xue, Q. K.; Chen, M. W.

    2011-03-01

    Detecting single molecules with high sensitivity and molecular specificity is of great practical interest in many fields such as chemistry, biology, medicine, and pharmacology. For this purpose, cheap and highly active substrates are of crucial importance. Recently, nanoporous metals (NPMs), with a three-dimensional continuous network structure and pore channels usually much smaller than the wavelength of visible light, revealed outstanding optical properties in surface enhanced Raman scattering (SERS). In this work, we further modify the nanoporous gold films by growing a high density of gold nano-tips on the surface. Extremely focused electromagnetic fields can be produced at the apex of the nano-tips, resulting in so-called hot spots. With this NPM-based and affordable substrate, single molecule-detection is achievable with ultrahigh enhancement in SERS.

  17. Surface plasmon polaritons in a composite system of porous silicon and gold

    SciTech Connect

    Vainshtein, J. S.; Goryachev, D. N.; Ken, O. S. Sreseli, O. M.

    2015-04-15

    A composite system of silicon quantum dots and gold particles with properties periodically changing along the surface (i.e., a system exhibiting the properties of a diffraction grating) is obtained by a one-step metal-assisted chemical etching. The spectral and angular dependences of the photoresponse for the composite system on single-crystal silicon are studied. The photoresponse peaks were observed, which behavior (the dependence on the parameters of the diffraction grating, wavelength and incidence angles of light) is attributed to the excitation of plasmon-polariton modes at the surface of the composite system with the diffraction grating. At the same time, the obtained values of the wave vectors for these modes are smaller than those calculated for plasmon polaritons excited at the interface between air and metal (gold) diffraction grating.

  18. Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide.

    PubMed

    Wu, Qiong; Sun, Ying; Ma, Pinyi; Zhang, Di; Li, Shuo; Wang, Xinghua; Song, Daqian

    2016-03-24

    A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL(-1), which is 32 times lower than that of graphene oxide-based biosensor. PMID:26944998

  19. Gold nanostar-enhanced surface plasmon resonance biosensor based on carboxyl-functionalized graphene oxide.

    PubMed

    Wu, Qiong; Sun, Ying; Ma, Pinyi; Zhang, Di; Li, Shuo; Wang, Xinghua; Song, Daqian

    2016-03-24

    A new high-sensitivity surface plasmon resonance (SPR) biosensor based on biofunctional gold nanostars (AuNSs) and carboxyl-functionalized graphene oxide (cGO) sheets was described. Compared with spherical gold nanoparticles (AuNPs), the anisotropic structure of AuNSs, which concentrates the electric charge density on its sharp tips, could enhance the local electromagnetic field and the electronic coupling effect significantly. cGO was obtained by a diazonium reaction of graphene oxide (GO) with 4-aminobenzoic acid. Compared with GO, cGO could immobilize more antibodies due to the abundant carboxylic groups on its surface. Testing results show that there are fairly large improvements in the analytical performance of the SPR biosensor using cGO/AuNSs-antigen conjugate, and the detection limit of the proposed biosensor is 0.0375 μg mL(-1), which is 32 times lower than that of graphene oxide-based biosensor.

  20. Controlling formation of gold nanoparticles generated in situ at a polymeric surface

    NASA Astrophysics Data System (ADS)

    Clukay, Christopher J.; Grabill, Christopher N.; Hettinger, Michelle A.; Dutta, Aniruddha; Freppon, Daniel J.; Robledo, Anthony; Heinrich, Helge; Bhattacharya, Aniket; Kuebler, Stephen M.

    2014-02-01

    This work shows that in situ reduction of metal ions bound at a polymer surface can form nanoparticles within the polymer matrix as well as at the interface, and the size and distribution of nanoparticles between the interface and subsurface depends upon the choice of reagents and reaction conditions. Tetrachloroaurate ions were bound to cross-linked SU-8 films that were functionalized using a variety of multi-functional amines, then reduced using one of several reagents. Reduction using sodium borohydride or sodium citrate generates bands of interspersed gold nanoparticles as much as 40 nm deep within the polymer, indicating that both the Au ions and the reducing agent can penetrate the surface enabling formation of nanoparticles within the polymer matrix. Nanoparticle formation can be confined nearer to the polymer interface by reducing with hydroquinone, or by processing the polymer film in aqueous media using high molecular-weight multifunctional amines that confine the gold ions at the interface.

  1. Gold replica of olive branch left on moons surface by Apollo 11

    NASA Technical Reports Server (NTRS)

    1969-01-01

    A gold replica of an olive branch, the traditional symbol of peace, which was left on the Moon's surface by the Apollo 11 crew members. Astronaut Neil A. Armstrong, commander, was in charge of placing the replica (less than half a foot in length) on the Moon. The gesture represents a fresh wish for peace for all mankind. astronauts will be released from quarantine on August 11, 1969. Donald K. Slayton (right), MSC Director of Flight Crew Operations; and Lloyd Reeder, training coordinator.

  2. Demonstrating the angular, wavelength and polarization dependence of surface plasmon resonance on thin gold films—An undergraduate experiment

    NASA Astrophysics Data System (ADS)

    Connolly, Peter W. R.; Kaplan, Andrey

    2016-10-01

    This paper describes the design of a simple and compact optical system capable of examining fundamental properties of light coupling to surface plasmon resonance (SPR) on a thin gold film. The setup, involving a rotatable Attenuated Total Reflection device, from which the reflected light is focused by means of a parabolic mirror, allows for the investigation of the dependence of the reflected intensity on the angle of incidence without moving the detector. It additionally makes provision for a convenient exchange of light sources or the possibility to incorporate a broadband source suitable to investigate SPR at different wavelengths. Theoretical simulation of the experimental data is provided, as well as straightforward calculations for exploring the physics of light excited waves propagating on a surface.

  3. Recyclable surface-enhanced Raman scattering template based on nanoporous gold film/Si nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Chang Xing; Liu, Luo; Jun Yin, Hong; Fang, Hui; Mei Zhao, Yong; Jian Bi, Chu; Jun Xu, Hai

    2014-07-01

    Nanoporous gold film (NPGF) composed of gold nanoparticles was used to cover a large Si nanowire array (SiNWA) by simple metal-assisted chemical etching and metal reduction processes. Three-dimensional SiNWA/NPGF was employed as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for crystal violet was as low as 10-12M, and the Raman enhancement factor was as large as 107 with a relative standard deviation of less than 20%. After calibrating the Raman peak intensities of crystal violet and thiram could be quantitatively detected. More importantly, the SERS substrates are recyclable and can be used for many gold surface adsorbates such as p-aminothiophenol, crystal violet, Rhodamine 6G, and methyl orange, which can all be rapidly and completely removed from the NPGF surface. Our findings are an important advance in SERS substrates and will allow the quantitative and recyclable detection of trace organic contaminants.

  4. Surface-enhanced Raman scattering of crystal violets from periodic array of gold nanocylinders

    NASA Astrophysics Data System (ADS)

    Bi, Gang; Wang, Li; Cai, Chunfeng; Ueno, Kosei; Misawa, Hiroaki; Qiu, Jianrong

    2014-09-01

    The periodic arrays of gold nanocylinder with 121 nm in diameter, 6.3 nm in gap, and 34 nm in thickness are fabricated on glass by electron-beam lithography and lift-off techniques. Some crystal violet molecules are coated on the array by using the dipping and drawing method. In addition, the surface-enhanced Raman scattering (SERS) spectra of these samples with and without gold nanocylinder arrays are characterized specifically. The largest enhancement factor is obtained when the excitation wavelength corresponds to the peak wavelength of localized surface plasmon resonance (LSPR). The density functional theory and the finite-difference time-domain method are used for the calculations of the extinction spectrum of the arrays and Raman spectra of the crystal violet, respectively. These results unambiguously demonstrate that the periodic arrays of gold nanocylinder have good and effective surface-enhanced properties for Raman scattering of crystal violets, and they also show that the excitation wavelength corresponding to the peak one of the LSPR is one of the major reasons causing SERS.

  5. Influence of ceramic surface texture on the wear of gold alloy and heat-pressed ceramics.

    PubMed

    Saiki, Osamu; Koizumi, Hiroyasu; Nogawa, Hiroshi; Hiraba, Haruto; Akazawa, Nobutaka; Matsumura, Hideo

    2014-01-01

    The purpose of this study was to evaluate the influence of ceramic surface texture on the wear of rounded rod specimens. Plate specimens were fabricated from zirconia (ZrO2), feldspathic porcelain, and lithium disilicate glass ceramics (LDG ceramics). Plate surfaces were either ground or polished. Rounded rod specimens with a 2.0-mm-diameter were fabricated from type 4 gold alloy and heat-pressed ceramics (HP ceramics). Wear testing was performed by means of a wear testing apparatus under 5,000 reciprocal strokes of the rod specimen with 5.9 N vertical loading. The results were statistically analyzed with a non-parametric procedure. The gold alloy showed the maximal height loss (90.0 µm) when the rod specimen was abraded with ground porcelain, whereas the HP ceramics exhibited maximal height loss (49.8 µm) when the rod specimen was abraded with ground zirconia. There was a strong correlation between height loss of the rod and surface roughness of the underlying plates, for both the gold alloy and HP ceramics.

  6. Synthesis of gold nanorods with a longitudinal surface plasmon resonance peak of around 1250 nm

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Nhat Hang; Le Trinh Nguyen, Thi; Thanh Tuyen Luong, Thi; Thang Nguyen, Canh Minh; Nguyen, Thi Phuong Phong

    2016-03-01

    We prepared gold nanorods and joined them to chemicals such as tetrachloauric (III) acid trihydrate, silver nitrate, hydroquinone, hexadecyltrimethylammonium bromide, sodium hydroxide and sodium borohydride using the seed-mediated method. The combination of hydroquinone, with or without salicylic acid, influences the size of the gold nanorods, and this is demonstrated by the results of TEM images, UV-vis spectra and the value of the longitudinal surface plasmon resonance peak with respect to the UV-vis spectra. By changing the Ag+ ion and hydroquinone concentration and the combination of hydroquinone and salicylic acid, the size of the gold nanorods can be controlled and this is manifested by longitudinal surface plasmon resonance peaks forming between 875 and 1278 nm. In particular, sample E2 achieved a longitudinal surface plasmon peak at 1273 nm and an aspect ratio of more than 10 by modifying the hydroquinone to 2.5 mM and salicylic acid to 0.5 mM concentration in the growth solution.

  7. Investigation of gold nanoparticle radiosensitization mechanisms using a free radical scavenger and protons of different energies.

    PubMed

    Jeynes, J C G; Merchant, M J; Spindler, A; Wera, A-C; Kirkby, K J

    2014-11-01

    Gold nanoparticles (GNPs) have been shown to sensitize cancer cells to x-ray radiation, particularly at kV energies where photoelectric interactions dominate and the high atomic number of gold makes a large difference to x-ray absorption. Protons have a high cross-section for gold at a large range of relevant clinical energies, and so potentially could be used with GNPs for increased therapeutic effect.Here, we investigate the contribution of secondary electron emission to cancer cell radiosensitization and investigate how this parameter is affected by proton energy and a free radical scavenger. We simulate the emission from a realistic cell phantom containing GNPs after traversal by protons and x-rays with different energies. We find that with a range of proton energies (1-250 MeV) there is a small increase in secondaries compared to a much larger increase with x-rays. Secondary electrons are known to produce toxic free radicals. Using a cancer cell line in vitro we find that a free radical scavenger has no protective effect on cells containing GNPs irradiated with 3 MeV protons, while it does protect against cells irradiated with x-rays. We conclude that GNP generated free radicals are a major cause of radiosensitization and that there is likely to be much less dose enhancement effect with clinical proton beams compared to x-rays.

  8. Investigation of gold nanoparticle radiosensitization mechanisms using a free radical scavenger and protons of different energies

    NASA Astrophysics Data System (ADS)

    Jeynes, J. C. G.; Merchant, M. J.; Spindler, A.; Wera, A.-C.; Kirkby, K. J.

    2014-10-01

    Gold nanoparticles (GNPs) have been shown to sensitize cancer cells to x-ray radiation, particularly at kV energies where photoelectric interactions dominate and the high atomic number of gold makes a large difference to x-ray absorption. Protons have a high cross-section for gold at a large range of relevant clinical energies, and so potentially could be used with GNPs for increased therapeutic effect. Here, we investigate the contribution of secondary electron emission to cancer cell radiosensitization and investigate how this parameter is affected by proton energy and a free radical scavenger. We simulate the emission from a realistic cell phantom containing GNPs after traversal by protons and x-rays with different energies. We find that with a range of proton energies (1-250 MeV) there is a small increase in secondaries compared to a much larger increase with x-rays. Secondary electrons are known to produce toxic free radicals. Using a cancer cell line in vitro we find that a free radical scavenger has no protective effect on cells containing GNPs irradiated with 3 MeV protons, while it does protect against cells irradiated with x-rays. We conclude that GNP generated free radicals are a major cause of radiosensitization and that there is likely to be much less dose enhancement effect with clinical proton beams compared to x-rays.

  9. Morphology, stresses, and surface reactivity of nanoporous gold synthesized from nanostructured precursor alloys

    NASA Astrophysics Data System (ADS)

    Rouya, Eric

    Nanoporous metallic materials (NMMs) are generally synthesized using dealloying, whereby the more reactive component is dissolved from a homogeneous alloy in a suitable electrolyte, and the more noble metal atoms simultaneously diffuse into 3-D clusters, forming a bi-continuous network of interconnected ligaments. Nanoporous gold (NPG) in particular is a well-known NMM; it is inert, bio-compatible, and capable of developing large surface areas with 1--100nm pores. While several studies have demonstrated its potential usefulness in fuel cell and sensing devices, its structural, mechanical, and electrocatalytic properties still require further investigation, particularly if NPG is synthesized from precursor alloy films exhibiting metastable nanostructures. In this dissertation, the electrodeposition (ECD) process, microstrucural characteristics, and metatstability of Au-Ni precursor alloys are investigated. The stresses evolved during Au-Ni alloy nucleation and growth are investigated in situ and correlated with microstructural and electrochemical data in order to identify the various stress-inducing mechanisms. In situ stresses generated during Au-Ni and Au-Ag dealloying were investigated, and additionally correlated with the growth stresses. Finally, the surface area and electrocatalytic properties of NPG are characterized using a variety of electrochemical techniques. Potentiostatically electrodeposited Au1-x-Nix (x: 0--90at%) films form a continuous series of metastable solid solutions and exhibit a nanocrystalline morphology, with ˜10--20 nm grains, the size of which decreases with increasing Ni content. The formation of a metastable structure was interpreted in terms of the limited surface diffusivities of adatoms at the growing interface and atomic volume differences (˜15%). Internal stresses generated during ECD of Ni-rich films can be explained assuming a 3-D Volmer-Weber growth mode, where the stress is initially compressive, then transitions into tension

  10. Improved Efficiency of Silicon Nanoholes/Gold Nanoparticles/Organic Hybrid Solar Cells via Localized Surface Plasmon Resonance

    NASA Astrophysics Data System (ADS)

    Lu, Ronghua; Xu, Ling; Ge, Zhaoyun; Li, Rui; Xu, Jun; Yu, Linwei; Chen, Kunji

    2016-03-01

    Silicon is the most widely used material for solar cells due to its abundance, non-toxicity, reliability, and mature fabrication process. In this paper, we fabricated silicon nanoholes (SiNHS)/gold nanoparticles (AuNPS)/organic hybrid solar cells and investigated their spectral and opto-electron conversion properties. SiNHS nanocomposite films were fabricated by metal-assisted electroless etching (EE) method. Then, we modified the surface of the nanocomposite films by exposing the samples in the air. After that, polymer poly(3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) blended with AuNPS were spin-coated on the surface of the SiNHS nanocomposite films as a hole-transporting layer. The external quantum efficiency (EQE) values of the solar cells with AuNPS are higher than that of the samples without AuNPS in the spectral region of 600-1000 nm, which were essential to achieve high performance photovoltaic cells. The power conversion efficiency (PCE) of the solar cells incorporating AuNPS exhibited an enhancement of 27 %, compared with that of the solar cells without AuNPS. We thought that the improved efficiency were attributed to localized surface plasmon resonance (LSPR) triggered by gold nanoparticles in SiNHS nanocomposite films.

  11. Composite fluorocarbon membranes by surface-initiated polymerization from nanoporous gold-coated alumina.

    PubMed

    Escobar, Carlos A; Zulkifli, Ahmad R; Faulkner, Christopher J; Trzeciak, Alex; Jennings, G Kane

    2012-02-01

    This manuscript describes the versatile fabrication and characterization of a novel composite membrane that consists of a porous alumina support, a 100 nm thick nanoporous gold coating, and a selective poly(5-(perfluorohexyl)norbornene) (pNBF6) polymer that can be grown exclusively from the nanoporous gold or throughout the membrane. Integration of the three materials is achieved by means of silane and thiol chemistry, and the use of surface-initiated ring-opening metathesis polymerization (SI-ROMP) to grow the pNBF6. The use of SI-ROMP allows tailoring of the extent of polymerization of pNBF6 throughout the structure by varying polymerization time. Scanning electron microscopy (SEM) images indicate that the thin polymer films cover the structure entirely. Cross-sectional SEM images of the membrane not only corroborate growth of the pNBF6 polymer within both the porous alumina and the nanoporous gold coating but also show the growth of a pNBF6 layer between these porous substrates that lifts the nanoporous gold coating away from the alumina. Advancing contact angle (θ(A)) measurements show that the surfaces of these composite membranes exhibit both hydrophobic (θ(A) = 121-129)° and oleophobic (θ(A) = 69-74)° behavior due to the fluorocarbon side chains of the pNBF6 polymer that dominate the surface. Results from electrochemical impedance spectroscopy (EIS) confirm that the membranes provide effective barriers to aqueous ions, as evidenced by a resistive impedance on the order of 1 × 10(7) Ω cm(2). Sulfonation of the polymer backbone substantially enhances ion transport through the composite membrane, as indicated by a 40-60 fold reduction in resistive impedance. Ion transport and selectivity of the membrane change by regulating the polymerization time. The fluorinated nature of the sulfonated polymer renders the membrane selective toward molecules with similar chemical characteristics. PMID:22195729

  12. Composite fluorocarbon membranes by surface-initiated polymerization from nanoporous gold-coated alumina.

    PubMed

    Escobar, Carlos A; Zulkifli, Ahmad R; Faulkner, Christopher J; Trzeciak, Alex; Jennings, G Kane

    2012-02-01

    This manuscript describes the versatile fabrication and characterization of a novel composite membrane that consists of a porous alumina support, a 100 nm thick nanoporous gold coating, and a selective poly(5-(perfluorohexyl)norbornene) (pNBF6) polymer that can be grown exclusively from the nanoporous gold or throughout the membrane. Integration of the three materials is achieved by means of silane and thiol chemistry, and the use of surface-initiated ring-opening metathesis polymerization (SI-ROMP) to grow the pNBF6. The use of SI-ROMP allows tailoring of the extent of polymerization of pNBF6 throughout the structure by varying polymerization time. Scanning electron microscopy (SEM) images indicate that the thin polymer films cover the structure entirely. Cross-sectional SEM images of the membrane not only corroborate growth of the pNBF6 polymer within both the porous alumina and the nanoporous gold coating but also show the growth of a pNBF6 layer between these porous substrates that lifts the nanoporous gold coating away from the alumina. Advancing contact angle (θ(A)) measurements show that the surfaces of these composite membranes exhibit both hydrophobic (θ(A) = 121-129)° and oleophobic (θ(A) = 69-74)° behavior due to the fluorocarbon side chains of the pNBF6 polymer that dominate the surface. Results from electrochemical impedance spectroscopy (EIS) confirm that the membranes provide effective barriers to aqueous ions, as evidenced by a resistive impedance on the order of 1 × 10(7) Ω cm(2). Sulfonation of the polymer backbone substantially enhances ion transport through the composite membrane, as indicated by a 40-60 fold reduction in resistive impedance. Ion transport and selectivity of the membrane change by regulating the polymerization time. The fluorinated nature of the sulfonated polymer renders the membrane selective toward molecules with similar chemical characteristics.

  13. 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

  14. Fabrication Localized Surface Plasmon Resonance sensor chip of gold nanoparticles and detection lipase-osmolytes interaction

    NASA Astrophysics Data System (ADS)

    Ghodselahi, T.; Hoornam, S.; Vesaghi, M. A.; Ranjbar, B.; Azizi, A.; Mobasheri, H.

    2014-09-01

    Co-deposition of RF-sputtering and RF-PECVD from acetylene gas and Au target were used to prepare sensor chip of gold nanoparticles (Au NPs). Deposition conditions were optimized to reach a Localized Surface Plasmon Resonance (LSPR) sensor chip of Au NPs with particle size less than 10 nm. The RF power was set at 180 W and the initial gas pressure was set at 0.035 mbar. Transmission Electron Microscopy (TEM) images and Atomic Force Microscopy (AFM) data were used to investigate particles size and surface morphology of LSPR sensor chip. The Au and C content of the LSPR sensor chip of Au NPs was obtained from X-ray photoelectron spectroscopy (XPS). The hydrogenated amorphous carbon (a-C:H) thin film was used as intermediate material to immobilize Au NPs on the SiO2 substrate. The interaction between two types of osmolytes, i.e. sorbitol and trehalose, with Pseudomonas cepacia lipase (PCL) were detected by the prepared LSPR biosensor chip. The detection mechanism is based on LSPR spectroscopy in which the wavelength of absorption peak is sensitive to the refractive index of the environment of the Au NPs. This mechanism eliminates the use of a probe or immobilization of PCL on the Au NPs of LSPR sensor chip. The interaction between PCL and osmolytes can change refractive index of the mixture or solution. We found that unlike to trehalose, sorbitol interacts with the PCL. This interaction increases refractive index of the PCL and sorbitol mixture. Refractive index of PCL in the presence of different concentration of sorbitol was obtained by Mie theory modeling of LSPR peaks. This modeling stated that the present LSPR sensor chip has sensitivity as high as wavelength shift of 175 nm per refractive index. Moreover, the detection of such weakly interaction between bio-molecules cannot be achieved by other analysis.

  15. The surface structure of silver-coated gold nanocrystals and its influence on shape control

    SciTech Connect

    Padmos, J. Daniel; Personick, Michelle L.; Tang, Qing; Duchesne, Paul N.; Jiang, De-en; Mirkin, Chad A.; Zhang, Peng

    2015-07-08

    Understanding the surface structure of metal nanocrystals with specific facet indices is important due to its impact on controlling nanocrystal shape and functionality. However, this is particularly challenging for halide-adsorbed nanocrystals due to the difficulty in analysing interactions between metals and light halides (for example, chloride). Here we uncover the surface structures of chloride-adsorbed, silver-coated gold nanocrystals with {111}, {110}, {310} and {720} indexed facets by X-ray absorption spectroscopy and density functional theory modelling. The silver–chloride, silver–silver and silver–gold bonding structures are markedly different between the nanocrystal surfaces, and are sensitive to their formation mechanism and facet type. A unique approach of combining the density functional theory and experimental/simulated X-ray spectroscopy further verifies the surface structure models and identifies the previously indistinguishable valence state of silver atoms on the nanocrystal surfaces. Overall, this work elucidates the thus-far unknown chloride–metal nanocrystal surface structures and sheds light onto the halide-induced growth mechanism of anisotropic nanocrystals.

  16. Surface modification of a gold-coated microcantilever and application in biomarker detection

    NASA Astrophysics Data System (ADS)

    Binh Pham, Van; Nhat Khoa Phan, Thanh; Nguyen, Thanh Trung; Pham, Xuan Thanh Tung; Thanh Tuyen Le, Thi; Chien Dang, Mau

    2015-12-01

    Biosensors have been rapidly developed recently. Biological receptors, such as antibodies, must be immobilized on these sensors’ surfaces to make the sensor capable of capturing a target analyte. In this research we studied how to modify a gold-coated surface of a microcantilever, a sensor with high potential in biological and medical applications. Thiol chemistry was adapted to create a cysteamine layer on a gold surface, and subsequently glutaraldehyde was used as a cross-linking agent to react with amine groups in receptors. In order to evaluate the efficiency of immobilizing protein on an Au surface and also whether the protein retains its biological activity, horseradish peroxidase enzyme (HRP) with its activity to catalyze a reaction between 2,2‧-azino-bis [3-ethylbenzothiazoline-6-sulphonic acid] (ABTS) and {{{H}}}2{{{{O}}}2}- was used as a testing protein. The result showed that HRP was immobilized successfully on cysteamine and glutaraldehyde layers and retained its activity. The cantilever’s tip deflection was also measured, and results showed that each layer created surface stress and made the cantilever bend—in particular, the cysteamine layer induced bending as high as 6 μm. An antibody of alpha-fetoprotein (AFP) was immobilized on the cantilever surface, and the measurement deflection showed that the sensor responded to solution containing AFP with concentration from 100 to 500 ng ml-1.

  17. Guided Cell Patterning On Gold-Silicon Dioxide Substrates by Surface Molecular Engineering

    SciTech Connect

    Veiseh, Mandana; Wickes, Bronwyn; Castner, David G.; Zhang, Miqin

    2004-07-01

    We report an effective approach to patterning cells on a gold-silicon substrate with high precision, selectivity, stability, and reproducibility. This technique is based on photolithography and surface molecular engineering and does not involve a cell positioning or delivery device, thus reducing potential damage to cells. Cell patterning is achieved by activating the gold regions with functionalized thiols that covalently bind proteins to guide the subsequent cell adhesion and passivating the silicon regions with polyethylene glycol (PEG) to resist cell adhesion. Time-of-light secondary ion mass spectrometry (TOF-SIMS), a powerful surface chemical state imaging technique that allows simultaneous chemical and spatial characterization, was used to characterize the chemistry of the cell-adhesive and cell-resistant regions of the surface at key stages in the device fabrication. Fourier transform infrared (FTIR) reflectance spectroscopy was used to verify the immobilization of proteins on model surfaces. Proteins were tagged with Rhodamine fluorescent probes to characterize patterned surfaces by fluorescence microscopy. Finally, the ability of the engineered surfaces to guide cell adhesion was illustrated by differential interference contrast (DIC) reflectance microscopy. The cell patterning technique introduced in this study is compatible with micro- and photo- electronics, and may have numerous medical, environmental, and defense applications.

  18. The surface structure of silver-coated gold nanocrystals and its influence on shape control

    DOE PAGESBeta

    Padmos, J. Daniel; Personick, Michelle L.; Tang, Qing; Duchesne, Paul N.; Jiang, De-en; Mirkin, Chad A.; Zhang, Peng

    2015-07-08

    Understanding the surface structure of metal nanocrystals with specific facet indices is important due to its impact on controlling nanocrystal shape and functionality. However, this is particularly challenging for halide-adsorbed nanocrystals due to the difficulty in analysing interactions between metals and light halides (for example, chloride). Here we uncover the surface structures of chloride-adsorbed, silver-coated gold nanocrystals with {111}, {110}, {310} and {720} indexed facets by X-ray absorption spectroscopy and density functional theory modelling. The silver–chloride, silver–silver and silver–gold bonding structures are markedly different between the nanocrystal surfaces, and are sensitive to their formation mechanism and facet type. A uniquemore » approach of combining the density functional theory and experimental/simulated X-ray spectroscopy further verifies the surface structure models and identifies the previously indistinguishable valence state of silver atoms on the nanocrystal surfaces. Overall, this work elucidates the thus-far unknown chloride–metal nanocrystal surface structures and sheds light onto the halide-induced growth mechanism of anisotropic nanocrystals.« less

  19. Silver- and Gold-Ordered Structures on Single-Crystal Silicon Surface After Thermal Deposition.

    PubMed

    Karbivskyy, Vladimir; Karbivska, Love; Artemyuk, Viktor

    2016-12-01

    The formation mechanisms of Ag- and Au-ordered structures on single-crystal silicon (Si) (111) and Si (110) surfaces were researched using high-resolution scanning tunneling microscopy method. It was shown that different patterns of self-assembled nanostructures with very precise and regular geometric shapes can be produced by controlling process parameters of thermal metal spraying on the substrate. The surfaces of nanorelieves at each stage of deposition were researched, and the main stages of morphological transformation were fixed.Self-ordered hexagonal pyramid-shaped nanostructures were formed at thermal deposition of gold on the Si (111), whereas only monolayer hexagonal formation could be observed on the plane Si (110). Gold monolayer flake nanostructures were obtained under certain technological parameters.Atomically smooth Ag film cannot be obtained on the Si (111) surface by means of thermal spraying at room temperature. The formation of two-dimensional (2D) clusters takes place; heating of these clusters at several hundred degrees Celsius leads to their transformation into atomically smooth covering.The weak interaction between Ag multilayer coatings and substrate was established that allows to clear crystal surface from metal with reproduction of the reconstructed Si (111) 7 × 7 surface by slight warming. The offered method can be used for single-crystal surface protection from destruction.

  20. Surface characterization and efficiency of a matrix-free and flat carboxylated gold sensor chip for surface plasmon resonance (SPR).

    PubMed

    Roussille, L; Brotons, G; Ballut, L; Louarn, G; Ausserré, D; Ricard-Blum, S

    2011-09-01

    We report the preparation and characterization of a matrix-free carboxylated surface plasmon resonance (SPR) sensor chip with high sensing efficiency by functionalizing a bare gold thin film with a self-assembled monolayer of 16-mercaptohexadecanoic acid (SAM-MHDA chip). The self assembled monolayer surface coverage of the gold layer was carefully evaluated and the SAM was characterized by infrared reflection absorption spectroscopy, X-ray photoemission spectroscopy, atomic force microscopy, X-ray reflectivity-diffraction, and SPR experiments with bovine serum albumin. We compared the SPR signal obtained on this chip made of a dense monolayer of carboxylic acid groups with commercially available carboxylated sensor chips built on the same gold substrate, a matrix-free C1 chip, and a CM5 chip with a ~100 nm dextran hydrogel matrix (GE Healthcare). Two well-studied interaction types were tested, the binding of a biotinylated antibody (immunoglobulin G) to streptavidin and an antigen-antibody interaction. For both interactions, the well characterized densely functionalized SAM-MHDA chip gave a high signal-to-noise ratio and showed a gain in the availability of immobilized ligands for their partners injected in buffer flow. It thus compared favourably with commercially available sensor chips. PMID:21755270

  1. Photocatalytic Destruction of Tetracycline Hydrochloride on the Surface of Titanium Dioxide Films Modified by Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Linnik, O. P.; Zhukovskiy, M. A.; Starukh, G. N.; Smirnova, N. P.; Gaponenko, N. V.; Asharif, A. M.; Khoroshko, L. S.; Borisenko, V. E.

    2015-01-01

    Films of titania (TiO2) and titania modified with gold nanoparticles (TiO2:Au) were synthesized by a sol-gel method on substrates of glass, aluminum, and aluminum with a layer of nanotextured aluminum or porous anodic alumina. The photocatalytic activity of the samples was investigated in an aqueous solution of the antibiotic tetracycline hydrochloride (TC). TC decomposition was observed in the presence of all samples as a reduction of the solution optical density in the range below 500 nm. Titania was in the crystalline anatase phase with incorporated spherical gold nanoparticles primarily of sizes 1-10 nm after heat treatment at 400°C. Modification of TiO2 films with gold nanoparticles on glass or aluminum substrates did not increase the photocatalytic activity of the samples. It was found that complexes of TC with Al3+ in solution formed only in the presence of gold nanoparticles in the film either in the dark or with UV irradiation.

  2. Layer-dependent surface potential of phosphorene and anisotropic/layer-dependent charge transfer in phosphorene-gold hybrid systems.

    PubMed

    Xu, Renjing; Yang, Jiong; Zhu, Yi; Yan, Han; Pei, Jiajie; Myint, Ye Win; Zhang, Shuang; Lu, Yuerui

    2016-01-01

    The surface potential and the efficiency of interfacial charge transfer are extremely important for designing future semiconductor devices based on the emerging two-dimensional (2D) phosphorene. Here, we directly measured the strong layer-dependent surface potential of mono- and few-layered phosphorene on gold, which is consistent with the reported theoretical prediction. At the same time, we used an optical way photoluminescence (PL) spectroscopy to probe charge transfer in the phosphorene-gold hybrid system. We firstly observed highly anisotropic and layer-dependent PL quenching in the phosphorene-gold hybrid system, which is attributed to the highly anisotropic/layer-dependent interfacial charge transfer.

  3. Glutathione-coated luminescent gold nanoparticles: a surface ligand for minimizing serum protein adsorption.

    PubMed

    Vinluan, Rodrigo D; Liu, Jinbin; Zhou, Chen; Yu, Mengxiao; Yang, Shengyang; Kumar, Amit; Sun, Shasha; Dean, Andrew; Sun, Xiankai; Zheng, Jie

    2014-08-13

    Ultrasmall glutathione-coated luminescent gold nanoparticles (GS-AuNPs) are known for their high resistance to serum protein adsorption. Our studies show that these NPs can serve as surface ligands to significantly enhance the physiological stability and lower the serum protein adsorption of superparamagnetic iron oxide nanoparticles (SPIONs), in addition to rendering the NPs the luminescence property. After the incorporation of GS-AuNPs onto the surface of SPIONs to form the hybrid nanoparticles (HBNPs), these SPIONs' protein adsorption was about 10-fold lower than those of the pure glutathione-coated SPIONs suggesting that GS-AuNPs are capable of providing a stealth effect against serum proteins.

  4. Fluctuations of surface-enhanced Raman spectra of CO adsorbed on gold substrates

    NASA Astrophysics Data System (ADS)

    Kudelski, Andrzej; Pettinger, Bruno

    2004-01-01

    Surface-enhanced Raman scattering (SERS) of CO adsorbed on roughened gold surfaces has been studied using a Raman microscope with high spatial resolution. Sequentially recorded SERS spectra showed variations of Raman lines in their number, intensity, frequency, and halfwidth. Sometimes, in addition to the band for CO adsorbed at top sites, Raman peaks for bridge-bonded CO appear, showing large intensity fluctuations. Obviously, SERS fluctuations represent a more general property of SERS and point to local restructuring of substrates that changes temporarily the character of adsorption sites and/or their contribution to SERS. The single molecule 'blinking' effect is also discussed.

  5. Size and Surface Effect of Gold Nanoparticles (AuNPs) in Nanogold-Assisted Pcr

    NASA Astrophysics Data System (ADS)

    Huang, Jiehuan; Zhang, Xiaodong; Wang, Chunmei; Wang, Lihua; Li, Haikuo; Cao, Xueyan; Zhang, Aili; Li, Xueling; Fan, Chunhai; Hu, Jun

    Recently, gold nanoparticles (AuNPs) were reported to increase the specificity and efficiency of the polymerase chain reaction (PCR). In this paper, we tested the enhancement of AuNPs with five different sizes on the specificity of two-round PCR. The results showed that, except 5.02 nm AuNPs, the AuNPs that could achieve the similar enhancement happened to have nearly the same total surface area. The surface effect seems to be the key factor of nanogold-assisted PCR.

  6. Gold nanoparticle absorption under a nanoscale tip illuminated by surface-plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Huda, Gazi M.; Hastings, J. Todd

    2013-03-01

    This research numerically calculated the optical absorption of gold nanoparticles (AuNP) in the presence of metallic (Au) and dielectric (Si) AFM probes, illuminated by a surface plasmon polaritons on an infinite gold substrate. Nanoscale probes localize and enhance the field between the apex of the tip and the particle. However, the absorption of the nanoparticle is not always enhanced; in fact, under a gold tip, the absorption is suppressed for a 50 nm diameter AuNP. After fitting the numerical absorption data with the equation of a driven damped harmonic oscillator (HO), it was found that the AFM tip modifies both the driving force (F0), consisting of the free carrier charge (q) and the driving field (E), and the overall damping of the oscillator (β). The enhancement or suppression of absorption with different tips can be understood in terms of competition between β and F0. Introducing the metallic tip increases β and decreases F0, resulting in reduced absorption. Introducing the dielectric tip, although it increases β, it also increases F0, resulting in overall absorption enhancement. Therefore, one most consider both β and F0 to control the absorption of nanoparticles under Surface Plasmon Polaritons.

  7. Modification of galactitol dehydrogenase from Rhodobacter sphaeroides D for immobilization on polycrystalline gold surfaces.

    PubMed

    Kornberger, P; Gajdzik, J; Natter, H; Wenz, G; Giffhorn, F; Kohring, G W; Hempelmann, R

    2009-10-20

    Galactitol dehydrogenase (GatDH) from Rhodobacter sphaeroides is a multifunctional enzyme that catalyzes in the presence of oxidized beta-nicotinamide adenine dinucleotide (NAD(+)) the interconversion of various multivalent aliphatic alcohols to the corresponding ketones. The recombinant GatDH was provided with an N-terminal His(6)-tag to which distally up to three cysteine residues were attached. This protein construct maintained nearly full enzymatic activity, and it could be covalently immobilized via thiol bonds onto the surface of a gold electrode. Binding of GatDH onto the gold electrode was verified by SPR measurements, and residual enzyme activity was measured by cyclic voltammetry using 1,2-hexanediol as substrate, the cofactor NAD(+) and the redox mediator CTFM (4-carboxy-2,5,7-trinitrofluorenyliden-malonnitrile) in solute form. The results demonstrate the possibility of a directed functional immobilization of proteins on gold surfaces, which represents a proof-of-concept for the development of reactors for electrochemical synthon preparation using dehydrogenases.

  8. Probing the effect of surface chemistry on the electrical properties of ultrathin gold nanowire sensors

    NASA Astrophysics Data System (ADS)

    Kisner, Alexandre; Heggen, Marc; Mayer, Dirk; Simon, Ulrich; Offenhäusser, Andreas; Mourzina, Yulia

    2014-04-01

    Ultrathin metal nanowires are ultimately analytical tools that can be used to survey the interfacial properties of the functional groups of organic molecules immobilized on nanoelectrodes. The high ratio of surface to bulk atoms makes such ultrathin nanowires extremely electrically sensitive to adsorbates and their charge and/or polarity, although little is known about the nature of surface chemistry interactions on metallic ultrathin nanowires. Here we report the first studies about the effect of functional groups of short-chain alkanethiol molecules on the electrical resistance of ultrathin gold nanowires. We fabricated ultrathin nanowire electrical sensors based on chemiresistors using conventional microfabrication techniques, so that the contact areas were passivated to leave only the surface of the nanowires exposed to the environment. By immobilizing alkanethiol molecules with head groups such as -CH3, -NH2 and -COOH on gold nanowires, we examined how the charge proximity due to protonation/deprotonation of the functional groups affects the resistance of the sensors. Electrical measurements in air and in water only indicate that beyond the gold-sulfur moiety interactions, the interfacial charge due to the acid-base chemistry of the functional groups of the molecules has a significant impact on the electrical resistance of the wires. Our data demonstrate that the degree of dissociation of the corresponding functional groups plays a major role in enhancing the surface-sensitive resistivity of the nanowires. These results stress the importance of recognizing the effect of protonation/deprotonation of the surface chemistry on the resulting electrical sensitivity of ultrathin metal nanowires and the applicability of such sensors for studying interfacial properties using electrodes of comparable size to the electrochemical double layer.Ultrathin metal nanowires are ultimately analytical tools that can be used to survey the interfacial properties of the functional

  9. Environment effects on surface-plasmon spectra in gold-island films potential for sensing applications

    SciTech Connect

    Meriaudeau, F.; Downey, T.R.; Passian, A.; Wig, A.; Ferrell, T.L.

    1998-12-01

    The effects of the local dielectric environment on the surface-plasmon resonances of annealed gold-island films as a potential for sensing applications are studied experimentally and modeled theoretically. Gold-island films were annealed at 600{degree}C to produce spheroidal shape particles that exhibit well-resolved resonances in polarized, angle-resolved, absorption spectra. These resonances are shifted in different amounts by the depolarization effect of the surrounding medium (liquids with various refraction indices). Cross-section calculations based on nonretarded, single-particle, dielectric interaction for these various configurations are presented and are found to be in good agreement with the experimental observations. The results show an interesting potential for biosensing or environmental monitoring applications. {copyright} 1998 Optical Society of America

  10. Fabrication of surface plasmon resonators by nanoskiving single-crystalline gold microplates

    NASA Astrophysics Data System (ADS)

    Wiley, Benjamin J.; Lipomi, Darren J.; Bao, Jiming; Capasso, Federico; Whitesides, George M.

    2009-02-01

    This paper demonstrates the sectioning of chemically synthesized, single-crystalline microplates of gold with an ultramicrotome to produce single-crystalline nanowires. This method produces collinearly aligned nanostructures with small, regular changes in dimension with each consecutive cross-section. The diamond knife cuts cleanly through microplates 100 nm thick without bending the resulting nanowire, and cuts through the sharp edges of a crystal to generate nanoscale tips. This paper demonstrates that the smooth surface of the single-crystalline gold nanowires allows them to guide plasmons with lower loss than rough, polycrystalline nanowires, and that the sharp tips on the singlecrystalline nanowires serve as optical antenna that selectively couple light into the nanowire at the resonance frequency of the sharp tip.

  11. Photon emission via surface state at the gold/acetonitrile solution interface

    SciTech Connect

    Uosaki, Kohei; Murakoshi, Kei; Kita, Hideaki )

    1991-01-24

    The emission of light caused by an electron-transfer reaction at a gold electrode in acetonitrile solution containing one of three redox species (benzophenone, trans-stilbene, and benzonitrile) with different redox potentials was studied. The high-energy threshold of the spectrum decreases linearly as the potential of the gold electrode becomes more negative. The peak position with respect to the high-energy threshold of the spectrum varies with electrode potential and is not affected by the redox potential of the electron injection species at the same electrode potential. The emission efficiency also depends on the potential. From these results, the authors proposed that the emission is due to a charge-transfer reaction inverse photoemission (CTRIP) process that takes place via a surface state.

  12. Fabrication of gold nanorods with tunable longitudinal surface plasmon resonance peaks by reductive dopamine.

    PubMed

    Su, Gaoxing; Yang, Chi; Zhu, Jun-Jie

    2015-01-20

    Hydroxyphenol compounds are often used as reductants in controlling the growth of nanoparticles. Herein, dopamine was used as an effective reductant in seed-mediated synthesis of gold nanorods (GNRs). The as-prepared GNRs (83 × 16 nm) were monodisperse and had a high degree of purity. The conversion ratio from gold ions to GNRs was around 80%. In addition, dopamine worked as an additive. At a very low concentration of hexadecyltrimethylammonium bromide (CTAB; 0.025 M), thinner and shorter GNRs (60 × 9 nm) were successfully prepared. By regulating the concentration of silver ions, CTAB, seeds, and reductant, GNRs with longitudinal surface plasmon resonance (LSPR) peaks ranging from 680 to 1030 nm were synthesized. The growth process was tracked using UV-vis-NIR spectroscopy, and it was found that a slow growth rate was beneficial to the formation of GNRs. PMID:25521416

  13. Probing the effect of surface chemistry on the electrical properties of ultrathin gold nanowire sensors.

    PubMed

    Kisner, Alexandre; Heggen, Marc; Mayer, Dirk; Simon, Ulrich; Offenhäusser, Andreas; Mourzina, Yulia

    2014-05-21

    Ultrathin metal nanowires are ultimately analytical tools that can be used to survey the interfacial properties of the functional groups of organic molecules immobilized on nanoelectrodes. The high ratio of surface to bulk atoms makes such ultrathin nanowires extremely electrically sensitive to adsorbates and their charge and/or polarity, although little is known about the nature of surface chemistry interactions on metallic ultrathin nanowires. Here we report the first studies about the effect of functional groups of short-chain alkanethiol molecules on the electrical resistance of ultrathin gold nanowires. We fabricated ultrathin nanowire electrical sensors based on chemiresistors using conventional microfabrication techniques, so that the contact areas were passivated to leave only the surface of the nanowires exposed to the environment. By immobilizing alkanethiol molecules with head groups such as -CH3, -NH2 and -COOH on gold nanowires, we examined how the charge proximity due to protonation/deprotonation of the functional groups affects the resistance of the sensors. Electrical measurements in air and in water only indicate that beyond the gold-sulfur moiety interactions, the interfacial charge due to the acid-base chemistry of the functional groups of the molecules has a significant impact on the electrical resistance of the wires. Our data demonstrate that the degree of dissociation of the corresponding functional groups plays a major role in enhancing the surface-sensitive resistivity of the nanowires. These results stress the importance of recognizing the effect of protonation/deprotonation of the surface chemistry on the resulting electrical sensitivity of ultrathin metal nanowires and the applicability of such sensors for studying interfacial properties using electrodes of comparable size to the electrochemical double layer.

  14. Below melting point photothermal reshaping of single gold nanorods driven by surface diffusion.

    PubMed

    Taylor, Adam B; Siddiquee, Arif M; Chon, James W M

    2014-12-23

    Plasmonic gold nanorod instability and reshaping behavior below melting points are important for many future applications but are yet to be fully understood, with existing nanoparticle melting theories unable to explain the observations. Here, we have systematically studied the photothermal reshaping behavior of gold nanorods irradiated with femtosecond laser pulses to report that the instability is driven by curvature-induced surface diffusion rather than a threshold melting process, and that the stability dramatically decreases with increasing aspect ratio. We successfully utilized the surface diffusion model to explain the observations and found that the activation energy for surface diffusion was dependent on the aspect ratio of the rods, from 0.6 eV for aspect ratio of 5 to 1.5 eV for aspect ratio less than 3. This result indicates that the surface atoms are much easier to diffuse around in larger aspect ratio rods than in shorter rods and can induce reshaping at any given temperature. Current plasmonics and nanorod applications with the sharp geometric features used for greater field enhancement will therefore need to consider surface diffusion driven shape change even at low temperatures.

  15. Formation of gold nanostructures on copier paper surface for cost effective SERS active substrate - Effect of halide additives

    NASA Astrophysics Data System (ADS)

    Desmonda, Christa; Kar, Sudeshna; Tai, Yian

    2016-03-01

    In this study, we report the simple fabrication of an active substrate assisted by gold nanostructures (AuNS) for application in surface-enhanced Raman scattering (SERS) using copier paper, which is a biodegradable and cost-effective material. As cellulose is the main component of paper, it can behave as a reducing agent and as a capping molecule for the synthesis of AuNS on the paper substrate. AuNS can be directly generated on the surface of the copier paper by addition of halides. The AuNS thus synthesized were characterized by ultraviolet-visible spectroscopy, SEM, XRD, and XPS. In addition, the SERS effect of the AuNS-paper substrates synthesized by using various halides was investigated by using rhodamine 6G and melamine as probe molecules.

  16. Gold Nanosphere-Deposited Substrate for Distinguishing of Breast Cancer Subtypes Using Surface-Enhanced Raman Spectroscopy.

    PubMed

    Hossain, Md Khaled; Cho, Hyeon-Yeol; Choi, Jeong-Woo

    2016-06-01

    Raman spectroscopy, as a nondestructive spectral technique, served as an efficient tool for investigating the molecular information of complex biological systems including cells. But the limitation of the technique is its low signal intensity. This inherent problem can be overcomed by using surface-enhanced Raman scattering (SERS) technique. SERS can be achieved by roughening the surface of a substrate with noble metal nanoparticles. But preparation of homogenous SERS substrate with higher enhancement property is a big challenge. In this study, we report a homogenous gold (Au) nanosphere deposited ITO substrate that can significantly increase the Raman signals from analytes. By using this substrate we successfully characterize and distinguish two different sub-types of breast cancer cells. SERS method is simple, label free and non-toxic. Our newly developed Au nanosphere deposited substrate can be used as an effective platform for molecular detection, characterization, and distinguishing different cells originated from same or different organs. PMID:27427706

  17. Extreme ultraviolet reflection efficiencies of diamond-turned aluminum, polished nickel, and evaporated gold surfaces. [for telescope mirrors

    NASA Technical Reports Server (NTRS)

    Malina, R. F.; Cash, W.

    1978-01-01

    Measured reflection efficiencies are presented for flat samples of diamond-turned aluminum, nickel, and evaporated gold surfaces fabricated by techniques suited for EUV telescopes. The aluminum samples were 6.2-cm-diameter disks of 6061-T6, the electroless nickel samples were formed by plating beryllium disks with 7.5-microns of Kanigen. Gold samples were produced by coating the aluminum and nickel samples with 5 strips of evaporated gold. Reflection efficiencies are given for grazing angles in the 5-75 degree range. The results indicate that for wavelengths over about 100 A, the gold-coated nickel samples yield highest efficiencies. For shorter wavelengths, the nickel samples yield better efficiencies. 500 A is found to be the optimal gold thickness.

  18. High relaxivity Gd(III)-DNA gold nanostars: investigation of shape effects on proton relaxation.

    PubMed

    Rotz, Matthew W; Culver, Kayla S B; Parigi, Giacomo; MacRenaris, Keith W; Luchinat, Claudio; Odom, Teri W; Meade, Thomas J

    2015-03-24

    Gadolinium(III) nanoconjugate contrast agents (CAs) have distinct advantages over their small-molecule counterparts in magnetic resonance imaging. In addition to increased Gd(III) payload, a significant improvement in proton relaxation efficiency, or relaxivity (r1), is often observed. In this work, we describe the synthesis and characterization of a nanoconjugate CA created by covalent attachment of Gd(III) to thiolated DNA (Gd(III)-DNA), followed by surface conjugation onto gold nanostars (DNA-Gd@stars). These conjugates exhibit remarkable r1 with values up to 98 mM(-1) s(-1). Additionally, DNA-Gd@stars show efficient Gd(III) delivery and biocompatibility in vitro and generate significant contrast enhancement when imaged at 7 T. Using nuclear magnetic relaxation dispersion analysis, we attribute the high performance of the DNA-Gd@stars to an increased contribution of second-sphere relaxivity compared to that of spherical CA equivalents (DNA-Gd@spheres). Importantly, the surface of the gold nanostar contains Gd(III)-DNA in regions of positive, negative, and neutral curvature. We hypothesize that the proton relaxation enhancement observed results from the presence of a unique hydrophilic environment produced by Gd(III)-DNA in these regions, which allows second-sphere water molecules to remain adjacent to Gd(III) ions for up to 10 times longer than diffusion. These results establish that particle shape and second-sphere relaxivity are important considerations in the design of Gd(III) nanoconjugate CAs.

  19. Gold-Induced Fibril Growth: The Mechanism of Surface-Facilitated Amyloid Aggregation.

    PubMed

    Gladytz, Anika; Abel, Bernd; Risselada, Herre Jelger

    2016-09-01

    The question of how amyloid fibril formation is influenced by surfaces is crucial for a detailed understanding of the process in vivo. We applied a combination of kinetic experiments and molecular dynamics simulations to elucidate how (model) surfaces influence fibril formation of the amyloid-forming sequences of prion protein SUP35 and human islet amyloid polypeptide. The kinetic data suggest that structural reorganization of the initial peptide corona around colloidal gold nanoparticles is the rate-limiting step. The molecular dynamics simulations reveal that partial physisorption to the surface results in the formation of aligned monolayers, which stimulate the formation of parallel, critical oligomers. The general mechanism implies that the competition between the underlying peptide-peptide and peptide-surface interactions must strike a balance to accelerate fibril formation. PMID:27513605

  20. Colloid-gold nanoparticle enhanced detection sensitivity of paired surface plasma waves biosensor

    NASA Astrophysics Data System (ADS)

    Wu, Hsieh-Ting; Chen, Yi-Ling; Huang, Yen-Chen; Liu, Wei-Chih; Ng, Ming-Yaw; Chang, Yin-Fong; Hsieh, Bao-Yu; Chou, Chien

    2007-02-01

    Previous work with amplitude-sensitive paired surface plasma waves biosensor (PSPWB) demonstrated that the detection sensitivity of PSPWB is able to experimentally detect 0.001% sucrose-water solution and biomolecular interaction of 10pg/ml mouse IgG interacting with immobilized anti-mouse IgG successfully. Further development of the detection sensitivity of PSPWB has been conducted by using 20nm in diameter colloid gold nanoparticles conjugated with target molecules that can result in a higher mass coverage and a larger resonant angle change of plasmon resonance, thereby its detection sensitivity is further enhanced significantly. Bare gold nanoparticles, which is randomly suspended in solution, is adopted to differentiate biospecific binding induced further signal enhancement. Experimentally, the sensitivity at 330fg/ml of Au-nanoparticle conjugated protein A (PA-Au) interacting with mouse IgG which is immobilized on a CM5 sensor chip was detected successfully. By this arrangement, 6-fold signal amplification is demonstrated compared with the same concentration of PA without conjugated gold nanoparticles.

  1. Robust Maleimide-Functionalized Gold Surfaces and Nanoparticles Generated Using Custom-Designed Bidentate Adsorbates.

    PubMed

    Park, Chul Soon; Lee, Han Ju; Jamison, Andrew C; Lee, T Randall

    2016-07-26

    A series of custom-designed alkanethioacetate ligands were synthesized to provide a facile method of attaching maleimide-terminated adsorbates to gold nanostructures via thiolate bonds. Monolayers on flat gold substrates derived from both mono- and dithioacetates, with and without oligo(ethylene glycol) (OEG) moieties in their alkyl spacers, were characterized using X-ray photoelectron spectroscopy, polarization modulation infrared reflection-absorption spectroscopy, ellipsometry, and contact angle goniometry. For all adsorbates, the resulting monolayers revealed that a higher packing density and more homogeneous surface were generated when the film was formed in EtOH, but a higher percentage of bound thiolate was obtained in THF. A series of gold nanoparticles (AuNPs) capped with each adsorbate were prepared to explore how adsorbate structure influences aqueous colloidal stability under extreme conditions, as examined visually and spectroscopically. The AuNPs coated with adsorbates that include OEG moieties exhibited enhanced stability under high salt concentration, and AuNPs capped with dithioacetate adsorbates exhibited improved stability against ligand exchange in competition with dithiothreitol (DTT). Overall, the best results were obtained with a chelating dithioacetate adsorbate that included OEG moieties in its alkyl spacer, imparting improved stability via enhanced solubility in water and superior adsorbate attachment owing to the chelate effect. PMID:27385466

  2. Charge carrier dynamics and surface plasmon interaction in gold nanorod-blended organic solar cell

    NASA Astrophysics Data System (ADS)

    Rana, Aniket; Gupta, Neeraj; Lochan, Abhiram; Sharma, G. D.; Chand, Suresh; Kumar, Mahesh; Singh, Rajiv K.

    2016-08-01

    The inclusion of plasmonic nanoparticles into organic solar cell enhances the light harvesting properties that lead to higher power conversion efficiency without altering the device configuration. This work defines the consequences of the nanoparticle overloading amount and energy transfer process between gold nanorod and polymer (active matrix) in organic solar cells. We have studied the hole population decay dynamics coupled with gold nanorods loading amount which provides better understanding about device performance limiting factors. The exciton and plasmon together act as an interacting dipole; however, the energy exchange between these two has been elucidated via plasmon resonance energy transfer (PRET) mechanism. Further, the charge species have been identified specifically with respect to their energy levels appearing in ultrafast time domain. The specific interaction of these charge species with respective surface plasmon resonance mode, i.e., exciton to transverse mode of oscillation and polaron pair to longitudinal mode of oscillations, has been explained. Thus, our analysis reveals that PRET enhances the carrier population density in polymer via non-radiative process beyond the concurrence of a particular plasmon resonance oscillation mode and polymer absorption range. These findings give new insight and reveal specifically the factors that enhance and control the performance of gold nanorods blended organic solar cells. This work would lead in the emergence of future plasmon based efficient organic electronic devices.

  3. Surface chemistry and structures of 1,4-phenylene diisocyanide on gold films from solution

    NASA Astrophysics Data System (ADS)

    Abuflaha, Rasha; Olson, Dustin; Bennett, Dennis W.; Tysoe, Wilfred T.

    2016-07-01

    The adsorption of 1,4-phenylene diisocyanide (PDI) is studied on gold films as a function of PDI exposure from benzene solution by a combination of attenuated total internal reflection infrared (ATR-IR) spectroscopy and conductivity measurements. The infrared spectrum found for low PDI doses exhibits a single isocyanide vibrational peak consistent with the formation of -(Au-PDI)- oligomer chains that have been identified previously on a Au(111) surface dosed in ultrahigh vacuum. Larger solution doses cause the isocyanide peaks to split into two, with the lower-frequency vibrations corresponding to a free isocyanide mode, indicating the formation of a perpendicular, vertically bonded PDI molecule. This observation also rationalizes the apparent disparity between studies of the chemistry of PDI on gold in ultrahigh vacuum and with solution dosing. Since it has been shown previously that the -(Au-PDI)- oligomer chains are capable of providing conductive linkages between gold nanoparticles on an insulating mica substrate, it was proposed that higher PDI doses from solution should cause a decrease in conductivity due to chain disruption. This effect was found experimentally, thereby providing corroborative evidence for the above conclusions.

  4. Nanostructured surfaces investigated by quantitative morphological studies

    NASA Astrophysics Data System (ADS)

    Perani, Martina; Carapezzi, Stefania; Rani Mutta, Geeta; Cavalcoli, Daniela

    2016-05-01

    The morphology of different surfaces has been investigated by atomic force microscopy and quantitatively analyzed in this paper. Two different tools have been employed to this scope: the analysis of the height-height correlation function and the determination of the mean grain size, which have been combined to obtain a complete characterization of the surfaces. Different materials have been analyzed: SiO x N y , InGaN/GaN quantum wells and Si nanowires, grown with different techniques. Notwithstanding the presence of grain-like structures on all the samples analyzed, they present very diverse surface design, underlying that this procedure can be of general use. Our results show that the quantitative analysis of nanostructured surfaces allows us to obtain interesting information, such as grain clustering, from the comparison of the lateral correlation length and the grain size.

  5. Gold nanoparticle-paper as a three-dimensional surface enhanced Raman scattering substrate.

    PubMed

    Ngo, Ying Hui; Li, Dan; Simon, George P; Garnier, Gil

    2012-06-12

    This work investigates the effect of gold nanoparticle (AuNP) addition to paper substrate and examines the ability of these composite materials to amplify the surface enhanced Raman scattering (SERS) signal of a dye adsorbed. Paper has a three-dimensional (3D), porous, and heterogeneous morphology. The manner in which paper adsorbs the nanoparticles is crucial to its SERS properties, particularly with regards to aggregation. In this work, we sought to maintain the same degree of aggregation, while changing the concentration of nanoparticles deposited on paper. We achieved this by dipping paper into AuNP solutions of different, known concentration and found that the initial packing density of AuNPs in solutions was retained on paper with the same degree of aggregation. The surface coverage of AuNPs on paper was found to scale linearly to their concentration profile in solutions. The SERS performances of the AuNP-treated papers were evaluated with 4-aminothiophenol (4-ATP) as the Raman molecule, and their SERS intensities increased linearly with the AuNPs' concentration. Compared to AuNP-treated silicon, the Raman enhancement factor (EF) from paper was relatively higher due to a more uniform and greater degree of adsorption of AuNPs. The effect of the spatial distribution of AuNPs in their substrates on SERS activity was also investigated. In this experiment, the number of AuNPs was kept constant (a 1 μL droplet of AuNPs was deposited on all substrates), and the distribution profile of AuNPs was controlled by the nature of the substrate: paper, silicon, and hydrophobized paper. The AuNP droplet on paper showed the most reproducible and sensitive SERS signal. This highlighted the role of the z-distribution (through film) of AuNPs within the bulk of the paper, producing a 3D multilayer structure to allow inter- and intralayer plasmon coupling, and hence amplifying the SERS signal. The SERS performance of nanoparticle-functionalized paper can thus be optimized by

  6. Gold nanoparticle-paper as a three-dimensional surface enhanced Raman scattering substrate.

    PubMed

    Ngo, Ying Hui; Li, Dan; Simon, George P; Garnier, Gil

    2012-06-12

    This work investigates the effect of gold nanoparticle (AuNP) addition to paper substrate and examines the ability of these composite materials to amplify the surface enhanced Raman scattering (SERS) signal of a dye adsorbed. Paper has a three-dimensional (3D), porous, and heterogeneous morphology. The manner in which paper adsorbs the nanoparticles is crucial to its SERS properties, particularly with regards to aggregation. In this work, we sought to maintain the same degree of aggregation, while changing the concentration of nanoparticles deposited on paper. We achieved this by dipping paper into AuNP solutions of different, known concentration and found that the initial packing density of AuNPs in solutions was retained on paper with the same degree of aggregation. The surface coverage of AuNPs on paper was found to scale linearly to their concentration profile in solutions. The SERS performances of the AuNP-treated papers were evaluated with 4-aminothiophenol (4-ATP) as the Raman molecule, and their SERS intensities increased linearly with the AuNPs' concentration. Compared to AuNP-treated silicon, the Raman enhancement factor (EF) from paper was relatively higher due to a more uniform and greater degree of adsorption of AuNPs. The effect of the spatial distribution of AuNPs in their substrates on SERS activity was also investigated. In this experiment, the number of AuNPs was kept constant (a 1 μL droplet of AuNPs was deposited on all substrates), and the distribution profile of AuNPs was controlled by the nature of the substrate: paper, silicon, and hydrophobized paper. The AuNP droplet on paper showed the most reproducible and sensitive SERS signal. This highlighted the role of the z-distribution (through film) of AuNPs within the bulk of the paper, producing a 3D multilayer structure to allow inter- and intralayer plasmon coupling, and hence amplifying the SERS signal. The SERS performance of nanoparticle-functionalized paper can thus be optimized by

  7. Colloidal stability of gold nanorod solution upon exposure to excised human skin: Effect of surface chemistry and protein adsorption.

    PubMed

    Mahmoud, Nouf N; Al-Qaoud, Khaled M; Al-Bakri, Amal G; Alkilany, Alaaldin M; Khalil, Enam A

    2016-06-01

    In this study, we evaluated the colloidal stability of gold nanorods (with positive, negative and neutral surface charge) in solution upon contact with excised human skin. UV-vis absorption, plasmon peak broadening index (PPBI%) and transmission electron microscope analysis were used to follow nanoparticles aggregation in solution. Our results show that positively charged gold nanorods aggregate extensively upon exposure to excised human skin compared to negatively and neutrally charged gold nanorods. Skin-induced aggregation of cationic gold nanorods was linked to the adsorption of proteins released from the dermis layer to the surface of gold nanorods. Protein adsorption significantly screen nanorod's effective surface charge and induce their aggregation. Moreover, we demonstrate that the presence of polyethylene glycol polymer on the surface of cationic gold nanorods minimize this aggregation significantly by providing steric repulsion (non-electrostatic stabilization mechanism). This work highlights the importance of evaluating the colloidal stability of nanoparticles in solution upon contact with skin, which is a "usually overlooked" parameter when studying the nanoparticle-skin interaction. PMID:26923289

  8. Investigation of the nonlinear refractive index of single-crystalline thin gold films and plasmonic nanostructures

    NASA Astrophysics Data System (ADS)

    Goetz, Sebastian; Razinskas, Gary; Krauss, Enno; Dreher, Christian; Wurdack, Matthias; Geisler, Peter; Pawłowska, Monika; Hecht, Bert; Brixner, Tobias

    2016-04-01

    The nonlinear refractive index of plasmonic materials may be used to obtain nonlinear functionality, e.g., power-dependent switching. Here, we investigate the nonlinear refractive index of single-crystalline gold in thin layers and nanostructures on dielectric substrates. In a first step, we implement a z-scan setup to investigate ~100-µm-sized thin-film samples. We determine the nonlinear refractive index of fused silica, n 2(SiO2) = 2.9 × 10-20 m2/W, in agreement with literature values. Subsequent z-scan measurements of single-crystalline gold films reveal a damage threshold of 0.22 TW/cm2 and approximate upper limits of the real and imaginary parts of the nonlinear refractive index, | n 2'(Au)| < 1.2 × 10-16 m2/W and | n 2″(Au)| < 0.6 × 10-16 m2/W, respectively. To further determine possible effects of a nonlinear refractive index in plasmonic circuitry, interferometry is proposed as a phase-sensitive probe. In corresponding nanostructures, relative phase changes between two propagating near-field modes are converted to amplitude changes by mode interference. Power-dependent experiments using sub-10-fs near-infrared pulses and diffraction-limited resolution (NA = 1.4) reveal linear behavior up to the damage threshold (0.23 times relative to that of a solid single-crystalline gold film). An upper limit for the nonlinear power-dependent phase change between two propagating near-field modes is determined to Δ φ < 0.07 rad.

  9. Investigating the Toxicity, Uptake, Nanoparticle Formation and Genetic Response of Plants to Gold

    PubMed Central

    Taylor, Andrew F.; Rylott, Elizabeth L.; Anderson, Christopher W. N.; Bruce, Neil C.

    2014-01-01

    We have studied the physiological and genetic responses of Arabidopsis thaliana L. (Arabidopsis) to gold. The root lengths of Arabidopsis seedlings grown on nutrient agar plates containing 100 mg/L gold were reduced by 75%. Oxidized gold was subsequently found in roots and shoots of these plants, but gold nanoparticles (reduced gold) were only observed in the root tissues. We used a microarray-based study to monitor the expression of candidate genes involved in metal uptake and transport in Arabidopsis upon gold exposure. There was up-regulation of genes involved in plant stress response such as glutathione transferases, cytochromes P450, glucosyl transferases and peroxidases. In parallel, our data show the significant down-regulation of a discreet number of genes encoding proteins involved in the transport of copper, cadmium, iron and nickel ions, along with aquaporins, which bind to gold. We used Medicago sativa L. (alfalfa) to study nanoparticle uptake from hydroponic culture using ionic gold as a non-nanoparticle control and concluded that nanoparticles between 5 and 100 nm in diameter are not directly accumulated by plants. Gold nanoparticles were only observed in plants exposed to ionic gold in solution. Together, we believe our results imply that gold is taken up by the plant predominantly as an ionic form, and that plants respond to gold exposure by up-regulating genes for plant stress and down-regulating specific metal transporters to reduce gold uptake. PMID:24736522

  10. Investigating the toxicity, uptake, nanoparticle formation and genetic response of plants to gold.

    PubMed

    Taylor, Andrew F; Rylott, Elizabeth L; Anderson, Christopher W N; Bruce, Neil C

    2014-01-01

    We have studied the physiological and genetic responses of Arabidopsis thaliana L. (Arabidopsis) to gold. The root lengths of Arabidopsis seedlings grown on nutrient agar plates containing 100 mg/L gold were reduced by 75%. Oxidized gold was subsequently found in roots and shoots of these plants, but gold nanoparticles (reduced gold) were only observed in the root tissues. We used a microarray-based study to monitor the expression of candidate genes involved in metal uptake and transport in Arabidopsis upon gold exposure. There was up-regulation of genes involved in plant stress response such as glutathione transferases, cytochromes P450, glucosyl transferases and peroxidases. In parallel, our data show the significant down-regulation of a discreet number of genes encoding proteins involved in the transport of copper, cadmium, iron and nickel ions, along with aquaporins, which bind to gold. We used Medicago sativa L. (alfalfa) to study nanoparticle uptake from hydroponic culture using ionic gold as a non-nanoparticle control and concluded that nanoparticles between 5 and 100 nm in diameter are not directly accumulated by plants. Gold nanoparticles were only observed in plants exposed to ionic gold in solution. Together, we believe our results imply that gold is taken up by the plant predominantly as an ionic form, and that plants respond to gold exposure by up-regulating genes for plant stress and down-regulating specific metal transporters to reduce gold uptake. PMID:24736522

  11. Surface plasmon and photonic mode propagation in gold nanotubes with varying wall thickness

    SciTech Connect

    Kohl, Jesse; Fireman, Micha; O'Carroll, Deirdre M.

    2011-12-15

    Gold nanotube arrays are synthesized with a range of wall thicknesses (15 to >140 nm) and inner diameters of {approx}200 nm using a hard-template method. A red spectral shift (>0.39 eV) with decreasing wall thickness is observed in dark-field spectra of nanotube arrays and single nanowire/nanotube heterostructures. Finite-difference-time-domain simulations show that nanotubes in this size regime support propagating surface plasmon modes as well as surface plasmon ring resonances at visible wavelengths (the latter is observed only for excitation directions normal to the nanotube long axis with transverse polarization). The energy of the surface plasmon modes decreases with decreasing wall thickness and is attributed to an increase in mode coupling between propagating modes in the nanotube core and outer surface and the circumference dependence of ring resonances. Surface plasmon mode propagation lengths for thicker-walled tubes increase by a factor of {approx}2 at longer wavelengths (>700 nm), where ohmic losses in the metal are low, but thinner-walled tubes (30 nm) exhibit a more significant increase in surface plasmon propagation length (by a factor of more than four) at longer wavelengths. Additionally, nanotubes in this size regime support a photonic mode in their core, which does not change in energy with changing wall thickness. However, photonic mode propagation length is found to decrease for optically thin walls. Finally, correlations are made between the experimentally observed changes in dark-field spectra and the changes in surface plasmon mode properties observed in simulations for the various gold nanotube wall thicknesses and excitation conditions.

  12. The optical, photothermal, and facile surface chemical properties of gold and silver nanoparticles in biodiagnostics, therapy, and drug delivery

    PubMed Central

    Austin, Lauren A.; Mackey, Megan A.; Dreaden, Erik C.

    2014-01-01

    Nanotechnology is a rapidly growing area of research in part due to its integration into many biomedical applications. Within nanotechnology, gold and silver nanostructures are some of the most heavily utilized nanomaterial due to their unique optical, photothermal, and facile surface chemical properties. In this review, common colloid synthesis methods and biofunctionalization strategies of gold and silver nanostructures are highlighted. Their unique properties are also discussed in terms of their use in biodiagnostic, imaging, therapeutic, and drug delivery applications. Furthermore, relevant clinical applications utilizing gold and silver nanostructures are also presented. We also provide a table with reviews covering related topics. PMID:24894431

  13. The gold/high temperature superconductor interface: Metallicity of the near surface region and a search for the proximity effect

    SciTech Connect

    Dessau, D.S.; Shen, Z.X.; Wells, B.O.; Spicer, W.E. . Stanford Electronics Labs.); List, R.S.; Arko, A.J.; Bartlett, R.J.; Fisk, Z.; Cheong, S.W. ); Olson, C.G. ); Mitzi, D.B.; Eom, C.B.; Kapitulnik, A.; Geballe, T.H. . Dept. of Applied Physics); Schirber, J.E. (Sandia National Labs., Albuquerque, NM (U

    1990-01-01

    We have used high resolution photoemission spectroscopy to probe the electronic structure of a wide variety of gold/high temperature superconductor interfaces, the majority of which were formed by low-temperature (20K) gold evaporations on cleaved high quality single crystals. For c-axis interfaces formed on the 123 family of superconductors, we find that the gold deposition essentially destroys the metallicity of the superconducting substrate in the near surface region ({approximately}5{angstrom}), while the near surface region of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} remains metallic. We have also used photoemission spectroscopy to search for a proximity-effect superconducting gap in gold overlayers on c-axis single crystals and a-axis thin films, though no such effect was found. 30 refs., 6 figs.

  14. Label-free, zeptomole cancer biomarker detection by surface-enhanced fluorescence on nanoporous gold disk plasmonic nanoparticles.

    PubMed

    Santos, Greggy M; Zhao, Fusheng; Zeng, Jianbo; Li, Ming; Shih, Wei-Chuan

    2015-10-01

    We experimentally demonstrate a label-free biosensor for the ERBB2 cancer gene DNA target based on the distance-dependent detection of surface-enhanced fluorescence (SEF) on nanoporous gold disk (NPGD) plasmonic nanoparticles. We achieve detection of 2.4 zeptomole of DNA target on the NPGD substrate with an upper concentration detection limit of 1 nM. Without the use of molecular spacers, the NPGD substrate as an SEF platform was shown to provide higher net fluorescence for visible and NIR fluorophores compared to glass and non-porous gold substrates. The enhanced fluorescence signals in patterned nanoporous gold nanoparticles make NPGD a viable material for further reducing detection limits for biomolecular targets used in clinical assays. With patterned nanoporous gold disk (NPGD) plasmonic nanoparticles, a label-free biosensor that makes use of distance-dependent detection of surface-enhanced fluorescence (SEF) is constructed and tested for zeptomole detection of ERBB2 cancer gene DNA targets.

  15. Preparation of ferrocene-functionalized gold nanoparticles by primer extension reaction on the particle surface.

    PubMed

    Takada, Tadao; Tochi, Takaaki; Nakamura, Mitsunobu; Yamana, Kazushige

    2014-06-15

    DNA molecules possessing multiple ferrocene (Fc) molecules as a redox active probe were prepared by the primer extension (PEX) reaction using a 2'-deoxyuridine-5'-triphosphate derivative in which Fc was connected to the C5-position of the uridine by a diethylene glycol linker. Gold nanoparticles (AuNP) covered with DNA possessing the Fc molecules were prepared by the PEX reaction on the surface. The AuNP-FcDNA conjugates exhibit a detectable electrochemical signal due to the Fc molecules. Possible application of the PEX reaction on AuNP is demonstrated for the detection of a single nucleotide mutation in the target DNA.

  16. Design, Synthesis and Characterization of Nucleic Acid-Functionalized Gold Surfaces for Biomarker Detection

    PubMed Central

    Adams, Nicholas M.; Jackson, Stephen R.; Haselton, Frederick R.; Wright, David W.

    2014-01-01

    Nucleic acid-functionalized gold surfaces have been used extensively for the development of biological sensors. The development of an effective biomarker detection assay requires careful design, synthesis and characterization of probe components. In this feature article, we describe fundamental probe development constraints and provide a critical appraisal of the current methodologies and applications in the field. We discuss critical issues and obstacles that impede the sensitivity and reliability of the sensors to underscore the challenges that must be met to advance the field of biomarker detection. PMID:21905721

  17. Dendrimer-Capped Gold Nanoparticles for Highly Reliable and Robust Surface Enhanced Raman Scattering.

    PubMed

    Kim, Kwanghyun; Lee, Jeongyeop; Jo, Gyeongcheon; Shin, Seungmin; Kim, Jin-Baek; Jang, Ji-Hyun

    2016-08-10

    Dendrimer-stabilized gold nanoparticles (Au-Den) were prepared by a facile solution based method for a highly reliable and robust surface enhanced Raman scattering (SERS) substrate. Au-Den was selectively attached on the surface of reduced graphene oxide (rGO) by noncovalent interactions between the Au capping dendrimer and the graphene surface. Au-Den/rGO exhibits the outstandingly stable and highly magnified Raman signal with an enhancement factor (EF) of 3.9 × 10(7) that enables detection of R6G dyes with concentration as low as 10 nM, retaining 95% of the Raman signal intensity after 1 year. The remarkable stability and enhancement originated not only from a simple combination of the electromagnetic and chemical mechanism of SERS but also from intensified packing density of stable Au-Den on the graphene substrate due to the firm binding between the dendrimer capped metal nanoparticles and the graphene substrate. This method is not limited to the gold nanoparticles and G4 dendrimer used herein, but also can be applied to other dendrimers and metal nanoparticles, which makes the material platform suggested here superior to other SERS substrates. PMID:27403733

  18. Facile Synthesis of Uniform Raspberry-Like Gold Nanoparticles for High Performance Surface Enhanced Raman Scattering.

    PubMed

    Rong, Yun; Zhang, Lei; Liu, Zhenzhong; Dai, Liwei; Huang, Youju; Chen, Tao

    2016-06-01

    Hierarchical Au nanostructures have attracted considerable attention owing to their rich hot-spots in inherent structures that have found various applications in surface-enhanced Raman scattering (SERS) based sensing and imaging. Herein we facilely synthesized uniform hierarchical raspberry-like Au nanostructures with tunable size via a seed-mediated growth approach employing a binary mixture of quaternized chitosan (QCS) and 5-bromosalicylic acid (5-BrSA). 5-BrSA plays an important role in tuning shapes and improving uniformity of resultant gold nanoparticles (AuNPs). The obtained raspberry-like Au nanostructures have a spherical profile and randomly arranged protrusions on the outsides, and their size can be finely tuned in a range from 50 to 120 nm. The rough surfaces of the special raspberry-like Au nanostructures endow them higher SERS performance than spherical Au spheres with smooth surfaces, which is promising for the application of SERS based sensors and optical imaging. PMID:27427615

  19. Application of image quality metamerism to investigate gold color area in cultural property

    NASA Astrophysics Data System (ADS)

    Miyata, Kimiyoshi; Tsumura, Norimichi

    2013-01-01

    A concept of image quality metamerism as an expansion of conventional metamerism defined in color science is introduced, and it is applied to segment similar color areas in a cultural property. The image quality metamerism can unify different image quality attributes based on an index showing the degree of image quality metamerism proposed. As a basic research step, the index is consisted of color and texture information and examined to investigate a cultural property. The property investigated is a pair of folding screen paintings that depict the thriving city of Kyoto designated as a nationally important cultural property in Japan. Gold-colored areas painted by using high granularity colorants compared with other color areas are evaluated based on the image quality metamerism index locally, then the index is visualized as a map showing the possibility of the image quality metamer to the reference pixel set in the same image. This visualization means a segmentation of areas where color is similar but texture is different. The experimental result showed that the proposed method was effective to show areas of gold color areas in the property.

  20. Nanoporous Gold as a Neural Interface Coating: Effects of Topography, Surface Chemistry, and Feature Size

    SciTech Connect

    Chapman, Christopher A. R.; Chen, Hao; Stamou, Marianna; Biener, Juergen; Biener, Monika M.; Lein, Pamela J.; Seker, Erkin

    2015-02-23

    We report that designing neural interfaces that maintain close physical coupling of neurons to an electrode surface remains a major challenge for both implantable and in vitro neural recording electrode arrays. Typically, low-impedance nanostructured electrode coatings rely on chemical cues from pharmaceuticals or surface-immobilized peptides to suppress glial scar tissue formation over the electrode surface (astrogliosis), which is an obstacle to reliable neuron–electrode coupling. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a promising candidate to reduce astrogliosis solely through topography by taking advantage of its tunable length scale. In the present in vitro study on np-Au’s interaction with cortical neuron–glia co-cultures, we demonstrate that the nanostructure of np-Au achieves close physical coupling of neurons by maintaining a high neuron-to-astrocyte surface coverage ratio. Atomic layer deposition-based surface modification was employed to decouple the effect of morphology from surface chemistry. Additionally, length scale effects were systematically studied by controlling the characteristic feature size of np-Au through variations in the dealloying conditions. In conclusion, our results show that np-Au nanotopography, not surface chemistry, reduces astrocyte surface coverage while maintaining high neuronal coverage and may enhance neuron–electrode coupling through nanostructure-mediated suppression of scar tissue formation.

  1. Nanoporous Gold as a Neural Interface Coating: Effects of Topography, Surface Chemistry, and Feature Size

    DOE PAGESBeta

    Chapman, Christopher A. R.; Chen, Hao; Stamou, Marianna; Biener, Juergen; Biener, Monika M.; Lein, Pamela J.; Seker, Erkin

    2015-02-23

    We report that designing neural interfaces that maintain close physical coupling of neurons to an electrode surface remains a major challenge for both implantable and in vitro neural recording electrode arrays. Typically, low-impedance nanostructured electrode coatings rely on chemical cues from pharmaceuticals or surface-immobilized peptides to suppress glial scar tissue formation over the electrode surface (astrogliosis), which is an obstacle to reliable neuron–electrode coupling. Nanoporous gold (np-Au), produced by an alloy corrosion process, is a promising candidate to reduce astrogliosis solely through topography by taking advantage of its tunable length scale. In the present in vitro study on np-Au’s interactionmore » with cortical neuron–glia co-cultures, we demonstrate that the nanostructure of np-Au achieves close physical coupling of neurons by maintaining a high neuron-to-astrocyte surface coverage ratio. Atomic layer deposition-based surface modification was employed to decouple the effect of morphology from surface chemistry. Additionally, length scale effects were systematically studied by controlling the characteristic feature size of np-Au through variations in the dealloying conditions. In conclusion, our results show that np-Au nanotopography, not surface chemistry, reduces astrocyte surface coverage while maintaining high neuronal coverage and may enhance neuron–electrode coupling through nanostructure-mediated suppression of scar tissue formation.« less

  2. 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.

  3. Surface-Enhanced Raman Spectroscopy Study of 4-ATP on Gold Nanoparticles for Basal Cell Carcinoma Fingerprint Detection

    NASA Astrophysics Data System (ADS)

    Quynh, Luu Manh; Nam, Nguyen Hoang; Kong, K.; Nhung, Nguyen Thi; Notingher, I.; Henini, M.; Luong, Nguyen Hoang

    2016-05-01

    The surface-enhanced Raman signals of 4-aminothiophenol (4-ATP) attached to the surface of colloidal gold nanoparticles with size distribution of 2 to 5 nm were used as a labeling agent to detect basal cell carcinoma (BCC) of the skin. The enhanced Raman band at 1075 cm-1 corresponding to the C-S stretching vibration in 4-ATP was observed during attachment to the surface of the gold nanoparticles. The frequency and intensity of this band did not change when the colloids were conjugated with BerEP4 antibody, which specifically binds to BCC. We show the feasibility of imaging BCC by surface-enhanced Raman spectroscopy, scanning the 1075 cm-1 band to detect the distribution of 4-ATP-coated gold nanoparticles attached to skin tissue ex vivo.

  4. Influence of metal-support interaction on the surface structure of gold nanoclusters deposited on native SiO(x)/Si substrates.

    PubMed

    Portale, Giuseppe; Sciortino, Luisa; Albonetti, Cristiano; Giannici, Francesco; Martorana, Antonino; Bras, Wim; Biscarini, Fabio; Longo, Alessandro

    2014-04-14

    The structure of small gold nanoclusters (around 2.5 nm) deposited on different silica-on-silicon (SiOx/Si) substrates is investigated using several characterization techniques (AFM, XRD, EXAFS and GISAXS). The grain morphology and the surface roughness of the deposited gold cluster layers are determined by AFM. The in-plane GISAXS intensity is modelled in order to obtain information about the cluster size and the characteristic length scale of the surface roughness. The surface morphology of the deposited clusters depends on whether the native defect-rich (n-SiOx/Si) or the defect-poor substrate obtained by thermal treatment (t-SiO2/Si) is used. Gold clusters show a stronger tendency to aggregate when deposited on n-SiOx/Si, resulting in films characterized by a larger grain dimension (around 20 nm) and by a higher surface roughness (up to 5 nm). The more noticeable cluster aggregation on n-SiOx/Si substrates is explained in terms of metal-support interaction mediated by the defects located on the surface of the native silica substrate. Evidence of metal-support interaction is provided by EXAFS, demonstrating the existence of an Au-O distance for clusters deposited on n-SiOx/Si that is not found on t-SiO2/Si.

  5. How surface reparation prevents catalytic oxidation of carbon monoxide on atomic gold at defective magnesium oxide surfaces.

    PubMed

    Töpfer, Kai; Tremblay, Jean Christophe

    2016-07-21

    In this contribution, we study using first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: (1) co-adsorption is weakly supported at F(0) and F(2+) defects but not at F(1+) sites, (2) electron redistribution from the F(0) vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, (3) a metastable carbonate intermediate can form on defects of the F(0) type, (4) only a small activation barrier exists for the highly favorable dissociation of CO2 from F(0), and (5) the moderate adsorption energy of the gold atom on the F(0) defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken in the first oxidation step. PMID:27345190

  6. Electrochemical functionalization of gold and silicon surfaces by a maleimide group as a biosensor for immunological application.

    PubMed

    Zhang, Xin; Tretjakov, Aleksei; Hovestaedt, Marc; Sun, Guoguang; Syritski, Vitali; Reut, Jekaterina; Volkmer, Rudolf; Hinrichs, Karsten; Rappich, Joerg

    2013-03-01

    In the present study we investigated the preparation of biofunctionalized surfaces using the direct electrochemical grafting of maleimidophenyl molecules with subsequent covalent immobilization of specific peptide to detect target antibody, thereby extending the application of the biosensing systems towards immunodiagnostics. Para-maleimidophenyl (p-MP) functional groups were electrochemically grafted on gold and silicon surfaces from solutions of the corresponding diazonium salt. A specially synthesized peptide modified with cysteine (Cys-peptide) was then immobilized on the p-MP grafted substrates by cross-linking between the maleimide groups and the sulfhydryl group of the cysteine residues. Accordingly, the Cys-peptide worked as an antigen that was able to bind specifically the target antibody (anti-GST antibody), while it was non-sensitive to a negative contrast antibody (i.e. anti-Flag β). The immobilization of both specific and non-specific antibodies on the Cys-peptide-modified surfaces was monitored by infrared spectroscopic ellipsometry, a quartz crystal microbalance integrated in flow injection analysis system and potentiometric response. The results obtained clearly demonstrated that the direct modification of a surface with maleimidophenyl provides a very simple and reliable way of preparing biofunctionalized surfaces suitable for the construction of immunological biosensors.

  7. Investigating the students' understanding of surface phenomena

    NASA Astrophysics Data System (ADS)

    Hamed, Kastro Mohamad

    1999-11-01

    This study investigated students' understanding of surface phenomena. The main purpose for conducting this research endeavor was to understand how students think about a complex topic about which they have little direct or formal instruction. The motivation for focusing on surface phenomena stemmed from an interest in integrating research and education. Despite the importance of surfaces and interfaces in research laboratories, in technological applications, and in everyday experiences, no previous systematic effort was done on pedagogy related to surface phenomena. The design of this research project was qualitative, exploratory, based on a Piagetian semi-structured clinical piloted interview, focused on obtaining a longitudinal view of the intended sample. The sampling was purposeful and the sample consisted of forty-four undergraduate students at Kansas State University. The student participants were enrolled in physics classes that spanned a wide academic spectrum. The data were analyzed qualitatively. The main themes that emerged from the analysis were: (a) students used analogies when confronted with novel situations, (b) students mixed descriptions and explanations, (c) students used the same explanation for several phenomena, (d) students manifested difficulties transferring the meaning of vocabulary across discipline boundaries, (e) in addition to the introductory chemistry classes, students used everyday experiences and job-related experiences as sources of knowledge, and (f) students' inquisitiveness and eagerness to investigate and discuss novel phenomena seemed to peak about the time students were enrolled in second year physics classes.

  8. (90377) SEDNA: INVESTIGATION OF SURFACE COMPOSITIONAL VARIATION

    SciTech Connect

    Barucci, M. A.; De Bergh, C.; Merlin, F.; Morea Dalle Ore, C.; Cruikshank, D.; Alvarez-Candal, A.; Dumas, C.

    2010-12-15

    The dwarf planet (90377) Sedna is one of the most remote solar system objects accessible to investigations. To better constrain its surface composition and to investigate the possible heterogeneity of the surface of Sedna, several observations have been carried out at ESO-VLT with the powerful spectrometer SINFONI observing simultaneously the H and K bands. The analyzed spectra (obtained in 2005, 2007, and 2008) show a non-uniform spectral signature, particularly in the K band. Spectral modeling using the Shkuratov radiative transfer code for surface scattering has been performed using the various sets of data, including previous observations at visible wavelengths and photometry at 3.6 and 4.5 {mu}m by the Spitzer Space Telescope. The visible and near-infrared spectra can be modeled with organic materials (triton and titan tholin), serpentine, and H{sub 2}O ice in fairly significant amounts, and CH{sub 4}, N{sub 2}, and C{sub 2}H{sub 6} in varying trace amounts. One of the spectra obtained in 2005 October shows a different signature in the K band and is best modeled with CH{sub 3}OH in place of CH{sub 4}, with reduced amounts of serpentine and with the addition of olivine. The compositional surface heterogeneity can give input on the past history as well clues to the origin of this peculiar, distant object.

  9. Ancient Parchment Examination by Surface Investigation Methods.

    PubMed

    Facchini; Malara; Bazzani; Cavallotti

    2000-11-15

    A restoring process was set up to restore flexibility, size, and shape in naturally aged or fire-damaged parchments of old manuscripts. Validation of such a process requires the measurement of intrinsic parchment properties and comparison of them before and after the treatment. To this aim, we investigated morphological, mechanical, and surface physico-chemical properties of parchment by taking SEM pictures and characterizing small samples by microindentation, mercury porosimetry, and water vapor adsorption/desorption isotherms. Copyright 2000 Academic Press.

  10. Colloidal gold nanorods: from reduction to growth

    NASA Astrophysics Data System (ADS)

    Park, Kyoungweon; El-Sayed, Mostafa; Srinivasarao, Mohan

    2005-03-01

    Formation of gold nanorods(NRs) in controlled reduction condition was investigated. Gold NRs were synthesized by seed mediated method where pre-made gold nanospheres were added to a growth solution containing surfactants, reducing agent and compound of gold ion and surfactant. Reduction mechanism was manipulated by changing catalytic activity of seed. Seed of different size and capping agent coverage led to different dispersity of NRs since seed plays a role as catalyst as well as nucleation site. The difference between the redox potentials of gold species and reducing agent(δE) was controlled by the strength of reducing agent and the stability of the gold compound. As δE leading to changing the morphology of resulting gold NRs. The surface of gold NRs with a series of aspect ratio was functionalized by thiolated beta cyclodextrin which binds preferentially to the end of NRs and promotes the orientation of rod-rod pair even without host-guest interaction.

  11. Gold nanorods as contrast agents for biological imaging: optical properties, surface conjugation, and photothermal effects†

    PubMed Central

    Tong, Ling; Wei, Qingshan; Wei, Alexander; Cheng, Ji-Xin

    2009-01-01

    Gold nanorods (NRs) have plasmon-resonant absorption and scattering in the near-infrared (NIR) region, making them attractive probes for in vitro and in vivo imaging. In the cellular environment, NRs can provide scattering contrast for darkfield microscopy, or emit a strong two-photon luminescence (TPL) due to plasmon-enhanced two-photon absorption. NRs have also been employed in biomedical imaging modalities such as optical coherence tomography (OCT) or photoacoustic tomography (PAT). Careful control over surface chemistry enhances the capacity of NRs as biological imaging agents by enabling cell-specific targeting, and by increasing their dispersion stability and circulation lifetimes. NRs can also efficiently convert optical energy into heat, and inflict localized damage to tumor cells. Laser-induced heating of NRs can disrupt cell membrane integrity and homeostasis, resulting in Ca2+ influx and the depolymerization of the intracellular actin network. The combination of plasmon-resonant optical properties, intense local photothermal effects, and robust surface chemistry render gold NRs as promising theragnostic agents. PMID:19161395

  12. Enhancing surface plasmon detection using template-stripped gold nanoslit arrays on plastic films.

    PubMed

    Lee, Kuang-Li; Chen, Pei-Wen; Wu, Shu-Han; Huang, Jhih-Bin; Yang, Sen-Yeu; Wei, Pei-Kuen

    2012-04-24

    Nanostructure-based sensors are capable of sensitive and label-free detection for biomedical applications. However, high-throughput and low-cost fabrication techniques are the main issues which should be addressed. In this study, chip-based nanostructures for intensity-sensitive detection were fabricated and tested using a thermal-annealing-assisted template-stripping method. Large-area uniform nanoslit arrays with a 500 nm period and various slit widths, from 30 to 165 nm, were made on plastic films. A transverse magnetic-polarized wave in these gold nanostructures generated sharp and asymmetric Fano resonances in transmission spectra. The full width at half-maximum bandwidth decreased with the decrease of the slit width. The narrowest bandwidth was smaller than 10 nm. Compared to nanoslit arrays on glass substrates using electron-beam lithography, the proposed chip has a higher intensity sensitivity up to 10367%/RIU (refractive index unit) and reaches a figure of merit up to 55. The higher intensity sensitivity for the template-stripped nanostructure is attributed to a smoother gold surface and larger grain sizes on the plastic film, which reduces the surface plasmon propagation loss.

  13. Setup for investigating gold nanoparticle penetration through reconstructed skin and comparison to published human skin data.

    PubMed

    Labouta, Hagar I; Thude, Sibylle; Schneider, Marc

    2013-06-01

    Owing to the limited source of human skin (HS) and the ethical restrictions of using animals in experiments, in vitro skin equivalents are a possible alternative for conducting particle penetration experiments. The conditions for conducting penetration experiments with model particles, 15-nm gold nanoparticles (AuNP), through nonsealed skin equivalents are described for the first time. These conditions include experimental setup, sterility conditions, effective applied dose determination, skin sectioning, and skin integrity check. Penetration at different exposure times (two and 24 h) and after tissue fixation (fixed versus unfixed skin) are examined to establish a benchmark in comparison to HS in an attempt to get similar results to HS experiments presented earlier. Multiphoton microscopy is used to detect gold luminescence in skin sections. λ(ex)=800 nm is used for excitation of AuNP and skin samples, allowing us to determine a relative index for particle penetration. Despite the observed overpredictability of penetration into skin equivalents, they could serve as a first fast screen for testing the behavior of nanoparticles and extrapolate their penetration behavior into HS. Further investigations are required to test a wide range of particles of different physicochemical properties to validate the skin equivalent-human skin particle penetration relationship.

  14. Mechanistic investigations and molecular medicine applications of gold nanoparticle mediated (GNOME) laser transfection

    NASA Astrophysics Data System (ADS)

    Schomaker, M.; Heinemann, D.; Kalies, S.; Willenbrock, S.; Murua Escobar, H.; Buch, A.; Sodeik, B.; Ripken, T.; Meyer, H.

    2014-03-01

    Alternative high throughput transfection methods are required to understand the molecular network of the cell, which is linked to the evaluation of target genes as therapeutic agents. Besides diagnostic purposes, the transfection of primary- and stem cells is of high interest for therapeutic use. Here, the cell release of trans- or exogene proteins is used to develop immune cancer therapies. The basic requirement to accomplish manipulation of cells is an efficient and gentle transfection method. Therefore, we developed an automatized cell manipulation platform providing high throughput by using GNOME laser transfection. Herein, the interaction of moderately focused laser pulses with gold nanoparticles in close vicinity to the cell membrane mediate transient membrane permeabilization. The exact nature of the involved permeabilization effects depends on the applied particles and laser parameters. Hereinafter, we describe investigations considering the parameter regime, the permeabilization mechanism and the safety profile of GNOME laser transfection. The experimental and calculated results imply a combined permeabilization mechanism consisting of both photochemical and photothermal effects. Furthermore, paramount spatial control achieved either by laser illumination with micrometer precision or targeted gold nanoparticle binding to the cells was demonstrated, allowing selective cell manipulation and destruction. Additionally, the possibility to manipulate difficult to transfect primary cells (neurons) is shown. These results give insights in the basic mechanisms involved in GNOME laser transfection and serve as a strong basis to deliver different molecules for therapeutic (e.g. proteins) and diagnostic (siRNA) use.

  15. Setup for investigating gold nanoparticle penetration through reconstructed skin and comparison to published human skin data

    NASA Astrophysics Data System (ADS)

    Labouta, Hagar I.; Thude, Sibylle; Schneider, Marc

    2013-06-01

    Owing to the limited source of human skin (HS) and the ethical restrictions of using animals in experiments, in vitro skin equivalents are a possible alternative for conducting particle penetration experiments. The conditions for conducting penetration experiments with model particles, 15-nm gold nanoparticles (AuNP), through nonsealed skin equivalents are described for the first time. These conditions include experimental setup, sterility conditions, effective applied dose determination, skin sectioning, and skin integrity check. Penetration at different exposure times (two and 24 h) and after tissue fixation (fixed versus unfixed skin) are examined to establish a benchmark in comparison to HS in an attempt to get similar results to HS experiments presented earlier. Multiphoton microscopy is used to detect gold luminescence in skin sections. λex=800 nm is used for excitation of AuNP and skin samples, allowing us to determine a relative index for particle penetration. Despite the observed overpredictability of penetration into skin equivalents, they could serve as a first fast screen for testing the behavior of nanoparticles and extrapolate their penetration behavior into HS. Further investigations are required to test a wide range of particles of different physicochemical properties to validate the skin equivalent-human skin particle penetration relationship.

  16. Nanoporous gold obtained from a metallic glass precursor used as substrate for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Scaglione, F.; Paschalidou, E. M.; Rizzi, P.; Bordiga, S.; Battezzati, L.

    2015-09-01

    Nanoporous gold (NPG) has been synthesized by electrochemical de-alloying a new precursor, amorphous Au30Cu38Ag7Pd5Si20 (at.%), starting from melt-spun ribbons. Ligaments ranging from 75 to 210 nm depending on the de-alloying time were obtained. Analytical and electrochemical evidence showed the ligaments contain residual Cu, Ag and Pd. Surface-enhanced Raman scattering from the NPG was investigated using pyridine and 4,4‧-bi-pyridine as probe molecules. It was found that the activity is at maximum when the ribbon is fully de-alloyed although the ligaments then have a larger size. The enhancement is attributed to the small size of crystals in the ligaments, to their morphology and to trapped atoms.

  17. Silica-coated gold nanostars for surface-enhanced resonance Raman spectroscopy mapping of integrins in breast cancer cells

    NASA Astrophysics Data System (ADS)

    Fenn, Michael B.; Roki, Nikša.; Bashur, Chris

    2015-03-01

    Surface-Enhanced Resonance Raman Spectroscopy (SERRS) has great potential for improving cancer research and diagnosis. Capable of sub-femtomolar detection, and a high degree of multiplexing, SERRS is an attractive new technique for studying cancer biology. We have developed PEGylated silica-coated gold nanostars that can be tuned to match the Raman laser-light source wavelength, providing high-level SERRS/SERS enhancement when combined with various reporter molecules. Furthermore, the particles were conjugated with cyclo-RGDf/k peptide to investigate integrin expression of breast cancer cells using high-speed Raman mapping. We propose that this may provide a better understanding of the role of integrins in breast cancer invasiveness.

  18. Enhancing on-surface mismatch discrimination capability of PNA probes by AuNP modification of gold(111) surface.

    PubMed

    Ghosh, Srabani; Mishra, Sourav; Mukhopadhyay, Rupa

    2013-09-24

    Unambiguous identification of single base mismatches in nucleic acid sequences is of great importance in nucleic acid detection assays. However, ambiguities are often encountered with, and therefore, a strategy for attaining substantially large enhancement of mismatch discrimination has been worked upon in this study. Short single-stranded peptide nucleic acid (PNA) and deoxyribonucleic acid (DNA) sensor probes that are immobilized onto gold nanoparticle (AuNP) modified Au(111) surface have been applied for target DNA detection. It will be shown that while both PNA and the analogous DNA probes exhibit generally better target detection abilities on the AuNP-modified Au(111) surface (elicited from fluorescence-based measurement of on-surface Tm values), compared to the bare Au(111) surface, PNA supersedes DNA, for all sizes of AuNPs (10, 50, and 90 nm) applied, with the difference being quite drastic in the case of the smallest 10 nm AuNP. It is found that while the AuNP curvature plays a pivotal role in target detection abilities of the PNA probes, the changes in the surface roughness caused by AuNP treatment do not exert any significant influence. This study also presents a means for preparing PNA-AuNP hybrids without altering PNA functionality and without AuNP aggregation by working with the surface-affixed AuNPs.

  19. Enhanced Broadband Electromagnetic Absorption in Silicon Film with Photonic Crystal Surface and Random Gold Grooves Reflector

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Hui; Qiao, Na; Yang, Yibiao; Ye, Han; Liu, Shaoding; Wang, Wenjie; Wang, Yuncai

    2015-08-01

    We show a hybrid structure consisting of Si film with photonic crystal surface and random triangular gold grooves reflector at the bottom, which is capable of realizing efficient, broad-band, wide-angle optical absorption. It is numerically demonstrated that the enhanced absorption in a broad wavelength range (0.3-9.9 μm) due to the scattering effect of both sides of the structure and the created resonance modes. Larger thickness and period are favored to enhance the absorption in broader wavelength range. Substantial electric field concentrates in the grooves of surface photonic crystal and in the Si film. Our structure is versatile for solar cells, broadband photodetection and stealth coating.

  20. Boron Nitride Nanosheet-Veiled Gold Nanoparticles for Surface-Enhanced Raman Scattering.

    PubMed

    Cai, Qiran; Mateti, Srikanth; Watanabe, Kenji; Taniguchi, Takashi; Huang, Shaoming; Chen, Ying; Li, Lu Hua

    2016-06-22

    Atomically thin boron nitride (BN) nanosheets have many properties desirable for surface-enhanced Raman spectroscopy (SERS). BN nanosheets have a strong surface adsorption capability toward airborne hydrocarbon and aromatic molecules. For maximized adsorption area and hence SERS sensitivity, atomically thin BN nanosheet-covered gold nanoparticles have been prepared for the first time. When placed on top of metal nanoparticles, atomically thin BN nanosheets closely follow their contours so that the plasmonic hot spots are retained. Electrically insulating BN nanosheets also act as a barrier layer to eliminate metal-induced disturbances in SERS. Moreover, the SERS substrates veiled by BN nanosheets show an outstanding reusability in the long term. As a result, the sensitivity, reproducibility, and reusability of SERS substrates can be greatly improved. We also demonstrate that large BN nanosheets produced by chemical vapor deposition can be used to scale up the proposed SERS substrate for practical applications. PMID:27254250

  1. Glutathione-Coated Luminescent Gold Nanoparticles: A Surface Ligand for Minimizing Serum Protein Adsorption

    PubMed Central

    2015-01-01

    Ultrasmall glutathione-coated luminescent gold nanoparticles (GS-AuNPs) are known for their high resistance to serum protein adsorption. Our studies show that these NPs can serve as surface ligands to significantly enhance the physiological stability and lower the serum protein adsorption of superparamagnetic iron oxide nanoparticles (SPIONs), in addition to rendering the NPs the luminescence property. After the incorporation of GS-AuNPs onto the surface of SPIONs to form the hybrid nanoparticles (HBNPs), these SPIONs’ protein adsorption was about 10-fold lower than those of the pure glutathione-coated SPIONs suggesting that GS-AuNPs are capable of providing a stealth effect against serum proteins. PMID:25029478

  2. Enhanced Broadband Electromagnetic Absorption in Silicon Film with Photonic Crystal Surface and Random Gold Grooves Reflector

    PubMed Central

    Chen, Zhi-Hui; Qiao, Na; Yang, Yibiao; Ye, Han; Liu, Shaoding; Wang, Wenjie; Wang, Yuncai

    2015-01-01

    We show a hybrid structure consisting of Si film with photonic crystal surface and random triangular gold grooves reflector at the bottom, which is capable of realizing efficient, broad-band, wide-angle optical absorption. It is numerically demonstrated that the enhanced absorption in a broad wavelength range (0.3–9.9 μm) due to the scattering effect of both sides of the structure and the created resonance modes. Larger thickness and period are favored to enhance the absorption in broader wavelength range. Substantial electric field concentrates in the grooves of surface photonic crystal and in the Si film. Our structure is versatile for solar cells, broadband photodetection and stealth coating. PMID:26238270

  3. Enhanced Broadband Electromagnetic Absorption in Silicon Film with Photonic Crystal Surface and Random Gold Grooves Reflector.

    PubMed

    Chen, Zhi-Hui; Qiao, Na; Yang, Yibiao; Ye, Han; Liu, Shaoding; Wang, Wenjie; Wang, Yuncai

    2015-01-01

    We show a hybrid structure consisting of Si film with photonic crystal surface and random triangular gold grooves reflector at the bottom, which is capable of realizing efficient, broad-band, wide-angle optical absorption. It is numerically demonstrated that the enhanced absorption in a broad wavelength range (0.3-9.9 μm) due to the scattering effect of both sides of the structure and the created resonance modes. Larger thickness and period are favored to enhance the absorption in broader wavelength range. Substantial electric field concentrates in the grooves of surface photonic crystal and in the Si film. Our structure is versatile for solar cells, broadband photodetection and stealth coating. PMID:26238270

  4. Glutathione-coated luminescent gold nanoparticles: a surface ligand for minimizing serum protein adsorption.

    PubMed

    Vinluan, Rodrigo D; Liu, Jinbin; Zhou, Chen; Yu, Mengxiao; Yang, Shengyang; Kumar, Amit; Sun, Shasha; Dean, Andrew; Sun, Xiankai; Zheng, Jie

    2014-08-13

    Ultrasmall glutathione-coated luminescent gold nanoparticles (GS-AuNPs) are known for their high resistance to serum protein adsorption. Our studies show that these NPs can serve as surface ligands to significantly enhance the physiological stability and lower the serum protein adsorption of superparamagnetic iron oxide nanoparticles (SPIONs), in addition to rendering the NPs the luminescence property. After the incorporation of GS-AuNPs onto the surface of SPIONs to form the hybrid nanoparticles (HBNPs), these SPIONs' protein adsorption was about 10-fold lower than those of the pure glutathione-coated SPIONs suggesting that GS-AuNPs are capable of providing a stealth effect against serum proteins. PMID:25029478

  5. Adsorbate dynamics on a silica-coated gold surface measured by Rydberg Stark spectroscopy

    NASA Astrophysics Data System (ADS)

    Naber, J.; Machluf, S.; Torralbo-Campo, L.; Soudijn, M. L.; van Druten, N. J.; van Linden van den Heuvell, H. B.; Spreeuw, R. J. C.

    2016-05-01

    Trapping a Rydberg atom close to a surface is an important step towards the realisation of many proposals for quantum information processing or hybrid quantum systems. One of the challenges in these experiments is posed by the electric field emanating from contaminations on the surface. Here we report on measurements of an electric field created by 87Rb atoms adsorbed on a 25 nm thick layer of SiO2, covering a 90 nm layer of Au. The electric field is measured using a two-photon transition to the 23{D}5/2 and 25{S}1/2 states. The electric field value that we measure is higher than typical values measured above metal surfaces, but is consistent with a recent measurement above a SiO2 surface. In addition, we measure the temporal behaviour of the field and observe that we can reduce it in a single experimental cycle, using ultraviolet light or by mildly locally heating the surface with one of the excitation lasers, whereas the buildup of the field takes thousands of cycles. We explain these results by a change in the adatom distribution on the surface. These results indicate that, while the stray electric field can be reduced, achieving field-free conditions above a silica-coated gold chip remains challenging.

  6. Modified titanium surface with gelatin nano gold composite increases osteoblast cell biocompatibility

    NASA Astrophysics Data System (ADS)

    Lee, Young-Hee; Bhattarai, Govinda; Aryal, Santosh; Lee, Nan-Hee; Lee, Min-Ho; Kim, Tae-Gun; Jhee, Eun-Chung; Kim, Hak-Yong; Yi, Ho-Keun

    2010-08-01

    This study examined the gelatin nano gold (GnG) composite for surface modification of titanium in addition to insure biocompatibility on dental implants or biomaterials. The GnG composite was constructed by gelatin and hydrogen tetrachloroaurate in presence of reducing agent, sodium borohydrate (NabH 4). The GnG composite was confirmed by UV-VIS spectroscopy and transmission electron microscopy (TEM). A dipping method was used to modify the titanium surface by GnG composite. Surface was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The MC-3T3 E1 cell viability was assessed by trypan blue and the expression of proteins to biocompatibility were analyzed by Western blotting. The GnG composite showed well dispersed character, the strong absorption at 530 nm, roughness, regular crystal and clear C, Na, Cl, P, and Au signals onto titanium. Further, this composite allowed MC-3T3 E1 growth and viability compared to gelatin and pure titanium. It induced ERK activation and the expression of cell adherent molecules, FAK and SPARC, and growth factor, VEGF. However, GnG decreased the level of SAPK/JNK. This shows that GnG composite coated titanium surfaces have a good biocompatibility for osteoblast growth and attachment than in intact by simple and versatile dipping method. Furthermore, it offers good communication between cell and implant surfaces by regulating cell signaling and adherent molecules, which are useful to enhance the biocompatibility of titanium surfaces.

  7. Electrochemical and Numerical Studies of Surface, Grain-Boundary and Bulk Copper Diffusion Into Gold

    NASA Astrophysics Data System (ADS)

    Miller, Eric Todd

    Surface, grain-boundary, and bulk chemical diffusivities of copper into gold were measured by chronoamperometry -potentiometry applied to Cu|CuCl |Au solid state galvanic cells at 300-400^circC. The cells were constructed using a novel vapor deposition technique which is described. The automated data acquisition techniques utilizing unique hardware and custom designed software are also presented. Chronoamperometry and a two electrode limited potential cyclic voltammetry technique were comparatively used to determine cell capacitance and resistance. Both gave similar RC values at lower temperatures but diverged from each other at higher temperatures. Electron hole conductivity of CuCl could not be determined from intercept values in the chronoamperometry Cottrell analysis. The partial molar enthalpy and entropy of mixing copper into gold were determined from Emf vs temperature vs composition measurements of Cu|CuCl |Au-Cu alloy cells. The results support the regular solution model of mixing with interaction energy parameter {bf{cal Q}} = 10kJ. Diffusion coefficients were calculated from the chronoamperometry-potentiometry time/flux/concentration data in two ways: via the Cottrell equation, for an average diffusion coefficient; and via a simplex and finite difference program for the simultaneous determination of surface, grain-boundary, and bulk diffusion coefficients. This program was run on a MASPAR MP-2 massively parallel computer. The surface and grain-boundary diffusivities were numerically determinable in single and polycrystalline cathodes at short diffusion times. Bulk diffusivity was determinable at short and long diffusion times and agreed with previous data. Surface diffusivity was two orders of magnitude larger than the bulk with lower activation energy. Grain -boundary diffusivity was one order of magnitude larger than the bulk with similar activation energy. The Cottrell equation was only valid at very long diffusion times due to the transient interface

  8. Surface-plasmon-based colorimetric detection of Cu(II) ions using label-free gold nanoparticles in aqueous thiosulfate systems

    NASA Astrophysics Data System (ADS)

    Tripathy, Suraj Kumar; Woo, Ju Yeon; Han, Chang-Soo

    2012-08-01

    We report colorimetric, label-free and non-aggregation-based gold nanoparticle (AuNP) probes for the highly selective detection of Cu(II) ions in aqueous environments. This detection scheme relies on the ability of Cu(II) ions to catalyze the leaching of gold at room temperature in the presence of thiosulfate species and ammonia. This simple and cost-effective probe provides rapid detection of Cu(II) ions at concentrations as low as 10 ppm. A similar detection method using AuNPs in ammonia-free thiosulfate solution is also viable at moderate reaction temperature (50 °C). The ammonia-free method also leads to marked damping and red-shifting of the surface plasmon resonance signal of the AuNP dispersion. The two methods clearly differ in the nature of the surface plasmon damping phenomenon, and their working mechanisms are plausibly explained based on the experimental investigations.

  9. Surface observation for seed-mediated growth attachment of gold nanoparticles on a glassy carbon substrate.

    PubMed

    Oyama, Munetaka; Yamaguchi, Shin-Ya; Zhang, Jingdong

    2009-02-01

    A seed-mediated growth method for surface modification was applied to the attachment of gold nanoparticles (AuNPs) to glassy carbon (GC) surfaces. By simply immersing a GC plate at first into a seed solution containing 4 nm Au nano-seed particles and then into a growth solution containing HAuCl(4), ascorbic acid and cetyltrimethyammonium bromide, AuNPs could be successfully attached to the GC surface via the growth of nanoparticles. A possible control of the size and density of AuNPs on GC was examined by observing surface images with a field-emission scanning electron microscope (FE-SEM) after several preparations with different immersion times. Compared with previous results on the growth of AuNPs on indium tin oxide (ITO) surfaces, it was characteristic that the AuNPs attached to GC surfaces exhibited smaller size and higher density as well as a flatter and non-crystal-like morphology. In addition, for performing the dense attachment of regular nano-sized AuNPs on GC surfaces, immersion for 2 h into the growth solution was sufficient. Longer immersion for 24 h caused an irregular growth of bold Au micro-crystals, while 24 h was necessary in the case of AuNPs on ITO surfaces. Shorter seeding and growth times were found to be effective for a sparse attachment of smaller Au nanoparticles whose size was ca. 20 nm. It was clarified that the seed-mediated growth method for surface modification was valid for fabricating a nanointerface composed of AuNPs on GC surfaces.

  10. Development of a localized surface plasmon resonance-based gold nanobiosensor for the determination of prolactin hormone in human serum.

    PubMed

    Faridli, Zahra; Mahani, Mohamad; Torkzadeh-Mahani, Masoud; Fasihi, Javad

    2016-02-15

    A localized surface plasmon resonance immunoassay has been developed to determine prolactin hormone in human serum samples. Gold nanoparticles were synthesized, and the probe was prepared by electrostatic adsorption of antibody on the surfaces of gold nanoparticles. The pH and the antibody-to-gold nanoparticle ratio, as the factors affecting the probe functions, were optimized. The constructed nanobiosensor was characterized by dynamic light scattering. The sensor was applied for the determination of prolactin antigen concentration based on the amount of localized surface plasmon resonance peak shift. A linear dynamic range of 1-40 ng ml(-1), a detection limit of 0.8 ng ml(-1), and sensitivity of 10 pg ml(-1) were obtained. Finally, the nanobiosensor was applied for the determination of prolactin in human control serum sample.

  11. Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt3M (where M = 3d transition metals) alloy catalyst from first-principles

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius; Ham, Hyung Chul

    2015-01-01

    The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt3M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt3M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt3M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt3M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

  12. Effect of gold subsurface layer on the surface activity and segregation in Pt/Au/Pt{sub 3}M (where M = 3d transition metals) alloy catalyst from first-principles

    SciTech Connect

    Kim, Chang-Eun; Lim, Dong-Hee; Jang, Jong Hyun; Kim, Hyoung Juhn; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Hong, Seong-Ahn; Soon, Aloysius E-mail: hchahm@kist.re.kr; Ham, Hyung Chul E-mail: hchahm@kist.re.kr

    2015-01-21

    The effect of a subsurface hetero layer (thin gold) on the activity and stability of Pt skin surface in Pt{sub 3}M system (M = 3d transition metals) is investigated using the spin-polarized density functional theory calculation. First, we find that the heterometallic interaction between the Pt skin surface and the gold subsurface in Pt/Au/Pt{sub 3}M system can significantly modify the electronic structure of the Pt skin surface. In particular, the local density of states projected onto the d states of Pt skin surface near the Fermi level is drastically decreased compared to the Pt/Pt/Pt{sub 3}M case, leading to the reduction of the oxygen binding strength of the Pt skin surface. This modification is related to the increase of surface charge polarization of outmost Pt skin atoms by the electron transfer from the gold subsurface atoms. Furthermore, a subsurface gold layer is found to cast the energetic barrier to the segregation loss of metal atoms from the bulk (inside) region, which can enhance the durability of Pt{sub 3}M based catalytic system in oxygen reduction condition at fuel cell devices. This study highlights that a gold subsurface hetero layer can provide an additional mean to tune the surface activity toward oxygen species and in turn the oxygen reduction reaction, where the utilization of geometric strain already reaches its practical limit.

  13. Investigating the surface chemistry of Mars

    SciTech Connect

    Grunthaner, F.J.; Ricco, A.J.; Butler, A.M.; Lane, A.L.; McKay, C.P.; Zent, A.P.; Quinn, R.C.; Murray, B.; Klein, H.P.; Levin, G.V.; Terhune, R.W.; Homer, M.L.; Ksendzov, A.; Niedermann, P.

    1995-10-01

    One of the primary objectives of the Viking missions to Mars in the 1970s was to search for life. Numerous theories were put forth to explain the Viking data, most of which involved an oxidizing species in the Martian surface material. In December 1992, the Mars Oxidant Experiment (MOx) was selected as the U.S. contribution to the Russian Mars 96 mission. Two landers are scheduled for launch in November 1996 and should arrive at Mars in September 1997. The MOx instrument on the Russian lander is designed to investigate the chemical nature of the Martian surface material, with particular emphasis on its oxidative character. The instrument uses fiber-optic technology to monitor real-time physicochemical changes in a suite of chemically sensitive thin-film materials. This report describes the scientific rationale and basis for the MOx instrument, along with the details of its design and construction. 15 refs., 4 figs., 1 tab.

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

    PubMed

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

    2015-01-28

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

  15. Templating gold surfaces with function: a self-assembled dendritic monolayer methodology based on monodisperse polyester scaffolds.

    PubMed

    Öberg, Kim; Ropponen, Jarmo; Kelly, Jonathan; Löwenhielm, Peter; Berglin, Mattias; Malkoch, Michael

    2013-01-01

    The antibiotic resistance developed among several pathogenic bacterial strains has spurred interest in understanding bacterial adhesion down to a molecular level. Consequently, analytical methods that rely on bioactive and multivalent sensor surfaces are sought to detect and suppress infections. To deliver functional sensor surfaces with an optimized degree of molecular packaging, we explore a library of compact and monodisperse dendritic scaffolds based on the nontoxic 2,2-bis(methylol)propionic acid (bis-MPA). A self-assembled dendritic monolayer (SADM) methodology to gold surfaces capitalizes on the design of aqueous soluble dendritic structures that bear sulfur-containing core functionalities. The nature of sulfur (either disulfide or thiol), the size of the dendritic framework (generation 1-3), the distance between the sulfur and the dendritic wedge (4 or 14 Å), and the type of functional end group (hydroxyl or mannose) were key structural elements that were identified to affect the packaging densities assembled on the surfaces. Both surface plasmon resonance (SPR) and resonance-enhanced surface impedance (RESI) experiments revealed rapid formation of homogenously covered SADMs on gold surfaces. The array of dendritic structures enabled the fabrication of functional gold surfaces displaying molecular covering densities of 0.33-2.2 molecules·nm(-2) and functional availability of 0.95-5.5 groups·nm(-2). The cell scavenging ability of these sensor surfaces for Escherichia coli MS7fim+ bacteria revealed 2.5 times enhanced recognition for G3-mannosylated surfaces when compared to G3-hydroxylated SADM surfaces. This promising methodology delivers functional gold sensor surfaces and represents a facile route for probing surface interactions between multivalently presented motifs and cells in a controlled surface setting.

  16. Strong coupling of surface plasmon resonances to molecules on a gold grating

    NASA Astrophysics Data System (ADS)

    Gupta, Prince; Ramakrishna, S. Anantha; Wanare, Harshawardhan

    2016-10-01

    The intense electromagnetic fields generated by a surface plasmon resonance can strongly couple to molecules in the vicinity of the surface, causing significant line shifts. By measuring the angle dependent transmission spectrum through gold gratings with Rhodamine-6G molecules deposited on them, the coupling of the surface plasmon resonance to the molecular levels at different frequencies was determined. The strong coupling within the absorption and fluorescence bands of the molecules leads to anti-crossing of the states of the coupled system evidenced by the transmission minima. In particular, simultaneous existence of two distinct resonances at different wavevectors for a given wavelength over the absorption and fluorescence bands is observed. The multiplicity of the molecular levels and the coupling fields involved in the process is captured in a three-level Λ-system model coherently driven by the enhanced surface plasmon fields. The enhanced surface plasmon fields and the resonant absorption/fluorescent fields form the two arms of the Λ-system with approriate detuning.

  17. The Janus-SAM approach for the flexible functionalization of gold and titanium oxide surfaces.

    PubMed

    Bhat, Rahila; Sell, Stephan; Wagner, Ralf; Zhang, Jian Tao; Pan, Changjiang; Garipcan, Bora; Boland, Wilhelm; Bossert, Jörg; Klemm, Elisabeth; Jandt, Klaus D

    2010-02-01

    A novel approach is developed to address the requirement of multiple stamps and inks for microcontact printing (microCP) onto different substrate surfaces. This approach relies on microCP one divalent molecule, which is able to form Janus self-assembled monolayers (JSAMs) with a labile cleavable centre, thus providing a facile method for the chemical derivatization of different substrate surfaces. This study presents an answer to the challenges presented within a highly versatile application, microCP. N-(3-diethylphosphatoxy)propyl-11-mercaptoundecanamide is used for the first time as an ink for microCP onto both gold and titanium oxide surfaces, utilizing the same polydimethylsiloxane stamp. Following printing, the JSAMs are enzymatically treated on these two different substrates to reveal different functional groups. The newly formed surfaces are subjected to additional surface reactions and used for the chemisorption of bovine serum albumin. At each stage, these JSAMs are characterized by X-ray photoelectron spectroscopy and dynamic water-contact-angle measurements. Confocal laser scanning microscopy is used for the characterization of the adsorbed proteins.

  18. Surface capping and size-dependent toxicity of gold nanoparticles on different trophic levels.

    PubMed

    Iswarya, V; Manivannan, J; De, Arpita; Paul, Subhabrata; Roy, Rajdeep; Johnson, J B; Kundu, Rita; Chandrasekaran, N; Mukherjee, Anita; Mukherjee, Amitava

    2016-03-01

    In the present study, the toxicity of gold nanoparticles (Au NPs) was evaluated on various trophic organisms. Bacteria, algae, cell line, and mice were used as models representing different trophic levels. Two different sizes (CIT30 and CIT40) and surface-capped (CIT30-polyvinyl pyrrolidone (PVP)-capped) Au NPs were selected. CIT30 Au NP aggregated more rapidly than CIT40 Au NP, while an additional capping of PVP (CIT30-PVP capped Au NP) was found to enhance its stability in sterile lake water medium. Interestingly, all the forms of NPs evaluated were stable in the cell culture medium during the exposure period. Size- and dose-dependent cytotoxicities were observed in both bacteria and algae, with a strong dependence on reactive oxygen species (ROS) generation and lactate dehydrogenase (LDH) release. CIT30-PVP capped Au NP showed a significant decrease in toxicity compared to CIT30 Au NP in bacteria and algae. In the SiHa cell line, dose- and exposure-dependent decline in cell viability were noted for all three types of Au NPs. In mice, the induction of DNA damage was size and dose dependent, and surface functionalization with PVP reduced the toxic effects of CIT30 Au NP. The exposure to CIT30, CIT40, and CIT30-PVP capped Au NPs caused an alteration of the oxidative stress-related endpoints in mice hepatocytes. The toxic effects of the gold nanoparticles were found to vary in diverse test systems, accentuating the importance of size and surface functionalization at different trophic levels.

  19. Surface interactions of gold nanorods and polysaccharides: From clusters to individual nanoparticles.

    PubMed

    de Barros, Heloise Ribeiro; Piovan, Leandro; Sassaki, Guilherme L; de Araujo Sabry, Diego; Mattoso, Ney; Nunes, Ábner Magalhães; Meneghetti, Mario R; Riegel-Vidotti, Izabel C

    2016-11-01

    Gold nanorods (AuNRs) are suitable for constructing self-assembled structures for the development of biosensing devices and are usually obtained in the presence of cetyltrimethylammonium bromide (CTAB). Here, a sulfated chitosan (ChiS) and gum arabic (GA) were employed to encapsulate CTAB/AuNRs with the purpose of studying the interactions of the polysaccharides with CTAB, which is cytotoxic and is responsible for the instability of nanoparticles in buffer solutions. The presence of a variety of functional groups such as the sulfate groups in ChiS and the carboxylic groups in GA, led to efficient interactions with CTAB/AuNRs as evidenced through UV-vis and FTIR spectroscopies. Electron microscopies (HR-SEM and TEM) revealed that nanoparticle clusters were formed in the GA-AuNRs sample, whereas individual AuNRs, surrounded by a dense layer of polysaccharides, were observed in the ChiS-AuNRs sample. Therefore, the presented work contributes to the understanding of the driving forces that control the surface interactions of the studied materials, providing useful information in the building-up of gold self-assembled nanostructures. PMID:27516295

  20. Gold nanoparticle incorporated inverse opal photonic crystal capillaries for optofluidic surface enhanced Raman spectroscopy.

    PubMed

    Zhao, Xiangwei; Xue, Jiangyang; Mu, Zhongde; Huang, Yin; Lu, Meng; Gu, Zhongze

    2015-10-15

    Novel transducers are needed for point of care testing (POCT) devices which aim at facile, sensitive and quick acquisition of health related information. Recent advances in optofluidics offer tremendous opportunities for biological/chemical analysis using extremely small sample volumes. This paper demonstrates nanostructured capillary tubes for surface enhanced Raman spectroscopy (SERS) analysis in a flow-through fashion. The capillary tube integrates the SERS sensor and the nanofluidic structure to synergistically offer sample delivery and analysis functions. Inside the capillary tube, inverse opal photonic crystal (IO PhC) was fabricated using the co-assembly approach to form nanoscale liquid pathways. In the nano-voids of the IO PhC, gold nanoparticles were in situ synthesized and functioned as the SERS hotspots. The advantages of the flow-through SERS sensor are multifold. The capillary effect facilities the sample delivery process, the nanofluidic channels boosts the interaction of analyte and gold nanoparticles, and the PhC structure strengthens the optical field near the SERS hotspots and results in enhanced SERS signals from analytes. As an exemplary demonstration, the sensor was used to measure creatinein spiked in artificial urine samples with detection limit of 0.9 mg/dL. PMID:25988995

  1. Electrical characterization of gold and platinum thin film electrodes with polyaniline modified surfaces

    NASA Astrophysics Data System (ADS)

    Aggas, John Richard

    Recent studies into soft organic electronics have burgeoned as a result of discoveries of conducting polymers such as polyaniline, polythiophene, and polypyrrole. However, in order to make these conducting polymers suitable for in vivo soft organic electronics, they must be developed so that they can be biocompatible and provide accurate sensing. Chitosan, a naturally occurring polymer structure found in exoskeletons of crustaceans, has been studied for its biocompatible properties. Composites of polyaniline (PAn), an intrinsically conductive polymer (ICP) and chitosan (Chi), a biopolymer, were developed and applied to gold and platinum Thin Film Electrode (TFE) devices. Electropolymerization and drop cast deposition were utilized to modify TFEs with a thin film of PAn or PAn-Chi composite. The impedance response over a spectrum of frequencies was studied for blank control TFEs, platinized TFEs, and platinized TFEs with various polyaniline coatings. Impedance measurements were taken in dry environments, DI Water, and in buffers such as PBS, and HEPES. Current-Voltage (I-V) characterization was used to study the current response and SEM imaging was used to study the surface topography. Resistance was measured for PAn modified unplatinized gold TFEs with varying amounts of incorporated chitosan. Impedance measurements of control and platinized TFEs yielded results similar to a low pass filter. Due to the conductive nature of polyaniline, the impedance of TFEs decreased substantially after poylaniline deposition. Measured resistance values for polyaniline and chitosan composites on TFEs revealed a window of concentrations of incorporated chitosan to lower resistance.

  2. Gold nanoparticle incorporated inverse opal photonic crystal capillaries for optofluidic surface enhanced Raman spectroscopy.

    PubMed

    Zhao, Xiangwei; Xue, Jiangyang; Mu, Zhongde; Huang, Yin; Lu, Meng; Gu, Zhongze

    2015-10-15

    Novel transducers are needed for point of care testing (POCT) devices which aim at facile, sensitive and quick acquisition of health related information. Recent advances in optofluidics offer tremendous opportunities for biological/chemical analysis using extremely small sample volumes. This paper demonstrates nanostructured capillary tubes for surface enhanced Raman spectroscopy (SERS) analysis in a flow-through fashion. The capillary tube integrates the SERS sensor and the nanofluidic structure to synergistically offer sample delivery and analysis functions. Inside the capillary tube, inverse opal photonic crystal (IO PhC) was fabricated using the co-assembly approach to form nanoscale liquid pathways. In the nano-voids of the IO PhC, gold nanoparticles were in situ synthesized and functioned as the SERS hotspots. The advantages of the flow-through SERS sensor are multifold. The capillary effect facilities the sample delivery process, the nanofluidic channels boosts the interaction of analyte and gold nanoparticles, and the PhC structure strengthens the optical field near the SERS hotspots and results in enhanced SERS signals from analytes. As an exemplary demonstration, the sensor was used to measure creatinein spiked in artificial urine samples with detection limit of 0.9 mg/dL.

  3. High specific surface gold electrode on polystyrene substrate: Characterization and application as DNA biosensor.

    PubMed

    Yang, Zhiliu; Liu, Yichen; Lu, Wei; Yuan, Qingpan; Wang, Wei; Pu, Qiaosheng; Yao, Bo

    2016-05-15

    In the past decades, many efforts have been made to improve the sensitivity and specificity of electrochemical DNA biosensors. However, it is still strongly required to develop disposable and reliable DNA biosensors for wide and practical application. In this article, we reported superior electrochemical properties of an integrated plastic-gold electrode (PGE) fabricated in-house by chemical plating on polystyrene substrate. PGEs were found having extremely high capacity of DNA immobilization compared with gold electrodes fabricated by standard sputtering based photolithography. Unique nano-structured surface was observed on PGEs through morphology techniques, which would to some extend give an explanation to higher capacity of DNA immobilization on PGEs. A probable mechanism of carboxylic acid produced on polystyrene substrate after exposure to UV irradiation was proposed and discussed for the first time. This biosensor was applied to detection and manipulate of DNA hybridization. Detection limit of 7.2×10(-11) M and 1-500 nM of linearity range was obtained.

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

    DOE PAGESBeta

    Jubb, A. M.; Jiao, Y.; Eres, Gyula; Retterer, Scott T.; Gu, Baohua

    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 109 for adsorbed p-mercaptoaniline molecules.« less

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

    PubMed

    Jubb, A M; Jiao, Y; Eres, G; Retterer, S T; Gu, B

    2016-03-14

    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 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 are 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. PMID:26893035

  6. High resolution fiber optic surface plasmon resonance sensors with single-sided gold coatings.

    PubMed

    Feng, Dingyi; Zhou, Wenjun; Qiao, Xueguang; Albert, Jacques

    2016-07-25

    The surface plasmon resonance (SPR) performance of gold coated tilted fiber Bragg gratings (TFBG) at near infrared wavelengths is evaluated as a function of the angle between the tilt plane orientation and the direction of single- and double-sided, nominally 50 nm-thick gold metal depositions. Scanning electron microscope images show that the coating are highly non-uniform around the fiber circumference, varying between near zero and 50 nm. In spite of these variations, the experimental results show that the spectral signature of the TFBG-SPR sensors is similar to that of simulations based on perfectly uniform coatings, provided that the depositions are suitably oriented along the tilt plane direction. Furthermore, it is shown that even a (properly oriented) single-sided coating (over only half of the fiber circumference) is sufficient to provide a theoretically perfect SPR response with a bandwidth under 5 nm, and 90% attenuation. Finally, using a pair of adjacent TFBG resonances within the SPR response envelope, a power detection scheme is used to demonstrate a limit of detection of 3 × 10-6 refractive index units. PMID:27464098

  7. Bone char surface modification by nano-gold coating for elemental mercury vapor removal

    NASA Astrophysics Data System (ADS)

    Assari, Mohamad javad; Rezaee, Abbas; Rangkooy, Hossinali

    2015-07-01

    The present work was done to develop a novel nanocomposite using bone char coated with nano-gold for capture of elemental mercury (Hg0) from air. The morphologies, structures, and chemical constitute of the prepared nanocomposite were evaluated by UV-VIS-NIR, dynamic light-scattering (DLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red (FTIR) spectroscopy, and energy dispersive X-ray spectroscopy (EDS). The capture performance of nanocomposite was evaluated in a needle trap for mercury vapor. An on-line setup based on cold vapor atomic absorption spectrometry (CVAAS) was designed for Hg0 determination. Dynamic capacity of nanocomposite for Hg0 was shown high efficient operating capacity of 586.7 μg/g. As temperature increases, the dynamic adsorption capacity of the nanocomposite was decreased, which are characteristics of physicosorption processes. It was found that the surface modification of bone char with nano-gold has various advantages such as high operating dynamic adsorption capacity and low cost preparation. It was also demonstrated that the developed nanocomposite is suitable for on-line monitoring of Hg0. It could be applied for the laboratory and field studies.

  8. [Ocular surface investigations in dry eye].

    PubMed

    Labbé, A; Brignole-Baudouin, F; Baudouin, C

    2007-01-01

    Dry eye is a complex clinicopathological entity involving tear film, lacrimal glands, eyelids, and a wide spectrum of ocular surface cells, including epithelial, inflammatory, immune, and goblet cells. From the tightly regulated lacrimal film functions and structure, a large variety of investigations have been developed, including tear meniscus measurements, fluorophotometry, meibometry, interference pattern analysis, evaporation rate, tear osmolarity, and thermography. Dry eye conditions also interfere with the ocular surface, causing corneal irregularities that may be explored using the techniques of videokeratography and in vivo confocal microscopy, or optical impairment, as confirmed by aberrometry. At the level of ocular surface cells, impression cytology remains a standard for assessing cell alterations. It has greatly benefited from new confocal microscopy, molecular biology, and flow cytometry techniques. Biological assessment of tear proteins or other mediators is also useful. Major limits should be acknowledged, however, such as technical issues in tear film collection, especially in dry eyes, and the lack of standardization of most measurements. Tear osmolarity, electrophoresis, and dosage of normal tear proteins, such as lysozyme or lactoferrin, remain the most useful tests. Finally, some extraocular explorations such as accessory gland biopsy or serum antinuclear antibody dosage may be useful for assessing the diagnosis of Sjögren's syndrome.

  9. Determination of gold and silver in geological samples by focused infrared digestion: A re-investigation of aqua regia digestion.

    PubMed

    Wang, Yong; Baker, Laura A; Brindle, Ian D

    2016-02-01

    Focused infrared radiation-based digestions, for the determination of gold and silver, can be achieved in a timeframe as short as 10-15 min, making it an attractive candidate technology for the mining industry, where very large numbers of samples are analyzed on a daily basis. An investigation was carried out into gold and silver dissolution chemistry from geological samples using this novel digestion technique. This study investigated in-depth the issue of low recoveries of gold from aqua regia (AR) digestions, reported by a number of researchers. Conventional AR digestions consistently delivered gold recoveries in a range of 69-80% of the certified values for the four certified reference materials (CRM) employed (CCU-1d, SN26, OREAS 62c, and AMiS 0274), while silver recoveries were satisfactory. By gradually shifting the HCl:HNO3 ratio (v/v) from 3:1 to a reversed 1:3 ratio, recoveries of gold and silver exhibited inverse trends. At a HCl:HNO3 ratio of 1:3, complete recovery of gold was achieved with excellent reproducibility in all CRMs. Meanwhile, silver recoveries plunged significantly at this ratio in samples with higher silver concentrations. Silver values were recovered, however, when the silver was re-solubilized by adding a small volume of concentrated HCl to the cooled reverse aqua regia digests. Recoveries of base metals, such as Fe and Cu, were satisfactory throughout and were much less sensitive to changes in the digestion medium. Using four CRMs and five real-world gold/silver containing samples, the utility of the proposed reverse aqua regia was systematically studied. The uncomplicated nature of the digestion methods reported here, that are fast, effective and inexpensive, may be useful to analysts developing/optimizing their methods for the rapid determination of Au and Ag in a variety of mineral phases, particularly where rapid results are desirable, such as in prospecting and mine development. PMID:26653468

  10. Silver and gold nanoparticles produced by pulsed laser ablation in liquid to investigate their interaction with Ubiquitin

    NASA Astrophysics Data System (ADS)

    Dell'Aglio, M.; Mangini, V.; Valenza, G.; De Pascale, O.; De Stradis, A.; Natile, G.; Arnesano, F.; De Giacomo, A.

    2016-06-01

    The interaction of nanoparticles (NPs) with proteins is widely investigated since it can be a key issue in addressing the problem of nanotoxicity, particularly in the case of biological and medical applications. In this work, silver and gold nanoparticles (AgNPs and AuNPs) were produced in water by Pulsed Laser Ablation in Liquid (PLAL) and allowed to react with Ubiquitin (Ub) (a small human protein essential for degradative processes in cells). NPs produced by PLAL are completely free of undesired contaminants and do not require the use of stabilizers. We found that the NPs + Ub system behaves differently if the NPs are or are not treated with a stabilizer before performing the interaction with Ub, since the presence of capping agents modifies the surface reactivity of the metal-NPs. The surface plasmon resonance (SPR) absorption spectroscopy was employed to monitor the fast changes occurring in the NP colloidal solutions upon interaction with Ub. The results obtained by SPR were confirmed by TEM analysis. Therefore, when Ub interacts with bare NPs a rapid aggregation occurs and, at the same time, Ub undergoes an amyloid transition. Notably, the aggregation of AuNPs occurs at a much greater rate than that of analogous AgNPs and the Ub fibrils that are formed can be imaged by thioflavin T fluorescence.

  11. Gold nanoparticle localization at the core surface by using thermosensitive core-shell particles as a template.

    PubMed

    Suzuki, Daisuke; Kawaguchi, Haruma

    2005-12-01

    We report novel thermosensitive hybrid core-shell particles via in situ gold nanoparticle formation using thermosensitive core-shell particles as a template. This method for the in situ synthesis of gold nanoparticles with microgel interiors offers the advantage of eliminating or significantly reducing particle aggregation. In addition, by using thermosensitive microgel structures in which the shell has thermosensitive and gel properties in water--whereas the core itself is a water-insoluble polymer--we were able to synthesize the gold nanoparticles only at the surface of the core, which had reactive sites to bind metal ions. After the gold nanoparticles were synthesized, electroless gold plating was carried out to control the thickness of the gold nanoshells. The dispersions of the obtained hybrid particles were characterized by dynamic light scattering and UV-vis absorption spectroscopy, and the dried particles were also observed by electron microscopy. Adaptation of the technique shown here will create a number of applications as optical, electronic, and biomedical functional materials. PMID:16316147

  12. Relating surface-enhanced Raman scattering signals of cells to gold nanoparticle aggregation as determined by LA-ICP-MS micromapping.

    PubMed

    Büchner, Tina; Drescher, Daniela; Traub, Heike; Schrade, Petra; Bachmann, Sebastian; Jakubowski, Norbert; Kneipp, Janina

    2014-11-01

    The cellular response to nanoparticle exposure is essential in various contexts, especially in nanotoxicity and nanomedicine. Here, 14-nm gold nanoparticles in 3T3 fibroblast cells are investigated in a series of pulse-chase experiments with a 30-min incubation pulse and chase times ranging from 15 min to 48 h. The gold nanoparticles and their aggregates are quantified inside the cellular ultrastructure by laser ablation inductively coupled plasma mass spectrometry micromapping and evaluated regarding the surface-enhanced Raman scattering (SERS) signals. In this way, both information about their localization at the micrometre scale and their molecular nanoenvironment, respectively, is obtained and can be related. Thus, the nanoparticle pathway from endocytotic uptake, intracellular processing, to cell division can be followed. It is shown that the ability of the intracellular nanoparticles and their accumulations and aggregates to support high SERS signals is neither directly related to nanoparticle amount nor to high local nanoparticle densities. The SERS data indicate that aggregate geometry and interparticle distances in the cell must change in the course of endosomal maturation and play a critical role for a specific gold nanoparticle type in order to act as efficient SERS nanoprobe. This finding is supported by TEM images, showing only a minor portion of aggregates that present small interparticle spacing. The SERS spectra obtained after different chase times show a changing composition and/or structure of the biomolecule corona of the gold nanoparticles as a consequence of endosomal processing. PMID:25120183

  13. Antifouling gold surfaces grafted with aspartic acid and glutamic acid based zwitterionic polymer brushes.

    PubMed

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-10-28

    We report two new amino acid based antifouling zwitterionic polymers, poly(N(4)-(2-methacrylamidoethyl)asparagine) (pAspAA) and poly(N(5)-(2-methacrylamidoethyl)glutamine) (pGluAA). The vinyl monomers were developed from aspartic acid and glutamic acid. Surface-initiated photoiniferter-mediated polymerization was employed to graft polymer brushes from gold surfaces. Different thickness of polymer brushes was controlled by varying UV irradiation time. The nonspecific adsorption from undiluted human blood serum and plasma was studied by surface plasmon resonance (SPR). With the polymer film as thin as 11-12 nm, the adsorption on pAspAA from serum and plasma was as low as 0.75 and 5.18 ng/cm(2), respectively, and 1.88 and 10.15 ng/cm(2), respectively, for pGluAA. The adsorption amount is comparable to or even better than other amino acid based zwitterionic polymers such as poly(serine methacrylate), poly(lysine methacrylamide), and poly(ornithine methacrylamide) and other widely used antifouling polymers such as poly(sulfobetaine methacrylate), even under thinner polymer film thickness. The pAspAA and pGluAA grafted surfaces also showed strong resistance to endothelial cell attachment. The possession of both zwitterionic structure and hydrophilic amide groups, biomimetic property, and multifunctionality make pAspAA and pGluAA promising candidates for biocompatible antifouling functionalizable materials. PMID:25262768

  14. Synthesis in situ of gold nanoparticles by a dialkynyl Fischer carbene complex anchored to glass surfaces

    NASA Astrophysics Data System (ADS)

    Bertolino, María Candelaria; Granados, Alejandro Manuel

    2016-10-01

    In this work we present a detailed study of classic reactions such as "click reaction" and nucleophilic substitution reaction but on glass solid surface (slides). We used different reactive center of a dialkynylalcoxy Fischer carbene complex of tungsten(0) to be anchored to modified glass surface with amine, to obtain aminocarbene, and azide terminal groups. These cycloaddition reaction showed regioselectivity to internal triple bond of dialkynyl Fischer carbene complex without Cu(I) as catalyst. Anyway the carbene anchored was able to act as a reducing agent to produce in situ very stable gold nanoparticles fixed on surface. We showed the characterization of modified glasses by contact angle measurements and XPS. Synthesized nanoparticles were characterized by SEM, XPS, EDS and UV-vis. The modified glasses showed an important enhancement Raman-SERS. This simple, fast and robust method to create a polifunctional and hybrid surfaces can be valuable in a wide range of applications such as Raman-SERS substrates and other optical fields.

  15. Antifouling gold surfaces grafted with aspartic acid and glutamic acid based zwitterionic polymer brushes.

    PubMed

    Li, Wenchen; Liu, Qingsheng; Liu, Lingyun

    2014-10-28

    We report two new amino acid based antifouling zwitterionic polymers, poly(N(4)-(2-methacrylamidoethyl)asparagine) (pAspAA) and poly(N(5)-(2-methacrylamidoethyl)glutamine) (pGluAA). The vinyl monomers were developed from aspartic acid and glutamic acid. Surface-initiated photoiniferter-mediated polymerization was employed to graft polymer brushes from gold surfaces. Different thickness of polymer brushes was controlled by varying UV irradiation time. The nonspecific adsorption from undiluted human blood serum and plasma was studied by surface plasmon resonance (SPR). With the polymer film as thin as 11-12 nm, the adsorption on pAspAA from serum and plasma was as low as 0.75 and 5.18 ng/cm(2), respectively, and 1.88 and 10.15 ng/cm(2), respectively, for pGluAA. The adsorption amount is comparable to or even better than other amino acid based zwitterionic polymers such as poly(serine methacrylate), poly(lysine methacrylamide), and poly(ornithine methacrylamide) and other widely used antifouling polymers such as poly(sulfobetaine methacrylate), even under thinner polymer film thickness. The pAspAA and pGluAA grafted surfaces also showed strong resistance to endothelial cell attachment. The possession of both zwitterionic structure and hydrophilic amide groups, biomimetic property, and multifunctionality make pAspAA and pGluAA promising candidates for biocompatible antifouling functionalizable materials.

  16. Biocompatible gold nanorods: one-step surface functionalization, highly colloidal stability, and low cytotoxicity.

    PubMed

    Liu, Kang; Zheng, Yuanhui; Lu, Xun; Thai, Thibaut; Lee, Nanju Alice; Bach, Udo; Gooding, J Justin

    2015-05-01

    The conjugation of gold nanorods (AuNRs) with polyethylene glycol (PEG) is one of the most effective ways to reduce their cytotoxicity arising from the cetyltrimethylammonium bromide (CTAB) and silver ions used in their synthesis. However, typical PEGylation occurs only at the tips of the AuNRs, producing partially modified AuNRs. To address this issue, we have developed a novel, facile, one-step surface functionalization method that involves the use of Tween 20 to stabilize AuNRs, bis(p-sulfonatophenyl)phenylphosphine (BSPP) to activate the AuNR surface for the subsequent PEGylation, and NaCl to etch silver from the AuNRs. This method allows for the complete removal of the surface-bound CTAB and the most active surface silver from the AuNRs. The produced AuNRs showed far lower toxicity than other methods to PEGylate AuNRs, with no apparent toxicity when their concentration is lower than 5 μg/mL. Even at a high concentration of 80 μg/mL, their cell viability is still four times higher than that of the tip-modified AuNRs. PMID:25874503

  17. Mechanism by which porous structure is formed on the surface of gold alloy containing only Cu as base metal.

    PubMed

    Ohno, Hiroki; Endo, Kazuhiko; Haneda, Katsumi; Tamura, Makoto; Hikita, Kazuhiro

    2005-12-01

    Gold alloys with Cu contents of 10 mass%, 20%, and 30% were used for morphological observation of porous surface structures after heating at 800 degrees C in air followed by pickling with acid solution. With increasing Cu content in the gold alloy, the internal oxidation zone became well-developed in the alloy matrix. The mechanism by which a porous structure was formed on the surface of a gold alloy containing only Cu as a base metal was thought to be as follows: Cu2O which formed along the grain boundaries acted as a diffusion path, permitting the penetration of O2- into the inner alloy matrix, and thereby resulting in internal oxidation occurring predominantly along the grain boundaries. PMID:16445010

  18. An effective surface-enhanced Raman scattering template based on gold nanoparticle/silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Ming-Li; Zhang, Chang-Xing; Wu, Zheng-Long; Jing, Xi-Li; Xu, Hai-Jun

    2014-06-01

    A large-scale Si nanowire array (SiNWA) is fabricated with gold (Au) nanoparticles by simple metal-assisted chemical etching and metal reduction processes. The three-dimensional nanostructured Au/SiNWA is evaluated as an active substrate for surface-enhanced Raman scattering (SERS). The results show that the detection limit for rhodamine 6G is as low as 10-7 M, and the Raman enhancement factor is as large as 105 with a relative standard deviation of less than 25%. After the calibration of the Raman peak intensities of rhodamine 6G and thiram, organic molecules could be quantitatively detected. These results indicate that Au/SiNWA is a promising SERS-active substrate for the detection of biomolecules present in low concentrations. Our findings are an important advance in SERS substrates to allow fast and quantitative detection of trace organic contaminants.

  19. Detection of melamine on fractals of unmodified gold nanoparticles by surface-enhanced Raman scattering.

    PubMed

    Roy, Pradip Kumar; Huang, Yi-Fan; Chattopadhyay, Surojit

    2014-01-01

    A simple way of detecting melamine in raw milk is demonstrated via surface-enhanced Raman spectroscopy (SERS) using fractals of bare and nonfunctionalized ~30 nm gold nanoparticles (AuNP) distributed on a solid support. The technique demonstrates the formation of AuNP fractals, from a random distribution, upon exposure to melamine, that enhance the Raman scattering cross-section to enable detection by SERS. The agglomeration, which is pronounced at higher melamine concentrations, is demonstrated directly through imaging, and the red-shift of the plasmon absorption peak of the AuNP fractal away from 530 nm by finite difference time domain (FDTD) calculations. The agglomeration results in a strong plasmon field, shown by FDTD, over the interparticle sites that enhances the Raman scattering cross-section of melamine and ensures unambiguous detection. Limit of detection of 100 ppb could be achieved reproducibly.

  20. Light-Induced Reversible Self-Assembly of Gold Nanoparticles Surface-Immobilized with Coumarin Ligands.

    PubMed

    He, Huibin; Feng, Miao; Chen, Qidi; Zhang, Xinqi; Zhan, Hongbing

    2016-01-18

    A novel light-induced reversible self-assembly (LIRSA) system is based on the reversible photodimerization and photocleavage of coumarin groups on the surface of gold nanoparticles (AuNPs) in THF solution. Facilitated by coumarin groups, light irradiation at 365 nm triggers the stable assembly of monodisperse AuNPs; the resulting self-assembly system can be disassembled back to the disassembled state by a relatively short exposure to benign UV light. The reversible self-assembly cycle can be repeated 4 times. A specific concentration range of coumarin ligand and the THF solvent were identified to be the two predominant factors that contribute to the LIRSA of AuNPs. This is the first successful application of reversible photodimerization based on a coumarin derivative in the field of AuNP LIRSA. This LIRSA system may provide unique opportunities for the photoregulated synthesis of many adjustable nanostructures and devices.

  1. Evidence for localized surface plasmon polaritons in a liquid crystal containing gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Tiwari, Kunal; Singh, Ankit; Sharma, Suresh

    2012-02-01

    We report an observation of the localized surface plasmon polaritons (SPPs) in a nematic liquid crystal containing 14 nm diameter gold nanoparticles (Au NPs). We observe attenuated total reflection (ATR) of p-polarized laser beam incident upon a high-index prism/liquid-crystal-Au-NPs/glass structure used in the Kretschmann configuration.^1 Unlike the ubiquitous ATR configuration, in which the prism base is coated with a noble metal thin film, our experimental set up does not utilize any such coating. The ATR observed at a specific incident angle and only for p-polarized laser reflects the excitation of localized SPPs at NP/liquid-crystal interface. We discuss possible SPPs related effects, which can significantly change the electro-optical properties of polymer-dispersed liquid crystals.^2

  2. Gold Nanoparticles Supported on Carbon Nitride: Influence of Surface Hydroxyls on Low Temperature Carbon Monoxide Oxidation

    SciTech Connect

    Singh, Joseph A; Dudney, Nancy J; Li, Meijun; Overbury, Steven {Steve} H; Veith, Gabriel M

    2012-01-01

    This paper reports the synthesis of 2.5 nm gold clusters on the oxygen free and chemically labile support carbon nitride (C3N4). Despite having small particle sizes and high enough water partial pressure these Au/C3N4 catalysts are inactive for the gas phase and liquid phase oxidation of carbon monoxide. The reason for the lack of activity is attributed to the lack of surface OH groups on the C3N4. These OH groups are argued to be responsible for the activation of CO in the oxidation of CO. The importance of basic OH groups explains the well document dependence of support isoelectric point versus catalytic activity.

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

    PubMed

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

    2016-07-15

    Calreticulin (CRT) is a cytoplasmic calcium-binding protein. The aim of this study was to investigate CRT presence in cancer with the use of fluorescent gold nanoclusters (AuNCs) and to explore AuNC synthesis using mercaptosuccinic acid (MSA) as a coating agent. MSA-coated AuNCs conferred well-dispersed, bio-stable, water-soluble nanoparticles with bioconjugation capacity and 800-850 nm fluorescence after broad-band excitation. Cell-viability assay revealed good AuNC tolerability. A native CRT amino-terminus corresponding peptide sequence was synthesised and used to generate rabbit site-specific antibodies. Target specificity was demonstrated with antibody blocking in colorectal and breast cancer cell models; human umbilical vein endothelial cells served as controls. We demonstrated a novel route of AuNC/MSA manufacture and CRT presence on colonic and breast cancerous cell surface. AuNCs served as fluorescent bio-probes specifically recognising surface-bound CRT. These results are promising in terms of AuNC application in cancer theranostics and CRT use as surface biomarker in human cancer. PMID:27255548

  4. Impact of core dielectric properties on the localized surface plasmonic spectra of gold-coated magnetic core-shell nanoparticles.

    PubMed

    Chaffin, Elise Anne; Bhana, Saheel; O'Connor, Ryan Timothy; Huang, Xiaohua; Wang, Yongmei

    2014-12-11

    Gold-coated iron oxide core-shell nanoparticles (IO-Au NPs) are of interest for use in numerous biomedical applications because of their unique combined magnetic-plasmonic properties. Although the effects of the core-dielectric constant on the localized surface plasmon resonance (LSPR) peak position of Au-shell particles have been previously investigated, the impact that light-absorbing core materials with complex dielectric functions have on the LSPR peak is not well established. In this study, we use extended Mie theory for multilayer particles to examine the individual effects of the real and imaginary components of core refractive indices on Au-shell NP plasmonic peaks. We find that the imaginary component dampens the intensity of the cavity plasmon and results in a decrease of surface plasmon coupling. For core materials with large imaginary refractive indices, the coupled mode LSPR peak disappears, and only the anticoupled mode remains. Our findings show that the addition of a nonabsorbing polymer layer to the core surface decreases the dampening of the cavity plasmon and increases LSPR spectral intensity. Additionally, we address apparent discrepancies in the literature regarding the effects of Au-shell thickness on LSPR peak shifts.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  6. Surface chemistry but not aspect ratio mediates the biological toxicity of gold nanorods in vitro and in vivo

    PubMed Central

    Wan, Jiali; Wang, Jia-Hong; Liu, Ting; Xie, Zhixiong; Yu, Xue-Feng; Li, Wenhua

    2015-01-01

    Gold nanorods are a promising nanoscale material in clinical diagnosis and treatment. The physicochemical properties of GNRs, including size, shape and surface features, are crucial factors affecting their cytotoxicity. In this study, we investigated the effects of different aspect ratios and surface modifications on the cytotoxicity and cellular uptake of GNRs in cultured cells and in mice. The results indicated that the surface chemistry but not the aspect ratio of GNRs mediates their biological toxicity. CTAB-GNRs with various aspect ratios had similar abilities to induce cell apoptosis and autophagy by damaging mitochondria and activating intracellular reactive oxygen species (ROS). However, GNRs coated with CTAB/PSS, CTAB/PAH, CTAB/PSS/PAH or CTAB/PAH/PSS displayed low toxicity and did not induce cell death. CTAB/PAH-coated GNRs caused minimally abnormal cell morphology compared with CTAB/PSS and CTAB/PSS/PAH coated GNRs. Moreover, the intravenous injection of CTAB/PAH GNRs enabled the GNRs to reach tumor tissues through blood circulation in animals and remained stable, with a longer half-life compared to the other GNRs. Therefore, our results demonstrated that further coating can prevent cytotoxicity and cell death upon CTAB-coated GNR administration, similar to changing the GNR aspect ratio and CTAB/PAH coated GNRs show superior biological properties with better biocompatibility and minimal cytotoxicity. PMID:26096816

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  8. Structure, Bonding, and Dynamics of Alkanethylhiolates on Copper and Gold Clusters and Surfaces

    NASA Astrophysics Data System (ADS)

    Konopka, Martin; Rousseau, Roger; Stich, Ivan; Marx, Dominik

    2005-03-01

    The interaction of alkanethiolates with small coinage metal clusters and (111) surfaces of copper and gold was studied based on density functional theory with a focus on the metal-thiolate junction. Calculation of fragmentation energies indicate that for Cu cluster-thiolate (n=1,3,5,7, and 9) there is a progressive lowering in energy for the fragmentation of the S-C bond in the thiolate from a value of 2.9 eV for n=1 to 1.4 eV for n=9. The detailed electronic origins of this specific weakening are attributed to a polarization of electron density in the S-C bond as induced by bonding with the Cu cluster. For the gold analogues this effect is not observed and fragmentation at the S-C bond experiences only a slight 10% destabilization as n increases from 3 to 9 On the Cu(111) surface the metal to thiolate charge transfer which leads to a non-direction partially ionic bonding with a concurrent flat adsorption energy landscape, As a result, occupation of fcc-hollow, hcp-hollow and fcc-bridge sites is observed during the coarse of a short finite temperature ab-initio molecular dynamics simulation as opposed to a static model where only the hollow sites are stable minima. Comparison of our results with the available experimental evidence and consequences of the electrostatic profile of the metal-molecule interface are presented. The difference between Cu and Au are discussed in the context of relativistic effects.

  9. Quantitative investigation of physical factors contributing to gold nanoparticle-mediated proton dose enhancement.

    PubMed

    Cho, Jongmin; Gonzalez-Lepera, Carlos; Manohar, Nivedh; Kerr, Matthew; Krishnan, Sunil; Cho, Sang Hyun

    2016-03-21

    Some investigators have shown tumor cell killing enhancement in vitro and tumor regression in mice associated with the loading of gold nanoparticles (GNPs) before proton treatments. Several Monte Carlo (MC) investigations have also demonstrated GNP-mediated proton dose enhancement. However, further studies need to be done to quantify the individual physical factors that contribute to the dose enhancement or cell-kill enhancement (or radiosensitization). Thus, the current study investigated the contributions of particle-induced x-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), Auger and secondary electrons, and activation products towards the total dose enhancement. Specifically, GNP-mediated dose enhancement was measured using strips of radiochromic film that were inserted into vials of cylindrical GNPs, i.e. gold nanorods (GNRs), dispersed in a saline solution (0.3 mg of GNRs/g or 0.03% of GNRs by weight), as well as vials containing water only, before proton irradiation. MC simulations were also performed with the tool for particle simulation code using the film measurement setup. Additionally, a high-purity germanium detector system was used to measure the photon spectrum originating from activation products created from the interaction of protons and spherical GNPs present in a saline solution (20 mg of GNPs/g or 2% of GNPs by weight). The dose enhancement due to PIXE/PIGE recorded on the films in the GNR-loaded saline solution was less than the experimental uncertainty of the film dosimetry (<2%). MC simulations showed highly localized dose enhancement (up to a factor 17) in the immediate vicinity (<100 nm) of GNRs, compared with hypothetical water nanorods (WNRs), mostly due to GNR-originated Auger/secondary electrons; however, the average dose enhancement over the entire GNR-loaded vial was found to be minimal (0.1%). The dose enhancement due to the activation products from GNPs was minimal (<0.1%) as well. In conclusion, under the currently

  10. Influence of various surface pretreatments on adherence of sputtered molybdenum disulfide to silver, gold, copper, and bronze

    NASA Technical Reports Server (NTRS)

    Spalvins, T.

    1973-01-01

    Solid film lubricants of radio frequency sputtered molybdenum disulfide (MoS2) were applied to silver, gold, copper, and bronze surfaces that had various pretreatments (mechanical polishing, sputter etching, oxidation, and sulfurization). Optical and electron transmission micrographs and electron diffraction patterns were used to interpret the film formation characteristics and to evaluate the sputtering conditions in regard to the film and substrate compatibility. Sputtered MoS2 films flaked and peeled on silver, copper, and bronze surfaces except when the surfaces had been specially oxidized. The flaking and peeling was a result of sulfide compound formation and the corresponding grain growth of the sulfide film. Sputtered MoS2 films showed no peeling and flaking on gold surfaces regardless of surface pretreatment.

  11. Label-Free Detection of Rare Cell in Human Blood Using Gold Nano Slit Surface Plasmon Resonance

    PubMed Central

    Mousavi, Mansoureh Z.; Chen, Huai-Yi; Hou, Hsien-San; Chang, Chou-Yuan-Yuan; Roffler, Steve; Wei, Pei-Kuen; Cheng, Ji-Yen

    2015-01-01

    Label-free detection of rare cells in biological samples is an important and highly demanded task for clinical applications and various fields of research, such as detection of circulating tumor cells for cancer therapy and stem cells studies. Surface Plasmon Resonance (SPR) as a label-free method is a promising technology for detection of rare cells for diagnosis or research applications. Short detection depth of SPR (400 nm) provides a sensitive method with minimum interference of non-targets in the biological samples. In this work, we developed a novel microfluidic chip integrated with gold nanoslit SPR platform for highly efficient immunomagnetic capturing and detection of rare cells in human blood. Our method offers simple yet efficient detection of target cells with high purity. The approach for detection consists of two steps. Target cells are firs captured on functionalized magnetic nanoparticles (MNPs) with specific antibody I. The suspension containing the captured cells (MNPs-cells) is then introduced into a microfluidic chip integrated with a gold nanoslit film. MNPs-cells bind with the second specific antibody immobilized on the surface of the gold nanoslit and are therefore captured on the sensor active area. The cell binding on the gold nanoslit was monitored by the wavelength shift of the SPR spectrum generated by the gold nanoslits. PMID:25806834

  12. Theoretical investigation of gas-surface interactions

    NASA Technical Reports Server (NTRS)

    Dyall, Kenneth G.

    1994-01-01

    The goal of this project was to develop computational tools for the calculation of the electronic structure of molecules containing heavy atoms, and to use these tools in the study of catalytic processes, with the overall objective of gaining an understanding of the catalytic process which could be used to design more efficient catalysts. The main catalytic system of interest was the combustion of hydrogen on platinum surfaces. Under this project, a flexible Dirac-Hartree-Fock (DHF) program has been developed, a code to calculate DHF correlation energies at the second-order Moeller-Plesset perturbation (PP2) level is almost complete, and code to include correlation at the MCSCF and MCSCF/MP2 level is planned. The tools so far developed have been validated and used to calibrate some more approximate methods, and applied to investigate the importance of relativistic effects in the bonding of hydrogen to platinum.

  13. Investigation of the ion beryllium surface interaction

    SciTech Connect

    Guseva, M.I.; Birukov, A.Yu.; Gureev, V.M.

    1995-09-01

    The self -sputtering yield of the Be was measured. The energy dependence of the Be self-sputtering yield agrees well with that calculated by W. Eckstein et. al. Below 770 K the self-sputtering yield is temperature independent; at T{sub irr}.> 870 K it increases sharply. Hot-pressed samples at 370 K were implanted with monoenergetic 5 keV hydrogen ions and with a stationary plasma (flux power {approximately} 5 MW/m{sup 2}). The investigation of hydrogen behavior in beryllium shows that at low doses hydrogen is solved, but at doses {ge} 5x10{sup 22} m{sup -2} the bubbles and channels are formed. It results in hydrogen profile shift to the surface and decrease of its concentration. The sputtering results in further concentration decrease at doses > 10{sup 25}m{sup -2}.

  14. Energetic stabilities of thiolated pyrimidines on gold nanoparticles investigated by Raman spectroscopy and density functional theory calculations.

    PubMed

    Ganbold, Erdene-Ochir; Yoon, Jinha; Cho, Kwang-Hwi; Joo, Sang-Woo

    2015-01-01

    The adsorption structures of 2-thiocytosine (2TC) on gold surfaces were examined by means of vibrational Raman spectroscopy and quantum mechanical density functional theory calculations. The 1H-thione-amino form was calculated to be most stable among the six examined tautomers. The three plausible binding geometries of sulfur, pyrimidine nitrogen, and amino group binding modes were calculated to estimate the binding energies of the 1H-thione-amino form with six gold cluster atoms. Thiouracils including 2-thiouracil (2TU), 4-thiouracil (4TU), and 6-methyl-2-thiouracil (6M2TU) were also studied to compare their relative binding energies on gold atoms. The intracellular localization of a DNA base analog of 2TC on gold nanoparticles (AuNPs) in HeLa cells was identified by means of surface-enhanced Raman scattering. AuNPs were modified with 2TC by self-assembly. Our dark-field microscopy and z-depth-dependent confocal Raman spectroscopy indicated that 2TC-assembled AuNPs could be found inside cancer cells. On the other hand, we did not observe noticeably strong Raman peaks in the cases of thiouracils including 2TU, 4TU, and 6M2TU. This may be due to the additional amino group of 2TC, which can lead to a stronger binding of adsorbates on AuNPs.

  15. Hydrodechlorination catalytic activity of gold nanoparticles supported on TiO 2 modified SBA-15 investigated by IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hannus, I.; Búza, M.; Beck, A.; Guczi, L.; Sáfrán, G.

    2009-04-01

    The hydrodechlorination catalytic activity of gold nanoparticles on SBA-15 silica modified by TiO 2 promoters has been investigated. Comparing the hydrodechlorination catalytic activity platinum nanoparticles supported on TiO 2 catalyst was used in the hydrodechlorination of CCl 4 as model compound. The IR spectroscopic experimental results showed that the gold nanoparticles have higher catalytic activity, than platinum ones. The two samples were tested also in CO oxidation, in which Au/TiO 2/SBA-15 possess also somewhat higher activity than Pt/TiO 2.

  16. Enhanced detection sensitivity of Escherichia coli O157:H7 using surface-modified gold nanorods

    PubMed Central

    Ramasamy, Mohankandhasamy; Yi, Dong Kee; An, Seong Soo A

    2015-01-01

    Escherichia coli O157:H7 (O157) is a Gram negative and highly virulent bacteria found in food and water sources, and is a leading cause of chronic diseases worldwide. Diagnosis and prevention from the infection require simple and rapid analysis methods for the detection of pathogens, including O157. Endogenous membrane peroxidase, an enzyme present on the surface of O157, was used for the colorimetric detection of bacteria by catalytic oxidation of the peroxidase substrate. In this study, we have analyzed the impact of the synthesized bare gold nanorods (AuNRs) and silica-coated AuNRs on the growth of E. coli O157. Along with the membrane peroxidase activity of O157, other bacteria strains were analyzed. Different concentrations of nanorods were used to analyze the growth responses, enzymatic changes, and morphological alterations of bacteria by measuring optical density, 3,3′,5,5′-tetramethylbenzidine assay, flow cytometry analysis, and microscopy studies. The results revealed that O157 showed higher and continuous membrane peroxidase activity than other bacteria. Furthermore, O157 treated with bare AuNRs showed a decreased growth rate in comparison with the bacteria with surface modified AuNRs. Interestingly, silica-coated AuNRs favored the growth of bacteria and also increased membrane peroxidase activity. This result can be particularly important for the enzymatic analysis of surface treated AuNRs in various microbiological applicants. PMID:26347081

  17. Enhanced detection sensitivity of Escherichia coli O157:H7 using surface-modified gold nanorods.

    PubMed

    Ramasamy, Mohankandhasamy; Yi, Dong Kee; An, Seong Soo A

    2015-01-01

    Escherichia coli O157:H7 (O157) is a Gram negative and highly virulent bacteria found in food and water sources, and is a leading cause of chronic diseases worldwide. Diagnosis and prevention from the infection require simple and rapid analysis methods for the detection of pathogens, including O157. Endogenous membrane peroxidase, an enzyme present on the surface of O157, was used for the colorimetric detection of bacteria by catalytic oxidation of the peroxidase substrate. In this study, we have analyzed the impact of the synthesized bare gold nanorods (AuNRs) and silica-coated AuNRs on the growth of E. coli O157. Along with the membrane peroxidase activity of O157, other bacteria strains were analyzed. Different concentrations of nanorods were used to analyze the growth responses, enzymatic changes, and morphological alterations of bacteria by measuring optical density, 3,3',5,5'-tetramethylbenzidine assay, flow cytometry analysis, and microscopy studies. The results revealed that O157 showed higher and continuous membrane peroxidase activity than other bacteria. Furthermore, O157 treated with bare AuNRs showed a decreased growth rate in comparison with the bacteria with surface modified AuNRs. Interestingly, silica-coated AuNRs favored the growth of bacteria and also increased membrane peroxidase activity. This result can be particularly important for the enzymatic analysis of surface treated AuNRs in various microbiological applicants. PMID:26347081

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  19. Significant Enhancement of the Chiral Correlation Length in Nematic Liquid Crystals by Gold Nanoparticle Surfaces Featuring Axially Chiral Binaphthyl Ligands.

    PubMed

    Mori, Taizo; Sharma, Anshul; Hegmann, Torsten

    2016-01-26

    Chirality is a fundamental scientific concept best described by the absence of mirror symmetry and the inability to superimpose an object onto its mirror image by translation and rotation. Chirality is expressed at almost all molecular levels, from single molecules to supramolecular systems, and present virtually everywhere in nature. Here, to explore how chirality propagates from a chiral nanoscale surface, we study gold nanoparticles functionalized with axially chiral binaphthyl molecules. In particular, we synthesized three enantiomeric pairs of chiral ligand-capped gold nanoparticles differing in size, curvature, and ligand density to tune the chirality transfer from nanoscale solid surfaces to a bulk anisotropic liquid crystal medium. Ultimately, we are examining how far the chirality from a nanoparticle surface reaches into a bulk material. Circular dichroism spectra of the gold nanoparticles decorated with binaphthyl thiols confirmed that the binaphthyl moieties form a cisoid conformation in isotropic organic solvents. In the chiral nematic liquid crystal phase, induced by dispersing the gold nanoparticles into an achiral anisotropic nematic liquid crystal solvent, the binaphthyl moieties on the nanoparticle surface form a transoid conformation as determined by imaging the helical twist direction of the induced cholesteric phase. This suggests that the ligand density on the nanoscale metal surfaces provides a dynamic space to alter and adjust the helicity of binaphthyl derivatives in response to the ordering of the surrounding medium. The helical pitch values of the induced chiral nematic phase were determined, and the helical twisting power (HTP) of the chiral gold nanoparticles calculated to elucidate the chirality transfer efficiency of the binaphthyl ligand capped gold nanoparticles. Remarkably, the HTP increases with increasing diameter of the particles, that is, the efficiency of the chirality transfer of the binaphthyl units bound to the nanoparticle

  20. Spectroscopic investigations, antimicrobial, and cytotoxic activity of green synthesized gold nanoparticles.

    PubMed

    Lokina, S; Suresh, R; Giribabu, K; Stephen, A; Lakshmi Sundaram, R; Narayanan, V

    2014-08-14

    The gold nanoparticles (AuNPs) were synthesized by using naturally available Punica Granatum fruit extract as reducing and stabilizing agent. The biosynthesized AuNPs was characterized by using UV-Vis, fluorescence, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric (TGA) analysis. The surface plasmon resonance (SPR) band at 585nm confirmed the reduction of auric chloride to AuNPs. The crystalline nature of the biosynthesized AuNPs was confirmed from the HRTEM images, XRD and selected area electron diffraction (SAED) pattern. The HRTEM images showed the mixture of triangular and spherical-like AuNPs having size between 5 and 20nm. The weight loss of the AuNPs was measured by TGA as a function of temperature under a controlled atmosphere. The biomolecules are responsible for the reduction of AuCl4(-) ions and the formation of stable AuNPs which was confirmed by FTIR measurement. The synthesized AuNPs showed an excellent antibacterial activity against Candida albicans (ATCC 90028), Aspergillus flavus (ATCC 10124), Staphylococcus aureus (ATCC 25175), Salmonella typhi (ATCC 14028) and Vibrio cholerae (ATCC 14033). The minimum inhibitory concentration (MIC) of AuNPs was recorded against various microorganisms. Further, the synthesized AuNPs shows an excellent cytotoxic result against HeLa cancer cell lines at different concentrations. PMID:24755638

  1. Spectroscopic investigations, antimicrobial, and cytotoxic activity of green synthesized gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Lokina, S.; Suresh, R.; Giribabu, K.; Stephen, A.; Lakshmi Sundaram, R.; Narayanan, V.

    2014-08-01

    The gold nanoparticles (AuNPs) were synthesized by using naturally available Punica Granatum fruit extract as reducing and stabilizing agent. The biosynthesized AuNPs was characterized by using UV-Vis, fluorescence, high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric (TGA) analysis. The surface plasmon resonance (SPR) band at 585 nm confirmed the reduction of auric chloride to AuNPs. The crystalline nature of the biosynthesized AuNPs was confirmed from the HRTEM images, XRD and selected area electron diffraction (SAED) pattern. The HRTEM images showed the mixture of triangular and spherical-like AuNPs having size between 5 and 20 nm. The weight loss of the AuNPs was measured by TGA as a function of temperature under a controlled atmosphere. The biomolecules are responsible for the reduction of AuCl4- ions and the formation of stable AuNPs which was confirmed by FTIR measurement. The synthesized AuNPs showed an excellent antibacterial activity against Candida albicans (ATCC 90028), Aspergillus flavus (ATCC 10124), Staphylococcus aureus (ATCC 25175), Salmonella typhi (ATCC 14028) and Vibrio cholerae (ATCC 14033). The minimum inhibitory concentration (MIC) of AuNPs was recorded against various microorganisms. Further, the synthesized AuNPs shows an excellent cytotoxic result against HeLa cancer cell lines at different concentrations.

  2. Maintaining the pluripotency of mouse embryonic stem cells on gold nanoparticle layers with nanoscale but not microscale surface roughness

    NASA Astrophysics Data System (ADS)

    Lyu, Zhonglin; Wang, Hongwei; Wang, Yanyun; Ding, Kaiguo; Liu, Huan; Yuan, Lin; Shi, Xiujuan; Wang, Mengmeng; Wang, Yanwei; Chen, Hong

    2014-05-01

    Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold nanoparticle layer (GNPL) with nano-, sub-micro-, and microscale surface roughnesses were used to study the roles of these structures in regulating the behaviors of mouse ESCs (mESCs) under feeder-free conditions. The distinctive results from Oct-4 immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) demonstrate that nanoscale and low sub-microscale surface roughnesses (Rq less than 392 nm) are conducive to the long-term maintenance of mESC pluripotency, while high sub-microscale and microscale surface roughnesses (Rq greater than 573 nm) result in a significant loss of mESC pluripotency and a faster undirectional differentiation, particularly in long-term culture. Moreover, the likely signalling cascades engaged in the topological sensing of mESCs were investigated and their role in affecting the maintenance of the long-term cell pluripotency was discussed by analyzing the expression of proteins related to E-cadherin mediated cell-cell adhesions and integrin-mediated focal adhesions (FAs). Additionally, the conclusions from MTT, cell morphology staining and alkaline phosphatase (ALP) activity assays show that the surface roughness can provide a potent regulatory signal for various mESC behaviors, including cell attachment, proliferation and osteoinduction.Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold

  3. Interactions of small gold clusters, Aun (n=1-3), with graphyne: theoretical investigation.

    PubMed

    Azizi, Elmira; Tehrani, Zahra Aliakbar; Jamshidi, Zahra

    2014-11-01

    The interactions of gold atom and clusters (Au2 and Au3) with the active sites of graphyne (GY) have been investigated using density functional theory (PBE, PBE-D3, and B3LYP-D3). In order to compare performance of DFT functional (BP86, PBE, TPSSh, B3LYP, PBE-D3, TPSSh-D3, and B3LYP-D3), the interactions of Au2 with various functional groups such as -sp, -sp(2) and aromatic sp(2) carbon atoms, -sp, -sp(2) and aromatic sp(2)-bonds have been investigated and also compared with the ab initio MP2 results. Additionally, the nature of interactions for graphyne-Au2 complexes are interpreted by means of the natural bond orbital (NBO), the quantum theory of atoms in molecules (QTAIM) and energy decomposition analysis (EDA) and compared with those of related graphene-Au2. This study suggests that graphyne shows complex behavior in comparison to those of graphene and could also be useful in modeling of the next generation electronic devices.

  4. Combinatorial investigation of the isolated nanoparticle to coalescent layer transition in a gradient sputtered gold nanoparticle layer on top of polystyrene

    SciTech Connect

    Roth, S.V.; Walter, H.; Burghammer, M.; Riekel, C.; Lengeler, B.; Schroer, C.; Kuhlmann, M.; Walther, T.; Sehrbrock, A.; Domnick, R.; Mueller-Buschbaum, P.

    2006-01-09

    Within a combinatorial investigation, a gradient sputtered gold layer on top of polystyrene on silicon substrate is addressed. Results from a real-space inspection by transmission electron microscopy are compared with surface-sensitive microbeam grazing incidence small-angle x-ray scattering. The combinatorial approach allows distinguishing different morphologies prepared under exactly the same environmental conditions on one single substrate. The transition of a coalescent layer to an isolated nanoparticle layer is determined as a function of sputter rate. Though optical spectra show only slight differences, the morphology and structure are distinctly different from evaporated layers prepared with same mass thickness.

  5. Maintaining the pluripotency of mouse embryonic stem cells on gold nanoparticle layers with nanoscale but not microscale surface roughness.

    PubMed

    Lyu, Zhonglin; Wang, Hongwei; Wang, Yanyun; Ding, Kaiguo; Liu, Huan; Yuan, Lin; Shi, Xiujuan; Wang, Mengmeng; Wang, Yanwei; Chen, Hong

    2014-06-21

    Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold nanoparticle layer (GNPL) with nano-, sub-micro-, and microscale surface roughnesses were used to study the roles of these structures in regulating the behaviors of mouse ESCs (mESCs) under feeder-free conditions. The distinctive results from Oct-4 immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) demonstrate that nanoscale and low sub-microscale surface roughnesses (Rq less than 392 nm) are conducive to the long-term maintenance of mESC pluripotency, while high sub-microscale and microscale surface roughnesses (Rq greater than 573 nm) result in a significant loss of mESC pluripotency and a faster undirectional differentiation, particularly in long-term culture. Moreover, the likely signalling cascades engaged in the topological sensing of mESCs were investigated and their role in affecting the maintenance of the long-term cell pluripotency was discussed by analyzing the expression of proteins related to E-cadherin mediated cell-cell adhesions and integrin-mediated focal adhesions (FAs). Additionally, the conclusions from MTT, cell morphology staining and alkaline phosphatase (ALP) activity assays show that the surface roughness can provide a potent regulatory signal for various mESC behaviors, including cell attachment, proliferation and osteoinduction.

  6. Gold/palladium and silver/palladium colloids as novel metallic substrates for surface-enhanced Raman scattering.

    PubMed

    Pergolese, Barbara; Bigotto, Adriano; Muniz-Miranda, Maurizio; Sbrana, Giuseppe

    2005-02-01

    New surface-enhanced Raman scattering (SERS) substrates, composed of gold or silver colloidal nanoparticles doped with palladium, were prepared. These novel colloids are stable and maintain a satisfactory SERS efficiency, even after long aging. The interest in doping the coinage metal nanoparticles with palladium is due to the well-known catalytic activity of this metal. Transmission electron microscopy (TEM) and ultraviolet-visible absorption spectroscopy were used to characterize the shape and size of the metal particles. It was found that these bimetallic colloidal nanoparticles have a core-shell structure, with gold or silver coated with palladium clusters.

  7. Templated Growth of Surface Enhanced Raman Scattering-Active Branched Gold Nanoparticles within Radial Mesoporous Silica Shells

    PubMed Central

    2015-01-01

    Noble metal nanoparticles are widely used as probes or substrates for surface enhanced Raman scattering (SERS), due to their characteristic plasmon resonances in the visible and near-IR spectral ranges. Aiming at obtaining a versatile system with high SERS performance, we developed the synthesis of quasi-monodisperse, nonaggregated gold nanoparticles protected by radial mesoporous silica shells. The radial mesoporous channels were used as templates for the growth of gold tips branching out from the cores, thereby improving the plasmonic performance of the particles while favoring the localization of analyte molecules at high electric field regions: close to the tips, inside the pores. The method, which additionally provides control over tip length, was successfully applied to gold nanoparticles with various shapes, leading to materials with highly efficient SERS performance. The obtained nanoparticles are stable in ethanol and water upon thermal consolidation and can be safely stored as a powder. PMID:26370658

  8. Surface Plasmon Resonance in Novel Nanocomposite Gold/Lead Zirconate Titanate Films Prepared by Aerosol Deposition Method

    NASA Astrophysics Data System (ADS)

    Park, Jae-Hyuk; Akedo, Jun; Nakada, Masafumi

    2006-09-01

    We prepared gold/lead zirconate titanate (PZT) nanocomposite thick films by the aerosol deposition method (ADM) for the first time and report their enhanced surface plasmon resonance (SPR) properties. ADM has been attracting much attention for its ability to deposit complex composite films at a high deposition rate and a low process temperature. Composite metal-dielectric powders are prepared from submicron particles of PZT and nano particles of gold (10-40 nm) with concentrations below 1 wt %. Nanocomposite gold/PZT 3-μm-thick film acquired enhanced SPR at approximately 640 nm as a result of annealing. The SPR position in nanocomposite films deposited by ADM can be precisely controlled by adjusting the dielectric constant of the host matrix by annealing. Moreover, nanogold particles were spatially very well distributed in the PZT matrix and showed no growth in spite of annealing at 600 °C.

  9. Templated Growth of Surface Enhanced Raman Scattering-Active Branched Gold Nanoparticles within Radial Mesoporous Silica Shells.

    PubMed

    Sanz-Ortiz, Marta N; Sentosun, Kadir; Bals, Sara; Liz-Marzán, Luis M

    2015-10-27

    Noble metal nanoparticles are widely used as probes or substrates for surface enhanced Raman scattering (SERS), due to their characteristic plasmon resonances in the visible and near-IR spectral ranges. Aiming at obtaining a versatile system with high SERS performance, we developed the synthesis of quasi-monodisperse, nonaggregated gold nanoparticles protected by radial mesoporous silica shells. The radial mesoporous channels were used as templates for the growth of gold tips branching out from the cores, thereby improving the plasmonic performance of the particles while favoring the localization of analyte molecules at high electric field regions: close to the tips, inside the pores. The method, which additionally provides control over tip length, was successfully applied to gold nanoparticles with various shapes, leading to materials with highly efficient SERS performance. The obtained nanoparticles are stable in ethanol and water upon thermal consolidation and can be safely stored as a powder. PMID:26370658

  10. Electrochemical control of creep in nanoporous gold

    SciTech Connect

    Ye, Xing-Long; Jin, Hai-Jun

    2013-11-11

    We have investigated the mechanical stability of nanoporous gold (npg) in an electrochemical environment, using in situ dilatometry and compression experiments. It is demonstrated that the gold nano-ligaments creep under the action of surface stress which leads to spontaneous volume contractions in macroscopic npg samples. The creep of npg, under or without external forces, can be controlled electrochemically. The creep rate increases with increasing potential in double-layer potential region, and deceases to almost zero when the gold surface is adsorbed with oxygen. Surprisingly, we also noticed a correlation between creep and surface diffusivity, which links the deformation of nanocrystals to mobility of surface atoms.

  11. Boron nitride nanosheets as improved and reusable substrates for gold nanoparticles enabled surface enhanced Raman spectroscopy.

    PubMed

    Cai, Qiran; Li, Lu Hua; Yu, Yuanlie; Liu, Yun; Huang, Shaoming; Chen, Ying; Watanabe, Kenji; Taniguchi, Takashi

    2015-03-28

    Atomically thin boron nitride (BN) nanosheets have been found to be excellent substrates for noble metal particles enabled surface enhanced Raman spectroscopy (SERS), thanks to their good adsorption of aromatic molecules, high thermal stability and weak Raman scattering. Faceted gold (Au) nanoparticles have been synthesized on BN nanosheets using a simple but controllable and reproducible sputtering and annealing method. The size and density of the Au particles can be controlled by sputtering time, current and annealing temperature etc. Under the same sputtering and annealing conditions, the Au particles on BN of different thicknesses show various sizes because the surface diffusion coefficients of Au depend on the thickness of BN. Intriguingly, decorated with similar morphology and distribution of Au particles, BN nanosheets exhibit better Raman enhancements than silicon substrates as well as bulk BN crystals. Additionally, BN nanosheets show no noticeable SERS signal and hence cause no interference to the Raman signal of the analyte. The Au/BN substrates can be reused by heating in air to remove the adsorbed analyte without loss of SERS enhancement. PMID:25714659

  12. Simple and Flexible Model for Laser-Driven Antibody-Gold Surface Interactions: Functionalization and Sensing.

    PubMed

    Della Ventura, Bartolomeo; Ambrosio, Antonio; Fierro, Annalisa; Funari, Riccardo; Gesuele, Felice; Maddalena, Pasquale; Mayer, Dirk; Pica Ciamarra, Massimo; Velotta, Raffaele; Altucci, Carlo

    2016-08-24

    Interactions between biomolecules and between substrates and biomolecules is a crucial issue in physics and applications to topics such as biotechnology and organic electronics. The efficiency of bio- and mechanical sensors, of organic electronics systems, and of a number of other devices critically depends on how molecules are deposited on a surface so that these acquire specific functions. Here, we tackle this vast problem by developing a coarse grained model of biomolecules having a recognition function, such as antibodies, capable to quantitatively describe in a simple manner essential phenomena: antigen-antibody and antibody substrate interactions. The model is experimentally tested to reproduce the results of a benchmark case, such as (1) gold surface functionalization with antibodies and (2) antibody-antigen immune-recognition function. The agreement between experiments and model prediction is excellent, thus unveiling the mechanism for antibody immobilization onto metals at the nanoscale in various functionalization schemes. These results shed light on the geometrical packing properties of the deposited molecules, and may open the way to a novel coarse-grained based approach to describe other processes where molecular packing is a key issue with applications in a huge number of fields from nano- to biosciences.

  13. Synthesis and characterization of surface-enhanced Raman-scattered gold nanoparticles

    PubMed Central

    Kalmodia, Sushma; Harjwani, Jaidev; Rajeswari, Raguraman; Yang, Wenrong; Barrow, Colin J; Ramaprabhu, Sundara; Krishnakumar, Subramanian; Elchuri, Sailaja V

    2013-01-01

    In this paper, we report a simple, rapid, and robust method to synthesize surface-enhanced Raman-scattered gold nanoparticles (GNPs) based on green chemistry. Vitis vinifera L. extract was used to synthesize noncytotoxic Raman-active GNPs. These GNPs were characterized by ultraviolet-visible spectroscopy, dynamic light-scattering, Fourier-transform infrared (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy. The characteristic surface plasmon-resonance band at ~ 528 nm is indicative of spherical particles, and this was confirmed by TEM. The N–H and C–O stretches in FTIR spectroscopy indicated the presence of protein molecules. The predominant XRD plane at (111) and (200) indicated the crystalline nature and purity of GNPs. GNPs were stable in the buffers used for biological studies, and exhibited no cytotoxicity in noncancerous MIO-M1 (Müller glial) and MDA-MB-453 (breast cancer) cell lines. The GNPs exhibited Raman spectral peaks at 570, 788, and 1,102 cm−1. These new GNPs have potential applications in cancer diagnosis, therapy, and ultrasensitive biomarker detection. PMID:24235830

  14. Inhibitation of cellular toxicity of gold nanoparticles by surface encapsulation of silica shell for hepatocarcinoma cell application.

    PubMed

    Zeng, Qinghui; Zhang, Youlin; Ji, Wenyu; Ye, Weiguang; Jiang, Yinglei; Song, Jie

    2014-01-01

    Nanotechnology, as a double-edged sword, endows gold nanoparticles (GNPs) more "power" in bioimaging and theragnostics, whereas an outstanding issue associated with the biocompatibility of GNPs should also be addressed. Especially for the silica-coated gold nanospheres (GNSs) and gold nanorods (GNRs), there is increasing attention to explore the application, because the surface silica encapsulation has been proved to be an alternative strategy for other organic surface coatings. However, among those reports there are very limited publications to focus on the toxicity of silica-coated GNSs and GNRs. Besides, the existing detoxification methods via surface chemistry on GNPs greatly improve the biocompatibility but still undergo challenges for high dose (>100 pM) demand and long-term stability. Here, we demonstrated a straightforward, low-cost, universal strategy for the surface chemistry on GNPs via silica encapsulating. Different size, shape, dose, and surface capping of GNPs for the nanotoxicity test have been carefully discussed. After silica encapsulating, the detoxification for all GNPs presents significantly from HepG2 cell proliferation results, especially for the GNRs. This new straightforward strategy will definitely rationalize the biocompatibility issue of GNPs and also provide potential for other surface chemistry methodology in biomedical fields. PMID:25313634

  15. Specific interactions of functionalised gold surfaces with ammonium perchlorate or starch; towards a chemical cartography of their mixture

    NASA Astrophysics Data System (ADS)

    Mercier, D.; Mercader, C.; Quere, S.; Hairault, L.; Méthivier, C.; Pradier, C. M.

    2012-10-01

    By functionalising gold samples, planar wafers or AFM tips, with an acid- or an amino acid-terminated thiols, mercaptoundecanoic acid (MUA) and homocystein (H-Cyst) respectively, we were able to differentiate the interactions with ammonium perchlorate (AP) and starch (S), two components of a nanocomposition mixture. To do so, the interaction between gold functionalized surfaces and the two targeted compounds have been characterized and quantified by several complementary techniques. Polarisation modulation-infrared spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS), providing chemical analyses of gold surfaces after contacting S or AP, proved that both compounds were retained on MUA or H-Cyst-modified surfaces, but to various extents. Quartz crystal microbalance on-line measurements enabled to monitor the kinetics of interaction and showed distinct differences in the behaviour of MUA and H-Cyst-surfaces towards the two compounds. Having observed that only H-Cyst-modified surfaces enables to get a contrast on the chemical force microscopy (CFM) images, this new result could be well explained by examining the data obtained by combining the above-mentioned surface characterisation techniques.

  16. Investigation of argon ion sputtering on the secondary electron emission from gold samples

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Cui, Wanzhao; Li, Yun; Xie, Guibai; Zhang, Na; Wang, Rui; Hu, Tiancun; Zhang, Hongtai

    2016-09-01

    Secondary electron (SE) yield, δ, is a very sensitive surface property. The values of δ often are not consistent for even identical materials. The influence of surface changes on the SE yield was investigated experimentally in this article. Argon ion sputtering was used to remove the contamination from the surface. Surface composition was monitored by X-ray photoelectron spectroscopy (XPS) and surface topography was scanned by scanning electron microscope (SEM) and atomic force microscope (AFM) before and after every sputtering. It was found that argon sputtering can remove contamination and roughen the surface. An "equivalent work function" is presented in this thesis to establish the relationship between SE yield and surface properties. Argon ion sputtering of 1.5keV leads to a significant increase of so called "work function" (from 3.7 eV to 6.0 eV), and a decrease of SE yield (from 2.01 to 1.54). These results provided a new insight into the influence of surface changes on the SE emission.

  17. Surface coverage and structure of mixed DNA/alkylthiol monolayers on gold: characterization by XPS, NEXAFS, and fluorescence intensity measurements.

    PubMed

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

    2006-05-15

    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 --> pi* 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

  18. Glucose sensing using near-infrared surface-enhanced Raman spectroscopy: gold surfaces, 10-day stability, and improved accuracy.

    PubMed

    Stuart, Douglas A; Yonzon, Chanda Ranjit; Zhang, Xiaoyu; Lyandres, Olga; Shah, Nilam C; Glucksberg, Matthew R; Walsh, Joseph T; Van Duyne, Richard P

    2005-07-01

    This research presents the achievement of significant milestones toward the development of a minimally invasive, continuously monitoring, glucose-sensing platform based on the optical quantitation of glucose in interstitial fluid. We expand our initial successes in the measurement of glucose by surface-enhanced Raman scattering (SERS), demonstrating substantial improvements not only in the quality and optical properties of the substrate system itself but also in the robustness of the measurement methodology and the amenability of the technique to compact, diode laser-based instrumentation. Herein, we compare the long-term stability of gold to silver film over nanosphere (AuFON, AgFON) substrates functionalized with a partitioning self-assembled monolayer (SAM) using both electrochemical and SERS measurements. AuFONs were found to be stable for a period of at least 11 days. The switch to AuFONs not only provides a more stable surface for SAM formation but also yields better chemometric results, with improved calibration and validation over a range of 0.5-44 mM (10-800 mg/dL). Measured values for glucose concentrations in phosphate-buffered saline (pH approximately 7.4) based on 160 independent SERS measurements on AuFONs have a root-mean-square error of prediction of 2.7 mM (49.5 mg/dL), with 91% of the values falling within an extended A-B range on an expanded Clarke error grid. Furthermore, AuFONs exhibit surface plasmon resonances at longer wavelengths than similar AgFONs, which make them more efficient for SERS at near-infrared wavelengths, enabling the use of low-power diode lasers in future devices.

  19. Arsenic speciation and mobility in surface water at Lucky Shot Gold Mine, Alaska.

    PubMed

    Torrance, Keith; Keenan, Helen; Munk, Leeann; Hagedorn, Birgit

    2012-12-01

    Historical mining in Alaska has created a legacy of approximately 6,830 abandoned mine sites which include adits, tailing piles and contaminated land that continue to impact surface and groundwater quality through run-off and leaching of potentially toxic metals, especially arsenic (As). One such site is the Lucky Shot Gold Mine in Hatcher Pass, south-central Alaska, which operated from 1920 until 1942, mining gold-bearing quartz veins hosted in a Cretaceous tonalite intrusion. Arsenopyrite (FeAsS) and pyrite (FeS(2)) present in the quartz veins contribute to elevated As levels in water draining, abandoned mine adits. As future underground mining at Lucky Shot may further adversely impact water quality, baseline geochemical studies were undertaken to assess As mobility in the vicinity of the mine adits. Water samples were collected from streams, adits and boreholes around the mine and analysed for major and minor elements using inductively coupled plasma-mass spectrometry (ICP-MS) and for anions by ion chromatography (IC). Arsenic species separation was performed in the field to determine the ratio of inorganic As(III)/As(V) using anion-exchange chromatography, following established methods. It was determined that water draining the adits had elevated levels of As roughly seventy times the United States Environmental Protection Agency Drinking Water Standard of 10 μg L(-1), although this was rapidly diluted downstream in Craigie Creek to <2 μg L(-1). Adit and surface water pH was circum-neutral and displayed no characteristics of acid mine drainage. Despite being well oxygenated, As(III) is the dominant As species in adit water, accounting for close to 100 % of total As. The proportion of As(V) increases downstream of the adits, as some As(III) is oxidized, but the speciation enhances arsenic mobility at the site. The δ(18)O measurements indicate that the water in the system has a short residence time as it is very similar to meteoric water, supporting the

  20. Investigating the structural evolution of thiolate protected gold clusters from first-principles

    NASA Astrophysics Data System (ADS)

    Pei, Yong; Zeng, Xiao Cheng

    2012-06-01

    Unlike bulk materials, the physicochemical properties of nano-sized metal clusters can be strongly dependent on their atomic structure and size. Over the past two decades, major progress has been made in both the synthesis and characterization of a special class of ligated metal nanoclusters, namely, the thiolate-protected gold clusters with size less than 2 nm. Nevertheless, the determination of the precise atomic structure of thiolate-protected gold clusters is still a grand challenge to both experimentalists and theorists. The lack of atomic structures for many thiolate-protected gold clusters has hampered our in-depth understanding of their physicochemical properties and size-dependent structural evolution. Recent breakthroughs in the determination of the atomic structure of two clusters, [Au25(SCH2CH2Ph)18]q (q = -1, 0) and Au102(p-MBA)44, from X-ray crystallography have uncovered many new characteristics regarding the gold-sulfur bonding as well as the atomic packing structure in gold thiolate nanoclusters. Knowledge obtained from the atomic structures of both thiolate-protected gold clusters allows researchers to examine a more general ``inherent structure rule'' underlying this special class of ligated gold nanoclusters. That is, a highly stable thiolate-protected gold cluster can be viewed as a combination of a highly symmetric Au core and several protecting gold-thiolate ``staple motifs'', as illustrated by a general structural formula [Au]a+a'[Au(SR)2]b[Au2(SR)3]c[Au3(SR)4]d[Au4(SR)5]e where a, a', b, c, d and e are integers that satisfy certain constraints. In this review article, we highlight recent progress in the theoretical exploration and prediction of the atomic structures of various thiolate-protected gold clusters based on the ``divide-and-protect'' concept in general and the ``inherent structure rule'' in particular. As two demonstration examples, we show that the theoretically predicted lowest-energy structures of Au25(SR)8- and Au38(SR)24 (-R

  1. Facile synthesis of hydrangea flower-like hierarchical gold nanostructures with tunable surface topographies for single-particle surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Song, C. Y.; Zhou, N.; Yang, B. Y.; Yang, Y. J.; Wang, L. H.

    2015-10-01

    The physicochemical properties of noble metal nanocrystals depend strongly on their size and shape, and it is becoming clear that the design and facile synthesis of particular nanostructures with tailored shape and size is especially important. Herein a novel class of hydrangea flower-like hierarchical gold nanostructures with tunable surface topographies and optical properties are prepared for the first time by a facile, one-pot, seedless synthesis using ascorbic acid (AA) to reduce hydrogen tetrachloroaurate (HAuCl4) in the presence of (1-hexadecyl)trimethylammonium chloride (CTAC). The morphologies of the synthesized gold nanoflowers are controlled and fine-tuned by varying the synthetic conditions such as the concentration of reagents and the growth temperature. Due to their unique hierarchical three-dimensional (3D) structures with rich hot spots, these gold nanoflowers exhibit an efficient performance in single-particle surface-enhanced Raman scattering (SERS). The work stands out as an interesting approach for anisotropic particle synthesis and morphological control, and the proposed novel, hierarchical gold nanoflowers have a number of exciting potential applications in SERS-based sensors.The physicochemical properties of noble metal nanocrystals depend strongly on their size and shape, and it is becoming clear that the design and facile synthesis of particular nanostructures with tailored shape and size is especially important. Herein a novel class of hydrangea flower-like hierarchical gold nanostructures with tunable surface topographies and optical properties are prepared for the first time by a facile, one-pot, seedless synthesis using ascorbic acid (AA) to reduce hydrogen tetrachloroaurate (HAuCl4) in the presence of (1-hexadecyl)trimethylammonium chloride (CTAC). The morphologies of the synthesized gold nanoflowers are controlled and fine-tuned by varying the synthetic conditions such as the concentration of reagents and the growth temperature. Due to

  2. Bio-active nanoemulsions enriched with gold nanoparticle, marigold extracts and lipoic acid: In vitro investigations.

    PubMed

    Guler, Emine; Barlas, F Baris; Yavuz, Murat; Demir, Bilal; Gumus, Z Pinar; Baspinar, Yucel; Coskunol, Hakan; Timur, Suna

    2014-09-01

    A novel and efficient approach for the preparation of enriched herbal formulations was described and their potential applications including wound healing and antioxidant activity (cell based and cell free) were investigated via in vitro cell culture studies. Nigella sativa oil was enriched with Calendula officinalis extract and lipoic acid capped gold nanoparticles (AuNP-LA) using nanoemulsion systems. The combination of these bio-active compounds was used to design oil in water (O/W) and water in oil (W/O) emulsions. The resulted emulsions were characterized by particle size measurements. The phenolic content of each nanoemulsion was examined by using both colorimetric assay and chromatographic analyses. Two different methods containing cell free chemical assay (1-diphenyl-2-picrylhydrazyl method) and cell based antioxidant activity test were used to evaluate the antioxidant capacities. In order to investigate the bio-activities of the herbal formulations, in vitro cell culture experiments, including cytotoxicity, scratch assay, antioxidant activity and cell proliferation were carried out using Vero cell line as a model cell line. Furthermore, to monitor localization of the nanoemulsions after application of the cell culture, the cell images were monitored via fluorescence microscope after FITC labeling. All data confirmed that the enriched N. sativa formulations exhibited better antioxidant and wound healing activity than N. sativa emulsion without any enrichment. In conclusion, the incorporation of AuNP-LA and C. officinalis extract into the N. sativa emulsions significantly increased the bio-activities. The present work may support further studies about using the other bio-active agents for the enrichment of herbal preparations to strengthen their activities.

  3. Bio-active nanoemulsions enriched with gold nanoparticle, marigold extracts and lipoic acid: In vitro investigations.

    PubMed

    Guler, Emine; Barlas, F Baris; Yavuz, Murat; Demir, Bilal; Gumus, Z Pinar; Baspinar, Yucel; Coskunol, Hakan; Timur, Suna

    2014-09-01

    A novel and efficient approach for the preparation of enriched herbal formulations was described and their potential applications including wound healing and antioxidant activity (cell based and cell free) were investigated via in vitro cell culture studies. Nigella sativa oil was enriched with Calendula officinalis extract and lipoic acid capped gold nanoparticles (AuNP-LA) using nanoemulsion systems. The combination of these bio-active compounds was used to design oil in water (O/W) and water in oil (W/O) emulsions. The resulted emulsions were characterized by particle size measurements. The phenolic content of each nanoemulsion was examined by using both colorimetric assay and chromatographic analyses. Two different methods containing cell free chemical assay (1-diphenyl-2-picrylhydrazyl method) and cell based antioxidant activity test were used to evaluate the antioxidant capacities. In order to investigate the bio-activities of the herbal formulations, in vitro cell culture experiments, including cytotoxicity, scratch assay, antioxidant activity and cell proliferation were carried out using Vero cell line as a model cell line. Furthermore, to monitor localization of the nanoemulsions after application of the cell culture, the cell images were monitored via fluorescence microscope after FITC labeling. All data confirmed that the enriched N. sativa formulations exhibited better antioxidant and wound healing activity than N. sativa emulsion without any enrichment. In conclusion, the incorporation of AuNP-LA and C. officinalis extract into the N. sativa emulsions significantly increased the bio-activities. The present work may support further studies about using the other bio-active agents for the enrichment of herbal preparations to strengthen their activities. PMID:25009101

  4. Improved molecular fingerprint analysis employing multi-branched gold nanoparticles in conjunction with surface-enhanced Raman scattering

    PubMed Central

    Johnston, Jencilin; Taylor, Erik N; Gilbert, Richard J; Webster, Thomas J

    2016-01-01

    Vibrational spectroscopy is a powerful analytical tool that assesses molecular properties based on spectroscopic signatures. In this study, the effect of gold nanoparticle morphology (spherical vs multi-branched) was assessed for the characterization of a Raman signal (ie, molecular fingerprint) that may be helpful for numerous medical applications. Multi-branched gold nanoparticles (MBAuNPs) were fabricated using a green chemistry method which employed the reduction of gold ion solute by 2-[4-(2-hydroxyethyl)-1-piperazyl] ethane sulfonic acid. Two types of reporter dyes, indocyanine (IR820 and IR792) and carbocyanine (DTTC [3,3′-diethylthiatricarbocyanine iodide] and DTDC [3,3′-diethylthiadicarbocyanine iodide]), were functionalized to the surface of the MBAuNPs and stabilized with denatured bovine serum albumin, thus forming the surface-enhanced Raman spectroscopy tag. Fluorescein isothiocyanate-conjugated anti-epidermal growth factor receptor to the surface-enhanced Raman spectroscopy tags and the properties of the resulting conjugates were assessed through determination of the Raman signal. Using the MBAuNP Raman probes synthesized in this manner, we demonstrated that MBAuNP provided significantly more surface-enhanced Raman scattering signal when compared with the associated spherical gold nanoparticle of similar size and concentration. MBAuNP enhancements were retained in the surface-enhanced Raman spectroscopy tags complexed to anti-epidermal growth factor receptor, providing evidence that this could be a useful biological probe for enhanced Raman molecular fingerprinting. Furthermore, while utilizing IR820 as a novel reporter dye linked with MBAuNP, superior Raman signal fingerprint results were obtained. Such results provide significant promise for the use of MBAuNP in the detection of numerous diseases for which biologically specific surface markers exist. PMID:26730189

  5. Improved molecular fingerprint analysis employing multi-branched gold nanoparticles in conjunction with surface-enhanced Raman scattering.

    PubMed

    Johnston, Jencilin; Taylor, Erik N; Gilbert, Richard J; Webster, Thomas J

    2016-01-01

    Vibrational spectroscopy is a powerful analytical tool that assesses molecular properties based on spectroscopic signatures. In this study, the effect of gold nanoparticle morphology (spherical vs multi-branched) was assessed for the characterization of a Raman signal (ie, molecular fingerprint) that may be helpful for numerous medical applications. Multi-branched gold nanoparticles (MBAuNPs) were fabricated using a green chemistry method which employed the reduction of gold ion solute by 2-[4-(2-hydroxyethyl)-1-piperazyl] ethane sulfonic acid. Two types of reporter dyes, indocyanine (IR820 and IR792) and carbocyanine (DTTC [3,3'-diethylthiatricarbocyanine iodide] and DTDC [3,3'-diethylthiadicarbocyanine iodide]), were functionalized to the surface of the MBAuNPs and stabilized with denatured bovine serum albumin, thus forming the surface-enhanced Raman spectroscopy tag. Fluorescein isothiocyanate-conjugated anti-epidermal growth factor receptor to the surface-enhanced Raman spectroscopy tags and the properties of the resulting conjugates were assessed through determination of the Raman signal. Using the MBAuNP Raman probes synthesized in this manner, we demonstrated that MBAuNP provided significantly more surface-enhanced Raman scattering signal when compared with the associated spherical gold nanoparticle of similar size and concentration. MBAuNP enhancements were retained in the surface-enhanced Raman spectroscopy tags complexed to anti-epidermal growth factor receptor, providing evidence that this could be a useful biological probe for enhanced Raman molecular fingerprinting. Furthermore, while utilizing IR820 as a novel reporter dye linked with MBAuNP, superior Raman signal fingerprint results were obtained. Such results provide significant promise for the use of MBAuNP in the detection of numerous diseases for which biologically specific surface markers exist.

  6. Size dependence of gold nanorod stability: the need for customized surface chemistry

    NASA Astrophysics Data System (ADS)

    SoRelle, Elliott; Liba, Orly; Hussain, Zeshan; Gambhir, Milan; de la Zerda, Adam

    2015-03-01

    Nanoparticles can be synthesized in a wide array of shapes and sizes to suit specific biomedical applications in therapy and imaging. Prerequisite to such applications are particle stability in biological environments, non-toxicity, and facile conjugation of the particle surface with targeting biological moieties (such as antibodies). Here we report significant flaws in the common methods used to functionalize the surface of gold nanorods (GNRs) of larger-than-usual sizes. We find that while GNRs of sizes smaller than 50 x 15 nm can be effectively stabilized by polyethylene glycol (PEG)-based methods, larger GNRs form major aggregates and crash under similar functionalization conditions. Large GNRs may provide enhanced imaging sensitivity in biological applications due to greater optical extinction cross sections, provided that the GNRs can be made biostable. In this study, GNRs of sizes up to 90 x 30 nm were synthesized using two different published methods. Particle morphology and size distributions were characterized using Transmission Electron Microscopy (TEM), and optical spectra were measured by Vis-NIR Spectrometry. The colloidal stability of different-sized GNRs was assayed at various stages of functionalization using zeta potential and Vis-NIR measurements. The results of these experiments indicate that large GNRs functionalized with PEG undergo irreversible aggregation after minimal washing. We find that coating large GNRs with polystyrene sulfonate (PSS) instead of PEG vastly improves GNR stability in water and serum. Moreover, we provide a novel platform for conjugating biomolecules of interest to PSS-coated large GNRs. We show that larger GNRs produce stronger photoacoustic signal than commonly used smaller GNRs, indicating an advantage of using large GNRs for biomedical imaging. Our observations underscore that the biomedical advantages of novel nanoparticle synthesis methods may not be realized without tailored surface functionalization methods. More

  7. Electrically Responsive Surfaces: Experimental and Theoretical Investigations

    PubMed Central

    2016-01-01

    Conspectus Stimuli-responsive surfaces have sparked considerable interest in recent years, especially in view of their biomimetic nature and widespread biomedical applications. Significant efforts are continuously being directed at developing functional surfaces exhibiting specific property changes triggered by variations in electrical potential, temperature, pH and concentration, irradiation with light, or exposure to a magnetic field. In this respect, electrical stimulus offers several attractive features, including a high level of spatial and temporal controllability, rapid and reverse inducement, and noninvasiveness. In this Account, we discuss how surfaces can be designed and methodologies developed to produce electrically switchable systems, based on research by our groups. We aim to provide fundamental mechanistic and structural features of these dynamic systems, while highlighting their capabilities and potential applications. We begin by briefly describing the current state-of-the-art in integrating electroactive species on surfaces to control the immobilization of diverse biological entities. This premise leads us to portray our electrically switchable surfaces, capable of controlling nonspecific and specific biological interactions by exploiting molecular motions of surface-bound electroswitchable molecules. We demonstrate that our self-assembled monolayer-based electrically switchable surfaces can modulate the interactions of surfaces with proteins, mammalian and bacterial cells. We emphasize how these systems are ubiquitous in both switching biomolecular interactions in highly complex biological conditions while still offering antifouling properties. We also introduce how novel characterization techniques, such as surface sensitive vibrational sum-frequency generation (SFG) spectroscopy, can be used for probing the electrically switchable molecular surfaces in situ. SFG spectroscopy is a technique that not only allowed determining the structural

  8. Surface properties of substituted-benzenethiol monolayers on gold and silver: Work function, wettability, and surface tension

    NASA Astrophysics Data System (ADS)

    Tatara, Shingo; Kuzumoto, Yasutaka; Kitamura, Masatoshi

    2016-03-01

    The surface properties, including work function and wettability, of Au and Ag surfaces modified with various substituted benzenethiols have been investigated. Whereas the work functions of the modified Au surfaces ranged from 4.42 to 5.48 eV, those of the modified Ag surfaces ranged from 3.99 to 5.77 eV. The highest work function of 5.77 eV was obtained on the Ag surface modified with pentafluorobenzenethiol, and the lowest work function of 3.99 eV was obtained on the Ag surface modified with 4-methylbenzenethiol. The water contact angle on modified Au surfaces was found to be in a wide range from 30.9 to 88.3°. The water contact angle on the Au surface modified with a substituted benzenethiol was close to that on the Ag surface modified with the same benzenethiol. Furthermore, the tension of the modified Au surfaces was estimated from their contact angles of water and ethylene glycol.

  9. Measurement and scaling of air-surface mercury exchange from substrates in the vicinity of two Nevada gold mines.

    PubMed

    Miller, Matthieu B; Gustin, Mae S; Eckley, Chris S

    2011-09-01

    The state of Nevada has extensive mineral resources, and is the largest producer of gold in the USA as well as fourth in world gold production. Mercury (Hg) is often present in the hydrothermal systems that produce gold deposits, and can be found in elevated concentrations in gold ore. As a result, mining of gold ore in Nevada has been shown to release Hg to the atmosphere from point and non-point sources. This project focused on measurement of air-soil Hg exchange associated with undisturbed soils and bedrock outcrops in the vicinity of two large gold mines. Field and laboratory data collected were used to identify the important variables controlling Hg flux from these surfaces, and to estimate a net flux from the areas adjacent to the active mines as well as that occurring from the mined area pre-disturbance. Mean daily flux by substrate type ranged from 9 ng m(-2) day(-1) to 140 ng m(-2) day(-1). Periods of net deposition of elemental Hg were observed when air masses originating from a mine site moved over sampling locations. Based on these observations and measured soil Hg concentrations we suggest that emissions from point and non-point sources at the mines are a source of Hg to the surrounding substrates with the amount deposited not being of an environmental concern but of interest mainly with respect to the cycling of atmospheric elemental Hg. Observations indicate that while some component of the deposited Hg is sequestered in the soil, this Hg is gradually released back to the atmosphere over time. Estimated pre-disturbance emissions from the current mine footprints based on field data were 0.1 and 1.7 kg yr(-1), compared to that estimated for the current non-point mining sources of 19 and 109 kg yr(-1), respectively.

  10. The effect of pressure on the surface plasmon absorption spectra of colloidal gold and silver particles

    SciTech Connect

    Coffer, J.L.; Shapley, J.R.; Drickamer, H.G. )

    1990-05-09

    The first measurements of the effect of pressure on the peak position ({omega}{sub sp}) and line width (fwhm) of the surface plasmon absorption in several Au and Ag hydrosols have been recorded up to 10 kbar. Red shifts of the plasmon peak with increasing pressure are observed for relatively large metal particles prepared by the citrate procedure (Au, {anti d} = 265 {angstrom}; Ag, {anti d} = 230 {angstrom}). The shift for silver is over twice that of gold ({minus}420 cm{sup {minus}1} vs {minus} 200 cm{sup {minus}1}). These red shifts are interpreted in terms of pressure-induced volume changes within the context of a free-electron model. In contrast, particles prepared by the Faraday method (Au, {anti d} = 54 {angstrom}; Ag, d{anti d} = 60 {angstrom}) show initial blue shifts with pressure, with the magnitude again larger for silver. Upon aging (as well as upon heating in the case of Au), the Au and Ag Faraday sols exhibit an increase in their average particle size and degree of aggregation. Correspondingly, the pressure response of their plasmon absorption approaches that of the citrate sols.

  11. Reversible Control in Surface Plasmon Resonance Wavelength of Gold Nanoparticles by Using Polydimethylsiloxane (PDMS)

    NASA Astrophysics Data System (ADS)

    Tsutsui, Yushi; Fudouzi, Hiroshi; Hayakawa, Tomokatsu; Nogami, Masayuki

    2011-10-01

    In this paper, we demonstrate reversible control in surface plasomon resonance (SPR) wavelength of gold nanoparticles (GNPs) by changing their interparticle distance, which is dependent on the length of alkyl chain of alkanethiol adsorbed on GNPs and the swelling effect of polydimethylsiloxane (PDMS) used as a host material. A SPR wavelength was first positioned at a given wavelength dependent on the length of alkanethiol when GNPs were immobilized in PDMS. It was found that SPR wavelength red-shifted when the length of the carbon chain was shortened. On the other hand, when silicone oil was transfused to PDMS, SPR wavelength was blue-shifted by the swelling effect (volume expansion) of PDMS. And once silicone oil was volatilized, the particles returned to the original position and SPR did as well. Additionally, the coefficient of expansion of PDMS could be changed by changing the kind of silicon oils. From these results, it could be concluded that the SPR control due to their interparticle distance of GNPs was reversible and the varying degree of swelling of PDMS led to good controllability of SPR in a wide range of wavelength.

  12. Theoretical study of surface plasmon resonances in hollow gold-silver double-shell nanostructures.

    PubMed

    Román-Velázquez, Carlos E; Noguez, Cecilia; Zhang, Jin Z

    2009-04-23

    A theoretical model has been developed to study the optical properties of metallic multishell structures on the nanometer scale. The Mie theory was generalized for multiconcentric spherical shell nanostructures and employed to determine the effects and importance of the different parameters of the system such as thickness, size, and other material properties, for instance, the medium index of refraction. A unique hollow gold-silver double-shell structure is used as an example to test the model developed with recent experiments. The surface plasmon resonance (SPR) absorption spectrum of this structure has been calculated as a function of various parameters, including shell thickness and diameter. Using parameters similar to those previously reported experimentally, very good agreement has been found between calculated and experimentally measured SPR spectra, which validates the model. The results provide new insights into the fundamental properties of complex metal nanostructures that give us the ability to control the optical response, which has important implications in the synthesis of new metal nanostructures as well as their application in emerging technologies. PMID:19226130

  13. Synthesis of gold nanoparticles on the surface of pyrolytic graphite using penicillin as a stabilizing reagent and the catalytic oxidation of α-naphthylamine

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Song, Y.; Cheng, Z. P.; Zhou, J. F.; Wei, C.

    2013-01-01

    Electrochemical synthesis of gold nanoparticles on the surface of pyrolytic graphite using penicillin as a stabilizing reagent was proposed. The gold nanoparticles were characterized by scanning electron microscopy, cyclic voltammetry, IR spectra, UV spectra, and powder X-ray diffraction spectra. The electro-chemical catalysis of penicillin for α-naphthylamine was demonstrated.

  14. Facile preparation of gold nanocages and hollow gold nanospheres via solvent thermal treatment and their surface plasmon resonance and photothermal properties.

    PubMed

    Wang, Haifei; Han, Jing; Lu, Wensheng; Zhang, Jianping; Li, Jinru; Jiang, Long

    2015-02-15

    Although template etching method is one of the most common ways of preparation of hollow gold nanostructures, this approach still requires further improvements to avoid the collapse of gold shells after the cores were removed. In this work, an improved template etching method, with which hollow gold nanostructure is fabricated by etching Polystyrene (PS) cores from PS@Au core-shell nanospheres with solvent thermal treatment in N,N-Dimethylformamide (DMF), is demonstrated. When PS cores were removed by a thermal treatment process, gold nanoshells reconstruct and the collapse of the nanoshells is avoided. Gold nanocages and hollow gold nanospheres are easily obtained from the various structures of PS@Au core-shell nanospheres. These hollow nanostructures represent special near infrared (NIR) optical property and photothermal property. Compared with hollow gold nanospheres, the gold nanocages show higher temperature increase at the same particle concentration.

  15. Facile preparation of gold nanocages and hollow gold nanospheres via solvent thermal treatment and their surface plasmon resonance and photothermal properties.

    PubMed

    Wang, Haifei; Han, Jing; Lu, Wensheng; Zhang, Jianping; Li, Jinru; Jiang, Long

    2015-02-15

    Although template etching method is one of the most common ways of preparation of hollow gold nanostructures, this approach still requires further improvements to avoid the collapse of gold shells after the cores were removed. In this work, an improved template etching method, with which hollow gold nanostructure is fabricated by etching Polystyrene (PS) cores from PS@Au core-shell nanospheres with solvent thermal treatment in N,N-Dimethylformamide (DMF), is demonstrated. When PS cores were removed by a thermal treatment process, gold nanoshells reconstruct and the collapse of the nanoshells is avoided. Gold nanocages and hollow gold nanospheres are easily obtained from the various structures of PS@Au core-shell nanospheres. These hollow nanostructures represent special near infrared (NIR) optical property and photothermal property. Compared with hollow gold nanospheres, the gold nanocages show higher temperature increase at the same particle concentration. PMID:25460711

  16. A novel electrochemical sensor surface for the detection of hydrogen peroxide using cyclic bisureas/gold nanoparticle composite.

    PubMed

    Mathew, Manjusha; Sandhyarani, N

    2011-10-15

    A novel electrochemical sensor surface with enhanced sensitivity for the detection of hydrogen peroxide has been developed based on the layer-by-layer assembly of mercapto propionic acid (MPA), cystine-based polymethylene-bridged cyclic bisureas (CBU)/gold nanoparticle (AuNP) and horseradish peroxidase (HRP) on gold electrode. Possibility of a large number of hydrogen bonds, allowed by the chemical and sterical structure of the CBU ensures the proper immobilization of the enzyme in favorable orientation and retention of enzymatic activity. Efficient electron tunneling property of AuNP together with its electrocatalytic activity leads to higher sensitivity in the detection of H(2)O(2). In cyclic voltammetry measurements a cathodic current due to direct electron transfer of HRP is observed which, indicates excellent electrocatalytic activity of the sensor surface. The biosensor surface modified with gold nanoparticle and CBU showed a lower detection limit of 50 nM for hydrogen peroxide. Chronoamperometry is performed at -0.3 V and Michaelis-Menten constant K(M)(app) value is estimated to be 4.5 μM. The newly developed sensor surface showed very high stability, reproducibility and high sensitivity.

  17. Gold Cluster Diffusion Kinetics on Stoichiometric and Reduced Surfaces of Rutile TiO 2 (110)

    SciTech Connect

    Goldman, Nir; Browning, Nigel D.

    2011-06-16

    Gold clusters on rutile TiO2 are known to serve as efficient oxidation catalysts for pollutants and environmental contaminants. However, the mechanism by which highly mobile small clusters migrate and aggregate into larger species relevant to gold’s catalytic activity remains unresolved. We report herein on ab initio simulations of the diffusion of atomic gold clusters up to the trimer on rutile TiO2(110) surfaces. We show that, on the stoichiometric surface, both the dimer and the trimer can exhibit relatively low surface mobility due to high energetic barriers for diffusion out of their energetic minima coupled with low barriers for the reverse motion. On the reduced surface, these clusters can diffuse relatively quickly between energetic minima within the oxygen vacancy site due to the large degree of vibrational entropy in their transition states. Our computed diffusion times provide a point of comparison for future experiments and will aid in development of models of gold cluster island sintering.

  18. Microwave-Accelerated Surface Modification of Plasmonic Gold Thin Films with Self-Assembled Monolayers of Alkanethiols

    PubMed Central

    Grell, Tsehai A.J.; Alabanza, Anginelle M.; Gaskell, Karen; Aslan, Kadir

    2013-01-01

    A rapid surface modification technique for the formation of self-assembled monolayers (SAMs) of alkanethiols on gold thin films using microwave heating in less than 10 min is reported. In this regard, SAMs of two model alkanethiols, 11-mercaptoundecanoic acid (11-MUDA, to generate a hydrophilic surface) and undecanethiol (UDET, a hydrophobic surface), were successfully formed on gold thin films using selective microwave heating in 1) a semi-continuous and 2) a continuous fashion and at room temperature (24 hours, control experiment, no microwave heating). The formation of SAMs of 11-MUDA and UDET were confirmed by contact angle measurements, Fourier–transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The contact angles for water on SAMs formed by the selective microwave heating and conventional room temperature incubation technique (24 hours) were measured to be similar for 11-MUDA and UDET. FT-IR spectroscopy results confirmed that the internal structure of SAMs prepared using both microwave heating and at room temperature were similar. XPS results revealed that the organic and sulfate contaminants found on bare gold thin films were replaced by SAMs after the surface modification process was carried out using both microwave heating and at room temperature. PMID:24083414

  19. Liquid Surface X-ray Studies of Gold Nanoparticle-Phospholipid Films at the Air/Water Interface.

    PubMed

    You, Siheng Sean; Heffern, Charles T R; Dai, Yeling; Meron, Mati; Henderson, J Michael; Bu, Wei; Xie, Wenyi; Lee, Ka Yee C; Lin, Binhua

    2016-09-01

    Amphiphilic phospholipids and nanoparticles functionalized with hydrophobic capping ligands have been extensively investigated for their capacity to self-assemble into Langmuir monolayers at the air/water interface. However, understanding of composite films consisting of both nanoparticles and phospholipids, and by extension, the complex interactions arising between nanomaterials and biological membranes, remains limited. In this work, dodecanethiol-capped gold nanoparticles (Au-NPs) with an average core diameter of 6 nm were incorporated into 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) monolayers with surface densities ranging from 0.1 to 20% area coverage at a surface pressure of 30 mN/m. High resolution liquid surface X-ray scattering studies revealed a phase separation of the DPPC and Au-NP components of the composite film, as confirmed with atomic force microscopy after the film was transferred to a substrate. At low Au-NP content, the structural organization of the phase-separated film is best described as a DPPC film containing isolated islands of Au-NPs. However, increasing the Au-NP content beyond 5% area coverage transforms the structural organization of the composite film to a long-range interconnected network of Au-NP strands surrounding small seas of DPPC, where the density of the Au-NP network increases with increasing Au-NP content. The observed phase separation and structural organization of the phospholipid and nanoparticle components in these Langmuir monolayers are useful for understanding interactions of nanoparticles with biological membranes. PMID:27459364

  20. Localized pulsed laser interaction with submicronic gold particles embedded in silica: a method for investigating laser damage initiation

    NASA Astrophysics Data System (ADS)

    Natoli, Jean-Yves; Gallais, Laurent; Bertussi, Bertrand; During, Annelise; Commandre, Mireille; Rullier, Jean-Luc; Bonneau, Florian; Combis, Patrick

    2003-04-01

    Laser damage phenomena in fused silica are currently under study because of numerous related high power laser applications. Nanosized defects are believed to be responsible for some laser damage initiation. In order to predict and to quantify this initiation process, engineered submicronic gold defects were embedded in silica. The study of these samples by localized pulsed irradiation of isolated gold particles coupled with Nomarski, atomic force and photothermal microscope observations permits us to discriminate between two distinct stages of material modification: one detectable at the surface and the second in the neighbourhood of the embedded particle. Comparison between the observations and simulations results in good agreement if we assume that inclusion melting initiates the damage.

  1. Biopolymer coated gold nanocrystals prepared using the green chemistry approach and their shape-dependent catalytic and surface-enhanced Raman scattering properties.

    PubMed

    Chou, Chih-Wei; Hsieh, Hui-Hsuan; Hseu, You-Cheng; Chen, Ko-Shao; Wang, Gou-Jen; Chang, Hsien-Chang; Pan, Yong-Li; Wei, Yi-Syuan; Chang, Ko Hsin; Harn, Yeu-Wei

    2013-07-21

    This study deals with the preparation of multi-shaped nanoscale gold crystals under synthetically simple, green, and efficient conditions using a seed-mediated growth approach in the presence of hyaluronic acid (HA). These highly biocompatible multi-shaped gold nanocrystals were examined to evaluate their catalytic and surface enhanced Raman scattering (SERS) properties. The results show that the size and shape of the nanocrystals are mainly correlated to the amount of seed, seed size, HA concentration, and reaction temperature. Gold seeds accelerate the reduction of the gold precursor to form gold nanocrystals using HA. The HA serves as a reducing agent and a growth template for the reduction of Au(III) and nanocrystal stabilization. The multi-shaped gold nanocrystals showed superior catalytic properties and higher SERS performance. The simple, green approach efficiently controls the nanocrystals and creates many opportunities for future applications. PMID:23728083

  2. Biopolymer coated gold nanocrystals prepared using the green chemistry approach and their shape-dependent catalytic and surface-enhanced Raman scattering properties.

    PubMed

    Chou, Chih-Wei; Hsieh, Hui-Hsuan; Hseu, You-Cheng; Chen, Ko-Shao; Wang, Gou-Jen; Chang, Hsien-Chang; Pan, Yong-Li; Wei, Yi-Syuan; Chang, Ko Hsin; Harn, Yeu-Wei

    2013-07-21

    This study deals with the preparation of multi-shaped nanoscale gold crystals under synthetically simple, green, and efficient conditions using a seed-mediated growth approach in the presence of hyaluronic acid (HA). These highly biocompatible multi-shaped gold nanocrystals were examined to evaluate their catalytic and surface enhanced Raman scattering (SERS) properties. The results show that the size and shape of the nanocrystals are mainly correlated to the amount of seed, seed size, HA concentration, and reaction temperature. Gold seeds accelerate the reduction of the gold precursor to form gold nanocrystals using HA. The HA serves as a reducing agent and a growth template for the reduction of Au(III) and nanocrystal stabilization. The multi-shaped gold nanocrystals showed superior catalytic properties and higher SERS performance. The simple, green approach efficiently controls the nanocrystals and creates many opportunities for future applications.

  3. On the mechanism of carbon monoxide oxidation on the surface of gold nanoclusters supported on titanium oxide

    NASA Astrophysics Data System (ADS)

    Tvauri, I. V.; Remar, D. F.; Turiev, A. M.; Tsidaeva, N. I.; Fukutani, K.; Magkoev, T. T.

    2010-05-01

    The process of carbon monoxide (CO) oxidation on the surface of a system comprising nanodimensional gold clusters deposited onto thin films of titanium oxide of variable stoichiometry formed on a Re(1000) single crystal surface has been studied by methods of thermodesorption, IR, and X-ray photoelectron spectroscopy. It is established that oxygen contained in titanium oxide plays an important role in the conversion of CO into CO2. The efficiency of this process on the Au/TiO x ( x < 2) system surface is significantly higher that that on the Au/TiO2 system.

  4. Characterization of gas-expanded liquid-deposited gold nanoparticle films on substrates of varying surface energy.

    PubMed

    Hurst, Kendall M; Roberts, Christopher B; Ashurst, W Robert

    2011-01-18

    Dodecanethiol-stabilized gold nanoparticles (AuNPs) were deposited via a gas-expanded liquid (GXL) technique utilizing CO(2)-expanded hexane onto substrates of different surface energy. The different surface energies were achieved by coating silicon (100) substrates with various organic self-assembled monolayers (SAMs). Following the deposition of AuNP films, the films were characterized to determine the effect of substrate surface energy on nanoparticle film deposition and growth. Interestingly, the critical surface tension of a given substrate does not directly describe nanoparticle film morphology. However, the results in this study indicate a shift between layer-by-layer and island film growth based on the critical surface tension of the capping ligand. Additionally, the fraction of surface area covered by the AuNP film decreases as the oleophobic nature of the surfaces increases. On the basis of this information, the potential exists to engineer nanoparticle films with desired morphologies and characteristics. PMID:21174390

  5. Characterization of gas-expanded liquid-deposited gold nanoparticle films on substrates of varying surface energy.

    PubMed

    Hurst, Kendall M; Roberts, Christopher B; Ashurst, W Robert

    2011-01-18

    Dodecanethiol-stabilized gold nanoparticles (AuNPs) were deposited via a gas-expanded liquid (GXL) technique utilizing CO(2)-expanded hexane onto substrates of different surface energy. The different surface energies were achieved by coating silicon (100) substrates with various organic self-assembled monolayers (SAMs). Following the deposition of AuNP films, the films were characterized to determine the effect of substrate surface energy on nanoparticle film deposition and growth. Interestingly, the critical surface tension of a given substrate does not directly describe nanoparticle film morphology. However, the results in this study indicate a shift between layer-by-layer and island film growth based on the critical surface tension of the capping ligand. Additionally, the fraction of surface area covered by the AuNP film decreases as the oleophobic nature of the surfaces increases. On the basis of this information, the potential exists to engineer nanoparticle films with desired morphologies and characteristics.

  6. Ultra-sensitive immunosensor for detection of hepatitis B surface antigen using multi-functionalized gold nanoparticles.

    PubMed

    Shourian, M; Ghourchian, H; Boutorabi, M

    2015-10-01

    The signal amplification for analytical purposes has considerable potential in detecting trace levels of analytes for clinical, security or environmental applications. In the present report a strategy based on a sandwich type immunoassay system was designed for the detection of hepatitis B surface antigen which exploits the specific affinity interaction between streptavidin and biotin recognition systems. The method involves the specific coupling of multi-functionalized gold nanoparticles (bearing biotin and luminol molecules) to the streptavidin modified by secondary antibody. The chemiluminescent signal is produced by the gold nanoparticles in the presence of HAuCl4 as catalyst and hydrogen peroxide as oxidant. The immunosensor was able to detect hepatitis B surface antigen in the linear concentration range from 1.7 to 1920 pg mL(-1) and the detection limit of 0.358 pg mL(-1), at signal/noise = 3.

  7. Surface plasmon resonance imaging on a microchip for detection of DNA-modified gold nanoparticles deposited onto the surface in a non-cross-linking configuration.

    PubMed

    Sato, Yasunobu; Sato, Kae; Hosokawa, Kazuo; Maeda, Mizuo

    2006-08-01

    Recently we reported that gold nanoparticles (GNPs) with fully matched duplexes on their surfaces are selectively deposited onto walls of poly(dimethylsiloxane) (PDMS) microchannels at high salt concentrations. In this study, the surface plasmon resonance (SPR) imaging technique was applied to monitor this phenomenon for improvement of detection sensitivity and elucidation of the phenomenon. The microchip was fabricated by bonding a surface-patterned PDMS plate and a gold thin film-deposited glass substrate. Probe oligonucleotide-modified GNPs were hybridized with target oligonucleotides to make fully matched or single-base-mismatched duplexes. The hybridized GNP solution was mixed with an NaCl solution in a Y-shaped microchannel. The deposition of the GNPs onto the gold sensor surface was detected by SPR imaging. Discrimination of the targets was possible with limit of detection of 32 nM (19 fmol) without temperature control in 5 min. Detailed analysis indicated that a seed layer of GNPs was initially adsorbed onto the sensor surface regardless of the target sequence. Therefore, in combination with a portable SPR device, the proposed method is promising for point-of-care testing of single-nucleotide polymorphsims.

  8. Facile synthesis of gold coated copper(II) hydroxide pine-needle-like micro/nanostructures for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Long, Kailin; Du, Deyang; Luo, Xiaoguang; Zhao, Weiwei; Wu, Zhangting; Si, Lifang; Qiu, Teng

    2014-08-01

    This work reports a facile method to fabricate gold coated copper(II) hydroxide pine-needle-like micro/nanostructures for surface-enhanced Raman scattering (SERS) application. The effects of reaction parameters on the shape, size and surface morphology of the products are systematically investigated. The as-prepared 3D hierarchical structures have the advantage of a large surface area available for the formation of hot spots and the adsorption of target analytes, thus dramatically improving the Raman signals. The finite difference time domain calculations indicate that the pine-needle-like model pattern may demonstrate a high quality SERS property owing to the high density and abundant hot spot characteristic in closely spaced needle-like arms.

  9. Gold Nanoplate-Based 3D Hierarchical Microparticles: A Single Particle with High Surface-Enhanced Raman Scattering Enhancement.

    PubMed

    Ma, Ying; Yung, Lin-Yue Lanry

    2016-08-01

    Formation of intended nano- and microstructures with regular building blocks has attracted much attention because of their potential applications in the fields of optics, electronics, and catalysis. Herein, we report a novel strategy to spontaneously grow three-dimensional (3D) hierarchical cabbagelike microparticles (CLMPs) constructed by individual Au nanoplates. By reducing gold precursor to gold atoms, N-(3-amidino)-aniline (NAAN) itself was oxidized to form poly(N-(3-amidino)-aniline) (PNAAN), which specifically binds on Au(111) facet as a capping agent and which leads to the formation of gold nanoplates. Because of the incomplete coverage of Au(111) facet, new gold nanoplate growth sites were spontaneously generated from the crystal plane of existing Au nanoplates for the growth of other nanoplates. This process continued until the nanoplate density reached its maximum range, eventually resulting in CLMPs with well-controlled structures. This opens a new avenue to utilize the imperfection during nanoparticle (NP) growth for the construction of microstructures. The individual CLMP shows excellent surface-enhanced Raman scattering (SERS) performance with high enhancement factor (EF) and good reproducibility as it integrates the SERS enhancement effects of individual Au nanoplate and the nanogaps formed by the uniform and hierarchical structures. PMID:27452074

  10. Tuning the observability of surface plasmon in silica-gold raspberry shaped nanoparticles using cuprous oxide shell.

    PubMed

    Tyagi, Himanshu; Mohapatra, Jeotikanta; Kushwaha, Ajay; Aslam, Mohammed

    2013-12-11

    A raspberry shaped silica-gold nanoparticle system has been coated with a cuprous oxide shell using a simple wet chemical approach. The optical properties of such particles depend on thin dielectric shell material, and we calculate far-field scattering and extinction of cuprous oxide coated silica-gold composite. In accordance with our theoretical findings, for ultrasmall gold nanoparticles (AuNPs < 5 nm) attached over silica, the localized surface plasmon resonance (LSPR) peak is completely suppressed after Cu2O coating. The cloaking (nonobservability) of the LSPR peak in extinction spectra has been explained via calculation of contribution from absorbance (<10%) and scattering (>90%) in the composite nanostructure. For larger particles (>5 nm), the traditional red-shift of the plasmon peak (from 532 to 588 nm) is still significant due to the large dielectric constant (approx. 8.0 @ 600 nm) of cuprous oxide (Cu2O) coating. A complete and controlled suppression of LSPR in small sized gold nanoparticles due to high dielectric refractory oxide shell could play a significant role in plasmon derived applications.

  11. Coverage Dependent Charge Reduction of Cationic Gold Clusters on Surfaces Prepared Using Soft Landing of Mass-selected Ions

    SciTech Connect

    Johnson, Grant E.; Priest, Thomas A.; Laskin, Julia

    2012-11-29

    The ionic charge state of monodisperse cationic gold clusters on surfaces may be controlled by selecting the coverage of mass-selected ions soft landed onto a substrate. Polydisperse diphosphine-capped gold clusters were synthesized in solution by reduction of chloro(triphenylphosphine)gold(I) with borane tert-butylamine in the presence of 1,3-bis(diphenylphosphino)propane. The polydisperse gold clusters were introduced into the gas phase by electrospray ionization and mass selection was employed to select a multiply charged cationic cluster species (Au11L53+, m/z = 1409, L = 1,3-bis(diphenylphosphino)propane) which was delivered to the surfaces of four different self-assembled monolayers on gold (SAMs) at coverages of 1011 and 1012 clusters/mm2. Employing the spatial profiling capabilities of in-situ time-of-flight secondary ion mass spectrometry (TOF-SIMS) it is shown that, in addition to the chemical functionality of the monolayer (as demonstrated previously: ACS Nano, 2012, 6, 573) the coverage of cationic gold clusters on the surface may be used to control the distribution of ionic charge states of the soft-landed multiply charged clusters. In the case of a 1H,1H,2H,2H-perfluorodecanethiol SAM (FSAM) almost complete retention of charge by the deposited Au11L53+ clusters was observed at a lower coverage of 1011 clusters/mm2. In contrast, at a higher coverage of 1012 clusters/mm2, pronounced reduction of charge to Au11L52+ and Au11L5+ was observed on the FSAM. When soft landed onto 16- and 11-mercaptohexadecanoic acid surfaces on gold (16,11-COOH-SAMs), the mass-selected Au11L53+ clusters exhibited partial reduction of charge to Au11L52+ at lower coverage and additional reduction of charge to both Au11L52+ and Au11L5+ at higher coverage. The reduction of charge was found to be more pronounced on the surface of the shorter (thinner) C11 than the longer (thicker) C16-COOH-SAM. On the surface of the 1-dodecanethiol (HSAM) monolayer, the most abundant charge state

  12. Gold nanoparticle-catalyzed reduction in a model system: Quantitative determination of reactive heterogeneity of a supported nanoparticle surface

    SciTech Connect

    Nigra, Michael M.; Arslan, Ilke; Katz, Alexander

    2012-11-01

    Kinetic poisoning experiments employing organic ligands were conducted using a gold nanoparticle–catalyzed reaction consisting of the reduction of resazurin to resorufin. The kinetic contributions of three distinct types of sites along with the number density of each of these site types during reaction were determined. The calculated number densities of each of the three types of sites, hypothesized to be corners, edges, and terraces, correlates well with atomic-resolution micrographs of the supported gold nanoparticles, obtained using aberration-corrected transmission electron microscopy and with predictions based on geometric models of idealized gold nanoparticles. The most active sites comprising 1% of the surface atoms exhibit at least 30% of the total activity of the catalyst for resazurin reduction. The selective mechanical blocking of surface sites on nanoparticles, particularly undercoordinated sites, paves the way for novel approaches utilizing organic ligands to quantify the activity of different active sites and control catalysis on metal surfaces. This work was supported in part by the Laboratory Directed Research and Development program at the Pacific Northwest National Laboratory (PNNL). The aberration-corrected electron microscopy was performed in the William R. Wiley Environmental Molecular Sciences Laboratory, a U.S. Department of Energy (DOE) national scientific user facility located at PNNL and funded by BER. PNNL is operated by Battelle for the U.S. DOE under contract DE-AC05-76RL01830.

  13. High-resolution investigation of metal nanoparticle growth on an insulating surface

    NASA Astrophysics Data System (ADS)

    Mativetsky, Jeffrey M.; Fostner, Shawn; Burke, Sarah A.; Grutter, Peter

    2009-07-01

    The three-dimensional nanoparticle morphology and the nanoparticle-substrate relationship during the submonolayer growth of three metals (gold, tantalum, and palladium) on the alkali halide KBr (001) surface is investigated by combining in situ high-resolution noncontact atomic force microscopy and ex situ transmission electron microscopy approaches. Highly varied growth behavior between the metals is revealed. Gold produces nearly spherical multiply twinned nanoparticles at room temperature and an increasing number of epitaxial particles at elevated temperatures. In contrast, the tantalum grows as relatively flat fractal particles, despite the square symmetry of the substrate lattice, a condition which normally precludes fractal growth. The tantalum also exhibits a strong affinity for KBr surface steps, leading to one-dimensional chains of nanoparticles. The deposition of palladium results in the creation of protruding substrate distortions and monolayer-high rectangular KBr islands in addition to the growth of palladium nanoparticles. It is hypothesized that the unusual growth observed in the palladium-KBr system is caused by the interdiffusion of palladium under the KBr surface. The range of growth behavior in the three systems is described in terms of the surface and interface energies, yielding bounds on the metal/KBr interface energies.

  14. Fabrication, characterization, and optical properties of gold nanobowl submonolayer structures.

    PubMed

    Ye, Jian; Van Dorpe, Pol; Van Roy, Willem; Borghs, Gustaaf; Maes, Guido

    2009-02-01

    We report on a versatile method to fabricate hollow gold nanobowls and complex gold nanobowls (with a core) based on an ion milling and a vapor HF etching technique. Two different sized hollow gold nanobowls are fabricated by milling and etching submonolayers of gold nanoshells deposited on a substrate, and their sizes and morphologies are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Optical properties of hollow gold nanobowls with different sizes are investigated experimentally and theoretically, showing highly tunable plasmon resonance ranging from the visible to the near-infrared region. Additionally, finite difference time domain (FDTD) calculations show an enhanced localized electromagnetic field around hollow gold nanobowl structures, which indicates a potential application in surface-enhanced Raman scattering (SERS) spectroscopy for biomolecular detection. Finally, we demonstrate the fabrication of complex gold nanobowls with a gold nanoparticle core which offers the capability to create plasmon hybridized nanostructures. PMID:19125593

  15. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer

    NASA Astrophysics Data System (ADS)

    Wang, Can; Bao, Chenchen; Liang, Shujing; Fu, Hualin; Wang, Kan; Deng, Min; Liao, Qiande; Cui, Daxiang

    2014-05-01

    Herein, we reported for the first time that RGD-conjugated silica-coated gold nanorods on the surface of multiwalled carbon nanotubes were successfully used for targeted photoacoustic imaging of in vivo gastric cancer cells. A simple strategy was used to attach covalently silica-coated gold nanorods (sGNRs) onto the surface of multiwalled carbon nanotubes (MWNTs) to fabricate a hybrid nanostructure. The cross-linked reaction occurred through the combination of carboxyl groups on the MWNTs and the amino group on the surface of sGNRs modified with a silane coupling agent. RGD peptides were conjugated with the sGNR/MWNT nanostructure; resultant RGD-conjugated sGNR/MWNT probes were investigated for their influences on viability of MGC803 and GES-1 cells. The nude mice models loaded with gastric cancer cells were prepared, the RGD-conjugated sGNR/MWNT probes were injected into gastric cancer-bearing nude mice models via the tail vein, and the nude mice were observed by an optoacoustic imaging system. Results showed that RGD-conjugated sGNR/MWNT probes showed good water solubility and low cellular toxicity, could target in vivo gastric cancer cells, and obtained strong photoacoustic imaging in the nude model. RGD-conjugated sGNR/MWNT probes will own great potential in applications such as targeted photoacoustic imaging and photothermal therapy in the near future.

  16. RGD-conjugated silica-coated gold nanorods on the surface of carbon nanotubes for targeted photoacoustic imaging of gastric cancer

    PubMed Central

    2014-01-01

    Herein, we reported for the first time that RGD-conjugated silica-coated gold nanorods on the surface of multiwalled carbon nanotubes were successfully used for targeted photoacoustic imaging of in vivo gastric cancer cells. A simple strategy was used to attach covalently silica-coated gold nanorods (sGNRs) onto the surface of multiwalled carbon nanotubes (MWNTs) to fabricate a hybrid nanostructure. The cross-linked reaction occurred through the combination of carboxyl groups on the MWNTs and the amino group on the surface of sGNRs modified with a silane coupling agent. RGD peptides were conjugated with the sGNR/MWNT nanostructure; resultant RGD-conjugated sGNR/MWNT probes were investigated for their influences on viability of MGC803 and GES-1 cells. The nude mice models loaded with gastric cancer cells were prepared, the RGD-conjugated sGNR/MWNT probes were injected into gastric cancer-bearing nude mice models via the tail vein, and the nude mice were observed by an optoacoustic imaging system. Results showed that RGD-conjugated sGNR/MWNT probes showed good water solubility and low cellular toxicity, could target in vivo gastric cancer cells, and obtained strong photoacoustic imaging in the nude model. RGD-conjugated sGNR/MWNT probes will own great potential in applications such as targeted photoacoustic imaging and photothermal therapy in the near future. PMID:24948888

  17. A theoretical investigation of the influence of gold nanosphere size on the decay and energy transfer rates and efficiencies of quantum emitters

    NASA Astrophysics Data System (ADS)

    Marocico, Cristian A.; Zhang, Xia; Bradley, A. Louise

    2016-01-01

    We present in this contribution a comprehensive investigation of the effect of the size of gold nanospheres on the decay and energy transfer rates of quantum systems placed close to these nanospheres. These phenomena have been investigated before, theoretically and experimentally, but no comprehensive study of the influence of the nanoparticle size on important dependences of the decay and energy transfer rates, such as the dependence on the donor-acceptor spectral overlap and the relative positions of the donor, acceptor, and nanoparticle, exists. As such, different accounts of the energy transfer mechanism have been presented in the literature. We perform an investigation of the energy transfer mechanisms between emitters and gold nanospheres and between donor-acceptor pairs in the presence of the gold nanospheres using a Green's tensor formalism, experimentally verified in our lab. We find that the energy transfer rate to small nanospheres is greatly enhanced, leading to a strong quenching of the emission of the emitter. When the nanosphere size is increased, it acts as an antenna, increasing the emission of the emitter. We also investigate the emission wavelength and intrinsic quantum yield dependence of the energy transfer to the nanosphere. As evidenced from the literature, the energy transfer process between the quantum system and the nanosphere can have a complicated distance dependence, with a r-6 regime, characteristic of the Förster energy transfer mechanism, but also exhibiting other distance dependences. In the case of a donor-acceptor pair of quantum systems in the presence of a gold nanosphere, when the donor couples strongly to the nanosphere, acting as an enhanced dipole; the donor-acceptor energy transfer rate then follows a Förster trend, with an increased Förster radius. The coupling of the acceptor to the nanosphere has a different distance dependence. The angular dependence of the energy transfer efficiency between donor and acceptor

  18. A theoretical investigation of the influence of gold nanosphere size on the decay and energy transfer rates and efficiencies of quantum emitters.

    PubMed

    Marocico, Cristian A; Zhang, Xia; Bradley, A Louise

    2016-01-14

    We present in this contribution a comprehensive investigation of the effect of the size of gold nanospheres on the decay and energy transfer rates of quantum systems placed close to these nanospheres. These phenomena have been investigated before, theoretically and experimentally, but no comprehensive study of the influence of the nanoparticle size on important dependences of the decay and energy transfer rates, such as the dependence on the donor-acceptor spectral overlap and the relative positions of the donor, acceptor, and nanoparticle, exists. As such, different accounts of the energy transfer mechanism have been presented in the literature. We perform an investigation of the energy transfer mechanisms between emitters and gold nanospheres and between donor-acceptor pairs in the presence of the gold nanospheres using a Green's tensor formalism, experimentally verified in our lab. We find that the energy transfer rate to small nanospheres is greatly enhanced, leading to a strong quenching of the emission of the emitter. When the nanosphere size is increased, it acts as an antenna, increasing the emission of the emitter. We also investigate the emission wavelength and intrinsic quantum yield dependence of the energy transfer to the nanosphere. As evidenced from the literature, the energy transfer process between the quantum system and the nanosphere can have a complicated distance dependence, with a r(-6) regime, characteristic of the Förster energy transfer mechanism, but also exhibiting other distance dependences. In the case of a donor-acceptor pair of quantum systems in the presence of a gold nanosphere, when the donor couples strongly to the nanosphere, acting as an enhanced dipole; the donor-acceptor energy transfer rate then follows a Förster trend, with an increased Förster radius. The coupling of the acceptor to the nanosphere has a different distance dependence. The angular dependence of the energy transfer efficiency between donor and acceptor

  19. Fabrication and manipulation of solid-state SiO2 nano-gears on a gold surface

    NASA Astrophysics Data System (ADS)

    Deng, J.; Troadec, C.; Ample, F.; Joachim, C.

    2011-07-01

    A process is presented to fabricate solid-state nano-gears down to a 60 nm outer diameter with six teeth, where the 350 nm diameter ones already have 24 teeth. The small gears are free to move on a polycrystalline gold surface. The gears can be manipulated one by one, using an atomic force microscope (AFM) tip, to construct a train of gears where mechanical motion can be transmitted from one gear to another by mastering the surface friction. This is a first step on the way to bridge the fabrication gap between microfabricated and molecule gears.

  20. Fabrication and manipulation of solid-state SiO2 nano-gears on a gold surface.

    PubMed

    Deng, J; Troadec, C; Ample, F; Joachim, C

    2011-07-01

    A process is presented to fabricate solid-state nano-gears down to a 60 nm outer diameter with six teeth, where the 350 nm diameter ones already have 24 teeth. The small gears are free to move on a polycrystalline gold surface. The gears can be manipulated one by one, using an atomic force microscope (AFM) tip, to construct a train of gears where mechanical motion can be transmitted from one gear to another by mastering the surface friction. This is a first step on the way to bridge the fabrication gap between microfabricated and molecule gears.

  1. In situ SEM and ToF-SIMS analysis of IgG conjugated gold nanoparticles at aqueous surfaces

    SciTech Connect

    Yang, Li; Zhu, Zihua; Yu, Xiao-Ying; Rodek, Gene; Saraf, Laxmikant V.; Thevuthasan, Suntharampillai; Cowin, James P.

    2014-04-01

    In this study, we report new results of in situ study of 5 nm goat anti-mouse IgG gold nanoparticles in a novel portable vacuum compatible microfluidic device using scanning electron microscope (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The unique feature of the liquid flow cell is that the detection window is open to the vacuum allowing direct probing of the liquid surface. The flow cell is composed of a silicon nitride (SiN) membrane and polydimethylsiloxane (PDMS), and it is fully compatible with vacuum operations for surface analysis. The aperture can be drilled through the 100 nm SiN membrane using a focused ion beam. Characteristic signals of the conjugated gold nanoparticles were successfully observed through the aperture by both energy-dispersive X-ray spectroscopy (EDX) in SEM and ToF-SIMS. Comparison was also made among wet samples, dry samples, and liquid sample in the flow cell using SEM/EDX. Stronger gold signal can be observed in our novel portable device by SEM/EDX compared with the wet or dry samples, respectively. Our results indicate that analyses of the nanoparticle components are better made in their native liquid environment. This is made possible using our unique microfluidic flow cell.

  2. Phthalocyaninato complexes with peripheral alkylthio chains: disk-like adsorbate species for the vertical anchoring of ligands on gold surfaces

    PubMed Central

    Siemeling, Ulrich; Schirrmacher, Christian; Glebe, Ulrich; Bruhn, Clemens; Baio, Joe E.; Árnadóttir, Líney; Castner, David G.; Weidner, Tobias

    2011-01-01

    Thin metalorganic films were prepared on gold by self-assembly of thioether-functionalised phthalocyaninato complexes from solution. The phthalocyaninato ligands used contain eight peripheral, β-positioned, alkylthio substituents SR (1a: R = n-C8H17, 1b: R = n-C12H25), which serve as headgroups for surface binding and promote lateral assembly, while the disk-like phthalocyaninato core offers the scope for the attachment of axial ligands to the adsorbed molecules. This process was mimicked by coordination of pyridine (Py) to [Zn(1a)] and [Zn(1b)], respectively. The crystal structures of the products [Zn(1a)(Py)] and [Zn(1b)(Py)] were determined. The crystal structures of 4,5-bis(octylthio)phthalodinitrile and 4,5-bis(dodecylthio)phthalodinitrile were also determined. The films fabricated from [Mn(1a)Cl] and [Mn(1b)Cl] on gold were characterised by XPS, ToF-SIMS and NEXAFS spectroscopy, which revealed the presence of well-defined and homogeneous self-assembled monolayers (SAMs), whose constituents are bound to the substrate by thioether–gold linkages. The orientation of the macrocycles is predominantly parallel to the surface. Strong electronic interaction of the manganese(III) centre with the substrate leads to Cl loss upon adsorption and its reduction to MnII. PMID:21857743

  3. Development of gold induced surface plasmon enhanced CIGS absorption layer on polyimide substrate

    NASA Astrophysics Data System (ADS)

    Park, Seong-Un; Sharma, Rahul; Sim, Jae-Kwan; Baek, Byung Joon; Ahn, Haeng-Kwun; Kim, Jin Soo; Lee, Cheul-Ro

    2013-09-01

    Localized surface plasmon resonance (LSPR) with metal nanoparticles is the promising phenomenon to increase light absorption by trapping light in thin film solar cells. In this study we demonstrate a successful LSPR effect with gold (Au) nanoparticles onto the Cu(In,Ga)Se2 (CIGS) absorption layer. First, the CIGS absorber layers is fabricated onto the Mo coated polyimide (PI) substrate by using two stage process as DC sputtering of CIG thin film followed by the selenization at 400 °C. Finally, the Au nanoparticles are deposited onto the CIGS layer with increasing particles size from 4-15 nm by using sputter coater for 10-120 s. The X-ray diffraction (XRD) patterns confirm the formation of CIGS/Au nanocomposite structure with prominent peak shift of CIGS reflections and increasing intensity for Au phase. The CIGS/Au nanocomposite morphologies with Au particle size distribution uniformity and surface coverage is examined under ultra-high resolution field effect scanning electron microscope (UHR-FESEM). A peak at 176 cm-1 in Raman spectra, associated with the “A1” mode of lattice vibration for the attributed to the pure chalcopyrite structure. The secondary ion mass spectroscopy (SIMS) showed ∼200 nm depth converge of Au nanoparticles into the CIGS absorption layer. The optical properties as transmittance, reflectance and absorbance of CIGS/Au layers were found to expand in the infrared region and the LSPR effect is the most prominent for Au particles (5-7 nm) deposited for 60 s. The absorption coefficient and band gap measurement also confirms that the LSPR effect for 5-7 nm Au particles with band gap improvement from 1.31 to 1.52 eV for CIGS/Au layer as the defect density decreases due to the deposition of Au nanoparticles onto the CIGS layer. Such LSPR effect in CIGS/Au nanocomposite absorption layer will be a key parameter to further improve performance of the solar cell.

  4. Inkjet-printed gold nanoparticulate patterns for surface finish in electronic package

    NASA Astrophysics Data System (ADS)

    Jang, Seonhee; Cho, Hyejin; Kang, Seongkoo; Oh, Sungil; Kim, Donghoon

    2011-11-01

    Gold (Au) pads for surface finish in electronic package were developed by the inkjet printing method. The Au ink for printing was prepared by Au nanoparticles (NPs) coated with capping molecules of dodecylamine (C12H25NH2). The microstructures of the inkjet-printed Au films were characterized after sintering in various gas flows. The film sintered in air showed that bonding between NPs was not enough for further grain growth due to the incomplete decomposition of the capping layer. The film sintered under nitrogen (N2) had NPs existing on the surface and the bottom which did not participate in sintering. When the film was sintered under N2-bubbled through formic acid (FA/N2), a large portion of the pores were observed to make a holey pancake-like structure of the film. The microstructures of the inkjet-printed Au film became denser with grain growth when Au NPs were sintered under mixed gas flows of FA/N2 and N2. The resistivity of film was 4.79 μΩ cm, about twice the bulk value. Organic analysis showed that about 0.43% of residual organics was left in the film. Therefore, this Au film was chosen for solder ball shear test because the microstructure was denser compared to the films sintered under other gasses such as N2 or FA/N2 and less organic residue was found from organic analyses. Even though the film sintered under N2 showed the best electrical property (4.35 μΩ cm), it was not adopted in the shear test because NPs remaining on the bottom of the film could lead to the poor adhesion between the film and substrate and show low shear strength. The shear force was 8.04 newton (N) on average and the strength was 64 MPa. This shear strength is good enough to substitute the inkjet-printed Au nanoparticulate film for electroplating in electronic package.

  5. Investigations of redox-labeled silica and gold nanoparticles in solution and as films on electrodes

    NASA Astrophysics Data System (ADS)

    Beasley, Christopher A.

    Chapter One serves as a background for Au nanoparticles (AuNP) and silica nanoparticles (SiNP). A brief history of the synthesis and characterization of AuNPs will be followed by a discussion on the recent application of the particles in sensing and energy-related applications. The second portion of the chapter will be a discussion on the functionalization of SiNPs and their application in a variety of sensing systems. Chapter Two discusses the irreversible adsorption onto electrode surfaces of highly ionic, mixed-monolayer AuNPs containing an N,N,N-triethylammonium terminated thiol and an 6-(ferrocenylhexane) thiol. The AuNP films are entropically stabilized due to the multidentate nature of the particles and can be transferred to NP-free electrolyte solutions for further investigation. The most interesting aspect of the film is the ability to monitor ion and accompanying solvent transfer between the film and electrolyte solution despite the films being one to two monolayers thick. Comparisons will be drawn to ion transfer between two immiscible electrolyte solutions. Chapter Three will discuss the controlled growth of films of highly ionic, mixed monolayer AuNPs containing deprotonated mercaptoundecanoic acid and 6-(ferrocenylhexane) thiol. The controlled deposition of films of AuNPs without the addition of a metal ion to facilitate binding between particles provides a new route to controlling film thicknesses for applications in Surface Enhanced Raman Spectroscopy and energy storage. Electrochemical quartz crystal microbalance studies, impedance spectroscopy and theoretical modeling show that the large peak-to-peak separation for the ferrocene/ferrocenium couple in cyclic voltammograms arises solely from uncompensated resistance effects within the film, i.e., the rates of ion permeation. Chapter Four examines ferrocenated SiNPs as charge storage devices. Focus is initially on the surface functionalization. Spectroscopic characterizations are used to estimate the

  6. Controlling gold nanoparticle assemblies for efficient surface-enhanced Raman scattering and localized surface plasmon resonance sensors

    NASA Astrophysics Data System (ADS)

    Toderas, Felicia; Baia, Monica; Baia, Lucian; Astilean, Simion

    2007-06-01

    Gold nanoparticle assemblies with different particle densities were immobilized upon functionalized glass substrates and their morphology and optical properties are analysed with TEM and UV-vis absorption spectroscopy. The efficiency of self-assembled gold colloidal nanoparticles as SERS-active substrates at 633 nm excitation line is evaluated by employing p-aminothiophenol. The average enhancements in the range of 105-107 are consistent with signals being dominated by molecules adsorbed at junctions inside nanoparticle assemblies. We employ an annealing treatment to induce changes in the initial morphology of gold assemblies and produce sensitive LSPR substrate. The sensitivity of the as-prepared substrate to transduce changes of the surrounding medium refractive index is further assessed.

  7. Simple control of surface topography of gold nanoshells by a surfactant-less seeded-growth method.

    PubMed

    Topete, Antonio; Alatorre-Meda, Manuel; Villar-Álvarez, Eva M; Cambón, Adriana; Barbosa, Silvia; Taboada, Pablo; Mosquera, Víctor

    2014-07-23

    We report the synthesis of branched gold nanoshells (BGNS) through a seeded-growth surfactant-less method. This was achieved by decorating chitosan-Pluronic F127 stabilized poly(lactic-co-gycolic) acid nanoparticles (NPs) with Au seeds (NP-seed), using chitosan as an electrostatic self-assembling agent. Branched shells with different degrees of anisotropy and optical response were obtained by modulating the ratios of HAuCl4/K2CO3 growth solution, ascorbic acid (AA) and NP-seed precursor. Chitosan and AA were crucial in determining the BGNS size and structure, acting both as coreductants and structure directing growth agents. Preliminary cytotoxicity experiments point to the biocompatibility of the obtained BGNS, allowing their potential use in biomedical applications. In particular, these nanostructures with "hybrid" compositions, which combine the features of gold nanoshells and nanostars showed a better performance as surface enhanced Raman spectroscopy probes in detecting intracellular cell components than classical smoother nanoshells. PMID:24959918

  8. A novel bioelectrochemical interface based on in situ synthesis of gold nanostructures on electrode surfaces and surface activation by Meerwein's salt. A bioelectrochemical sensor for glucose determination.

    PubMed

    Nikolaev, Konstantin; Ermakov, Sergey; Ermolenko, Yuri; Averyaskina, Elena; Offenhäusser, Andreas; Mourzina, Yulia

    2015-10-01

    A novel effective bioelectrochemical sensor interface for enzyme biosensors is proposed. The method is based on in situ synthesis of gold nanostructures (5-15 nm) on the thin-film electrode surface using the oleylamine (OA) method, which provides a high-density, stable, electrode interface nanoarchitecture. New method to activate the surface of the OA-stabilized nanostructured electrochemical interface for further functionalization with biomolecules (glucose oxidase enzyme) using Meerwein's salt is proposed. Using this approach a new biosensor for glucose determination with improved analytical characteristics: wide working range of 0.06-18.5mM with a sensitivity of 22.6 ± 0.5 μAmM(-1)cm(-2), limit of detection 0.02 mM, high reproducibility, and long lifetime (60 d, 93%) was developed. The surface morphology of the electrodes was characterized by scanning electron microscopy (SEM). The electrochemical properties of the interface were studied by cyclic voltammetry and electrochemical impedance spectroscopy using a Fe(II/III) redox couple. The studies revealed an increase in the electroactive surface area and a decrease in the charge transfer resistance following surface activation with Meerwein's reagent. A remarkably enhanced stability and reproducibility of the sensor was achieved using in situ synthesis of gold nanostructures on the electrode surface, while surface activation with Meerwein's salt proved indispensable in achieving an efficient bioelectrochemical interface. PMID:25983284

  9. Hybridization behavior of mixed DNA/alkylthiol monolayers on gold: characterization by surface plasmon resonance and 32P radiometric assay.

    PubMed

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

    2006-05-15

    Nucleic acid assay from a complex biological milieu is attractive but currently difficult and far from routine. In this study, DNA hybridization from serum dilutions into mixed DNA/mercaptoundecanol (MCU) adlayers on gold was monitored by surface plasmon resonance (SPR). Immobilized DNA probe and hybridized target densities on these surfaces were quantified using 32P-radiometric assays as a function of MCU diluent exposure. SPR surface capture results correlated with radiometric analysis for hybridization performance, demonstrating a maximum DNA hybridization on DNA/MCU mixed adlayers. The maximum target surface capture produced by MCU addition to the DNA probe layer correlates with structural and conformational data on identical mixed DNA/MCU adlayers on gold derived from XPS, NEXAFS, and fluorescence intensity measurements reported in a related study (Lee, C.-Y.; Gong, P.; Harbers, G. M.; Grainger, D. W.; Castner, D. G.; Gamble, L. J. Anal. Chem. 2006, 78, 3316-3325.). MCU addition into the DNA adlayer on gold also improved surface resistance to both nonspecific DNA and serum protein adsorption. Target DNA hybridization from serum dilutions was monitored with SPR on the optimally mixed DNA/MCU adlayers. Both hybridization kinetics and efficiency were strongly affected by nonspecific protein adsorption from a complex milieu even at a minimal serum concentration (e.g., 1%). No target hybridization was detected in SPR assays from serum concentrations above 30%, indicating nonspecific protein adsorption interference of DNA capture and hybridization from complex milieu. Removal of nonsignal proteins from nucleic acid targets prior to assay represents a significant issue for direct sample-to-assay nucleic acid diagnostics from food, blood, tissue, PCR mixtures, and many other biologically complex sample formats. PMID:16689533

  10. Size-controlled synthesis of superparamagnetic iron oxide nanoparticles and their surface coating by gold for biomedical applications

    NASA Astrophysics Data System (ADS)

    Maleki, H.; Simchi, A.; Imani, M.; Costa, B. F. O.

    2012-11-01

    The size mono-dispersity, saturation magnetization, and surface chemistry of magnetic nanoparticles (NPs) are recognized as critical factors for efficient biomedical applications. Here, we performed modified water-in-oil inverse nano-emulsion procedure for preparation of stable colloidal superparamagnetic iron oxide NPs (SPIONs) with high saturation magnetization. To achieve mono-dispersed SPIONs, optimization process was probed on several important factors including molar ratio of iron salts [Fe3+ and Fe2+], the concentration of ammonium hydroxide as reducing agent, and molar ratio of water to surfactant. The biocompatibility of the obtained NPs, at various concentrations, was evaluated via MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay and the results showed that the NPs were non-toxic at concentrations <0.1 mg/mL. Surface functionalization was performed by conformal coating of the NPs with a thin shell of gold (˜4 nm) through chemical reduction of attached gold salts at the surface of the SPIONs. The Fe3O4 core/Au shell particles demonstrate strong plasmon resonance absorption and can be separated from solution using an external magnetic field. Experimental data from both physical and chemical determinations of the changes in particle size, surface plasmon resonance optical band, phase components, core-shell surface composition, and magnetic properties have confirmed the formation of the mono-dispersed core-shell nanostructure.

  11. Surface crystallographic dependence of voltammetric oxidation of polyhydric alcohols and related systems at monocrystalline gold-acidic aqueous interfaces

    NASA Astrophysics Data System (ADS)

    Hamelin, Antoinette; Ho, Yeunghaw; Chang, Si-Chung; Gao, Xiaoping; Weaver, Michael J.

    1992-02-01

    The voltammetric oxidation in aqueous 0.1 Molar perchloric acid of four polyhydric alcohols, ethylene glycol, glycerol, meso-erythritol, and d-mannitol, on seven oriented gold surfaces is reported with the objective of assessing the role of surface crystallographic orientation on the catalytic electrooxidation of such poly-functional reactants. The automatically well-ordered nature of these gold surfaces has been scrutinized by in-situ scanning tunneling microscopy. In particular, the Au(221) and (533) faces were selected since they provide stepped surfaces, 4(111)-(111) and 4(111)-(100), respectively. The results are compared with corresponding data for simple unifunctional reactants, specifically for formic acid oxidation and with results reported previously for carbon monoxide oxidation. In contrast to the last reaction, the electrooxidation rates for both the polyhydric alcoholic and formic acid are greatest on Au(111), with Au(110) displaying unusually low activity. While formic acid electrooxidation is insensitive to the presence of monoatomic surface steps, the polyhydric alcohols (especially mannitol) are substantially less reactive on AU(221) and (533) relative to Au(111).

  12. Communication: anti-icing characteristics of superhydrophobic surfaces investigated by quartz crystal microresonators.

    PubMed

    Lee, Moonchan; Yim, Changyong; Jeon, Sangmin

    2015-01-28

    We investigated the anti-icing characteristics of superhydrophobic surfaces with various morphologies by using quartz crystal microresonators. Anodic aluminum oxide (AAO) or ZnO nanorods were synthesized directly on gold-coated quartz crystal substrates and their surfaces were rendered hydrophobic via chemical modifications with octyltrichlorosilane (OTS), octadecyltrichlorosilane (ODS), or octadecanethiol (ODT). Four different hydrophobic nanostructures were prepared on the quartz crystals: ODT-modified hydrophobic plain gold (C18-Au), an OTS-modified AAO nanostructure (C8-AAO), an ODS-modified AAO nanostructure (C18-AAO), and ODT-modified ZnO nanorods (C18-ZnO). The water contact angles on the C18-Au, C8-AAO, C18-AAO, and C18-ZnO surfaces were measured to be 91.4°, 147.2°, 156.3°, and 157.8°, respectively. A sessile water droplet was placed on each quartz crystal and its freezing temperature was determined by monitoring the drastic changes in the resonance frequency and Q-factor upon freezing. The freezing temperature of a water droplet was found to decrease with decreases in the water contact radius due to the decreases in the number of active sites available for ice nucleation. PMID:25637961

  13. Simulation and modeling of self-assembled monolayers of carboxylic acid thiols on flat and nanoparticle gold surfaces.

    PubMed

    Techane, Sirnegeda; Baer, Donald R; Castner, David G

    2011-09-01

    Quantitative analysis of the 16-mercaptohexadecanoic acid self-assembled monolayer (C16 COOH-SAM) layer thickness on gold nanoparticles (AuNPs) was performed using simulation of electron spectra for surface analysis (SESSA) software and X-ray photoelectron spectroscopy (XPS) experimental measurements. XPS measurements of C16 COOH-SAMs on flat gold surfaces were made at nine different photoelectron emission angles (5-85° in 10° increments), corrected using geometric weighting factors and then summed together to approximate spherical AuNPs. The SAM thickness and relative surface roughness (RSA) in SESSA were optimized to determine the best agreement between simulated and experimental surface composition. On the basis of the glancing-angle results, it was found that inclusion of a hydrocarbon-contamination layer on top the C16 COOH-SAM was necessary to improve the agreement between the SESSA and XPS results. For the 16 COOH-SAMs on flat Au surfaces, using a SAM thickness of 1.1 Å/CH(2) group, an RSA of 1.05, and a 1.5 Å CH(2)-contamination overlayer (total film thickness = 21.5 Å) for the SESSA calculations provided the best agreement with the experimental XPS data. After applying the appropriate geometric corrections and summing the SESSA flat-surface compositions, the best fit results for the 16 COOH-SAM thickness and surface roughness on the AuNPs indicated a slightly thinner overlayer with parameters of 0.9 Å/CH(2) group in the SAM, an RSA of 1.06 RSA, and a 1.5 Å CH(2)-contamination overlayer (total film thickness = 18.5 Å). The 3 Å difference in SAM thickness between the flat Au and AuNP surfaces suggests that the alkyl chains of the SAM are slightly more tilted or disordered on the AuNP surfaces.

  14. Adhesion and Atomic Structures of Gold on Ceria Nanostructures:The Role of Surface Structure and Oxidation State of Ceria Supports

    SciTech Connect

    Lin, Yuyuan; Wu, Zili; Wen, Jianguo; Poeppelmeier, Kenneth R; Marks, Laurence D

    2015-01-01

    Recent advances in heterogeneous catalysis have demonstrated that oxides supports with the same material but different shapes can result in metal catalysts with distinct catalytic properties. The shape-dependent catalysis was not well-understood owing to the lack of direct visualization of the atomic structures at metal-oxide interface. Herein, we utilized aberration-corrected electron microscopy and revealed the atomic structures of gold particles deposited on ceria nanocubes and nanorods with {100} or {111} facets exposed. For the ceria nanocube support, gold nanoparticles have extended atom layers at the metal-support interface. In contrast, regular gold nanoparticles and rafts are present on the ceria nanorod support. After hours of water gas shift reaction, the extended gold atom layers and rafts vanish, which is associated with the decrease of the catalytic activities. By understanding the atomic structures of the support surfaces, metal-support interfaces, and morphologies of the gold particles, a direct structure-property relationship is established.

  15. Sensitivity of transmission surface plasmon resonance (T-SPR) spectroscopy: self-assembled multilayers on evaporated gold island films.

    PubMed

    Doron-Mor, Ilanit; Cohen, Hagai; Barkay, Zahava; Shanzer, Abraham; Vaskevich, Alexander; Rubinstein, Israel

    2005-09-19

    The distance dependence of the localized surface plasmon (SP) extinction of discontinuous gold films is a crucial issue in the application of transmission surface plasmon resonance (T-SPR) spectroscopy to chemical and biological sensing. This derives from the usual sensing configuration, whereby an analyte binds to a selective receptor layer on the gold film at a certain distance from the metal surface. In the present work the distance sensitivity of T-SPR spectroscopy of 1.0-5.0 nm (nominal thickness) gold island films evaporated on silanized glass substrates is studied by using coordination-based self-assembled multilayers, offering thickness tuning in the range from approximately 1 to approximately 15 nm. The morphology, composition and optical properties of the Au/multilayer systems were studied at each step of multilayer construction. High-resolution scanning electron microscopy (HRSEM) showed no apparent change in the underlying Au islands, while atomic force microscopy (AFM) indicated flattening of the surface topography during multilayer construction. A regular growth mode of the organic layers was substantiated by X-ray photoelectron spectroscopy (XPS). Transmission UV-visible spectra showed an increase of the extinction and a red shift of the maximum of the SP band upon addition of organic layers, establishing the distance dependence of the Au SP absorbance. The distance sensitivity of T-SPR spectroscopy can be varied by using characteristic substrate parameters, that is, Au nominal thickness and annealing. In particular, effective sensitivity up to a distance of at least 15 nm is demonstrated with 5 nm annealed Au films. It is shown that intensity measurements, particularly in the plasmon intensity change (PIC) presentation, provide an alternative to the usually measured plasmon band position, offering good accuracy and the possibility of measuring at a single wavelength. The present distance sensitivity results provide the basis for further development

  16. Nanoscale glassification of gold substrates for surface plasmon resonance analysis of protein toxins with supported lipid membranes.

    PubMed

    Phillips, K Scott; Han, Jong-Ho; Martinez, Marilyn; Wang, Zhuangzhi; Carter, David; Cheng, Quan

    2006-01-15

    Surface plasmon resonance (SPR) spectroscopy, a powerful tool for biosensing and protein interaction analysis, is currently confined to gold substrates and the relevant surface chemistries involving dextran and functional thiols. Drawbacks of using self-assembled monolayers (SAMs) for SPR-related surface modification include limited stability, pinhole defects, bioincompatibility, and nonspecific protein adsorption. Here we report the development of stable nanometer-scale glass (silicate) layers on gold substrates for SPR analysis of protein toxins. The nanoscale silicate layers were built up with layer-by-layer deposition of poly(allylamine hydrochloride) and sodium silicate, followed by calcination at high temperature. The resulting silicate films have a thickness ranging from 2 to 15 nm and demonstrate outstanding stability in flow cell conditions. The use of these surfaces as a platform to construct supported bilayer membranes (SBMs) is demonstrated, and improved performance against protein adsorption on SBM-coated surfaces is quantified by SPR measurements. SBMs can be formed reproducibly on the silicate surface via vesicle fusion and quantitatively removed using injection of 5% Triton X-100 solution, generating a fresh surface for each test. Membrane properties such as lateral diffusion of the SBMs on the silicate films are characterized with photobleaching methods. Studies of protein binding with biotin/avidin and ganglioside/cholera toxin systems show detection limits lower than 1 microg/mL (i.e., nanomolar range), and the response reproducibility is better than 7% RSD. The method reported here allows many assay techniques developed for glass surfaces to be transferred to label-free SPR analysis without the need for adaptation of protocols and time-consuming synthetic development of thiol-based materials and opens new avenues for developing novel bioanalytical technologies for protein analysis. PMID:16408945

  17. Effect of Ions and Ionic Strength on Surface Plasmon Absorption of Single Gold Nanowires.

    PubMed

    Baral, Susil; Green, Andrew J; Richardson, Hugh H

    2016-06-28

    The local temperature change from a single optically excited gold nanowire, lithographically prepared on Al0.94Ga0.06N embedded with Er(3+) ions, is measured in air, pure water, and various concentrations of aqueous solutions of ionic solutes of NaCl, Na2SO4, and MgSO4. The absorption cross section of the nanowire under pure water (2.25 × 10(-14) m(2)) and different solution ionic strength is measured from the slopes of temperature change versus laser intensity plots. Addition of charges into the solution decreases the amount of heat generated during optical excitation of the gold nanostructures because the absorption cross section of the gold nanowire is attenuated. A Langmuir-type behavior of the absorption cross section with ionic strength is observed that is identified with an increase in the occupancy of screened interfacial charges. The absorption cross section of the nanowire decreases with ionic strength until a saturation value of 9 × 10(-15) m(2), where saturation in the occupancy of screened interfacial charge occurs. Dynamic measurements of temperature for a single gold nanowire immersed in a microchannel flow cell show a sharp and fast temperature drop for the flow of ionic solution compared to the pure (deionized) water, suggesting that the technique can be developed as a sensor probe to detect the presence of ions in solution.

  18. Electronic structure at nanocontacts of surface passivated CdSe nanorods with gold clusters.

    PubMed

    Saraf, Deepashri; Kshirsagar, Anjali

    2014-06-14

    We report the electronic structure of free standing and gold attached passivated CdSe nanorods. The goal is to assess the changes at the nanolevel after formation of contacts with gold clusters serving as electrodes and compare the results with experimental observations [Steiner et al., Phys. Rev. Lett., 2005, 95, 056805]. It is interesting to note that upon attaching gold clusters, the nanorods shorter than 27 Å develop metallicity by means of metal induced gap states (MIGS). Longer nanorods exhibit a nanoscale Schottky barrier emerging at the center. For these nanorods, the interfacial region closest to the gold electrodes shows a finite density of states in the gap due to MIGS, which gradually decreases towards the center of the nanorod opening up a finite gap. Our theoretical results agree qualitatively with the experimental results of Steiner et al. This study attempts to identify the minimum length of a one-dimensional nanostructure to be used in an electronic device. An analysis of density of states and charge density brings out the role of hybridization of semiconductor states with metal states. Bader charge analysis indicates localized charge transfer from metal to semiconductor.

  19. Theoretical investigation of gas-surface interactions

    NASA Technical Reports Server (NTRS)

    Dyall, Kenneth G.

    1992-01-01

    The investigation into the appearance of intruder states from the negative continuum when some of the two-electron integrals were omitted was completed. The work shows that, provided all integrals involving core contracted functions in an atomic general contraction are included, or that the core functions are radially localized, meaningful results are obtained and intruder states do not appear. In the area of program development, the Dirac-Hartree-Fock (DHF) program for closed-shell polyatomic molecules was extended to permit Kramers-restricted open-shell DHF calculations with one electron in an open shell or one hole in a closed shell, or state-averaged DHF calculations over several particle or hole doublet states. One application of the open-shell code was to the KO molecule. Another major area of program development is the transformation of integrals from the scalar basis in which they are generated to the 2-spinor basis employed in parts of the DHF program, and hence to supermatrix form. Particularly concerning the omission of small component integrals, and with increase in availability of disk space, it is now possible to consider transforming the integrals. The use of ordered integrals, either in the scalar basis or in the 2-spinor basis, would considerably speed up the construction of the Fock matrix, and even more so if supermatrices were constructed. A considerable amount of effort was spent on analyzing the integral ordering and tranformation for the DHF program. The work of assessing the reliability of the relativistic effective core potentials (RECPs) was continued with calculation of the group IV monoxides. The perturbation of the metal atom provided by oxygen is expected to be larger than that provided by hydrogen and thus provide a better test of the qualification of the RECPs. Calculations on some platinum hydrides were carried out at nonrelativistic (NR), perturbation theory (PT) and DHF levels. Reprints of four papers describing this work are

  20. Raman and surface enhanced Raman scattering study of the orientation of cruciform 9,10-anthracene thiophene and furan derivatives deposited on a gold colloidal surface

    NASA Astrophysics Data System (ADS)

    Muñoz-Pérez, J.; Leyton, P.; Paipa, C.; Soto, J. P.; Brunet, J.; Gómez-Jeria, J. S.; Campos-Vallette, M. M.

    2016-10-01

    The 9,10-di(thiophen-2-yl)anthracene (TAT), 9,10-di(furan-2-yl)anthracene (FAF) and 2-[(10-(thiophen-2-yl)anthracen-9-yl)]furan (TAF) cruciform molecular systems were synthesized using one-step coupling reactions and structurally characterized via Raman, infrared, 1H NMR, 13C NMR and mass spectroscopies. The orientation of the analytes on a gold colloidal surface was inferred from a surface-enhanced Raman scattering (SERS) study. The metal surface interaction was driven by the S and O atoms of the thiophene and furan α-substituents, and the plane of the anthracene fragment remained parallel to the surface. Theoretical calculations based on a simplified molecular model for the analyte-surface interaction provide a good representation of the experimental data.

  1. Unique gold sponges: biopolymer-assisted hydrothermal synthesis and potential application as surface-enhanced Raman scattering substrates

    NASA Astrophysics Data System (ADS)

    Gao, Shuyan; Zhang, Hongjie; Wang, Xiaomei; Yang, Jianhui; Zhou, Liang; Peng, Chunyun; Sun, Dehui; Li, Meiye

    2005-11-01

    In this paper we describe a biopolymer-assisted hydrothermal approach to the synthesis of gold sponges. This is carried out by transferring a hyaluronic acid potassium salt/HAuCl4 aqueous solution into a stainless steel autoclave with a Teflon liner and heating in an oven at 180 °C for 6 h. Here, hyaluronic acid potassium salt plays three roles in the synthesis, namely, stabilization, reduction, and as a soft template. Field emission scanning electron microscopy images, energy-dispersive x-ray spectroscopy, and x-ray diffraction reveal that the materials obtained consist of an interconnected framework of face-centred cubic metallic gold filaments, which is approximately 0.6 µm in width and composed of fused micrometre-sized particles that enclose pores 1-4 µm in size. The test of surface-enhanced Raman scattering (SERS) from 4-mercaptobenzoic acid shows that the prepared gold sponges are an active SERS substrate. This is largely because they had an increased number of particle junctions, which are SERS active sites. This route can also be extended to the fabrication of silver sponges, which are composed of fused crystallites with diameters of 200-400 nm that enclosed pores 0.4-2 µm in size. The test of SERS from Rhodamine 6G also reveals that the prepared silver sponges are likewise an excellent SERS substrate.

  2. Extensive ionic partitioning in interfaces that membranous and biomimetic surfaces form with electrolytes: Antitheses of the gold-electrolyte interface

    NASA Astrophysics Data System (ADS)

    Chilcott, Terry; Guo, Chuan; Coster, Hans

    2013-04-01

    Maxwell-Wagner modeling of electrical impedance measurements of tetradecane-electrolyte systems yielded three interfacial layers between the tetradecane layer and the bulk electrolytes of concentration ranging from 1-300 mM KCl whereas the gold-electrolyte system yielded only one layer. The conductivity and thickness for the surface layer were orders of magnitude different from that expected for the Gouy-Chapman layer and did not reflect dependencies of the Debye length on concentration. Conductivity values for the three layers were less than those of the bulk electrolyte but exhibited a dependency on concentration similar to that expected for the bulk. Thickness values for the layers indicate an interface extending ~106 Å into the bulk electrolyte, which contrasts with the gold-electrolyte interface that extended only 20-30 Å into the bulk. Maxwell-Wagner characterizations of both interfaces were consistent with spatial distributions of ionic partitioning arising from the Born energy as determined by the dielectric properties of the substrates and electrolyte. The distributions for the membranous and silicon interfaces were similar but the antitheses of that for the gold interface.

  3. Surface plasmon induced polarization filter of the gold-coated photonic crystal fiber with a liquid core

    NASA Astrophysics Data System (ADS)

    Jiang, Linghong; Zheng, Yi; Hou, Lantian; Zheng, Kai; Peng, Jiying

    2015-06-01

    A new gold-coated photonic crystal fiber (PCF) which can achieve a specific wavelength filter has been proposed. The polarization filter characteristics of the PCF based on the finite element method are investigated. Numerical results show that moving the two gold-coated holes toward the central core in longitudinal direction and filling pure water in the central defected air-hole can effectively enhance polarization extinction ratio around the resonance wavelength. The resonance strength in y-polarized case is far stronger than that in x-polarized case, the peak loss of the PCF with different coating thickness in y polarization can reach 536.25 dB/cm and 412.91 dB/cm at the communication wavelength of 1.55 μm and 1.31 μm, respectively, while the losses are very low in x polarization. This is beneficial for the study and application in many polarization filter devices.

  4. Structural and Electronic Properties of Gold Contacts on CdZnTe with Different Surface Finishes for Radiation Detector Applications

    NASA Astrophysics Data System (ADS)

    Tari, S.; Aqariden, F.; Chang, Y.; Ciani, A.; Grein, C.; Li, Jin; Kioussis, N.

    2014-08-01

    State-of-the-art room-temperature, high-resolution x-ray and gamma-ray semiconductor detectors can be fabricated from CdZnTe (CZT) crystals. The structural and electronic properties of the CZT surface, especially the contact interfaces, can have a substantial effect on radiation detector performance, for example leakage current, signal-to-noise ratio, and energy resolution, especially for soft x-rays and large pixilated arrays. Atomically smooth and defect-free surfaces are desirable for high-performance CZT-based detectors; chemo-mechanical polishing (CMP) is typically performed to produce such surfaces. The electrical behavior of the metal/CZT interface varies substantially with surface preparation before contact deposition, and with choice of metal and deposition technique. We report a systematic study of the structural and electronic properties of gold (Au) contacts on CZT prepared with different surface finishes. We observed subsurface damage under Au contacts on CMP-finished CZT and abrupt interfaces for Au on chemically-polished (CP) CZT. Schottky barrier formation was observed for Au contacts, irrespective of surface finish, and less charge trapping and low surface resistance were observed for CP-finished surfaces. Pre-deposition surface treatment produced interfaces free from oxide layers.

  5. Investigation of mechanical properties of twin gold crystal nanowires under uniaxial load by molecular dynamics method

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Wei; Yang, Zai-Lin; Luo, Gang

    2016-08-01

    Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated. We calculate the nanowires under tensile or compressive loads, different length nanowires, and different twin boundary nanowires respectively. The Young modulus of nanowires under compressive load is about twice that under tensile load. The compressive properties of twin gold nanowires are superior to their tensile properties. For different length nanowires, there is a critical value of length with respect to the mechanical properties. When the length of nanowire is greater than the critical value, its mechanical properties are sensitive to length. The twin boundary spacing hardly affects the mechanical properties. Project supported by the National Science and Technology Pillar Program, China (Grant No. 2015BAK17B06), the Earthquake Industry Special Science Research Foundation Project, China (Grant No. 201508026-02), the Natural Science Foundation of Heilongjiang Province, China (Grant No. A201310), and the Scientific Research Starting Foundation for Post Doctorate of Heilongjiang Province, China (Grant No. LBHQ13040).

  6. Investigation of mechanical properties of twin gold crystal nanowires under uniaxial load by molecular dynamics method

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Wei; Yang, Zai-Lin; Luo, Gang

    2016-08-01

    Twin gold crystal nanowires, whose loading direction is parallel to the twin boundary orientation, are simulated. We calculate the nanowires under tensile or compressive loads, different length nanowires, and different twin boundary nanowires respectively. The Young modulus of nanowires under compressive load is about twice that under tensile load. The compressive properties of twin gold nanowires are superior to their tensile properties. For different length nanowires, there is a critical value of length with respect to the mechanical properties. When the length of nanowire is greater than the critical value, its mechanical properties are sensitive to length. The twin boundary spacing hardly affects the mechanical properties. Project supported by the National Science and Technology Pillar Program, China (Grant No. 2015BAK17B06), the Earthquake Industry Special Science Research Foundation Project, China (Grant No. 201508026-02), the Natural Science Foundation of Heilongjiang Province, China (Grant No. A201310), and the Scientific Research Starting Foundation for Post Doctorate of Heilongjiang Province, China (Grant No. LBHQ13040).

  7. Nonlinear optical property of hemicyanine self-assembled monolayers on gold and its adsorption kinetics probed by optical second-harmonic generation and surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Naraoka, Ryo; Kaise, Go; Kajikawa, Kotaro; Okawa, Haruki; Ikezawa, Hiroki; Hashimoto, Kazuhiko

    2002-08-01

    We have prepared the organosulfur self-assembled monolayer (SAM) containing hemicyanine on gold. It shows a large second-order nonlinear optical susceptibility χzzz=58 pm/V. The adsorption kinetics of the SAM on gold was also probed by the in situ real time measurements of second-harmonic generation (SHG) and surface plasmon resonance (SPR) spectroscopy. While the SHG kinetics was saturated immediately after the immersion of the gold substrate in the solution, the SPR kinetics showed additional slow adsorption for more than 20 000 s. This means that rapid formation of the well-ordered hemicyanine SAM is followed by gradual physisorption where the molecules are disordered.

  8. Comparative sessile drop and dip pen nanolithography investigation for various hydrophilic ink/surface systems.

    PubMed

    Yadav, Pradeep K; Lemoine, Patrick

    2012-01-01

    We present a dip pen nanolithography study of various hydrophilic ink/surface systems with application in the field of biosensors and novel nano-materials. The inking process was investigated by studying a number of inks, such as Deoxyribonucleic acid (DNA), Bovine serum albumin (BSA), Streptavidin, 16-mercaptohexadecanoic acid (MHA) and a 20 nm nanosphere (NS) polystyrene solution onto a range of substrates, namely glass, silicon, gold and tetrahedral amorphous carbon (taC). In the majority of cases, this resulted in patterns with sub-100 nm line widths and dot diameters. Importantly, contact angle measurements in the microl range showed a decrease of contact angle with drop volume, interpreted as a line tension effect. The significance of this to the nanoscale wetting behaviour is discussed. The effect of dwell time and writing speed indicates that the inking process is not solely defined by surface diffusion but also influenced by the ink dissolution rate from the tip. PMID:22523946

  9. High spatial resolution mapping of surface plasmon resonance modes in single and aggregated gold nanoparticles assembled on DNA strands

    PubMed Central

    2013-01-01

    Abstract We present the mapping of the full plasmonic mode spectrum for single and aggregated gold nanoparticles linked through DNA strands to a silicon nitride substrate. A comprehensive analysis of the electron energy loss spectroscopy images maps was performed on nanoparticles standing alone, dimers, and clusters of nanoparticles. The experimental results were confirmed by numerical calculations using the Mie theory and Gans-Mie theory for solving Maxwell's equations. Both bright and dark surface plasmon modes have been unveiled. PACS 78.67.Bf; 61.46.Df; 87.64.Ee PMID:23890222

  10. Real-Time Label-Free Surface Plasmon Resonance Biosensing with Gold Nanohole Arrays Fabricated by Nanoimprint Lithography

    PubMed Central

    Martinez-Perdiguero, Josu; Retolaza, Aritz; Otaduy, Deitze; Juarros, Aritz; Merino, Santos

    2013-01-01

    In this work we present a surface plasmon resonance sensor based on enhanced optical transmission through sub-wavelength nanohole arrays. This technique is extremely sensitive to changes in the refractive index of the surrounding medium which result in a modulation of the transmitted light. The periodic gold nanohole array sensors were fabricated by high-throughput thermal nanoimprint lithography. Square periodic arrays with sub-wavelength hole diameters were obtained and characterized. Using solutions with known refractive index, the array sensitivities were obtained. Finally, protein absorption was monitored in real-time demonstrating the label-free biosensing capabilities of the fabricated devices. PMID:24135989

  11. Gold surfaces and nanoparticles are protected by Au(0)-thiyl species and are destroyed when Au(I)-thiolates form.

    PubMed

    Reimers, Jeffrey R; Ford, Michael J; Halder, Arnab; Ulstrup, Jens; Hush, Noel S

    2016-03-15

    The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)-thiyl, with Au(I)-thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)-thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s-d hybridization and charge polarization effects that perturbatively mix in some Au(I)-thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)-thiolate involvement. Predictions that Brust-Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)-thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established.

  12. Friction and transfer of copper, silver, and gold to iron in the presence of various adsorbed surface films

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with the noble metals copper, silver, and gold and two binary alloys of these metals contacting iron in the presence of various adsorbates including, oxygen, methyl mercaptan, and methyl chloride. A pin on disk specimen configuration was used with a load of 100 grams, sliding velocity of 60 mm/min; at 25 C with the surfaces saturated with the adsorbates. Auger emission spectroscopy was used to monitor surface films. Results of the experiments indicate that friction and transfer characteristics are highly specific with respect to both the noble metal and surface film present. With all three metals and films transfer of the noble metal to iron occurred very rapidly. With all metals and films transfer of the noble metal to iron continuously increased with repeated passes except for silver and copper sliding on iron sulfide.

  13. First-principles investigations of the structure and stability of oxygen adsorption and surface oxide formation at Au(111)

    NASA Astrophysics Data System (ADS)

    Shi, Hongqing; Stampfl, Catherine

    2007-08-01

    We perform density-functional theory calculations to investigate the adsorption of oxygen at the Au(111) surface, including on-surface, subsurface, and surface oxide formation. We find that atomic oxygen adsorbs weakly on the surface and is barely stable with respect to molecular oxygen, while pure subsurface adsorption is only metastable. Interestingly, however, we find that the most favorable structure investigated involves a thin surface-oxide-like configuration, where the oxygen atoms are quasithreefold-coordinated to gold atoms, and the gold atoms of the surface layer are twofold, linearly coordinated to oxygen atoms. By including the effect of temperature and oxygen pressure through the description of ab initio atomistic thermodynamics, we find that this configuration is the most stable for realistic catalytic temperatures and pressures, e.g., for low-temperature oxidation reactions, and is predicted to be stable up to temperatures of around 420K at atmospheric pressure. This gives support to the notion that oxidized Au, or surface-oxide-like regions, could play a role in the behavior of oxide-supported nanogold catalysts.

  14. Determination of the surface density of polyethylene glycol on gold nanoparticles by use of microscale thermogravimetric analysis.

    PubMed

    Sebby, K B; Mansfield, E

    2015-04-01

    The widespread integration of nanoparticle technologies into biomedicine will depend on the ability to repeatedly create particles with well-defined properties and predictable behaviors. For this to happen, fast, reliable, inexpensive, and widely available techniques to characterize nanomaterials are needed. Characterization of the surface molecules is particularly important since the surface, including the surface molecule density, plays a dominant role in determining how nanoparticles interact with their surroundings. Here, 10 and 30 nm gold nanoparticle NIST Standard Reference Materials were functionalized with fluorescently labeled polyethylene glycol (PEG) with either thiolate or lipoic acid anchoring groups to evaluate analytical techniques for determining surface coverage. The coating of the nanoparticles was confirmed with dynamic light scattering, microscale thermogravimetric analysis (μ-TGA), and ultraviolet-visible (UV-vis) spectroscopy. A UV-vis method for determining gold nanoparticle concentrations that takes into account spectral broadening upon functionalization was developed. The amount of bound PEG was quantified with μ-TGA, a technique analogous to thermogravimetric analysis that uses quartz crystal microbalances, and fluorescence spectroscopy of displaced ligands. It is shown that μ-TGA is a convenient technique for the quantification of ligands bound to inorganic particles while sacrificing a minimal amount of sample, and the treatment of the functionalized nanoparticle dispersions with dithiothreitol may be insufficient to achieve complete displacement of the surface ligands for quantification by fluorescence measurements. The μ-TGA and fluorescence results were used to determine ligand footprint sizes-average areas occupied by each ligand on the particles' surface. The lipoic acid bound ligands had footprint sizes of 0.21 and 0.25 nm(2) on 10 and 30 nm particles, respectively while the thiolate ligands had footprint sizes of 0.085 and 0

  15. Real time nanoscale structural evaluation of gold structures on Si (100) surface using in-situ transmission electron microscopy

    SciTech Connect

    Rath, A. E-mail: ashutosh.phy@gmail.com E-mail: pvsatyam22@gmail.com; Juluri, R. R.; Satyam, P. V. E-mail: ashutosh.phy@gmail.com E-mail: pvsatyam22@gmail.com

    2014-05-14

    Transport behavior of gold nanostructures on Si(100) substrate during annealing under high vacuum has been investigated using in-situ real time transmission electron microscopy (TEM). A comparative study has been done on the morphological changes due to annealing under different vacuum environments. Au thin films of thickness ∼2.0 nm were deposited on native oxide covered silicon substrate by using thermal evaporation system. In-situ real time TEM measurements at 850 °C showed the isotropic growth of rectangular/square shaped gold-silicon alloy structures. During the growth, it is observed that the alloying occurs in liquid phase followed by transformation into the rectangular shapes. For similar system, ex-situ annealing in low vacuum (10{sup −2} millibars) at 850 °C showed the spherical gold nanostructures with no Au-Si alloy formation. Under low vacuum annealing conditions, the rate of formation of the oxide layer dominates the oxide desorption rate, resulting in the creation of a barrier layer between Au and Si, which restricts the inter diffusion of Au in to Si. This work demonstrates the important role of interfacial oxide layer on the growth of nanoscale Au-Si alloy structures during the initial growth. The time dependent TEM images are presented to offer a direct insight into the fundamental dynamics of the sintering process at the nanoscale.

  16. Enhancing laser thermal-therapy using ultrasound-microbubbles and gold nanorods: In vitro investigation

    NASA Astrophysics Data System (ADS)

    Tarapacki, Christine; Kumaradas, Carl; Karshafian, Raffi

    2012-11-01

    Gold nanorods (GNR) in laser-induced thermal therapy can significantly increase light absorption, leading to a local temperature increase and causing irreversible cell damage. One of the key challenges in using GNR as a thermal therapy agent is to deliver a concentration of GNR to generate sufficient heat and cause cell death. In this study, ultrasound and microbubble induced sonoporation is used to enhance intracellular uptake of GNR and improve the therapeutic outcome of laserinduced thermal therapy. Acute myeloid leukemia (AML) cells in suspension (0.6 mL) were treated with ultrasound and microbubbles (USMB) at 1 MHz frequency, 16 microseconds pulse duration, 1 kHz pulse repetition frequency, 1 minute insonation time, varying acoustic pressures (0, 1.26 and 1.73 MPa) and 10 μL Definity microbubble agent with and without GNR (12 nm × 48 nm) at varying concentration (1.0×1010 to 2.5×1011 GNR/mL). The GNR were manufactured through wet chemical synthesis process and measured using Transmission Electron Microscopy (TEM) and Atomic Absorption Spectroscopy (AAS) for size and concentration respectively. Following ultrasound and microbubble treatment, cells were centrifuged to remove excess gold nanorods and treated in suspension with an 810 nm laser (Diomed 60 NIR) at 4 W for 5 minutes. A thermal camera (FLIR Thermovision A40) was positioned to monitor the sample temperature throughout laser treatment and cell viability was assessed using flow cytometry with propidium iodide. Cell viability of 18±2% was achieved with GNR+USMB (1.26 MPa) compared to 72±3% with GNR alone (12 hour incubation) and 99±0.2% with USMB (1.26 MPa) alone. With increasing GNR concentration during ultrasound and microbubble treatment, laser induced sample temperature increased and consequently cell viability decreased. Cell viability decreased from 92±1% at 1.0×1011 GNR/mL to 29±5% at 1.5×1011 GNR/mL concentration with corresponding maximum temperatures of 50°C and 54°C, respectively

  17. Solution-based direct readout surface enhanced Raman spectroscopic (SERS) detection of ultra-low levels of thiram with dogbone shaped gold nanoparticles.

    PubMed

    Saute, Benjamin; Narayanan, Radha

    2011-02-01

    We report the use of two different sizes of dogbone shaped gold nanoparticles as colloidal substrates for surface enhanced Raman spectroscopy (SERS) based detection of ultra-low levels of thiram, a dithiocarbamate fungicide. We demonstrate the ability to use a solution based, direct readout SERS method as a quantitative tool for the detection of ultra-low levels of thiram. The two different sizes of dogbone shaped gold nanoparticles are synthesized by using the seed-mediated growth method and characterized by using UV-visible spectroscopy and transmission electron microscopy (TEM). The smaller dogbone shaped nanoparticles have an average size of 43 ± 13 nm. The larger dogbone shaped gold nanoparticles have an average size of 65 ± 15 nm. The nanoparticle concentration is 1.25 × 10(11) nanoparticles per mL for the smaller dogbone shaped gold nanoparticles and is 1.13 × 10(11) nanoparticles per mL for the larger dogbone shaped gold nanoparticles. Different concentrations of thiram are allowed to bind to the two different sizes of dogbone shaped gold nanoparticles and the SERS spectra are obtained. From the calibration curve, the limit of detection for thiram is 43.9 ± 6.2 nM when the smaller dogbone shaped gold nanoparticles are used as colloidal SERS substrates In the case of the larger dogbone shaped gold nanoparticles, the limit of detection for thiram is 11.8 ± 3.2 nM. The lower limit of detection obtained by using the larger dogbone shaped gold nanoparticles as colloidal substrates is due to the lightning rod effect, higher contributions from the electromagnetic enhancement effect, and larger number of surface sites for thiram to bind.

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

    NASA Astrophysics Data System (ADS)

    Pretzer, Lori A.

    Transition metal nanomaterials are used to catalyze many chemical reactions, including those key to environmental, medicinal, and petrochemical fields. Improving their catalytic properties and lifetime would have significant economic and environmental rewards. Potentially expedient options to make such advancements are to alter the shape, size, or composition of transition metal nanocatalysts. This work investigates the relationships between structure and catalytic properties of synthesized Au, Pd-on-Au, and Au-enzyme model transition metal nanocatalysts. Au and Pd-on-Au nanomaterials were studied due to their wide-spread application and structure-dependent electronic and geometric properties. The goal of this thesis is to contribute design procedures and synthesis methods that enable the preparation of more efficient transition metal nanocatalysts. The influence of the size and composition of Pd-on-Au nanoparticles (NPs) was systematically investigated and each was found to affect the catalyst's surface structure and catalytic properties. The catalytic hydrodechlorination of trichloroethene and reduction of 4-nitrophenol by Pd-on-Au nanoparticles were investigated as these reactions are useful for environmental and pharmaceutical synthesis applications, respectively. Structural characterization revealed that the dispersion and oxidation state of surface Pd atoms are controlled by the Au particle size and concentration of Pd. These structural changes are correlated with observed Pd-on-Au NP activities for both probe reactions, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. Using the structure-dependent electronic properties of Au NPs, a new type of light-triggered biocatalyst was prepared and used to remotely control a model biochemical reaction. This biocatalyst consists of a model thermophilic glucokinase enzyme covalently attached to the surface of Au nanorods. The rod-like shape of the Au nanoparticles made the

  19. A combined QCM and XPS investigation of asphaltene adsorption on metal surfaces.

    PubMed

    Rudrake, Amit; Karan, Kunal; Horton, J Hugh

    2009-04-01

    To investigate asphaltene-metal interactions, a combined quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS) study of asphaltene adsorption on a gold surface was conducted. Adsorption experiments were conducted at 25 degrees C with solutions of asphaltenes in toluene at concentrations ranging from 50 to 1500 ppm. QCM measurements yielded information on the kinetics of adsorption and further assessment of the data allowed the estimation of equilibrium adsorption levels. XPS analysis of adsorbed and bulk asphaltene demonstrated the presence of carboxylic, thiophenic, sulfide, pyridinic and pyrrolic type functional groups. The intensity of the main carbon (C-H) peak was related to surface coverage of adsorbed asphaltene as a function of asphaltene concentration by a simple mathematical model. The mass adsorption data from the QCM experiments also allowed estimation of the surface coverage, which was compared to those from XPS analyses. Surface coverage estimates as a function of asphaltene concentration could be described by a Langmuir (type-I) isotherm. The free energy of asphaltene adsorption was estimated to be -26.8+/-0.1 and -27.3+/-0.1 kJ/mol from QCM and XPS data, respectively assuming asphaltene molar mass of 750 g/gmol. QCM and XPS data was also analyzed to estimate adsorbed layer thickness after accounting for surface coverage. The thickness of the adsorbed asphaltene estimated from both XPS and QCM data analyses ranged from 6-8 nm over the entire range of adsorption concentrations investigated.

  20. [Investigation of stages of chemical leaching and biooxidation during the extraction of gold from sulfide concentrates].

    PubMed

    Murav'ev, M I; Fomchenko, N V; Kondrat'eva, T V

    2015-01-01

    We examined the chemical leaching and biooxidation stages in a two-stage biooxidation process of an auriferous sulfide concentrate containing pyrrhotite, arsenopyrite and pyrite. Chemical leaching of the concentrate (slurry density at 200 g/L) by ferric sulfate biosolvent (initial concentration at 35.6 g/L), which was obtained by microbial oxidation of ferrous sulfate for 2 hours at 70°C at pH 1.4, was allowed to oxidize 20.4% ofarsenopyrite and 52.1% of sulfur. The most effective biooxidation of chemically leached concentrate was observed at 45°C in the presence of yeast extract. Oxidation of the sulfide concentrate in a two-step process proceeded more efficiently than in one-step. In a two-step mode, gold extraction from the precipitate was 10% higher and the content of elemental sulfur was two times lower than in a one-step process.

  1. Enhanced infrared transmission from gold wire-grid arrays via surface plasmons in continuous graphene (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Liu, Zizhuo; Bütün, Serkan; Palacios, Edgar; Aydin, Koray

    2015-09-01

    Enhanced transmission of light through nanostructures has always been of great interest in the field of plasmonics and nanophotonics. With the aid of near-field effects, the transmission of the electromagnetic waves can be enhanced or suppressed. Much of the work on enhanced transmission has been shown to be frequency-selective. However it is possible to increase the transmission over a large frequency range by using graphene, which has shown broadband properties in many applications. Here, we propose enhanced transmission in wire grid gold structure making use of continuous graphene sheets. We use finite-difference time-domain simulations to study the optical properties of this graphene-metal hybrid structure at mid infrared (mid-IR) wavelengths. The grating structure in wire grid gold provides an ideal platform to match the momentum and excite the surface plasmon polaritons (SPPs) in monolayer graphene. Our numerical calculations show that the local electromagnetic field around the graphene is largely enhanced due to surface plasmons. Moreover, with the highly confined SPPs coupling with the incident light, the transmission through the whole structure can be broadly enhanced in the mid infrared region. We also analyze the effect of the spectrum with different periods and gold nanowire widths to evaluate the size effects of the plasmons in graphene. In addition, by tuning the Fermi level, one can control the wavelength range at which the transmission is enhanced. The mechanism of the enhancement will be explained in the calculated electric field distribution. And we will also highlight the opportunities of graphene for applications such as tunable transmission and active photonic modulator.

  2. Molecular-level insights of early-stage prion protein aggregation on mica and gold surface determined by AFM imaging and molecular simulation.

    PubMed

    Lou, Zhichao; Wang, Bin; Guo, Cunlan; Wang, Kun; Zhang, Haiqian; Xu, Bingqian

    2015-11-01

    By in situ time-lapse AFM, we investigated early-stage aggregates of PrP formed at low concentration (100 ng/mL) on mica and Au(111) surfaces in acetate buffer (pH 4.5). Remarkably different PrP assemblies were observed. Oligomeric structures of PrP aggregates were observed on mica surface, which was in sharp contrast to the multi-layer PrP aggregates yielding parallel linear patterns observed Au(111) surface. Combining molecular dynamics and docking simulations, PrP monomers, dimers and trimers were revealed as the basic units of the observed aggregates. Besides, the mechanisms of the observed PrP aggregations and the corresponding molecular-substrate and intermolecular interactions were suggested. These interactions involved gold-sulfur interaction, electrostatic interaction, hydrophobic interaction, and hydrogen binding interaction. In contrast, the PrP aggregates observed in pH 7.2 PBS buffer demonstrated similar large ball-like structures on both mica and Au(111) surfaces. The results indicate that the pH of a solution and the surface of the system can have strong effects on supramolecular assemblies of prion proteins. This study provides in-depth understanding on the structural and mechanistic nature of PrP aggregation, and can be used to study the aggregation mechanisms of other proteins with similar misfolding properties.

  3. Surface engineered gold nanoparticles through highly stable metal-surfactant complexes.

    PubMed

    Kim, Sunghwan; Jang, Youngjin; Yoon, Ki Youl; Park, Jongnam

    2016-02-15

    Monodispersed Au nanoparticles were synthesized by the reduction of Au-decyltrimethylammonium bromide (Au-DTAB), which was easily prepared via the reaction of HAuCl4 and DTAB. This Au-DTAB complex is highly stable in air and moisture, and suitable for large-scale synthesis of uniform-sized Au nanoparticles. The nanoparticles were characterized by transmission electron microscopy, optical absorption spectrometry, X-ray diffraction, and Fourier Transform infrared spectroscopy. The size of Au nanoparticles was controlled in the range of 5-10nm by changing the concentrations of reducing agent and Au precursor. The resulting Au nanoparticles were transferred to the aqueous phase after surface engineering using multidentate polymeric ligands with multiple imidazole functional groups. Polymeric imidazole ligands (PILs) demonstrated enhanced binding stability with the Au surface, and overcame the disadvantage of multidentate thiol ligand systems which have oxidative cross-linking and the formation of disulfide bonding. The colloidal stability of surface engineered Au nanoparticles with PILs was investigated by dynamic light scattering (DLS) characterization.

  4. Facile preparation of surface-exchangeable core@shell iron oxide@gold nanoparticles for magnetic solid-phase extraction: use of gold shell as the intermediate platform for versatile adsorbents with varying self-assembled monolayers.

    PubMed

    Li, Yaping; Qi, Li; Shen, Ying; Ma, Huimin

    2014-02-01

    The core@shell Fe3O4@Au nanoparticles (NPs) functionalized with exchangeable self-assembled monolayers have been developed for mode switching magnetic solid-phase extraction (MSPE) using high performance liquid chromatography with ultraviolet detection. The adsorbents were synthesized by chemical coprecipitation to prepare magnetic cores followed by sonolysis to produce gold shells. Functionalization of Fe3O4@Au NPs surface was realized through self-assembly of commercially available low molecular weight thiol-containing ligands using gold shells as intermediate platform and the dynamic nature of Au-S chemistry allowed substituent of one thiol-containing ligand with another simply by thiol exchange process. The resultant adsorbents were characterized by transmission electronic microscopy, Fourier transform infrared spectroscopy, elemental analysis, contact angle measurement, and vibrating sample magnetometry. To evaluate the versatile performance of the developed MSPE adsorbents, they were applied for normal-phase SPE followed by reversed-phase SPE. A few kinds of diphenols and polycyclic aromatic hydrocarbons (PAHs) were employed as model analytes, respectively. The predominant parameters affecting extraction efficiency were investigated and optimized. Under the optimum experimental conditions, wide dynamic linear range (6.25-1600 μg L(-1) for diphenols and 1.56-100 μg L(-1) for PAHs) with good linearity (r(2)≥0.989) and low detection limits (0.34-16.67 μg L(-1) for diphenols and 0.26-0.52 μg L(-1) for PAHs) were achieved. The advantage of the developed method is that the Fe3O4@Au NPs could be reutilized for preconcentrating diverse target analytes in different SPE modes sequentially simply through treatment with desired thiol-containing ligands.

  5. A theoretical investigation of the (0001) covellite surfaces

    SciTech Connect

    Gaspari, Roberto; Manna, Liberato; Cavalli, Andrea

    2014-07-28

    We report on the properties of the (0001) covellites surfaces, which we investigate by periodic slab density functional theory calculations. The absolute surface energies have been computed for all bulk terminations, showing that surfaces terminated by the flat CuS layer are associated with the lowest surface energy. Cleavage is predicted to occur across the [0001] interlayer Cu–S bond. The surfaces obtained by lowest energy cleavage are analyzed in terms of the atomic vertical relaxation, workfunction, and surface band structure. Our study predicts the presence of a shallow p{sub z}-derived surface state located 0.26 eV below the Fermi level, which is set to play an important role in the surface reactivity of covellite.

  6. Polymer nanopillar-gold arrays as surface-enhanced Raman spectroscopy substrate for the simultaneous detection of multiple genes.

    PubMed

    Picciolini, Silvia; Mehn, Dora; Morasso, Carlo; Vanna, Renzo; Bedoni, Marzia; Pellacani, Paola; Marchesini, Gerardo; Valsesia, Andrea; Prosperi, Davide; Tresoldi, Cristina; Ciceri, Fabio; Gramatica, Furio

    2014-10-28

    In our study, 2D nanopillar arrays with plasmonic crystal properties are optimized for surface-enhanced Raman spectroscopy (SERS) application and tested in a biochemical assay for the simultaneous detection of multiple genetic leukemia biomarkers. The special fabrication process combining soft lithography and plasma deposition techniques allows tailoring of the structural and chemical parameters of the crystal surfaces. In this way, it has been possible to tune the plasmonic resonance spectral position close to the excitation wavelength of the monochromatic laser light source in order to maximize the enhancing properties of the substrate. Samples are characterized by scanning electron microscopy and reflectance measurements and tested for SERS activity using malachite green. Besides, as the developed substrate had been prepared on a simple glass slide, SERS detection from the support side is also demonstrated. The optimized substrate is functionalized with thiol-modified capture oligonucleotides, and concentration-dependent signal of the target nucleotide is detected in a sandwich assay with labeled gold nanoparticles. Gold nanoparticles functionalized with different DNA and various Raman reporters are applied in a microarray-based assay recognizing a disease biomarker (Wilms tumor gene) and housekeeping gene expressions in the same time on spatially separated microspots. The multiplexing performance of the SERS-based bioassay is illustrated by distinguishing Raman dyes based on their complex spectral fingerprints.

  7. Investigation on the adsorption characteristics of sodium benzoate and taurine on gold nanoparticle film by ATR-FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Fourier transform infrared (FTIR) spectroscopic studies of sodium benzoate and taurine adsorbed on gold nanoparticle (AuNp) film on silanised glass slides have been studied by attenuated total reflection technique (ATR). The surface morphology of the AuNp films has been measured by Atomic Force Microscopy. The ATR spectra of sodium benzoate and taurine deposited on AuNp film are compared with ATR spectra of their powdered bulk samples. A new red-shifted band appeared along with the symmetric and asymmetric stretches of carboxylate group of sodium benzoate leading to a broadening of the above peaks. Similar behavior is also seen in the case of symmetric and asymmetric stretches of sulphonate group of taurine. The results indicate presence of both chemisorbed and physisorbed layers of both sodium benzoate and taurine on the AuNp film with bottom layer chemically bound to AuNp through carboxylate and sulphonate groups respectively.

  8. Preservation of Thermal Control Specular Gold Baffle Surface on the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) Electronics Compartment (IEC)

    NASA Technical Reports Server (NTRS)

    MonteedeGarcia, Kristina; Patel, Jignasha; Perry, Radford, III

    2010-01-01

    Extremely tight thermal control property degradation allowances on the vapor-deposited, gold-coated IEC baffle surface, made necessary by the cryogenic JWST Observatory operations, dictate tight contamination requirements on adjacent surfaces. Theoretical degradation in emittance with contaminant thickness was calculated. Maximum allowable source outgassing rates were calculated using worst case view factors from source to baffle surface. Tight requirements pushed the team to change the design of the adjacent surfaces to minimize the outgassing sources

  9. Interaction of the CLPFFD peptide with gold nanospheres. A Raman, surface enhanced Raman scattering and theoretical study.

    PubMed

    Vera, A M; Cárcamo, J J; Aliaga, A E; Gómez-Jeria, J S; Kogan, M J; Campos-Vallette, M M

    2015-01-01

    In a previous work we demonstrated that toxic aggregates of the protein β-amyloid (ATAβ) involved in the Alzheimer's disease (AD) can be destabilized upon electromagnetic irradiation of the peptide Cys-Leu-Pro-Phe-Phe-Asp (CLPFFD) adsorbed on gold nanospheres (AuNSs). For a selective recognition of the therapeutic target (i.e. ATAβ) of AD by the conjugates peptide-nanoparticle it is relevant to understand how the interaction between attached ligands and nanoparticles occurs. In this work a surface enhanced Raman scattering spectroscopy (SERS) study of the interactions of CLPFFD with AuNSs of 10nm average diameter was carried out. The SERS data suggest that phenylalanine displays its aromatic ring coplanar to the surface which is supported by theoretical data obtained from molecular mechanics (MM) and Extended Hückel Theory (EHT) calculations.

  10. Surface plasmon resonances in periodic and random patterns of gold nano-disks for broadband light harvesting.

    PubMed

    Nishijima, Yoshiaki; Rosa, Lorenzo; Juodkazis, Saulius

    2012-05-01

    We analyze the localized surface plasmon resonance spectra of periodic square lattice arrays of gold nano-disks, and we describe numerically and experimentally the effect of disorder on resonance width, spectrum, and EM field enhancement in increasingly randomized patterns. The periodic structure shows a narrower and stronger extinction peak, conversely we observe an increase of up to (1-2)×10(2) times enhancement as the disorder is gradually introduced. This allows for simpler, lower resolution fabrication, cost-effective in light harvesting for solar cell and sensing applications. We show that dipole-dipole interactions contribute to diffract light parallel to the surface as a mean of long-range coupling between the nano-disks. PMID:22565766

  11. Interaction of the CLPFFD peptide with gold nanospheres. A Raman, surface enhanced Raman scattering and theoretical study

    NASA Astrophysics Data System (ADS)

    Vera, A. M.; Cárcamo, J. J.; Aliaga, A. E.; Gómez-Jeria, J. S.; Kogan, M. J.; Campos-Vallette, M. M.

    2015-01-01

    In a previous work we demonstrated that toxic aggregates of the protein β-amyloid (ATAβ) involved in the Alzheimer's disease (AD) can be destabilized upon electromagnetic irradiation of the peptide Cys-Leu-Pro-Phe-Phe-Asp (CLPFFD) adsorbed on gold nanospheres (AuNSs). For a selective recognition of the therapeutic target (i.e. ATAβ) of AD by the conjugates peptide-nanoparticle it is relevant to understand how the interaction between attached ligands and nanoparticles occurs. In this work a surface enhanced Raman scattering spectroscopy (SERS) study of the interactions of CLPFFD with AuNSs of 10 nm average diameter was carried out. The SERS data suggest that phenylalanine displays its aromatic ring coplanar to the surface which is supported by theoretical data obtained from molecular mechanics (MM) and Extended Hückel Theory (EHT) calculations.

  12. Gold nanoshell-decorated silicone surfaces for the near-infrared (NIR) photothermal destruction of the pathogenic bacterium E. faecalis.

    PubMed

    Khantamat, Orawan; Li, Chien-Hung; Yu, Fei; Jamison, Andrew C; Shih, Wei-Chuan; Cai, Chengzhi; Lee, T Randall

    2015-02-25

    Catheter-related infections (CRIs) are associated with the formation of pathogenic biofilms on the surfaces of silicone catheters, which are ubiquitous in medicine. These biofilms provide protection against antimicrobial agents and facilitate the development of bacterial resistance to antibiotics. The application of photothermal agents on catheter surfaces is an innovative approach to overcoming biofilm-generated CRIs. Gold nanoshells (AuNSs) represent a promising photothermal tool, because they can be used to generate heat upon exposure to near-infrared (NIR) radiation, are biologically inert at physiological temperatures, and can be engineered for the photothermal ablation of cells and tissue. In this study, AuNSs functionalized with carboxylate-terminated organosulfur ligands were attached to model catheter surfaces and tested for their effectiveness at killing adhered Enterococcus faecalis (E. faecalis) bacteria. The morphology of the AuNSs was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Furthermore, optical and photothermal properties were acquired by ultraviolet-visible (UV-vis) spectroscopy and thermographic imaging with an infrared camera, respectively. Bacterial survival studies on AuNS-modified surfaces irradiated with and without NIR light were evaluated using a colony-formation assay. These studies demonstrated that AuNS-modified surfaces, when illuminated with NIR light, can effectively kill E. faecalis on silicone surfaces. PMID:25611157

  13. Gold nanoshell-decorated silicone surfaces for the near-infrared (NIR) photothermal destruction of the pathogenic bacterium E. faecalis.

    PubMed

    Khantamat, Orawan; Li, Chien-Hung; Yu, Fei; Jamison, Andrew C; Shih, Wei-Chuan; Cai, Chengzhi; Lee, T Randall

    2015-02-25

    Catheter-related infections (CRIs) are associated with the formation of pathogenic biofilms on the surfaces of silicone catheters, which are ubiquitous in medicine. These biofilms provide protection against antimicrobial agents and facilitate the development of bacterial resistance to antibiotics. The application of photothermal agents on catheter surfaces is an innovative approach to overcoming biofilm-generated CRIs. Gold nanoshells (AuNSs) represent a promising photothermal tool, because they can be used to generate heat upon exposure to near-infrared (NIR) radiation, are biologically inert at physiological temperatures, and can be engineered for the photothermal ablation of cells and tissue. In this study, AuNSs functionalized with carboxylate-terminated organosulfur ligands were attached to model catheter surfaces and tested for their effectiveness at killing adhered Enterococcus faecalis (E. faecalis) bacteria. The morphology of the AuNSs was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Furthermore, optical and photothermal properties were acquired by ultraviolet-visible (UV-vis) spectroscopy and thermographic imaging with an infrared camera, respectively. Bacterial survival studies on AuNS-modified surfaces irradiated with and without NIR light were evaluated using a colony-formation assay. These studies demonstrated that AuNS-modified surfaces, when illuminated with NIR light, can effectively kill E. faecalis on silicone surfaces.

  14. Surface plasmon resonance enhanced real-time photoelectrochemical protein sensing by gold nanoparticle-decorated TiO₂ nanowires.

    PubMed

    Da, Peimei; Li, Wenjie; Lin, Xuan; Wang, Yongcheng; Tang, Jing; Zheng, Gengfeng

    2014-07-01

    Recently developed photoelectrochemical (PEC) sensing systems represent a unique potential detection method for real-time analysis of chemical/biological molecules, while the low absorption of TiO2 nanomaterials in the visible wavelength region and the slow surface charge transfer efficiency limit the ultimate sensitivity. Here we develop a gold nanoparticle-decorated TiO2 nanowire sensor for PEC detection of protein binding. The direct attachment of Au nanoparticles to TiO2 nanowires offers strong surface plasmon resonance for electrochemical field effect amplification, yielding a ~100% increase of photocurrent density. In addition, the surface functionalization of gold nanoparticles allows for direct capturing of target proteins near the Au/TiO2 interface and thus substantially enhances the capability of attenuation of energy coupling between Au and TiO2, leading to much-improved sensor performance. As a proof of concept, cholera toxin subunit B has been robustly detected by the TiO2-Au nanowire sensor functionalized with ganglioside GM1, with a high sensitivity of 0.167 nM and excellent selectivity. Furthermore, the real-time feature of photoelectrochemical sensing enables direct measurement of binding kinetics between cholera toxin subunit B and GM1, yielding association and disassociation rate constants and an equilibrium constant K(d) of 4.17 nM. This surface plasmon resonance-enhanced real-time, photoelectrochemical sensing design may lead to exciting biodetection capabilities with high sensitivity and real-time kinetic studies. PMID:24915128

  15. Resistivity of thin gold films on mica induced by electron-surface scattering: Application of quantitative scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Robles, Marcelo E.; Gonzalez-Fuentes, Claudio A.; Henriquez, Ricardo; Kremer, German; Moraga, Luis; Oyarzun, Simón; Suarez, Marco Antonio; Flores, Marcos; Munoz, Raul C.

    2012-02-01

    We report a comparison between the resistivity measured on thin gold films deposited on mica, with predictions based upon classical theories of size effects (Drude's, Sondheimer's and Calecki's), as well as predictions based upon quantum theories of electron-surface scattering (the modified theory of Sheng, Xing and Wang, the theory of Tesanovic, Jaric and Maekawa, and that of Trivedi and Aschroft). From topographic images of the surface recorded with a Scanning Tunneling Microscope, we determined the rms roughness amplitude, δ and the lateral correlation length, ξ corresponding to a Gaussian representation of the average height-height autocorrelation function, describing the roughness of each sample in the scale of length set by the Fermi wave length. Using (δ, ξ) as input data, we present a rigorous comparison between resistivity data and predictions based upon the theory of Calecki as well as quantum theoretical predictions without adjustable parameters. The resistivity was measured on gold films of different thickness evaporated onto mica substrates, between 4 K and 300 K. The resistivity data covers the range 0.1 < x(T) < 6.8, for 4 K < T < 300 K, where x(T) is the ratio between film thickness and electron mean free path in the bulk at temperature T. We experimentally identify electron-surface and electron-phonon scattering as the microscopic electron scattering mechanisms giving rise to the macroscopic resistivity. The different theories are all capable of estimating the thin film resistivity to an accuracy better than 10%; however the mean free path and the resistivity characterizing the bulk turn out to depend on film thickness. Surprisingly, only the Sondheimer theory and its quantum version, the modified theory of Sheng, Xing and Wang, predict and increase in resistivity induced by size effects that seems consistent with published galvanomagnetic phenomena also arising from electron-surface scattering measured at low temperatures.

  16. Investigation of UV Laser Triggered, Nanosecond, Surface Flashover Switches

    SciTech Connect

    Nunnally, W C; Neurath, R; Holmes, C; Sampayan, S; Caporaso, G

    2003-06-03

    Triggered, multi-channel, surface discharges or surface flashover switching have been investigated as a low inductance, low pulse rate switch for conducting large currents. This paper discusses the investigation of UV (355 nm) laser triggered, single channel, low inductance, ns closure and sub-ns jitter switches for applications in switching high dielectric constant, compact pulse forming lines into accelerator loads. The experimental arrangement for evaluating the switch performance and for measuring the high field dielectric constant of the pulse forming lines is presented. Experimental results of delay and jitter measurements versus optical energy on the flashover surface and dc electric field charge.

  17. Exploration of the growth process of ultrathin silica shells on the surface of gold nanorods by the localized surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Li, Chong; Li, Yujie; Ling, Yunyang; Lai, Yangwei; Wu, Chuanliu; Zhao, Yibing

    2014-01-01

    Ultrathin silica coating (UTSC) has emerged as an effective way to improve the compatibility and stability of nanoparticles without attenuating their intrinsic optical properties. Exploration strategies to probe the growth process of ultrathin silica shells on the surface of nanoparticles would represent a valuable innovation that would benefit the development of ultrathin silica coated nanoparticles and their relevant applications. In this work, we report a unique, very effective and straightforward strategy for probing the growth of ultrathin silica shells on the surface of gold nanorods (Au NRs), which exploits the localized surface plasmon resonance (LSPR) as a reporting signal. The thickness of the ultrathin silica shells on the surface of Au NRs can be quantitatively measured and predicted in the range of 0.5-3.5 nm. It is demonstrated that the LSPR shift accurately reflects the real-time change in the thickness of the ultrathin silica shells on Au NRs during the growth process. By using the developed strategy, we further analyze the growth of UTSC on the surface of Au NRs via feeding of Na2SiO3 in a stepwise manner. The responsiveness analysis of LSPR also provides important insight into the shielding effect of UTSC on the surface of Au NRs that is not accessible with conventional strategies. This LSPR-based strategy permits exploration of the surface-mediated sol-gel reactions of silica from a new point of view.

  18. Coupled Molecular Switching Processes in Ordered Mono- and Multilayers of Stimulus-Responsive Rotaxanes on Gold Surfaces

    PubMed Central

    2015-01-01

    Interfaces provide the structural basis for function as, for example, encountered in nature in the membrane-embedded photosystem or in technology in solar cells. Synthetic functional multilayers of molecules cooperating in a coupled manner can be fabricated on surfaces through layer-by-layer self-assembly. Ordered arrays of stimulus-responsive rotaxanes undergoing well-controlled axle shuttling are excellent candidates for coupled mechanical motion. Such stimulus-responsive surfaces may help integrate synthetic molecular machines in larger systems exhibiting even macroscopic effects or generating mechanical work from chemical energy through cooperative action. The present work demonstrates the successful deposition of ordered mono- and multilayers of chemically switchable rotaxanes on gold surfaces. Rotaxane mono- and multilayers are shown to reversibly switch in a coupled manner between two ordered states as revealed by linear dichroism effects in angle-resolved NEXAFS spectra. Such a concerted switching process is observed only when the surfaces are well packed, while less densely packed surfaces lacking lateral order do not exhibit such effects. PMID:25782057

  19. Using localized surface plasmon resonances to probe the nanoscopic origins of adsorbate-driven ordering transitions of liquid crystals in contact with chemically functionalized gold nanodots.

    PubMed

    Koenig, Gary M; Gettelfinger, Brian T; de Pablo, Juan J; Abbott, Nicholas L

    2008-08-01

    We report that localized surface plasmon resonances (LSPRs) of gold nanodots immersed under liquid crystals (LCs) can be used to characterize adsorbate-induced ordering transitions of the LCs on the surfaces of the nanodots. The nanoscopic changes in ordering of the LCs, as measured by LSPR, were shown to give rise to macroscopic ordering transitions of the LCs that were observed by polarized light microscopy. The results reported herein suggest that (i) LCs may be useful for enhancing the sensitivity of LSPR-based detection of binding events and (ii) that LSPR measurements of gold nanodots provide a means to characterize the nanoscopic origins of macroscopic, adsorbate-induced LC ordering transitions.

  20. Cancer cells assemble and align gold nanorods conjugated to antibodies to produce highly enhanced, sharp, and polarized surface Raman spectra: a potential cancer diagnostic marker.

    PubMed

    Huang, Xiaohua; El-Sayed, Ivan H; Qian, Wei; El-Sayed, Mostafa A

    2007-06-01

    Human oral cancer cells are found to assemble and align gold nanorods conjugated to anti-epidermal growth factor receptor (anti-EGFR) antibodies. Immnoconjugated gold nanorods and nanospheres were shown previously to exhibit strong Rayleigh (Mie) scattering useful for imaging. In the present letter, molecules near the nanorods on the cancer cells are found to give a Raman spectrum that is greatly enhanced (due to the high surface plasmon field of the nanorod assembly in which their extended surface plasmon fields overlap), sharp (due to a homogeneous environment), and polarized (due to anisotropic alignments). These observed properties can be used as diagnostic signatures for cancer cells.

  1. Investigation of arsenic species in tailings and windblown dust from a gold mining area.

    PubMed

    Ono, F B; Tappero, R; Sparks, D; Guilherme, L R G

    2016-01-01

    Research has shown the presence of high levels of arsenic (up to 2666 mg As kg(-1)) in tailings from a gold mining area of Brazil. This is an important point of attention, generating concerns about impacts on human health. Yet, a recent study showed that As bioaccessibility in the same area was very low (<4.4%). Thus, determination of the direct solid-phase speciation of As in the mine tailings and windblown dust is needed to explain this low bioaccessibility. Mine samples were collected from four subareas and windblown dust from eight sites. Synchrotron-based bulk-X-ray absorption near-edge structure (bulk-XANES) spectroscopy, micro-X-ray absorption near-edge structure (μ-XANES), and μ-X-ray fluorescence (μ-SXRF) spectroscopy were applied to determine As speciation. Bulk-XANES spectra indicated that As occurs as the As(V) oxidation state. Micro-XANES and μ-SXRF analyses revealed that As was also present as arsenopyrite (FeAsS) and its weathering products, but mostly it was As(V) as poorly crystalline ferric arsenate. This supports the findings of low bioaccessible As and highlights the importance of Fe oxides in immobilizing As in the terrestrial environment. All air particulate samples exhibited As-rich particles (up to 313 mg As kg(-1)). The air particulates exhibited solid-phase As species very similar to those found in the mine samples, which indicates that As in the windblown dust is not easily available.

  2. Protein-coated pH-responsive gold nanoparticles: Microwave-assisted synthesis and surface charge-dependent anticancer activity

    PubMed Central

    Joseph, Dickson; Tyagi, Nisha; Geckeler, Christian

    2014-01-01

    Summary The biocompatibility and ease of functionalization of gold nanoparticles underlie significant potential in biotechnology and biomedicine. Eight different proteins were examined in the preparation of gold nanoparticles (AuNPs) in aqueous medium under microwave irradiation. Six of the proteins resulted in the formation of AuNPs. The intrinsic pH of the proteins played an important role in AuNPs with strong surface plasmon bands. The hydrodynamic size of the nanoparticles was larger than the values observed by TEM and ImageJ. The formation of a protein layer on the AuNPs accounts for this difference. The AuNPs exhibited sensitivity towards varying pH conditions, which was confirmed by determining the difference in the isoelectric points studied by using pH-dependent zeta potential titration. Cytotoxicity studies revealed anticancerous effects of the AuNPs at a certain micromolar concentration by constraining the growth of cancer cells with different efficacies due to the use of different proteins as capping agents. The positively charged AuNPs are internalized by the cells to a greater level than the negatively charged AuNPs. These AuNPs synthesized with protein coating holds promise as anticancer agents and would help in providing a new paradigm in area of nanoparticles. PMID:25247128

  3. Protein-coated pH-responsive gold nanoparticles: Microwave-assisted synthesis and surface charge-dependent anticancer activity.

    PubMed

    Joseph, Dickson; Tyagi, Nisha; Geckeler, Christian; E Geckeler, Kurt

    2014-01-01

    The biocompatibility and ease of functionalization of gold nanoparticles underlie significant potential in biotechnology and biomedicine. Eight different proteins were examined in the preparation of gold nanoparticles (AuNPs) in aqueous medium under microwave irradiation. Six of the proteins resulted in the formation of AuNPs. The intrinsic pH of the proteins played an important role in AuNPs with strong surface plasmon bands. The hydrodynamic size of the nanoparticles was larger than the values observed by TEM and ImageJ. The formation of a protein layer on the AuNPs accounts for this difference. The AuNPs exhibited sensitivity towards varying pH conditions, which was confirmed by determining the difference in the isoelectric points studied by using pH-dependent zeta potential titration. Cytotoxicity studies revealed anticancerous effects of the AuNPs at a certain micromolar concentration by constraining the growth of cancer cells with different efficacies due to the use of different proteins as capping agents. The positively charged AuNPs are internalized by the cells to a greater level than the negatively charged AuNPs. These AuNPs synthesized with protein coating holds promise as anticancer agents and would help in providing a new paradigm in area of nanoparticles.

  4. Protein-coated pH-responsive gold nanoparticles: Microwave-assisted synthesis and surface charge-dependent anticancer activity.

    PubMed

    Joseph, Dickson; Tyagi, Nisha; Geckeler, Christian; E Geckeler, Kurt

    2014-01-01

    The biocompatibility and ease of functionalization of gold nanoparticles underlie significant potential in biotechnology and biomedicine. Eight different proteins were examined in the preparation of gold nanoparticles (AuNPs) in aqueous medium under microwave irradiation. Six of the proteins resulted in the formation of AuNPs. The intrinsic pH of the proteins played an important role in AuNPs with strong surface plasmon bands. The hydrodynamic size of the nanoparticles was larger than the values observed by TEM and ImageJ. The formation of a protein layer on the AuNPs accounts for this difference. The AuNPs exhibited sensitivity towards varying pH conditions, which was confirmed by determining the difference in the isoelectric points studied by using pH-dependent zeta potential titration. Cytotoxicity studies revealed anticancerous effects of the AuNPs at a certain micromolar concentration by constraining the growth of cancer cells with different efficacies due to the use of different proteins as capping agents. The positively charged AuNPs are internalized by the cells to a greater level than the negatively charged AuNPs. These AuNPs synthesized with protein coating holds promise as anticancer agents and would help in providing a new paradigm in area of nanoparticles. PMID:25247128

  5. CW-laser-induced morphological changes of a single gold nanoparticle on glass: observation of surface evaporation.

    PubMed

    Setoura, Kenji; Okada, Yudai; Hashimoto, Shuichi

    2014-12-28

    Pulsed-laser heating of colloidal noble-metal nanoparticles in an aqueous solution induces morphological changes such as size reduction. However, the technique suffers disadvantages through polydispersed products. Here, we show that continuous-wave (CW) laser heating of single gold nanoparticles is capable of generating particles of smaller diameters with superb control in terms of exposure time and intensity. We show, based on calculations of particle temperatures under illumination, that surface evaporation below the boiling point of bulk gold occurs, resulting in a gradual diameter decrease in air. In our experiment, a focused illumination of Au NPs through an objective lens of a microscope provided peak-power densities (10(6)-10(7) W cm(-2)) equivalent to that of a typical nanosecond laser. Nevertheless the heating rate under CW laser illumination is much lower than that under pulsed-laser illumination, resulting in better control over nanoparticle heating and related morphological changes. Furthermore, the single-particle study of such heating helps us to clarify the evolution of such changes to a given particle.

  6. Scattering of electrically excited surface plasmon polaritons by gold nanoparticles studied by optical interferometry with a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Rogez, Benoît.; Comtet, Geneviève; Le Moal, Eric; Abidi, Wafa; Remita, Hynd; Dujardin, Gérald; Boer-Duchemin, Elizabeth

    2015-07-01

    We study the scattering of electrically excited surface plasmon polaritons (SPP) from individual nanostructures. The tunneling electrons from a scanning tunneling microscope (STM) are used to excite an out-going, circular SPP wave on a thin (50-nm) gold film on which isolated gold nanoparticles (NPs) have been deposited. Interaction of the excited SPPs with the NPs leads to both in-plane (SPP-to-SPP) and out-of-plane (SPP-to-photon) scattering. We use SPP leakage radiation microscopy to monitor the interference between the incident and in-plane scattered SPP waves in the image plane. By changing the location of the STM tip, the distance of the pointlike SPP source to the scatterers can be varied at will, which constitutes a key advantage over other existing techniques. As well, the out-of-plane scattered radiation interferes with the direct light emission from the STM tip in the back focal plane (Fourier plane). This confirms the mutual coherence of the light and SPP emission resulting from the inelastic tunneling of an electron in the STM junction. We use this effect to demonstrate that SPP-to-photon scattering at NPs is highly directional.

  7. Surface plasmon spectroscopy study of electron exchange between single gold nanorods and metal oxide matrix during hydrogen gas sensing (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Cittadini, Michela; Collins, Sean; Mulvaney, Paul; Martucci, Alessandro

    2015-08-01

    The direct optical monitoring of electron exchange on single plasmonic nanoparticles, involved in chemical reactions with gas molecules, is one of the main challenges in the heterogeneous catalysis and gas sensing fields. Catalysts are substances that speed up reactions by providing an alternative pathway with lower activation energy than that required for the uncatalysed reaction. A lot of research, both fundamental and applied, has been carried out to investigate how catalysts work and to increase their efficiency. The present work shows how the use of Dark Field Microscopy (DFM) coupled with surface plasmon spectroscopy, enables the direct observation of the kinetics of H2 gas interaction with single gold nanorods (NR) coupled with Pt nanoparticles (NPs) and/or with metal oxide matrices. The plasmonic particles, gold NRs, act as optical probes, and enable the monitoring of the electron exchange through the measurement of their surface plasmon resonance (SPR) band shift. To improve the redox reaction kinetics, the Au NRs have been coupled with Pt NPs and embedded also into a TiO2 or ZnO low scattering matrix. The Au NRs, the Pt, TiO2 and ZnO NPs have been synthetized by colloid chemistry. Several samples made of bare Au NRs, or Au NRs coupled with only Pt NPs or with Pt and TiO2 NPs or with Pt and TiO2 have been deposited by spin coating on silica substrates. The longitudinal Au SPR band shift has been monitored by DFM looking at the variation of the scattering spectrum of a single Au NRs in the presence of H2. Time-resolved measurements have been also conducted at fixed wavelength in order to monitor the kinetics of the H2 reaction. With such measurements it was possible to elucidate the importance of the adsorbed oxygen and the TiO2 matrix on the H2 reaction with the Pt NPs.

  8. Gold glyconanoparticles: synthetic polyvalent ligands mimicking glycocalyx-like surfaces as tools for glycobiological studies.

    PubMed

    Barrientos, Africa G; de la Fuente, Jesús M; Rojas, Teresa C; Fernández, Asunción; Penadés, Soledad

    2003-05-01

    A simple and versatile methodology is described for tailoring sugar-functionalised gold nanoclusters (glyconanoparticles) that have 3D polyvalent carbohydrate display and globular shapes. This methodology allows the preparation of glyconanoparticles with biologically significant oligosaccharides as well as with differing carbohydrate density. Fluorescent glyconanoparticles have been also prepared for labelling cells in biological tests. The materials are water soluble, stable under physiological conditions and present an exceptional small core size. All of them have been characterised by (1)H NMR, UV and IR spectroscopy, TEM and elemental analysis. Their highly polyvalent network can mimic glycosphingolipid clustering and interactions at the plasma membrane, providing an controlled system for glycobiological studies. Furthermore, they are useful building blocks for the design of nanomaterials. PMID:12740837

  9. Conductive-probe AFM characterization of graphene sheets bonded to gold surfaces

    NASA Astrophysics Data System (ADS)

    Hauquier, Fanny; Alamarguy, David; Viel, Pascal; Noël, Sophie; Filoramo, Arianna; Huc, Vincent; Houzé, Frédéric; Palacin, Serge

    2012-01-01

    Conducting probe atomic force microscopy (CP-AFM) has been used to perform mechanical and electrical experiments on graphene layers bonded to polyaminophenylene (PAP) films grafted on gold substrates. This technique is a new approach for the characterization of graphene sheets and represents a complementary tool to Raman spectroscopy. The combination of friction and electrical imaging reveals that different stacked graphene sheets have been successfully distinguished from each other and from the underlying PAP films. Lateral force microscopy has shown that the friction is greatly reduced on graphene sheets in comparison with the organic coating. The electrical resistance images show very different local conduction properties which can be linked to the number of underlying graphene sheets. The resistance decreases very slowly when the normal load increases. Current-voltage curves display characteristics of metal-molecule-metal junctions.

  10. Gold glyconanoparticles: synthetic polyvalent ligands mimicking glycocalyx-like surfaces as tools for glycobiological studies.

    PubMed

    Barrientos, Africa G; de la Fuente, Jesús M; Rojas, Teresa C; Fernández, Asunción; Penadés, Soledad

    2003-05-01

    A simple and versatile methodology is described for tailoring sugar-functionalised gold nanoclusters (glyconanoparticles) that have 3D polyvalent carbohydrate display and globular shapes. This methodology allows the preparation of glyconanoparticles with biologically significant oligosaccharides as well as with differing carbohydrate density. Fluorescent glyconanoparticles have been also prepared for labelling cells in biological tests. The materials are water soluble, stable under physiological conditions and present an exceptional small core size. All of them have been characterised by (1)H NMR, UV and IR spectroscopy, TEM and elemental analysis. Their highly polyvalent network can mimic glycosphingolipid clustering and interactions at the plasma membrane, providing an controlled system for glycobiological studies. Furthermore, they are useful building blocks for the design of nanomaterials.

  11. Accelerated colorimetric immunosensing using surface-modified porous monoliths and gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Chuag, Shao-Hsuan; Chen, Guan-Hua; Chou, Hsin-Hao; Shen, Shu-Wei; Chen, Chien-Fu

    2013-08-01

    A rapid and sensitive immunoassay platform integrating polymerized monoliths and gold nanoparticles (AuNPs) has been developed. The porous monoliths are photopolymerized in situ within a silica capillary and serve as solid support for high-mass transport and high-density capture antibody immobilization to create a shorter diffusion length for antibody-antigen interactions, resulting in a rapid assay and low reagent consumption. AuNPs are modified with detection antibodies and are utilized as signals for colorimetric immunoassays without the need for enzyme, substrate and sophisticated equipment for quantitative measurements. This platform has been verified by performing a human IgG sandwich immunoassay with a detection limit of 0.1 ng ml-1. In addition, a single assay can be completed in 1 h, which is more efficient than traditional immunoassays that require several hours to complete.

  12. Electric Switching of Fluorescence Decay in Gold-Silica-Dye Nematic Nanocolloids Mediated by Surface Plasmons.

    PubMed

    Jiang, Li; Mundoor, Haridas; Liu, Qingkun; Smalyukh, Ivan I

    2016-07-26

    Tunable composite materials with interesting physical behavior can be designed through integrating unique optical properties of solid nanostructures with facile responses of soft matter to weak external stimuli, but this approach remains challenged by their poorly controlled coassembly at the mesoscale. Using scalable wet chemical synthesis procedures, we fabricated anisotropic gold-silica-dye colloidal nanostructures and then organized them into the device-scale (demonstrated for square-inch cells) electrically tunable composites by simultaneously invoking molecular and colloidal self-assembly. We show that the ensuing ordered colloidal dispersions of shape-anisotropic nanostructures exhibit tunable fluorescence decay rates and intensity. We characterize how these properties depend on low-voltage fields and polarization of both the excitation and emission light, demonstrating a great potential for the practical realization of an interesting breed of nanostructured composite materials. PMID:27391876

  13. Deformation of the surface of gallium arsenide during the deposition of gold

    SciTech Connect

    Briantseva, T. A. Lioubtchenko, D. V.; Markov, I. A.; Ten, Yu. A.

    2011-12-15

    Deformation phenomena of near-surface GaAs layers are studied using surface acoustic waves during the deposition of Au and the irradiation of the semiconductor surface by the light of a heated evaporator. It is shown that, in the case of Au deposition, the near-surface layers are plasticized due to the phase transformations in the Au-Ga-As system, while upon irradiation of the GaAs surface with light, a coarse-grained layer with liquid-like interlayers is formed. As a result, the type of surface deformations and their relaxation time change. The integral temporal characteristics of the surface acoustic wave, such as the variation integrals of its rate and dissipated power, reflect the processes occurring on the surface in the real-time mode. In summary, they reflect the current magnitude of the resulting deformation. The parameters of occurring processes such as activation energy and relaxation time are determined.

  14. Scattering of surface plasmon-polaritons and volume waves by a rough gold film.

    PubMed

    Sterligov, V A; Grytsaienko, I A; Men, Y

    2016-08-15

    A discrepancy between the theories of volume and surface plasmon-polaritons (SPPs) wave scattering was found. Its tentative explanation is related to the resonance-like emission of SPPs energy due to SPPs diffraction by a surface relief Fourier decomposition component. It was also shown that the sum of surface wave scattered intensity along a plane of incidence is proportional to surface roughness value. PMID:27519069

  15. Exceptionally Slow Movement of Gold Nanoparticles at a Solid/Liquid Interface Investigated by Scanning Transmission Electron Microscopy.

    PubMed

    Verch, Andreas; Pfaff, Marina; de Jonge, Niels

    2015-06-30

    Gold nanoparticles were observed to move at a liquid/solid interface 3 orders of magnitude slower than expected for the movement in a bulk liquid by Brownian motion. The nanoscale movement was studied with scanning transmission electron microscopy (STEM) using a liquid enclosure consisting of microchips with silicon nitride windows. The experiments involved a variation of the electron dose, the coating of the nanoparticles, the surface charge of the enclosing membrane, the viscosity, and the liquid thickness. The observed slow movement was not a result of hydrodynamic hindrance near a wall but instead explained by the presence of a layer of ordered liquid exhibiting a viscosity 5 orders of magnitude larger than a bulk liquid. The increased viscosity presumably led to a dramatic slowdown of the movement. The layer was formed as a result of the surface charge of the silicon nitride windows. The exceptionally slow motion is a crucial aspect of electron microscopy of specimens in liquid, enabling a direct observation of the movement and agglomeration of nanoscale objects in liquid.

  16. Propitious Immobilization of Gold Nanoparticles on Poly(dimethylsiloxane) Substrate for Local Surface Plasmon Resonance Based Biosensor

    NASA Astrophysics Data System (ADS)

    Trung, Nguyen Ba; Yoshikawa, Hiroyuki; Tamiya, Eiichi; Viet, Pham Hung; Takamura, Yuzuru; Ashahi, Tsuyoshi

    2012-03-01

    In this work, a simple method for fabricating gold nanoparticle (AuNP) layer on a poly(dimethylsiloxane) (PDMS) substrate based on electrostatic deposition of AuNP colloid onto a chemically-modified PDMS surface using 3-aminopropyltriethoxysilane (γ-APTES) was developed. AuNPs of 100 nm diameter were successfully dispersed and deposited onto the chemically-modified PDMS surface. The morphology and optical property of the AuNP layer were examined by atomic force microscopy (AFM) and UV-visible absorption spectroscopy, respectively. It was found that the prepared AuNP layer on PDMS could work as a localized surface plasma resonance (LSPR) sensor. The sensing characteristics were examined by changing the refractive index of solution surrounding the AuNP and antigen-antibody events on the AuNP surface. Changes in absorbance intensity and peak wavelength shift of the LSPR band were both clearly observed. The developed technique can hopefully expand the applications of PDMS for not only micro channel fabrication, but also sensing construction for easier and simpler preparation of microfluidic biosensors, which were then applied for immunoassays and other biochemical analyses.

  17. A computational study on surface-enhanced Raman spectroscopy of para-substituted Benzenethiol derivatives adsorbed on gold nanoclusters.

    PubMed

    You, Tingting; Liang, Xiu; Gao, Yukun; Yin, Penggang; Guo, Lin; Yang, Shihe

    2016-01-01

    We presented a computational study on para-substituted Benzenethiol (x-BT, x=H, F, Cl, Br, OH, SH, SeH, NH2, CH3) derivatives interacting with gold cluster for chemical effects related to surface-enhanced Raman spectroscopy (SERS). Density functional theory (DFT) calculations were performed on a series of bridge-type and vertex type x-BT/Au13 complexes for geometric, electronic and excitation properties to determine the key factor in spectral enhancement. Results indicated that off-resonance enhancement factors of bridge-type and vertex-type complexes exhibited different dependency on substitutions, which was greatly influenced by molecule-cluster transitions instead of properties such as interaction energy and charge transfer due to same origination for off-resonance and resonance chemical enhancement.

  18. A localized surface plasmon resonance DNA biosensor based on gold nanospheres coated on the tip of the fiber

    NASA Astrophysics Data System (ADS)

    Jia, Shuo; Bian, Chao; Tong, Jian-hua; Sun, Ji-zhou; Xia, Shan-hong

    2016-03-01

    A localized surface plasmon resonance (LSPR) biosensor was prepared with gold nanospheres (AuNSs) coated on the tip face of the optical silica fiber. AuNSs with the sizes of 20 nm and 80 nm were used. The sensitivities of AuNS20 nm and AuNS80 nm modified sensors to bulk refractive index (RI) variation are 82.86 nm/RIU and 218.98 nm/RIU, respectively. The AuNS80 nm modified sensor was used for the detection of 40 bases DNA hybridization and the limit of detection is 50 nmol/L, where the 40-bases DNA probe was covalently linked with AuNS80 nm. The complementary DNA sequence in tris-acetate-EDTA (TAE) buffer solution was detected as the target DNA. This fiber sensor has the advantages of small sample consumption, easy fabrication and high sensitivity.

  19. Sensitivity enhancement of a grating-based surface plasmon-coupled emission (SPCE) biosensor chip using gold thickness

    NASA Astrophysics Data System (ADS)

    Yuk, Jong Seol; Guignon, Ernest F.; Lynes, Michael A.

    2014-01-01

    We describe a novel approach to enhance the sensitivity of a grating-based surface plasmon-coupled emission (SPCE) sensor by increasing the thickness of the metal film used in this system. The calculated optical properties of grating-based SPR spectra were significantly affected by both grating depth and by gold thickness. Higher angular sensitivity could be achieved at short wavelengths and under in situ measurement (analysis under aqueous condition). We confirmed the predicated enhancements of SPCE response using Alexa Fluor 647-labeled anti-mouse IgG immobilized on the SPCE sensor chips. Grating-coupled SPCE sensor chips can be used as a useful tool for high contents analysis of chemical and biomolecular interactions.

  20. Finite-Difference Time-Domain (FDTD) Modeling of Gold Core-Shell Structures with Different Shell Morphology for Surface-Enhanced Raman Spectroscopy (SERS)

    NASA Astrophysics Data System (ADS)

    Gorunmez, Zohre; Jana, Debrina; He, Jie; Sagle, Laura; Beck, Thomas

    Core-shell (CS) nanostructures have received attention in recent years due to their usefulness in applications ranging from catalysis to cancer treatment. SERS has been shown to be one of the most sensitive techniques for molecular detection, achieving single molecule detection. It has been established that the electromagnetic mechanism (EM) provides the main contribution to SERS enhancement due to the normal Raman spectroscopy arising from coupling of both the incident and re-emitted fields. The FDTD technique has been developed to provide numerical solutions to Maxwell's time-dependent curl equations in order to promise modeling capabilities for EM enhancement of SERS. Herein, we apply this method to the study of three morphologically different gold core-shell nanoparticles to investigate their contributions to SERS. In these structures, the dye/probe molecule resides in between the shell and the core and only the shell morphology is altered. The data shows that the surface plasmon resonances (PRs) influencing the SERS of the probe molecules, due to the coupling of the core and shell, are tunable by changing the shell morphologies and CS structures with sharp features on their surfaces highlight larger enhancements due to stronger localized surface PRs. University of Cincinnati start-up funds, NSF, Ohio Supercomputer Center, and the Ministry of National Education of the Republic of Turkey.