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The adsorption of 3-methylthiophene on planar and nanoparticle Au surfaces is investigated. The resulting systems are compared with a benchmark system based on 1-decanethiol.

Monodisperse hexapeptides having lipoic acid coupled to the N-terminus were self-assembled on gold substrates. X-ray photoelectron spectroscopy (XPS), angle dependent XPS, and grazing angle Fourier transfer infrared reflection-absorption spectroscopy (FTIR-RAS) were used to investigate the self-assembled monolayer (SAM) film compositions.

A single step process for the synthesis and self-assembly of ca. 3nm gold nanoparticles by 4-aminothiophenol (ATP) in water -DMF is demonstrated. The results indicate the involvement of both ithiol and amine groups in the reduction of AuCl(super -) ions, which simultaneously compete for attachment on the surface of gold nanoparticles.

Pyrene chromophores functionalized to gold nanoparticles using methylene groups of varying chain length were prepared. A detailed investigation was conducted on the nanoparticle-chromophore and interchromophore interactions. The emission spectra studies indicated that the local environment close to the surface of Au nanoparticle was more polar compared to the bulk medium.

The self-assembled monolayers (SAMs) of dodecanethiol (DDT), octadecanethiol (ODT), and resorcinarene C10 tetrasulfide (RC10TS) on Au(111) are characterized by scanning tunneling spectroscopy. The leakage current densities across DDT and RC10TS SAMs on Au are estimated.

The coadsorption properties of carbon monoxide and oxygen on gold clusters reveals that instead of competitive coadsorption, cooperative coadsorption with an increase in the adsorption of both is observed. Furthermore, the coadsorption causes new peaks in the mass spectrum, which may be due to the carbon dioxide released.

A unique, sensitive, and highly specific immunoassay system for antibodies using gold nanoparticles has been developed. The assay is based on the aggregation of gold nanoparticles that are coated with protein antigens in the presence of their corresponding antibodies. The aggregation of the gold nanoparticles results in an absorption change at 620 nm that is monitored using an absorption plate reader. To demonstrate the analytical capabilities of the new technique, monodispersed protein A-coated gold particles, averaging 10 nm in diameter, were used to determine the level of anti-protein A in serum samples. The effects of the pH, the temperature, and the concentration of protein A-coated gold nanoparticles on the sensitivity of the assay were investigated using transmission electron microscopy (TEM) and UV/vis absorption spectroscopy. A dynamic range of 2 orders of magnitude and a limit of detection of 1 [micro]g/mL of anti-protein A were observed. The new technique could be used for fast, high-throughput screening of antibodies in clinical diagnostic applications.

Results show that in Au/ZnSe heterostructures annealing causes gold diffusion into the ZnSe and deposition of gold grains on the surfaces. Data on backscattering signal from the grains show that the signal overlaps the signal from diffused gold at a depth of 100 mm beyond the crystal interface.

Temperature-programmed reaction investigations of the catalyzed combustion of CO on size-selected small monodispersed Au(sub n) gold clusters supported on magnesia, and first-principle simulations, indicate the microscopic origins of unusual catalytic activity. Au8 is the smallest catalytically active size.

The influence of the aspect ratio and the medium dielectric constant in the optical absorption spectra of gold nanorods has been studied. The nanorods have been prepared in micelles by the electrochemical method using an electrochemical cell with gold as the anode and platinum plate as the cathode. Results indicate that theoretical computations can also prove the linear relationship between the absorption maximum of the longitudinal plasmon resonance and the mean aspect ratio. Numerical calculations also show that the plasmon resonance is linearly dependent on the medium dielectric constant for a given aspect ratio.

Research was conducted to examine the adsorption or bonding geometries of pure adlayers of several N(sub x)O(sub y) species, nitrogen dioxide, dinitrogen trioxide and dinitrogen tetroxide, on Au(111) using infrared reflection-absorption spectroscopy. New information on the reacting species in condensed films of NO2 + H2O that lead to oxygen formation on the Au(111) surface were also obtained. Results demonstrate that the formation of the nascent intermediates that lead to oxygen deposition on the Au(111) surface is not due to the presence of the Au surface atoms.

The steric aspects of monolayer-protected gold clusters (MPCs) are addressed, based on SN2 reactivity of omega-bromoalkanethiolate/Au MPCs having primary amines of grade steric bulk. Rate of cyanide-induced decomposition of gold cores ws taken into consideration, and solution infrared spectroscopy was used to examine disorder features of alkanethiolate ligand monolayers on Au MPCs.

The electrochemical formation of contacts between platinum or gold electrodes with the organic charge-transfer salts tetrathiafulvalenium bromide (TTFBr(sub x), x = 0.74-0.79) or bis(tetramethyltetraselenafulvalenium) perchlorate ((TMTSF)2ClO4) was investigated. To this end, conducting crystals of the charge-transfer salts were examined. The needle-shaped crystals were prepared between pairs of platinum or gold electrodes by oxidative electrodeposition. An electrical connection resulted when a crystal growing from one electrode encountered the second electrode.

The synthesis and structural characterization of mono- and multilayers of cadmium sulfide (CdS) nanoparticles on a gold substrate were investigated. CdS-nanoparticle mono- and multilayers were fabricated by an alternate immersion of the substrate into ethanolic solutions of dithiol. A layer-by-layer structure of dithiol self-assembled and cadmium sulfide monolayers was confirmed with the aid of Fourier transform infrared reflection-absorption spectroscopy and X-ray photoelectron spectroscopy at each stage of fabrication of the composite film.

The substitution of the chlorine ligand to give [Au2X2(mu-dppf)] (X = Br, I) results from the reaction of [Au2Cl2(mu-dppf)] (dppf = 1,1'-bis(diphenylphosphino)ferrocene) with KX in acetone. The 31P{1H] NMR spectra indicate a singlet for the equivalent phosphorous atoms. Three multiplets with an intensity ratio 1:1:5 appear in the 1H NMR spectra. The crystal structure of [Au3(mu-3-Spy)(mu-dppf)(PPh2Me)](OTf)2 is the first example where a pyridinethiolate ligand bridges three gold atoms.

Surface characterization techniques were utilized to analyze the formation of crystalline, nanometer-scale -(CH2)x-clusters on evaporated gold (Au) surfaces. Results have shown that the defect sites on the Au surface serve as the niche for the initial nucleation of the clusters which then progresses as it crosses over to an increased surface coverage with increasing diazomethane decomposition.

An attenuated total reflection (ATR) method to excite the surface plasmon polariton (SPP) was applied to gold and copper to improve the sensitivity level of classical Raman spectroscopy. Reflectivity and Raman band intensity from copper phthalocyanine (CuPc) adsorbates on these metals were measured in an Otto configuration as a function of the angle of incidence and gap size at various excitation wavelengths. The SPP's on gold and copper were most efficiently excited at a wavelength of 632.8 nm according to the sufficiently large real part and the small imaginary part in the dielectric constants. It yields an enhancement factor of approximately 50 and 23 for Raman band intensity from CuPc 6 nm thick on gold and copper, respectively. Furthermore the significantly larger enhancement factor of [approximately]100 was obtained for a self-assembled monolayer of p-nitrothiophenol on gold at 632.8-nm excitation, probably owing to its smaller imaginary part value. It enabled us to observe the electrochemical reduction to p-aminothiophenol in situ and gave clear evidence of charge transfer resonance as observed for the silver system. Conclusively, the ATR-SPP method is essential to enhancing a quite weak Raman signal from adsorbates on gold and copper surfaces as well as silver. Key words: ATR Raman spectroscopy, surface plasmon polariton, in situ highly sensitive analysis

Gold complexes of the type (P'AuX) (P = 2-MBPA; X = Cl (1); X = 2-pyS (5)), containing chiral phosphine ligands are synthesized and characterized by 13C, 1H and 31P NMR spectroscopy. X-ray analysis indicates that the linear arrangement of pyrano rings and P-Au-X of 1 and 5 form a distorted chair conformation. Compound 1 is stable in CDCl3 solution for few hours only. The 2-pyS anion in complex 5 serves as a thiolate and is coordinated to the metal center in distinct structural modes.

Two gold-carborane compounds having the same electron configuration, 1,2-(AuPPh3)2-1,2-C2B10H10 and 1,1'-(AuPPh3)2- 2-(1',2'-C2B10H10)-1,2-C2B10H10 were prepared and compared using nuclear magnetic resonance and crystallographic techniques. The first exhibited no aurophilic interaction between its gold centers. In contrast, the second demonstrated an aurophilic interaction of 11 kcal/mol.

The monomeric gold(I) complexes containing thiolate and phosphine ligands exhibit luminescence in the solid state at low temperatures, attributed to a ligand to metal charge transfer transition from the sulfur of the thiolate to the gold center. The long lifetimes and large Stokes shifts indicate that the emission is phosphorescence. The presence of gold-gold interaction between the adjacent molecules and the substituents on the thiolate ligand affect the position of emission maxima. The experimental procedure for the syntheses of these gold complexes is discussed.

Hydride ligands in cationic clusters were studied in terms of their structural and bonding characteristics. These included (triphos)MH2(Au(PPh3))3 2+ triphos = CH3C(CH2PPh2)3; M = Rh and Ir and (triphos)RuH3(Au(PPh3)3)2+. Spectral analysis showed that the phosphorus atoms of the triphos ligands and the PPh3 molecules are inequivalent while the corresponding donors in the trihydrido complex are equivalent. Mossbauer spectra showed distinct assymetry of measured doublet patterns which could possibly be due to the presence of overlapping doublets.

The inclusion of a An layer in the magnetic tunnel junction structure Fe/MgO/CoFe substantially alters the magnetic properties. In this work we use zero field 59Co NMR to see if these changes in magnetic properties are correlated with changes in the local atomic environment. The technique of spin-echo NMR allows the effective magnetic field (hyperfine field) at the nucleus to be determined and so provides information on the local atomic environments including strain effects and magnetic moments. The results show that the local atomic environment of Co does not change significantly, however the r.f. power required to obtain the maximum signal is substantially different when the Au layer is included showing that the r.f. electronic enhancement factor changes appreciably. Index Terms - Magnetic tunnel junctions, NMR, Thin films.

The lowest bandgap, soluble, spray-processable polymer is produced by combining a strong donor, tris(dodecyloxy)phenyl)-dithieno[3,2-b:2',3'-d-pyrrole, with a strong acceptor, 4,8-dithien-2-yl-2[[lambda].sup.4][[delta].sup.2]-benzo[1,2-c;4,5-c']bis[1,2,5]thiadiazole. Transmission/absorption spectroscopy on single-walled carbon nanotubes (SWCNTs) and reflectance spectroscopy on gold are used for estimating the optical bandgap.

Zipper assembly is introduced as a simple and general approach to complex functional architectures on conducting surfaces. Steady zipper growth with mismatched rods and the absence of zipper growth with matched rods are shown on gold nanoparticles and gold electrodes by using photocurrent generation, naphthalenediimide (NDI) absorption and shift of the surface plasmon resonance (SPR) band.

The low-temperature electron transport properties of alkyl monolayers that use dithiocarbamate and thiolate attachment strategies to gold are compared. Inelastic electron tunneling spectroscopy (IETS) and current-voltage analysis of the device have shown an increase in current density when using dithiocarbamate attachment to gold when compared to alkanethiolate molecules of similar length.

The synthesis of a series of tiopronin monolayer-protected gold nanoclusters (MPCs) and their postsynthesis peptide ligand place-exchange reactions are studied using electrospray ionization time-of-flight mass spectrometry and gel permeation chromatography. The study result shows the first experimental validation of cyclic gold(I)-thiolate tetramer formation in tiopronin monolayer-protected nanoclusters and reports the chemical pathway leading to their formation in MPCs.

The near-infrared photoluminescence of monolayer-protected Au38 and Au140 clusters (MPCs) is intensified with exchange of nonpolar ligands by more polar thiolate ligands. The observations are consistent with sensitivity of the luminescence mechanism to any factor that enhances the electronic polarization of the bonds between the Au core atoms and their thiolate ligands.

A study of the molecular packing of ligand shells on gold nanoparticles is presented based on the analysis of scanning tunneling microscopy images. It is shown that the packing of a self-assembled monolayer composed solely of octanethiols on gold nanoparticles depends on the particle's diameter with an average headgroup spacing of 5.4 Angstrom, which is different from that of similar monolayers formed on flat Au(111) surfaces (5.0 Angstrom).

Small gold particles with N-isobutyryl-D-cysteine and N-isobutyryl-L-cysteine, respectively are prepared, and their optical activity in the infrared and UV-vis is investigated. These particles with a mean particle size smaller than 2 nm are highly soluble in water and are amenable to chiroptical techniques such as vibrational circular dichroism and circular dichroism.

A simple procedure to assemble gold nanoparticles into hallow tubular morphology with micrometer scale is described, wherein the citrate molecule is used not only as a reducing and capping agent, but also as an assembling template. The results reveal that the microtubes both before and after electroless plating could be used as surface-enhanced Raman scattering (SERS) substrates and the microtubes after electroless plating have displayed excellent enhancement ability.

The effect of dielectric core and embedding medium on the local field enhancement for gold nanoshells was investigated. It was noticed that increasing the dielectric constant of dielectric core leads the shorter wavelength local field factor peak to red-shift and increase nonlinearly, whereas the longer wavelength peak redshifts and decreases nonlinearly.

The effect of aggregation in gold nanoparticles on their ultrafast electron-phonon relaxation dynamics measured by femtosecond transient absorption pump-probe spectroscopy is reported. Results strongly suggest the presence of intercolloid electronic coupling within the nanoparticle aggregates, besides the well-known dipolar plasmon coupling.

A demonstration showing that arrays of nanoholes could be used to fabricate analytical devices for enhanced fluorescence measurements, with fluorescence enhancement through surface plasmons (SP) resonance being tunable through the periodicity of the array is presented. Results suggest that arrays of nanoholes in Au films at resonance could improve both the sensitivity and the limit of detection of fluorescence-based analysis.

The conclusion that the depolarized ratio of the scattered intensities, I(sub vh)/I(sub vv), is shown to exceed 1/3, for nonspherical plasmon resonant metal particles. Gold nanospheres and nanorods are used to measure the extinction and static light scattering spectra as well as depolarized ratio of He-Ne laser light scattering spectra.

A procedure for the preparation of high aspect ratio Au nanowires utilizing gold electroless reduction in the hexagonally ordered, thiol-modified nanosized channels of the SBA-15 material is reported. The results show that the growth of the Au nanowires is templated by the channel structure of the SBA-15 material.

The use of size-selected gold nanoparticles (AuNPs) as low concentration and selective matrices for the ionization of biomolecules is described in contrast with measurements of ions and clusters formed by laser desorption ionization of AuNP. The utility of AuNPs was examined using size distributions of 2,5, and 10 nm.

A novel strategy for the reconstruction of a membrane protein monolayer in a lipid layer on a solid support is pursued. Quantum mechanical calculations are used to assign the experimentally observed vibrational frequencies of the various steps to normal modes.

It is shown that Au particles having diameters of less than 2.2nm can be extracted from within the interior of PAMAM dendimers using n-alkanethiol extractants. The extraction rate is fastest for the lowest generation dendimers, the smallest nanoparticles, and the shortest chain-length n-alkanethiols.

The presence of photoinduced sulfur desorption from the surfaces of the metal oxide-supported Au nanoparticles in water at room temperature is identified. It is demonstrated that the phenomenon is applicable to the low-temperature cleaning of sulfur-poised metal catalysts.

The construction of a novel nanosensor, based on the real-time determination of swelling of responsive ultrathin polymer brushes by an inexpensive, simple, efficient, and highly sensitive technique of gold nanoparticle enhanced transmission surface plasmon resonance (T-SPR) spectroscopy is described. T-SPR spectroscopy is based on the exploitation of localized surface plasmon resonance.

A new approach to achieving photothermally modulated volume transitions in submicrometer hydrogel particles in the near-IR spectral range is reported. In the experiment, hybrid gold microgels comprised of temperature-responsive copolymer and gold nanorods (NRs) designed to absorb near-IR light were used.

In-situ scanning tunneling microscopy (STM) and cyclic voltammetry are used to study conformational-related adlayer structures of four calixarenes, three calix[4]arenes with specific conformations and one calix[6]arene. The results show that the conformation of calixarenes can be immobilized on the Au(111) surface through adsorption.

The organization of dodecanethiol- stabilized Au nanoparticles prepared by two different synthetic routes into nanocrystal superlattices with different packing structures despite similarity in nanoparticle size is demonstrated. Findings stated that Au nanoparticles obtained by bulk gold vaporization (SMAD procedure) has primarily defective core structures, lack faceting and behave like hard spheres.

A DOE sponsored workshop organized to discuss the status of our understanding of charge transfer processes on the nanoscale is reported and the research and other needs for progress in nanoscience and nanotechnology are identified. The findings state that chemistry can progress in an Edisonian manner but the greatest and most satisfying advances have come through the knowledge of molecular structure and insights from principles based on that knowledge.

The effect of temperature on the vibrational spectrum and electrochemical properties of a monolayer of hexadecanethiol adsorbed on Au(111) in an alkaline aqueous solution is examined. The result suggested that the properties of self-assembled monolayers of alkanethiols in contrast with electrolyte solutions change with temperature.

CO adsorption and oxidation over Au/Al(sub 2)O(sub 3) were studied by infrared (IR) spectroscopy at 150 K and two kinds of adsorbed CO on ultrafine gold particles of Au/Al(sub 2)O(sub 3) catalyst were observed at 150 K. The oxidation of reversible CO and the others did not convert the irreversible CO to CO(sub 2).