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Au Nanoparticles (au + nanoparticle)
Selected AbstractsSeed-Mediated Synthesis of Truncated Gold Decahedrons with a AuCl/Oleylamine Complex as PrecursorADVANCED MATERIALS, Issue 17 2010Yanyun Ma A seed-mediated growth method is described for the synthesis of a novel type of Au nanoparticles,truncated decahedrons with a pentagonal, platelike structure (see figure). The precursor is based on the AuCl/oleylamine complex. TEM analyses reveal that the truncated Au nanoparticle has two types of truncation: one is parallel to the five-fold axis and the other is perpendicular to the five-fold axis. [source] Selective Electroless Deposition of Cu on an Ultrathin Au Film PatternMACROMOLECULAR RAPID COMMUNICATIONS, Issue 22 2004Maofeng Zhang Abstract Summary: In this report an ultrathin Au nanoparticle (AuNP) film composed of photosensitive diazoresin (DR) and mercaptophenol (MP) capped AuNPs (MP-AuNPs) was fabricated by self-assembly (SA). The DR/MP-AuNP film was then patterned through a photomask by selective exposure to UV light and instantly developed in sodium dodecyl sulfate (SDS) aqueous solution. After sintering at 550,°C to remove the organic components, the DR/MP-AuNPs formed AuNPs. Taking advantage of the catalytic susceptibility of AuNPs toward electroless deposition of Cu, a Cu film micropattern with fine resolution (ca. 2,3 ,m) and considerable thickness (ca. 130 nm) was prepared. SEM image of the micropatterned Cu film on a silicon substrate; scale bar: 10 ,m. [source] Kinetic and DFT Studies on the Photoinduced Desorption of Sulfur from Gold Nanoparticles Loaded on Titanium DioxideCHEMPHYSCHEM, Issue 12 2005Tomokazu Kiyonaga Cleaning poisoned gold catalysts: Kinetic analysis of the photoinduced desorption of sulfur from gold nanoparticles loaded on TiO2 particles in water revealed that the rate constant increases with increasing pH. Photoelectrochemical measurements and DFT calculations led to the conclusion that this reaction results from an upward shift in the Fermi energy of gold nanoparticles by irradiation. The picture shows a high-resolution TEM image of an Au nanoparticle on TiO2. [source] Influence of Metal Nanoparticles on the Electrocatalytic Oxidation of Glucose by Poly(NiIIteta) Modified ElectrodesELECTROANALYSIS, Issue 5 2010Pratap Azad Abstract Conductive polymeric [NiII(teta)]2+ (teta=C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane) films (poly(Ni)) have been deposited on the surface of glassy carbon (GC), Nafion (Nf) modified GC (GC/Nf) and Nf stabilized Ag and Au nanoparticles (NPs) modified GC (GC/Ag-Nf and GC/Au-Nf) electrodes. The cyclic voltammogram of the resulting electrodes, show a well defined redox peak due to oxidation and reduction of poly(Ni) system in 0.1,M NaOH. They show electrocatalytic activity towards the oxidation of glucose. AFM studies reveal the formation of poly(Ni) film on the modified electrodes. Presence of metal NPs increases electron transfer rate and electrocatalytic oxidation current by improving the communication within the Nf and poly(Ni) films. In the presence of metal NPs, 4 fold increase in current for glucose oxidation was observed. [source] A Graphene Oxide,Streptavidin Complex for Biorecognition , Towards Affinity PurificationADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Zunfeng Liu Abstract In our postgenomic era, understanding of protein-protein interactions by characterizing the structure of the corresponding protein complex is becoming increasingly important. An important problem is that many protein complexes are only stable for a few minutes. Dissociation will occur when using the typical, time-consuming purification methods such as tandem affinity purification and multiple chromatographic separations. Therefore, there is an urgent need for a quick and efficient protein-complex purification method for 3D structure characterization. The graphene oxide (GO)·streptavidin complex is prepared via a GO·biotin·streptavidin strategy and used for affinity purification. The complex shows a strong biotin recognition capability and an excellent loading capacity. Capturing biotinylated DNA, fluorophores and Au nanoparticles on the GO·streptavidin complexes demonstrates the usefulness of the GO·streptavidin complex as a docking matrix for affinity purification. GO shows a high transparency towards electron beams, making it specifically well suited for direct imaging by electron microscopy. The captured protein complex can be separated via a filtration process or even via on-grid purification and used directly for single-particle analysis via cryo-electron microscopy. Therefore, the purification, sample preparation, and characterization are rolled into one single step. [source] Self-Assembled In-Plane Growth of Mg2SiO4 Nanowires on Si Substrates Catalyzed by Au NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 15 2010Zhou Zhang Abstract In-plane growth of Mg2SiO4 nanowires on Si substrates is achieved by using a vapor transport method with Au nanoparticles as catalyst. The self-assembly of the as-grown nanowires shows dependence on the substrate orientation, i.e., they are along one, two, and three particular directions on Si (110), (100), and (111) substrates, respectively. Detailed electron microscopy studies suggest that the Si substrates participate in the formation of Mg2SiO4, and the epitaxial growth of the nanowires is confined along the Si <110> directions. This synthesis route is quite reliable, and the dimensions of the Mg2SiO4 nanowires can be well controlled by the experiment parameters. Furthermore, using these nanowires, a lithography-free method is demonstrated to fabricate nanowalls on Si substrates by controlled chemical etching. The Au nanoparticle catalyzed in-plane epitaxial growth of the Mg2SiO4 nanowires hinges on the intimate interactions between substrates, nanoparticles, and nanowires, and our study may help to advance the developments of novel nanomaterials and functional nanodevices. [source] Controllable Shifts in Threshold Voltage of Top-Gate Polymer Field-Effect Transistors for Applications in Organic Nano Floating Gate MemoryADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Kang-Jun Baeg Abstract Organic field-effect transistor (FET) memory is an emerging technology with the potential to realize light-weight, low-cost, flexible charge storage media. Here, solution-processed poly[9,9-dioctylfluorenyl-2,7-diyl]-co-(bithiophene)] (F8T2) nano floating gate memory (NFGM) with a top-gate/bottom-contact device configuration is reported. A reversible shift in the threshold voltage (VTh) and reliable memory characteristics was achieved by the incorporation of thin Au nanoparticles (NPs) as charge storage sites for negative charges (electrons) at the interface between polystyrene and cross-linked poly(4-vinylphenol). The F8T2 NFGM showed relatively high field-effect mobility (µFET) (0.02,cm2 V,1 s,1) for an amorphous semiconducting polymer with a large memory window (ca. 30,V), a high on/off ratio (more than 104) during writing and erasing with an operation voltage of 80,V of gate bias in a relatively short timescale (less than 1,s), and a retention time of a few hours. This top-gated polymer NFGM could be used as an organic transistor memory element for organic flash memory. [source] Hydrophilic Sparse Ionic Monolayer-Protected Metal Nanoparticles: Highly Concentrated Nano-Au and Nano-Ag "Inks" that can be Sintered to Near-Bulk Conductivity at 150,°CADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Bibin T. Anto Here, monolayer-protected gold and silver nanoparticles with extremely high solvent dispersibility (over 200,mg mL,1 in water and glycols) and low coalescence temperature (approximately 150,°C, measured by the percolation transition temperature Tp) are developed, to reach conductivities better than 1,×,105,S cm,1. These materials are suitable for inkjet and other forms of printing on substrates that may be solvent- and/or temperature-sensitive, such as for plastic electronics, and as bus lines for solar and lighting panels. This is achieved using a new concept of the sparse ionic protection monolayer. The metal nanoparticles are initially protected by a two-component mixed ligand shell comprising an ,-functionalized ionic ligand and a labile ligand. These are selectively desorbed to give a sparse shell of the ,-ionic ligands of ca. 25% coverage. Through a systematic study of different monolayer-protected Au nanoparticles using FTIR spectroscopy, supported by XPS and DSC, it is shown that Tp is not determined by thermodynamic size melting or by surface area effects, as previously thought, but by the temperature when ca. 80% of the dense monolayer is eliminated. Therefore, Tp depends on the thermal stability and packing density of the shell, rather than the size of the metal core, while the solubility characteristics depend strongly on the exposed terminal group. [source] Highly Stable Au Nanoparticles with Tunable Spacing and Their Potential Application in Surface Plasmon Resonance BiosensorsADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Shuyan Gao Abstract Colloidal Au-amplified surface plasmon resonance (SPR), like traditional SPR, is typically used to detect binding events on a thin noble metal film. The two major concerns in developing colloidal Au-amplified SPR lie in 1) the instability, manifested as a change in morphology following immersion in organic solvents and aqueous solutions, and 2) the uncontrollable interparticle distance, determining probe spacing and inducing steric hindrance between neighboring probe molecules. This may introduce uncertainties into such detecting techniques, degrade the sensitivity, and become the barricade hampering colloidal Au-based transducers from applications in sensing. In this paper, colloidal Au-amplified SPR transducers are produced by using ultrathin Au/Al2O3 nanocomposite films via a radio frequency magnetron co-sputtering method. Deposited Au/Al2O3 nanocomposite films exhibit superior stability, and average interparticle distances between Au nanoparticles with similar average sizes can be tuned by changing surface coverage. These characteristics are ascribed to the spacer function and rim confinement of dielectric Al2O3 and highlight their advantages for application in optimal nanoparticle-amplified SPR, especially when the probe size is smaller than the target molecule size. This importance is demonstrated here for the binding of protein (streptavidin) targets to the probe (biotin) surface. In this case, the dielectric matrix Al2O3 is a main contributor, behaving as a spacer, tuning the concentration of Au nanoparticles, and manipulating the average interparticle distance, and thus guaranteeing an appropriate number of biotin molecules and expected near-field coupling to obtain optimal sensing performance. [source] Repeated Transfer of Colloidal Patterns by Using Reversible Buckling ProcessADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Dong Choon Hyun Abstract The reversible nature of buckling is employed to repeatedly transfer colloids assembled in buckling patterns to flat surfaces. The cycle of colloidal loading,transfer,buckling is repeatedly carried out to fabricate the same colloidal patterns. The key to success is the reduction in the amplitude of the buckling patterns to a few nanometers as well as the recovery of initial buckling patterns after repeated stretching. The reduced buckling amplitude by poststretching or thermal annealing embosses the colloids assembled in the trenches of the buckling patterns, which enables the transfer regardless of the size, species, or layer thickness of the particles. This report demonstrates various transferred patterns composed of colloidal crystals, fluorescence hydrogel colloids, Au nanoparticles, and iron oxide magnetic particles. Since the process does not require surface modification of the colloids, it can be used to fabricate any colloidal patterns. [source] Formation of Gold and Silver Nanoparticle Arrays and Thin Shells on Mesostructured Silica Nanofibers,ADVANCED FUNCTIONAL MATERIALS, Issue 16 2007S. Zhang Abstract Mesostructured silica nanofibers synthesized in high yields with cetyltrimethylammonium bromide as the structure-directing agent in HBr solutions are used as templates for the assembly of Au and Ag nanoparticles and the formation of thin Au shells along the fiber axis. Presynthesized spherical Au and Ag nanoparticles are adsorbed in varying amounts onto the silica nanofibers through bifunctional linking molecules. Nonspherical Au nanoparticles with sharp tips are synthesized on the nanofibers through a seed-mediated growth approach. The number density of nonspherical Au nanoparticles is controlled by varying the amount of seeded nanofibers relative to the amount of supplied Au precursor. This seed-mediated growth is further used to form continuous Au shells around the silica nanofibers. Both the Au- and Ag-nanoparticle/silica-nanofiber hybrid nanostructures and silica/Au core/shell fibers exhibit extinction spectra that are distinct from the spectra of Au and Ag nanoparticles in solution, indicating the presence of new surface plasmon resonance modes in the silica/Au core/shell fibers and surface plasmon coupling between closely spaced metal nanoparticles assembled on silica nanofibers. Spherical Au- and Ag-nanoparticle/silica-nanofiber hybrid nanostructures are further used as substrates for surface-enhanced Raman spectroscopy, and the enhancement factors of the Raman signals obtained on the Ag-nanoparticle/silica-nanofiber hybrid nanostructures are 2,×,105 for 4-mercaptobenzoic acid and 4-mercaptophenol and 7,×,107 for rhodamine,B isothiocyanate. These hybrid nanostructures are therefore potentially useful for ultrasensitive chemical and biological sensing by using molecular vibrational signatures. [source] Vapor Sorption and Electrical Response of Au-Nanoparticle, Dendrimer Composites,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007N. Krasteva Abstract Films comprising Au nanoparticles and polyphenylene dendrimers (first and second generation) are deposited onto transducer substrates via layer-by-layer self-assembly and characterized by atomic force microscopy and X-ray photoelectron spectroscopy. Their sorption behavior is studied by measuring the uptake of solvents from the vapor phase with quartz crystal microbalances (QCMs). The resistance of the films is simultaneously monitored. Both sensor types, QCMs and chemiresistors, give qualitatively very similar response isotherms that are consistent with a combination of Henry- and Langmuir-type sorption processes. The sorption-induced increase in relative differential resistance scales linearly with the amount of analyte accumulated in the films. This result is in general agreement with an activated tunneling process for charge transport, if little swelling and only small changes in the permittivity of the film occur during analyte sorption (a first-order approximation). The relative sensitivity of the films to different solvents decreases in the order toluene,,,tetrachloroethylene,>,1-propanol,,,water. Films containing the larger second-generation dendrimers show higher sensitivity than films containing first-generation dendrimers. [source] UV-Light-Driven Immobilization of Surface-Functionalized Oxide Nanocrystals onto Silicon,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2007E. Fanizza Abstract TiO2 nanorods (NRs) and ,-Fe2O3 nanocrystals (NCs) passivated with unsaturated long-chain carboxylic acids, namely 10-undecylenic acid (10UDA) and oleic acid (OLEA), are covalently anchored to Si(100) at room temperature by UV-light-driven reaction of hydrogenated silicon with the carbon,carbon double bond (,CC,) moieties of the capping surfactants. The high reactivity of vinyl groups towards Si provides a general tool for attaching particles of both materials via Si,C bonds. Interestingly, TiO2 NRs were efficiently attached to silicon even when capped by OLEA. This latter finding has been explained by a photocatalytic mechanism involving the primary role of hydroxyl radicals that can be generated upon bandgap TiO2 photoexcitation with UV light. The increased oxide coverage achievable on Si opens access to further surface manipulation, as demonstrated by the possibility of depositing an additional film of Au nanoparticles onto TiO2 via TiO2 -catalyzed visible-light-driven reduction of aqueous AuCl4, ions. Extensive morphological and chemical characterization of the obtained NC-functionalized Si substrates is provided to support the effectiveness of proposed photochemical approaches. [source] Fabrication of Surface Plasmon-Coupled Si Nanodots in Au-Embedded Silicon Oxide NanowiresADVANCED MATERIALS, Issue 22 2010Gyeong-Su Park High-density amorphous silicon nanodots are easily produced by irradiating gold-nanoparticle-embedded silicon oxide nanowires with a low-intensity electron beam. The optical characteristics of Si nanodots in the vicinity of gold nanoparticles exhibit evidence of strong coupling to the surface plasmon resonance of the Au nanoparticles, as manifested by their markedly enhanced electron-induced excitation in our monochromated scanning transmission electron microscopy,electron energy-loss spectroscopy measurements. [source] Seed-Mediated Synthesis of Truncated Gold Decahedrons with a AuCl/Oleylamine Complex as PrecursorADVANCED MATERIALS, Issue 17 2010Yanyun Ma A seed-mediated growth method is described for the synthesis of a novel type of Au nanoparticles,truncated decahedrons with a pentagonal, platelike structure (see figure). The precursor is based on the AuCl/oleylamine complex. TEM analyses reveal that the truncated Au nanoparticle has two types of truncation: one is parallel to the five-fold axis and the other is perpendicular to the five-fold axis. [source] Nanocomposite Films Assembled from Genetically Engineered Filamentous Viruses and Gold Nanoparticles: Nanoarchitecture- and Humidity-Tunable Surface Plasmon Resonance SpectraADVANCED MATERIALS, Issue 9 2009Aihua Liu Nanocomposite films are prepared by layer-by-layer (LBL) assembly of cationic genetically engineered rodlike nontoxic viruses and anionic spherical Au nanoparticles. The cationic viruses electrostatically interact with the anionic Au nanoparticles to drive the LBL assembly. The nanocomposite films exhibit humidity-dependent surface plasmon resonance spectra (see figure). [source] Synthesis of Functionalized Au Nanoparticles for Protein Detection,ADVANCED MATERIALS, Issue 3 2008R. Jana Aptamer and antibody functionalized Au nanoparticles are synthesized and used for protein detection (see figure). These particles are highly water soluble and as small as 10 nm. However, they are enlarged after a protein binding event to enhance signal sensitivity. A conventional western blot protocol is used to enable detection of the proteins with nanomolar sensitivity, with the naked eye. [source] DNA-Wrapped Single Walled Carbon Nanotubes as Rigid Templates for Assembling Linear Gold Nanoparticle Arrays,ADVANCED MATERIALS, Issue 11 2007X. Han Nanotube templates assembly: Water-soluble conjugates between gold nanoparticles and DNA-wrapped single-walled carbon nanotubes (SWNTs), as shown in the figure, are constructed based on a self-assembly strategy that does not require any chemical modifications to the sidewalls of the SWNTs, which minimizes the possibility of changes to their structure and properties. The success of assembling Au nanoparticles (AuNPs) onto SWNTs paves a way for further decoration of AuNPs on SWNTs to achieve multifunctionalities. [source] When Small Is Different: Some Recent Advances in Concepts and Applications of Nanoscale Phenomena,ADVANCED MATERIALS, Issue 5 2007G. Hodes Abstract Reduction in size often does more than simply make things smaller. There are many properties of materials that undergo qualitative, often sudden, changes below a certain size scale. This Report first describes some of these size-dependent properties. Following this general description, recent developments in a number of selected topics in nanoscience are covered. These topics are: luminescence from Au nanoparticles; Si (and related) nanoparticle luminescence; modification of optical absorption by surface adsorption on nanoparticles; and transistors (and some other devices) based on nanotubes and nanowires. [source] Biologically Programmed Synthesis of Bimetallic Nanostructures,ADVANCED MATERIALS, Issue 15 2006M. Slocik Catalytic bimetallic nanoparticles are synthesized by exploiting the interaction between peptides and inorganic materials to program the peptide sequence such that it can serve as a template in the synthesis of gold nanoparticles as well as direct the binding to Pd ions to the surface of the Au nanoparticles (see figure). [source] Peptide Nanotubes: Simple Separation Using Size-Exclusion Columns and Use as Templates for Fabricating One-Dimensional Single Chains of Au Nanoparticles,ADVANCED MATERIALS, Issue 14 2005X. Gao Straight single chains of Au nanoparticles have been synthesized using 10,nm diameter peptide nanotubes as templates (see Figure). The 6,nm Au nanoparticles grow in the gaps between the synthetic peptide coating the nanotubes which regulates the size, dispersity, interparticle distance, and crystallinity of the nanoparticles. The use of longer nanotubes results in longer chains. [source] Encapsulation of nanomaterials using an intermediary layer cross-linkable ABC triblock copolymerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2009Jin Sook Kim Abstract For the preparation of core-shell nanoparticles containing functional nanomaterials, a photo-cross-linkable amphiphilic ABC triblock copolymer, poly(ethylene glycol)- b -poly(2-cinnamoyloxyethyl methacrylate)- b -poly(methyl methacrylate) (PEG-PCEMA-PMMA), was synthesized. This triblock copolymer was then used to encapsulate Au nanoparticles or pyrene. The triblock copolymer of PEG- b -poly(2-hydroxyethyl methacrylate)- b -PMMA (PEG-PHEMA-PMMA) (Mn = 15,800 g/mol, Mw/Mn = 1.58) was first synthesized by activators generated by electron transfer atom transfer radical polymerization. Its middle block was then functionalized with cinnamoyl chloride. The degrees of polymerization of the PEG, PHEMA, and PMMA blocks were 45, 13, and 98, respectively. PMMA-tethered Au nanoparticles (with an average diameter of 3.0 nm) or pyrene was successfully encapsulated within the PEG-PCEMA-PMMA micelles. The intermediary layers of the micelles were then cross-linked by UV irradiation. The spherical structures of the PEG-PCEMA-PMMA micelles containing Au nanoparticles or pyrene were not changed by the photo-cross-linking process and they showed excellent colloidal stability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4963,4970, 2009 [source] A Novel Route for Fabricating Metal-Polymer Composite Nanoparticles with Phase-Separated StructuresMACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2010Hiroshi Yabu Abstract Au nanoparticles (NPs) and polymer composite particles with phase-separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block-copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core-shell) were controlled by changing the combination of polymers having differing hydrophobicity. [source] Decorating Polypyrrole Nanotubes with Au Nanoparticles by an In Situ Reduction ProcessMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2009Jingjing Xu Abstract Au nanoparticle-decorated polypyrrole nanotubes (defined as PPy/Au nanocomposites) are prepared by an in situ reduction process. Polypyrrole (PPy) nanotubes are prepared by a self-degraded template method, and Au nanoparticles are deposited in situ by the reduction of HAuCl4. The size and uniformity of the Au nanoparticles that decorate the PPy nanotubes can be controlled by adjusting the experimental conditions, such as the stabilizers used and the reaction temperature. The morphologies and optical properties of the nanocomposites have been characterized by scanning electron microscopy, transmission electron microscopy, UV-vis, and FT-IR spectroscopy. Conductivity measurements show that the conductivities of the nanocomposites decrease with a decrease of temperature, and the conductivity,temperature relationship obeys the quasi-one dimensional variable range hopping model. [source] Scaling behavior of plasmon coupling in Au and ReO3 nanoparticles incorporated in polymer matricesPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010Urmimala Maitra Abstract Polymer nanocomposites containing different concentrations of Au nanoparticles have been investigated by small angle X-ray scattering and electronic absorption spectroscopy. The variation in the surface plasmon resonance (SPR) band of Au nanoparticles with concentration is described by a scaling law. The variation in the plasmon band of ReO3 nanoparticles embedded in polymers also follows a similar scaling law. Distance dependence of plasmon coupling in polymer composites of metal nanoparticles. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] PS-NH2 + PMMA-COOH blend: A promising substrate material for the deposition of densely packed gold nanoparticlesPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 3-4 2010D. K. Bo Abstract Densely packed gold nanoparticles with narrow size distribution were fabricated by pulsed laser deposition using a blend of amino-terminated polystyrene (PS-NH2) and carboxyl-terminated polymethylmethacrylate (PMMA-COOH) as a deposition substrate. Transmission electron microscopy showed spherical Au nanoparticles with an average size of 5 nm. UV,vis absorption spectra of the Au/blend nanocomposite films exhibited a strong resonance band at 658 nm. The analyses of the spectrum using the effective medium Bergman theory showed that the nanocomposite is comprised of isolated and randomly arranged nanoparticles. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical nanometrology of Au nanoparticles on a multilayer filmPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2008Yia-Chung Chang Abstract Ellipsometric measurements coupled with efficient theoretical modeling are used to determine the size and distribution density of Au nanoparticles on a multilayer film. The rigorous coupled-wave analysis (RCWA) and finiteelement Green's function method were used to model the polarization-dependent reflectivity, and the model calculations are in reasonable agreement with the measurements. This demonstrates that the spectroscopic ellipsometry could be a useful optical tool for nondestructive nanometrology. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Purification,chemical structure,electrical property relationship in gold nanoparticle liquids,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2010Robert I. MacCuspie Abstract Macroscopic assemblies of nanoparticles with fluid like characteristics, i.e. nanoparticle liquids (NPLs), are a new class of materials that exhibit unique properties compared with dispersions of nanoparticles in a molecularly distinct matrix phase. By focusing on reaction ratios, techniques to maximize concentration of reactants and quantification of chemical content during washing steps, a high degree of control over the purity of NPLs was maintained while allowing for easy scalability in batch sizes and synthesis throughput. A range of tertiary amines and quaternary ammoniums were used to successfully synthesize Au NPLs from a range of Au nanoparticles with nominal diameters from 6 to 20 nm and initially stabilized with either citrate or dodecanethiol. Stable Au NPLs after purification exhibited a sub-equivalence ratio of canopy to ligand molecules within the corona. This small canopy density most likely arose from the incommensurate areal density of anionic charge within the ligand shell relative to the larger size of the cationic canopy molecule, resulting in a population of cation,anion pairs too weakly bound to be retained in the initial assembly of the canopy post-purification. Finally, increasing either the volume fraction or molecular weight of the canopy was found to increase exponentially the electrical resistance of the bulk NPLs. Removal of excess canopy molecules created a conductive Au NPL that improved hot-current switching durability by at least two orders of magnitude beyond prior reports. Published in 2010 by John Wiley & Sons, Ltd. [source] The Response of Articular Chondrocytes to Type II Collagen,Au NanocompositesARTIFICIAL ORGANS, Issue 12 2007Shan-hui Hsu Abstract:, The nanocomposites (denoted "CII,Au") of porcine type II collagen (CII) with 0.05, 0.1, 0.5, 1, or 2.5% (wt/wt) Au nanoparticles (,5 nm) were fabricated for potential use in cartilage tissue engineering. Au formed clusters on the surface of all nanocomposites and appeared to distribute along the collagen fibrils inside the matrix. The addition of Au at low concentrations (,0.5%) increased the modulus and viscosity, as well as the free radical-scavenging ability. These effects decreased at higher concentrations of Au. The chondrocytes on CII,Au became spindle-like with lamellipodia formation. Cell proliferation on CII,Au 0.1% was promoted. Nitric oxide (NO) in the culture medium was reduced by CII,Au 0.05% and CII,Au 0.1%. Type I collagen, aggrecan, and Sox 9 gene expressions increased with an increased Au content, but slightly decreased at 2.5% Au. There was no significant difference in the CII gene expression. The cellular uptake of Au was observed but less than that which occurred when 10 ppm of Au was added in culture medium. Chondrocytes cultured with ,10 ppm of Au nanoparticles showed neither cytotoxicity nor change in gene expression. Au at an appropriate amount could be well dispersed in CII, and enhanced the material modulus, antioxidant effect, as well as the chondrocyte growth and matrix production. [source] Adsorption of 1,3-Benzenedithiol and 1,3-Benzenedimethanethiol on Gold Surfaces,CHEMPHYSCHEM, Issue 12 2008Jong Kuk Lim Dr. Abstract The adsorption characteristics of 1,3-benzenedithiol (1,3-BDT) and 1,3-benzenedimethanethiol (1,3-BDMT) on Au surfaces are investigated by means of surface-enhanced Raman scattering, UV/Vis absorption spectroscopy, and cyclic voltammetry (CV). 1,3-BDMT is found to adsorb via two S,Au linkages at concentrations below monolayer coverage, but to have an upright geometry as the concentration increases on Au nanoparticles. On the other hand, 1,3-BDT is found to adsorb by forming two S,Au linkages, regardless of concentration, based on the disappearance of the ,(SH)free stretching band. Because of the absence of the methylene unit, 1,3-BDT appeares not to self-assemble efficiently on Au surfaces. The UV/Vis absorption spectroscopy and CV techniques are also applied to check the formation of self-assembled monolayers of 1,3-BDT and 1,3-BDMT on Au. Density functional theory calculations based on a simple adsorption model using an Au8 cluster are performed to better understand the nature of the adsorption characteristics of 1,3-BDT and 1,3-BDMT on Au surfaces. [source] | ||||||||||||||||||||||||||||