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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. Piezoelectric crystal impedance analysis for investigating the modification processes of protein, cross-linker, and DNA on gold surface

    NASA Astrophysics Data System (ADS)

    Zhou, Anhong; Xie, Qingji; Li, Ping; Nie, Lihua; Yao, Shouzhuo

    2000-05-01

    The processes of surface modification on gold-coated piezoelectric quartz crystal sensor have been in situ investigated by using the impedance analysis technique. The changes of equivalent circuit parameters were used to interpret the different behaviors of successively modifying protein, cross-linker, and DNA onto a gold electrode surface. It was found that the frequency changes due to protein adsorption might be described as a sum of two exponential functions, compared with a first-order kinetic function exhibited in subsequent binding of cross-linker to protein. The kinetic parameters were fitted to these two cases. It was also shown that the DNA molecules binding to cross-linker gave rise to the changes of the density-viscosity and the dielectric constant, both being linearly related to DNA concentration in the liquid when below 6.0 μg m -1.

  6. 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.

  7. The effect of thiolated phospholipids on formation of supported lipid bilayers on gold substrates investigated by surface-sensitive methods.

    PubMed

    Kılıç, Abdulhalim; Fazeli Jadidi, M; Özer, Hakan Özgür; Kök, Fatma Neşe

    2017-09-08

    Most of the model lipid membrane studies on gold involve the usage of various surface-modification strategies to rupture liposomes and induce lipid bilayer formation since liposomes with polar surfaces do not interact with bare, hydrophobic gold. In this study, a thiol-modified phospholipid, 1,2-Dipalmitoyl-sn-Glycero-3-Phosphothioethanol (DPPTE) was incorporated into phosphatidylcholine (PC) based liposomes to form supported lipid bilayer (SLB) on gold surfaces without further modification. The binding kinetics of liposomes with different DPPTE ratio (0.01 to 100%mol/mol) and diameters were monitored by Quartz Crystal Microbalance with Dissipation (QCM-D). The dissipation change per frequency change, i.e. acoustic ratio, which is evaluated as a degree of the viscoelasticity, considerably decreased with the presence of DPPTE (from 162.3GHz(-1) for flattened PC liposomes to ca. 89.5GHz(-1) for 100% DPPTE liposomes) when compared to the results of two reference rigid monolayers and two viscoelastic layers. To assess the quality of SLB platform, the interpretation of QCM-D data was also complemented with Surface Plasmon Resonance. The optimum thiolated-lipid ratio (1%, lower thiol ratio and higher rigidity) was then used to determine the dry-lipid mass deposition, the water content and the thickness values of the SLB via viscoelastic modelling. Further surface characterization studies were performed by Atomic Force Microscopy with high spatial resolution. The results suggested that model membrane was almost continuous with minimum defects but showed more dissipative/soft nature compared to an ideal bilayer due to partially fused liposomes/overlapped lipid bilayers/multilayer islands. These local elevations distorted the planarity and led the increase of overall membrane thickness to ∼7.0nm. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. 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.

  9. Controlled adsorption of cytochrome c to nanostructured gold surfaces

    NASA Astrophysics Data System (ADS)

    Gomes, Inês; Feio, Maria J.; Santos, Nuno C.; Eaton, Peter; Serro, Ana Paula; Saramago, Benilde; Pereira, Eulália; Franco, Ricardo

    2012-12-01

    Controlled electrostatic physisorption of horse heart cytochrome c (Cyt c) onto nanostructured gold surfaces was investigated using Quartz-Crystal Microbalance measurements in planar gold surfaces with or without functionalization using a self-assembled monolayer (SAM) of the alkanethiol mercaptoundecanoic acid (MUA). MUA is a useful functionalization ligand for gold surfaces, shedding adsorbed biomolecules from the excessive electron density of the metal. A parallel analysis was conducted in the corresponding curved surfaces of 15 nm gold nanoparticles (AuNPs), using zeta-potential and UV- visible spectroscopy. Atomic Force Microscopy of both types of functionalized gold surfaces with a MUA SAM, allowed for visualization of Cyt c deposits on the nanostructured gold surface. The amount of Cyt c adsorbed onto the gold surface could be controlled by the solution pH. For the assays conducted at pH 4.5, when MUA SAM- functionalized planar gold surfaces are positive or neutral, and Cyt c has a positive net charge, only 13 % of the planar gold surface area was coated with protein. In contrast, at pH 7.4, when MUA SAM-functionalized planar gold surfaces and Cyt c have opposite charges, a protein coverage of 28 % could be observed implying an adsorption process strongly governed by electrostatic forces. Cyt c adsorption on planar and curved gold surfaces are found to be greatly favored by the presence of a MUA-capping layer. In particular, on the AuNPs, the binding constant is three times larger than the binding constant obtained for the original citrate-capped AuNPs.

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

    PubMed

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

    2013-03-07

    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 HAuCl(4) 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 Au(3+) 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, Au(3+) ions are reduced to Au(0). 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.

  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. 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.

  14. A case study investigating the occurrence of geosmin and 2-methylisoborneol (MIB) in the surface waters of the Hinze Dam, Gold Coast, Australia.

    PubMed

    Uwins, H K; Teasdale, P; Stratton, H

    2007-01-01

    The Hinze Dam is located in the Gold Coast hinterland and is the primary source of water supply for the Gold Coast region. Sporadic and unpredictable taste and odour events caused by geosmin and 2-methylisoborneol (MIB) are an ongoing problem in the Hinze Dam. To investigate potential ecological and physiological triggers of these events, a 12-month surface-sampling regime was undertaken. Concentrations of geosmin, MIB, nitrogen and phosphorus were measured. Algal and cyanobacterial counts were performed. Water temperature, rainfall and dam capacity were also recorded. The occurrence of geosmin was found to correlate significantly with Anabaena numbers, water temperature and dam capacity. The occurrence of MIB correlated with increasing ammonia. No significant correlations were observed with the other nutrients or physical parameters measured. Overall, this study demonstrated that high concentrations of geosmin detected in dam surface waters was strongly correlated with an increase in numbers of Anabaena spp. These events were most likely triggered by significant rainfall causing a pulse in nutrients into the dam, in conjunction with warmer water temperatures.

  15. Gold-Organic Hybrids: On-Surface Synthesis and Perspectives.

    PubMed

    Zhang, Haiming; Chi, Lifeng

    2016-12-01

    Gold-organic hybrids can be prepared on gold substrates by on-surface dehalogenation of molecular precursors with multiple halogen substituents. Various contact geometries of covalent arylAu bonds are achieved by changing the halogen substituents in the bay or peri regions. Scanning tunneling microscopy/spectroscopy (STM/STS) investigations allow a better understanding of the structure/property relationships in various gold-aryl contacts. Recent progress on the synthesis, large-scale alignment, and STS measurement of gold-organic hybrids is described, ending with an emphasis on potential future applications, e.g., as precursors (intermediates) for the synthesis of graphene nanoribbons (GNRs) on insulating surfaces, and as a model system to investigate the role of covalent arylAu bonds in electron transport through gold-GNR contacts.

  16. 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

    2015-03-06

    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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. 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.

  18. 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.

  19. Investigating the specificity of adsorption of onto gold by gold-binding peptides using molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Vila Verde, Ana; Maranas, Janna

    2007-03-01

    It is possible to engineer artificial peptide sequences showing high specificity of adsorption for surfaces like gold, platinum or other solid materials. However, the reasons behind that high specificity are not clear. We investigate the adsorption of a genetically engineered peptide with high gold specificity using all-atom molecular dynamics simulations. Accurate Lennard-Jones parameters describing the interactions of gold with both water and amino acids are not currently available, so thus we discuss assignment of appropriate values. Two sets of simulations are presented: one using peptides made of a gold-binding motif (MHGKTQATSGTIQS) and another using peptides made of a non gold-binding motif (AIRRDVNCIGASMH). Adsorption onto the (111) and the (100) crystalline faces of gold is investigated. We discuss our results in light of the features of the peptide (sequence, charge, structure, nature of the amino acids) that may be responsible for the specificity of the gold-binding motif for gold.

  20. 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.

  1. Adsorption of homopolypeptides on gold investigated using atomistic molecular dynamics.

    PubMed

    Vila Verde, Ana; Beltramo, Peter J; Maranas, Janna K

    2011-05-17

    We investigate the role of dynamics on adsorption of peptides to gold surfaces using all-atom molecular dynamics simulations in explicit solvent. We choose six homopolypeptides [Ala(10), Ser(10), Thr(10), Arg(10), Lys(10), and Gln(10)], for which experimental surface coverages are not correlated with amino acid level affinities for gold, with the idea that dynamic properties may also play a role. To assess dynamics we determine both conformational movement and flexibility of the peptide within a given conformation. Low conformational movement indicates stability of a given conformation and leads to less adsorption than homopolypeptides with faster conformational movement. Likewise, low flexibility within a given conformation also leads to less adsorption. Neither amino acid affinities nor dynamic considerations alone predict surface coverage; rather both quantities must be considered in peptide adsorption to gold surfaces.

  2. 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

  3. Topological states on the gold surface.

    PubMed

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

    2015-12-14

    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.

  4. Gold nanoparticles on polarizable surfaces as Raman scattering antennas.

    PubMed

    Chen, Shiuan-Yeh; Mock, Jack J; Hill, Ryan T; Chilkoti, Ashutosh; Smith, David R; Lazarides, Anne A

    2010-11-23

    Surface plasmons supported by metal nanoparticles are perturbed by coupling to a surface that is polarizable. Coupling results in enhancement of near fields and may increase the scattering efficiency of radiative modes. In this study, we investigate the Rayleigh and Raman scattering properties of gold nanoparticles functionalized with cyanine deposited on silicon and quartz wafers and on gold thin films. Dark-field scattering images display red shifting of the gold nanoparticle plasmon resonance and doughnut-shaped scattering patterns when particles are deposited on silicon or on a gold film. The imaged radiation patterns and individual particle spectra reveal that the polarizable substrates control both the orientation and brightness of the radiative modes. Comparison with simulation indicates that, in a particle-surface system with a fixed junction width, plasmon band shifts are controlled quantitatively by the permittivity of the wafer or the film. Surface-enhanced resonance Raman scattering (SERRS) spectra and images are collected from cyanine on particles on gold films. SERRS images of the particles on gold films are doughnut-shaped as are their Rayleigh images, indicating that the SERRS is controlled by the polarization of plasmons in the antenna nanostructures. Near-field enhancement and radiative efficiency of the antenna are sufficient to enable Raman scattering cyanines to function as gap field probes. Through collective interpretation of individual particle Rayleigh spectra and spectral simulations, the geometric basis for small observed variations in the wavelength and intensity of plasmon resonant scattering from individual antenna on the three surfaces is explained.

  5. Mixed carboranethiol self-assembled monolayers on gold surfaces

    NASA Astrophysics Data System (ADS)

    Yavuz, Adem; Sohrabnia, Nima; Yilmaz, Ayşen; Danışman, M. Fatih

    2017-08-01

    Carboranethiol self-assembled monolayers on metal surfaces have been shown to be very convenient systems for surface engineering. Here we have studied pure and mixed self-assembled monolayers (SAMs) of three different carboranethiol (CT) isomers on gold surfaces. The isomers were chosen with dipole moments pointing parallel to (m-1-carboranethiol, M1), out of (m-9-carboranethiol, M9) and into (o-1-carboranethiol, O1) the surface plane, in order to investigate the effect of dipole moment orientation on the film properties. In addition, influence of the substrate surface morphology on the film properties was also studied by using flame annealed (FA) and template stripped (TS) gold surfaces. Contact angle measurements indicate that in M1/M9 and M1/O1 mixed SAMs, M1 is the dominant species on the surface even for low M1 ratio in the growth solution. Whereas for O1/M9 mixed SAMs no clear evidence could be observed indicating dominance of one of the species over the other one. Though contact angle values were lower and hysteresis values were higher for SAMs grown on TS gold surfaces, the trends in the behavior of the contact angles with changing mixing ratio were identical for SAMs grown on both substrates. Atomic force microscopy images of the SAMs on TS gold surfaces indicate that the films have similar morphological properties regardless of mixing ratio.

  6. Surface-modified gold nanoshells for enhanced cellular uptake.

    PubMed

    Liang, Zhongshi; Liu, Yun; Li, Xiangyang; Wu, Qinge; Yu, Jiahui; Luo, Shufang; Lai, Lihui; Liu, Shunying

    2011-09-15

    Gold nanoshells have shown a great potential for use as agents in a wide variety of biomedical applications, and some of which require the delivery of large numbers of gold nanoshells onto or into the cells. Here, we develop a ready method to enhance the cellular uptake of gold nanoshells by modifying with meso-2,3-dimercaptosuccinic acid (DMSA). The quantifiable technique of inductively coupled plasma atomic emissions spectroscopy (ICP-AES) and transmission electron microscopy (TEM) were used to investigate the cellular uptake of unmodified and DMSA-modified gold nanoshells. Three cell lines (RAW 264.7, A549, and BEL-7402) were involved and the results indicated that the cellular uptake of the DMSA-modified gold nanoshells was obviously enhanced versus the unmodified gold nanoshells. The reason possibly lies in the nonspecific adsorption of serum protein on the DMSA-modified gold nanoshells (DMSA-GNs), which consequently enhanced the cellular uptake. As a continued effort, in vitro experiments with endocytic inhibitors suggested the DMSA-GNs internalized into cells via receptor-mediated endocytosis (RME) pathway. This study has provided a valuable insight into the effects of surface modification on cellular uptake of nanoparticles.

  7. 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.

  8. 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.

  9. Surface Plasmon Polariton Interference in Gold Nanoplates.

    PubMed

    Beane, Gary; Yu, Kuai; Devkota, Tuphan; Johns, Paul; Brown, Brendan; Wang, Guo Ping; Hartland, Gregory

    2017-10-05

    Transient absorption microscopy (TAM) measurements have been used to study the optical properties of surface plasmon polariton (SPP) modes in gold nanoplates on a glass substrate. For thin gold nanoplates, the TAM images show an oscillation in the signal across the plate due to interference between the "bound" and "leaky" SPP modes. The wavelength of the interference pattern is given by λ = 2π/Δk, where Δk is the difference between the wavevectors for the bound and leaky modes and is sensitive to the dielectric constant of the material above the gold nanoplate. Back focal plane imaging was also used to measure the wavevector of the leaky mode, which, in combination with the Δk information from the TAM images, enabled the bound mode wavevector to be determined. These experiments represent the first far-field optical measurement of the wavevector for the bound mode in metal nanostructures.

  10. Gold surface with gold nitride-a surface enhanced Raman scattering active substrate

    NASA Astrophysics Data System (ADS)

    Brieva, A. C.; Alves, L.; Krishnamurthy, S.; Šiller, L.

    2009-03-01

    The nitration of gold surfaces is a nonpolluting method, which can lead to large scale production of substrates with remarkable properties and applications. We present a topographical study of the nanoscale structure of the gold nitride surfaces produced by radio frequency (rf) nitrogen plasma etching of thin gold films. Atomic force microscopy images taken after rf etching reveal the striking appearance of the cluster assembly with large clusters surrounded by small clusters (7.9±1.4 and 2.3±0.9 nm, respectively) appearing to exhibit an attractive interaction. We discuss the possible mechanism for this attraction based on a colloid model by Messina et al. [Phys. Rev. Lett. 85, 872 (2000)]. This surface exhibits a notable surface enhanced Raman scattering effect demonstrated with L-alanine and rhodamine-6G. The significance of this work is that we found that this SERS active gold nitride surface can be prepared in just one step: by nitrogen plasma etching a thin gold film. Until now most SERS active gold cluster covered surfaces have been prepared in several steps very often requiring complex lithography.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  12. 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.

  13. Gold Nanostructures for Surface-Enhanced Raman Spectroscopy, Prepared by Electrodeposition in Porous Silicon.

    PubMed

    Fukami, Kazuhiro; Chourou, Mohamed L; Miyagawa, Ryohei; Muñoz Noval, Álvaro; Sakka, Tetsuo; Manso-Silván, Miguel; Martín-Palma, Raúl J; Ogata, Yukio H

    2011-04-14

    Electrodeposition of gold into porous silicon was investigated. In the present study, porous silicon with ~100 nm in pore diameter, so-called medium-sized pores, was used as template electrode for gold electrodeposition. The growth behavior of gold deposits was studied by scanning electron microscope observation of the gold deposited porous silicon. Gold nanorod arrays with different rod lengths were prepared, and their surface-enhanced Raman scattering properties were investigated. We found that the absorption peak due to the surface plasmon resonance can be tuned by changing the length of the nanorods. The optimum length of the gold nanorods was ~600 nm for surface-enhanced Raman spectroscopy using a He-Ne laser. The reason why the optimum length of the gold nanorods was 600 nm was discussed by considering the relationship between the absorption peak of surface plasmon resonance and the wavelength of the incident laser for Raman scattering.

  14. Superlubricity of graphene nanoribbons on gold surfaces.

    PubMed

    Kawai, Shigeki; Benassi, Andrea; Gnecco, Enrico; Söde, Hajo; Pawlak, Rémy; Feng, Xinliang; Müllen, Klaus; Passerone, Daniele; Pignedoli, Carlo A; Ruffieux, Pascal; Fasel, Roman; Meyer, Ernst

    2016-02-26

    The state of vanishing friction known as superlubricity has important applications for energy saving and increasing the lifetime of devices. Superlubricity, as detected with atomic force microscopy, appears when sliding large graphite flakes or gold nanoclusters across surfaces, for example. However, the origin of the behavior is poorly understood because of the lack of a controllable nanocontact. We demonstrated the superlubricity of graphene nanoribbons when sliding on gold with a joint experimental and computational approach. The atomically well-defined contact allows us to trace the origin of superlubricity, unraveling the role played by ribbon size and elasticity, as well as by surface reconstruction. Our results pave the way to the scale-up of superlubricity and thus to the realization of frictionless coatings.

  15. Surface effects and gold-nanostructure surface coating of whispering-gallery microresonators

    NASA Astrophysics Data System (ADS)

    Ganta, Deepak

    Scope and method of study. The purpose of this study is to explore the surface effects of high-quality-factor optical microsphere resonators and thin-film-coated microresonators in various ambient gases. In this work, we present a systematic study of the assembly and characterization of gold nanostructures. We employ a wet-chemical synthesis method for growing gold nanorods and a directed electrochemical method for assembly of gold nanowires. The adhesion methods of gold nanostructures on high-quality-factor optical microsphere resonators are also investigated. Findings and conclusions. A novel method is employed for measuring thermal accommodation coefficients of various gases like nitrogen, helium and ambient air on several coated and uncoated surfaces of fused-silica microresonators, operating at room temperature. This method is further extended to measure the absorption coefficient of a surface film or water layer on a fused-silica microresonator, and provides a novel method to find the water layer desorption and adsorption rates on the surface of a microresonator in the presence of gases like ambient air and nitrogen. We have adapted methods for growing gold nanorods of different aspect ratios (AR), and developed a novel method of growing high-AR (20-400) gold nanowires from low-AR gold nanorods. Various methods were discovered to coat these gold nanostructures and carbon nanotubes on the fused-silica surface. The most successful method involves surface modification with MPMDMS (i.e., silanization) before coating with gold nanorods. These coating methods have made microresonators useful for plasmonic sensing applications.

  16. RAPID COMMUNICATION: Surface vertical deposition for gold nanoparticle film

    NASA Astrophysics Data System (ADS)

    Diao, J. J.; Qiu, F. S.; Chen, G. D.; Reeves, M. E.

    2003-02-01

    In this rapid communication, we present the surface vertical deposition (SVD) method to synthesize the gold nanoparticle films. Under conditions where the surface of the gold nanoparticle suspension descends slowly by evaporation, the gold nanoparticles in the solid-liquid-gas junction of the suspension aggregate together on the substrate by the force of solid and liquid interface. When the surface properties of the substrate and colloidal nanoparticle suspension define for the SVD, the density of gold nanoparticles in the thin film made by SVD only depends on the descending velocity of the suspension surface and on the concentration of the gold nanoparticle suspension.

  17. Unidirectional molecular motor on a gold surface

    NASA Astrophysics Data System (ADS)

    van Delden, Richard A.; Ter Wiel, Matthijs K. J.; Pollard, Michael M.; Vicario, Javier; Koumura, Nagatoshi; Feringa, Ben L.

    2005-10-01

    Molecules capable of mimicking the function of a wide range of mechanical devices have been fabricated, with motors that can induce mechanical movement attracting particular attention. Such molecular motors convert light or chemical energy into directional rotary or linear motion, and are usually prepared and operated in solution. But if they are to be used as nanomachines that can do useful work, it seems essential to construct systems that can function on a surface, like a recently reported linear artificial muscle. Surface-mounted rotors have been realized and limited directionality in their motion predicted. Here we demonstrate that a light-driven molecular motor capable of repetitive unidirectional rotation can be mounted on the surface of gold nanoparticles. The motor design uses a chiral helical alkene with an upper half that serves as a propeller and is connected through a carbon-carbon double bond (the rotation axis) to a lower half that serves as a stator. The stator carries two thiol-functionalized `legs', which then bind the entire motor molecule to a gold surface. NMR spectroscopy reveals that two photo-induced cis-trans isomerizations of the central double bond, each followed by a thermal helix inversion to prevent reverse rotation, induce a full and unidirectional 360° rotation of the propeller with respect to the surface-mounted lower half of the system.

  18. In vitro liberation of charged gold atoms: autometallographic tracing of gold ions released by macrophages grown on metallic gold surfaces.

    PubMed

    Larsen, Agnete; Stoltenberg, Meredin; Danscher, Gorm

    2007-07-01

    The present study demonstrates that cultured macrophages are able to liberate gold ions from metallic gold surfaces, a process suggested to be called "dissolucytosis", in a way analogous to the release taking place when metallic implants are placed in a body. Using the ultra-sensitive autometallographic (AMG) technique, we demonstrate that murine macrophages grown on a surface of metallic gold liberate gold ions. Ultra-structural AMG reveals that the gold ions are located in an ultra-thin membrane-like structure, "the dissolution membrane", intervened between the macrophages and the metal surface. The presence of AMG silver enhanced gold nanoparticles in the dissolution membrane proves that the release of charged gold atoms takes place extracellularly. The dissolution membrane is most likely secreted and chemically controlled by the "dissolucytes", here macrophages, and the membrane is essential for the dissolution of metal implants and particles, which cannot be phagocytosed. Our findings support the notion that whenever a metallic gold surface is attacked by dissolucytes, gold ions are liberated and taken up by surrounding cells. As gold ions can suppress the inflammatory process, it is reasonable to expect that when dissolucytosis takes place in the living organism the liberated gold ions will cause local immunosuppression.

  19. 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.

  20. Surface chemistry driven actuation in nanoporous gold

    SciTech Connect

    Biener, J; Wittstock, A; Zepeda-Ruiz, L; Biener, M M; Zielasek, V; Kramer, D; Viswanath, R N; Weissmuller, J; Baumer, M; Hamza, A V

    2008-04-14

    Although actuation in biological systems is exclusively powered by chemical energy, this concept has not been realized in man-made actuator technologies, as these rely on generating heat or electricity first. Here, we demonstrate that surface-chemistry driven actuation can be realized in high surface area materials such as nanoporous gold. For example, we achieve reversible strain amplitudes in the order of a few tenths of a percent by alternating exposure of nanoporous Au to ozone and carbon monoxide. The effect can be explained by adsorbate-induced changes of the surface stress, and can be used to convert chemical energy directly into a mechanical response thus opening the door to surface-chemistry driven actuator and sensor technologies.

  1. 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.

  2. Temperature-dependent morphological evolution of clustered gold surface

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Govind

    2012-07-01

    The present pragmatic deals with the surface morphology and the temperature induced modifications of gold surface. The gold surface consists of three dimensional (3D) large nanoclusters and the shape of these nanoclusters was identified as cap like structure with approximately circular periphery. The effect of temperature on the gold surface has been characterized by Scanning Tunnelling Microscopy technique. Annealing the gold surface at 473 K induce inter-diffusion of the 3D-nanoclusters, while the formation of nanoscale step and terrace morphology near the cluster boundary has been detected at 573 K. This study also reveals that the clusters size and roughness of gold surface varies differently in different range of annealing temperature.

  3. 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.

  4. An electrochemical investigation of gold, tin and titanium compounds

    SciTech Connect

    Sawtelle, S.M.

    1992-01-01

    The determination of the electron transfer properties of gold, tin, and titanium compounds using electrochemical and spectroelectrochemical techniques is the focus of this dissertation. The investigations of the gold compounds include the determination of the properties of Au[PR[sub 3

  5. 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.

  6. Gold nanoparticles with patterned surface monolayers for nanomedicine: current perspectives.

    PubMed

    Pengo, Paolo; Şologan, Maria; Pasquato, Lucia; Guida, Filomena; Pacor, Sabrina; Tossi, Alessandro; Stellacci, Francesco; Marson, Domenico; Boccardo, Silvia; Pricl, Sabrina; Posocco, Paola

    2017-09-01

    Molecular self-assembly is a topic attracting intense scientific interest. Various strategies have been developed for construction of molecular aggregates with rationally designed properties, geometries, and dimensions that promise to provide solutions to both theoretical and practical problems in areas such as drug delivery, medical diagnostics, and biosensors, to name but a few. In this respect, gold nanoparticles covered with self-assembled monolayers presenting nanoscale surface patterns-typically patched, striped or Janus-like domains-represent an emerging field. These systems are particularly intriguing for use in bio-nanotechnology applications, as presence of such monolayers with three-dimensional (3D) morphology provides nanoparticles with surface-dependent properties that, in turn, affect their biological behavior. Comprehensive understanding of the physicochemical interactions occurring at the interface between these versatile nanomaterials and biological systems is therefore crucial to fully exploit their potential. This review aims to explore the current state of development of such patterned, self-assembled monolayer-protected gold nanoparticles, through step-by-step analysis of their conceptual design, synthetic procedures, predicted and determined surface characteristics, interactions with and performance in biological environments, and experimental and computational methods currently employed for their investigation.

  7. Conjugated Gold-Porphyrin Monolayers Assembled on Inorganic Surfaces.

    PubMed

    Gulino, Antonino; Contino, Annalinda; Giuseppe Maccarrone, Giuseppe Maccarrone; Fragalà, Maria Elena; Spitaleri, Luca

    2017-08-24

    Gold nanoparticles show important properties owing to their electronic structures. A limitation of some gold nanoparticles is that they either show surface plasmon or luminescence. In fact the increase in size of the gold nanoparticles and the appearing of the surface plasmon may result in the disappearance of luminescence. The aim of our study was the nanoscale assembly of Au nanoparticles on a monolayer of porphyrin molecules previously anchored to functionalized inorganic surfaces. This functional architecture not only exhibits a strong surface plasmon due to the gold nanoparticles but also a strong luminescence signal from porphyrin molecules. Finally we observed a long range order in the Au nanoparticles conjugated to the porphyrin monolayer. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    NASA Astrophysics Data System (ADS)

    Johnson, Grant; Priest, Thomas; Laskin, Julia

    2012-02-01

    Monodisperse gold clusters have been prepared on surfaces in different charge states through soft landing of mass-selected ions. Gold clusters were synthesized in methanol solution by reduction of a gold precursor with a weak reducing agent in the presence of a diphosphine capping ligand. Electrospray ionization was used to introduce the clusters into the gas-phase and mass-selection was employed to isolate a single ionic cluster species which was delivered to surfaces at well controlled kinetic energies. Using in-situ time of flight secondary ion mass spectrometry (SIMS) it is demonstrated that the cluster retains its 3+ charge state when soft landed onto the surface of a fluorinated self assembled monolayer on gold. In contrast, when deposited onto carboxylic acid terminated and conventional alkyl thiol surfaces on gold the clusters exhibit larger relative abundances of the 2+ and 1+ charge states, respectively. The kinetics of charge reduction on the surface have been investigated using in-situ Fourier Transform Ion Cyclotron Resonance SIMS. It is shown that an extremely slow interfacial charge reduction occurs on the fluorinated monolayer surface while an almost instantaneous neutralization takes place on the surface of the alkyl thiol monolayer. Our results demonstrate that the size and charge state of small gold clusters on surfaces, both of which exert a dramatic influence on their chemical and physical properties, may be tuned through soft landing of mass-selected ions onto selected substrates.

  9. Use of cellulose derivatives on gold surfaces for reduced nonspecific adsorption of immunoglobulin G.

    PubMed

    Volden, Sondre; Zhu, Kaizheng; Nyström, Bo; Glomm, Wilhelm R

    2009-09-01

    This study addresses the design of protein-repellent gold surfaces using hydroxyethyl- and ethyl(hydroxyethyl) cellulose (HEC and EHEC) and hydrophobically modified analogues of these polymers (HM-HEC and HM-EHEC). Adsorption behavior of the protein immunoglobulin G (IgG) onto pure gold and gold surfaces coated with cellulose polymers was investigated and described by quartz crystal microbalance with dissipation monitoring (QCM-D), atomic force microscopy (AFM) and contact angle measurements (CAM). Surfaces coated with the hydrophobically modified cellulose derivatives were found to significantly outperform a reference poly(ethylene glycol) (PEG) coating, which in turn prevented 90% of non-specific protein adsorption as compared to adsorption onto pure gold. HEC and EHEC prevented around 30% and 60% of the IgG adsorption observed on pure gold, while HM-HEC and HM-EHEC were both found to completely hinder biofouling when deposited on the gold substrates. Adsorption behavior of IgG has been discussed in terms of polymer surface coverage and roughness of the applied surfaces, together with hydrophobic interactions between protein and gold, and also polymer-protein interactions.

  10. Ballbot-type motion of N-heterocyclic carbenes on gold surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Gaoqiang; Rühling, Andreas; Amirjalayer, Saeed; Knor, Marek; Ernst, Johannes Bruno; Richter, Christian; Gao, Hong-Jun; Timmer, Alexander; Gao, Hong-Ying; Doltsinis, Nikos L.; Glorius, Frank; Fuchs, Harald

    2017-02-01

    Recently, N-heterocyclic carbenes (NHCs) were introduced as alternative anchors for surface modifications and so offered many attractive features, which might render them superior to thiol-based systems. However, little effort has been made to investigate the self-organization process of NHCs on surfaces, an important aspect for the formation of self-assembled monolayers (SAMs), which requires molecular mobility. Based on investigations with scanning tunnelling microscopy and first-principles calculations, we provide an understanding of the microscopic mechanism behind the high mobility observed for NHCs. These NHCs extract a gold atom from the surface, which leads to the formation of an NHC-gold adatom complex that displays a high surface mobility by a ballbot-type motion. Together with their high desorption barrier this enables the formation of ordered and strongly bound SAMs. In addition, this mechanism allows a complementary surface-assisted synthesis of dimeric and hitherto unknown trimeric NHC gold complexes on the surface.

  11. Hot electron dynamics and impurity scattering on gold nanoshell surfaces

    NASA Astrophysics Data System (ADS)

    Wolfgang, John Adam

    2000-10-01

    Recent ultrafast pump-probe experiments studying the relaxation rate of an optically excited hot electron distribution on Au/Au2S gold nanoshells indicate that this relaxation rate can be modified by the chemical environment surrounding the shell. This work will begin a theoretical investigation of the effect of chemical adsorbates---solvents and impurities---upon nanoshell hot electron dynamics. The effects of water, polyvinyl alcohol (PVA), sulfur, p-aminobenzoic acid, p-mercaptobenzoic acid and propylamine adsorbates are examined for their electronic interaction with a noble metal surface. p-Aminobenzoic acid is found to have a very large dipole moment when adsorbed to the metal surface, in contrast to p-mercaptobenzoic acid, propylamine and water. This correlates well to the experimentally observed results where nanoshells dispersed in an aqueous soulution with p-aminobenzoic acid display a faster relaxation rate compared to nanoshells dispersed in a pure water, aqueous propylamine or aqueous p-mercaptobenzoic acid environments. This thesis will also introduce a non-equilibrium Green's function approach, based on the formalism developed by Baym and Kadanoff, to model the dynamics of a hot electron distribution. The model will be discussed in terms of a simple potential scattering mechanism, which may in later work be expanded to include more complex electron-electron and electron-phonon interactions. Lastly acoustic oscillation modes are calculated for solid gold spheres and gold-silicon nanoshells. These modes describe an effect of electron-phonon coupling between the hot electron distribution and the nanoshell lattice, whereby the electronic energy is converted into mechanical energy.

  12. 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.

  13. Surface interactions between gold nanoparticles and biochar

    USDA-ARS?s Scientific Manuscript database

    Engineered nanomaterials are directly applied to agricultural soils as a part of pesticide/fertilize formulations and sludge/manure amendments. Yet, no prior reports are available on the extent and reversibility of gold nanoparticles (nAu) retention by soil components including charcoal black carbo...

  14. Undulatory delamination of thin polymer films on gold surfaces.

    PubMed

    Chah, Soonwoo; Noolandi, Jaan; Zare, Richard N

    2005-10-20

    Using two-dimensional surface plasmon resonance measurements, we have observed the formation of traveling waves in the delamination of thin films of polydimethylsilane (PDMS) exposed to methanol. Films were spin-coated on a gold surface and the methanol was added to the top surface. The stress-induced instability caused by the swelling of the PDMS thin film when its edge is pinned to the gold surface leads to wrinkle formation and propagation at the interface. The periodic pattern is thought to be the result of an Asaro-Tiller-Grinfeld (ATG) instability.

  15. Formation of Gold Microparticles by Ablation with Surface Plasmons

    PubMed Central

    Garner, Quincy; Molian, Pal

    2013-01-01

    The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an array of 200 nm diameter holes with a periodicity of 400 nm was prepared and placed on a silicon substrate. The mask was composed of 60 µm thick porous alumina membrane sputter-coated with 100 nm thin gold film. A Nd:YAG laser with 1064 nm wavelength and 230 µs pulse width (free-running mode) was then passed through the mask at an energy fluence of 0.35 J/cm2. The extraordinary transmission of laser light through alumina/gold micro-hole optical antenna created both extended and localized surface plasmons that caused the gold film at the bottom of the mask to fragment into microparticles and deposit on the silicon substrate that is in direct contact with the mask. The surface plasmon method is simpler, quicker, more energy efficient, and environmentally safer than existing physical and chemical methods, as well as being contamination-free, and can be extended to all types of materials that will in turn allow for new possibilities in the formation of structured surfaces. PMID:28348354

  16. 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.

  17. 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.

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

    SciTech Connect

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

    2016-09-07

    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.

  19. 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.

  20. 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.

  1. Enhanced optical second harmonic generation in hybrid polymer nanoassemblies based on coupled surface plasmon resonance of a gold nanoparticle array

    NASA Astrophysics Data System (ADS)

    Ishifuji, Miki; Mitsuishi, Masaya; Miyashita, Tokuji

    2006-07-01

    Effective utilization of coupled surface plasmon resonance from gold nanoparticles was demonstrated experimentally for optoelectronic applications based on second-order nonlinear optics. Hybrid polymer nanoassemblies were constructed by manipulating gold nanoparticle arrays with nonlinear optical active polymer nanosheets to investigate the second harmonic generation. The gold nanoparticle arrays were assembled on heterodeposited polymer nanosheets. The second harmonic light intensity was enhanced by a factor of 8. The observed enhancement was attributed to coupling of surface plasmons between two adjacent gold nanoparticles, thereby enhancing the surface electromagnetic field around the nanoparticles at the fundamental light wavelength (1064nm).

  2. Triply surface-plasmon resonant four-wave mixing imaging of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Masia, Francesco; Langbein, Wolfgang; Watson, Peter; Borri, Paola

    2011-03-01

    We have developed a novel multiphoton microscopy technique not relying on (and hence not limited by) fluorescence emission, which exploits the third-order nonlinearity called four-wave mixing of gold nanoparticles in resonance with their surface Plasmon. The coherent, transient and resonant nature of this signal allows its detection free from backgrounds that limit other contrast methods for gold nanoparticles. We show detection of single 10nm gold nanoparticles with low excitation intensities, corresponding to negligible average thermal heating. Owing to the the third-order nonlinearity we measure a transversal and axial resolution of 140nm and 470nm respectively, better than the one-photon diffraction limit. We also show high-contrast imaging of gold-labels down to 5nm size in Golgi structures of HepG2 cells at useful imaging speeds (10 kHz pixel rate). Thermal dissociation of gold nanoparticles from their bonding sites when varying the excitation intensity is also investigated.

  3. Mercury adsorption to gold nanoparticle and thin film surfaces

    NASA Astrophysics Data System (ADS)

    Morris, Todd Ashley

    Mercury adsorption to gold nanoparticle and thin film surfaces was monitored by spectroscopic techniques. Adsorption of elemental mercury to colloidal gold nanoparticles causes a color change from wine-red to orange that was quantified by UV-Vis absorption spectroscopy. The wavelength of the surface plasmon mode of 5, 12, and 31 nm gold particles blue-shifts 17, 14, and 7.5 nm, respectively, after a saturation exposure of mercury vapor. Colorimetric detection of inorganic mercury was demonstrated by employing 2.5 nm gold nanoparticles. The addition of low microgram quantities of Hg 2+ to these nanoparticles induces a color change from yellow to peach or blue. It is postulated that Hg2+ is reduced to elemental mercury by SCN- before and/or during adsorption to the nanoparticle surface. It has been demonstrated that surface plasmon resonance spectroscopy (SPRS) is sensitive to mercury adsorption to gold and silver surfaces. By monitoring the maximum change in reflectivity as a function of amount of mercury adsorbed to the surface, 50 nm Ag films were shown to be 2--3 times more sensitive than 50 nm Au films and bimetallic 15 nm Au/35 nm Ag films. In addition, a surface coverage of ˜40 ng Hg/cm2 on the gold surface results in a 0.03° decrease in the SPR angle of minimum reflectivity. SPRS was employed to follow Hg exposure to self-assembled monolayers (SAMs) on Au. The data indicate that the hydrophilic or hydrophobic character of the SAM has a significant effect on the efficiency of Hg penetration. Water adsorbed to carboxylic acid end group of the hydrophilic SAMs is believed to slow the penetration of Hg compared to methyl terminated SAMs. Finally, two protocols were followed to remove mercury from gold films: immersion in concentrated nitric acid and thermal annealing up to 200°C. The latter protocol is preferred because it removes all of the adsorbed mercury from the gold surface and does not affect the morphology of the gold surface.

  4. 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})

  5. Island-like Nanoporous Gold: Smaller Island Generates Stronger Surface-Enhanced Raman Scattering.

    PubMed

    Huang, Jinglin; He, Zhibing; He, Xiaoshan; Liu, Yansong; Wang, Tao; Chen, Guo; Tang, Cuilan; Jia, Ru; Liu, Lei; Zhang, Ling; Wang, Jian; Ai, Xing; Sun, Shubing; Xu, Xiaoliang; Du, Kai

    2017-08-30

    The surface-enhanced Raman scattering properties of nanoporous gold prepared by the dealloying technique have been investigated for many years.The relatively low enhancement factor and the poor uniformity of existing conventional or advanced nanoporous gold structures are still the main factors that limit their wide application as Raman enhancement substrates. Here, we report island-like nanoporous gold (INPG) fabricated by simply controlling the composition of the dealloying precursor.This nanostructure can generate ∼10 times higher enhancement factor (above 10(7)) with ∼4 times lower gold consumption than conventional nanoporous gold. The dimensions of the gold islands can be controlled by the composition of the precursor. The enhancement factor can therefore be controlled by the gold island dimensions, which suggests an effective approach to fabricate better Raman enhancement substrates. Furthermore, INPG exhibits excellent Raman enhancement uniformity and reproducibility with the relative standard deviations of only 2.5% and 6.5%, which originate from the extremely homogeneous structure of INPG at both the microscale and macroscale. The excellent surface-enhanced Raman scattering properties make INPG a potential surface-enhanced Raman scattering substrate.

  6. STM observation of thia[1 1]heterohelicene on gold( 1 1 1 ) and gold(1 1 0) surface

    NASA Astrophysics Data System (ADS)

    Taniguchi, Masahiro; Nakagawa, Hiroko; Yamagishi, Akihiko; Yamada, Kohichi

    2002-06-01

    Monolayers of helically shaped aromatic compound, hexathia[1 1]heterohelicene ([1 1]TH), which consists of five benzene rings and six thiophene rings were prepared on gold(1 1 1) and gold(1 1 0) surface under UHV condition. LEED and STM were used for the structural study focused on the molecular chirality. [1 1]TH monolayer on gold(1 1 1) substrate showed the same structure as on (1 1 1) analogue of polycrystalline surface. [1 1]TH evaporated on gold(1 1 0) showed loosely packed molecular chains. The results were compared with the results on gold polycrystalline surface and the bulk structural analysis.

  7. Growth of pentacene on clean and modified gold surfaces

    SciTech Connect

    Kaefer, Daniel; Ruppel, Lars; Witte, Gregor

    2007-02-15

    The growth and evolution of pentacene films on gold substrates have been studied. By combining complementary techniques including scanning tunneling microscopy, atomic force microscopy, scanning electron microscopy, near-edge x-ray-absorption fine structure, and x-ray diffraction, the molecular orientation, crystalline structure, and morphology of the organic films were characterized as a function of film thickness and growth parameters (temperature and rate) for different gold substrates ranging from Au(111) single crystals to polycrystalline gold. Moreover, the influence of precoating the various gold substrates with self-assembled monolayers (SAM's) of organothiols with different chemical terminations has been studied. On bare gold the growth of pentacene films is characterized by a pronounced dewetting while the molecular orientation within the resulting crystalline three-dimensional islands depends distinctly on the roughness and cleanliness of the substrate surface. After completion of the first wetting layer where molecules adopt a planar orientation parallel to the surface the molecules continue to grow in a tilted fashion: on Au(111) the long molecular axis is oriented parallel to the surface while on polycrystalline gold it is upstanding oriented and thus parallels the crystalline orientation of pentacene films grown on SiO{sub 2}. On SAM pretreated gold substrates the formation of a wetting layer is effectively suppressed and pentacene grows in a quasi-layer-by-layer fashion with an upstanding orientation leading to rather smooth films. The latter growth mode is observed independently of the chemical termination of the SAM's and the roughness of the gold substrate. Possible reasons for the different growth mechanism as well as consequences for the assignment of spectroscopic data of thin pentacene film are discussed.

  8. Synthesis and tuning of gold nanorods with surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Shajari, Daryush; Bahari, Ali; Gill, Pooria; Mohseni, Mojtaba

    2017-02-01

    Gold nanostructures in general and gold nanorods in particular due to their plasmon resonance has been employed for many applications, such as biosensors. For the biosensors uses, gold nanorods remain popular and reproducibility of them is the most important and critical. In the present work we used six different CTAB (Hexadecyltrimethylammonium bromide) products and one BDAC (Benzyldimethylhexadecylammonium chloride) with varying silver nitrate concentration in the seed-mediated growth of gold nanostructures. We synthesized gold nanorods with varying aspect ratio up to 5.5 with a longitudinal surface plasmon resonance peak from 670 to 950 nm. We obtained excellent rod-shape gold nanostructures witch were reliable and reproducible with our method based on common seed-mediated growth. The synthesized nanostructures were characterized by UV-visible spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Here, we report our method in more detail as a user-friendly guide for the production of gold nanorods and tuning of their aspect ratios.

  9. Directional surface enhanced Raman scattering on gold nano-gratings

    NASA Astrophysics Data System (ADS)

    Gillibert, Raymond; Sarkar, Mitradeep; Bryche, Jean-François; Yasukuni, Ryohei; Moreau, Julien; Besbes, Mondher; Barbillon, Grégory; Bartenlian, Bernard; Canva, Michael; Lamy de la Chapelle, Marc

    2016-03-01

    Directional plasmon excitation and surface enhanced Raman scattering (SERS) emission were demonstrated for 1D and 2D gold nanostructure arrays deposited on a flat gold layer. The extinction spectrum of both arrays exhibits intense resonance bands that are redshifted when the incident angle is increased. Systematic extinction analysis of different grating periods revealed that this band can be assigned to a propagated surface plasmon of the flat gold surface that fulfills the Bragg condition of the arrays (Bragg mode). Directional SERS measurements demonstrated that the SERS intensity can be improved by one order of magnitude when the Bragg mode positions are matched with either the excitation or the Raman wavelengths. Hybridized numerical calculations with the finite element method and Fourier modal method also proved the presence of the Bragg mode plasmon and illustrated that the enhanced electric field of the Bragg mode is particularly localized on the nanostructures regardless of their size.

  10. Optical fiber surface plasmon resonance sensor with surface modified gold nanorods for biochemical detection

    NASA Astrophysics Data System (ADS)

    Li, Lixia; Liang, Yuzhang; Xie, Lingxiao; Lu, Mengdi; Peng, Wei

    2014-11-01

    A novel gold nanorods (GNRs) modified optical fiber localized surface plasmon resonance (LSPR) sensor for biochemical detection is demonstrated. The gold nanorods (GNRs) assembled film as the sensing layer was built on the polyelectrolyte (PE) multilayer modified sidewall of an unclad optical fiber. Poly (allylamine hydrochloride) (PAH)/poly (sodium 4-styrenesulfonate) (PSS) films were formed through layer-by-layer (LbL) assembly. The influence of the thickness of polyelectrolyte films was investigated. Simultaneously, the feasibility of the proposed film coupled nanorods optical fiber LSPR sensor in monitoring a series of concentration sucrose solutions with different refractive index is examined. Results suggest that the compact sensor can perform qualitative and quantitative detection in real-time biomolecular sensing.

  11. Analysis of gold(I/III)-complexes by HPLC-ICP-MS demonstrates gold(III) stability in surface waters.

    PubMed

    Ta, Christine; Reith, Frank; Brugger, Joël; Pring, Allan; Lenehan, Claire E

    2014-05-20

    Understanding the form in which gold is transported in surface- and groundwaters underpins our understanding of gold dispersion and (bio)geochemical cycling. Yet, to date, there are no direct techniques capable of identifying the oxidation state and complexation of gold in natural waters. We present a reversed phase ion-pairing HPLC-ICP-MS method for the separation and determination of aqueous gold(III)-chloro-hydroxyl, gold(III)-bromo-hydroxyl, gold(I)-thiosulfate, and gold(I)-cyanide complexes. Detection limits for the gold species range from 0.05 to 0.30 μg L(-1). The [Au(CN)2](-) gold cyanide complex was detected in five of six waters from tailings and adjacent monitoring bores of working gold mines. Contrary to thermodynamic predictions, evidence was obtained for the existence of Au(III)-complexes in circumneutral, hypersaline waters of a natural lake overlying a gold deposit in Western Australia. This first direct evidence for the existence and stability of Au(III)-complexes in natural surface waters suggests that Au(III)-complexes may be important for the transport and biogeochemical cycling of gold in surface environments. Overall, these results show that near-μg L(-1) enrichments of Au in environmental waters result from metastable ligands (e.g., CN(-)) as well as kinetically controlled redox processes leading to the stability of highly soluble Au(III)-complexes.

  12. Selective electrochemical gold deposition onto p-Si (1 0 0) surfaces

    NASA Astrophysics Data System (ADS)

    Santinacci, L.; Djenizian, T.; Schwaller, P.; Suter, T.; Etcheberry, A.; Schmuki, P.

    2008-09-01

    In this paper, we report selective electrochemical gold deposition onto p-type Si (1 0 0) into nanoscratches produced through a thin oxide layer using an atomic force microscope. A detailed description of the substrate engraving process is presented. The influence of the main scratching parameters such as the normal applied force, the number of scans and the scanning velocity are investigated as well as the mechanical properties of the substrate. Gold deposition is carried out in a KAu(CN)2 + KCN solution by applying cathodic voltages for various durations. The gold deposition process is investigated by cyclic voltammetry. Reactivity enhancement at the scratched locations was studied by comparing the electrochemical behaviour of intact and engraved surfaces using a micro-electrochemical setup. Selective electrochemical gold deposition is achieved: metallic patterns with a sub-500 nm lateral resolution are obtained demonstrating, therefore, the bearing potential of this patterning technique.

  13. Surface characterization of immunosensor conjugated with gold nanoparticles based on cyclic voltammetry and X-ray photoelectron spectroscopy.

    PubMed

    Lai, Lee-Jene; Yang, Yaw-Wen; Lin, Yao-Kwang; Huang, Li-Ling; Hsieh, Yi-Heui

    2009-02-01

    This investigation describes the surface characterization of rabbit immunoglobulin G (IgG) conjugated with gold nanoparticles. Goat anti-rabbit immunoglobulin G tagged with 5nm gold nanoparticles was applied to detect the IgG. Then, the autocatalyzed deposition of Au(3+) onto the surface of anti-IgGAu increased the surface area per gold nanoparticle. The immobilization chemistries and the atomic concentrations of Au(4f), P(2p), S(2p), C(1s), N(1s) and O(1s) of the resulting antibody-modified Au electrodes were determined by X-ray photoelectron spectroscopy (XPS). The sulfur that is involved in the cysteamine binding and the enlargement of the gold nanoparticles are identified using cyclic voltammetry. The results reveal that the surface area per gold particle, following the autocatalyzed deposition Au(3+) on the surface of anti-IgGAu, was approximately seven times higher than that before deposition.

  14. 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.

  15. Dependence of the signal amplification potential of colloidal gold nanoparticles on resonance wavelength in surface plasmon resonance-based detection

    PubMed Central

    Fu, Elain; Ramsey, Stephen A.; Yager, Paul

    2008-01-01

    We demonstrate the resonance wavelength-dependent signal of colloidal gold nanoparticles adsorbed to a planar gold surface in surface plasmon resonance (SPR)-based detection. Experimental measurements of the SPR signal as a function of particle surface coverage are presented for three different resonance wavelengths. The SPR signal due to the colloidal gold nanoparticles varies across the resonance wavelengths of 650 nm, 770 nm, and 920 nm. The experimental SPR curves show good agreement with the results of a Lorentz absorbance model at the lower particle surface coverages investigated. The results demonstrate an almost 2-fold signal difference for a subset of the experimental conditions explored. PMID:17765071

  16. Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment.

    PubMed

    Novotná, Zdeňka; Rimpelová, Silvie; Juřík, Petr; Veselý, Martin; Kolská, Zdeňka; Hubáček, Tomáš; Borovec, Jakub; Švorčík, Václav

    2017-12-01

    Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

  17. Tuning Surface Chemistry of Polyetheretherketone by Gold Coating and Plasma Treatment

    NASA Astrophysics Data System (ADS)

    Novotná, Zdeňka; Rimpelová, Silvie; Juřík, Petr; Veselý, Martin; Kolská, Zdeňka; Hubáček, Tomáš; Borovec, Jakub; Švorčík, Václav

    2017-06-01

    Polyetheretherketone (PEEK) has good chemical and biomechanical properties that are excellent for biomedical applications. However, PEEK exhibits hydrophobic and other surface characteristics which cause limited cell adhesion. We have investigated the potential of Ar plasma treatment for the formation of a nanostructured PEEK surface in order to enhance cell adhesion. The specific aim of this study was to reveal the effect of the interface of plasma-treated and gold-coated PEEK matrices on adhesion and spreading of mouse embryonic fibroblasts. The surface characteristics (polarity, surface chemistry, and structure) before and after treatment were evaluated by various experimental techniques (gravimetry, goniometry, X-ray photoelectron spectroscopy (XPS), and electrokinetic analysis). Further, atomic force microscopy (AFM) was employed to examine PEEK surface morphology and roughness. The biological response of cells towards nanostructured PEEK was evaluated in terms of cell adhesion, spreading, and proliferation. Detailed cell morphology was evaluated by scanning electron microscopy (SEM). Compared to plasma treatment, gold coating improved PEEK wettability. The XPS method showed a decrease in the carbon concentration with increasing time of plasma treatment. Cell adhesion determined on the interface between plasma-treated and gold-coated PEEK matrices was directly proportional to the thickness of a gold layer on a sample. Our results suggest that plasma treatment in a combination with gold coating could be used in biomedical applications requiring enhanced cell adhesion.

  18. Surface Nucleation in the Freezing of Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Mendez-Villuendas, Eduardo; Bowles, Richard K.

    2007-05-01

    We use molecular simulation to calculate the nucleation free energy barrier for the freezing of a 456 atom gold cluster over a range of temperatures. The results show that the embryo of the solid cluster grows at the vapor-surface interface for all temperatures studied and that the usual classical nucleation model, with the embryo growing in the core of the cluster, is unable to predict the shape of the free energy barrier. We use a simple partial wetting model that treats the crystal as a lens-shaped nucleus at the liquid-vapor interface and find that the line tension plays an important role in the freezing of gold nanoparticles.

  19. 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.

  20. 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

  1. Microscale Heat Transfer Transduced by Surface Plasmon Resonant Gold Nanoparticles

    PubMed Central

    Roper, D. Keith; Ahn, W.; Hoepfner, M.

    2008-01-01

    Visible radiation at resonant frequencies is transduced to thermal energy by surface plasmons on gold nanoparticles. Temperature in ≤10-microliter aqueous suspensions of 20-nanometer gold particles irradiated by a continuous wave Ar+ ion laser at 514 nm increased to a maximum equilibrium value. This value increased in proportion to incident laser power and in proportion to nanoparticle content at low concentration. Heat input to the system by nanoparticle transduction of resonant irradiation equaled heat flux outward by conduction and radiation at thermal equilibrium. The efficiency of transducing incident resonant light to heat by microvolume suspensions of gold nanoparticles was determined by applying an energy balance to obtain a microscale heat-transfer time constant from the transient temperature profile. Measured values of transduction efficiency were increased from 3.4% to 9.9% by modulating the incident continuous wave irradiation. PMID:19011696

  2. 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

  3. Adsorption of cellulose derivatives on flat gold surfaces and on spherical gold particles.

    PubMed

    Amirkhani, Masoud; Volden, Sondre; Zhu, Kaizheng; Glomm, Wilhelm R; Nyström, Bo

    2008-12-01

    The adsorption of hydroxyethylcellulose (HEC), ethyl(hydroxyethyl)cellulose (EHEC), and their hydrophobically modified counterparts HM-HEC and HM-EHEC has been studied on planar gold and citrate-covered gold surfaces by means of quartz crystal microbalance with dissipation monitoring (QCM-D), and on citrate-covered gold particles with the aid of dynamic light scattering (DLS). The QCM-D results indicate that larger amounts of polymer are adsorbed from aqueous solutions of HM-HEC and HM-EHEC on both substrates than from solutions of their unmodified analogues. The adsorption affinity for all the polymers, except EHEC, is higher on the citrate-covered surfaces than on the bare gold substrate. This indicates that more adsorption sites are activated in the presence of the citrate layer. The experimental adsorption data for all the polymers can be described fairly well by the Langmuir adsorption isotherm. However, at very low polymer concentrations significant deviations from the model are observed. The value of the hydrodynamic thickness of the adsorbed polymer layer (delta h), determined from DLS, rises with increasing polymer concentration for all the cellulose derivatives; a Langmuir type of isotherm can be used to roughly describe the adsorption behavior. Because of good solvent conditions for HEC the chains extend far out in the bulk at higher concentrations and the value of delta h is much higher than that of HM-HEC. The adsorption of EHEC and HM-EHEC onto gold particles discloses that the values of delta h are considerably higher for the hydrophobically modified cellulose derivative, and this finding is compatible with the trend in layer thickness estimated from the QCM-D measurements.

  4. Photophysical aspects of molecular probes near nanostructured gold surfaces.

    PubMed

    Ghosh, Sujit Kumar; Pal, Tarasankar

    2009-05-28

    Highly ordered, self-organized assemblies of organic molecules at surfaces of metal particles with sizes in the nanometer regime have been a subject of immense interest in recent years. Amongst the metal nanoparticles, considering the nobility of gold, organic fluoroprobes have often been attached to the surfaces of gold nanoparticles to form an extended network for potential technological applications. These organic-inorganic hybrid nanoassemblies offer an efficient route for the patterning of surfaces with functional nanometer-scale architectures utilizing several non-covalent intermolecular bonding interactions, e.g., hydrogen bonding, coordination bonding, etc. There is a growing recognition of fluorescence spectroscopy to achieve a molecular level understanding of the physical and chemical aspects of the molecule-surface interactions. The fluorophore-bound gold nanoparticles provide a convenient way to examine the mechanistic details of various deactivation pathways of the photoexcited fluoroprobes, such as energy and electron transfer to the particles as well as different types of intermolecular interactions involved in producing the bottom-up assembly of tailored nanostructures with a wide variety of structures and properties. The understanding of electronic absorption and dynamics in nanoparticulate systems is essential before assembling them into devices, which is essentially the future goal of the use of nanostructured systems. It is, therefore, important to elucidate the particle size and distance dependence on the interaction between excited molecular probes and the gold nanoparticles. The potential impact of the derived nanopatterned surfaces ranges from applications in molecular electronics to selective sensors to diagnostic devices. The greatest promise of these systems lies in the potential to tune functional aspects of the supramolecular assemblies at surfaces by manipulation of the interactions governing the derivation of supramolecular function

  5. Surface diffusion of gold on quasihexagonal-reconstructed Au(100)

    NASA Astrophysics Data System (ADS)

    Trembulowicz, Artur; Ehrlich, Gert; Antczak, Grazyna

    2011-12-01

    The scanning tunneling microscope has been used to measure the saturation island density Nx of gold on the hex-reconstructed Au(100) surface over a range of temperatures starting at 76 K. Assuming that the critical island size equals one, ∂lnNx/∂(1/T) = χEd/k, where χ is the scaling exponent, Ed gives the activation energy for surface diffusion, and k is the Boltzmann constant. The scaling exponent χ has been obtained as 0.26 ± 0.03 from measurements of the island density as a function of the deposition rate, indicating that diffusion is indeed one-dimensional (anisotropic) and the critical island size is unity. We therefore derive an activation energy of 0.32 ± 0.02eV and a frequency prefactor of 2(×4±1) × 1013 s-1 for diffusion of gold on hex-reconstructed Au(100).

  6. 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.

  7. 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

  8. Optical and electrochemical properties of ordered macroporous gold array on the ITO surface

    NASA Astrophysics Data System (ADS)

    Lu, Huidan; Liu, Yongping; Han, Guo-Cheng

    2011-06-01

    The electrochemical and optical properties of transparent, two-dimensional macroporous gold film were investigated. Colloidal crystal templates were assembled onto indium-doped tin oxide (ITO) glass surface through vertical depositing method. Following gold electrodeposition, they were removed by dissolution with tetrahydrofuran (THF). The highly ordered macroporous gold array was achieved. It was characterized by scanning electron microscope (SEM) and ultraviolet visible (UV-vis) spectrophotometry. The optical transparency of the gold film was near 25% and fairly constant between 300 and 900 nm. The macroporous gold film electrode was mounted into a thin-layer transmission cell. The electrochemical response was evaluated by thin-layer cyclic voltammograms (CV) of the Fe (CN) 63-/Fe (CN) 64- couple. Thin-layer cell exhibits good shape of waves and nearly symmetric cathodic and anodic waves. E0' value and n of TMPD + rad /TMPD (TMPD is acronyms for N,N,N',N'-tetramethyl-p-phenylenediamine, and TMPD + rad is its mono-cation radical) couple were determined. Furthermore, results demonstrated electrolytic equilibrium was faster reached in macroporous gold film than ITO electrode.

  9. Tuning the surface enhanced Raman scattering activity of gold nanocubes by silver coating

    NASA Astrophysics Data System (ADS)

    Ding, Shu-Jun; Zhu, Jian

    2015-12-01

    Colloidal gold nanocubes coated with a silver nanoshell have been synthesized via the seed mediated growth method. By changing the volume of gold seed and silver nitrate, both the edge length of gold nanocube and the thickness of silver shell could be fine-tuned. The surface-enhanced Raman scattering (SERS) activity of these core-shell structural Au-Ag bimetallic nanocubes has also been investigated by using the rhodamine 6G (R6G) as Raman active probe. It has been found the SERS activity of the silver-coated gold nanocubes greatly depends on their geometry factors. By decreasing the edge length of gold nanocubes or increasing the silver coating thickness, the SERS activity has been greatly enhanced. By comparing with other Raman bands of R6G, the enhancement of the Raman peak corresponding to the Csbnd Csbnd C ring in-plane vibration mode is more sensitive to the geometries of the nanostructure. These improved SERS properties of silver-coated gold nanocubes provide potential application for biologic and chemical sensing based on Raman spectroanalysis.

  10. 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.

  11. Investigation of nanogap localized field enhancement in gold plasmonic structures

    NASA Astrophysics Data System (ADS)

    Debu, Desalegn Tadesse; Bauman, Stephen; Saylor, Cameron; Novak, Eric; French, David; Herzog, Joseph

    2015-03-01

    Nanogaps between plasmonic structures allow confining the localized electric field with moreenhancements. Based on previously implemented two-step lithography process, we introducea nano-masking technique to fabricate nanostructrues and nanogaps for various geometrical patterns. This new method can fabricate gold nanostructures as well as nanogaps that are less than 10nm, below the limiting scale of lithography. Simulation from finite element method (FEM) shows strong gap dependence of optical properties and peak enhancement of these devices. The fabricated plasmonic nanostructure provides wide range of potential future application including highly sensitive optical antenna, surface enhanced Raman spectroscopy and biosensing.

  12. Dendrimer functionalization of gold surface improves the measurement of protein-DNA interactions by surface plasmon resonance imaging.

    PubMed

    Pillet, Flavien; Sanchez, Aurore; Formosa, Cécile; Séverac, Marjorie; Trévisiol, Emmanuelle; Bouet, Jean-Yves; Anton Leberre, Véronique

    2013-05-15

    Surface Plasmon Resonance imaging (SPRi) is a label free technique typically used to follow biomolecular interactions in real time. SPRi offers the possibility to simultaneously investigate numerous interactions and is dedicated to high throughput analysis. However, precise determination of binding constants between partners is not highly reliable. We report here a dendrimer functionalization of gold surface that significantly improves selectivity of the detection of protein-DNA interactions. We showed that amino-gold surface functionalization with phosphorus dendrimers of fourth generation (G4) allowed complete coverage of the gold surface and the increase of the surface roughness. We optimized the conditions for DNA probe deposition to allow accurate detection of a well-known protein-DNA interaction involved in bacterial chromosome segregation. Using this G4-functionalized surface, the specificity of the SPRi response was significantly improved allowing discrimination between protein and DNA interactions of different strengths. Kinetic constants similar to those obtained with other techniques currently used in molecular biology were only obtained with the G4 dendrimer functionalized surface. This study demonstrated the benefit of using dendrimeric surfaces for sensitive high throughput SPRi analysis. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Carbohydrate Coating Reduces Adhesion of Biofilm-Forming Bacillus subtilis to Gold Surfaces

    PubMed Central

    Kesel, S.; Mader, A.; Seeberger, P. H.; Lieleg, O.

    2014-01-01

    The growth of bacterial biofilms in pipes and food tanks causes severe problems in industry. Biofilms growing on medical implants or catheters are of great concern, as they can cause serious infections and decrease the functionality of the medical device. The prevention of bacterial adhesion—the first step in colonization and biofilm formation—is therefore very important. Current research comprises alterations in surface properties, the prevention of adhesin biosynthesis, inhibition with receptor analogs, or the development of anti-adhesive vaccines. We present a new approach that allows us to study bacterial adhesion with high sensitivity in real-time while testing several different surfaces in parallel. Using the cantilever-array technique we demonstrate that coating of gold surfaces with mono- or disaccharides results in a reduction of the bacterial adhesion of the biofilm-forming bacterium Bacillus subtilis NCIB 3610 to these gold surfaces. This reduction in bacterial adhesion is independent of the studied carbohydrate. Using several mutant strains, we investigate the underlying molecular interactions, and our results suggest that adhesion to gold surfaces is mediated by thiol groups present in proteins of the bacterial cell membrane or biofilm matrix proteins expressed at low levels by the wild-type strain. Furthermore, our data indicate that the adhesion of B. subtilis NCIB 3610 to carbohydrate-coated gold surfaces is facilitated by interactions between carbohydrates installed on the cantilever gold surface and an exopolysaccharide expressed by this strain. Understanding general and specific contributions of molecular interactions mediating bacterial adhesion will enable its prevention in the future. PMID:25038098

  14. 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.

  15. 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

  16. Cytochrome c dynamics at gold and glassy carbon surfaces monitored by in situ scanning tunnel microscopy

    NASA Astrophysics Data System (ADS)

    Andersen, Jens E. T.; Møller, Per; Pedersen, Marianne V.; Ulstrup, Jens

    1995-02-01

    We have investigated the absorption of cytochrome c on gold and glassy carbon substrates by in situ scanning tunnel microscopy under potentiostatic control of both substrate and tip. Low ionic strength and potential ranges where no Faradaic current flows were used. Cyt c aggregates into flat composite structures of about 50 nm lateral extension at gold surfaces. The aggregates evolve in time, and structures resembling individual cyt c molecules can be distinguished in the space between the 50 nm structures. Cyt c aggregates also form at glassy carbon but have a different, unbroken character where cyt c both sticks well to the surface and exhibits notable mobility. The observations suggest that characteristic surface specific, internally mobile protein aggregates are formed at both surfaces and that in situ molecular resolution of the STM pictures may have been achieved.

  17. Femtosecond nonlinear ultrasonics in gold probed with ultrashort surface plasmons.

    PubMed

    Temnov, Vasily V; Klieber, Christoph; Nelson, Keith A; Thomay, Tim; Knittel, Vanessa; Leitenstorfer, Alfred; Makarov, Denys; Albrecht, Manfred; Bratschitsch, Rudolf

    2013-01-01

    Fundamental interactions induced by lattice vibrations on ultrafast time scales have become increasingly important for modern nanoscience and technology. Experimental access to the physical properties of acoustic phonons in the terahertz-frequency range and over the entire Brillouin zone is crucial for understanding electric and thermal transport in solids and their compounds. Here we report on the generation and nonlinear propagation of giant (1 per cent) acoustic strain pulses in hybrid gold/cobalt bilayer structures probed with ultrafast surface plasmon interferometry. This new technique allows for unambiguous characterization of arbitrary ultrafast acoustic transients. The giant acoustic pulses experience substantial nonlinear reshaping after a propagation distance of only 100 nm in a crystalline gold layer. Excellent agreement with the Korteveg-de Vries model points to future quantitative nonlinear femtosecond terahertz-ultrasonics at the nano-scale in metals at room temperature.

  18. Surface-enhanced Raman scattering study of the redox adsorption of p-phenylenediamine on gold or copper surfaces.

    PubMed

    de Carvalho, Dhieniffer Ferreira; da Fonseca, Bruno Guilherme; Barbosa, Ingrid Lopes; Landi, Sandra Marcela; de Sena, Lídia Ágata; Archanjo, Bráulio Soares; Sant'Ana, Antonio Carlos

    2013-02-15

    The adsorption of the p-phenylenediamine (PPD(+)) radical cation on gold or copper nanoparticle (NP) surfaces was studied through surface-enhanced Raman scattering (SERS) spectroscopy, excited at 1064 nm. The SERS spectra were obtained from gold or copper NPs after exposure to non-oxidized p-phenylenediamine (PPD) aqueous solution, in millimolar concentration. The gold NPs were synthesized as nanoshells involving silica cores (SiO(2)@Au) and the copper NPs were obtained in aqueous medium, undergoing surface oxidation with the formation of Cu(II) oxide nanoshell (Cu@CuO). In the latter, the oxidative adsorption of PPD(+) led to the reduction of the copper oxide, present on NP surface, allowing obtaining the PPD(+) SERS spectrum. The vibrational assignments of the SERS spectra of the adsorbate were performed using the results of Density Functional Theory calculations of the Raman frequencies, which together with the SERS surface selection rules, allowed to infer the adsorption geometry of PPD(+) radical cation on both metallic surfaces. This work stress the investigation of redox processes involved in the molecular adsorption is imperative for the interpretation of the SERS results, which is even more important when copper surfaces are studied. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Effect of Gold on the Corrosion Behavior of an Electroless Nickel/Immersion Gold Surface Finish

    NASA Astrophysics Data System (ADS)

    Bui, Q. V.; Nam, N. D.; Yoon, J. W.; Choi, D. H.; Kar, A.; Kim, J. G.; Jung, S. B.

    2011-09-01

    The performance of surface finishes as a function of the pH of the utilized plating solution was evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 wt.% NaCl solution. In addition, the surface finishes were examined by x-ray diffraction (XRD), and the contact angle of the liquid/solid interface was recorded. NiP films on copper substrates with gold coatings exhibited their highest coating performance at pH 5. This was attributed to the films having the highest protective efficiency and charge transfer resistance, lowest porosity value, and highest contact angle among those examined as a result of the strongly preferred Au(111) orientation and the improved surface wettability.

  20. Fabrication of Localized Surface Plasmon Resonance Fiber Probes Using Ionic Self-Assembled Gold Nanoparticles

    PubMed Central

    Wan, Miao; Luo, Pengfei; Jin, Jiayi; Xing, Jiong; Wang, Zhiyong; Wong, Stephen T. C.

    2010-01-01

    An nm-thickness composite gold thin film consisting of gold nanoparticles and polyelectrolytes is fabricated through ionic self-assembled multilayers (ISAM) technique and is deposited on end-faces of optical fibers to construct localized surface plasmon resonance (LSPR) fiber probes. We demonstrate that the LSPR spectrum induced by ISAM gold films can be fine-tuned through the ISAM procedure. We investigate variations of reflection spectra of the probe with respect to the layer-by-layer adsorption of ISAMs onto end-faces of fibers, and study the spectral variation mechanism. Finally, we demonstrated using this fiber probe to detect the biotin-streptavidin bioconjugate pair. ISAM adsorbed on optical fibers potentially provides a simple, fast, robust, and low-cost, platform for LSPR biosensing applications. PMID:22163561

  1. 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.

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

    SciTech Connect

    Walen, Holly

    2016-01-01

    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. 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.

  3. 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.

  4. Speciation of surface gold in pressure oxidized carbonaceous gold ores by TOF-SIMS and TOF-LIMS

    NASA Astrophysics Data System (ADS)

    Dimov, S. S.; Chryssoulis, S. L.; Sodhi, R. N.

    2003-01-01

    To the best of our knowledge, this is the first attempt ever to speciate gold preg-robbed by carbonaceous matter using a surface sensitive microbeam technique. This approach enables the direct determination of gold species sorbed on carbonaceous particulates thus providing a new tool in understanding the chemistry of gold sorption on carbon. The reasoning behind this effort was to study the detrimental effect chloride ions have on gold recovery by pressure oxidation of carbonaceous sulfide ores, a technology largely used by the mining industry. The characterization of the sorbed gold species involved three surface sensitive microbeam analytical techniques (TOF-SIMS, TOF-LIMS and XPS) providing confirmatory results for better accuracy. Optimum conditions for detection of gold compounds with minimum fragmentation by TOF-SIMS and TOF-LIMS mass spectrometers have been determined. A reference library of 16 major gold complexes with halogen, thiosulfate, cyanide and thiocyanate groups relevant to the gold recovery processes has been established. The most suitable of the microbeam techniques tested was found to be negative (-ve) ion TOF-LIMS, offering best sensitivity and a small analytical spot size.

  5. 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

  6. 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.

  7. 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.

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

    SciTech Connect

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

    2016-06-28

    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 H{sub 2}O{sub 2} as an oxidizer. The reshaping of these nanostructures has been demonstrated as a consequence of an oxidation process in which HGNSs are dissolved by H{sub 2}O{sub 2} 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.

  9. Surface-enhanced Raman scattering dendritic substrates fabricated by deposition of gold and silver on silicon.

    PubMed

    Cheng, Mingfei; Fang, Jinghuai; Cao, Min; Jin, Yonglong

    2010-11-01

    This paper reports a study on the preparation of gold nanoparticles and silver dendrites on silicon substrates by immersion plating. Firstly, gold was deposited onto silicon wafer from HF aqueous solution containing HAuCl4. Then, the silicon wafer deposited gold was dipped into HF aqueous solution of AgNO3 to form silver coating gold film. Scanning electron microscopy reveals a uniform gold film consisted of gold nanoparticles and rough silver coating gold film containing uniform dendritic structures on silicon surface. By SERS (surface-enhanced Raman scattering) measurements, the fabricated gold and silver coating gold substrates activity toward SERS is assessed. The SERS spectra of crystal violet on the fabricated substrates reflect the different SERS activities on gold nanoparticles film and silver coating gold dendrites film. Compared with pure gold film on silicon, the film of silver coating gold dendrites film significantly increased the SERS intensity. As the fabrication process is very simple, cost-effective and reproducible, and the fabricated silver coating gold substrate is of excellent enhancement ability, spatial uniformity and good stability.

  10. Revisiting Surface-Enhanced Raman Scattering on Realistic Lithographic Gold Nanostripes

    PubMed Central

    2013-01-01

    In this article, we investigate the Surface-Enhanced Raman Scattering (SERS) efficiency of methylene blue (MB) molecules deposited on gold nanostripes which, due to their fabrication by electron beam lithography and thermal evaporation, present various degrees of crystallinity and nanoscale surface roughness (NSR). By comparing gold nanostructures with different degrees of roughness and crystallinity, we show that the NSR has a strong effect on the SERS intensity of MB probe molecules. In particular, the NSR features of the lithographic structures significantly enhance the Raman signal of MB molecules, even when the excitation wavelength lies far from the localized surface plasmon resonance (LSPR) of the stripes. These results are in very good agreement with numerical calculations of the SERS gain obtained using the discrete dipole approximation (DDA). The influence of NSR on the optical near-field response of lithographic structures thus appears crucial since they are widely used in the context of nano-optics or/and molecular sensing. PMID:24340104

  11. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  13. Reciprocal space engineering with hyperuniform gold disordered surfaces

    NASA Astrophysics Data System (ADS)

    Castro-Lopez, Marta; Gaio, Michele; Sellers, Steven; Gkantzounis, George; Florescu, Marian; Sapienza, Riccardo

    2017-06-01

    Hyperuniform geometries feature correlated disordered topologies which follow from a tailored k-space design. Here, we study gold plasmonic hyperuniform disordered surfaces and, by momentum spectroscopy, we report evidence of k-space engineering on both light scattering and light emission. Even if the structures lack a well-defined periodicity, emission and scattering are directional in ring-shaped patterns. The opening of these rotational-symmetric patterns scales with the hyperuniform correlation length parameter as predicted via the spectral function method.

  14. Optical Properties of Gold Nanoparticle Assemblies on a Glass Surface

    NASA Astrophysics Data System (ADS)

    Stetsenko, M. O.; Rudenko, S. P.; Maksimenko, L. S.; Serdega, B. K.; Pluchery, O.; Snegir, S. V.

    2017-05-01

    The assemblies of cross-linked gold nanoparticles (AuNP) attract lot of scientific attention due to feasible perspectives of their use for development of scaled contact electrodes. Here, we developed and tested method of solid-state formation of dimers created from small AuNP ( 18 nm) cross-linked with 1.9-nonadithiol (NDT) molecules. The morphology of created coating of a glass surface and its optical-polarization properties have been studied in detail by combination of scanning electron microscopy, atomic force microscopy, UV-visible spectroscopy, and modulation-polarization spectroscopy.

  15. Surface-Enhanced Raman Scattering of Hydroxyproline in Gold Colloids

    NASA Astrophysics Data System (ADS)

    Guerrero, Ariel R.; Aroca, Ricardo F.

    2010-08-01

    Surface-Enhanced Raman Scattering (SERS) of amino acids has proven a challenging task. The SERS of biomolecules and the formation of a reliable SERS data-base for medical application has shown to be a very challenging task for two reasons: first, the functional groups in proteins, lipid and sugars do not usually include aromatic moieties or chromophores absorbing in the visible (with intrinsic very large cross sections), and therefore, large enhancement factors are needed for ultrasensitive analysis. Second, the biomolecule-metal surface interaction leads to active surface photochemistry, photoisomerization or photodissociation, thus hindering the reproducibility of the experiment. In this work, we have employed hydroxyproline (Hyp) as our problem molecule, and tackled the problem of reproducibility by employing gold colloids instead of the usual silver to achieve SERS. We slightly modified the procedure described by Lee and Meisel to obtain the colloid, and concentrated the gold particles by centrifuging the colloid at 14000 rpm by 7 minutes. The SERS spectra show distinctive bands of Hyp, assigned by comparison to normal Raman spectra and DFT calculations. Repeated measurements using this procedure showed no significant variation in the spectra obtained.

  16. Gold nanoshells for surface enhanced Raman spectroscopy and drug delivery

    NASA Astrophysics Data System (ADS)

    Barhoumi, Aoune

    Gold nanoshells are tunable plasmonic nanostructures consisting of spherical silica cores wrapped with thin layer of Au. Based on the size of the Au layer with respect to the silica core, gold nanoshells can resonantly absorb or scatter light at any wavelength on the visible or infrared. On resonance, gold nanoshells interact strongly with light to give rise to collective oscillations of the free electrons against the background of the ionic core, phenomena known as localized surface plasmons. The free electron oscillation creates surface plasmon multimodes of various orders. As a result, the average local near field surrounding the Au nanoshell is enhanced. The local field enhancement has been extensively used in different applications. In this work, the local near-field is used to enhance the Raman spectroscopy of DNA and explore the different modes attributed to the base composition and structure of the DNA sequence. We showed that urface enhanced Raman spectroscopy of DNA is dominated by the adenine modes regardless of the base composition of the DNA sequence, a property that we have used to develop a DNA label-free detection system. As absorbers, plasmon-resonant Au nanoshells can convert absorbed light into heat. As a consequence, the temperature on the Au nanoshell surface increases dramatically. This property is used to light-trigger the release of variety of therapeutic molecules such as single stranded DNA, siRNA and small molecules. We demonstrated that the local heat can be used to dehybridize double stranded DNA attached to the Au surface via a thiol moiety on one of the DNA strands. The complementary sequence (therapeutic sequence) is released at temperature lower than the standard melting temperature of same DNA sequence. Moreover, small molecules (DAPI) which were initially intercalated on the double stranded DNA attached to the Au surface were successfully released due to the heat generated around the nanoshell surface. Finally, siRNA molecules

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

    PubMed Central

    2013-01-01

    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. PMID:24172147

  18. Surface-enhanced Raman scattering spectra of tomato epidermis on gold/ silver sol active substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Chen, Zhenyi; Chen, Na; Hu, Ling; Zhu, Hongfei; Liu, Shupeng; Guo, Qiang

    2011-12-01

    In this paper, tomato epidermis' surface-enhanced Raman scattering spectra were measured on gold and silver active substrates and analyzed. Preparing and using gold sol and silver sol in similar particle diameters (about 50-60nm), three comparable Raman spectra were obtained. Silver sol and gold sol can both increase Raman scattering signal of tomato epidermis. Through the Raman spectra, silver sol has greater enhancement ability than gold sol to tomato epidermis.

  19. 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.

  20. 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.

  1. Using Impedance Measurements to Characterize Surface Modified with Gold Nanoparticles

    PubMed Central

    MacKay, Scott; Abdelrasoul, Gaser N.; Tamura, Marcus; Yan, Zhimin

    2017-01-01

    With the increased practice of preventative healthcare to help reduce costs worldwide, sensor technology improvement is vital to patient care. Point-of-care (POC) diagnostics can reduce time and lower labor in testing, and can effectively avoid transporting costs because of portable designs. Label-free detection allows for greater versatility in the detection of biological molecules. Here, we describe the use of an impedance-based POC biosensor that can detect changes in the surface modification of a micro-fabricated chip using impedance spectroscopy. Gold nanoparticles (GNPs) have been employed to evaluate the sensing ability of our new chip using impedance measurements. Furthermore, we used impedance measurements to monitor surface functionalization progress on the sensor’s interdigitated electrodes (IDEs). Electrodes made from aluminum and gold were employed and the results were analyzed to compare the impact of electrode material. GNPs coated with mercaptoundecanoic acid were also used as a model of biomolecules to greatly enhance chemical affinity to the silicon substrate. The portable sensor can be used as an alternative technology to ELISA (enzyme-linked immunosorbent assays) and polymerase chain reaction (PCR)-based techniques. This system has advantages over PCR and ELISA both in the amount of time required for testing and the ease of use of our sensor. With other techniques, larger, expensive equipment must be utilized in a lab environment, and procedures have to be carried out by trained professionals. The simplicity of our sensor system can lead to an automated and portable sensing system.

  2. Molecular dynamics simulation studies of gold nano-cluster on silicon (001) surface

    NASA Astrophysics Data System (ADS)

    Sarangi, S. S.; Satyam, P. V.; Nayak, S. K.; Mahanti, S. D.

    2017-02-01

    Classical molecular dynamics simulations with modified embedded atom method model has been carried out to understand the interfacial behavior of a gold(Au) nano-cluster on a silicon(Si) surface. For illustration, a gold nano-cluster (NC) consisting of 108 atoms has been chosen on the Si (001) surface. We have investigated on the process of melting of this NC, the temperature dependent intermixing of Au and Si, and the diffusion of Au atoms into the Si substrate. It has been observed that the NC becomes semi-spherical around the room temperature and the melting process started around 450 K. In order to examine the substrate effect on the melting point temperature of the gold NC, a similar NC has been studied in vacuum. The melting point temperature of this free NC is found to be around 480 K. The observed suppression of melting temperature (by 30 K) for the supported NC can be understood in terms of substrate induced change in morphology. We observe inter-diffusion between gold and silicon atoms for temperatures greater than 650 K.

  3. Molecular dynamics simulation studies of gold nano-cluster on silicon (001) surface

    NASA Astrophysics Data System (ADS)

    Sarangi, S. S.; Satyam, P. V.; Nayak, S. K.; Mahanti, S. D.

    2017-08-01

    Classical molecular dynamics simulations with modified embedded atom method model has been carried out to understand the interfacial behavior of a gold(Au) nano-cluster on a silicon(Si) surface. For illustration, a gold nano-cluster (NC) consisting of 108 atoms has been chosen on the Si (001) surface. We have investigated on the process of melting of this NC, the temperature dependent intermixing of Au and Si, and the diffusion of Au atoms into the Si substrate. It has been observed that the NC becomes semi-spherical around the room temperature and the melting process started around 450 K. In order to examine the substrate effect on the melting point temperature of the gold NC, a similar NC has been studied in vacuum. The melting point temperature of this free NC is found to be around 480 K. The observed suppression of melting temperature (by 30 K) for the supported NC can be understood in terms of substrate induced change in morphology. We observe inter-diffusion between gold and silicon atoms for temperatures greater than 650 K.

  4. Infrared gold alloy brazing on titanium and Ti-6Al-4V alloy surfaces and its application to removable prosthodontics.

    PubMed

    Wakabayashi, N; Ai, M; Iijima, K; Takada, Y; Okuno, O

    1999-09-01

    This study investigated the area size of the flow of a gold braze alloy on commercially pure titanium and Ti-6Al-4V alloy plates, and elemental composition at the interface was determined. In the second part of this study, the tensile strengths of titanium plates brazed using a gold alloy were investigated. Chips of Type IV gold alloy and silver braze alloys were melted onto commercially pure titanium and Ti-6Al-4V surfaces in a dental infrared radiation unit. Flow area of each braze alloy was measured using a digital image analyzer. Tensile specimens (n = 5) were also prepared by infrared brazing using the braze alloys. Five specimens for each combination of the two titanium plates and the two braze alloys were subjected to tensile loading using a Universal testing machine. Electronprobe microanalysis of x-rays at cross-section of the brazed joints to determine elemental composition across the interface, as well as scanning electron microscopic observation at the fracture surfaces, were also conducted. The braze alloys flowed well and spread over the Ti and Ti-6Al-4V plates. Braze alloy type significantly influenced flow, and the gold alloy flowed less on the titanium materials. The mean tensile strengths of Ti and Ti-6Al-4V plates brazed using the gold braze alloy were 219 MPa and 417 MPa, respectively. The fracture surfaces of Ti-6Al-4V specimens with the gold braze alloy exhibited typical ductile behavior. Ti with the same braze alloy showed brittle surfaces. A greater concentration of Cu was found at the Ti with gold braze interface. The flow and the tensile strength of the gold alloy coating on titanium surface by means of an infrared brazing is adequate for dental use.

  5. 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.

  6. Surface coating effects on the assembly of gold nanospheres

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    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.

  7. 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.

  8. Simultaneous anomalous reflection and quartz-crystal microbalance measurements of protein bindings on a gold surface.

    PubMed

    Manaka, Yuichi; Kudo, Yukihiko; Yoshimine, Hiroshi; Kawasaki, Takayoshi; Kajikawa, Kotaro; Okahata, Yoshio

    2007-09-14

    Protein bindings onto a gold surface were detected simultaneously by QCM (delta F(water)) and anomalous reflection (deltaR) of gold on the same surface in aqueous solutions; the obtained delta F(water)/deltaR values correlated with surface areas and viscosity of proteins.

  9. The pH effect on black spots in surface finish: Electroless nickel immersion gold

    NASA Astrophysics Data System (ADS)

    Won, Yong Sun; Park, Sung Soo; Lee, Jinuk; Kim, Jong-Yun; Lee, Seong-Jae

    2010-10-01

    In order to understand the black spot generation after electroless nickel immersion gold (ENIG) plating, we investigated the pH effect with a combined approach of experiments and computer aided engineering (CAE). As the pH is increased in IG plating solution, the deprotonation of citric acid as chelating agent is enhanced to stabilize the solution by producing Ni-citrate complex ion. For the substitution reaction between nickel and gold, excess citrate ions (deprotonated citric acids) are adsorbed along nodal boundaries of Ni-P layer to decrease the surface reactivity. Since the low reactivity decreases the overall growth rate, the resulting homogeneous Au layer growth avoids the unfavorable galvanic cell corrosion to control black spot. Based on molecular orbital method and kinetic Monte Carlo calculation, our computational approach well explained the capability of citric acid as chelating agent and the Au growth rate along the nodal boundaries of Ni-P layer depending on the surface reactivity.

  10. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    PubMed

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

    2015-11-05

    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.

  13. Propulsion of gold nanoparticles with surface plasmon polaritons: evidence of enhanced optical force from near-field coupling between gold particle and gold film.

    PubMed

    Wang, Kai; Schonbrun, Ethan; Crozier, Kenneth B

    2009-07-01

    We experimentally demonstrate the enhanced propulsion of gold nanoparticles by surface plasmon polaritons (SPPs). Three dimensional finite difference time domain (FDTD) simulations indicate considerably enhanced optical forces due to the field enhancement provided by SPPs and the near-field coupling between the gold particles and the film. This coupling is an important part of the enhanced propulsion phenomenon. Finally, the measured optical force is compared with that predicted by FDTD simulations and proven to be reasonable.

  14. Spectroscopic investigation on porphyrins nano-assemblies onto gold nanorods

    NASA Astrophysics Data System (ADS)

    Trapani, Mariachiara; De Luca, Giovanna; Romeo, Andrea; Castriciano, Maria Angela; Scolaro, Luigi Monsù

    2017-02-01

    The interaction between gold nanorods (Au NRs), synthesized by a conventional seeded growth protocol, and the anionic tetrakis-(4-sulfonatophenyl)porphyrin (TPPS4) has been investigated through various spectroscopic techniques. At neutral pH, the formation of H-aggregates and the inclusion of porphyrin monomers in CTAB micelles covering the nanorods have been evidenced. Under mild acidic conditions (pH = 3) a nano-hybrid assembly of porphyrin J-aggregates and Au NRs has been revealed. For the sake of comparison, Cu(II) and Zn(II) metal porphyrin derivatives as well as a cationic porphyrin have been studied in the same experimental conditions, showing that: i) CuTPPS4 forms porphyrin H-dimers onto the Au NRs; ii) ZnTPPS4 undergoes to demetallation, followed by acidification of the central core and eventually aggregation onto Au NRs; iii) cationic porphyrin does not interact with Au NRs.

  15. Two-dimensional ultrathin gold film composed of steadily linked dense nanoparticle with surface plasmon resonance

    PubMed Central

    2012-01-01

    Background Noble metallic nanoparticles have prominent optical local-field enhancement and light trapping properties in the visible light region resulting from surface plasmon resonances. Results We investigate the optical spectral properties and the surface-enhanced Raman spectroscopy of two-dimensional distinctive continuous ultrathin gold nanofilms. Experimental results show that the one- or two-layer nanofilm obviously increases absorbance in PEDOT:PSS and P3HT:PCBM layers and the gold nanofilm acquires high Raman-enhancing capability. Conclusions The fabricated novel structure of the continuous ultrathin gold nanofilms possesses high surface plasmon resonance properties and boasts a high surface-enhanced Raman scattering (SERS) enhancement factor, which can be a robust and cost-efficient SERS substrate. Interestingly, owing to the distinctive morphology and high light transmittance, the peculiar nanofilm can be used in multilayer photovoltaic devices to trap light without affecting the physical thickness of solar photovoltaic absorber layers and yielding new options for solar cell design. PMID:23259927

  16. 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

  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. 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.

  19. The Surface Morphology Characterization of Electroless Nickel Immersion Gold Under Bump Metallurgy (UBM) Using SEM

    SciTech Connect

    Arshad, M. K. Md; Isa, M. N. Md; Sohiful, Z. M. A.

    2007-05-09

    This paper presents the surface morphology characterization at each process step in electroless nickel immersion gold (ENIG) deposition using Scanning Electron Microscope (SEM). The characterization start at initial bond pad, followed by cleaning, activation, first zincation, zinc removal, second zincation, electroless nickel and lastly immersion gold process. The result shows that the surface morphology of initial bond pad starts to change with deposition of zinc layer and further changes with deposition of nickel and gold layer.

  20. Stabilization of Gold Nanorods (GNRs) in Aqueous and Organic Environments by Select Surface Functionalization

    DTIC Science & Technology

    2016-01-01

    ARL-TR-7581 ● JAN 2016 US Army Research Laboratory Stabilization of Gold Nanorods (GNRs) in Aqueous and Organic Environments by...7581 ● JAN 2016 US Army Research Laboratory Stabilization of Gold Nanorods (GNRs) in Aqueous and Organic Environments by Select Surface... Gold Nanorods (GNRs) in Aqueous and Organic Environments by Select Surface Functionalization 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  1. 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.

  2. Evaluation of Nanoporous Gold with Controlled Surface Structures for Laser Desorption Ionization (LDI) Analysis: Surface Area Versus LDI Signal Intensity

    NASA Astrophysics Data System (ADS)

    Jin, Jang Mi; Choi, Suhee; Kim, Young Hwan; Choi, Man Ho; Kim, Jongwon; Kim, Sunghwan

    2012-09-01

    The structural effect of a nanoporous gold (NPG) surface on the signal intensities of laser desorption ionization-mass spectrometry (LDI-MS) were investigated using NPG surfaces with controlled structures. The relationship between surface area and LDI efficiency was compared and evaluated. Comparisons between bare flat gold and NPG surfaces show that nanostructures increased LDI efficiency. We also found that the LDI signal decreased with increasing depth of nanoporous layers, thus increasing the surface area. This result agrees with a previous report (Shin J. A. et al., J. Am. Soc. Mass Spectrom. 2010, 21, 989) in which the LDI efficiency of small molecules decreased for ZnO wires with longer lengths. This observation was explained by the penetration and deposition of samples into locations inaccessible to photons because of structural screening. The LDI-MS analysis of oils with NPG surfaces (but without matrix) showed the same trend whereby the NPG with about a 200 nm depth of porous area showed the highest sensitivity. This study clearly shows that the active surface area for solution chemistry can differ from LDI-MS and that NPGs can function as a substrate for LDI oil analysis.

  3. Self-organization of gold nanoparticles on silanated surfaces.

    PubMed

    Kyaw, Htet H; Al-Harthi, Salim H; Sellai, Azzouz; Dutta, Joydeep

    2015-01-01

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

  4. Multiple Surface Plasmon Modes for Gold/Silver Alloy Nanorods

    SciTech Connect

    Bok, Hye-Mi; Shuford, Kevin L; Kim, Sungwan; Kim, Seong Kyu; Park, Sungho

    2009-01-01

    Alloy nanorods consisting of bimetallic gold and silver are synthesized by employing the electrochemical codeposition of Au/Ag alloy materials into the pores of anodized aluminum oxide templates. This paper presents the variation of localized surface plasmon resonance (LSPR) modes of the Au{sub x}/Ag{sub 1-x} alloy nanorods as a function of relative compositions of Au and Ag. Transverse and multiple longitudinal modes were observed when the length was longer than ca. 300 nm. For a given length, the transverse LSPR mode systematically blue-shifted as the Ag portion increased, while there was little variation in peak positions of the longitudinal LSPR modes. The optical properties of the Au{sub x}/Ag{sub 1-x} alloy nanorods were calculated using the discrete dipole approximation and showed a good agreement with the experimental measurements.

  5. Self-organization of gold nanoparticles on silanated surfaces

    PubMed Central

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

    2015-01-01

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

  6. Electrochemical synthesis of gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode and their application

    NASA Astrophysics Data System (ADS)

    Song, Y. Z.; Li, X.; Song, Y.; Cheng, Z. P.; Zhong, H.; Xu, J. M.; Lu, J. S.; Wei, C. G.; Zhu, A. F.; Wu, F. Y.; Xu, J.

    2013-01-01

    Gold nanoparticles on the surface of multi-walled carbon nanotubes with glassy carbon electrode were prepared using electrochemical synthesis method. The thin films of gold Nanoparticles/multi-walled carbon nanotubes were characterized by scanning electron microscopy, powder X-ray diffraction, and cyclic voltammetry. Electrochemical behavior of adrenaline hydrochloride at gold nanoparticles/multi-walled carbon nanotube modified glassy carbon electrode was investigated. A simple, sensitive, and inexpensive method for determination of adrenaline hydrochloride was proposed.

  7. Flexible Gold Nanocone Array Surfaces as a Tool for Regulating Neuronal Behavior.

    PubMed

    Toma, Mana; Belu, Andreea; Mayer, Dirk; Offenhäusser, Andreas

    2017-06-01

    Accelerated neurite outgrowth of rat cortical neurons on a flexible and inexpensive substrate functionalized with gold nanocone arrays is reported. The gold nanocone arrays are fabricated on Teflon films by a bottom-up approach based on colloidal lithography followed by deposition of a thin gold layer. The geometry of nanocone arrays including height and pitch is controlled by the overall etching time and template polystyrene beads size. Fluorescence microscopy studies reveal high viability and significant morphological changes of the neurons on the structured surfaces. The elongation degree of neurite is maximized on the nanocone arrays created with 1 µm polystyrene beads by a factor of two with respect to the control. Furthermore, the interface between the neurons and the nanocones is investigated by scanning electron microscopy and focused ion beam cross-sectioning. The detailed observation of the neuron/nanocone interfaces reveals the morphological similarity between the nanocone tips and the neuronal processes, the existence of interspace at the interface between the cell body and the nanocones, and neurite bridging among the neighboring structures, which may induce the acceleration of neurite outgrowth. The flexible gold nanocone arrays can be a good supporting substrate of neuron culture with noble electrical and optical properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Comparisons between Surface-Enhanced Raman and Surface Infrared Spectroscopies for Strongly Perturbed Adsorbates: Thiocyanate at Gold Electrodes.

    DTIC Science & Technology

    1986-07-30

    tu. 3. iptt FCSa, s CATALOG NUtof SBetween Surface -Enhanced Raman anj$ YEO EOTI EIDCvfr Surface Infared Spectroscopies for StrongiV Technical Report...REPORT 8 49 0Comparisons Between Surface-Enhanced Raman and Surface Infrared Spectroscopies for Strongly Perturbed Adsorbates: Thiocyanate at Gold...for thiocyanate adsorbed at the gold-aqueous interface is examined by both surface-enhanced Raman spectroscopy (SERS) and subtractively normalized

  9. In situ GISAXS investigation of gold sputtering onto a polymer template.

    PubMed

    Metwalli, E; Couet, S; Schlage, K; Röhlsberger, R; Körstgens, V; Ruderer, M; Wang, W; Kaune, G; Roth, S V; Müller-Buschbaum, P

    2008-04-15

    Microphase-separation structures in mixed diblock-triblock copolymer thin films are used for the incorporation of gold atoms inside the polymer matrix via sputtering of gold. Polystyrene (PS) spheres are arranged in a liquidlike type with a well defined nearest neighbor distance inside a polyisoprene matrix acting as a template for directing the gold atoms. Sputtering conditions are selected with a very low sputtering rate to avoid clustering in the atmosphere so that gold reaches the polymer surface in its atomic state. Due to the mobility of the gold atoms and the selective interaction with the PS parts of the microphase separation structure, gold is accumulated inside the polymer film in the PS spheres, as probed in situ with grazing incidence small-angle X-ray scattering (GISAXS). Nominally 4.3 A of gold is deposited, which by diffusion is spread out vertically over a thickness of 280 nm. UV-vis spectroscopy reveals a small blue shift for the gold sputtered polymer film. Atomic force microscopy proves the absence of gold clusters on the film surface. For low sputtering rate, GISAXS proves good sensitivity for gold migration inside the polymer film and opens new possibilities for studying polymer-metal interaction.

  10. Scanning probe studies of water nucleation on aluminum oxide and gold surfaces

    NASA Astrophysics Data System (ADS)

    Missert, N.; Copeland, R. G.

    2008-01-01

    The nucleation of nanoscale water at surfaces in humid environments is sensitive to several factors, including the details of the surface morphology, ability of the surface to hydrate and the presence of contaminants. Tapping mode atomic force microscopy was used to investigate the nucleation process as a function of relative humidity (RH) on passive aluminum and gold thin films. Films exposed to the ambient environment prior to RH exposure showed discrete structures with lateral sizes ranging from 10 to 100 nm only at RH > 70%. These structures formed preferentially at grain boundaries, triple points and regions with significant topography such as protruding grains. The morphology of the passive aluminum surface is permanently altered at the sites where discrete structures were observed; nodules with heights ranging from 0.5 to 2 nm persist even after reducing the RH to <2%. The gold surface does not show such a permanent change in morphology after reducing the RH. Passive aluminum films exposed to high RH immediately after growth (e.g. no ambient exposure) do not show discrete structures even at the highest RH exposures of 90%, suggesting a hydrophilic surface and the importance of surface hydrocarbon contaminants in affecting the distribution of the water layer.

  11. Ultrafast thermal analysis of surface functionalized gold nanorods in aqueous solution.

    PubMed

    Huang, Jingyu; Park, Jonglo; Wang, Wei; Murphy, Catherine J; Cahill, David G

    2013-01-22

    The thermal conductivity and heat capacity of surfactant and polyelectrolyte coatings of gold nanorods (GNRs) in aqueous solution are investigated by transient absorption, following femtosecond pumping of the longitudinal localized surface plasmons. Surfactant and polyelectrolyte layer thicknesses are measured by dynamic light scattering (DLS). The GNRs are initially coated with a bilayer of the quaternary ammonium surfactant cetyltrimethylammonium bromide (CTAB). The rate of change of the absorption of gold nanorods in aqueous solution varies with the probe laser wavelength due to the shift in the plasmon resonance created by heating of media around the particles. The cooling dynamics of gold nanorods are best measured by tuning the pump-probe laser wavelength to the absorption peak of the sample. The heat capacity of the surfactant layer is 2.0 ± 0.3 J cm(-3) K(-1); the thermal conductivity of the surfactant layer drops from 0.24 to 0.18 W m(-1) K(-1) at solution concentrations above the CTAB critical micelle concentration (cmc). Layer-by-layer polyelectrolyte coatings using poly(acrylic acid) (PAA) and polyallyamine hydrochloride (PAH) increase the thermal conductivity and heat capacity of the surface layer. PAH-terminated layers have increased thickness, thermal conductivity, and heat capacity relative to PAA-terminated layers; this effect is attributed to greater water penetration into PAH-terminated surface layers.

  12. Gold nanoparticles surface modification using BSA and cysteine

    NASA Astrophysics Data System (ADS)

    Cardoso-Avila, P. E.; Pichardo-Molina, J. L.; Upendra Kumar, K.; Barbosa-Sabanero, G.; Barbosa-Garcia, O.

    2011-08-01

    Metal nanometer-size particles show intriguing optical properties which depend on their shape, size and local environment. For these reasons, these materials have received a lot of attention in different scientific areas, and several applications can be found, for example: fabrication of bio-sensor, electronic devices, catalysis and new drugs. However, in the case of biomedical applications, metallic nanoparticles need to satisfy several requirements: bio-compatibility, stability and functionality. To satisfy these requirements, metallic nanoparticles need to be modified in their surfaces. In this work we report the synthesis and the modification of gold nanoparticles (GNPs) surface. GNPs were fabricated following the Turkevich's method, and the bio-conjugation (surface modification) was done using cysteine and bovine serum albumin (BSA). Our results of Uv-vis spectroscopy show that BSA and cysteine permit to increase the stability of GNPs in presence of NaCl, the stability is function of BSA concentration. Also to verify the bio-conjugation we used Raman spectroscopy and gel electrophoresis.

  13. Surface packing determines the redox potential shift of cytochrome c adsorbed on gold.

    PubMed

    Zanetti-Polzi, Laura; Daidone, Isabella; Bortolotti, Carlo Augusto; Corni, Stefano

    2014-09-17

    Thermodynamic and dynamic properties of iso-1-cytochrome c covalently bound to a bare gold surface are here investigated by large scale atomistic simulations. The reduction potential of the protein for low and high surface concentrations is calculated showing a good agreement with experimental estimates. The origin of the dependence of the reduction potential on the surface concentration is investigated and is demonstrated to stem from the changing polarizability of the environment surrounding the protein, a mechanism reminiscent of crowding effects. Moreover, structural analyses are performed revealing relevant changes induced by the presence of the electrode on the dynamic properties of cytochrome c. In particular, one of the two cavities previously identified on the protein surface [Bortolotti et al. J. Am. Chem. Soc., 2012, 134, 13670], and that reversibly open in cytochrome c freely diffusing in solution, is found to be deformed when the protein is adsorbed on gold. This modification exemplifies a mechanism that potentially leads to changes in the protein properties by surface-induced modification of its dynamical behavior.

  14. Magnetic resonance investigation of gold-doped and gold-hydrogen-doped silicon

    NASA Astrophysics Data System (ADS)

    Huy, P. T.; Ammerlaan, C. A.

    2002-10-01

    Three paramagnetic centers related to gold have been observed in gold-doped and gold-doped hydrogenated silicon by magnetic resonance. One spectrum, labeled Si-NL62, corresponding to a center with monoclinic-I symmetry, presents fourfold splitting due to the hyperfine interaction with one gold atom and further hyperfine interaction with two silicon nearest-neighbor atoms. After being diffused with hydrogen in a wet atmosphere of water vapor at 1300 °C for about 30 min, a second electron paramagnetic resonance spectrum, labeled Si-NL63, is detected, also of the monoclinic-I symmetry. The spectrum of the center is characterized by a complex hyperfine structure, in which, depending on magnetic field orientation, a sevenfold splitting with the intensities 1:2:3:4:3:2:1, a fourfold splitting 4:4:4:4, and other more arbitrary structures are observed. Extra small splitting is observed in the sample diffused with deuterium, indicating hydrogen involvement in the microscopic structure of the Si-NL63 center. Under band gap illumination the third center of a one-gold-two-hydrogen complex is observed. The center, labeled Si-NL64, has low triclinic symmetry and features the hyperfine interactions with one gold and two nearly equivalent hydrogen atoms. This results in a (1:2:1):(1:2:1):(1:2:1):(1:2:1) structure of each group of spectral lines. Spin-Hamiltonian parameters for the three spectra are determined and microscopic models are discussed.

  15. Nd:YAG laser penetration into cast titanium and gold alloy with different surface preparations.

    PubMed

    Watanabe, I; Baba, N; Chang, J; Chiu, Y

    2006-06-01

    This study investigated the effect of surface preparation on the Nd:YAG laser penetration into cast titanium and gold alloy. Cast blocks of each metal were given four different surface preparations: (i) coloured with black marker; (ii) air-abraded with 50 microm Al2O3; (iii) ground with SiC points and (iv) polished with 1 microm Al2O3 (mirror-polished). Two blocks with each of the surface preparations were abutted and laser-welded at their interface using the voltages of 210-260 V in increments of 10 V. After the welded blocks were mechanically separated, the laser penetration was measured using computer graphics. Regardless of the surface preparation, an increase in voltage increased the laser penetration for both metals. The laser penetration into titanium prepared with black marker and air-abrasion was significantly deeper than into the titanium ground with SiC points and mirror-polished. Although there were no statistical differences in penetration among the surface preparations for the gold alloy, the penetration in the mirror-polished specimens was shallower than any of the other preparation methods at higher voltages of 240-260 V. The results obtained in this study suggested that broken metal frameworks with finished surfaces should be painted with black marker or air-abraded before laser welding.

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

    PubMed

    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 10(7). 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. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Low energy slowing down of nanosize copper clusters on gold (1 1 1) surfaces

    NASA Astrophysics Data System (ADS)

    Lei, H.; Hou, Q.; Hou, M.

    2000-04-01

    The slowing down of copper clusters formed by 440 atoms on a gold (1 1 1) surface is studied in detail by means of molecular dynamics. The atomic classical molecular dynamics is based on the second moment approximation of the tight binding model and, in addition, accounts for the electron-phonon coupling in the frame of the Sommerfeld theory of metals. The slowing down energy range is 0-1 eV/atom, which is characteristic of low energy cluster beam deposition (LECBD). A pronounced epitaxy of the copper clusters is found. However, their morphology is significantly energy dependent. The structure and the radial pair correlation functions are used to study the details of the epitaxial properties as well as the pronounced relaxation in the interfacial cluster atom positions due to the lattice mismatch between copper and gold. The effect of the cluster and substrate average temperature is investigated and can be distinguished from the kinetic effect of the cluster impact.

  18. 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.

  19. Obliquely Deposited Gold Nanohelices on Lithography-Free Prepared Nanoseeded Surfaces

    NASA Astrophysics Data System (ADS)

    Jen, Yi-Jun; Liu, Wei-Chih; Hsiao, Chih-Yung; Lin, Po-Cheng; Yu, Chia-Liang; Chan, Teh-Li

    2017-08-01

    A substrate surface on which gold particles are distributed is prepared by annealing an ultra-thin gold film to enable glancing angle deposition. By cooling the substrate and controlling its spin rate, two spiral-like and one screw-like gold nanohelix arrays are grown upon the seeded surfaces. The mean helix radius and pitch length are reduced to 17 and 55 nm, respectively. The g-factor of the three nanohelix arrays is measured here and associated circular dichroism peak blue shifts occur as the gold helices shrink.

  20. Gold nanoparticle based surface enhanced fluorescence for detection of organophosphorus agents

    NASA Astrophysics Data System (ADS)

    Dasary, Samuel S. R.; Rai, Uma S.; Yu, Hongtao; Anjaneyulu, Yerramilli; Dubey, Madan; Ray, Paresh Chandra

    2008-07-01

    Organophosphorus agents (OPA) represent a serious concern to public safety as nerve agents and pesticides. Here we report the development of gold nanoparticle based surface enhanced fluorescence (NSEF) spectroscopy for rapid and sensitive screening of organophosphorus agents. Fluorescent from Eu 3+ ions that are bound within the electromagnetic field of gold nanoparticles exhibit a strong enhancement. In the presence of OPA, Eu 3+ ions are released from the gold nanoparticle surface and thus a very distinct fluorescence signal change was observed. We discussed the mechanism of fluorescence enhancement and the role of OPA for fluorescence intensity change in the presence of gold nanoparticles.

  1. Simulation studies of electroless metal deposition using gold nano-clusters on polymeric surfaces

    NASA Astrophysics Data System (ADS)

    Lively, Mike; Bhattacharya, Aniket; Grabill, Chris; Kuebler, Stephen M.; Dutta, Aniruddha; Heinrich, Helge

    2010-03-01

    We report lattice Monte Carlo (MC) simulation studies of deposition of metallic silver on randomly distributed gold nano clusters on a polymeric surface. The gold nano-clusters act as seeds for further deposition of silver atoms. We assume ballistic growth for the growth of metallic silver on gold clusters but treat the lateral growth (which eventually form bridges among original clusters) with different rules and study the evolving morphologies of the deposited silver atoms as a function of the surface density and the size distribution of gold nano-clusters and compare simulation results with those obtained from TEM studies of the prepared samples.

  2. PIXE, XRF and GRT for the global investigation of ancient gold artefacts

    NASA Astrophysics Data System (ADS)

    Demortier, Guy; Morciaux, Yvon; Dozot, Daphné

    1999-04-01

    The study of ancient gold jewellery artefacts often requires surface and bulk characterisation using non-destructive methods. Curators of musea or owners of private collections do not allow any sampling (even at microscopic level) for the investigation of the bulk of massive gold objects, which often contain less noble metals. Neutron Activation Analysis of the whole sample is generally prohibited even if no danger may be feared from delayed radioactivity. Weight and density measurements are easy and convenient to assert the presence of a cavity or a core of lower density. A combination of PIXE (at various incident proton energies in a non-vacuum geometry) for the elemental distribution in the first 10 μm below the surface, XRF (induced by γ-rays of 59 keV and of higher energy from a source of 241Am) to investigate the material up to several hundreds of microns, and GRT (Gamma Ray Transmission) of 662 keV photons ( 137Cs) may give a more complete answer on the surface and bulk compositions of the artefacts. Examples are given for Hellenistic and Mesoamerican jewellery items.

  3. Surface plasmon-driven water reduction: gold nanoparticle size matters.

    PubMed

    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 David

    2014-07-16

    Water reduction under two different visible-light ranges (λ > 400 nm and λ > 435 nm) was investigated in gold-loaded titanium dioxide (Au-TiO2) heterostructures with different sizes of Au nanoparticles (NPs). Our study clearly demonstrates the essential role played by Au NP size in plasmon-driven H2O reduction and reveals two distinct mechanisms to clarify visible-light photocatalytic activity under different excitation conditions. The size of the Au NP governs the efficiency of plasmon-mediated electron transfer and plays a critical role in determining the reduction potentials of the electrons transferred to the TiO2 conduction band. Our discovery provides a facile method of manipulating photocatalytic activity simply by varying the Au NP size and is expected to greatly facilitate the design of suitable plasmonic photocatalysts for solar-to-fuel energy conversion.

  4. Mussel-inspired block copolymer lithography for low surface energy materials of teflon, graphene, and gold.

    PubMed

    Kim, Bong Hoon; Lee, Duck Hyun; Kim, Ju Young; Shin, Dong Ok; Jeong, Hu Young; Hong, Seonki; Yun, Je Moon; Koo, Chong Min; Lee, Haeshin; Kim, Sang Ouk

    2011-12-15

    Mussel-inspired interfacial engineering is synergistically integrated with block copolymer (BCP) lithography for the surface nanopatterning of low surface energy substrate materials, including, Teflon, graphene, and gold. The image shows the Teflon nanowires and their excellent superhydrophobicity.

  5. Mixed DNA/Oligo(ethylene glycol) Functionalized Gold Surface Improve DNA Hybridization in Complex Media

    SciTech Connect

    Lee,C.; Gamble, L.; Grainger, D.; Castner, D.

    2006-01-01

    Reliable, direct 'sample-to-answer' capture of nucleic acid targets from complex media would greatly improve existing capabilities of DNA microarrays and biosensors. This goal has proven elusive for many current nucleic acid detection technologies attempting to produce assay results directly from complex real-world samples, including food, tissue, and environmental materials. In this study, we have investigated mixed self-assembled thiolated single-strand DNA (ssDNA) monolayers containing a short thiolated oligo(ethylene glycol) (OEG) surface diluent on gold surfaces to improve the specific capture of DNA targets from complex media. Both surface composition and orientation of these mixed DNA monolayers were characterized with x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS). XPS results from sequentially adsorbed ssDNA/OEG monolayers on gold indicate that thiolated OEG diluent molecules first incorporate into the thiolated ssDNA monolayer and, upon longer OEG exposures, competitively displace adsorbed ssDNA molecules from the gold surface. NEXAFS polarization dependence results (followed by monitoring the N 1s{yields}{pi}* transition) indicate that adsorbed thiolated ssDNA nucleotide base-ring structures in the mixed ssDNA monolayers are oriented more parallel to the gold surface compared to DNA bases in pure ssDNA monolayers. This supports ssDNA oligomer reorientation towards a more upright position upon OEG mixed adlayer incorporation. DNA target hybridization on mixed ssDNA probe/OEG monolayers was monitored by surface plasmon resonance (SPR). Improvements in specific target capture for these ssDNA probe surfaces due to incorporation of the OEG diluent were demonstrated using two model biosensing assays, DNA target capture from complete bovine serum and from salmon genomic DNA mixtures. SPR results demonstrate that OEG incorporation into the ssDNA adlayer improves surface resistance to both nonspecific DNA and protein

  6. Pharmacological Investigation of Fluoro-Gold Entry into Spinal Neurons

    PubMed Central

    Falgairolle, Melanie; O’Donovan, Michael J.

    2015-01-01

    The fluorescent tracer Fluoro-Gold has been widely used to label neurons retrogradely. Here we show that Fluoro-Gold can also enter neurons through AMPA receptor endocytosis. We found that a 30 minute application of Fluoro-Gold to the isolated spinal cord labeled neurons under control conditions and in the presence of glutamatergic agonists including NMDA and AMPA. The labeling was abolished or greatly reduced by glutamatergic antagonists and the endocytic inhibitors Dynasore and dynamin inhibitory peptide. Whole cell recordings from spinal neurons exposed to extracellular AMPA revealed large inward currents that spontaneously decayed in the presence of the agonist but were maintained when a dynamin inhibitory peptide was included in the electrode. These findings suggest that Fluoro-Gold enters spinal neurons through AMPA-mediated receptor internalization. Drugs used to induce locomotor-like activity in the spinal cord also increased and decreased Fluoro-Gold labeling in a drug and lamina specific manner, indicating that AMPAR endocytosis is altered in the presence of the locomotor cocktail. Our findings suggest that endocytosis of Fluoro-Gold could potentially complicate the interpretation of experiments in which the tracer is used to label neurons retrogradely. Moreover, they also demonstrate that many drugs, including the locomotor cocktail, can modulate the number and/or the composition of AMPA receptors on spinal neurons and thereby affect network excitability. PMID:26102354

  7. Pharmacological Investigation of Fluoro-Gold Entry into Spinal Neurons.

    PubMed

    Falgairolle, Melanie; O'Donovan, Michael J

    2015-01-01

    The fluorescent tracer Fluoro-Gold has been widely used to label neurons retrogradely. Here we show that Fluoro-Gold can also enter neurons through AMPA receptor endocytosis. We found that a 30 minute application of Fluoro-Gold to the isolated spinal cord labeled neurons under control conditions and in the presence of glutamatergic agonists including NMDA and AMPA. The labeling was abolished or greatly reduced by glutamatergic antagonists and the endocytic inhibitors Dynasore and dynamin inhibitory peptide. Whole cell recordings from spinal neurons exposed to extracellular AMPA revealed large inward currents that spontaneously decayed in the presence of the agonist but were maintained when a dynamin inhibitory peptide was included in the electrode. These findings suggest that Fluoro-Gold enters spinal neurons through AMPA-mediated receptor internalization. Drugs used to induce locomotor-like activity in the spinal cord also increased and decreased Fluoro-Gold labeling in a drug and lamina specific manner, indicating that AMPAR endocytosis is altered in the presence of the locomotor cocktail. Our findings suggest that endocytosis of Fluoro-Gold could potentially complicate the interpretation of experiments in which the tracer is used to label neurons retrogradely. Moreover, they also demonstrate that many drugs, including the locomotor cocktail, can modulate the number and/or the composition of AMPA receptors on spinal neurons and thereby affect network excitability.

  8. [Preparation, characterization and surface-enhanced Raman properties of agarose gel/gold nanoparticles hybrid].

    PubMed

    Ma, Xiao-yuan; Liu, Ying; Wang, Zhou-ping

    2014-08-01

    Agarose gel/gold nanoparticles hybrid was prepared by adding gold nanoparticles to preformed agarose gel. Naniocomposite structures and properties were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UV-Vis-NIR absorption spectroscopy. Experimental data indicated a uniform distribution of gold nanoparticles adsorbed on agarose gel network And the excellent optical absorption properties were shown. Based on the swelling-contraction characteristics of agarose gel and the adjustable localized surface plasmon resonance (LSPR) of the gold nanoparticles, the nano-composites were used as surface enhanced Raman scattering (SERS) substrate to detect the Raman signal molecules Nile blue A. Results revealed that the porous structure of the agarose gel provided a good carrier for the enrichment of the gold nanoparticles. The gold nanoparticles dynamic hot-spot effect arising from the agarose gel contraction loss of water in the air greatly enhanced the Raman signal.

  9. Rough SERS substrate based on gold coated porous silicon layer prepared on the silicon backside surface

    NASA Astrophysics Data System (ADS)

    Dridi, H.; Haji, L.; Moadhen, A.

    2017-04-01

    We report in this paper a novel method to elaborate rough Surface Enhanced Raman Scattering (SERS) substrate. A single layer of porous silicon was formed on the silicon backside surface. Morphological characteristics of the porous silicon layer before and after gold deposition were influenced by the rough character (gold size). The reflectance measurements showed a dependence of the gold nano-grains size on the surface nature, through the Localized Surface Plasmon (LSP) band properties. SERS signal of Rhodamine 6G used as a model analyte, adsorbed on the rough porous silicon layer revealed a marked enhancement of its vibrational modes intensities.

  10. Fine-Tuning the Antimicrobial Profile of Biocompatible Gold Nanoparticles by Sequential Surface Functionalization Using Polyoxometalates and Lysine

    PubMed Central

    Daima, Hemant K.; Selvakannan, P. R.; Shukla, Ravi; Bhargava, Suresh K.; Bansal, Vipul

    2013-01-01

    Antimicrobial action of nanomaterials is typically assigned to the nanomaterial composition, size and/or shape, whereas influence of complex corona stabilizing the nanoparticle surface is often neglected. We demonstrate sequential surface functionalization of tyrosine-reduced gold nanoparticles (AuNPsTyr) with polyoxometalates (POMs) and lysine to explore controlled chemical functionality-driven antimicrobial activity. Our investigations reveal that highly biocompatible gold nanoparticles can be tuned to be a strong antibacterial agent by fine-tuning their surface properties in a controllable manner. The observation from the antimicrobial studies on a gram negative bacterium Escherichia coli were further validated by investigating the anticancer properties of these step-wise surface-controlled materials against A549 human lung carcinoma cells, which showed a similar toxicity pattern. These studies highlight that the nanomaterial toxicity and biological applicability are strongly governed by their surface corona. PMID:24147146

  11. 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

  12. Thiol adsorption at gold surfaces: self-assembly, chiral recognition, and enantioselective adsorption at chiral surfaces.

    NASA Astrophysics Data System (ADS)

    Hammer, Bjork

    2003-03-01

    Density functional theory calculations are presented for the adsorption of thiol containing molecules on to Au(111), Au(110), and Au(17 11 9). The thiol group becomes dehydrogenated during the adsorption process and the resulting thiolate group shows a strong preference for the Au-Au bridging adsorption site.[1] For methylthiolate adsorption, a restructuring of the Au(111) surface in to a honeycomb pattern with every 3rd Au atom missing is found to lead an overall strengthening of the thiolate-gold bonding.[2] Since the surface restructuring must happen through-out the system, it represents a net attractive interaction between the adsorbates and it is speculated to have implications for the self-assembly of alkanethiols found at close packed gold surfaces. Adsorption studies of the naturally occuring amino acid, cysteine, at Au(110) also reveal enhanced thiolate-gold bonding at restructured Au sites.[3] The cysteine molecules are found to interact pairwise forming dimers that are hydrogen bonded through the cysteine carboxyl groups. The gold surface restructuring required to hold this complex involves the creation of a four Au atom wide vacancy in the outermost close packed row of the Au(110) surface. The binding of the the cysteine dimer to this vacancy site causes chiral recognition -- only cysteine dimers formed between like cysteine enantiomers are able to bind to the surface. For cysteine adsorption over the chiral (kinked) Au(17 11 9) surface no enantiospecific adsorption is found since the molecule only binds through the thiolate and amino groups.[4] Modifying the adsorbate by substituting the noninteracting carboxyl group with a dimethylphosphino group provides a third strong adsorbate-surface bond thereby enabling the discrimination during adsorption of two molecular enantiomers by one particular chiral Au surface. [1] J. Gottschalck and B. Hammer, J. Chem. Phys. 116, 784 (2002). [2] L.M. Molina and B. Hammer, Chem. Phys. Lett. 360, 264 (2002). [3] A

  13. 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

  14. Surface functionalization by gold nanoparticles and its prospects for application in conductometric metal oxide gas sensors

    NASA Astrophysics Data System (ADS)

    Korotcenkov, G.; Brinzari, V.; Cho, B. K.

    2017-03-01

    Approaches to surface functionalizing by gold nanoparticles of metal oxides aimed for gas sensors applications are discussed in this paper. It is demonstrated that surface modification by gold nanoparticles is accompanied by improvement of sensor performance. However, analysis of obtained results has shown that the achievement of strong improvement of gas sensor parameters is not a trivial task. For its reduction, it is necessary to ensure several specific conditions related to the size and density of gold clusters on the surface of metal oxide crystallites, the state of gold in the cluster, and to the properties of the metal oxide support used. It is also demonstrated that additional studies are required before conductometric gas sensors modified by gold nanoclusters will appear in gas-sensor market.

  15. 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.

  16. Dye gain gold NW array of surface plasmon polariton waveguide

    NASA Astrophysics Data System (ADS)

    Zhu, Jun; Xu, Zhengjie; Xu, Wenju; Fu, Deli; Wei, Duqu

    Plasmon lasers can support ultrasmall mode confinement and ultrafast dynamics with device feature sizes below the diffraction limit. At present in the single visible light frequency, the optical gain method of constraint SPP on metal nanowires structure reported less. We design the gold nanowire array structure, consisting of PMMA and R6G dye molecules as gain, by 488 nm pump in the middle of the nanowires position for wide range of light, use symmetry broken overcome that momentum does not match the photonic and SPP energy conversion. Theoretical analysis shows that dyes provide coherent optical feedback, resulting in nanowires face will observe laser properties of surface plasmons. Feature analysis: the incident light and pump joint strength is greater than the sum of strength which is the incident light, pump respectively. Under the effect of dye molecules gain effective, length of SPP transmission can increase 1 μm. The results achieved in a single optical frequency of stimulated radiation, application of dye optical gain can achieve continuous gain effect. This is for the future development of plasma amplifier and the wavelength laser.

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

    PubMed Central

    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

  18. Characterization of silver ions adsorbed on gold nanorods: surface analysis by using surface-assisted laser desorption/ionization time-of-flight mass spectrometry.

    PubMed

    Niidome, Yasuro; Nakamura, Yuki; Honda, Kanako; Akiyama, Yasuyuki; Nishioka, Koji; Kawasaki, Hideya; Nakashima, Naotoshi

    2009-04-07

    Surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-MS) indicated AgBr2-, which adsorbed on gold nanorod surfaces, was a key material to control the anisotropic growth of gold nanorods.

  19. 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

  20. DNA-Origami-Driven Lithography for Patterning on Gold Surfaces with Sub-10 nm Resolution.

    PubMed

    Gállego, Isaac; Manning, Brendan; Prades, Joan Daniel; Mir, Mònica; Samitier, Josep; Eritja, Ramon

    2017-01-06

    Sub-10 nm lithography of DNA patterns is achieved using the DNA-origami stamping method. This new strategy utilizes DNA origami to bind a preprogrammed DNA ink pattern composed of thiol-modified oligonucleotides on gold surfaces. Upon denaturation of the DNA origami, the DNA ink pattern is exposed. The pattern can then be developed by hybridization with complementary strands carrying gold nanoparticles.

  1. Formation of self-assembled monolayer of curcuminoid molecules on gold surfaces

    NASA Astrophysics Data System (ADS)

    Berlanga, Isadora; Etcheverry-Berríos, Álvaro; Mella, Andy; Jullian, Domingo; Gómez, Victoria Alejandra; Aliaga-Alcalde, Núria; Fuenzalida, Victor; Flores, Marcos; Soler, Monica

    2017-01-01

    We investigated the formation of self-assembled monolayers of two thiophene curcuminoid molecules, 2-thphCCM (1) and 3-thphCCM (2), on polycrystalline gold substrates prepared by immersion of the surfaces in a solution of the molecules during 24 h. The functionalized surfaces were studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Despite the fact that both molecules have the same composition and almost the same structure, these molecules exhibit different behavior on the gold surface, which can be explained by the different positions of the sulfur atoms in the terminal aromatic rings. In the case of molecule 1, the complete formation of a SAM can be observed after 24 h of immersion. In the case of molecule 2, the transition from flat-lying to upright configuration on the surface is still in process after 24 h of immersion. This is attributed to the fact that molecule 2 have the sulfur atoms more exposed than molecule 1.

  2. Coadsorption of gold with chlorine on CeO2 (111) surfaces: A first principles study

    NASA Astrophysics Data System (ADS)

    Lu, Zhan-Sheng; He, Bing-Ling; Ma, Dong-Wei; Yang, Zong-Xian

    2015-02-01

    To investigate the effects of chlorine on the Au/ceria catalysts, the adsorption of gold or chlorine and their coadsorpiton on the stoichiometric and partially reduced CeO2 (111) surfaces are studied from the first principles. It is found that the adsorption of Au is significantly enhanced by the chlorine preadsorption on the stoichiometric CeO2 (111) surface; while on the partially reduced CeO2 (111) surface, the preadsorbed chlorine inhabits the oxygen vacancy (which is the preferred adsorption site for gold), leading to a CeOCl phase and the dramatical weakening of the Au adsorption. Therefore, chlorine on the CeO2 (111) surface can affect the Au adsorption thus the activity of the Au/CeO2 catalyst. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174070, 51401078, and 11147006), the China Postdoctoral Science Foundation (Grant No. 2012M521399), the Postdoctoral Research Sponsorship in Henan Province, China (Grant No. 2011038), and the Foundation for the Key Young Teachers of Henan Normal University and Start-up Foundation for Doctors of Henan Normal University, China.

  3. Systematic Approach to the Development of Microfabricated Biosensors: Relationship between Gold Surface Pretreatment and Thiolated Molecule Binding.

    PubMed

    Makaraviciute, Asta; Xu, Xingxing; Nyholm, Leif; Zhang, Zhen

    2017-08-09

    Despite the increasing popularity of microfabricated biosensors due to advances in technologic and surface functionalization strategies, their successful implementation is partially inhibited by the lack of consistency in their analytical characteristics. One of the main causes for the discrepancies is the absence of a systematic and comprehensive approach to surface functionalization. In this article microfabricated gold electrodes aimed at biosensor development have been systematically characterized in terms of surface pretreatment, thiolated molecule binding, and reproducibility by means of X-ray photoelectron scattering (XPS) and cyclic voltammetry (CV). It has been shown that after SU-8 photolithography gold surfaces were markedly contaminated, which decreased the effective surface area and surface coverage of a model molecule mercaptohexanol (MCH). Three surface pretreatment methods compatible with microfabricated devices were compared. The investigated methods were (i) cyclic voltammetry in dilute H2SO4, (ii) gentle basic piranha followed by linear sweep voltammetry in dilute KOH, and (iii) oxygen plasma treatment followed by incubation in ethanol. It was shown that all three methods significantly decreased the contamination and increased MCH surface coverage. Most importantly, it was also revealed that surface pretreatments may induce structural changes to the gold surfaces. Accordingly, these alterations influence the characteristics of MCH functionalization.

  4. 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.

  5. 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.

  6. [Dithiobis-succinimidyl propionate on gold island films: surface-enhanced infrared absorption spectroscopy study].

    PubMed

    Guo, Hao; Ding, Li; Zhang, Tian-Jie; Mao, Yan-Li

    2013-05-01

    Dithiobis-succinimidyl propionate (DTSP), an important homobifunctional crosslinker, has been widely used for the covalent immobilization of proteins onto solid supports by amine coupling. In the present study, adsorption of DTSP on vacuum-deposited gold island films was analyzed by means of surface-enhanced infrared absorption spectroscopy (SEIRAS). For the sake of a reliable assignment of the vibrational spectra, IR intensity of the adsorption model of TSP on one gold surface was calculated using density functional theory (DFT) at the Beck' s three-parameter Lee-Yang-Parr (B3LYP) level with the LANL2DZ basis set. SEIRAS and multiple-angle-of-incidence polarization infrared reflection-absorption spectroscopy indicated that TSP is arranged orderly in a tilted fashion with a dihedral angle of 65 degrees between the plane of succinimidyl ring and the gold surface. The binding kinetics revealed that that the time constant of self-assembly of the TSP layer is 220 sec. Furthermore, the coupling process of amino-nitrilotriacetic acid (ANTA) with surface-bound TSP monolayer was monitored in situ by SEIRAS. Three negative bands observed at 1 807, 1 776, and 1 728 cm(-1) respectively provided direct evidence for the reaction of the succinimidyl ester. The appearance of one intense band at 1 566 cm(-1) gave a clear support for the presence of the cross-link between ANTA and TSP. We hope that the results in current investigation will contribute to the better understanding of properties of DTSP and related reactions at the molecular level.

  7. First-principles investigation of Ag-doped gold nanoclusters.

    PubMed

    Zhang, Xiao-Dong; Guo, Mei-Li; Wu, Di; Liu, Pei-Xun; Sun, Yuan-Ming; Zhang, Liang-An; She, Yi; Liu, Qing-Fen; Fan, Fei-Yue

    2011-01-01

    Gold nanoclusters have the tunable optical absorption property, and are promising for cancer cell imaging, photothermal therapy and radiotherapy. First-principle is a very powerful tool for design of novel materials. In the present work, structural properties, band gap engineering and tunable optical properties of Ag-doped gold clusters have been calculated using density functional theory. The electronic structure of a stable Au(20) cluster can be modulated by incorporating Ag, and the HOMO-LUMO gap of Au(20-) (n)Ag(n) clusters is modulated due to the incorporation of Ag electronic states in the HOMO and LUMO. Furthermore, the results of the imaginary part of the dielectric function indicate that the optical transition of gold clusters is concentration-dependent and the optical transition between HOMO and LUMO shifts to the low energy range as the Ag atom increases. These calculated results are helpful for the design of gold cluster-based biomaterials, and will be of interest in the fields of radiation medicine, biophysics and nanoscience.

  8. 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.

  9. Gold nanoisland arrays by repeated deposition and post-deposition annealing for surface-enhanced Raman spectroscopy.

    PubMed

    Sun, Xin; Li, Hao

    2013-09-06

    Gold nanoisland arrays with well controlled growth were achieved by repeated sputtering deposition and post-deposition annealing processes. When each deposition was set at 5 nm (nominal thickness based on gold mass), the single deposition and annealing process (single process) yielded gold nanoisland arrays with an average diameter of ~16 nm based on top view scanning electron microscopy (SEM). When the deposition and annealing process was repeated two more times (triple process), top view SEM showed the nanoisland arrays grew to ~38 nm in average diameter. The surface-enhanced Raman spectroscopy (SERS) measurement indicated that triple processed nanoisland arrays led to the highest SERS enhancement, suggesting the necessity of pursuing nanoislands with larger sizes. The gold nanoisland arrays after the triple process were further sputtered with a final layer of gold thin film at different nominal thicknesses. An optimal nominal thickness for SERS was determined experimentally at ~40 nm, as a result of the competition between the positive and negative effects of the final gold deposition. Last, the uniformity of the optimized SERS substrate was investigated on a 5 cm x 5 cm platform. SERS measurements demonstrated a relative standard deviation of ~7% in terms of spectral variation over the entire substrate, rendering the process in the present study a promising fabrication approach for large-scale production of SERS substrates.

  10. Thermodynamic and kinetic analysis of the interaction between hepatitis B surface antibody and antigen on a gold electrode modified with cysteamine and colloidal gold via electrochemistry.

    PubMed

    He, Yan Bin; Luo, Hong Qun; Li, Nian Bing

    2007-06-15

    Hepatitis B surface antibody (HBsAb) was immobilized to the surface of a gold electrode modified with cysteamine and colloidal gold as matrices to detect hepatitis B surface antigen (HBsAg). Differential pulse voltammetry (DPV) method was used for the investigation of the specific interaction between the immobilized HBsAb and HBsAg in solution, which was followed as a change of peak current in DPV with time. With the modified gold electrode, the differences in affinity of HBsAb with HBsAg at the temperatures of 37 and 40 degrees C were easily distinguished and the kinetic rate constants (k(ass) and k(diss)) and kinetic affinity constant K were determined from the curves of current versus time. In addition, the thermodynamic constants, DeltaG, DeltaH and DeltaS, of the interaction at 37 degrees C were calculated, which were -56.65, -64.54 and -25.45 kJ mol(-1), respectively.

  11. Ultrasmooth gold surfaces prepared by chemical mechanical polishing for applications in nanoscience.

    PubMed

    Miller, Michael S; Ferrato, Michael-Anthony; Niec, Adrian; Biesinger, Mark C; Carmichael, Tricia Breen

    2014-12-02

    For over 20 years, template stripping has been the best method for preparing ultrasmooth metal surfaces for studies of nanostructures. However, the organic adhesives used in the template stripping method are incompatible with many solvents, limiting the conditions that may subsequently be used to prepare samples; in addition, the film areas that can be reliably prepared are typically limited to ∼1 cm(2). In this article, we present chemical-mechanical polishing (CMP) as an adhesive-free, scalable method of preparing ultrasmooth gold surfaces. In this process, a gold film is first deposited by e-beam evaporation onto a 76-mm-diameter silicon wafer. The CMP process removes ∼4 nm of gold from the tops of the grains comprising the gold film to produce an ultrasmooth gold surface supported on the silicon wafer. We measured root-mean-square (RMS) roughness values using atomic force microscopy of 12 randomly sampled 1 μm × 1 μm areas on the surface of the wafer and repeated the process on 5 different CMP wafers. The average RMS roughness was 3.8 ± 0.5 Å, which is comparable to measured values for template-stripped gold (3.7 ± 0.5 Å). We also compared the use of CMP and template-stripped gold as bottom electrical contacts in molecular electronic junctions formed from n-alkanethiolate self-assembled monolayers as a sensitive test bed to detect differences in the topography of the gold surfaces. We demonstrate that these substrates produce statistically indistinguishable values for the tunneling decay coefficient β, which is highly sensitive to the gold surface topography.

  12. Gold/Silicon nanowire arrays modified by Gold nanosphere as the surface-enhanced Raman spectroscopy substrate

    NASA Astrophysics Data System (ADS)

    Zhou, Long; Li, Mingyu; Tang, Longhua; He, Jian-Jun

    2016-01-01

    Fabrication of gold coated silicon nanowires (AuSiNW) substrate is introduced in detail and A hybrid substrate is designed for surface-enhanced Raman spectroscopy (SERS). The SERS behaviors are discussed and compared by the detection of 4, 4’-Bipyridine. Gold nanoparicles is modified on the surface of AuSiNW to form the “hot gap”. Molecules captured in these “hot gap” can generate huge Raman signal. Double-fold enhancement of SERS signal has been achieved comparing with AuSiNW. The as-fabricated hybrid substrate exhibit high SERS sensitivity, long-term stability, and consistent reproducibility, highly potential for realizing a rapid, cost-effective, and label-free SERS-based biosensor.

  13. Raman spectroscopy and quantum-mechanical analysis of tautomeric forms in cytosine and 5-methylcytosine on gold surfaces

    NASA Astrophysics Data System (ADS)

    Nguyen, Dinh Bao; Nguyen, Thanh Danh; Kim, Sangsoo; Joo, Sang-Woo

    2017-03-01

    Spectral differences between cytosine (Cyt) and 5-methylcytosine (5MC) were investigated by means of Raman spectroscopy with a combination of density functional theory (DFT) calculations. Surface-enhanced Raman scattering (SERS) revealed discriminating peaks of 5MC from those of Cyt upon adsorption on gold nanoparticles (AuNPs). Among the notable features, the multiple bands between 850 and 700 cm- 1 for the ring-breathing modes of 5MC and Cyt could be correlated well with the simulated spectra based on the DFT calculations of the adsorbates on the gold cluster atoms. The relative energetic stabilities of the enol/keto and the amino/imino tautomeric forms of Cyt and 5MC have been estimated using DFT calculations, before and after binding six atom gold clusters. Among the six tautomeric forms, the 7H keto amino and the 4H imino trans forms are expected to be predominant in binding gold atoms, whereas the enol trans/cis conformers would coexist in the free gas phase. Our approach may provide useful theoretical guidelines for identifying 5MC from Cyt by analyzing Raman spectra on gold surfaces on the basis of quantum-mechanical calculations.

  14. 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.

  15. 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.

  16. Gold surface supported spherical liposome-gold nano-particle nano-composite for label free DNA sensing.

    PubMed

    Bhuvana, M; Narayanan, J Shankara; Dharuman, V; Teng, W; Hahn, J H; Jayakumar, K

    2013-03-15

    Immobilization of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) liposome-gold nano-particle (DOPE-AuNP) nano-composite covalently on 3-mercaptopropionic acid (MPA) on gold surface is demonstrated for the first time for electrochemical label free DNA sensing. Spherical nature of the DOPE on the MPA monolayer is confirmed by the appearance of sigmoidal voltammetric profile, characteristic behavior of linear diffusion, for the MPA-DOPE in presence of [Fe(CN)(6)](3-/4-) and [Ru(NH(3))(6)](3+) redox probes. The DOPE liposome vesicle fusion is prevented by electroless deposition of AuNP on the hydrophilic amine head groups of the DOPE. Immobilization of single stranded DNA (ssDNA) is made via simple gold-thiol linkage for DNA hybridization sensing in the presence of [Fe(CN)(6)](3-/4-). The sensor discriminates the hybridized (complementary target hybridized), un-hybridized (non-complementary target hybridized) and single base mismatch target hybridized surfaces sensitively and selectively without signal amplification. The lowest target DNA concentration detected is 0.1×10(-12)M. Cyclic voltammetry (CV), electrochemical impedance (EIS), differential pulse voltammetry (DPV) and quartz crystal microbalance (QCM) techniques are used for DNA sensing on DOPE-AuNP nano-composite. Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS) and Ultraviolet-Visible (UV) spectroscopic techniques are used to understand the interactions between the DOPE, AuNP and ssDNA. The results indicate the presence of an intact and well defined spherical DOPE-AuNP nano-composite on the gold surface. The method could be applied for fabrication of the surface based liposome-AuNP-DNA composite for cell transfection studies at reduced reagents and costs.

  17. Investigating the use of in situ liquid cell scanning transmission electron microscopy to explore DNA-mediated gold nanoparticle growth

    NASA Astrophysics Data System (ADS)

    Nguy, Amanda

    Engineering nanoparticles with desired shape-dependent properties is the key to many applications in nanotechnology. Although many synthetic procedures exist to produce anisotropic gold nanoparticles, the dynamics of growth are typically unknown or hypothetical. In the case of seed-mediated growth in the presence of DNA into anisotropic nanoparticles, it is not known exactly how DNA directs growth into specific morphologies. A series of preliminary experiments were carried out to contribute to the investigation of the possible mechanism of DNA-mediated growth of gold nanoprisms into gold nanostars using liquid cell scanning transmission electron microscopy (STEM). Imaging in the liquid phase was achieved through the use of a liquid cell platform and liquid cell holder that allow the sample to be contained within a “chip sandwich” between two electron transparent windows. Ex situ growth experiments were performed using Au-T30 NPrisms (30-base thymine oligonucleotide-coated gold nanoprisms) that are expected to grow into gold nanostars. Growth to form these nanostars were imaged using TEM (transmission electron microscopy) and liquid cell STEM (scanning transmission electron microscopy). An attempt to perform in situ growth experiments with the same Au-T30 nanoprisms revealed challenges in obtaining desired morphology results due to the environmental differences within the liquid cell compared to the ex situ environment. Different parameters in the experimental method were explored including fluid line set up, simultaneous and alternating reagent addition, and the effect of different liquid cell volumes to ensure adequate flow of reagents into the liquid cell. Lastly, the binding affinities were compared for T30 and A30 DNA incubated with gold nanoparticles using zeta potential measurements, absorption spectroscopy, and isothermal titration calorimetry (ITC). It was previously reported thymine bases have a lower binding affinity to gold surfaces than

  18. Surface properties of plasma-functionalized graphite-encapsulated gold nanoparticles prepared by a direct current arc discharge method

    NASA Astrophysics Data System (ADS)

    Yang, Enbo; Chou, Han; Tsumura, Shun; Nagatsu, Masaaki

    2016-05-01

    The graphite-encapsulated gold nanoparticles (Au@C NPs) fabricated by a direct current arc discharge method were surface-functionalized by an inductively-coupled radio frequency ammonia plasma with a particle explosion technique for enhancing surface modification efficiency. To investigate the structural and surface properties of Au@C NPs, characterizations using x-ray diffraction, high resolution transmission electron microscopy and x-ray photoelectron spectroscopy have been conducted on the untreated and plasma treated Au@C NPs. Based on the experimental results, we give insight into the possible formation of Au ions in the interface between the graphite layers and gold core particles of the Au@C NPs. Finally, the role of the plasma treatment on the surface functionalization of Au@C NPs with amino groups is discussed.

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

    SciTech Connect

    Harnisch, Jennifer Anne

    2001-01-01

    The properties of both carbon and gold substrates are easily affected by the judicious choice of a surface modification protocol. Several such processes for altering surface composition have been published in literature. The research presented in this thesis primarily focuses on the development of on-column methods to modify carbon stationary phases used in electrochemically modulated liquid chromatography (EMLC). To this end, both porous graphitic carbon (PGC) and glassy carbon (GC) particles have been modified on-column by the electroreduction of arenediazonium salts and the oxidation of arylacetate anions (the Kolbe reaction). Once modified, the carbon stationary phases show enhanced chromatographic 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.

  20. An Electrochemical and Raman Spectroelectrochemical Investigation of Underpotentially Deposited Silver on a Gold Substrate.

    DTIC Science & Technology

    1986-07-30

    Raman Spectroelectrochemical Investigation of Underpotentially Deposited Silver on a Gold Substrate By Stanley Pons. J. Li, J. Liang DTIC S ELECTE APR 14...ACCCSSIONd 14U. 3. i4CCipIa.ti rs CATALOG. PiumnRi - 4. ITL (sa~utfie) . TYPE Of REPORT a PCI3ioo covEuiv Investigation of Underpotentially Deposited ...spectroelectrochemical data indicate that underpotentially * deposited silver adatoms on gold substrates are photolyzed to form silver meta clusters. *DD

  1. 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.

  2. Adsorption and Exchange Kinetics of Hydrophilic and Hydrophobic Phosphorus Ligands on Gold Surface

    NASA Astrophysics Data System (ADS)

    Zhuge, X. Q.; Bian, Z. C.; Luo, Z. H.; Mu, Y. Y.; Luo, K.

    2017-02-01

    The adsorption kinetics process of hydrophobic ligand (triphenylphosphine, PPh3) and hydrophilic ligand (tris(hydroxymethyl)phosphine oxide, THPO) on the surface of gold electrode were estimated by using electrical double layer capacitance (EDLC). Results showed that the adsorption process of both ligands included fast and slow adsorption processes, and the fast adsorption process could fit the first order kinetic equation of Langmuir adsorption isotherm. During the slow adsorption process, the surface coverage (θ) of PPh3 was higher than that of THPO due to the larger adsorption kinetic constant of PPh3 than that of THPO, which implied that PPh3 could replace THPO on the gold electrode. The exchange process of both ligands on the surface of gold electrode proved that PPh3 take the place of THPO by testing the variation of EDLC which promote the preparation of Janus gold, and the theoretic simulation explained the reason of ligands exchange from the respect of energy..

  3. Straightforward and robust synthesis of monodisperse surface-functionalized gold nanoclusters

    PubMed Central

    Varela-Aramburu, Silvia; Wirth, Richard; Lai, Chian-Hui; Orts-Gil, Guillermo

    2016-01-01

    Summary Gold nanoclusters are small (1–3 nm) nanoparticles with a high surface area that are useful for biomedical studies and drug delivery. The synthesis of small, surface-functionalized gold nanoclusters is greatly dependent on the reaction conditions. Here, we describe a straightforward, efficient and robust room temperature one-pot synthesis of 2 nm gold nanoclusters using thioglucose as a reducing and stabilizing agent, which was discovered by serendipity. The resultant monodisperse gold nanoclusters are more stable than those generated using some other common methods. The carboxylic acid contained in the stabilizing agent on the cluster surface serves as anchor for nanocluster functionalization. Alternatively, the addition of thiols serves to functionalize the nanoclusters. The resulting non-cytotoxic nanoclusters are taken up by cells and constitute a tuneable platform for biomedical applications including drug delivery. PMID:27826501

  4. 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.

  5. Gold Rush!

    ERIC Educational Resources Information Center

    Brahier, Daniel J.

    1997-01-01

    Describes a mathematical investigation of gold--how it is weighed, stored, used, and valued. For grades 3-4, children estimate the value of treasure chests filled with gold coins and explore the size and weight of gold bars. Children in grades 5-6 explore how gold is mined and used, and how the value of gold changes over time. (PVD)

  6. 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.

  7. Ultrafast Electron Dynamics in Gold in the Presence of Laser Excited Surface Plasma Waves

    SciTech Connect

    Raynaud, M.

    2010-02-02

    Surface plasmon excitation with ultrashort intense laser pulses enhances efficiently laser absorption in metals and creates local high fields and non-equilibrium hot electrons population that have attractivity for numerous applications such as the development of intense sources of high-energy particles or photons and in the fast ignitor scheme in the framework of inertial fusion. In this context, the knowledge of the dynamics of relaxation of the collective electrons behavior is of importance. Using gold grating, we have investigated electrons relaxation in the presence of laser excited surface plasmon waves using a multiple-wavelengh femtosecond pump-probe technique. The results yield evidence of longer relaxation time in the presence of the collective excitation than that of individual electronic states.

  8. Computer simulation of particle bombardment of alkanethiol chains adsorbed on gold surface

    NASA Astrophysics Data System (ADS)

    Liu, K. S. S.; Vickerman, J. C.; Garrison, B. J.

    Molecular dynamics (MD) simulations have been used to model the high energy particle bombardment process of deuteated alkanethiol chains chemisorbed on a gold surface. The model involves the use of sophisticated many-body potential energy functions to represent the chemical interactions among atoms. We have investigated the dependence of the fragmentation pattern upon two different angles of the Ar incidents, namely in the direction parallel (-35°) and orthogonal (+55°) to the tilt chain. It is found that surface thiol chains are likely to be hit for Ar at +55° so that more fragmentation occurs. In contrast, collisions with substrate atoms are more likely when Ar impacts at -35°. This leads to less fragmentation and more molecular species are sputtered. We also found that hydrocarbon fragments such as C2D5, C3D7, and C4D9 are prominent for both angles of incidence although the suggested mechanisms leading to their ejections are different.

  9. Surface modified gold nanoparticles for SERS based detection of vulnerable plaque formations (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Matthäus, Christian; Dugandžić, Vera; Weber, Karina; Cialla-May, Dana; Popp, Jürgen

    2017-02-01

    Cardiovascular diseases are the leading cause of death worldwide. Atherosclerosis is closely related to the majority of these diseases, as a process of thickening and stiffening of the arterial walls through accumulation of lipids, which is a consequence of aging and life style. Atherosclerosis affects all people in some extent, but not all arterial plaques will necessarily lead to the complications, such as thrombosis, stroke and heart attack. One of the greatest challenges in the risk assessment of atherosclerotic depositions is the detection and recognition of plaques which are unstable and prone to rupture. These vulnerable plaques usually consist of a lipid core that attracts macrophages, a type of white blood cells that are responsible for the degradation of lipids. It has been hypothesized that the amount of macrophages relates to the overall plaque stability. As phagocytes, macrophages also act as recipients for nanoscale particles or structures. Administered gold nanoparticles are usually rabidly taken up by macrophages residing within arterial walls and can therefore be indirectly detected. A very sensitive strategy for probing gold nanoparticles is by utilizing surface enhanced Raman scattering (SERS). By modifying the surface of these particles with SERS active labels it is possible to generate highly specific signals that exhibit sensitivity comparable to fluorescence. SERS labeled gold nanoparticles have been synthesized and the uptake dynamics and efficiency on macrophages in cell cultures was investigated using Raman microscopic imaging. The results clearly show that nanoparticles are taken up by macrophages and support the potential of SERS spectroscopy for the detection of vulnerable plaques. Acknowledgements: Financial support from the Carl Zeiss Foundation is highly acknowledged. The project "Jenaer Biochip Initiative 2.0" (03IPT513Y) within the framework "InnoProfile Transfer - Unternehmen Region" is supported by the Federal Ministry of

  10. Where's the silver? Imaging trace silver coverage on the surface of gold nanorods.

    PubMed

    Jackson, Stephen R; McBride, James R; Rosenthal, Sandra J; Wright, David W

    2014-04-09

    The development of the seeded growth synthesis for gold nanorods provided the first simple, convenient wet chemistry route to these nanomaterials. Over the past decade, the original silver-assisted seeded growth procedure has been the subject of further modifications that have continuously expanded access to anisotropic gold nanoparticles; however, the role of silver in formation of gold nanorods remains poorly understood. We report the first experimental evidence on the position of silver present on gold nanorods using advanced energy dispersive X-ray spectroscopy. Our results indicate the deposition of silver ions on the surface shows no preference for a specific face or axis. Furthermore, we show that the "dog bone" structures developed from gold nanorod solutions show preferential deposition of silver atoms on the ends and in the crevices.

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

    PubMed

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

    2015-09-14

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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.

  14. 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

    2015-05-07

    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.

  15. 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.

  16. Investigation of gold as a material for thermal radiation shielding

    NASA Astrophysics Data System (ADS)

    Munshi, Amit Harenkumar

    CdS/CdTe thin film solar cells technology is one of the fastest growing carbon neutral energy sources in the world today. Manufacturing of CdS/CdTe solar modules is carried out at temperature in the range of 620350°C under a vacuum of 40 millitorr using a Heated Pocket Deposition (HPD) system in the materials engineering laboratory. Since this system operates in vacuum, majority of the heat loss is due to thermal radiation. The concept here is to conserve the heat by reflecting the infrared radiation back into the deposition system thus increasing the thermal efficiency. Various metals may be used but calculations show that using a Gold thin film mirror can effectively reflect almost 97% of the incident radiation, thus conserving energy required for the manufacturing process. However, a phenomenon called thermal grooving or island formation inhibits its use. Thermal grooving occurs when the stress concentration at the grain boundaries causes grain separation. This phenomenon is observed in thin gold films that are exposed to a temperature in excess of 350°C for over 3 to 5 hours. In this study, these films are exposed to temperature upto 620350°C for cycles as long as 200 hours. The goal of this research is to explore the solutions for elimination of the phenomenon of thermal grooving and thus extract maximum life out of these thin gold films for conservation of heat. After carefully exploring literature on past research and conducting experiments it was found that within the range of the films that were tested, a 2000 A350° film with a 150 A350° of Indium underlay showed the best performance after thermal annealing and testing.

  17. Interaction of bombesin and its fragments with gold nanoparticles analyzed using surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Tąta, Agnieszka; Szkudlarek, Aleksandra; Kim, Younkyoo; Proniewicz, Edyta

    2017-02-01

    This work demonstrates the application of commercially available stable surface composed of gold nanograins with diameters ranging from 70 to 226 nm deposited onto silicon wafer for surface-enhanced Raman scattering investigations of biologically active compounds, such as bombesin (BN) and its fragments. BN is an important neurotransmitter involved in a complex signaling pathways and biological responses; for instance, hypertensive action, contractive on uterus, colon or ileum, locomotor activity, stimulation of gastric and insulin secretion as well as growth promotion of various tumor cell lines, including: lung, prostate, stomach, colon, and breast. It has also been shown that 8-14 BN C-terminal fragment partially retains the biological activity of BN. The SERS results for BN and its fragment demonstrated that (1) three amino acids from these peptides sequence; i.e., L-histidine, L-methionine, and L-tryptophan, are involved in the interaction with gold coated silicon wafer and (2) the strength of these interactions depends upon the aforementioned amino acids position in the peptide sequence.

  18. Gold Nanostars For Surface-Enhanced Raman Scattering: Synthesis, Characterization and Optimization

    PubMed Central

    Khoury, Christopher G.; Vo-Dinh, Tuan

    2008-01-01

    The controlled synthesis of high-yield gold nanostars of varying sizes, their characterization and use in surface-enhanced Raman scattering (SERS) measurements are reported for the first time. Gold nanostars ranging from 45 to 116-nm in size were synthesized in high-yield, physically modeled and optically characterized using transmission and scanning electron microscopy and UV-Visible absorption spectroscopy. The nanostar characterization involved both studying morphology evolution over time and size as a function of nucleation. The nanostars properties as substrates for SERS were investigated and compared with respect to size. As the overall star size increases, so does the core size, the number of branches and branch aspect ratio; the number of branch tips per star surface area decreases with increasing size. The stars become more inhomogeneous in shape, although their yield is high and overall size remains homogeneous. Variations in star size are also accompanied by shifts of the long plasmon band in the NIR region, which hints towards tuning capabilities that may be exploited in specific SERS applications. The measured SERS enhancement factors suggest an interesting correlation between nanostar size and SERS efficiencies, and were relatively consistent across different star samples, with the enhancement factor estimated as 5×103 averaged over the 52-nm nanostars for 633-nm excitation. PMID:23977403

  19. 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.

  20. 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.

  1. Functionalization of gold and glass surfaces with magnetic nanoparticles using biomolecular interactions.

    PubMed

    Nidumolu, Bala G; Urbina, Michelle C; Hormes, Josef; Kumar, Challa S S R; Monroe, W Todd

    2006-01-01

    Advances in nanotechnology have enabled the production and characterization of magnetic particles with nanometer-sized features that can be functionalized with biological recognition elements for numerous applications in biotechnology. In the present study, the synthesis of and interactions between self-assembled monolayers (SAMs) on gold and glass surfaces and functionalized magnetic nanoparticles have been characterized. Immobilization of 10-15 nm streptavidin-functionalized nanoparticles to biotinylated gold and glass surfaces was achieved by the strong interactions between biotin and streptavidin. Fluorescent streptavidin-functionalized nanoparticles, biotinylated surfaces, and combinations of the two were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electron and fluorescent microscopy to confirm that little or no functionalization occurred in nonbiotinylated regions of the gold and glass surfaces compared to the biotinylated sites. Together these techniques have potential use in studying the modification and behavior of functionalized nanoparticles on surfaces in biosensing and other applications.

  2. Reductive surface synthesis of gold nanoparticles on silicate glass and their biochemical sensor applicationsa

    PubMed Central

    Li, M.; Kim, D.-P.; Jeong, G.-Y.; Seo, D.-K.; Park, C.-P.

    2012-01-01

    Gold nanoparticles (Au NPs) were directly synthesized on the surface of polyvinylsilazane (PVSZ, -[(vinyl)SiH-NH2]-) without use of extra reductive additives. The reductive Si-H functional groups on the surface of cured PVSZ acted as surface bound reducing agents to form gold metal when contacted with an aqueous Au precursor (HAuCl4) solution, leading to formation of Au NPs adhered to silicate glass surface. The Au NPs-silicate platforms were preliminarily tested to detect Rhodamine B (1 μM) by surface enhanced Raman scattering. Furthermore, gold microelectrode obtained by post-chemical plating was used as an integrated amperometric detection element in the polydimethylsilane-glass hybrid microfluidic chip. PMID:24324531

  3. Reductive surface synthesis of gold nanoparticles on silicate glass and their biochemical sensor applications.

    PubMed

    Li, M; Kim, D-P; Jeong, G-Y; Seo, D-K; Park, C-P

    2012-01-01

    Gold nanoparticles (Au NPs) were directly synthesized on the surface of polyvinylsilazane (PVSZ, -[(vinyl)SiH-NH2]-) without use of extra reductive additives. The reductive Si-H functional groups on the surface of cured PVSZ acted as surface bound reducing agents to form gold metal when contacted with an aqueous Au precursor (HAuCl4) solution, leading to formation of Au NPs adhered to silicate glass surface. The Au NPs-silicate platforms were preliminarily tested to detect Rhodamine B (1 μM) by surface enhanced Raman scattering. Furthermore, gold microelectrode obtained by post-chemical plating was used as an integrated amperometric detection element in the polydimethylsilane-glass hybrid microfluidic chip.

  4. Surface chemistry of gold nanorods: origin of cell membrane damage and cytotoxicity

    NASA Astrophysics Data System (ADS)

    Wang, Liming; Jiang, Xiumei; Ji, Yinglu; Bai, Ru; Zhao, Yuliang; Wu, Xiaochun; Chen, Chunying

    2013-08-01

    We investigated how surface chemistry influences the interaction between gold nanorods (AuNRs) and cell membranes and the subsequent cytotoxicity arising from them in a serum-free cell culture system. Our results showed that the AuNRs coated with cetyl trimethylammonium bromide (CTAB) molecules can generate defects in the cell membrane and induce cell death, mainly due to the unique bilayer structure of CTAB molecules on the surface of the rods rather than their charge. Compared to CTAB-capped nanorods, positively charged polyelectrolyte-coated, i.e. poly(diallyldimethyl ammonium chloride) (PDDAC), AuNRs show improved biocompatibility towards cells. Thus, the present results indicate that the nature of surface molecules, especially their packing structures on the surface of AuNRs rather than surface charge, play a more crucial role in determining cytotoxicity. These findings about interfacial interactions could also explain the effects of internalized AuNRs on the structures or functions of organelles. This study will help understanding of the toxic nature of AuNRs and guide rational design of the surface chemistry of AuNRs for good biocompatibility in pharmaceutical therapy.

  5. Effects of changes in the interparticle separation induced by alkanethiols on the surface plasmon band and other properties of nanocrystalline gold films.

    PubMed

    Agrawal, Ved Varun; Varghese, Neenu; Kulkarni, G U; Rao, C N R

    2008-03-18

    Effects of changing the interparticle separation on the surface plasmon bands of ultrathin films of gold nanoparticles have been investigated by examining the interaction of alkanethiols of varying chain length on nanocrystalline gold films generated at the organic-aqueous interface. Adsorption of alkanethiols causes blue-shifts of the surface plasmon adsorption band, the magnitude of the shift being proportional to the chain length. The disordered nanocrystals thus created (lambdamax, 530 m) are in equilibrium with the ordered nanocrystals in the film (lambdamax, 700 m) as indicated by an isosbestic point around 600 nm. Long chain thiols disintegrate or disorder the gold films more effectively, as demonstrated by the increased population of the thiol-capped gold nanocrystals in solution. The rate of interaction of the thiols with the film decreases with the decreasing chain length. The effect of an alkanethiol on the spectrum of the gold film is specific, in that the effects with long and short chains are reversible. The changes in the plasmon band of gold due to interparticle separation can be satisfactorily modeled on the basis of the Maxwell-Garnett formalism. Spectroscopic studies, augmented by calorimetric measurements, suggest that the interaction of alkanethiols involves two steps, the first step being the exothermic gold film-thiol interaction and the second step includes the endothermic disordering process followed by further thiol capping of isolated gold particles.

  6. 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

    2015-09-07

    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.

  7. Facile synthesis of biocompatible gold nanoparticles with organosilicone-coated surface properties

    NASA Astrophysics Data System (ADS)

    Xia, Lijin; Yi, Sijia; Lenaghan, Scott C.; Zhang, Mingjun

    2012-07-01

    In this study, a simple method for one-step synthesis of gold nanoparticles has been developed using an organosilicone surfactant, Silwet L-77, as both a reducing and capping agent. Synthesis of gold nanoparticles using this method is rapid and can be conducted conveniently at ambient temperature. Further refinement of the method, through the addition of sodium hydroxide and/or silver nitrate, allowed fine control over the size of spherical nanoparticles produced. Coated on the surface with organosilicone, the as-prepared gold nanoparticles were biocompatible and stable over the pH range from 5 to 12, and have been proven effective at transportation into MC3T3 osteoblast cells. The proposed method is simple, fast, and can produce size-controlled gold nanoparticles with unique surface properties for biomedical applications.

  8. Photoacoustic investigation of gold nanoshells for bioimaging applications

    NASA Astrophysics Data System (ADS)

    Sathiyamoorthy, K.; Strohm, Eric M.; Kolios, Michael C.

    2016-03-01

    In this study, we report photoacoustic (PA) measurements of gold-covered polystyrene nanoparticles (Au nanoshells). Two types of Au nanoshells were examined: 1) polystyrene core with sparsely covered Au nanoparticles, and 2) polystyrene core which were fully covered by Au nanoparticles. The fully covered Au nanoshell exhibited a broad extinction cross section (500 nm - 850 nm), which is in the first infrared optical window where light transmission is optimal for optical based studies in tissues. The optical properties were compared to numerical simulations using Mie scattering theory. Using a photoacoustic microscope, the PA signal measured from fully covered Au nanoshells was 1.27 +/- 0.18 mV per fluence (mJ/cm2), which was 10x greater than the PA signal from sparsely covered Au nanoshells (0.12 +/- 0.14 mV). These novel Au nanoshell nanoparticles can be used for multispectral optical and PA imaging.

  9. Observation of surface plasmon resonance of gold nanoparticles in energy-related material: pentaerythritol tetranitrate

    NASA Astrophysics Data System (ADS)

    Nurmukhametov, D. R.; Zvekov, A. A.; Zverev, A. S.; Eremenko, A. N.; Russakov, D. M.; Aduev, B. P.

    2017-07-01

    The surface plasmon resonance of gold nanoparticles in a polycrystalline energy-related material - pentaerythritol tetranitrate (PETN) - has been observed for the first time. The extinction spectra of this material are recorded, and its absorption characteristics are determined by the photoacoustic method using pulsed laser irradiation. Using the data obtained, it is concluded that gold nanoparticles are promising inclusions in explosive materials when designing an optical detonator.

  10. Effect of Gold Nanorod Surface Chemistry on Cellular Response

    DTIC Science & Technology

    2011-03-15

    distribution unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Recently gold nanoparticles (Au NPs) have shown promising biological and military applications...tion after exposure to nanoparticles , but Trypan Blue exclusion assay and protein quantification did not show increased cell viability. It was...the literature showed that nanoparticles caused DNA damage to cells indirectly, without ever being directly exposed to or taken up by the cells.45 It is

  11. Surface Proton Transfer Promotes Four-Electron Oxygen Reduction on Gold Nanocrystal Surfaces in Alkaline Solution

    DOE PAGES

    Lu, Fang; Zhang, Yu; Liu, Shizhong; ...

    2017-05-11

    Four-electron oxygen reduction reaction (4e-ORR), as a key pathway in energy conversion, is preferred over the two-electron reduction pathway that falls short in dissociating dioxygen molecules. Gold (Au) surfaces exhibit high sensitivity of the ORR pathway to its atomic structures. The long-standing puzzle remains unsolved why the Au surfaces with {100} sub-facets were exceptionally capable to catalyze the 4e-ORR in alkaline solution, though limited within a narrow potential window. Herein we report the discovery of a dominant 4e-ORR over the whole potential range on {310} surface of Au nanocrystal shaped as truncated ditetragonal prism (TDP). In contrast, ORR pathways onmore » single-crystalline facets of shaped nanoparticles, including {111} on nano-octahedra and {100} on nano-cubes, are similar to their single-crystal counterparts. Combining our experimental results with density functional theory calculations, we elucidate the key role of surface proton transfers from co-adsorbed H2O molecules in activating the facet- and potential-dependent 4e ORR on Au in alkaline solutions. These results elucidate how surface atomic structures determine the reaction pathways via bond scission and formation among weakly adsorbed water and reaction intermediates. The new insight helps in developing facet-specific nanocatalysts for various reactions.« less

  12. Surface Proton Transfer Promotes Four-Electron Oxygen Reduction on Gold Nanocrystal Surfaces in Alkaline Solution.

    PubMed

    Lu, Fang; Zhang, Yu; Liu, Shizhong; Lu, Deyu; Su, Dong; Liu, Mingzhao; Zhang, Yugang; Liu, Ping; Wang, Jia X; Adzic, Radoslav R; Gang, Oleg

    2017-05-31

    Four-electron oxygen reduction reaction (4e-ORR), a key pathway in energy conversion, is preferred over the two-electron reduction pathway that falls short in dissociating dioxygen molecules. Gold surfaces exhibit high sensitivity of the ORR pathway to its atomic structures. A long-standing puzzle remains unsolved: why the Au surfaces with {100} sub-facets were exceptionally capable to catalyze the 4e-ORR in alkaline solution, though limited within a narrow potential window. Herein we report the discovery of a dominant 4e-ORR over the whole potential range on {310} surface of Au nanocrystal shaped as truncated ditetragonal prism (TDP). In contrast, ORR pathways on single-crystalline facets of shaped nanoparticles, including {111} on nano-octahedra and {100} on nanocubes, are similar to their single-crystal counterparts. Combining our experimental results with density functional theory calculations, we elucidate the key role of surface proton transfers from co-adsorbed H2O molecules in activating the facet- and potential-dependent 4e-ORR on Au in alkaline solutions. These results elucidate how surface atomic structures determine the reaction pathways via bond scission and formation among weakly adsorbed water and reaction intermediates. The new insight helps in developing facet-specific nanocatalysts for various reactions.

  13. Adsorption of DNA onto gold nanoparticles and graphene oxide: surface science and applications.

    PubMed

    Liu, Juewen

    2012-08-14

    The interaction between DNA and inorganic surfaces has attracted intense research interest, as a detailed understanding of adsorption and desorption is required for DNA microarray optimization, biosensor development, and nanoparticle functionalization. One of the most commonly studied surfaces is gold due to its unique optical and electric properties. Through various surface science tools, it was found that thiolated DNA can interact with gold not only via the thiol group but also through the DNA bases. Most of the previous work has been performed with planar gold surfaces. However, knowledge gained from planar gold may not be directly applicable to gold nanoparticles (AuNPs) for several reasons. First, DNA adsorption affinity is a function of AuNP size. Second, DNA may interact with AuNPs differently due to the high curvature. Finally, the colloidal stability of AuNPs confines salt concentration, whereas there is no such limit for planar gold. In addition to gold, graphene oxide (GO) has emerged as a new material for interfacing with DNA. GO and AuNPs share many similar properties for DNA adsorption; both have negatively charged surfaces but can still strongly adsorb DNA, and both are excellent fluorescence quenchers. Similar analytical and biomedical applications have been demonstrated with these two surfaces. The nature of the attractive force however, is different for each of these. DNA adsorption on AuNPs occurs via specific chemical interactions but adsorption on GO occurs via aromatic stacking and hydrophobic interactions. Herein, we summarize the recent developments in studying non-thiolated DNA adsorption and desorption as a function of salt, pH, temperature and DNA secondary structures. Potential future directions and applications are also discussed.

  14. Theoretical study of atomic oxygen on gold surface by Hückel theory and DFT calculations.

    PubMed

    Sun, Keju; Kohyama, Masanori; Tanaka, Shingo; Takeda, Seiji

    2012-09-27

    It is fundamental to understand the behavior of atomic oxygen on gold surfaces so as to elucidate the mechanism of nano gold catalysts for low-temperature CO oxidation reactions since the atomic oxygen on gold system is an important intermediate involved in both the processes of O(2) dissociation and CO oxidation. We performed theoretical analysis of atomic oxygen adsorption on gold by using Hückel theory. It is found that formation of linear O-Au-O structure on Au surfaces greatly stabilizes the atomic oxygen adsorption due to stronger bond energy and bond order, which is confirmed subsequently by density functional theory (DFT) calculations. The linear O-Au-O structure may explain the surprising first order kinetics behavior of O(2) desorption from gold surfaces. This view of the linear O-Au-O structure as the natural adsorption status is quite different from the conventional view, which may lead to new understanding toward the reaction mechanism of low-temperature CO oxidation reaction on nano gold catalysts.

  15. Bacterial biofilm elimination using gold nanorod localised surface plasmon resonance generated heat.

    PubMed

    Pihl, Maria; Bruzell, Ellen; Andersson, Martin

    2017-11-01

    Antimicrobial resistance is an increasing global health concern and the world is facing a major challenge to develop novel ways of replacing antibiotics. Gold nanorods exhibit localised surface plasmon resonance upon optical irradiation. During relaxation, absorbed energy is dissipated as heat, which has been utilized to kill bacteria. In this study, 10×45nm gold nanorods were attached to glass surfaces using silanisation. Then biofilms were cultured on the surfaces and studied using microscopy. On average, 71% of the early biofilm bacteria were eliminated after 5min of near infrared radiation (LED emission peak at 850nm) of the gold nanorod coated surfaces, showing the potential of this novel antibiofilm technique. Most notably, the best individual result showed 97% biofilm elimination. This study demonstrates that nanoplasmonic generated heat offers a novel way of eliminating bacterial biofilms. In future applications, this method may be used to eliminate bacterial contamination during implant surgery. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Mechanisms of Reduced Astrocyte Surface Coverage in Cortical Neuron-Glia Co-cultures on Nanoporous Gold Surfaces.

    PubMed

    Chapman, Christopher A R; Chen, Hao; Stamou, Marianna; Lein, Pamela J; Seker, Erkin

    2016-09-01

    Nanoporous gold (np-Au) is a promising multifunctional material for neural electrodes. We have previously shown that np-Au nanotopography reduces astrocyte surface coverage (linked to undesirable gliosis) while maintaining high neuronal coverage in a cortical primary neuron-glia co-culture model as long as two weeks in vitro. Here, we investigate the potential influence of secreted soluble factors from cells grown on np-Au on the cell type-specific surface coverage of cells grown on conventional tissue culture plastic and test the hypothesis that secretion of factors is responsible for inhibiting astrocyte coverage on np-Au. In order to assess whether factors secreted from cells grown on np-Au surfaces reduced surface coverage by astrocytes, we seeded fresh primary rat neuron-glia co-cultures on conventional polystyrene culture dishes, but maintained the cells in conditioned media from co-cultures grown on np-Au surfaces. After one week in vitro, a preferential reduction in astrocyte surface coverage was not observed, suggesting that soluble factors are not playing a role. In contrast, four hours after cell seeding there were a significant number of non-adhered, yet still viable, cells for the cultures on np-Au surfaces. We hypothesize that the non-adherent cells are mainly astrocytes, because: (i) there was no difference in neuronal cell coverage between np-Au and pl-Au for long culture durations and (ii) neurons are post-mitotic and not expected to increase in number upon attaching to the surface. Overall, the results suggest that the np-Au topography leads to preferential neuronal attachment shortly after cell seeding and limits astrocyte-specific np-Au surface coverage at longer culture durations.

  17. 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.

  18. CO2 laser-cleaning of dimethylsilicone contamination on the surface of gold films

    NASA Astrophysics Data System (ADS)

    Ye, Yayun; Yuan, Xiaodong; Xiang, Xia; Chen, Meng; Miao, Xinxiang; Lv, Haibing; Wang, Haijung; Wang, Chengcheng; Zheng, Wanguo

    2009-08-01

    As a non-contact cleaning method, laser cleaning can effectively remove particulate contaminations of sizes as small as 0.1 μm without damage to the optics. In this work, 10.6 μm CO2 laser was utilized to clean the dimethylsilicone oil contaminated on the surface of the gold-coated K9 glass. The dimethylsilicone oil contaminants with different degree were obtained by 10-30 minutes of vapor condensation. Single point irradiation mode was used to study the removal of the dimethylsilicone oil. The cleaning different degree of contaminations was investigated at the variable laser parameters, including laser power, laser frequency, and irradiation time. Optical microscope was used to analyze the cleaning effect. The results show that CO2 laser can effectively remove the dimethylsilicone oil. On the premise that the gold-coated K9 glasses are not damaged, the cleaning area increases with the increase of radiation time and laser power. The cleaning area doesn't change much with the variation of laser frequency when the other parameters are the same. In addition, at the same laser parameters, the cleaning area increases as contamination degree increases.

  19. Investigating the specificity of peptide adsorption on gold using molecular dynamics simulations.

    PubMed

    Verde, Ana Vila; Acres, Jacqueline M; Maranas, Janna K

    2009-08-10

    We report all-atom molecular dynamics simulations following adsorption of gold-binding and non-gold-binding peptides on gold surfaces modeled with dispersive interactions. We examine the dependence of adsorption on both identity of the amino acids and mobility of the peptides. Within the limitations of the approach, results indicate that when the peptides are solvated, adsorption requires both configurational changes and local flexibility of individual amino acids. This is achieved when peptides consist mostly of random coils or when their secondary structural motifs (helices, sheets) are short and connected by flexible hinges. In the absence of solvent, only affinity for the surface is required: mobility is not important. In combination, these results suggest the barrier to adsorption presented by displacement of water molecules requires conformational sampling enabled through mobility.

  20. Gold Induced SILICON(111) Surface Reconstructions Studied by Ultrahigh Vacuum Transmission Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Plass, Richard Anton

    Due to its growing scientific and technical importance in semiconductor metallization, the Au on Si(111) system has recently drawn the attention of many researchers. Therefore, the atomic structures of two gold induced Si(111) surface reconstructions were determined using ultrahigh vacuum transmission electron microscopy. The Si(111)-(5 x 2) Au atomic structure was determined using a combination of off-zone HREM imaging, "heavy-atom holography", and chi^2 electron diffraction refinement. It contains two rows of gold atoms between expanded surface arrangements of silicon atoms. Si(111) -(5 x 2) Au passivates the surface to oxygen attack and room temperature gold deposition onto it indicates surface diffusion is important in its disordering. Transmission electron diffraction data of the Si(111)-(surd 3 x surd3)R30 ^circAu surface support the missing top layer twisted trimer model of this surface in which gold and silicon atoms in the top two layers form rotated like-atom trimers. This gold-silicon structure is quite similar to part of the Si(111)-(5 x 2) Au structure. The degree of trimer rotation and the interatomic spacings of the Si(111)-(surd3 x surd3)R30 ^circAu structure vary significantly with the sharpness of the structure's diffraction spots. These variations and large fitted Debye Waller term values indicate substantial static disorder is present. Evidence of subsurface displacements and charge transfer was also found. The presence of gold trimers is confirmed by the local symmetry seen in high resolution micrographs, which also show surface domain morphology differences between diffuse and sharp diffraction spot regions. Based on these images, models for the Si(111)-(surd3 x surd3)R30 ^circAu domain walls are proposed. Room temperature gold deposition onto the Si(111) -(surd3timessurd3)R30 ^circAu surface shows that higher order surface diffracted beams decay more quickly with coverage than lower order beams. Direct phasing analysis of this result

  1. Numerical investigation of the enhancement factor of Raman scattering using plasmonic properties of gold nanorhomb arrays

    NASA Astrophysics Data System (ADS)

    Mehrvar, L.; Dizaji, Z. V.; Tavassoli, S. H.

    2017-03-01

    Plasmonic nanostructures with sharp tips like nanorhomb array provide strong electric field enhancement and consequently meaningful Raman signal enhancement. In this study, the near-field electromagnetic enhancement of the gold nanorhomb array formed by a new proposed approach has been investigated using the finite element method (FEM). Feasibility and ease of fabrication, which are very important in practical applications, are intended in this approach. This nanorhomb array is achieved by arranging holes tangentially together in a square lattice. In other words, nanorhombs are formed by transition from nanohole to nanoparticle array. Optimization of this structure for a surface-enhanced Raman spectroscopy (SERS) substrate is performed by sweeping through the geometric parameters. The most privileged nanorhomb array substrate with highest hot spot density and EM field enhancement is obtained by calculating the enhancement factor (EF) and normalized EF (EFN) for Raman lines of pyridine. Our simulations indicate that the localized surface plasmon resonance (LSPR) mode of such nanorhomb array leads to high electromagnetic enhancement factor (EMEF) and average surface integral of field enhancement factor (\\overlineEF), which are hundreds of times greater than the nanohole arrays. It is found that this LSPR mode is thickness-dependent besides being periodicity-dependent. Finally, accurate EF is calculated by considering local incident field enhancement in terms of the excitation process and local density of states (LDOS) enhancements on emission process and then the best structure with highest EF is obtained.

  2. Gold nanorods for surface Plasmon resonance detection of mercury (II) in flow injection analysis.

    PubMed

    Trieu, Khang; Heider, Emily C; Brooks, Scott C; Barbosa, Fernando; Campiglia, Andres D

    2014-10-01

    This article investigates the flow injection analysis of mercury (II) ions in tap water samples via surface Plasmon resonance detection. Quantitative analysis of mercury (II) is based on the chemical interaction of metallic mercury with gold nanorods immobilized on a glass substrate. A new flow cell design is presented with the ability to accommodate the detecting substrate in the sample compartment of commercial spectrometers. Two alternatives are here considered for mercury (II) detection, namely stop-flow and continuous flow injection analysis modes. The best limit of detection (2.4 ng mL(-1)) was obtained with the continuous flow injection analysis approach. The accurate determination of mercury (II) ions in samples of unknown composition is demonstrated with a fortified tap water sample.

  3. Modified gold surfaces by poly(amidoamine) dendrimers and fructose dehydrogenase for mediated fructose sensing.

    PubMed

    Damar, Kadir; Odaci Demirkol, Dilek

    2011-12-15

    An electrochemical biosensor for detection of fructose in food samples was developed by immobilization of fructose dehydrogenase (FDH) on cysteamine and poly(amidoamine) dendrimers (PAMAM)-modified gold electrode surface. Electrochemical analysis was carried out by using hexacyanoferrate (HCF) as a mediator and the response time was 35s at +300 mV vs. Ag/AgCl. Moreover, some parameters such as pH, enzyme loading and type of PAMAM (Generations 2, 3 and 4) were investigated. Then, the FDH biosensor was calibrated for fructose in the concentration range of 0.25-5.0mM. To evaluate its utility, the FDH biosensor was applied for fructose analysis in real samples. Finally, obtained data were compared with those measured with HPLC as a reference method. Copyright © 2011 Elsevier B.V. All rights reserved.

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

    PubMed

    Choudhary, Amit; Li, Guoqiang

    2014-10-06

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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. Localized surface plasmon resonances in gold nano-patches on a gallium nitride substrate.

    PubMed

    D'Antonio, Palma; Inchingolo, Alessio Vincenzo; Perna, Giuseppe; Capozzi, Vito; Stomeo, Tiziana; De Vittorio, Massimo; Magno, Giovanni; Grande, Marco; Petruzzelli, Vincenzo; D'Orazio, Antonella

    2012-11-16

    In this paper we describe the design, fabrication and characterization of gold nano-patches, deposited on gallium nitride substrate, acting as optical nanoantennas able to efficiently localize the electric field at the metal-dielectric interface. We analyse the performance of the proposed device, evaluating the transmission and the electric field localization by means of a three-dimensional finite difference time domain (FDTD) method. We detail the fabrication protocol and show the morphological characterization. We also investigate the near-field optical transmission by means of scanning near-field optical microscope measurements, which reveal the excitation of a localized surface plasmon resonance at a wavelength of 633 nm, as expected by the FDTD calculations. Such results highlight how the final device can pave the way for the realization of a single optical platform where the active material and the metal nanostructures are integrated together on the same chip.

  7. Bond strengths and patterns of failure of a zinc polycarboxylate cement on surface-treated gold alloys.

    PubMed

    Ogunyinka, A

    2000-08-01

    The study investigated the shear strengths and fracture characteristics of a zinc polycarboxylate cement on three sets of type III gold alloy bars whose surfaces were modified by alumina blasting, heat treatment and tin plating respectively. Each set comprised 20 bars with similarly treated surfaces, cemented in pairs with the polycarboxylate cement and stored in water at 37 degrees C for 48 hours. The cement bond was then stressed to failure by application of forces in shear mode and the bond strength was determined. The mean bond strength for each type of treated gold alloy surface was calculated and then compared with the others by way of statistical analysis. The failed surfaces were observed and photographed with a stereophotomicroscope for subjective evaluation of the character of the failed surfaces. The strongest bonds were formed on the alumina-blasted surfaces where 70% of the bonds failed in an adhesive-cohesive fashion. The weakest bonds were formed on the tin-plated surfaces where cement failure was entirely adhesive. Bond strengths on the heat-treated surfaces were intermediate and a cohesive failure pattern was observed on 80% of the specimens. The differences in bond strengths on the three surfaces were statistically significant.

  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. Near-infrared surface-enhanced Raman spectroscopy of chemisorbed compounds on gold colloids

    NASA Astrophysics Data System (ADS)

    Xu, Hong; Tseng, Ching-Hui; Vickers, Thomas J.; Mann, Charles K.; Schlenoff, Joseph B.

    1994-05-01

    Near-infrared surface-enhanced Raman scattering (SERS) spectra have been measured for strongly chemisorbed compounds, such as 4-mercaptopyridine and thiophenol, on gold colloids in mixed solvents of ethanol and water using a diode laser as an excitation source. From UV-vis spectroscopy, the aggregated gold colloids show a broad absorbance band through the visible to the near-infrared after adding chemisorbing compounds. The absorption maximum is located in the range 750-850 nm, permitting the use of a near-IR source (826 nm) for the first time in SERS of gold colloid systems. The estimated enhancement is on the order of 10 5. Transmission electron microscopy of aggregated gold particles revealed a cluster morphology. The aggregated mixed-solvent colloids were more stable than those prepared in water, and were useful in dissolving compounds with poor water solubility.

  10. 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.

  11. Utilizing the photothermal effect for releasing molecules from the surfaces of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Samsam Bakhtiari, Amir Bahman

    Nanomaterials, with unique physical and chemical properties, have the potential to help in the development of drug delivery systems. Some of these properties can be attributed to the nanoscale dimension of these materials. By masking, targeting, and release of a therapeutic agent, these nanomaterials can provide a delivery system that would reduce side effects. Gold nanoparticles have been studied as a candidate for the drug delivery system. These materials can be decorated with molecules that have a thermally responsive reaction (i.e., Diels-Alder). In addition, gold nanoparticles when irradiated with a right wavelength of light produce heat. Consequently, the generated heat from nanoparticles causes a retro-Diels-Alder reaction, which release a segment of molecule (i.e., payload) from gold surfaces. This controlled release mechanism is a novel method to take advantage of the properties inherent in gold nanoparticles and have the potential to be used in drug delivery system.

  12. 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-

  13. Atom and Amine Adsorption on Flat and Stepped Gold Surfaces & Structure, Stability and Spin Ordering in Manganese Sulfide Clusters

    NASA Astrophysics Data System (ADS)

    Lewoczko, April D.

    In part I, we investigate gold catalysis in the chemistry of organonitrogen compounds. We examine the adsorption of oxygen, nitrogen and sulfur atoms on the gold (111), (100) and (211) surfaces using density functional theory (DFT). Sulfur atoms bind most strongly, followed by oxygen and nitrogen atoms with stronger adsorption for greater coordination to the surface. We see a trend of stronger adsorption to undercoordinated gold, but find it is non-universal with the adsorption strength trend: (111) > (211) > (100). We consider the diffusion of oxygen, nitrogen and sulfur adatoms and find facile long-range diffusion of oxygen atoms on the (100) surface. Lastly, we compare the adsorption of methylamine on gold to that of a selection of alkylamines, methanol and methanethiol. In each case, the ontop site is preferred with stronger adsorption at low coordinated gold. At oxygen atom coverages of 0.125 -- 0.25 ML on Au (111), we find cooperative adsorption of methylamine and oxygen atoms. Energetic costs for adsorbate tilt from the surface normal and rotation about the gold-nitrogen bond are calculated. While methylamine rotation is barrierless on the (111) and (211) surfaces, it has a low energetic barrier for the 0.125 ML and 0.25 ML O atom pre-covered Au (111) surfaces. In part II, we interpret the experimental mass spectrum of small gas phase manganese sulfide clusters using DFT and elucidate the role of ionicity and spin ordering in sizes with special stability, i.e. magic clusters. We first consider nine low lying minima (MnS)6 structures and reveal antiferromagnetic (AFM) spin ordering with a ˜0.1 eV/pair AFM energy benefit and a ˜0.1 A shrinkage of average Mn-Mn distances over clusters with ferromagnetic (FM) spin ordering. We calculate energetic barriers for interconversion between the two lowest lying (MnS)6 isomers and predict an elevated cluster melting temperature due to increased configurational entropy in a pre-melted state. Second, we demonstrate the

  14. 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.

  15. Multichannel biosensing platform of surface-immobilized gold nanospheres for linear and nonlinear optical imaging.

    PubMed

    Tsuboi, Kazuma; Fukuba, Shinya; Naraoka, Ryo; Fujita, Katsuhiko; Kajikawa, Kotaro

    2007-07-10

    What we believe to be a new label-free multichannel biosensing platform is proposed. It is composed of surface-immobilized gold nanospheres (SIGNs) above a gold surface with a nanogap supported by a merocyanine self-assembled monolayer. The circular SIGN spots with a diameter of 120 microm were arrayed for multichannel biosensing on a glass slide. Two kinds of sensing methods were examined: One is a reflectivity measurement of a blue ray and the other is a second-harmonic generation measurement. It was found that the SIGN system can be used as a promising platform for multichannel biosensing in both sensing methods.

  16. Preparation, Surface Properties, and Therapeutic Applications of Gold Nanoparticles in Biomedicine.

    PubMed

    Panahi, Yunes; Mohammadhosseini, Majid; Nejati-Koshki, Kazem; Abadi, Azam Jafari Najaf; Moafi, Hadi Fallah; Akbarzadeh, Abolfazl; Farshbaf, Masoud

    2017-02-01

    Gold nanoparticles (AuNPs) due to their unique properties and manifold surface functionalities have been applied in bio-nanotechnology. The application of GNPs in recent medical and biological research is very extensive. Especially it involves applications such as detection and photothermalysis of microorganisms and cancer stem cells, biosensors; optical bio-imaging and observing of cells and these nanostructures also serve as practical platforms for therapeutic agents. In this review we studied all therapeutic applications of gold nanoparticles in biomedicine, synthesis methods, and surface properties.

  17. 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.

  18. Early diagnosis of oral cancer based on the surface plasmon resonance of gold nanoparticles

    PubMed Central

    Kah, James Chen Yong; Kho, Kiang Wei; Lee, Caroline Guat Leng; Richard, Colin James; Sheppard; Shen, Ze Xiang; Soo, Khee Chee; Olivo, Malini Carolene

    2007-01-01

    The high mortality rate in cancer such as oral squamous cell carcinoma is commonly attributed to the difficulties in detecting the disease at an early treatable stage. In this study, we exploited the ability of gold nanoparticles to undergo coupled surface plasmon resonance and set up strong electric fields when closely-spaced to improve the molecular contrast signal in reflectance-based imaging and also to enhance the Raman signal of bioanalytes in cancer. Colloidal gold nanoparticles were synthesized and conjugated to anti-epidermal growth factor receptor (EGFR) for imaging. A self-assembled surface enhanced Raman scattering (SERS)-active gold nanoparticle monolayer film was also developed as a biosensing surface using a simple drop-dry approach. We have shown that gold nanoparticles could elicit an optical contrast to discriminate between cancerous and normal cells and their conjugation with antibodies allowed them to map the expression of relevant biomarkers for molecular imaging under confocal reflectance microscopy. We have also shown that the SERS spectra of saliva from the closely-packed gold nanoparticles films was differentiable between those acquired from normal individuals and oral cancer patients, thus showing promise of a simple SERS-based saliva assay for early diagnosis of oral cancer. PMID:18203445

  19. Electroless-plated gold films for sensitive surface plasmon resonance detection of white spot syndrome virus.

    PubMed

    Lei, Yun; Chen, Hongyu; Dai, Heping; Zeng, Zhaorui; Lin, Yi; Zhou, Feimeng; Pang, Daiwen

    2008-02-28

    The paper describes the rapid and label-free detection of the white spot syndrome virus (WSSV) using a surface plasmon resonance (SPR) device based on gold films prepared by electroless plating. The plating condition for obtaining films suitable for SPR measurements was optimized. Gold nanoparticles adsorbed on glass slides were characterized by transmission electron microscopy (TEM). Detection of the WSSV was performed through the binding between WSSV in solution and the anti-WSSV single chain variable fragment (scFv antibody) preimmobilized onto the sensor surface. Morphologies of the as-prepared gold films, gold films modified with self-assembled alkanethiol monolayers, and films covered with antibody were examined using an atomic force microscope (AFM). To demonstrate the viability of the method for real sample analysis, WSSV of different concentrations present in a shrimp hemolymph matrix was determined upon optimizing the surface density of the antibody molecules. The SPR device based on the electroless-plated gold films is capable of detecting concentration of WSSV as low as 2.5 ng/mL in 2% shrimp hemolymph, which is one to two orders of magnitude lower than the level measurable by enzyme-linked immunosorbant assays.

  20. Effect of gold immersion time on the electrochemical migration property of electroless nickel/immersion gold surface finishing.

    PubMed

    Bui, Q V; Yoon, Jeong-Won; Jung, Seung-Boo

    2012-04-01

    In this study, the electrochemical performance of an electroless nickel/immersion gold (ENIG) surface finish was evaluated as a function of the Au immersion time by the water immersion migration test. As the Au plating time increased, the electroless nickel phosphorous (EN-P) changed from amorphous to crystalline and then increased in crystallinity. X-ray diffraction (XRD) was used to evaluate the crystallinity of the plating layer. The electrical resistance of the electrodes was tracked as the sample was immersed in water with a 5 V bias. The microstructures of the electrodes after the electrochemical migration test were observed by using secondary electron microscopy (SEM) and energy dispersive spectroscopy (EDS). As the Au immersion time increased, the EN-P's crystallinity and Au thickness increased. This enhanced the electrochemical migration protection of the surface finish layer.

  1. Bioconjugation of trypsin onto gold nanoparticles: effect of surface chemistry on bioactivity.

    PubMed

    Hinterwirth, Helmut; Lindner, Wolfgang; Lämmerhofer, Michael

    2012-07-06

    The systematic study of activity, long-time stability and auto-digestion of trypsin immobilized onto gold nanoparticles (GNPs) is described in this paper and compared to trypsin in-solution. Thereby, the influence of GNP's size and immobilization chemistry by various linkers differing in lipophilicity/hydrophilicity and spacer lengths was investigated with regard to the bioactivity of the conjugated enzyme. GNPs with different sizes were prepared by reduction and simultaneous stabilization with trisodium citrate and characterized by UV/vis spectra, dynamic light scattering (DLS), ζ-potential measurements and transmission electron microscopy (TEM). GNPs were derivatized by self-assembling of bifunctional thiol reagents on the nanoparticle (NP) surface via dative thiol-gold bond yielding a carboxylic acid functionalized surface. Trypsin was either attached directly via hydrophobic and ionic interactions onto the citrate stabilized GNPs or immobilized via EDC/NHS bioconjugation onto the carboxylic functionalized GNPs, respectively. The amount of bound trypsin was quantified by measuring the absorbance at 280 nm. The activity of bound enzyme and its Michaelis Menten kinetic parameter K(m) and v(max) were measured by the standard chromogenic substrate N(α)-Benzoyl-DL-arginine 4-nitroanilide hydrochloride (BApNA). Finally, digestion of a standard protein mixture with the trypsin-conjugated NPs followed by analysis with LC-ESI-MS and successful MASCOT search demonstrated the applicability of the new heterogenous nano-structured biocatalyst. It could be shown that the amount of immobilized trypsin and its activity can be increased by a factor of 6 using a long hydrophilic spacer with simultaneous reduced auto-digestion and reduced digestion time. The applicability of the new trypsin bioreactor was proven by digestion of casein and identification of α- as well as κ-casein by subsequent MASCOT search. Copyright © 2012 Elsevier B.V. All rights reserved.

  2. 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.

  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.

  4. Targeting and molecular imaging of HepG2 cells using surface-functionalized gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Rathinaraj, Pierson; Lee, Kyubae; Choi, Yuri; Park, Soo-Young; Kwon, Oh Hyeong; Kang, Inn-Kyu

    2015-07-01

    Mercaptosuccinic acid (M)-conjugated gold nanoparticles (GM) were prepared and characterized by transmission electron microscope and dynamic light scattering. M was used to improve the monodispersity and non-specific intracellular uptake of nanoparticles. Lactobionic acid (L) was subsequently conjugated to the GM to target preferentially HepG2 cells (liver cancer cells) that express asialoglycoprotein receptors (ASGPR) on their membrane surfaces and facilitate the transit of nanoparticles across the cell membrane. The mean size of lactobionic acid-conjugated gold nanoparticle (GL) was approximately 10 ± 0.2 nm. Finally, the Atto 680 dye (A6) was coupled to the nanoparticles to visualize their internalization into HepG2 cells. The interaction of surface-modified gold nanoparticles with HepG2 cells was studied after culturing cells in media containing the GM or L-conjugated GM (GL).

  5. Microstructural and surface characterization of thin gold films on n-Ge (1 1 1)

    NASA Astrophysics Data System (ADS)

    Nel, J. M.; Chawanda, A.; Auret, F. D.; Jordaan, W.; Odendaal, R. Q.; Hayes, M.; Coelho, S.

    2009-12-01

    Thin gold films were fabricated by vacuum resistive deposition on the n-Ge (1 1 1) wafers. The films were annealed between 300 and 600 °C. These resulting thin films were then characterised using scanning electron microscopy (field emission and back-scattering modes), Rutherford back scattering spectroscopy and time of flight secondary ion mass spectroscopy (TOF-SIMS). For temperatures below the eutectic temperature the distribution of both the gold and the germanium on the surface are uniform. Above the eutectic temperature, the formation of gold rich islands on the surface of the Germanium were observed. These changes in the microstructure were found to correspond to changes in the electrical characteristics of the diodes.

  6. 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.

  7. 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.

  8. Spontaneous deposition of gold nanoparticle nanocomposite on polymer surfaces through sol-gel chemistry

    NASA Astrophysics Data System (ADS)

    Choi, Yong-Jae; Chiu, Chi-Kai; Luo, Tzy-Jiun M.

    2011-01-01

    A aminosilica nanocomposite layer containing a monolayer of gold nanoparticles (d = 18-22 nm) with a well-defined spacing was spontaneously deposited on an unmodified polystyrene surface via a sol-gel reaction when the reduction reaction was carried out under 1:8 molar ratio (gold(III):aminosilane). The amount of aminosilica and spacing between gold nanoparticles were found to be a function of the aminosilane:water molar ratio, which contributes to the plasmonic property of the films with its absorption wavelength ranging between 701 and 548 nm. Furthermore, the nanocomposite film that consists of a monolayer of nanoparticles in aminosilica has also been deposited on the surface of polystyrene beads. This core-shell structure was found capable of storing electrostatic charges and forming a well-separated 2D array.

  9. Carbon disulfide mediated self-assembly of Laccase and iron oxide nanoparticles on gold surfaces for biosensing applications.

    PubMed

    Almeida, I; Henriques, F; Carvalho, M D; Viana, A S

    2017-01-01

    A simple one-step methodology was explored to prepare enzyme-modified nanostructured electrodes for the development of biosensing interfaces. Magnetite type nanoparticles conjugated with Laccase were immobilized on gold surfaces. This approach relies on the reaction between carbon disulfide and amine groups of biomolecules to form dithiocarbamate (DTC) moieties, as well as on the strong affinity between sulfur species and metals. Special emphasis was given to demonstrate DTC formation in aqueous solution and further attachment to iron oxide nanoparticles and to gold electrodes. UV-visible spectroscopy confirmed the functionalization of nanoparticles by DTC using a model secondary amine (N-hexylmethylamine). The direct attachment of modified iron oxide nanoparticles (with ca. 20 or 40nm mean sizes) to gold electrodes was investigated using the hormone epinephrine, with well-known electrochemical properties. A high amount of immobilized epinephrine and a facilitated redox conversion was observed for modified electrodes containing iron oxide nanoparticles. The success of this simple and robust method was confirmed by X-ray photoelectronic spectroscopy. Finally, the catalytic activity of modified gold with iron oxide nanoparticles and Laccase was evaluated toward 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid diammonium salt (ABTS). Chronoamperometric studies revealed a significant catalytic activity of immobilized Laccase in the presence of the nanoparticles, in particular for the largest ones (40nm), with a sensitivity for ABTS oxidation of 100mAM(-1)cm(-2). Copyright © 2016 Elsevier Inc. All rights reserved.

  10. 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.

  11. Tuning Surface Structure of 3D Nanoporous Gold by Surfactant-Free Electrochemical Potential Cycling.

    PubMed

    Wang, Zhili; Ning, Shoucong; Liu, Pan; Ding, Yi; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

    2017-09-14

    3D dealloyed nanoporous metals have emerged as a new class of catalysts for various chemical and electrochemical reactions. Similar to other heterogeneous catalysts, the surface atomic structure of the nanoporous metal catalysts plays a crucial role in catalytic activity and selectivity. Through surfactant-assisted bottom-up synthesis, the surface-structure modification has been successfully realized in low-dimensional particulate catalysts. However, the surface modification by top-down dealloying has not been well explored for nanoporous metal catalysts. Here, a surfactant-free approach to tailor the surface structure of nanoporous gold by surface relaxation via electrochemical redox cycling is reported. By controlling the scan rates, nanoporous gold with abundant {111} facets or {100} facets can be designed and fabricated with dramatically improved electrocatalysis toward the ethanol oxidation reaction. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. In situ spectroscopy of ligand exchange reactions at the surface of colloidal gold and silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Dinkel, Rebecca; Peukert, Wolfgang; Braunschweig, Björn

    2017-04-01

    Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ. In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time. First, a brief introduction to SHS and basic features of the SHS of nanoparticles are given. After that, we demonstrate how the SHS intensity decrease can be correlated to the thiol coverage which allows for the determination of the Gibbs free energy of adsorption and the surface coverage.

  13. Investigation of Venus Surface Properties

    NASA Technical Reports Server (NTRS)

    Ford, Peter G.

    2002-01-01

    Strong localized radar echoes have been observed at decimeter wavelengths from the highlands of Venus since the earliest radar maps were obtained over 30 years ago. These echoes are some five to ten times stronger than those from the presumably basaltic rocks seen at lower altitudes elsewhere on Venus. Observations of thermal emission from the visible disk of Venus at wavelengths corresponding to those used in the radar mapping confirm that the regions of high reflectivity also exhibit low emissivity, as expected from considerations of detailed thermodynamic balance. Two possibilities have been put forward to explain this unexpected aspect of the Venus highlands: 1) surface materials of high effective dielectric constant, probably associated with finite electrical conductivity, and 2) volume scattering associated with multiple scattering from a layer of very-low-loss material containing voids and extending down a few hundred wavelengths beneath the surface. Analogs to these two mechanisms are found elsewhere in the solar system, and each is capable of explaining the basic observations. as of the early 1990's. In 1993, however, it became possible to carry out a bistatic observation of the anomalous highland regions using the Magellan spacecraft, then in orbit about Venus. In this experiment the on-board telemetry transmitter was aimed at the planet's surface with its linear S-band polarization vector oriented at 45 deg to the spacecraft-Venus-Earth scattering plane. The pointing of the transmitting antenna was adjusted so that the spacecraft-to-illuminated-surface incidence angle equalled the Earth-to-Venus-surface incidence angle. In this way, the experiment emphasized the specular scattering component. A full Stokes-Vector analysis of the reflected signal as received on Earth was carried out as the illuminated region scanned across the highland regions of Venus. From the observed position angle of the echo, it was possible to calculate the Fresnel reflectivity of

  14. Findings on the interaction of the antimicrobial peptide cecropin-melittin with a gold surface from molecular dynamics studies.

    PubMed

    Ferreira, André F; Rai, Akhilesh; Ferreira, Lino; Simões, Pedro N

    2017-04-01

    The immobilization of gold nanoparticles (AuNPs) with antimicrobial peptides (AMPs) is a new and promising way to enhance both the activity and targeting capabilities of AMPs. However, a full understanding of the adsorption process underlying these materials is still lacking. Cecropin-melittin is a peptide with a broad antimicrobial activity while displaying low hemolytic properties, whose conjugation with AuNPs has not been studied before. In this context, we report the investigation of the adsorption process of the cecropin-melittin peptide, with (CM-SH) and without (CM) cysteine at its C-terminus, onto a gold surface based on all-atom MD simulations. Our results show that the way the peptides approach the surface dictates the final conformation and the time required to achieve it in both CM-SH and CM cases. Most important, it is demonstrated that the presence of cysteine promotes a faster conformational stabilization during the lockdown regime of the CM-SH peptide, noticeably affecting this by acting as a preferential anchoring point. This investigation represents a first step in rationalizing, with atomistic detail, some experimentally observed features of CM-SH and CM immobilized gold nanoparticles.

  15. Understanding the effect of size and shape of gold nanomaterials on nanometal surface energy transfer.

    PubMed

    Rakshit, Soumyadipta; Moulik, Satya Priya; Bhattacharya, Subhash Chandra

    2017-04-01

    Gold Nanomaterials (GNMs) interact with fluorophores via electromagnetic coupling under excitation. In this particular work we carried out (to the best of our knowledge for the first time) a comprehensive study of systematic quenching of a blue emitter 2-Anthracene Sulfonate (2-AS) in the presence of gold nanoparticles of different size and shape. We synthesized gold nanomaterials of four different dimensions [nanoparticle (0D), nanorod (1D), nanotriangle (2D) and nanobipyramids (3D)] and realized the underlying effect on the emitting dipole in terms of steady and time resolved fluorescence. Nanometal Surface Energy Transfer (NSET) has already been proved to be the best long range spectroscopic ruler so far. Many attempts have been made to understand the interaction between a fluorescent molecule and gold nanomaterials. But not a single model can interpret alone the interaction phenomena. We have opted three different models to compare the experimental and theoretical data. Due to the presence of size dependent absorptivity and dielectric function, modified CPS-Kuhn model was proved to be the worthiest to comprehend variance of behavior of an emitting dipole in close proximity to nanometal surface by coupling with the image dipole of gold nanomaterials.

  16. 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.

  17. DFT study of the adsorption of D-(L-)cysteine on flat and chiral stepped gold surfaces.

    PubMed

    Fajín, José L C; Gomes, José R B; Cordeiro, M Natália D S

    2013-07-16

    The adsorption of cysteine onto the intrinsically chiral gold surface, Au(321)(R,S), was investigated by means of a periodic supercell density functional theory approach. The results are compared to those obtained at the same level of theory with a nonchiral surface having the same terrace orientation, the Au(111) surface. Neutral and zwitterionic cysteine forms of the L and D enantiomers are considered, as are surface coverage effects. It was found that at high coverage the zwitterionic forms of L- and D-cysteine are more stable on the Au(321)(R,S) faces of the stepped surface and also on the flat Au(111) surface, leading to highly organized cysteine monolayers. However, at low coverage the adsorption of cysteine dimers, with the pairs interacting through their carbonyl groups, is more favorable than or at least equally favorable to the adsorption of single cysteine molecules on both surfaces. A comparison between the cysteine adsorption on the two different surface structures shows that the adsorption on the stepped surface is clearly more favorable than on the flat surface, revealing the importance of the low-coordinated gold atoms in the adsorption of these species. Furthermore, non-negligible differences between the adsorption energy of the enantiomers of cysteine were found both at high and low coverage, thus showing the enantiospecificity of this intrinsically chiral surface regarding cysteine adsorption. This adsorption occurs with the cysteine binding the surface through only one contact point (by its sulfur atom), in contrast to previous work where the enantiospecific adsorption of cysteine has been related to two nonequivalent binding sites of the cysteine enantiomers with the surface.

  18. 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.

  19. Investigation of Surface Plasmon Dispersion

    DTIC Science & Technology

    1980-09-30

    of Cs-Ag and the Cs-O-Ag surface layers are likely to have energy bands rather than dis- crete energies . We have analyzed the data presented in...into the Au-Si interface. When the photon energy is larger than the band gap of the semiconductor, as in our case, the EM field can create elec- tron...in which electrons are injected from Ad into Si. To study only the internal photo- emission, SPW with photon energies between the band gap of Si and

  20. 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.

  1. Surface plasmon resonance in gold nanoparticles: a review

    NASA Astrophysics Data System (ADS)

    Amendola, Vincenzo; Pilot, Roberto; Frasconi, Marco; Maragò, Onofrio M.; Iatì, Maria Antonia

    2017-05-01

    In the last two decades, plasmon resonance in gold nanoparticles (Au NPs) has been the subject of intense research efforts. Plasmon physics is intriguing and its precise modelling proved to be challenging. In fact, plasmons are highly responsive to a multitude of factors, either intrinsic to the Au NPs or from the environment, and recently the need emerged for the correction of standard electromagnetic approaches with quantum effects. Applications related to plasmon absorption and scattering in Au NPs are impressively numerous, ranging from sensing to photothermal effects to cell imaging. Also, plasmon-enhanced phenomena are highly interesting for multiple purposes, including, for instance, Raman spectroscopy of nearby analytes, catalysis, or sunlight energy conversion. In addition, plasmon excitation is involved in a series of advanced physical processes such as non-linear optics, optical trapping, magneto-plasmonics, and optical activity. Here, we provide the general overview of the field and the background for appropriate modelling of the physical phenomena. Then, we report on the current state of the art and most recent applications of plasmon resonance in Au NPs.

  2. A numerical study of the sensitivity of surface plasmon resonance bimetallic silver-gold alloys using boundary element method

    NASA Astrophysics Data System (ADS)

    Putra, M. H.; Djuhana, D.; Fauzia, V.; Harmoko, A.; Imawan, C.

    2017-04-01

    In this study, we have systematically investigated the sensitivity of surface plasmon resonance bimetallic silver-gold alloys by means of metallic nanoparticle simulation, MNPBEM with respect to the diameter, mole fraction, and refractive index medium variation. The sensitivity of surface plasmon resonance was obtained from a fitting linear between the value of the peak position LSPR spectra and the refractive index medium. Interestingly, it was found the sensitivity of surface plasmon resonance increased as the diameter increased for a diameter less than 40 nm, whereas the sensitivity of surface plasmon resonance exhibited the fluctuation values for diameter above 40 nm. The highest value of the sensitivity occurred at the silver mole fraction at x = 0.6 rather than at x = 1.0 (pure silver particle). This result also showed the sensitivity of surface plasmon resonance pure silver particle (x = 1) was greater than gold particle (x = 0). The sensitivity of surface plasmon resonance was not only affected by the diameter but also influenced by the mole fraction.

  3. DNA-directed gold nanodimers with tailored ensemble surface-enhanced Raman scattering properties.

    PubMed

    Lan, Xiang; Chen, Zhong; Lu, Xuxing; Dai, Gaole; Ni, Weihai; Wang, Qiangbin

    2013-11-13

    Gold nanodimers (GNDs) are assembled with high uniformity as ideal surface-enhanced Raman scattering (SERS) substrates through DNA-directed self-assembly of gold nanoparticles. The interparticle distance within GNDs is precisely tailored on the order of a few nanometers with changing the molecule length of DNA bridge. The ensemble SERS activity of monodispersed GNDs is then rationally engineered by modifying the structural parameters of GNDs including the particle size and interparticle distance. Theoretical studies on the level of single GND evidence the particle size- and interparticle-distance-dependent SERS effects, consistent with the ensemble averaged measurements.

  4. Enhanced detection sensitivity of higher-order vibrational modes of gold nanodisks on top of a GaN nanorod array through localized surface plasmons

    NASA Astrophysics Data System (ADS)

    Yang, Szu-Chi; Wei, Pei-Kuen; Hsiao, Hui-Hsin; Mante, Pierre-Adrien; Huang, Yu-Ru; Chen, I.-Ju; Chang, Hung-Chun; Sun, Chi-Kuang

    2014-11-01

    We report a method that enables the excitation of localized surface plasmons (LSPs) in a gold nanodisk array by placing each nanodisk on top of a GaN nanorod. When the rod length was much longer than the plasmon penetration depth inside the nanorod, the plasmonic field was found to be localized, and coupling between neighboring gold nanodisks was eliminated. The interaction between LSPs and acoustic vibrations in gold nanodisks was then investigated. Owing to the strong localization of the plasmonic field, weak, higher-order vibrational modes of gold nanodisk could be optically observed. Furthermore, such an LSP-based acoustic sensor could be operated at any angle of incident light. Our study not only provides an approach to excite LSPs in high-density metallic arrays, but also opens one of the possible solutions for the development of highly sensitive sub-terahertz hypersonic sensors with high angle tolerance of incident light.

  5. Influence of pH upon surface-enhanced enzyme-catalyzed luminol chemiluminescence at vicinity of nanoscale-corrugated gold and silver films.

    PubMed

    Ou, Meigui; Lu, Guowei; Shen, Hong; Descamps, Armel; Marquette, Christophe André; Blum, Loïc Jacques; Roux, Stéphane; Tillement, Olivier; Cheng, Bolin; Perriat, Pascal

    2008-01-01

    Au and Ag biochips were fabricated to investigate the influence of pH upon the chemiluminescence (CL) of luminol at vicinity of surface-adsorbed peroxidase. A nanoscaled-corrugation of the metal induces an enhancement of the luminol CL which is maximal in the pH range favoring peroxidase catalysis and greater for gold than for silver. This is the proof that, in the CL process, the reactions involving peroxidase are surface-enhanced near corrugated surfaces.

  6. Random Surface Texturing of Silicon Dioxide Using Gold Agglomerates

    DTIC Science & Technology

    2016-07-01

    photons incident on the surface of the solar cell actually end up in the active region able to convert photon energy into electrical energy . Several...mechanisms contribute to energy losses in solar cells, including heat loss, recombination loss, and reflective loss. Of those, reflection of incident...in an AR coating on solar cells. 15. SUBJECT TERMS anti-reflective, AR coatings, textured surface structures, silicon dioxide, SiO2 16. SECURITY

  7. 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.

  8. 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

  9. 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.

  10. Dynamic Monitoring of Mechano-Sensing of Cells by Gold Nanoslit Surface Plasmon Resonance Sensor

    PubMed Central

    Wu, Shu-Han; Lee, Kuang-Li; Weng, Ruei-Hung; Zheng, Zhao-Xian; Chiou, Arthur; Wei, Pei-Kuen

    2014-01-01

    We demonstrated a real-time monitoring of live cells upon laminar shear stress stimulation via surface plasmon resonance (SPR) in gold nanoslit array. A large-area gold nanostructure consisted of 500-nm-period nanoslits was fabricated on a plastic film using the thermal-annealed template-stripping method. The SPR in the gold nanoslit array provides high surface sensitivity to monitor cell adhesion changes near the sensor surface. The human non-small cell lung cancer (CL1-0), human lung fibroblast (MRC-5), and human dermal fibroblast (Hs68) were cultured on the gold nanoslits and their dynamic responses to laminar shear stress were measured under different stress magnitudes from 0 to 30 dyne/cm2. Cell adhesion was increased in CL1-0 under shear flow stimulation. No adhesion recovery was observed after stopping the flow. On the other hand, MRC-5 and Hs68 decreased adhesion and recovered from the shear stress. The degree of recovery was around 70% for MRC-5. This device provides dynamic study and early detection of cell adhesion changes under shear flow conditions. PMID:24586846

  11. Gold Nanoplates for a Localized Surface Plasmon Resonance-Based Boric Acid Sensor.

    PubMed

    Morsin, Marlia; Mat Salleh, Muhamad; Ali Umar, Akrajas; Sahdan, Mohd Zainizan

    2017-04-25

    Localized surface plasmon resonance (LSPR) properties of metallic nanostructures, such as gold, are very sensitive to the dielectric environment of the material, which can simply be adjusted by changing its shape and size through modification of the synthesizing process. Thus, these unique properties are very promising, particularly for the detection of various types of chemicals, for example boric acid which is a non-permitted preservative employed in food preparations. For the sensing material, gold (Au) nanoplates with a variety of shapes, i.e., triangular, hexagonal, truncated pentagon and flat rod, were prepared using a seed-mediated growth method. The yield of Au nanoplates was estimated to be ca. 63% over all areas of the sensing material. The nanoplates produced two absorption bands, i.e., the transverse surface plasmon resonance (t-SPR) and the longitudinal surface plasmon resonance (l-SPR) at 545 nm and 710 nm, respectively. In the sensing study, these two bands were used to examine the response of gold nanoplates to the presence of boric acid in an aqueous environment. In a typical process, when the sample is immersed into an aqueous solution containing boric acid, these two bands may change their intensity and peak centers as a result of the interaction between the boric acid and the gold nanoplates. The changes in the intensities and peak positions of t-SPR and l-SPR linearly correlated with the change in the boric acid concentration in the solution.

  12. Gold Nanoplates for a Localized Surface Plasmon Resonance-Based Boric Acid Sensor

    PubMed Central

    Morsin, Marlia; Mat Salleh, Muhamad; Ali Umar, Akrajas; Sahdan, Mohd Zainizan

    2017-01-01

    Localized surface plasmon resonance (LSPR) properties of metallic nanostructures, such as gold, are very sensitive to the dielectric environment of the material, which can simply be adjusted by changing its shape and size through modification of the synthesizing process. Thus, these unique properties are very promising, particularly for the detection of various types of chemicals, for example boric acid which is a non-permitted preservative employed in food preparations. For the sensing material, gold (Au) nanoplates with a variety of shapes, i.e., triangular, hexagonal, truncated pentagon and flat rod, were prepared using a seed-mediated growth method. The yield of Au nanoplates was estimated to be ca. 63% over all areas of the sensing material. The nanoplates produced two absorption bands, i.e., the transverse surface plasmon resonance (t-SPR) and the longitudinal surface plasmon resonance (l-SPR) at 545 nm and 710 nm, respectively. In the sensing study, these two bands were used to examine the response of gold nanoplates to the presence of boric acid in an aqueous environment. In a typical process, when the sample is immersed into an aqueous solution containing boric acid, these two bands may change their intensity and peak centers as a result of the interaction between the boric acid and the gold nanoplates. The changes in the intensities and peak positions of t-SPR and l-SPR linearly correlated with the change in the boric acid concentration in the solution. PMID:28441323

  13. Tuning the Surface Composition, Spatial Arrangement, and Thermal Release Behavior of DNA-Gold Nanomaterials

    NASA Astrophysics Data System (ADS)

    Diaz, Julian

    Combining multiple functions and controlling their relative organization on the surface, as well as controlling the release of payloads will be essential properties of nanomaterials for future medical applications. In this thesis we studied these properties using as a model DNA-gold nanoparticles, one of the most promising nanomaterials for medical purposes. First, we studied strategies to control the density and the ratio of combinations of labeled DNA on gold nanoparticles. Using two approaches, thiol self-assembly and DNA-directed assembly (hybridization) we found that thiol self-assembly leads to a higher density of labeled DNA per particle, but poor ratio control, while DNA-directed assembly is better at controlling the proportions of labeled DNA on the particle but the number of strands is lower than the thiol self-assembly approach. Second, to control the relative position of the labels on the particle we used DNA-doublers and Y-shaped DNA complexes to tune the distance between tags. Off particle experiments indicated that the spacing between labels can be controlled in the Angstrom-nanometer scale. On particle experiments showed the apparent formation of these constructs; however more experiments are needed to attain quantitative results. The aim of the last investigation was to achieve thermal stepwise release of DNA from DNA-gold nanoparticles. To do so, it is necessary to obtain sharp thermal dissociation, or melting, transitions as well as control over the melting temperature. Taking advantage of the cooperative properties of DNA, we found that sharpened melting can be achieved using branched DNA-doublers hybridized with complementary DNA bound to the nanoparticle. Tuning the melting temperature can be achieved by modifying the branches of the hybridized doublers with abasic groups. Using these two findings, we sequentially released two DNA-doublers from the same nanoparticle, in a very narrow temperature window, and with minimal overlapping. Current

  14. 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.

  15. Surface-enhanced Raman scattering from graphene covered gold nanocap arrays

    NASA Astrophysics Data System (ADS)

    Long, Kailin; Luo, Xiaoguang; Nan, Haiyan; Du, Deyang; Zhao, Weiwei; Ni, Zhenhua; Qiu, Teng

    2013-11-01

    This work reports an efficient method to fabricate large-area flexible substrates for surface enhanced Raman scattering (SERS) application. Our technique is based on a single-step direct imprint process via porous anodic alumina stamps. Periodic hexagonal arrangements of porous anodic alumina stamps are transferred to the polyethylene terephthalate substrates by mechanically printing process. Printed nanocaps will turn into "hot spots" for electromagnetic enhancement with a deposited gold film by high vacuum evaporation. The gaps between the nanocaps are controllable with a tight correspondence to the thickness of the deposited gold, which dramatically influence the enhancement factor. After covered with a single-layer graphene sheet, the gold nanocap substrate can be further optimized with an extra enhancement of Raman signals, and it is available for the trace detection of probe molecules. This convenient, simple, and low-cost method of making flexible SERS-active substrates potentially opens a way towards biochemical analysis and disease detection.

  16. 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.

  17. 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

  18. 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.

  19. Candida rugosa lipase immobilization on hydrophilic charged gold nanoparticles as promising biocatalysts: Activity and stability investigations.

    PubMed

    Venditti, Iole; Palocci, Cleofe; Chronopoulou, Laura; Fratoddi, Ilaria; Fontana, Laura; Diociaiuti, Marco; Russo, Maria Vittoria

    2015-07-01

    In this work, a simple and versatile methodology to obtain two different bioconjugated systems has been developed by the immobilization of Candida rugosa lipase (CRL) on hydrophilic gold nanoparticles functionalized with 2-diethylaminoethanethiol hydrochloride (DEA) or with sodium 3-mercapto-1-propanesulfonate (3MPS), namely Au-DEA@CRL and Au-3MPS@CRL. Both spectroscopic and morphological properties of metal nanoparticles have been deeply investigated. The enzyme loading and lipolytic activity of AuNPs@CRL bioconjugates have been studied with respect to different surface functionalization and compared with the free enzyme. Some physical and chemical parameters had a strong effect on enzyme activity and stability, that were improved in the case of the Au-DEA@CRL bioconjugate, which showed a remarkable biocatalytic performance (95% of residual lipolytic activity compared with free CRL) and stability in experimental conditions concerning pH (range 5-8) and temperature (range 20-60°C), as often required for the industrial scale up of catalytic systems.

  20. Detuned surface plasmon resonance scattering of gold nanorods for continuous wave multilayered optical recording and readout.

    PubMed

    Taylor, Adam B; Kim, Jooho; Chon, James W M

    2012-02-27

    In a multilayered structure of absorptive optical recording media, continuous-wave laser operation is highly disadvantageous due to heavy beam extinction. For a gold nanorod based recording medium, the narrow surface plasmon resonance (SPR) profile of gold nanorods enables the variation of extinction through mulilayers by a simple detuning of the readout wavelength from the SPR peak. The level of signal extinction through the layers can then be greatly reduced, resulting more efficient readout at deeper layers. The scattering signal strength may be decreased at the detuned wavelength, but balancing these two factors results an optimal scattering peak wavelength that is specific to each layer. In this paper, we propose to use detuned SPR scattering from gold nanorods as a new mechanism for continuous-wave readout scheme on gold nanorod based multilayered optical storage. Using this detuned scattering method, readout using continuous-wave laser is demonstrated on a 16 layer optical recording medium doped with heavily distributed, randomly oriented gold nanorods. Compared to SPR on-resonant readout, this method reduced the required readout power more than one order of magnitude, with only 60 nm detuning from SPR peak. The proposed method will be highly beneficial to multilayered optical storage applications as well as applications using a continuous medium doped heavily with plasmonic nanoparticles.

  1. Surface plasmon resonance of gold nanoparticles assemblies at liquid | liquid interfaces.

    PubMed

    Hojeij, Mohamad; Younan, Nathalie; Ribeaucourt, Lydie; Girault, Hubert H

    2010-09-01

    Surface plasmon resonance (SPR) was observed when a planar close-packed assembly of gold nanoparticles (Au NPs) is adsorbed at the water|1,2-dichloroethane interface. Aqueous gold nanoparticles, 13 or 16 nm in diameter, are deposited at the interface by adding methanol to form a close-packed film with a visible gold mirror reflectance. By total internal reflection of a light beam on the interface, the angular dependence of the interfacial reflectivity was measured in a pseudo-Kretschmann configuration and compared to Fresnel simulations for a homogeneous gold film. The experimental angles for minimum reflectivity were found to match the simulated values. Then, the fluorescence of dye molecules co-adsorbed within 13 and 16 nm gold nanoparticles assemblies at the liquid|liquid interface was measured. The fluorescence intensity under SPR is revealed to be much greater than under total internal reflection conditions, yielding an enhancement factor of approximately 30 and 50 for 13 and 16 nm Au NPs assemblies, respectively. Also, the fluorescence lifetime was found to decrease under SPR conditions.

  2. XPS and NRA investigations during the fabrication of gold nanostructured functionalized screen-printed sensors for the detection of metallic pollutants

    NASA Astrophysics Data System (ADS)

    Jasmin, Jean-Philippe; Miserque, Frédéric; Dumas, Eddy; Vickridge, Ian; Ganem, Jean-Jacques; Cannizzo, Caroline; Chaussé, Annie

    2017-03-01

    An all covalent nanostructured lead sensor was built by the successive grafting of gold nanoparticles and carboxylic ligands at the surface of self-adhesive carbon screen-printed electrodes (SPEs). Surface analysis techniques were used in each step in order to investigate the structuration of this sensor. The self-adhesive surfaces were made from the electrochemical grafting of p-phenylenediamine at the surface of the SPEs via diazonium salts chemistry. The quantity of grafted aniline functions, estimated by Nuclear Reaction Analysis (NRA) performed with p-phenylenediamine labelled with 15N isotope, is in agreement with an almost complete coverage of the electrode surface. The subsequent diazotization of the aniline functions at the surface of the SPEs was performed; X-ray Photoelectron Spectroscopy (XPS) allowed us to consider a quantitative conversion of the aniline functions into diazonium moieties. The spontaneous grafting of gold nanoparticles on the as-obtained reactive surfaces ensures the nanostructuration of the material, and XPS studies showed that the covalent bonding of the gold nanoparticles at the surface of the SPEs induces a change both in the Au-4f (gold nanoparticles) and Cl-2p (carbon ink) core level signals. These unusual observations are explained by an interaction between the carbon ink constituting the substrate and the gold nanoparticles. Heavy and toxic metals are considered of major environmental concern because of their non-biodegradability. In a final step, the grafting of the carboxylic ligands at the surface of the SPEs and an accumulation step in the presence of lead(II) cations allowed us to evidence the interest of nanostructured materials as metallic pollutants sensors.

  3. 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.

  4. A comparative PM-IRRAS and ellipsometry study of the adsorptive behaviour of bovine serum albumin on a gold surface.

    PubMed

    Dargahi, Mahdi; Omanovic, Sasha

    2014-04-01

    Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and ellipsometry were used ex situ to investigate adsorption of bovine serum albumin (BSA) on a gold surface, in terms of the adsorption equilibrium and kinetics. The aim of the work was to examine if the two different techniques give similar/complementary results under the same experimental conditions employing the same protein/surface system, and thus validate the use of the techniques for the investigation of protein/surface interactions under the applied experimental conditions, in general. It was found that the adsorption of BSA on gold follows Type I isotherm, which can be described by the Freundlich isotherm. The initial BSA adsorption kinetics was found to be very fast, and the results were modelled using a two-step kinetic model. The first step represents reversible BSA adsorption that yields BSA adsorbed in a native configuration (θ1) that is not thermodynamically stable. The second step represents the irreversible transformation of this protein configuration into a thermodynamically stable surface-adsorbed configuration (θ2). It was found that the θ2/θ1 ratio increased with time. Finally, the comparison of the results obtained by the two techniques showed a very good agreement. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. Some Theoretical and Experimental Insights on the Mechanistic Routes Leading to the Spontaneous Grafting of Gold Surfaces by Diazonium Salts.

    PubMed

    Berisha, Avni; Combellas, Catherine; Kanoufi, Frédéric; Decorse, Philippe; Oturan, Nihal; Médard, Jérôme; Seydou, Mahamadou; Maurel, François; Pinson, Jean

    2017-09-05

    The spontaneous grafting of diazonium salts on gold may involve the carbocation obtained by heterolytic dediazonation and not necessarily the radical, as usually observed on reducing surfaces. The mechanism is addressed on the basis of DFT calculations and experiments carried out under conditions where the carbocation and the radical are produced selectively. The calculations indicate that the driving force of the reaction leading from a gold cluster, used as a gold model surface, and the carbocation to the modified cluster is higher than that of the analogous reaction starting from the radical. The experiments performed under conditions of heterolytic dediazonation show the formation of thin films on the surface of gold. The grafting of a carbocation is therefore possible, but a mechanism where the cleavage of the Ar-N bond is catalyzed by the surface of gold cannot be excluded.

  6. 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.

  7. Investigation of active biomolecules involved in the nucleation and growth of gold nanoparticles by Artocarpus heterophyllus Lam leaf extract

    NASA Astrophysics Data System (ADS)

    Jiang, Xinde; Sun, Daohua; Zhang, Genlei; He, Ning; Liu, Hongyu; Huang, Jiale; Odoom-Wubah, Tareque; Li, Qingbiao

    2013-06-01

    The effects of different biomolecules in Artocarpus heterophyllus Lam leaf extract on the morphology of obtained gold nanoparticles were investigated in this study. The results indicated that reducing sugars, flavones, and polyphenols consisting of about 79.8 % dry weight of the leaf extract were mainly involved in providing the dual function of reduction and the size/shape control during the biosynthesis. The gold nanoparticles present included 64 ± 10 nm nanospheres, 131 ± 18 nm nanoflowers, and 347 ± 136 nm (edge length) nanoplates and they were synthesized using the main content of reducing sugars, flavones, and polyphenols, respectively, after they were desorbed by the AB-8 macroporous adsorption resin column. Particularly, flower-like and triangular/hexagonal gold nanoparticles with a yield more than 80 % were obtained. Possible shape-directed agents for the nucleation and growth were characterized by FTIR, it can be seen that ketones were bound on the surface of the spherical and flower-like GNPs, while both the ketones and carbonyls bound on the Au {111} plane this may have favored the formation of the twin defects, which are very essential for nanoplates' formation.

  8. 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

    2014-06-03

    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.

  9. Surface Plasmon Mediated Chemical Solution Deposition of Gold Nanoparticles on a Nanostructured Silver Surface

    SciTech Connect

    Qiu, Jingjing; Wu, Yung-Chen; Wang, Yi-Chung; Engelhard, Mark H.; McElwee-White, Lisa; Wei, Wei

    2013-01-01

    Utilizing intrinsic surface properties to direct and control nanostructure growth on a large-scale surface is fundamentally interesting and holds great technological promise. Reported here is a novel "bottom-up" approach to fabricating sub-15 nm Au nanoparticles on a nanostructured Ag surface via a liquid-phase chemical deposition by using localized surface plasmon resonance (SPR) excitation. A molecular thermometry strategy was employed to investigate the SPR-mediated photothermal heating of the Ag film on nanosphere (AgFON) substrate and measured the surface temperature to be above 230 °C, which led to an efficient decomposition of CH3AuPPh3 to form Au nanoparticles on the Ag surface. Particle sizes were tunable between 3 to 10 nm by adjusting the deposition time. Moreover, investigation of the deposition kinetics revealed that the Au nanoparticle deposition was surface-limited by the Ag substrate. This SPR-mediated chemical solution deposition (SPMCSD) strategy should be extendable to the deposition of many other materials for various applications.

  10. 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

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

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

  12. The adsorption of cytochromes on a modified surface of gold electrodes

    NASA Astrophysics Data System (ADS)

    Zhavnerko, G. K.; Paribok, I. V.; Agabekov, V. E.; Zmachinskaya, Yu. A.; Usanov, S. A.

    2010-06-01

    The adsorption of cytochromes b 5 and c on the surface of gold electrodes, including the surface modified with cysteine, was studied. The quartz crystal microbalance method with parallel dissipation energy measurements, microcontact printing, and atomic-force microscopy were used to show that the special features of the structure and morphology of two-component cytochrome b 5 and c films were determined by the nature of the proteins themselves and the influence of the modifying "sublayer." The largest changes in the weight of films and dissipation energy were observed in the adsorption of cytochrome b 5 on a cytochrome c film deposited on a cysteine sublayer. Atomic-force microscopy measurements showed that strong interaction between cytochrome c and b 5 molecules on the surface of gold modified with cysteine could be related to the formation of the corresponding protein complex.

  13. Regenerating titanium ventricular assist device surfaces after gold/palladium coating for scanning electron microscopy.

    PubMed

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

    2010-01-01

    Titanium is one of the most commonly used materials for implantable devices in humans. 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 nonconductive 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 titaniumsurfaces 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. (c) 2009 Wiley-Liss, Inc.

  14. 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

  15. Improving gold catalysis of nitroarene reduction with surface Pd

    SciTech Connect

    Pretzer, Lori A.; Heck, Kimberly N.; Kim, Sean S.; Fang, Yu-Lun; Zhao, Zhun; Guo, Neng; Wu, Tianpin; Miller, Jeffrey T.; Wong, Michael S.

    2016-04-01

    Nitroarene reduction reactions are commercialized catalytic processes that play a key role in the synthesisof many products including medicines, rubbers, dyes, and herbicides. Whereas bimetallic compositionshave been studied, a better understanding of the bimetallic structure effects may lead to improved indus-trial catalysts. In this work, the influence of surface palladium atoms supported on 3-nm Au nanoparticles(Pd-on-Au NPs) on catalytic activity for 4-nitrophenol reduction is explored. Batch reactor studies indi-cate Pd-on-Au NPs exhibit maximum catalytic activity at a Pd surface coverage of 150 sc%, with aninitial turnover frequency of ~3.7 mol-nitrophenol/mol-metalsurface/s, which was ~5.5× and ~13× moreactive than pure Au NPs and Pd NPs, respectively. Pd NPs, Au NPs, and Pd-on-Au NPs below 175 sc%show compensation behavior. Three-dimensional Pd surface ensembles (with ~4–5 atoms) previouslyidentified through X-ray adsorption spectroscopy provide the active sites responsible for the catalyticmaximum. These results demonstrate the ability to adjust systematically a structural feature (i.e., Pdsurface coverage) to yield a more active material.

  16. Gold nanoparticles: role of size and surface chemistry on blood protein adsorption

    NASA Astrophysics Data System (ADS)

    Benetti, F.; Fedel, M.; Minati, L.; Speranza, G.; Migliaresi, C.

    2013-06-01

    Material interaction with blood proteins is a critical issue, since it could influence the biological processes taking place in the body following implantation/injection. This is particularly important in the case of nanoparticles, where innovative properties, such as size and high surface to volume ratio can lead to a behavioral change with respect to bulk macroscopic materials and could be responsible for a potential risk for human health. The aim of this work was to compare gold nanoparticles (AuNP) and planar surfaces to study the role of surface curvature moving from the macro- to the nano-size in the process of blood protein adsorption. In the course of the study, different protocols were tested to optimize the analysis of protein adsorption on gold nanoparticles. AuNP with different size (10, 60 and 200 nm diameter) and surface coatings (citrate and polyethylene glycol) were carefully characterized. The stabilizing action of blood proteins adsorbed on AuNP was studied measuring the variation of size and solubility of the nanoparticles following incubation with single protein solutions (human serum albumin and fibrinogen) and whole blood plasma. In addition, we developed a method to elute proteins from AuNP to study the propensity of gold materials to adsorb plasma proteins in function of dimensional characteristics and surface chemistry. We showed a different efficacy of the various eluting media tested, proving that even the most aggressive agent cannot provide a complete detachment of the protein corona. Enhanced protein adsorption was evidenced on AuNP if compared to gold laminae (bare and PEGylated) used as macroscopic control, probably due to the superior AuNP surface reactivity.

  17. Gold nanostructures for detection of pesticides, nitrates and drugs using Surface Enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Nedyalkov, N.; Nikov, Ru.; Nikov, Ro.; Nikolov, A.; Atanasov, P.; Nakajima, Y.; Terakawa, M.; Sawczak, M.; Grochowska, K.; Sliwinski, G.

    2016-01-01

    In this work laser-assisted methods for metal nanostructures formation and their application as active substrates in Surface Enhanced Raman Spectroscopy are presented. The nanostructures are fabricated by laser processing of gold thin films deposited on low cost substrates as glass, ceramic, polymer and paper. The films are deposited by classical PLD technology. The produced films are then processed by nanosecond pulses delivered by nanosecond Nd:YAG laser system. At certain conditions the laser treatment leads to formation of discrete nanostructure on the substrate surface. Femtosecond Pulsed Laser Deposition in air is also applied for direct deposition of gold nanostructure. In another set of experiments gold nanoparticle colloids are fabricated by laser ablation of gold target in chloroform. The fabricated structures are then tested as active systems in SERS, as detection of pesticides (DDT), nitrates (NH4NO3), and drugs (Methylene blue) is demonstrated. The obtained results show that these nanostructures can be efficiently used in the detection and monitoring of materials with a high social impact.

  18. Self-assembly of gold nanoparticles on deep eutectic solvent (DES) surfaces.

    PubMed

    Raghuwanshi, V S; Ochmann, M; Polzer, F; Hoell, A; Rademann, K

    2014-08-14

    Self-assembly of gold nanoparticles was obtained by sputter deposition on DES. SAXS and TEM investigations reveal the formation of spherical nanoparticles with a mean diameter of 5 ± 0.5 nm. For extended sputtering times, the number density of AuNPs increases linearly and a very pronounced 1st and 2nd shell ordering is observed.

  19. Surface diffusion of gold nanoclusters on Ru(0001): effects of cluster size, surface defects and adsorbed oxygen atoms.

    PubMed

    Stein, Ori; Ankri, Jonathan; Asscher, Micha

    2013-08-28

    Understanding thermal behavior of metallic clusters on their solid supports is important for avoiding sintering and aggregation of the active supported metallic particles in heterogeneous catalysis. As a model system we have studied the diffusion of gold nano-clusters on modified Ru(0001) single crystal surfaces, employing surface density grating formation via a laser induced ablation technique. Surface modifications included damage induced by varying periods of Ne(+) ion sputtering at a collision energy of 2.8 keV and the effect of pre-adsorbed oxygen on the clean, defect free ruthenium surface. High density of surface damage, obtained at long sputter times, has led to enhanced diffusivity with lower onset temperature for diffusion. It is attributed to reduced cluster-surface commensurability which gives rise to smaller effective activation energy for diffusion. The diffusion of gold nano-clusters, 2 nm in size, was found to be insensitive to the oxygen surface concentration. The adsorbed oxygen acted as an "atomic layer lubricant", reducing friction between the cluster and the underlying surface. This has led to lower diffusivity onset temperatures (150 K) of the nano-clusters, with a stronger effect on smaller clusters.

  20. The effect of surface symmetry on the adsorption energetics of SCH 3 on gold surfaces studied using Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Masens, C.; Ford, M. J.; Cortie, M. B.

    2005-04-01

    Adsorption of methanethiol onto the three, high symmetry gold surfaces has been studied at the density functional level using a linear combination of atomic orbitals approach. In all three cases the bond energy between the thiolate radical and surface is typical of a covalent bond, and is of the order of 40 kcal mol -1. For the (1 1 1) surface the fcc hollow site is slightly more stable than the bridge site. For the (1 0 0) surfaces the four-fold hollow is clearly the most stable, and for the reconstructed (1 1 0) surface the bridge/edge sites either side of the first layer atoms are preferred. The calculated differences in binding energy between the three surfaces indicate that the thiolate will preferentially bind to the Au(1 1 0) or (1 0 0) before (1 1 1) surface, by about 10 kcal mol -1. The (1 1 0) surface is slightly more favourable than the (1 0 0), although the energy difference is only 3 kcal mol -1. The results suggest the possibility of selectively functionalising the different facets offered by a gold nanoparticle.

  1. Regioselective surface functionalization of lithographically designed gold nanorods by plasmon-mediated reduction of aryl diazonium salts.

    PubMed

    Nguyen, Mai; Kherbouche, Issam; Gam-Derouich, Sarra; Ragheb, Iman; Lau-Truong, Stéphanie; Lamouri, Aazdine; Lévi, Georges; Aubard, Jean; Decorse, Philippe; Félidj, Nordin; Mangeney, Claire

    2017-10-12

    Site-selective surface functionalization of anisotropic gold nanoparticles represents a major breakthrough for fully exploiting nanoparticle anisotropy. In this paper, we explore an original strategy for the regioselective functionalization of lithographically designed gold nanorods (AuNRs), based a combination of photo-induced plasmon excitation and aryl diazonium salt chemistry.

  2. A Detailed Experimental and Theoretical Investigation on the Chemical and Physical Behavior of Gold Nanoparticles under X-ray Radiation

    NASA Astrophysics Data System (ADS)

    Cheng, Neal

    A detailed investigation into the interaction between highly ionizing x-ray radiation and nanomaterials was performed. To begin, a theoretical model of the interactions of the system was created as an attempt to understand the relationship between the nanomaterial and the radiation-generated species. The model spans from the physical regime (<10-15s) which includes the physical absorption of x-rays, atomic processes, and electron emission to the diffusion regime (>10-10 s), during which the chemical species generated from radiolytic cleavage of water diffuses and reacts. A combination of methods was used in the simulation: Monte Carlo, Brownian diffusion, and kinetic rate equations. Several experimental systems were created for the purpose of testing the radio-enhancing effects of nanomaterials and the validity of the model: Firstly, the effects of localized energy deposition by gold nanoparticles were examined in a system consisting of 3 nm gold nanoparticles conjugated to DNA. In this system, single-strand breaks on DNA were used to probe the spatial distribution of energy nanometers around the nanoparticle. A comparison of the local energy deposition by gold nanoparticles versus global energy deposition by water was examined using the model. An additional 150% in DNA strand breaks was observed at 100 mM Tris (2-Amino-2-hydroxymethyl-propane-1,3-diol, represents 5nm diffusion distance), yet according to the model, the energy deposition of 10 gold nanoparticles on a strand of DNA accounts for only an additional 20%. Several explanations were given, such as the different reactivity of radical at short distance, the cross-linking of multiple DNA to a single nanoparticle, and geometric configuration of DNA. Secondly, the effect of remote energy deposition was examined in a system consisting of gold nanotubules and free-floating DNA, containing a composition of 50 wt.% Au/50 wt.% H2O. There was no localized energy deposition due to non-conjugation and a maximum

  3. Effects of gold nanoparticle and electrode surface properties on electrocatalytic silver deposition for electrochemical DNA hybridization detection.

    PubMed

    Lee, Thomas Ming-Hung; Cai, Hong; Hsing, I-Ming

    2005-03-01

    In this paper we report the catalytic effects of various gold nanoparticles for silver electrodeposition on indium tin oxide (ITO)-based electrodes, and successfully apply this methodology for signal amplification of the hybridization assay. The most widely used gold nanoparticle-based hybridization indicators all promote silver electrodeposition on the bare ITO electrodes, with decreasing catalytic capability in order of 10 nm gold, DNA probe-10 nm gold conjugate, streptavidin-5 nm gold, and streptavidin-10 nm gold. Of greater importance, these electrocatalytic characteristics are affected by any surface modifications of the electrode surfaces. This is illustrated by coating the ITO with an electroconducting polymer, poly(2-aminobenzoic acid)(PABA), as well as avidin molecules, which are promising immobilization platforms for DNA biosensors. The catalytic silver electrodeposition of the gold nanoparticles on the PABA-coated ITO surfaces resembles that on the bare surfaces. With avidin covalently bound to the PABA, it is interesting to note that the changes in electrocatalytic performance vary for different types of gold nanoparticles. For the streptavidin-5 nm gold, the silver electrodeposition profile is unaffected by the presence of the avidin layer, whereas for both the 10 nm Au and DNA probe-10 nm gold conjugate, the deposition profiles are suppressed. The streptavidin-5 nm gold is employed as the hybridization indicator, with avidin-modified (via PABA) ITO electrode as the immobilization platform, to enable signal amplification by the silver electrodeposition process. Under the conditions, this detection strategy offers a signal-to-noise ratio of 20. We believe that this protocol has great potential for simple, reproducible, highly selective and sensitive DNA detection on fully integrated microdevices in clinical diagnostics and environmental monitoring applications.

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

    PubMed

    Park, Sung Yong; Stroud, D

    2005-06-03

    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.

  5. Molecularly resolved images of peptide-functionalized gold surfaces by scanning tunneling microscopy.

    PubMed

    Raigoza, Annette F; Webb, Lauren J

    2012-11-28

    Peptide-terminated monolayers were formed through a Huisgen cycloaddition reaction between an α-helical peptide containing two propargylglycine unnatural functional groups 20 Å apart and an alkanethiol self-assembled monolayer (SAM) on a gold surface containing 25% surface density of reactive azide terminal groups. The azide- and peptide-terminated surfaces were imaged by scanning tunneling microscopy (STM) using a low tunneling current of 10 pA. On the peptide-terminated surface, oblong features ~30 Å long and ~20 Å wide were observed and attributed to individual surface-bound α-helical peptides oriented parallel to the gold surface. These features covered an area of the surface corresponding to a density of 0.11 ± 0.01 peptides nm(-2), compared with a theoretical density of ~0.14 peptides nm(-2) for a fully reacted surface. Finally, no evidence of peptide aggregation was observed on either short (<10 nm) or long (~100 nm) length scales.

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

    PubMed Central

    Wei, Mingjie; Wang, Yong

    2015-01-01

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

  7. Investigation of maximum optical enhancement in single gold nanowires and triple nanowire arrays

    NASA Astrophysics Data System (ADS)

    Saylor, Cameron; Novak, Eric; Debu, Desalegn; Herzog, Joseph B.

    2015-01-01

    This work thoroughly investigates gold nanowires with various cross-sectional geometries and patterns. The study has determined the effect of the cross section aspect ratio on its maximum optical enhancement. The plasmonic optical enhancement properties of single gold nanowires and an array of three nanowires were investigated using finite element method simulations. The results indicate a significant dependence of the optical enhancement on both the thickness and width of the nanowires. From the simulation data, an equation for each geometry (single and triple array) was found that relates the dimensions and incident wavelength to the optical enhancement. These relationships can be a valuable resource while designing nanowires to optimize the dimensions and provide the maximum possible optical enhancement.

  8. 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.

  9. 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).

  10. 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.

  11. Surface mediated assembly of small, metastable gold nanoclusters

    NASA Astrophysics Data System (ADS)

    Pettibone, John M.; Osborn, William A.; Rykaczewski, Konrad; Talin, A. Alec; Bonevich, John E.; Hudgens, Jeffrey W.; Allendorf, Mark D.

    2013-06-01

    The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The films exhibit distinct structure from Au nanoparticles observed by X-ray diffraction, and film dissolution data support the preservation of small nanoclusters. UV-Vis spectroscopy, electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and electron microscopy are used to elucidate information regarding the nanocluster formation and assembly mechanism. Preferential deposition of nanocluster assemblies can be achieved on multiple substrates, including polymer, Cr, Si, SiO2, SiNx, and metal-organic frameworks (MOFs). Unlike other vapor phase coating processes, nanocluster assembly on the MIL-68(In) MOF crystal is capable of preferentially coating the external surface and stabilizing the crystal structure in hydrothermal conditions, which should enhance their storage, separation and delivery capabilities.The unique properties of metallic nanoclusters are attractive for numerous commercial and industrial applications but are generally less stable than nanocrystals. Thus, developing methodologies for stabilizing nanoclusters and retaining their enhanced functionality is of great interest. We report the assembly of PPh3-protected Au9 clusters from a heterogeneous mixture into films consisting of sub 3 nm nanocluster assemblies. The depositing nanoclusters are metastable in solution, but the resulting nanocluster assemblies are stabilized indefinitely in air or fresh solvent. The

  12. 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.

  13. pH effect on protein G orientation on gold surfaces and characterization of adsorption thermodynamics.

    PubMed

    Johnson, Blake N; Mutharasan, Raj

    2012-05-01

    The pH effect on adsorbed antibody-binding protein (protein G) orientation on gold (Au) and its adsorption thermodynamic characteristics were investigated using quartz crystal microbalance (QCM) and X-ray photoelectron spectroscopy (XPS). The adsorbed protein G orientation was measured by binding response of two antibody-antigen systems: the model bovine serum albumin (BSA) and the foodborne pathogen E. coli O157:H7. Surface coverage was not significantly affected by pH, but its orientation was. The most properly oriented protein G for antibody binding was achieved at near-neutral pH. Adsorption was verified by XPS measurements using nitrogen (N) 1s, oxygen (O) 1s, and Au 4p peak heights. Adsorption energetics were determined by van't Hoff and Langmuir kinetic analyses of adsorption data obtained at 296, 303, and 308 K. Large characteristic entropy change of protein adsorption was observed (ΔS° = 0.52 ± 0.01 kcal/mol·K). The adsorption process was not classical physisorption but exhibited chemisorption characteristics based on significant enthalpy change (ΔH° = -25 ± 6 kcal/mol).

  14. Multiple Surface Plasmon Modes for a Colloidal Solution of Nanoporous Gold Nanorods and Their Comparison to Smooth Gold Nanorods

    SciTech Connect

    Bok, Hye-Mi; Shuford, Kevin L; Kim, Sungwan; Kim, Seong Kyu; Park, Sungho

    2008-01-01

    The paper represents a novel approach to investigating localized surface plasmon (LSP) resonance modes of nanoporous Au nanorods (NRs) in a solution phase with control over surface morphology. Au NRs, which have distinctive features such as nanopores and ligaments, showed interesting LSP resonance modes depending on the surface morphology and the total length of the structure. Compared with the analogous smooth surface NRs, the LSP modes of nanoporous NRs are red-shifted, which can be interpreted as a longer effective rod length and larger amplitude of plasmon oscillation.

  15. Study of Molecular Trapping by Gold Nanofinger Arrays on Surface-Enhanced Raman Substrates

    DTIC Science & Technology

    2011-01-21

    Study of Molecular Trapping by Gold Nanofinger Arrays on Surface- Enhanced Raman Substrates Ansoon Kim, Fung Suong Ou...Enhanced Raman Substrates Ansoon Kim1, Fung Suong Ou1, Douglas A.A. Ohlberg2, Min Hu1, R. Stanley Williams2, Zhiyong Li1* 1Intelligent...P.; Hommer, M. B.; Jackson, M. A.; Smith, P. C.; Walter , D. G., Science 1995, 267, 1629. 11. Lindau, I.; Pianetta, P.; Yu, K. Y.; Spicer, W. E

  16. 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.

  17. Evidence for surface plasmons in a liquid crystal containing gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Tiwari, Kunal; Singh, Ankit K.; Sharma, Suresh C.

    2012-12-01

    We present evidence for surface plasmons (SPs) in a nematic liquid crystal (LC) containing dispersion of gold nanoparticles (Au NPs). The evidence originates from observations of attenuated total reflection (ATR) of p-polarized laser incident upon a high-index prism/LC-Au NPs/glass structure. We argue that SPs are generated through evanescent waves interacting with Au NPs embedded in the LC and NPs' dispersing medium.

  18. Sensitive surface plasmon resonance enabled by templated periodic arrays of gold nanodonuts

    NASA Astrophysics Data System (ADS)

    Dou, Xuan; Lin, Yuh-Chieh; Choi, Baeck; Wu, Kedi; Jiang, Peng

    2016-05-01

    Here we report a simple and scalable colloidal lithography technology for fabricating periodic arrays of gold nanodonuts for sensitive surface plasmon resonance (SPR) analysis. This new bottom-up approach leverages a unique polymer wetting layer between a self-assembled, non-close-packed monolayer silica colloidal crystal and a silicon substrate to template ordered gold nanodonuts with tunable geometries over wafer-sized areas. The processes involved in this templating nanofabrication approach, including spin coating, oxygen plasma etching, and metal sputtering, are all compatible with standard microfabrication technologies. Specular reflection measurements reveal that the efficient electromagnetic coupling of the incident light with the tunable SPR modes of the templated gold nanodonut arrays enables good spectral tunability. Bulk refractive index sensing experiments show that a high SPR sensitivity of ∼758 nm per refractive index unit, which outperforms many plasmonic nanostructures fabricated by both top-down and bottom-up approaches, can be achieved using the templated gold nanodonut arrays. Numerical finite-difference time-domain simulations have also been performed to complement the optical characterization and the theoretical results match well with the experimental measurements.

  19. Conducting polymer-gold co-patterned surfaces via nanosphere lithography.

    PubMed

    Tiu, Brylee David B; Pernites, Roderick B; Foster, Edward L; Advincula, Rigoberto C

    2015-12-01

    Co-patterned arrays comprised of conjugated polymers and nanostructured gold is an important matrix for sensing and stimuli-responsive plasmonic applications. Nanosphere lithography (NSL) is an easy-to-use patterning technique and viable method to fabricate inverse honeycomb structures with electrochemically deposited conjugated polymers. The cross-sectional height of the conducting polymer pattern can be tuned such that the macropores of the honeycomb structure expose electrochemically accessible areas for further gold deposition. Using time-dependent electrochemical reduction, Au(3+) is reduced to Au(0) and selectively deposit on the macropores thus forming a co-patterned surface. The Langmuir-Blodgett-like deposition was used to assemble polystyrene spheres on a conductive substrate. Then the carbazole-based monomer was electropolymerized within the interstices of the colloidal template, which was subsequently dissolved. A potentiostatic technique was used to deposit Au in the macropores. Fabrication of the polycarbazole-Au co-patterned surface was characterized by atomic force microscopy (AFM), electrochemical quartz crystal microbalance (EC-QCM), and X-ray photoelectron spectroscopy (XPS). Surface plasmon resonance spectroscopy (SPS) data supported backfilling behavior and quantified the complex refractive index of the array. UV-Vis absorption spectroscopy shows overlapping polycarbazole and gold LSPR peaks useful for plasmonic sensing applications. The colloidal templating approach reported in this study was further used in the fabrication of highly ordered Au nanodisks. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. 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.

  1. 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.

  2. Layer-by-layer assembly surface modified microbial biomass for enhancing biorecovery of secondary gold.

    PubMed

    Zhou, Ying; Zhu, Nengwu; Kang, Naixin; Cao, Yanlan; Shi, Chaohong; Wu, Pingxiao; Dang, Zhi; Zhang, Xiaoping; Qin, Benqian

    2017-02-01

    Enhancement of the biosorption capacity for gold is highly desirable for the biorecovery of secondary gold resources. In this study, polyethylenimine (PEI) was grafted on Shewanella haliotis surface through layer-by-layer assembly approach so as to improve the biosorption capacity of Au(III). Results showed that the relative contribution of amino group to the biosorption of Au(III) was the largest one (about 44%). After successful grafting 1, 2 and 3-layer PEI on the surface of biomass, the biosorption capacity significantly enhanced from 143.8mg/g to 597.1, 559.1, and 536.8mg/g, respectively. Interestingly, the biomass modified with 1-layer PEI exhibited 4.2 times higher biosorption capacity than the untreated control. When 1-layer modified biomass was subjected to optimizing the various conditions by response surface methodology, the theoretical maximum adsorption capacity could reach up to 727.3mg/g. All findings demonstrated that PEI modified S. haliotis was effective for enhancing gold biorecovery. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. 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.

  4. Sign-inverted surface stress-charge response in nanoporous gold

    NASA Astrophysics Data System (ADS)

    Jin, Hai-Jun; Parida, Smrutiranjan; Kramer, Dominik; Weissmüller, Jörg

    2008-12-01

    The surface stress-charge coefficient, ς, quantifies the response of the surface stress - a fundamental property of solid surfaces - to the addition or removal of superficial electric charge. So far, all experiments have found ς negative at clean metal surfaces. Here we report in situ dilatometry experiments on nanoporous gold samples prepared by dealloying. The results reveal a large reversible elastic contraction during the anodic part of cyclic potential scans. The behavior, which indicates an abnormal positive sign of ς, can be linked to a monolayer of strongly adsorbed oxygen formed during dealloying, and to the extraordinarily small (1-2 nm) structure scale of the material while the oxide is in place. After cathodic reduction, ς reverts to the conventional, negative sign of the clean metal surface. We discuss the sign of ς in relation to the electronic screening at metallic and oxide-covered surfaces.

  5. Facile in situ characterization of gold nanoparticles on electrode surfaces by electrochemical techniques: average size, number density and morphology determination.

    PubMed

    Wang, Ying; Laborda, Eduardo; Salter, Chris; Crossley, Alison; Compton, Richard G

    2012-10-21

    A fast and cheap in situ approach is presented for the characterization of gold nanoparticles from electrochemical experiments. The average size and number of nanoparticles deposited on a glassy carbon electrode are determined from the values of the total surface area and amount of gold obtained by lead underpotential deposition and by stripping of gold in hydrochloric acid solution, respectively. The morphology of the nanoparticle surface can also be analyzed from the "fingerprint" in lead deposition/stripping experiments. The method is tested through the study of gold nanoparticles deposited on a glassy carbon substrate by seed-mediated growth method which enables an easy control of the nanoparticle size. The procedure is also applied to the characterization of supplied gold nanoparticles. The results are in satisfactory agreement with those obtained via scanning electron microscopy.

  6. 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

  7. Band bending at copper and gold interfaces with ferroelectric Pb(Zr,Ti)O3 investigated by photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Apostol, Nicoleta G.; Ştoflea, Laura E.; Tănase, Liviu C.; Bucur, Ioana Cristina; Chirilă, Cristina; Negrea, Raluca F.; Teodorescu, Cristian M.

    2015-11-01

    Interfaces formed by gold and copper on single crystal layers of (0 0 1) PbZr0.2Ti0.8O3 (PZT) produced by pulsed laser deposition and exhibiting outwards polarization are analyzed by X-ray photoelectron spectroscopy. The stoichiometry of the layers reproduces reasonably that of the PZT target. The band bending occurring at the interface between PZT and the metals is investigated by analyzing the core level shifts as function on the metal deposition. It is found that for Au/PZT(0 0 1) the gold layer is not continuous and the observed band bendings can be attributed to a Schottky mechanism, whereas for Cu/PZT(0 0 1) the copper layer is continuous; in this latter case, the observed band bendings towards higher energies (lower binding energies) can be attributed to a concomitant bending due to the Schottky effect together with the disappearance of the initial bending due to the outwards polarization of the samples. Metal Pb is observed to segregate only in the case of Cu/PZT(0 0 1), therefore the surface self-reduction might also be connected to the presence of a metal with lower work function, which for larger coverage forms a continuous metal layer, able to provide electrons to the surface. High resolution transmission electron spectroscopy yielded the disappearance of the tetragonal distortion in the case of Cu/PZT(0 0 1), in line with the assumption of disappearance of the polarization-induced band bending.

  8. Phosphane-stabilized gold clusters: investigation of the stability of [Au(13)(PMe (2)Ph) (10)Cl (2)] (3+).

    PubMed

    Li, Jia; Wang, Shu-Guang

    2010-03-01

    The phosphane-stabilized gold cluster [Au(13)(PMe(2)Ph)(10)Cl(2)](3+) was studied using density functional theory. The extraordinary stability of the cluster has been attributed to the stability of the gold core and the protection conferred by ligands. Here, five stability factors of the gold core were explained and verified by investigating the Au (13) (5+) core in detail. Interactions between the gold core and several PR(3) ligands (R = Me, H, I, Br, Cl, F) were investigated according to the different electron donor abilities of each ligand; bonding energy between the ligand and the gold core was found to increase with the electronegativity of the R substituent. Furthermore, two other aspects of the ligands were clarified: how the ligand stabilizes the Au (13) (5+) core, and which kind of ligand provides the best stabilization for the cluster.

  9. 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.

  10. Chitosan-ceramide coating on gold nanorod to improve its physiological stability and reduce the lipid surface-related toxicity.

    PubMed

    Battogtokh, Gantumur; Gotov, Oyuntuya; Ko, Young Tag

    2017-03-01

    Gold nanoparticles are promising materials for many applications that include imaging, drug delivery, and photothermal therapy. However, AuNPs can be unstable and/or toxic. We purposed to improve the stability and reduce toxicity of gold nanorods (AuNR) upon coating with biocompatible polymer, chitosan-ceramide (CS-CE), without replacing the original layer, CTAB. CS-CE-coated AuNR was prepared by simple mixing for 24 h and purified by centrifugation. The coating was confirmed by UV-Vis absorption analysis and surface charge and size measurement. We prepared nanorods with CS or CS-CE coating at two different concentrations (5 and 10% AuNR), the resulting in larger nanorods with a more positive surface-charge than that of AuNR. We investigated the UV-absorption and protein adsorption of the polymer coated nanorods. Based on the protein adsorption, AuNR-CS-CE was found to be more stable under physiological conditions than AuNR-CS. The cell internalization assay revealed that Hela cells internalized higher amounts of AuNR-CS-CE than that of AuNR-CS. Cytotoxicity study revealed that AuNR-CS-CE has lower toxicity than AuNR against HeLa cells. The CS-CE coating improved the stability of AuNR under physiological conditions via the hydrophobic interactions between the AuNR lipid surface and the ceramide anchor in the CS backbone as well as.

  11. 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.

  12. 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.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

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

    PubMed

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

    DOE PAGES

    Padmos, J. Daniel; Personick, Michelle L.; Tang, Qing; ...

    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

  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

    PubMed Central

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

    2015-01-01

    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. PMID:26153854

  19. 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

    2014-11-07

    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.

  20. Investigating the extrinsic size effect of palladium and gold spherical nanoparticles

    NASA Astrophysics Data System (ADS)

    Rashidian Vaziri, M. R.; Omidvar, A.; Jaleh, B.; Partovi Shabestari, N.

    2017-02-01

    In many optical applications, knowing the variations of the plasmonic resonance wavelengths of a special kind of nanoparticles in terms of their size before the experiment began, can assist the users in selection of an appropriate preparation method for the optimum functionality. In this work, in order to show the role of the preparation method on the mean size and the size distribution of nanoparticles, two different chemical bottom-up and physical top-down methods were used for the synthesis of palladium and gold nanoparticles. Chemical reduction of metal salt and laser ablation in liquid media methods were respectively used for preparation of palladium and gold nanoparticles. It is shown that the chemical bottom-up method results in the formation of smaller particles with narrower size distribution. Optical properties and plasmonic resonance absorption of the prepared nanoparticles were investigated by UV-vis spectroscopy and their size distribution were determined by transmission electron microscopy (TEM) images. Using the measured size distribution of nanoparticles, their optical extinctions are modelled using the Mie theory of scattering. A comprehensive study on the extrinsic size effect of palladium and gold nanoparticles is performed and the dipolar and the quadrupolar Mie resonances in these nanoparticles are investigated in details. The reported results can be used for selecting the preparation method of these nanoparticles and for choosing the appropriate laser wavelength to excite stronger or weaker Mie resonances for specific applications.

  1. 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.

  2. Microchemical investigation of Greek and Roman silver and gold plated coins: coating techniques and corrosion mechanisms

    NASA Astrophysics Data System (ADS)

    Ingo, G. M.; Balbi, S.; de Caro, T.; Fragalà, I.; Riccucci, C.; Bultrini, G.

    2006-06-01

    Within the framework of a project financially supported by the European Commission (contract Nr. 509126, acronym PROMET) the metallurgical techniques used by Romans and Greeks for coating the copper core of coins with a thin or thick layer of gold or silver are studied by means of the combined use of scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS) and optical microscopy (OM) techniques. This approach is utilised to gain further insight into the micro-chemical structure of the external regions of the coins as well as into the bulk metallurgical features. The results indicate that several methods were used by the Greek and Roman craftsmen including the mechanical application of a thin malleable gold or silver foils to be welded via thermal treatment. The analytical approach is also used for investigating the corrosion products grown on the coins during the long-term burial and for identifying degradation mechanisms.

  3. Surface oxidation of gold nanoparticles supported on a glassy carbon electrode in sulphuric acid medium: contrasts with the behaviour of 'macro' gold.

    PubMed

    Wang, Ying; Laborda, Eduardo; Crossley, Alison; Compton, Richard G

    2013-03-07

    Consecutive electro-oxidation and reduction cycling of gold macroelectrodes in sulphuric acid medium is a widely-used cleaning and calibration procedure. In this paper this method is applied to electrodeposited nanoparticles revealing significant differences in the electro-oxidation process and the cleaning effectiveness. This suggests a higher density of surface defects on the nanoparticles.

  4. New insights into colloidal gold flakes: structural investigation, micro-ellipsometry and thinning procedure towards ultrathin monocrystalline layers

    NASA Astrophysics Data System (ADS)

    Hoffmann, B.; Bashouti, M. Y.; Feichtner, T.; Mačković, M.; Dieker, C.; Salaheldin, A. M.; Richter, P.; Gordan, O. D.; Zahn, D. R. T.; Spiecker, E.; Christiansen, S.

    2016-02-01

    High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 μm and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake {111} surfaces which have been found to not interfere with the presented nanopatterning. Micro-Ellipsometry was carried out to determine the complex dielectric function and to compare it to previous measurements of bulk single crystalline gold. Finally, we used focused ion beam milling to prepare smooth crystalline layers and high-quality nanostructures with desired thickness down to 10 nm to demonstrate the outstanding properties of the flakes. Our findings support the plasmonics and nano optics community with a better understanding of this material which is ideally suited for superior plasmonic nanostructures.High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 μm and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake {111} surfaces which have

  5. 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.

  6. Finite-temperature properties of ultra-thin lead films on gold (110) surfaces

    NASA Astrophysics Data System (ADS)

    De'Bell, K.; Imeson, D.

    1997-07-01

    At low coverages, lead adatoms form a single layer on the gold (110) surface. However, if a critical coverage 0953-8984/9/27/005/img1 is exceeded, a second adlayer forms. At zero temperature, various properties such as the energy and atomic spacing of atoms in the first adlayer are discontinuous at 0953-8984/9/27/005/img1. The effects of temperature on the discontinuities and location of 0953-8984/9/27/005/img1 are reported. Results for clean Au(110) and Pb(110) surfaces are also reported.

  7. Signal enhancement of surface plasmon resonance based on gold nanoparticle-antibody complex for immunoassay.

    PubMed

    Lee, Woochang; Oh, Byung-Keun; Kim, Yong-Wan; Choi, Jeong-Woo

    2006-11-01

    In the immunoassay based on surface plasmon resonance (SPR) system, the signal enhancement was done by means of the conjugate of gold (Au) nanoparticle-antibody fragment. Antibody fragment was prepared for the improved immobilization based on Au-thiol interaction. Through the ellipsometric analysis on surface, the conjugation between Au and antibody fragment was performed in the oriented manner. The optimal fabrication conditions such as concentration and incubation time were determined for the constant size of the fabricated nanoparticle-antibody conjugate. Through the plot of SPR angle difference versus antigen concentration, the linear correlation was achieved, of which the detection limit was 100 fg/ml.

  8. Surface two-level state dissipation in single-crystalline gold nanomechanical resonators

    NASA Astrophysics Data System (ADS)

    Kim, Minjin; Kim, Jihwan; Kim, Jinhee; Shim, Seung-Bo; Kim, Bongsoo; Suh, Junho

    2017-02-01

    We study the intrinsic dissipation in nanomechanical resonators fabricated with synthetic singlecrystalline gold nanowires. Contrary to the etched nanostructures, the measured resonance frequencies and damping rates unambiguously demonstrate temperature dependence, as predicted by the standard two-level tunneling-state (TLS) theory. We compare the data to a model assuming a thin amorphous layer on the nanowire surface. The deduced TLS parameters are consistent with bulk poly(methyl methacrylate) (PMMA) data, confirming the presence of residual PMMA on the surface as the TLS host.

  9. Multimodal plasmon coupling in low symmetry gold nanoparticle pairs detected in surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Dreaden, Erik C.; Near, Rachel D.; Abdallah, Tamer; Talaat, M. Hassan; El-Sayed, Mostafa A.

    2011-05-01

    We report on surface-enhanced Raman scattering of silicon phonon vibrations from arrays of gold nanoprism pairs fabricated by electron beam lithography. We found that resonant excitation of the quadrupolar surface plasmon mode of the nanoprisms increases Raman scattering intensity from the substrate as the distance between the nanoparticle pairs decreases. Finite element modeling and plasmon coupling theory indicate that symmetry is reduced as the nanoparticles approach, resulting in increased dipole-quadrupole coupling. Plasmonic enhancement of the incident and Raman-scattered photons results from the dipolar component of the mixed plasmonic field. This effect is expected to be largest in assemblies/aggregates of nanoparticles.

  10. 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.

  11. High-resolution XPS spectromicroscopy study of micro-patterned gold-tin surfaces

    NASA Astrophysics Data System (ADS)

    Renault, O.; Garnier, A.; Morin, J.; Gambacorti, N.; Bertin, F.

    2012-10-01

    We report on high-resolution chemical state mapping performed with a laboratory, spectroscopic X-ray photoelectron emission microscope (XPEEM) on electro-deposited gold-tin patterns (100 μm × 20 μm) for packaging applications of micro-systems. The analysis conditions were selected to achieve a lateral resolution below 1 μm and an energy resolution of 0.8 eV for Au4f7/2 and Sn3d5/2 for images acquired over 5 min. The chemical state maps reveal the non-uniformity of the gold/tin chemistry over regions of typical width of less than 10 μm. More precisely, the coexistence of Au and AuSn4 states, and the heterogeneity of Sn oxidation were shown. The results evidence the role of the partial delamination of the photo-resist during the electro-deposition of tin due to degraded adhesion properties on gold. These conclusions are drawn from direct inspection of the raw image data sets, and are supported by statistical treatments using Principal Component Analysis (PCA). This is a clear example of the interest in using high resolution XPS imaging by XPEEM at a practical level in applied surface science, and its complementarity to other surface imaging techniques.

  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.

  13. 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.

  14. Surface Enhanced Raman Scattering (SERS) Studies of Gold and Silver Nanoparticles Prepared by Laser Ablation

    PubMed Central

    Herrera, Gloria M.; Padilla, Amira C.; Hernandez-Rivera, Samuel P.

    2013-01-01

    Gold and silver nanoparticles (NPs) were prepared in water, acetonitrile and isopropanol by laser ablation methodologies. The average characteristic (longer) size of the NPs obtained ranged from 3 to 70 nm. 4-Aminobenzebethiol (4-ABT) was chosen as the surface enhanced Raman scattering (SERS) probe molecule to determine the optimum irradiation time and the pH of aqueous synthesis of the laser ablation-based synthesis of metallic NPs. The synthesized NPs were used to evaluate their capacity as substrates for developing more analytical applications based on SERS measurements. A highly energetic material, TNT, was used as the target compound in the SERS experiments. The Raman spectra were measured with a Raman microspectrometer. The results demonstrate that gold and silver NP substrates fabricated by the methods developed show promising results for SERS-based studies and could lead to the development of micro sensors.

  15. 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.

  16. 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.

  17. Adsorption of benzoic acid, phthalic acid on gold substrates studied by surface-enhanced Raman scattering spectroscopy and density functional theory calculations.

    PubMed

    Gao, Jiao; Hu, Yongjun; Li, Shaoxin; Zhang, Yanjiao; Chen, Xue

    2013-03-01

    Benzoic acid (BA) and phthalic acid (PTA) are the simplest aromatic carboxylic acids, and they can be regarded as typical model compounds in investigating the interaction of aromatic carboxylic acids with metal surfaces by use of SERS spectroscopy. In this work, we have investigated the structure and adsorption behavior of benzoic acid and phthalic acid on the gold surface with combination of SERS and DFT calculation methods. The experimental results show that both BA and PTA may be adsorbed on the Au surface with a bidentate bridging structure, namely, the carboxylate group(s) being bound to gold via two oxygen atoms in the carboxylate group(s). Comparison of the observed SERS and predicted spectra of the complexes of these two substances with Au atoms indicates that BA is favorable to adsorb on the gold surface with a vertical orientation rather than a flat one, and PTA could "stand up" on the Au surface as a slight tilt with a two-legged geometry, i.e. all four oxygen atoms in two carboxylate groups interact on the metal surface. Apart from that, we compare the discrepancy of SERS spectra between those two molecules, which could be taken as a potential analysis technique in food safety field. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

  18. Effect of seed age on gold nanorod formation. A microfluidic, real-time investigation

    DOE PAGES

    Watt, John; Hance, Bradley G.; Anderson, Rachel S.; ...

    2015-09-02

    We report a real time investigation into the effect of seed age on the growth of gold nanorods using a microfluidic reaction apparatus. Through small-angle X-ray scattering (SAXS) and ultraviolet–visible spectroscopy (UV–vis) analysis, we observe the seeds aging in accordance with Ostwald ripening. A seed solution is then aged in situ and continuously injected into a microfluidic chip to initiate rod growth. We track nanorod formation in real time using in-line ultraviolet–visible and near-infrared (UV–vis–NIR) monitoring and observe a dramatic decrease in yield with increasing seed age. We then demonstrate that, by diluting the gold seed solution immediately following synthesis,more » the rate of aging can be reduced and nanorods synthesized continuously, in good yield. As a result, these findings suggest ultrasmall, catalytically active seeds, which are rapidly lost due to ripening and are critical for the formation of gold nanorods.« less

  19. Investigation of Sub-100 nm Gold Nanoparticles for Laser-Induced Thermotherapy of Cancer

    PubMed Central

    Leung, Jennifer P.; Wu, Sherry; Chou, Keng C.; Signorell, Ruth

    2013-01-01

    Specialized gold nanostructures are of interest for the development of alternative treatment methods in medicine. Photothermal therapy combined with gene therapy that supports hyperthermia is proposed as a novel multimodal treatment method for prostate cancer. In this work, photothermal therapy using small (<100 nm) gold nanoparticles and near-infrared (NIR) laser irradiation combined with gene therapy targeting heat shock protein (HSP) 27 was investigated. A series of nanoparticles: nanoshells, nanorods, core-corona nanoparticles and hollow nanoshells, were synthesized and examined to compare their properties and suitability as photothermal agents. In vitro cellular uptake studies of the nanoparticles into prostate cancer cell lines were performed using light scattering microscopy to provide three-dimensional (3D) imaging. Small gold nanoshells (40 nm) displayed the greatest cellular uptake of the nanoparticles studied and were used in photothermal studies. Photothermal treatment of the cancer cell lines with laser irradiation at 800 nm at 4 W on a spot size of 4 mm (FWHM) for 6 or 10 min resulted in an increase in temperature of ~12 °C and decrease in cell viability of up to 70%. However, in vitro studies combining photothermal therapy with gene therapy targeting HSP27 did not result in additional sensitization of the prostate cancer cells to hyperthermia.

  20. Light wavelength influence on surface plasmon resonance in citrate-gold nanosystems

    NASA Astrophysics Data System (ADS)

    Lupusoru, Raoul-Vasile; Pricop, Daniela A.; Andries, Maria; Creanga, Dorina

    2016-12-01

    Citrate-gold particles were yielded according to classical method of auric salt reduction in two different synthesis media aiming to use them further applications in biomedical and environmental domains. The analysis of citrate-gold interaction was done through UV-vis and IR spectroscopy as well as by Transmission Electron Microscopy (TEM) and Dark Field (DF) Microscopy. Average particle size was higher for citrate-gold NPs synthesized with NaOH (32.5 nm) than for NPs synthesized with NaCl (15 nm). Dimensional histograms of one year aged colloidal suspensions presented mean size of 29 nm and respectively 18 nm. The influence of 90 min light exposure, analyzed by UV-vis, evidenced that for both NaOH synthesis protocol and NaCl protocol, plasmon band maxima at 528 nm and respectively 538 nm didn't changed, neither for white nor for green light. For one year aged samples this band shifted to 540 nm for green light irradiation in the case of citrate-gold NPs synthesized with NaOH. Also, for these NPs, both green and white light exposures resulted in plasmon band intensity changes for native as well as for aged samples. FTIR investigation showed also different changes at the level of the intensity of main vibration bands of citrate-gold after exposure to light, suggesting stronger adsorption of citrate in the case of NaCl addition in the initial reaction medium than in the case of NaOH. Finally, the utilization of NaCl in the synthesis protocol seems to favor the synthesis of more stable and lower toxicity colloidal suspensions, both during time and under the light irradiation.

  1. Luminescent gold surfaces for sensing and imaging: patterning of transition metal probes.

    PubMed

    Adams, Samuel J; Lewis, David J; Preece, Jon A; Pikramenou, Zoe

    2014-07-23

    Luminescent transition metal complexes are introduced for the microcontact printing of optoelectronic devices. Novel ruthenium(II), RubpySS, osmium(II), OsbpySS, and cyclometalated iridium(III), IrbpySS, bipyridyl complexes with long spacers between the surface-active groups and the metal were developed to reduce the distance-dependent, nonradiative quenching pathways by the gold surface. Indeed, surface-immobilized RubpySS and IrbpySS display strong red and green luminescence, respectively, on planar gold surfaces with luminescence lifetimes of 210 ns (RubpySS·Au) and 130 and 12 ns (83%, 17%) (IrbpySS·Au). The modified surfaces show enhancement of their luminescence lifetime in comparison with solutions of the respective metal complexes, supporting the strong luminescence signal observed and introducing them as ideal inorganic probes for imaging applications. Through the technique of microcontact printing, complexes were assembled in patterns defined by the stamp. Images of the red and green patterns rendered by the RubpySS·Au and IrbpySS·Au monolayers were revealed by luminescence microscopy studies. The potential of the luminescent surfaces to respond to biomolecular recognition events is demonstrated by addition of the dominant blood-pool protein, bovine serum albumin (BSA). Upon treatment of the surface with a BSA solution, the RubpySS·Au and IrbpySS·Au monolayers display a large luminescence signal increase, which can be quantified by time-resolved measurements. The interaction of BSA was also demonstrated by surface plasmon resonance (SPR) studies of the surfaces and in solution by circular dichroism spectroscopy (CD). Overall, the assembly of arrays of designed coordination complexes using a simple and direct μ-contact printing method is demonstrated in this study and represents a general route toward the manufacture of micropatterned optoelectronic devices designed for sensing applications.

  2. Location and identification of colloidal gold particles on the cell surface with a scanning electron microscope and energy dispersive analyzer

    SciTech Connect

    Eskelinen, S.; Peura, R.

    1988-09-01

    The use of colloidal gold particles for locating cell surface components by scanning electron microscopy (SEM) has been restricted due to difficulties in the identification of these gold particles under SEM. It is shown here how the gold particles bound to cell surfaces can be located and identified under SEM using the secondary electron imaging (SEI) mode with an energy dispersive X-ray microanalyzer (EDS). This enables reliable identification of gold particles and good quality micrographs of the cells to be achieved at the same time. The distribution of receptors for two lectins, concanavalin A (ConA) and wheat germ agglutinin (WGA), on the surface of cultured Raji cells and human erythrocytes is presented as an example. Raji cells and erythrocytes were fixed with glutaraldehyde, post-fixed with a glutaraldehyde-tannic acid mixture and then incubated with ConA- or WGA-coated gold particles. After dehydration and critical point drying, the specimen filters were mounted on copper stubs and coated with carbon. The cells were examined on a JEOL TEMSCAN 100CX II electron microscope. The gold particles could be identified with the EDS analyzer, which was able to detect the Au spectrum when the electron beam was focused on single gold particles using a magnification of 100,000 or more. High-resolution photographs of the same cells were obtained up to the same magnification of 100,000.

  3. 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.

  4. 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.

  5. 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.

  6. Nanoscale size dependence in the conjugation of amyloid beta and ovalbumin proteins on the surface of gold colloidal particles

    NASA Astrophysics Data System (ADS)

    Yokoyama, K.; Briglio, N. M.; Sri Hartati, D.; Tsang, S. M. W.; MacCormac, J. E.; Welchons, D. R.

    2008-09-01

    Absorption spectroscopy was utilized to investigate the conjugation of amyloid β protein solution (Aβ1-40) and chicken egg albumin (ovalbumin) with various sizes of gold colloidal nanoparticles for various pHs, ranging from pH 2 to pH 10. The pH value that indicates the colour change, pHo, exhibited colloidal size dependence for both Aβ1-40 and ovalbumin coated particles. In particular, Aβ1-40 coated gold colloidal particles exhibited non-continuous size dependence peaking at 40 and 80 nm, implying that their corresponding cage-like structures provide efficient net charge cancellation at these core sizes. Remarkably, only the pHo value for ovalbumin coated 80 nm gold colloid was pH>7, and a specific cage-like structure is speculated to have a positive net charge facing outward when ovalbumin self-assembles over this particular gold colloid. The previously reported reversible colour change between pH 4 and 10 took place only with Aβ1-40 coated 20 nm gold colloids; this was also explored with ovalbumin coated gold colloids. Interestingly, gold colloidal nanoparticles showed a quasi-reversible colour change when they were coated with ovalbumin for all test sizes. The ovalbumin coated gold colloid was found to maintain reversible properties longer than Aβ1-40 coated gold colloid.

  7. 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.

  8. SERS characterization of neuropeptide Y and its C-terminal fragments deposited onto colloidal gold nanoparticle surface.

    PubMed

    Domin, Helena; Piergies, Natalia; Święch, Dominika; Pięta, Ewa; Proniewicz, Edyta

    2017-01-01

    It has been suggested that the family of neuropeptide Y (NPY) peptides is a promising target for the neuroprotective therapy; therefore, knowledge of the structure of these biologically active compounds and their behavior at solid/liquid interface is important in order to design new analogues. Because there is still a lack of detailed information on the behavior of NPY and its mutated analogues at the solid/liquid interfaces, in this work surface-enhanced Raman spectroscopy (SERS) analysis was used to investigate NPY and its native NPY(3-36), NPY(13-36), and NPY(22-36) and mutated acetyl-(Leu(28,31))-NPY(24-36)C-terminal fragments, acting on Y2 receptors (Y2R), in order to determine their possible metal surface/molecule interactions. In these studies, colloidal gold nanoparticle surface served as a solid surface, whereas an aqueous solution was used as a liquid medium. The observed differences in the band intensities, wavenumbers, and widths allowed us to draw conclusions on an adsorption mode of NPY and on changes in this mode upon the shortening of the peptide chain and increase in solution pH (from pH 3 to pH 11). Briefly, three different species of Tyr were identified onto the colloidal gold surface depending upon the length of the peptide chain and solution pH. Tyrosine (TyrOH) is present in a basic medium. Tyrosinate (TyrO(-)) is present in an acidic solution, whereas phenoxyl radical (Tyr(*)) appears at neutral pH for peptides having relatively short peptide chain (acetyl-(Leu(28,31))-NPY(24-36)). The elongation of the peptide chain partially (NPY(13-36) and NPY(22-36)) or completely (NPY(3-36) and NPY) protects the Tyr residue against conversion to the radical form. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Functionalization of gold and graphene electrodes by p-maleimido-phenyl towards thiol-sensing systems investigated by EQCM and IR ellipsometric spectroscopy

    NASA Astrophysics Data System (ADS)

    Neubert, Tilmann Joachim; Rösicke, Felix; Sun, Guoguang; Janietz, Silvia; Gluba, Marc A.; Hinrichs, Karsten; Nickel, Norbert H.; Rappich, Jörg

    2017-01-01

    Electrografting of gold and graphene surfaces by functional p-(N-maleimido)phenyl groups was performed by reduction of p-(N-maleimido)phenyldiazonium tetrafluoroborate. The reduction was carried out using cyclo voltammetry coupled with micro-gravimetric measurements by means of electrochemical quartz crystal microbalance (EQCM). The overall deposited mass on gold was higher than on graphene. However, the Faradaic efficiency was lower on Au (14%) compared to graphene (22%) after the first potential scan. Subsequently, the maleimide functional groups have been tested for immobilization of terminal thiols using 2-(4-nitrobenzene)-ethane-thiol for the functionalized graphene surface and a cysteine-modified peptide for the functionalized gold surface. The functionalization by p-(N-maleimido)phenyl groups and the following thiol coupling of the particular surface was proven by infrared spectroscopic ellipsometry (IRSE). In addition, the interaction of the tetrabutylammonium and tetrafluoroborate ions present in the electrolyte with the Au and graphene electrodes was investigated by EQCM and revealed less electrostatic interaction of graphene with these ions in solution compared to the metal (Au) surface.

  10. New insights into colloidal gold flakes: structural investigation, micro-ellipsometry and thinning procedure towards ultrathin monocrystalline layers.

    PubMed

    Hoffmann, B; Bashouti, M Y; Feichtner, T; Mačković, M; Dieker, C; Salaheldin, A M; Richter, P; Gordan, O D; Zahn, D R T; Spiecker, E; Christiansen, S

    2016-02-28

    High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 μm and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake {111} surfaces which have been found to not interfere with the presented nanopatterning. Micro-Ellipsometry was carried out to determine the complex dielectric function and to compare it to previous measurements of bulk single crystalline gold. Finally, we used focused ion beam milling to prepare smooth crystalline layers and high-quality nanostructures with desired thickness down to 10 nm to demonstrate the outstanding properties of the flakes. Our findings support the plasmonics and nano optics community with a better understanding of this material which is ideally suited for superior plasmonic nanostructures.

  11. 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.

  12. Controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes.

    PubMed

    Kumar, Suresh; Kaur, Inderpreet; Dharamvir, Keya; Bharadwaj, Lalit M

    2012-03-01

    A facile method for controlling the density and site of attachment of gold nanoparticles onto the surface of carbon nanotubes is demonstrated. Nitric acid based oxidation was carried out to create carboxylic groups exclusively at the ends of carbon nanotubes, whereas oxidation using a mixture of nitric and sulfuric acid with varied reaction time was carried out to control the population of carboxylic groups on the side walls of nanotubes. In turn, 4-aminothiophenol modified gold nanoparticles were covalently interfaced to these carboxylated multi-walled carbon nanotubes in the presence of a zero length cross-linker, 1-ethylene-3-(3-dimethylaminopropyl) carbodiimide. Raman spectroscopic results showed increase in height of disorder band with each of these successive steps, indicating the increase in degree of functionalization of the carbon nanotubes. Fourier transformed infrared spectroscopic analysis affirmed the functionalization of nanostructures and the formation of nanohybrid. Transmission electron and field emission scanning electron microscopic analysis ascertained the attachment of gold nanoparticles to the ends and side walls of the multi-walled carbon nanotubes. The new hybrid nanostructures may find applications in electronic, optoelectronic, and sensing devices.

  13. 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.

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

    SciTech Connect

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

    2016-08-14

    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.

  15. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Application of Ru(bpy) 32+ in control and formation of gold surface nanostructure through oxidation-reduction cycling

    NASA Astrophysics Data System (ADS)

    Bin, Qi; Zheng, Zhikun; Yang, Xiurong

    2007-03-01

    It was studied that the nanostructure formed on a gold surface via a simple oxidation-reduction cycles (ORC) in 0.1 M KCl containing Ru(bpy) 32+ with different concentrations. Atomic force microscopy (AFM) and energy-dispersed spectroscopy (EDS) were used to characterize the nanostructure formed on the gold surface. Sweep-step voltammetry and corresponding electroluminescence (ECL) response, in situ electrochemical quartz crystal microbalance (EQCM) measurement were used to monitor the ORC procedure. It was found that the surface structure became more uniform in the presence of Ru(bpy) 32+, and the surface roughness was decreasing with the increasing of Ru(bpy) 32+ concentration, suggesting a simple and effective method to control the formation of nanostructure on the gold surface.

  17. River dykes investigation using seismic surface waves

    NASA Astrophysics Data System (ADS)

    Bitri, Adnand; Jousset, Philippe; Samyn, Kévin; Naylor, Adam

    2010-05-01

    Natural underground caves such as karsts are quite common in the region "Centre", France. These subsurface perturbations can be found underneath the protection dykes around "the Loire" River and the damage caused can create routes for floods. Geophysical methods such as Multi-channel Analysis of Surface Waves (MASW) can be used for locating voids or karsts systems, but its efficiency on surface with strong topography such as dykes is not certain. Three dimensional Rayleigh wave modelling was used to understand the role of topography in the propagation of surface waves and with the aim of determining the best way for MASW investigations of surfaces with strong topography such as river dykes. Numerical modelling shows that surface waves propagation is not strongly affected by topography for an array parallel to the dyke. For homogeneous models with topography, a diminution of surface waves amplitude is observed while higher propagation modes are amplified in the dispersion curves in the case of heterogeneous models with topography. For an array perpendicular to the dyke, numerical modeling shows that Rayleigh waves' velocity is lower. MASW investigations can then be applied if lateral variations of the topography are not too strong along the seismic line. Diffraction hyperbolas created by a full of water cavity were identified in numerical modelling with topography. According to these elements, a MASW survey has been performed on the dykes of "the Loire" river close to a collapsed cavity and potential karstic systems were discovered.

  18. Glycine crystallization in solution by CW laser-induced microbubble on gold thin film surface.

    PubMed

    Uwada, Takayuki; Fujii, Sho; Sugiyama, Teruki; Usman, Anwar; Miura, Atsushi; Masuhara, Hiroshi; Kanaizuka, Katsuhiko; Haga, Masa-aki

    2012-03-01

    We have developed a novel laser-induced crystallization method utilizing local heat-induced bubble/water interface. Continuous laser beam of 1064 nm is focused on a gold nanoparticles thin film surface covered with glycine supersaturated aqueous solution. Light absorption of the film due to localized plasmon resonance caused local heating at the focal position and produced a single thermal vapor microbubble, which generated thermal gradient followed by convection flow around the bubble and eventually induced glycine crystallization and growth. The crystallization mechanism is discussed by considering gathering and accumulating molecules around the bubble/water interface assisted by convection flow and temperature jump.

  19. Gold-surface binding of molecular switches studied by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Homenya, Patrick; Messerschmidt, Markus; Tahir, Muhammad Nawaz; Martinez, Victor; Cheng, Yajun; Gutmann, Jochen S.; Klein, Michael; Jung, Stefan; Wolff, Morris; Saadat, Reza; Nariaki, Driss; Boča, Roman; Klingelhöfer, Göstar; Tremel, Wolfgang; Renz, Franz

    2012-03-01

    The nonanuclear coordination compound [MoIV{(CN)FeIII(3-methyl-saldptn)}8]Cl4 exhibits multiple spin transitions (3-methyl-saldptn = N,N'-bis(3''-methyl-2''-hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. Mössbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e.g. in the field of information storage) was laid.

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

    PubMed

    Austin, Lauren A; Mackey, Megan A; Dreaden, Erik C; El-Sayed, Mostafa A

    2014-07-01

    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.

  1. 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

  2. Two-photon activation of photoactive ligands bound to gold surfaces

    NASA Astrophysics Data System (ADS)

    Magill, Brenden A.; Guo, Xi; See, Erich M.; Reyes, Roberto L.; Davis, Richey M.; Santos, Webster L.; Robinson, Hans D.

    2014-03-01

    Photoactive crosslinkers are useful tools for optically driven assembly of nano-particles. We report on the use of ultra-short laser pulses to affect localized photoreactions in o-nitrobenzyl-based photoactive ligands bound to a gold surface with thiol groups. The reaction is activated through a combination of thermal activation and two-photon absorption, while at higher power densities, ligands can be ablated from the surface through breaking of the gold-thiol bond. We will present data on the interplay of these three effects as a function of laser power and exposure time, and demonstrate assembly of nanoparticles onto optically patterned surfaces. Finally, we will discuss how this effect could be used to create well-defined nanoparticle assemblies where great binding-site selectivity can be obtained through the combination of high electromagnetic intensity enhancements at plasmon hotspots and the nonlinear scaling of photoactivation efficiency in two-photon absorption processes. We acknowledge financial support from the National Science Foundation and the Institute for Critical Technology and Applied Science.

  3. Cytotoxicity of gold nanoparticles with different structures and surface-anchored chiral polymers.

    PubMed

    Deng, Jun; Yao, Mengyun; Gao, Changyou

    2017-02-15

    Nanoparticles (NPs) can have profound effects on cell biology. However, the potential adverse effects of gold nanoparticles (AuNPs) with different surface chirality and structures have not been elucidated. In this study, monolayers of poly(acryloyl-l(d)-valine (l(d)-PAV) chiral molecules were anchored on the surfaces of gold nanocubes (AuNCs) and nanooctahedras (AuNOs), respectively. The l-PAV-AuNCs and d-PAV-AuNCs, or the l-PAV-AuNOs and d-PAV-AuNOs, had identical physicochemical properties in terms of size, morphology and ligand density except of the reverse molecular chirality on the particle surfaces, respectively. The l-PAV capped AuNCs and AuNOs exhibited larger cytotoxicity to A549 cells than the D-PAV coated ones, and the PAV-AuNOs had larger cytotoxicity than PAV-AuNCs when being capped with the same type of enantiomers, respectively. The cytotoxicity was positively correlated with the cellular uptake amount, and thereby the production of intracellular reactive oxygen species (ROS).

  4. Terahertz conductivity engineering in surface decorated carbon nanotube films by gold nanoparticles.

    PubMed

    Polley, Debanjan; Patra, Animesh; Barman, Anjan; Mitra, Rajib Kumar

    2017-02-01

    We report the controllable conductivity of single-walled carbon nanotubes (SWNTs) and multiwalled carbon nanotubes with their surface walls decorated by gold nanoparticles (Au NPs) with varying concentration in terahertz (THz) frequency range. Colloidal Au NPs of nominal diameter ∼15  nm are synthesized by the reduction of gold chloride solution using tri-sodium citrate. A simple chemical route is followed to attach Au NPs on the surfaces of both types of carbon nanotubes (CNTs). The attachment of Au NPs on the sidewalls of CNTs is confirmed by UV-visible spectroscopy and scanning electron microscope images. THz spectroscopic measurements are carried out at room temperature in transmission geometry in the frequency range of 0.3-2.0 THz. It is found that the THz conductivity of the surface decorated SWNT composites can either be increased or decreased by ±15% than that of the as-prepared SWNT composites by carefully choosing the Au NP concentration. The conductivity variation is qualitatively explained in terms of carrier trapping potential for low Au NP density, and alternative carrier conduction pathways at higher Au NP density and analyzed with the help of a modified universal dielectric relaxation model.

  5. Ultra-strong surface plasmon amplification characteristic of a spaser based on gold-silver core-shell nanorods

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Zhou, Jun; Zhang, Haopeng; Jiang, Tao; Lou, Cibo

    2015-03-01

    We proposed an efficient spaser based on gold-silver core-shell nanorods (NRs) encapsulated by an outer silica shell doped with a gain medium. The optical characteristics of the spaser were numerically simulated based on the finite element method (FEM). The results showed that the localized surface plasmon resonance (LSPR) amplification characteristics of the spaser strongly depend on the thickness of silver shell, the aspect ratio of the inner gold NRs, and the polarization direction of the incident light. And, the maximum absolute value of optical cross-section of the spaser can reach 21,824 μm2, which is about 1115, 523, and 18 times higher than that of spasers based on the gold NRs, the silver NRs, and the silver-gold core-shell NRs, respectively. The ultra-strong surface plasmon amplification characteristics of the spaser have potential applications in optical information storage, high sensitivity biochemical sensing, and medical engineering.

  6. 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

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

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

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

  8. Gold-film coating assisted femtosecond laser fabrication of large-area, uniform periodic surface structures.

    PubMed

    Feng, Pin; Jiang, Lan; Li, Xin; Rong, Wenlong; Zhang, Kaihu; Cao, Qiang

    2015-02-20

    A simple, repeatable approach is proposed to fabricate large-area, uniform periodic surface structures by a femtosecond laser. 20 nm gold films are coated on semiconductor surfaces on which large-area, uniform structures are fabricated. In the case study of silicon, cross-links and broken structures of laser induced periodic surface structures (LIPSSs) are significantly reduced on Au-coated silicon. The good consistency between the scanning lines facilitates the formation of large-area, uniform LIPSSs. The diffusion of hot electrons in the Au films increases the interfacial carrier densities, which significantly enhances interfacial electron-phonon coupling. High and uniform electron density suppresses the influence of defects on the silicon and further makes the coupling field more uniform and thus reduces the impact of laser energy fluctuations, which homogenizes and stabilizes large-area LIPSSs.

  9. Nanocrystal and surface alloy properties of bimetallic Gold-Platinum nanoparticles

    PubMed Central

    Mott, Derrick; Luo, Jin; Smith, Andrew; Njoki, Peter N; Wang, Lingyan

    2007-01-01

    We report on the correlation between the nanocrystal and surface alloy properties with the bimetallic composition of gold-platinum(AuPt) nanoparticles. The fundamental understanding of whether the AuPt nanocrystal core is alloyed or phase-segregated and how the surface binding properties are correlated with the nanoscale bimetallic properties is important not only for the exploitation of catalytic activity of the nanoscale bimetallic catalysts, but also to the general exploration of the surface or interfacial reactivities of bimetallic or multimetallic nanoparticles. The AuPt nanoparticles are shown to exhibit not only single-phase alloy character in the nanocrystal, but also bimetallic alloy property on the surface. The nanocrystal and surface alloy properties are directly correlated with the bimetallic composition. The FTIR probing of CO adsorption on the bimetallic nanoparticles supported on silica reveals that the surface binding sites are dependent on the bimetallic composition. The analysis of this dependence further led to the conclusion that the relative Au-atop and Pt-atop sites for the linear CO adsorption on the nanoparticle surface are not only correlated with the bimetallic composition, but also with the electronic effect as a result of the d-band shift of Pt in the bimetallic nanocrystals, which is the first demonstration of the nanoscale core-surface property correlation for the bimetallic nanoparticles over a wide range of bimetallic composition.

  10. 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.

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

    DOE PAGES

    Chapman, Christopher A. R.; Chen, Hao; Stamou, Marianna; ...

    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

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

    PubMed Central

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

    2015-01-01

    Designing neural-electrode interfaces that maintain close physical coupling of neurons to the 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 is achieving close physical coupling of neurons through 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 of the dealloying conditions. Our results show that np-Au nanotopography, not surface chemistry, reduces astrocyte surface coverage while maintaining high neuronal coverage, and may enhance the neuron-electrode coupling through nanostructure-mediated suppression of scar tissue formation. PMID:25706691

  13. Preferential adsorption of fetal bovine serum on bare and aromatic thiol-functionalized gold surfaces in cell culture media.

    PubMed

    Park, Jin; Park, Jin-Ho; Ock, Kwang-Su; Ganbold, Erdene-Ochir; Song, Nam Woong; Cho, Keunchang; Lee, So Yeong; Joo, Sang-Woo

    2011-11-01

    Intracellular uptake of serum-coated gold nanoparticles (AuNPs) in a single mammalian cell was examined in order to investigate the interactions of cell culture media and aromatic thiol-functionalized gold surfaces using micro-spectroscopic tools. The AuNPs modified by the aromatic thiols of para-aminobenzenethiol (ABT), para-hydroxy benzenethiol (HBT), and para-carboxylic benzenethiol (CBT, para-mercaptobenzoic acid) bearing NH(2), OH, and COOH surface functional groups are presumed to adsorb the serum proteins as indicated from the compiled quartz crystal microbalance (QCM) data. The QCM results indicate that among the constituents, fetal bovine serum (FBS) should be the major adsorbate species on AuNPs incubated in Roswell Park Memorial Institute (RPMI) medium. The functionalized AuNPs were found to be internalized as an aggregation state in mammalian cells as evidenced by transmission electron microscopy (TEM) images. We monitored such cellular uptake behaviors of aromatic thiol-modified AuNPs using dark-field microscopy (DFM)-guided confocal surface-enhanced Raman scattering techniques in order to identify the three-dimensional localization inside the single cell. We found that the uptake amounts of ABT, HBT, and CBT were similar by counting up to 70 particles inside the cells incubated in the solution mixture of the aromatic thiol and 1,4-phenylenediisocyanide (PDIC) as a reference. This result indicates for the short aromatic thiol compounds, the AuNPs should enter the cell after the serum-coating regardless of the surface functional groups. Considering that the aromatic thiols have little effect on the serum coating, the DFM/SERS method is an effective tool for monitoring the localization of AuNPs inside a single cell. Copyright © 2011 Elsevier Inc. All rights reserved.

  14. Mechanistic Investigation of N-Homocysteinylation-Mediated Protein–Gold Nanoconjugate Assembly

    PubMed Central

    Gates, Arther T.; Moore, Leonard; Sylvain, Monica R.; Jones, Christina M.; Lowry, Mark; El-Zahab, Bilal; Robinson, James W.; Strongin, Robert M.; Warner, Isiah M.

    2010-01-01

    Herein we report the use of protein-gold nanoconjugate (PGNs) as probes for elucidating mechanistic events involved in protein homocystamide detection with gold nanoparticles (GNPs), as was previously reported by our laboratory. Three different PGN probes are synthesized by direct adsorption of cytochrome c, albumin, or human serum onto citrate-capped GNPs. The PGNs are subsequently purified and treated to confer N-homocysteinylation. Individual PGN systems are evaluated to assess the effect of modification on (1) surface plasmon resonance (SPR), (2) protein structural conformation, and (3) assembly-association. The degree of PGN assembly and colorimetric signal observed postmodification varies based on the type of conjugated protein. For example, results of time-resolved dynamic light scattering studies indicate that modification of cytochrome c-PGNs yields rapid formation of macroscopic nanoparticle assemblies that eventually precipitate from solution. In contrast, albumin and human serum PGNs exhibit higher stability toward modification. Additionally, findings from circular dichroism studies indicate significant modification-induced denaturation, which is what may initiate assembly via electrosteric destabilization of PGNs. The results of electrophoretic studies appear to confirm that the process of N-homocysteinylation-mediated PGN assembly culminates in covalent interparticle association by disulfide cross-linking among modified proteins. PMID:19719226

  15. Effect of gold oxide in measurements of colloidal force.

    PubMed

    Tabor, Rico F; Morfa, Anthony J; Grieser, Franz; Chan, Derek Y C; Dagastine, Raymond R

    2011-05-17

    Atomic force microscopy, contact-angle, and spectroscopic ellipsometry measurements were employed to investigate the presence and properties of gold oxide on the surface of gold metal. It was found that, in agreement with available literature, unoxidized gold surfaces were hydrophobic, whereas oxidation rendered the surface highly hydrophilic. The oxide could be removed with ethanol or base but appeared to be stable over long periods in water or salt solutions between pH 3 and 7. After oxidation, the oxide layer thickness, determined using ellipsometry, was consistent with an approximate monolayer of Au-O bonds at the gold surface. The presence of gold oxide was found to alter significantly the electrical double-layer characteristics of the gold surface below pH 6 and may explain the apparent inconsistencies in observed force behavior where gold is employed as well as aiding in design of future microfluidic systems which incorporate gold as a coating.

  16. 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.

  17. Experimental Characterization of the Order-Disorder Transition of a Gold-Rich COPPER(3)-GOLD(100) Surface

    NASA Astrophysics Data System (ADS)

    Rivers, Steven B.

    The order-disorder transition of a Au-rich Cu _3Au{001 } surface has been characterized using synchrotron x-ray scattering. Cu_3Au is a prototypical system for ordering alloys which undergo a first-order bulk phase transition. The specific bulk composition of our sample is CU_{72.1}AU _{27.9}. An important advantage of x-ray scattering is that it can be used to investigate both the bulk and the near-surface region. The disorder-to-order-transformation at the surface occurs at a temperature about 15^circ C above the bulk transition temperature as revealed by x-ray measurements. Recently Lipowsky proposed a Landau -Ginzburg type model that addresses the issue of surface -induced order and disorder. The language developed in this model is useful for describing our results. However, the Hamiltonian is not general enough to treat nonstoichiometric compositions and therefore no quantitative description is possible. Antiphase domain boundaries are found to form parallel to the surface in a long-range periodic structure. This structure produces satellites in the superstructure diffraction line shapes. We analyze this phenomenon in terms of several models including the formation of a new phase, a two-phase mixture, and the interaction between the Fermi surface and the Brillouin Zone. The time dependence of the growth of the ordered domains from 10^3 to 10 ^5 seconds was investigated through the measurement of the superstructure beam profile following a quench from the disordered state to final temperatures below both the surface and bulk transition temperatures. Quenches to temperatures below the surface transition temperature resulted in power law growth. However, quenches below the bulk transition temperature resulted in domain growth that could not be described by a power law even for the longest times studied. In both cases the kinetics of the domain growth was substantially slower than that previously reported for the bulk, which is known to follow a power law with a

  18. 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.

  19. 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.

  20. A micro GC detector array based on chemiresistors employing various surface functionalized monolayer-protected gold nanoparticles.

    PubMed

    Jian, Rih-Sheng; Huang, Rui-Xuan; Lu, Chia-Jung

    2012-01-15

    Aspects of the design, fabrication, and characterization of a chemiresistor type of microdetector for use in conjunction with gas chromatograph are described. The detector was manufactured on silicon chips using microelectromechanical systems (MEMS) technology. Detection was based on measuring changes in resistance across a film comprised of monolayer-protected gold nanoclusters (MPCs). When chromatographic separated molecules entered the detector cell, the MPC film absorbed vapor and undergoes swelling, then the resistance changes accordingly. Thiolates were used as ligand shells to encapsulate the nano-gold core and to manipulate the selectivity of the detector array. The dimensions of the μ-detector array were 14(L)×3.9(W)×1.2(H)mm. Mixtures of eight volatile organic compounds with different functional groups and volatility were tested to characterize the selectivity of the μ-detector array. The detector responses were rapid, reversible, and linear for all of the tested compounds. The detection limits ranged from 2 to 111ng, and were related to both the compound volatility and the selectivity of the surface ligands on the gold nanoparticles. Design and operation parameters such as flow rate, detector temperature, and width of the micro-fluidic channel were investigated. Reduction of the detector temperature resulted in improved sensitivity due to increased absorption. When a wider flow channel was used, the signal-to-noise ratio was improved due to the larger sensing area. The extremely low power consumption and small size makes this μ-detector array potentially useful for the development of integrated μ-GC. Copyright © 2011 Elsevier B.V. All rights reserved.

  1. 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.

  2. Investigation of phase separation behavior and formation of plasmonic nanocomposites from polypeptide-gold nanorod nanoassemblies.

    PubMed

    Huang, Huang-Chiao; Nanda, Alisha; Rege, Kaushal

    2012-04-24

    Genetically engineered elastin-like polypeptides (ELP) can be interfaced with cetyltrimethyl ammonium bromide (CTAB)-stabilized gold nanorods (GNRs) resulting in the formation of stable dispersions (nanoassemblies). Increasing the dispersion temperature beyond the ELP transition temperature results in phase separation and formation of solid-phase ELP-GNR matrices (nanocomposites). Here, we investigated different physicochemical conditions that influence nanocomposite formation from temperature-induced phase separation of ELP-GNR nanoassemblies. The presence of cetyltrimethyl ammonium bromide (CTAB), used to template the formation of gold nanorods, plays a significant role in the phase separation behavior, with high concentrations of the surfactant leading to dramatic enhancements in ELP transition temperature. Nanocomposites could be generated at 37 °C in the presence of low CTAB concentrations (<1.5 mM); higher concentrations of CTAB necessitated higher temperatures (60 °C) due to elevated transition temperatures. The concentration of gold nanorods, however, had minimal influence on the phase separation behavior and nanocomposite formation. Further analysis of the kinetics of nanocomposite formation using a mathematical model indicated that CTAB largely influenced the early event of coacervation of ELP-GNR nanoassemblies leading to nanocomposites, but had minimal effect on nanocomposite maturation, which is a later-stage longer event. Finally, nanocomposites prepared in the presence of low CTAB concentrations demonstrated a superior photothermal response following laser irradiation compared to those generated using higher CTAB concentrations. Our results on understanding the formation of plasmonic/photothermal ELP-GNR nanocomposites have significant implications for tissue engineering, regenerative medicine, and drug delivery.

  3. Numerical investigation of thermal response of laser-irradiated biological tissue phantoms embedded with gold nanoshells.

    PubMed

    Phadnis, Akshay; Kumar, Sumit; Srivastava, Atul

    2016-10-01

    The work presented in this paper focuses on numerically investigating the thermal response of gold nanoshells-embedded biological tissue phantoms with potential applications into photo-thermal therapy wherein the interest is in destroying the cancerous cells with minimum damage to the surrounding healthy cells. The tissue phantom has been irradiated with a pico-second laser. Radiative transfer equation (RTE) has been employed to model the light-tissue interaction using discrete ordinate method (DOM). For determining the temperature distribution inside the tissue phantom, the RTE has been solved in combination with a generalized non-Fourier heat conduction model namely the dual phase lag bio-heat transfer model. The numerical code comprising the coupled RTE-bio-heat transfer equation, developed as a part of the current work, has been benchmarked against the experimental as well as the numerical results available in the literature. It has been demonstrated that the temperature of the optical inhomogeneity inside the biological tissue phantom embedded with gold nanoshells is relatively higher than that of the baseline case (no nanoshells) for the same laser power and operation time. The study clearly underlines the impact of nanoshell concentration and its size on the thermal response of the biological tissue sample. The comparative study concerned with the size and concentration of nanoshells showed that 60nm nanoshells with concentration of 5×10(15)mm(-3) result into the temperature levels that are optimum for the irreversible destruction of cancer infected cells in the context of photo-thermal therapy. To the best of the knowledge of the authors, the present study is one of the first attempts to quantify the influence of gold nanoshells on the temperature distributions inside the biological tissue phantoms upon laser irradiation using the dual phase lag heat conduction model.

  4. Colloidal stability of self-assembled monolayer-coated gold nanoparticles: the effects of surface compositional and structural heterogeneity.

    PubMed

    Huang, Rixiang; Carney, Randy P; Stellacci, Francesco; Lau, Boris L T

    2013-09-17

    Surface heterogeneity plays an important role in controlling colloidal phenomena. This study investigated the self-aggregation and bacterial adsorption of self-assembled monolayer coated gold nanoparticles (AuNPs) with different surface compositional and structural heterogeneity. Evaluation was performed on AuNPs coated with (1) one ligand with charged terminals (MUS), (2) two homogeneously distributed ligands with respectively charged and nonpolar terminals (brOT) and (3) two ligands with respectively charged and nonpolar terminals with stripe-like distribution (OT). The brOT particles have less negative electrophoretic mobility (EPM) values, smaller critical coagulation concentration (CCC) and larger adsorption rate on Escherichia coli than that of AuNPs with homogeneously charged groups, in good agreement with DLVO predictions. Although the ligand composition on the surface of AuNPs is the same, OT particles have less negative EPM values and faster rate of bacterial adsorption, but much larger CCC compared to brOT. The deviation of OT particles from brOT and MUS in their self-aggregation behavior reflects the effects of surface heterogeneity on electrical double layer structures at the interface. Results from the present study demonstrated that, besides chemical composition, organization of ligands on particle surface is important in determining their colloidal stability.

  5. One-pot reaction for the preparation of biofunctionalized self-assembled monolayers on gold surfaces

    NASA Astrophysics Data System (ADS)

    Raigoza, Annette F.; Fies, Whitney; Lim, Amber; Onyirioha, Kristeen; Webb, Lauren J.

    2017-02-01

    The Huisgen cycloaddition reaction ("click" chemistry) has been used extensively to functionalize surfaces with macromolecules in a straightforward manner. We have previously developed a procedure using the copper(I)-catalyzed click reaction to tether synthetic α-helical peptides carrying two alkyne groups to a well-ordered azide-terminated alkanethiol self-assembled monolayer (SAM) on a Au(111) surface. While convenient, click-based strategies potentially pose significant problems from reagents, solvents, and reaction temperatures that may irreversibly damage some molecules or substrates. Tuning click chemistry conditions would allow individual optimization of reaction conditions for a wide variety of biomolecules and substrate materials. Here, we explore the utility of simultaneous SAM formation and peptide-attachment chemistry in a one-pot reaction. We demonstrate that a formerly multistep reaction can be successfully carried out concurrently by mixing azide-terminated alkanethiols, CuCl, and a propargylglycine-containing peptide over a bare gold surface in ethanol and reacting at 70 °C. X-ray photoelectron spectroscopy (XPS), surface infrared spectroscopy, surface circular dichroic (CD) spectroscopy, and scanning tunneling microscopy (STM) were used to determine that this one-pot reaction strategy resulted in a high density of surface-bound α-helices without aggregation. This work demonstrates the simplicity and versatility of a SAM-plus-click chemistry strategy for functionalizing Au surfaces with structured biomolecules.

  6. Electronic correlation effects on the neutralization of Ga+ scattered by a gold surface

    NASA Astrophysics Data System (ADS)

    Tacca, M. S.; Bonetto, F.; Goldberg, E. C.

    2017-08-01

    The monotonous increasing with temperature behavior of the neutralization of Ga + scattered by a gold surface plus the nonmagnetic character of the ion induced to disregard the important electronic correlation effects. In this work, we show that contrary to this assumption, the electron-electron interaction in the Ga site is crucial for describing the experimental results. We extend the formalism previously used in the Sr + /Au system to include more than one valence orbital in the projectile, which is the case of Ga + , where the neutralization occurs to a p -type shell. We consider the six possible orbital-spin neutral configurations in a correlated way within the Anderson model. The comparison with the results obtained from a noninteracting electron model allows one to infer how important the many-body effects in the charge exchange between Ga + and the gold surface are. We also found that the proximity of the projectile one-electron energy levels to the substrate Fermi level determines the influence of electronic correlation effects on the neutral fraction and its temperature and velocity dependences.

  7. Effect of hydrophobicity on the stability of the wetting films of water formed on gold surfaces.

    PubMed

    Pan, L; Jung, S; Yoon, R-H

    2011-09-01

    We have developed a methodology that can be used to determine disjoining pressures (Π) in both stable and unstable wetting films from the spatial and temporal profiles of dynamic wetting films. The results show that wetting films drain initially by the capillary pressure created by the changes in curvature at the air/water interface and subsequently by the disjoining pressure created by surface forces. The drainage rate of the film formed on a gold surface with a receding contact angle (θ(r)) of 17° decreases with film thickness due to a corresponding increase in positive Π, resulting in the formation of a stable film. The wetting film formed on a hydrophobic gold with θ(r)=81° drains much faster due to the presence of negative Π in the film, resulting in film rupture. Analysis of the experimental data using the Frumkin-Derjaguin isotherm suggests that short-range hydrophobic forces are responsible for film rupture and long-range hydrophobic forces accelerate film thinning. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Surface-enhanced terahertz spectroscopy using gold rod structures resonant with terahertz waves.

    PubMed

    Ueno, Kosei; Nozawa, Sho; Misawa, Hiroaki

    2015-11-02

    Terahertz (THz) spectroscopy is a promising method to measure the spectrum of low-frequency modes of molecules or ensembles, such as crystals and polymers, including proteins. However, the main drawback of THz spectroscopy is its extremely low sensitivity. In the present study, we report on signal enhancement in THz spectroscopy achieved by depositing amino acid molecules or their derivatives on a gold rod structured silicon substrate whose localized surface plasmon resonance is exhibited in the THz frequency region. The distinct peaks derived from the enhancement of the inherent spectrum based on a molecular crystal were clearly observed when a longitudinal plasmon resonance mode of the gold rod structure was excited and the plasmon resonance band overlapped the molecular/intermolecular vibrational mode. We discuss the mechanism by which surface-enhanced THz spectroscopy was induced from the viewpoint of the enhancement of light-matter coupling due to plasmon excitation and the modulation of the plasmon band by dipole coupling between the plasmon dipole and molecular/intermolecular vibrational modes.

  9. Surface-enhanced resonance Raman scattering of polyaniline on silver and gold colloids.

    PubMed

    Izumi, Celly M S; Andrade, Gustavo F S; Temperini, Marcia L A

    2008-12-25

    The interaction of emeraldine base (PANI-EB) with silver and gold colloids was probed by using Surface-Enhanced Resonance Raman Scattering (SERRS) at 3 different exciting radiations. Due to the great sensitivity of SERRS technique the detection limit of PANI-EB concentration was ca. 2 x 10(-7) mol L(-1) in Ag and Au colloidal suspensions. The UV-vis-NIR spectra of metal colloids in function of PANI-EB concentrations showed that gold colloids present a higher degree of aggregation than silver colloids. SERRS of PANI-EB on metal colloids allowed the study of the polymeric species formed primarily on the metallic surface. The polymer formed after the adsorption of PANI-EB on metallic nanoparticles is strongly dependent on the nature of the metal colloids. The oxidation of PANI-EB to pernigraniline occurred for silver colloids, while a doping process of PANI-EB on Au nanoparticles was evidenced through the observation of the characteristic SERRS spectrum of emeraldine salt at 1064nm.

  10. Measurement of surface mercury fluxes at active industrial gold mines in Nevada (USA).

    PubMed

    Eckley, C S; Gustin, M; Marsik, F; Miller, M B

    2011-01-01

    Mercury (Hg) may be naturally associated with the rock units hosting precious and base metal deposits. Active gold mines are known to have point source releases of Hg associated with ore processing facilities. The nonpoint source release of Hg to the air from the large area (hundreds to thousands of hectares) of disturbed and processed material at industrial open pit gold mines has not been quantified. This paper describes the field data collected as part of a project focused on estimating nonpoint source emissions of Hg from two active mines in Nevada, USA. In situ Hg flux data were collected on diel and seasonal time steps using a dynamic flux chamber from representative mine surfaces. Hg fluxes ranged from <1500 ng m(-2) day(-1) for waste rock piles (0.6-3.5 μg g(-1)) to 684,000 ng m(-2) day(-1) for tailings (2.8-58 μg g(-1)). Releases were positively correlated with material Hg concentrations, surface grain size, and moisture content. Highest Hg releases occurred from materials under active cyanide leaching and from tailings impoundments containing processed high-grade ore. Data collected indicate that as mine sites are reclaimed and material disturbance ceases, emissions will decline. Additionally local cycling of atmospheric Hg (deposition and re-emission) was found to occur.

  11. Enhanced magneto-optical properties of semiconductor EuS nanocrystals assisted by surface plasmon resonance of gold nanoparticles.

    PubMed

    Kawashima, Akira; Nakanishi, Takayuki; Shibayama, Tamaki; Watanabe, Seiichi; Fujita, Koji; Tanaka, Katsuhisa; Koizumi, Hitoshi; Fushimi, Koji; Hasegawa, Yasuchika

    2013-10-18

    Remarkable magneto-optical properties of a new isolator material, that is, europium sulfide nanocrystals with gold (EuS-Au nanosystem), has been demonstrated for a future photo-information technology. Attachment of gold particles that exhibit surface plasmon resonance leads to amplification of the magneto-optical properties of the EuS nanocrystals. To construct the EuS-Au nanosystems, cubic EuS and spherical Au nanocrystals have been joined by a variety of organic linkers, that is, 1,2-ethanedithiol (EDT), 1,6-hexanedithiol (HDT), 1,10-decanedithiol (DDT), 1,4-bisethanethionaphthalene (NpEDT), or 1,4-bisdecanethionaphthalene (NpDDT) . Formation of these systems was observed by XRD, TEM, and absorption spectra measurements. The magneto-optical properties of the EuS-Au nanosystem have been characterized by using Faraday rotation spectroscopy. The Faraday rotation angle of the EuS-Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS-Au nanosystems was observed. The spin configuration in the excited state of the EuS-Au nanosystem was also investigated using photo-assisted electron paramagnetic resonance.

  12. Preparing metal-complex surfaces based on self-assembled monolayers of thiols and disulfides on gold

    NASA Astrophysics Data System (ADS)

    Dolzhikova, V. D.; Bogdanova, Yu. G.; Majouga, A. G.; Beloglazkina, E. K.; Kudrinsky, A. A.

    2017-02-01

    The complexation of monolayers of sulfur-containing ligands self-assembled on surface of gold with Co(II) and Cu(II) ions is studied using quartz crystal microbalance (QCM) and wetting measurements. The optimum conditions for obtaining metal-complex surfaces and the compositions of the resulting monolayers are determined.

  13. Facile synthesis of thermally stable poly(N-vinylpyrrolidone)-modified gold surfaces by surface-initiated atom transfer radical polymerization.

    PubMed

    Liu, Xiaoli; Sun, Kai; Wu, Zhaoqiang; Lu, Jianhong; Song, Bo; Tong, Weifang; Shi, Xiujuan; Chen, Hong

    2012-06-26

    Well-controlled polymerization of N-vinylpyrrolidone (NVP) on Au surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP) was carried out at room temperature by a silanization method. Initial attempts to graft poly(N-vinylpyrrolidone) (PVP) layers from initiators attached to alkanethiol monolayers yielded PVP films with thicknesses less than 5 nm. The combined factors of the difficulty in the controllable polymerization of NVP and the instability of alkanethiol monolayers led to the difficulty in the controlled polymerization of NVP on Au surfaces. Therefore, the silanization method was employed to form an adhesion layer for initiator attachment. This method allowed well-defined ATRP polymerization to occur on Au surfaces. Water contact angle, X-ray photoelectron spectroscopy (XPS), and reflectance Fourier transform infrared (reflectance FTIR) spectroscopy were used to characterize the modified surfaces. The PVP-modified gold surface remained stable at 130 °C for 3 h, showing excellent thermal stability. Thus, postfunctionalization of polymer brushes at elevated temperatures is made possible. The silanization method was also applied to modify SPR chips and showed potential applications in biosensors and biochips.

  14. High Relaxivity Gd(III)–DNA Gold Nanostars: Investigation of Shape Effects on Proton Relaxation

    PubMed Central

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

    2015-01-01

    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. PMID:25723190

  15. (90377) Sedna: Investigation of Surface Compositional Variation

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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 μm by the Spitzer Space Telescope. The visible and near-infrared spectra can be modeled with organic materials (triton and titan tholin), serpentine, and H2O ice in fairly significant amounts, and CH4, N2, and C2H6 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 CH3OH in place of CH4, 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. Based on observations obtained at the VLT Observatory Cerro Paranal of European Southern Observatory, ESO, Chile, in the framework of proposal 275.C-5055 and Large Program 178-C-0036/0867.

  16. (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.

  17. Development of Lateral Flow Assay Based on Size-Controlled Gold Nanoparticles for Detection of Hepatitis B Surface Antigen

    PubMed Central

    Kim, Dong Seok; Kim, Yong Tae; Hong, Seok Bok; Kim, Jinwoon; Heo, Nam Su; Lee, Moon-Keun; Lee, Seok Jae; Kim, Byeong Il; Kim, In Soo; Huh, Yun Suk; Choi, Bong Gill

    2016-01-01

    In this study, we developed lateral flow assay (LFA) biosensors for the detection of hepatitis B surface antigens using well-controlled gold nanoparticles (AuNPs). To enhance colorimetric signals, a seeded growth method was used for the preparation of size-controlled AuNPs with a narrow size distribution. Different sizes of AuNPs in the range of 342–137.8 nm were conjugated with antibodies and then optimized for the efficient detection of LFA biosensors. The conjugation stability was investigated by UV-vis spectroscopy of AuNP dispersion at various pH values and concentrations of antibody. Based on optimized conjugation conditions, the use of 42.7 ± 0.8 nm AuNPs exhibited superior performance for the detection of LFAs relative to other sizes of AuNPs. PMID:27999291

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

    NASA Astrophysics Data System (ADS)

    Jubb, A. M.; Jiao, Y.; Eres, G.; Retterer, S. T.; Gu, B.

    2016-03-01

    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 109 for adsorbed p-mercaptoaniline molecules.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

  19. 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.

  20. 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

  1. Electro-optically modulated localized surface plasmon resonance biosensors with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Wang, Tzyy-Jiann; Lin, Wen-Shao

    2006-10-01

    An integrated-optic biosensor based on electro-optically modulated localized surface plasmon resonance (LSPR) is demonstrated. This biosensor utilizes the electro-optic effect to modulate the wave vector of incident lightwave used to excite localized surface plasmons. Electro-optically modulated LSPR results in the analyte-dependent variation of output intensity with the applied voltage. The linear regression slope of this relation is used to determine the analyte concentration. On the sensing region of LSPR biosensor, human serum albumin is self-assembled on gold nanoparticles in order to sense the beta-blocker concentration. The use of the presented biosensor has the features of no intensity drift problem, no absorption diversity problem in different sample media, and noise reduction by linear regression analysis.

  2. 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.

  3. Localized surface plasmon resonance and refractive index sensitivity of vacuum-evaporated nanostructured gold thin films

    NASA Astrophysics Data System (ADS)

    Rai, V. N.; Srivastava, A. K.; Mukherjee, C.; Deb, S. K.

    2016-01-01

    Plasmonic properties of vacuum-evaporated nanostructured gold thin films having different types of nanoparticles are presented. The films with thickness ≥6 nm show the presence of nanorods having non-cylindrical shape with triangular base. Two characteristic plasmon bands have been recorded in absorption spectra. First one occurs below 500 nm and the other one at higher wavelength side. Both the peaks show dependence on the dielectric property of surroundings. The higher wavelength localized surface plasmon resonance peak shifts to higher wavelength with an increase in the nanoparticle size, surface roughness and refractive index of the surrounding (methylene blue dye coating). This shows that such thin films can be used as sensor for organic molecules with a refractive index sensitivity ranging from 250 to 305 nm/RIU (refractive index unit).

  4. Nanoparticle-protein interactions: a thermodynamic and kinetic study of the adsorption of bovine serum albumin to gold nanoparticle surfaces.

    PubMed

    Boulos, Stefano P; Davis, Tyler A; Yang, Jie An; Lohse, Samuel E; Alkilany, Alaaldin M; Holland, Lisa A; Murphy, Catherine J

    2013-12-03

    Investigating the adsorption process of proteins on nanoparticle surfaces is essential to understand how to control the biological interactions of functionalized nanoparticles. In this work, a library of spherical and rod-shaped gold nanoparticles (GNPs) was used to evaluate the process of protein adsorption to their surfaces. The binding of a model protein (bovine serum albumin, BSA) to GNPs as a function of particle shape, size, and surface charge was investigated. Two independent comparative analytical methods were used to evaluate the adsorption process: steady-state fluorescence quenching titration and affinity capillary electrophoresis (ACE). Although under favorable electrostatic conditions kinetic analysis showed a faster adsorption of BSA to the surface of cationic GNPs, equilibrium binding constant determinations indicated that BSA has a comparable binding affinity to all of the GNPs tested, regardless of surface charge. BSA was even found to adsorb strongly to GNPs with a pegylated/neutral surface. However, these fluorescence titrations suffer from significant interference from the strong light absorption of the GNPs. The BSA-GNP equilibrium binding constants, as determined by the ACE method, were 10(5) times lower than values determined using spectroscopic titrations. While both analytical methods could be suitable to determine the binding constants for protein adsorption to NP surfaces, both methods have limitations that complicate the determination of protein-GNP binding constants. The optical properties of GNPs interfere with Ka determinations by static fluorescence quenching analysis. ACE, in contrast, suffers from material compatibility issues, as positively charged GNPs adhere to the walls of the capillary during analysis. Researchers seeking to determine equilibrium binding constants for protein-GNP interactions should therefore utilize as many orthogonal techniques as possible to study a protein-GNP system.

  5. 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.

  6. 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.

  7. 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.

  8. An experimental and theoretical approach to investigate the effect of chain length on aminothiol adsorption and assembly on gold.

    PubMed

    Bedford, Erin; Humblot, Vincent; Méthivier, Christophe; Pradier, Claire-Marie; Gu, Frank; Tielens, Frederik; Boujday, Souhir

    2015-10-05

    Despite the numerous studies on the self-assembled monolayers (SAMs) of alkylthiols on gold, the mechanisms involved, especially the nature and influence of the thiol-gold interface are still under debate. In this work the adsorption of aminothiols on Au(111) surfaces has been studied by using surface IR and X-ray photoelectron spectroscopy (XPS) as well as by density functional theory (DFT) modeling. Two aminothiols were used, cysteamine (CEA) and mercaptoundecylamine (MUAM), which contain two and eleven carbon atoms, respectively. By combining experimental and theoretical methods, it was possible to draw a molecular picture of the thiol-gold interface. The long-chain aminothiol produced better ordered SAMs, but, interestingly, the XPS data showed different sulfur binding environments depending on the alkyl chain length; an additional peak at low binding energy was observed upon CEA adsorption, which indicates the presence of sulfur in a different environment. DFT modeling showed that the positions of the sulfur atoms in the SAMs on gold with similar unit cells [(2√3×2√3)R30°] depended on the length of the alkyl chain. Short-chain alkylthiol SAMs were adsorbed more strongly than long-chain thiol SAMs and were shown to induce surface reconstruction by extracting atoms from the surface, possibly forming adatom/vacancy combinations that lead to the additional XPS peak. In the case of short alkylthiols, the thiol-gold interface governs the layer, CEA adsorbs strongly, and the mechanism is closer to single-molecule adsorption than self-assembly, whereas for long chains, interactions between alkyl chains drive the system to self-assembly, leading to a higher level of SAM organization and restricting the influence of the sulfur-gold interface.

  9. Adsorption kinetics of an engineered gold binding Peptide by surface plasmon resonance spectroscopy and a quartz crystal microbalance.

    PubMed

    Tamerler, Candan; Oren, Ersin Emre; Duman, Memed; Venkatasubramanian, Eswaranand; Sarikaya, Mehmet

    2006-08-29

    The adsorption kinetics of an engineered gold binding peptide on gold surface was studied by using both quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy systems. The gold binding peptide was originally selected as a 14-amino acid sequence by cell surface display and then engineered to have a 3-repeat form (3R-GBP1) with improved binding characteristics. Both sets of adsorption data for 3R-GBP1 were fit to Langmuir models to extract kinetics and thermodynamics parameters. In SPR, the adsorption onto the surface shows a biexponential behavior and this is explained as the effect of bimodal surface topology of the polycrystalline gold substrate on 3R-GBP1 binding. Depending on the concentration of the peptide, a preferential adsorption on the surface takes place with different energy levels. The kinetic parameters (e.g., K(eq) approximately 10(7) M(-1)) and the binding energy (approximately -8.0 kcal/mol) are comparable to synthetic-based self-assembled monolayers. The results demonstrate the potential utilization of genetically engineered inorganic surface-specific peptides as molecular substrates due to their binding specificity, stability, and functionality in an aqueous-based environment.

  10. Molecular structure of cysteamine monolayers on silver and gold substrates. Comparative studies by surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Michota, Agnieszka; Kudelski, Andrzej; Bukowska, Jolanta

    2002-04-01

    Monolayers of cysteamine (2-aminoethanethiol) frequently work as linkage layers for adsorption of other molecules on metal surfaces. We compared the structure of cysteamine monolayers formed on gold and silver and the influence of various electrolytes on the structure of monolayers formed on both substrates. The monolayers formed on silver contain significantly higher portion of a trans conformer than monolayers on gold. Probably monolayers on silver are self-assembled in such a way that higher portion of the amino groups is unbonded to the surface, thus being available for attaching other molecules. The structure of cysteamine monolayers formed on gold is considerably more stable and resistive to the influence of electrolytes as compared to the silver substrate. The greater stability of the monolayers on Au surface was ascribed to the strong affinity of the amine groups toward this metal.

  11. Combined measurement of directional Raman scattering and surface-plasmon-polariton cone from adsorbates on smooth planar gold surfaces.

    PubMed

    Nyamekye, Charles K A; Weibel, Stephen C; Bobbitt, Jonathan M; Smith, Emily A

    2017-09-25

    Directional-surface-plasmon-coupled Raman scattering (directional RS) has the combined benefits of surface plasmon resonance and Raman spectroscopy, and provides the ability to measure adsorption and monolayer-sensitive chemical information. Directional RS is performed by optically coupling a 50 nm gold film to a Weierstrass prism in the Kretschmann configuration and scanning the angle of the incident laser under total internal reflection. The collected parameters on the prism side of the interface include a full surface-plasmon-polariton cone and the full Raman signal radiating from the cone as a function of incident angle. An instrument for performing directional RS and a quantitative study of the instrumental parameters are herein reported. To test the sensitivity and quantify the instrument parameters, self-assembled monolayers and 10 to 100 nm polymer films are studied. The signals are found to be well-modeled by two calculated angle-dependent parameters: three-dimensional finite-difference time-domain calculations of the electric field generated in the sample layer and projected to the far-field, and Fresnel calculations of the reflected light intensity. This is the first report of the quantitative study of the full surface-plasmon-polariton cone intensity, cone diameter, and directional Raman signal as a function of incident angle. We propose that directional RS is a viable alternative to surface plasmon resonance when added chemical information is beneficial.

  12. Global Transcriptomic Analysis of Model Human Cell Lines Exposed to Surface-Modified Gold Nanoparticles: The Effect of Surface Chemistry

    PubMed Central

    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. PMID:25491924

  13. Use of graphene and gold nanorods as substrates for the detection of pesticides by surface enhanced Raman spectroscopy.

    PubMed

    Nguyen, Trang H D; Zhang, Zhong; Mustapha, Azlin; Li, Hao; Lin, Mengshi

    2014-10-29

    This study aimed to use gold nanorods and graphene as key materials to fabricate high-performance substrates for the detection of pesticides by surface enhanced Raman spectroscopy (SERS). Three types of pesticides (azinphos-methyl, carbaryl, and phosmet) were selected. Gold nanorods have great potential to be used as a SERS substrate because it is easy to tune the surface plasmon resonance of the nanorods to the laser excitation wavelength of Raman spectroscopy. Graphene is a promising nanoscale material that can be used for supporting metal nanostructures. Three types of novel SERS substrates were fabricated, including graphene-gold film-gold nanorod (G-Au-AuNR) substrate, gold film-gold nanorod (Au-AuNR) substrate, and graphene coupled with gold nanorods (G-AuNR). The results demonstrate that G-Au-AuNR substrates exhibited the strongest Raman signals of the selected pesticides, followed by the Au-AuNR substrates. G-AuNR exhibited the weakest Raman signals, and no characteristic spectral features of the analytes were obtained. A partial least-squares method was used to develop quantitative models for the analysis of spectral data (R = 0.94, 0.87, and 0.86 for azinphos-methyl, carbaryl, and phosmet, respectively). The G-Au-AuNRs substrate was able to detect all three types of pesticides at the parts per million level with limits of detection at around 5, 5, and 9 ppm for azinphos-methyl, carbaryl, and phosmet, respectively. These results indicate that combining gold nanorods and graphene has great potential in the fabrication of sensitive, lightweight, and flexible substrates for SERS applications to improve food safety.

  14. Potential-dependent adsorption/desorption behavior of perfluorosulfonated ionomer on a gold electrode surface studied by cyclic voltammetry, electrochemical quartz microbalance, and electrochemical atomic force microscopy.

    PubMed

    Masuda, Takuya; Ikeda, Kota; Uosaki, Kohei

    2013-02-19

    Potential-dependent adsorption/desorption behavior of perfluorosulfonated ionomer (PFSI) on a gold electrode was investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and electrochemical atomic force microscopy (EC-AFM) in a Nafion (i.e., PFSI) dispersed aqueous solution without any other electrolyte. It was found that PFSI serves as an electrolyte and that electrochemical measurements can be performed in this solution without any significant IR drop. PFSI molecules were adsorbed on the Au surface in the lying-down configuration in the potential range between 0 and 0.45 V, the amount of adsorbed PFSI increased when the potential was made more positive than 0.75 V, and the adsorbed PFSI fully desorbed from the surface at potentials more positive than 1.4 V where gold oxide was formed. Once the gold oxide had been reduced, PFSI readsorbed on the surface, albeit slowly. PFSI desorbed from the surface as the potential was made more negative than 0 V. These processes took place reversibly.

  15. 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.

  16. 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.

  17. Determination of colloidal gold nanoparticle surface areas, concentrations, and sizes through quantitative ligand adsorption.

    PubMed

    Gadogbe, Manuel; Ansar, Siyam M; He, Guoliang; Collier, Willard E; Rodriguez, Jose; Liu, Dong; Chu, I-Wei; Zhang, Dongmao

    2013-01-01

    Determination of the true surface areas, concentrations, and particle sizes of gold nanoparticles (AuNPs) is a challenging issue due to the nanoparticle morphological irregularity, surface roughness, and size distributions. A ligand adsorption-based technique for determining AuNP surface areas in solution is reported. Using a water-soluble, stable, and highly UV-vis active organothiol, 2-mercaptobenzimidazole (MBI), as the probe ligand, we demonstrated that the amount of ligand adsorbed is proportional to the AuNP surface area. The equivalent spherical AuNP sizes and concentrations were determined by combining the MBI adsorption measurement with Au(3+) quantification of aqua regia-digested AuNPs. The experimental results from the MBI adsorption method for a series of commercial colloidal AuNPs with nominal diameters of 10, 30, 50, and 90 nm were compared with those determined using dynamic light scattering, transmission electron microscopy, and localized surface plasmonic resonance methods. The ligand adsorption-based technique is highly reproducible and simple to implement. It only requires a UV-vis spectrophotometer for characterization of in-house-prepared AuNPs.

  18. Fungal surface protein mediated one-pot synthesis of stable and hemocompatible gold nanoparticles.

    PubMed

    Kitching, Michael; Choudhary, Priyadarshani; Inguva, Saikumar; Guo, Yina; Ramani, Meghana; Das, Sujoy K; Marsili, Enrico

    2016-12-01

    Despite their large secretome and wide applications in bioprocesses, fungi remain underexplored in metal nanoparticles (MNP) biosynthesis. Previous studies have shown that cell surface proteins of Rhizopus oryzae play a crucial role in biomineralization of Au(III) to produce gold nanoparticles (AuNPs). Therefore, it is hypothesized that purified cell surface protein may produce in vitro AuNPs with narrow size distribution for biomedical and biocatalytic applications. However, different protein extraction methods might affect protein stability and the AuNP biosynthesis process. Herein, we have explored the extraction of cell surface proteins from R. oryzae using common detergents and reducing agent (sodium dodecyl sulfate (SDS) Triton X-100, and 1,4-dithiothreitol (DTT)) and their effect on the size and shape of the biosynthetic AuNPs. The surface proteins extracted with reducing agent (DTT) and non-ionic detergent (Triton X-100) produce spherical AuNPs with a mean particle size of 16±7nm, and 19±4nm, respectively, while the AuNPs produced by the surface protein extracted by ionic detergent (SDS) are flower-like AuNPs with broader size distribution of 43±19nm. This synthetic approach does not require use of any harsh chemicals, multistep preparation and separation process, favouring environmental sustainability. The biosynthetic AuNPs thus formed, are stable in different physiological buffers and hemocompatible, making them suitable for biomedical applications.

  19. Stability investigation of laser darkened metal surfaces

    NASA Astrophysics Data System (ADS)

    Hopp, Béla; Smausz, Tomi; Lentner, Márton; Kopniczky, Judit; Tápai, Csaba; Gera, Tamás; Csizmadia, Tamás; Ehrhardt, Martin; Lorenz, Pierre; Zimmer, Klaus

    2017-09-01

    Pulsed laser irradiation-induced reflectivity decrease of metal surfaces is a well-established phenomenon, which is extensively utilized in numerous applications. Since the stability of these black surfaces is often a demand, we investigated the resistance of darkened copper and titanium surfaces against optical and mechanical damages. For optical stability studies, samples were irradiated by a probe laser beam ( λ = 775 nm, FWHM = 150 fs, f = 1 kHz) at different fluences (0-300 mJ/cm2), while the mechanical stability was studied with scratch test using 2.5 µm radius tip and applying normal force in 29.4-147 µN range. The observed reflectivity and morphological changes indicated that the optical damage threshold fluence is 130 and 160 mJ/cm2 for copper and titanium surfaces, respectively. Mechanical damage only in case of copper could be detected in the applied parameter range indicating a scratch hardness of 21.5 MPa.

  20. Tuned longitudinal surface plasmon resonance and third-order nonlinear optical properties of gold nanorods.

    PubMed

    Tsutsui, Yushi; Hayakawa, Tomokatsu; Kawamura, Go; Nogami, Masayuki

    2011-07-08

    In order to elucidate the relationship for third-order nonlinear optical properties of anisotropic metal nanoparticles between the incident laser wavelength and surface plasmon resonance (SPR) wavelength, gold nanorods (GNRs) with a tuned longitudinal SPR mode in frequency were prepared by seed-mediated methods with two different surfactants, cetyltrimethylammonium bromide (CTAB) and benzyldimethylammonium chloride (BDAC). The real and imaginary parts of the third-order nonlinear optical susceptibilities χ(3) were examined by near-infrared (800 nm) femtosecond Z-scan and I-scan techniques for various gold sols with SPR wavelengths of 530 nm (spheres), 800 nm (nanorods) and 1000 nm (nanorods), named as 530GNSs, 800GNRs and 1000GNRs, respectively. All the samples showed intrinsically third-order nonlinear optical refractive responses. However, as for the real part of χ(3) for one particle, 800GNRs whose plasmon peak was tuned to the incident laser wavelength exhibited a Reχ(3) value 45 times stronger than 530GNSs. More interestingly, the imaginary part of χ(3) was more greatly influenced at the tuned SPR wavelength. Here we first demonstrate that 800GNRs showed plasmon-enhanced saturable absorption (SA) due to a longitudinal SPR tuned to the incident laser wavelength.

  1. DNA origami based assembly of gold nanoparticle dimers for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Thacker, Vivek V.; Herrmann, Lars O.; Sigle, Daniel O.; Zhang, Tao; Liedl, Tim; Baumberg, Jeremy J.; Keyser, Ulrich F.

    2014-03-01

    Plasmonic sensors are extremely promising candidates for label-free single-molecule analysis but require exquisite control over the physical arrangement of metallic nanostructures. Here we employ self-assembly based on the DNA origami technique for accurate positioning of individual gold nanoparticles. Our innovative design leads to strong plasmonic coupling between two 40 nm gold nanoparticles reproducibly held with gaps of 3.3±1 nm. This is confirmed through far field scattering measurements on individual dimers which reveal a significant red shift in the plasmonic resonance peaks, consistent with the high dielectric environment due to the surrounding DNA. We use surface-enhanced Raman scattering (SERS) to demonstrate local field enhancements of several orders of magnitude through detection of a small number of dye molecules as well as short single-stranded DNA oligonucleotides. This demonstrates that DNA origami is a powerful tool for the high-yield creation of SERS-active nanoparticle assemblies with reliable sub-5 nm gap sizes.

  2. 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.

  3. Modulating the physicochemical and structural properties of gold-functionalized protein nanotubes through thiol surface modification.

    PubMed

    Carreño-Fuentes, Liliana; Plascencia-Villa, Germán; Palomares, Laura A; Moya, Sergio E; Ramírez, Octavio T

    2014-12-16

    Biomolecules are advantageous scaffolds for the synthesis and ordering of metallic nanoparticles. Rotavirus VP6 nanotubes possess intrinsic affinity to metal ions, a property that has been exploited to synthesize gold nanoparticles over them. The resulting nanobiomaterials have unique properties useful for novel applications. However, the formed nanobiomaterials lack of colloidal stability and flocculate, limiting their functionality. Here we demonstrate that it is possible to synthesize thiol-protected gold nanoparticles over VP6 nanotubes, which resulted in soluble nanobiomaterials. With this strategy, it was possible to modulate the size, colloidal stability, and surface plasmon resonance of the synthesized nanoparticles by controlling the content of the thiolated ligands. Two types of water-soluble ligands were tested, a small linear ligand, sodium 3-mercapto-1-propanesulfonate (MPS), and a bulky ligand, 5-mercaptopentyl β-D-glucopyranoside (GlcC5SH). The synthesized nanobiomaterials had a higher stability in suspension, as determined by Z-potential measurements. To the extent of our knowledge, this is the first time that a rational strategy is developed to modulate the particular properties of metal nanoparticles in situ synthesized over a protein bioscaffold through thiol coating, achieving a high spatial and structural organization of nanoparticles in a single integrative hybrid structure.

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

    SciTech Connect

    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 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 109 for adsorbed p-mercaptoaniline molecules.

  5. 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.

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

    DOE PAGES

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

    2016-02-15

    Here we demonstrate large area arrays of elevated gold ellipse dimers with precisely controlled gaps for use as sensitive and highly controllable surface enhanced Raman scattering (SERS) substrates. The significantly enhanced Raman signal observed with SERS arises from both localized and long range plasmonic effects. By controlling the geometry of a SERS substrate, in this case the size and aspect ratio of individual ellipses, the plasmon resonance can be tuned in a broad wavelength range, providing a method for designing the response of SERS substrates at different excitation wavelengths. Plasmon effects exhibited by the elevated gold ellipse dimer substrates aremore » also demonstrated and confirmed through finite difference time domain (FDTD) simulations. A plasmon resonance red shift with an increase of the ellipse aspect ratio is observed, allowing systematic control of the resulting SERS signal intensity. Optimized elevated ellipse dimer substrates with 10±2 nm gaps exhibit uniform SERS enhancement factors on the order of 109 for adsorbed p-mercaptoaniline molecules.« less

  7. 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.

  8. 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.

  9. 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

    2016-11-05

    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.

  10. 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. Copyright © 2016. Published by Elsevier B.V.

  11. 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.

  12. Theoretical investigation on DNA/RNA base pairs mediated by copper, silver, and gold cations.

    PubMed

    Marino, Tiziana; Russo, Nino; Toscano, Marirosa; Pavelka, Matej

    2012-02-14

    B3LYP density functional based computations were performed in order to characterize the interactions present in some Cu(+), Ag(+), and Au(+) metal ion-mediated DNA and RNA base pairs from both structural and electronic points of view. Examined systems involve as ligands canonical Watson-Crick, Hoogsteen and Wobble base pairs. Two artificial Hoogsteen base pairs were also taken into account. Binding energy values indicate that complexes involving silver cations are less stable than those in which copper or gold are present, and propose a similar behaviour for these two latter ions. The nature of the bond linking metal ions and bases was described by the NBO analysis that suggests metal coordinative interactions to be covalent. An evaluation of the dispersion contributions for the investigated systems was performed with the B3LYP-D3 functional.

  13. Time-of-flight-secondary ion mass spectrometry and cyclic voltammetry studies of self-assembly of dodecanethiol on a nanoporous gold surface.

    PubMed

    Hafez, Aly M; Huber, Andreas; Wenclawiak, Bernd W

    2013-03-19

    Preparation of a nanoporous gold surface by dealloying (etching) of a 585 gold plate (58.5% Au, 30% Ag, and 11.5% non-noble metals) was studied by applying acidic and thermal treatment of the gold plate. The gold plate surface was studied before and after the etching process using different analytical techniques like field emission scanning electron microscope (FE-SEM) with an energy dispersive X-ray spectroscopy analyzer (EDX), cyclic voltammetry (CV), and time-of-flight-secondary ion mass spectrometry (TOF-SIMS). CV analysis of the gold surface has shown that overnight etching with warm nitric acid increases the surface area 20 times higher than before etching. FE-SEM analysis has shown that a nanoporous gold surface with pore diameter ≤100 nm was obtained. SIMS depth profile analysis and EDX analysis have shown that the nanoporous gold surface was obtained as a result of removing the silver and copper from the first layers of the plate. The nanoporous gold surface was used as a substrate for self-assembly of dodecanethiol and has shown a higher extraction efficiency than the unetched gold alloy.

  14. Preliminary investigation of gold mineralization in the Pedro Dome-Cleary Summit area, Fairbanks district, Alaska

    USGS Publications Warehouse

    Pilkington, H.D.; Forbes, R.B.; Hawkins, D.B.; Chapman, R.M.; Swainbank, R.C.

    1969-01-01

    Anomalous gold values in mineralized veins and hydrothermally altered quartz-mica schist in the Pedro Dome-Cleary Summit area of the Fairbanks district suggest the presence of numerous small low- to high-grade lodes. Anomalous concentrations of gold were found to exist in the wall rocks adjacent to mineralized veins. In general, the gold concentration gradients in these wall rocks are much too steep to increase appreciably the mineable width of the veins. Anomalous gold values were also detected in bedrock samples taken by means of a power auger on the Murphy Dome Road along the southwest extension of the Pedro Dome-Cleary Summit mineralized belt.

  15. Reconnaissance investigations of ancient gold mines in the southern part of the Wadi Bidah District, Jabal Ibrahim and Al Aqiq quadrangles, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Worl, R.G.; Smith, C.W.

    1982-01-01

    Ancient gold mines in the southern part of the Wadi Bidah district, Kingdom of Saudi Arabia, are located either within lenses of ferruginous chert or in large felsic intrusions of Precambrian age. All are associated with quartz veins, stringers, and stockworks. Samples from both types of deposits have low silver and base-metal contents; samples from deposits within ferruginous chert have anomalous arsenic contents. None of the deposits are large enough to be considered as prime exploration targets at this time. Analytical results from the Bani Sar deposit, which is located within felsic plutonic rocks, are encouraging, but additional surface investigations are needed to define the size and extent of the mineralized zone. Deposits associated with ferruginous chert are also of exploration interest. Anomalous gold contents and other evidence of mineralization were found along a considerable exposure of the metasedimentary unit that contains the chert lenses.

  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

    2015-05-05

    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.

  17. Excess thermodynamic properties of thin water films confined between hydrophobized gold surfaces.

    PubMed

    Wang, Jialin; Yoon, Roe-Hoan; Eriksson, Jan Christer

    2011-12-01

    Surface forces between gold surfaces were measured in pure water at temperatures in the range of 10-40 °C using an atomic force microscope (AFM). The surfaces were hydrophobized by self-assembly of alkanethiols (C(n)SH) with n=2 and 16 in ethanol solutions. The data were used to determine the changes in excess free energies (ΔG(f)) of the thin water films per unit area by using the Derjaguin approximation [1]. The free energy data were then used to determine the changes in excess film entropy (ΔS(f)) and the excess film enthalpy (ΔH(f)) per unit area. The results show that both ΔS(f) and ΔH(f) decrease with decreasing film thickness, suggesting that the macroscopic hydrophobic interaction involves building some kind of structures in the intervening thin films of water. It was found that |ΔH(f)|>|TΔS(f)|, which is a necessary condition for an attractive force to appear when the enthalpy and entropy changes are both negative. That macroscopic hydrophobic interaction is enthalpically driven is contrary to the hydrophobic interactions at molecular scale. The results obtained in the present work are used to discuss possible origins for the long-range attractions observed between hydrophobic surfaces.

  18. Thermal-driven attachment of gold nanoparticles prepared with ascorbic acid onto indium tin oxide surfaces

    NASA Astrophysics Data System (ADS)

    Aziz, Md. Abdul; Oyama, Munetaka

    2013-05-01

    Thermal-driven attachment of gold nanoparticles (AuNPs), of which size was less than 50 nm, onto the surfaces of indium tin oxide (ITO) is reported as a new phenomenon. This was permitted by preparing AuNPs via the reduction of hydrogen tetrachloroaurate (HAuCl4) with ascorbic acid (AA). While the AuNPs prepared via the AA reduction sparsely attached on the surface of ITO even at room temperature, a heat-up treatment at ca. 75 °C caused denser attachment of AuNPs on ITO surfaces. The attached density and the homogeneity after the thermal treatment were better than those of AuNP/ITO prepared using 3-aminopropyl-trimethoxysilane linker molecules. The denser attachment was observed similarly both by the immersion of ITO samples after the preparations of AuNPs by AA and by the in situ preparation of AuNPs with AA together with ITO samples. Thus, it is considered that the thermal-driven attachment of AuNPs would occur after the formation of AuNPs in the aqueous solutions, not via the growth of AuNPs on ITO surfaces. The preparation of AuNPs with AA would be a key for the thermal-driven attachment because the same attachments were not observed for AuNPs prepared with citrate ions or commercially available tannic acid-capped AuNPs.

  19. Neutralization of slow multicharged ions at a clean gold surface: Electron-emission statistics

    NASA Astrophysics Data System (ADS)

    Kurz, H.; Aumayr, F.; Lemell, C.; Töglhofer, K.; Winter, Hp.

    1993-09-01

    Emission of slow electrons (Ee<=60 eV) induced by impact of slow multicharged ions (impact velocity vp<=2×105 m/s) onto an atomically clean, polycrystalline gold surface has been studied both experimentally and by numerical simulation, based on the resulting electron-emission statistics. The projectile ions (Nq+, q=5,6; Neq+, q=5-10 Arq+, q=5-16 Krq+, q=5-10 Xeq+, q=6,8,10; Iq+, q=16,20,23,25) have been extracted from a recoil ion source pumped by the GSI UNILAC heavy-ion accelerator in Darmstadt, Germany. We discuss the shape of the experimentally obtained electron-emission statistics and, by means of numerical simulation based on the classical over-the-barrier model put forward recently by Burgdörfer, Lerner, and Meyer [Phys. Rev. A 44, 5674 (1991)], identify the various processes contributing to the ``above-surface'' electron emission, i.e., taking place until projectile impact on the surface. In particular, for impact of slow (E>=50 eV) Ar12+ we show that most of the emitted electrons have energies below 50 eV, with the above-surface-produced fast Auger electrons being a small minority of less than 1%.

  20. 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.

  1. Gold nanoparticle biodistribution: Cell, blood, and tissue interactions as a function of nanoparticle surface properties

    NASA Astrophysics Data System (ADS)

    Shah, Neha B.

    Intravenously injected gold nanoparticles (GNPs) hold a great promise for clinical diagnostic and therapeutic applications. A critical issue in their implementation is incomplete mechanistic understanding of their in vivo biodistribution. Two major limitations in optimizing the biodistribution of NPs are: (1) achieving the highest accumulation at the disease site, and (2) avoiding accumulation in healthy organs including liver and spleen. To overcome these limitations, the interactions of GNPs with biological system must be better understood. The research described in this dissertation sought to advance the field of GNP in vivo biodistribution by elucidating the effects of GNP surface properties such as surface charge, ligand, and polyethylene glycol (PEG) coverage. It was shown that the interactions of GNPs with cells and tissues were a function of their surface properties. A Confocal Raman Microscopy based technique was developed to study GNPs interactions with cells in vitro in fast, label-free, and non-invasive way. It was further shown that GNP surface properties strongly influence their blood circulation time in vivo. It was demonstrated that GNPs interact with circulating blood cells including platelets and monocytes, which may play a role in their clearance from blood stream. Most of the injected dose was shown to accumulate in liver and spleen; however, both organs displayed a different mechanism of uptake and distribution of GNPs. Long-term biodistribution studies further suggested that GNPs were still found in liver and spleen after 4 months, but GNPs showed clearance from liver overtime.

  2. Highly Sensitive Detection of Target Biomolecules on Cell Surface Using Gold Nanoparticle Conjugated with Aptamer Probe

    NASA Astrophysics Data System (ADS)

    Kim, Hyonchol; Terazono, Hideyuki; Hayashi, Masahito; Takei, Hiroyuki; Yasuda, Kenji

    2012-06-01

    A method of gold nanoparticle (Au NP) labeling with backscattered electron (BE) imaging of field emission scanning electron microscopy (FE-SEM) was applied for specific detection of target biomolecules on a cell surface. A single-stranded DNA aptamer, which specifically binds to the target molecule on a human acute lymphoblastic leukemia cell, was conjugated with a 20 nm Au NP and used as a probe to label its target molecule on the cell. The Au NP probe was incubated with the cell, and the interaction was confirmed using BE imaging of FE-SEM through direct counting of the number of Au NPs attached on the target cell surface. Specific Au NP-aptamer probes were observed on a single cell surface and their spatial distributions including submicron-order localizations were also clearly visualized, whereas the nonspecific aptamer probes were not observed on it. The aptamer probe can be potentially dislodged from the cell surface with treatment of nucleases, indicating that Au NP-conjugated aptamer probes can be used as sensitive and reversible probes to label target biomolecules on cells.

  3. Surface plasmon resonance-induced photoactivation of gold nanoparticles as mitochondria-targeted therapeutic agents for pancreatic cancer.

    PubMed

    Mocan, Lucian; Ilie, Ioana; Tabaran, Flaviu A; Dana, Bartos; Zaharie, Florin; Zdrehus, Claudiu; Puia, Cosmin; Mocan, Teodora; Muntean, Valentin; Teodora, Pop; Ofelia, Mosteanu; Marcel, Tantau; Iancu, Cornel

    2013-12-01

    Noble metal nanoparticles such as gold nanoparticles can strongly absorb light in the visible region by inducing coherent collective oscillation of conduction band electrons in strong resonance with visible frequencies of light. This phenomenon is frequently termed as surface plasmon resonance (SPR). The main objective was to study the effects of laser photoactivated gold nanoparticles (by means of SPR) on human pancreatic cancer cells. Gold nanoparticles obtained using standard wet chemical methods (with sodium borohydride as a reducing agent) underwent photoexcitation using 2w 808 nm laser and further administered to 1.4E7 pancreatic cancer cell lines. Flow cytometry, transmission electron microscopy, phase contrast microscopy, quantitative proteomics and confocal microscopy combined with immunochemical staining were used to examine the interaction between photo excited gold nanoparticles and pancreatic cancer cells. The study shows that phonon-phonon interactions following laser photoexcitation of gold nanoparticles exhibit increased intracellular uptake, as well as mitochondrial swelling, closely followed by mitochondrial inner membrane permeabilization and depolarization. This unique data may represent a major step in mitochondria-targeted anticancer therapies using laser-activated gold nanoparticles.

  4. Gold nanoparticle localization at the core surface by using thermosensitive core-shell particles as a template.

    PubMed

    Suzuki, Daisuke; Kawaguchi, Haruma

    2005-12-06

    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.

  5. 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.

  6. High performance gold nanorods and silver nanocubes in surface-enhanced Raman spectroscopy of pesticides.

    PubMed

    Costa, Jean Claudio Santos; Ando, Rômulo Augusto; Sant'Ana, Antonio Carlos; Rossi, Liane Marcia; Santos, Paulo Sérgio; Temperini, Márcia Laudelina Arruda; Corio, Paola

    2009-09-14

    The behavior of Au nanorods and Ag nanocubes as analytical sensors was evaluated for three different classes of herbicides. The use of such anisotropic nanoparticles in surface-enhanced Raman scattering (SERS) experiments allows the one to obtain the spectrum of crystal violet dye in the single molecule regime, as well as the pesticides dichlorophenoxyacetic acid (2,4-D), trichlorfon and ametryn. Such metallic substrates show high SERS performance at low analyte concentrations making them adequate for use as analytical sensors. Density functional theory (DFT) calculations of the geometries and vibrational wavenumbers of the adsorbates in the presence of silver or gold atoms were used to elucidate the nature of adsorbate-nanostructure bonding in each case and support the enhancement patterns observed in each SERS spectrum.

  7. Acoustic Sensing Based on Density Shift of Microspheres by Surface Binding of Gold Nanoparticles.

    PubMed

    Miyagawa, Akihisa; Inoue, Yoshinori; Harada, Makoto; Okada, Tetsuo

    2017-01-01

    Herein, we propose a concept for sensing based on density changes of microparticles (MPs) caused by a biochemical reaction. The MPs are levitated by a combined acoustic-gravitational force at a position determined by the density and compressibility. Importantly, the levitation is independent of the MPs sizes. When gold nanoparticles (AuNPs) are bound on the surface of polymer MPs through a reaction, the density of the MPs dramatically increases, and their levitation position in the acoustic-gravitational field is lowered. Because the shift of the levitation position is proportional to the number of AuNPs bound on one MP, we can determine the number of molecules involved in the reaction. The avidin-biotin reaction is used to demonstrate the effectiveness of this concept. The number of molecules involved in the reaction is very small because the reaction space is small for an MP; thus, the method has potential for highly sensitive detection.

  8. Vapour-phase gold-surface-mediated coupling of aldehydes with methanol.

    PubMed

    Xu, Bingjun; Liu, Xiaoying; Haubrich, Jan; Friend, Cynthia M

    2010-01-01

    Selective coupling of oxygenates is critical to many synthetic processes, including those necessary for the development of alternative fuels. We report a general process for selective coupling of aldehydes and methanol as a route to ester synthesis. All steps are mediated by oxygen-covered metallic gold nanoparticles on Au(111). Remarkably, cross-coupling of methanol with formaldehyde, acetaldehyde, benzaldehyde and benzeneacetaldehyde to methyl esters is promoted by oxygen-covered Au(111) below room temperature with high selectivity. The high selectivity is attributed to the ease of nucleophilic attack of the aldehydes by the methoxy intermediate-formed from methanol on the surface-which yields the methyl esters. The competing combustion occurs via attack of both methanol and the aldehydes by oxygen. The mechanistic model constructed in this study provides insight into factors that control selectivity and clearly elucidates the crucial role of Au nanoparticles as active species in the catalytic oxidation of alcohols, even in solution.

  9. Strong surface enhanced Raman scattering from gold nanoarrays obtained by direct laser writing

    NASA Astrophysics Data System (ADS)

    Ivanov, V. G.; Todorov, N. D.; Petrov, L. S.; Ritacco, T.; Giocondo, M.; Vlakhov, E. S.

    2016-10-01

    We report for surface enhanced Raman scattering (SERS) from arrays of gold nanoparticles produced by 2-photons photo-reduction of the metallic precursor (HAuCl4) hosted in a Poly-Vinyl Alcohol (PVA) matrix, on glass substrates. Samples with the same pattern but featuring different nanoparticles size and density were obtained by varying the writing laser power and scanning speed. The Raman spectra were recorded from samples immersed in a solution of rhodamine-6G (R6G), as well as, after exposure of the samples in xylene. SERS enhancement factors of up to ∼104 were obtained for both analytes. The measurements show that the SERS enhancement is maximized on golden strips produced at higher writing laser power and lower scanning speed, where closer nanoparticles packing is obtained..

  10. 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.

  11. Surface plasmons in suspended graphene: launching with in-plane gold nanoantenna and propagation properties.

    PubMed

    Legrand, D; Le Cunff, L O; Bruyant, A; Salas-Montiel, R; Liu, Z; Tay, B K; Maurer, T; Bachelot, R

    2017-07-24

    Graphene physics and plasmonics are two fields which, once combined, promise a variety of exciting applications. One of those applications is the integration of active nano-optoelectronic devices in electronic systems, using the fact that plasmons in graphene are tunable, highly confined and weakly damped. A crucial challenge remains before achieving these active devices: finding a platform enabling a high propagation of Graphene Plasmons Polaritons (GPPs). Suspended graphene presenting ultrahigh electron mobility has given rise to increasing interest. We numerically studied the plasmonic properties of suspended graphene. We propose a hybrid configuration and a set of conditions to launch graphene plasmons via an in-plane gold nanoantenna, for micrometric propagation of surface plasmons in suspended graphene. Finally, we propose a realistic optoelectronic device based on the use of suspended graphene.

  12. Localized surface plasmon resonance biosensing with large area of gold nanoholes fabricated by nanosphere lithography.

    PubMed

    Xiang, Gansheng; Zhang, Nan; Zhou, Xiaodong

    2010-03-09

    Localized surface plasmon resonance (LSPR) has been extensively studied as potential chemical and biological sensing platform due to its high sensitivity to local refractive index change induced by molecule adsorbate. Previous experiments have demonstrated the LSPR generated by gold nanoholes and its biosensing. Here, we realize large uniform area of nanoholes on scale of cm2 on glass substrate by nanosphere lithography which is essential for mass production. The morphology of the nanoholes is characterized using scanning electron microscope and atomic force microscope. The LSPR sensitivity of the nanoholes to local refractive index is measured to be 36 nm/RIU. However, the chip has demonstrated high sensitivity and specificity in biosensing: bovine serum albumin adsorption is detected with LSPR peak redshift of 27 nm, and biotin-streptavidin immunoassay renders a LSPR redshift of 11 nm. This work forms a foundation toward the cost-effective, high-throughput, reliable and robust chip-based LSPR biosensor.

  13. Hybrid Structures for Surface-Enhanced Raman Scattering: DNA Origami/Gold Nanoparticle Dimer/Graphene.

    PubMed

    Prinz, Julia; Matković, Aleksandar; Pešić, Jelena; Gajić, Radoš; Bald, Ilko

    2016-10-01

    A combination of three innovative materials within one hybrid structure to explore the synergistic interaction of their individual properties is presented. The unique electronic, mechanical, and thermal properties of graphene are combined with the plasmonic properties of gold nanoparticle (AuNP) dimers, which are assembled using DNA origami nanostructures. This novel hybrid structure is characterized by means of correlated atomic force microscopy and surface-enhanced Raman scattering (SERS). It is demonstrated that strong interactions between graphene and AuNPs result in superior SERS performance of the hybrid structure compared to their individual components. This is particularly evident in efficient fluorescence quenching, reduced background, and a decrease of the photobleaching rate up to one order of magnitude. The versatility of DNA origami s