We demonstrate localized electrodeposition of anisotropic metal nanoobjects, namely Au nanorods (GNR), on indium tin oxide (ITO) using scanning electrochemical microscopy (SECM). A gold microelectrode was the source of the gold ions whereby double pulse chronoamperometry was employed to generate initially Au seeds which were further grown under controlled conditions. The distance between the microelectrode and the ITO surface as well as the different experimental parameters (electrodeposition regime, solution composition and temperature) were optimized to produce faceted gold seeds with the required characteristics (size and distribution). Colloidal chemical synthesis was successfully exploited for better understanding the role of the surfactant and different additives in breaking the crystallographic symmetry and anisotropic growth of GNR. Experiments performed in a conventional three-electrode cell revealed the most appropriate electrochemical conditions allowing high yield synthesis of nanorods with well-defined shape as well as nanocubes and bipyramids.[on SciFinder (R)]

We demonstrate localized electrodeposition of anisotropic metal nanoobjects, namely Au nanorods (GNR), on indium tin oxide (ITO) using scanning electrochem. microscopy (SECM). A gold microelectrode was the source of the gold ions whereby double pulse chronoamperometry was employed to generate initially Au seeds which were further grown under controlled conditions. The distance between the microelectrode and the ITO surface as well as the different exptl. parameters (electrodeposition regime, soln. compn. and temp.) were optimized to produce faceted gold seeds with the required characteristics (size and distribution). Colloidal chem. synthesis was successfully exploited for better understanding the role of the surfactant and different additives in breaking the crystallog. symmetry and anisotropic growth of GNR. Expts. performed in a conventional three-electrode cell revealed the most appropriate electrochem. conditions allowing high yield synthesis of nanorods with well-defined shape as well as nanocubes and bipyramids. [on SciFinder(R)]

An approach for patterning surfaces with prepd. nanoparticles is described. Chitosan-stabilized gold nanoparticles (Au/chitosan NPs) were locally deposited on stainless steel (StSt), indium tin oxide (ITO), and highly-ordered pyrolytic graphite (HOPG). Deposition was driven by local pH gradient formed between a surface and a scanning electrochem. microscopy tip set in the direct mode. The pH at the substrate was increased upon biasing the surface by neg. potentials, which caused the redn. of water. As the pH on the surface exceeded that of pKchitosanH+\~6.3 deprotonation of the amino groups of chitosan caused the irreversible deposition of the chitosan/AuNPs. The effect of different parameters, such as tip-surface distance and time, on deposition was studied. While the potential duration showed no clear influence, smaller tip-substrate distance and more neg. potentials applied to the surface caused larger deposits. The overpotential needed for the deposition of nanoparticles on HOPG was the highest while that for StSt was the lowest. On the former, the sluggish kinetics caused the deposition of ring-shaped structures while disk-shaped deposits were formed on the other surfaces. [on SciFinder(R)]

A review. The following topics are discussed: Patterning by the Direct and Feedback modes of the SECM (Semiconductor, metal, and inorg. material etching and deposition; deposition of conducting polymers; self-assembled monolayers, polymers, and biomol. patterning); Speed of patterning, resoln., and scope of materials and approaches. [on SciFinder(R)]

Remote sensing is a fast developing field. The ability to detect various elements in secluded or inaccessible areas holds great opportunities. We present a new electrochem. flow cell which was developed as part of an autonomous flow system for measuring heavy metals in aquatic environments. The system was designed for remote sensing. Our system can utilize different com. available electrodes and apply a range of electrochem. methods. The system was studied through both electrochem. expts. and simulation. The potential of the platform was demonstrated by analyzing seawater spiked with Cd. Good agreement was found between our results and those obtained by ICP-MS anal. [on SciFinder(R)]

Gold nanoparticles, AuNPs, capped with mercaptocarboxylic acids followed by silver precipitation develop latent fingermarks on paper as high quality "negative" impressions. This effect stems from hydrogen bonding between the carboxylic group and the paper cellulose and may improve the yield of latent fingermarks since the results are less dependent on sweat composition.[on SciFinder (R)]

Gold nanoparticles, AuNPs, capped with mercaptocarboxylic acids followed by silver pptn. develop latent fingermarks on paper as high quality "neg." impressions. This effect stems from hydrogen bonding between the carboxylic group and the paper cellulose and may improve the yield of latent fingermarks since the results are less dependent on sweat compn. [on SciFinder(R)]

A self-assembled polymer of linear polyethylenimine (LPEI) on indium tin oxide (ITO) is found to stabilize the titanium-doped vanadium oxide film. After modification by LPEI, the oxide film shows good cycling stability, and sustains over 1500 cycles in a three-electrode system, a remarkable improvement compared to that without LPEI modification. [on SciFinder(R)]

A simple and cost effective sol-gel process for producing vanadium dioxide thin films was developed via thermolysis of V2O5·nH2O (n ≈ 2) VV precursors prepd. by dissolving vanadium powder or V2O5 powder in 30% hydrogen peroxide solns. After spin-coating on fused silica substrates and annealing at 750° in vacuum, without any intermediate gas reducing step, the major phase VO2(M, monoclinic phase) was found in both of the films based on V-H2O2 and V2O5-H2O2 precursor, exhibiting large transmittance changes (> 40%) in the IR region (> 2000 nm) and small hysteresis loop width (< 5°) which were comparable to reported epitaxial VO2 films. The two films have similar metal-to-insulator transition temp. τC = 62.5°, lower than the classical value of 68° for VO2 thin films. In addn., the method enables simple doping, as found for 0.56 at.% W-doped VO2 films. This intrinsically simple soln. process followed by one-step annealing makes it potentially useful in smart window applications. [on SciFinder(R)]

Electrochem. detn. of Hg(II) in aquatic solns. on bare and modified glassy carbon electrode (GCE) is reported. Optimizing the parameters used for a bare GCE, such as the electrolyte soln., the potential and time of deposition, resulted in linear response over a large range of Hg(II) concns. (4-160 ppb) using linear sweep anodic stripping voltammetry. Modification of the electrode with 4,4’-disulfanediyldibenzenediazonium (DSBD) yielded a lowest detection limit of 1 ppb. Two procedures for DSBD synthesis are described for the 1st time, and the product was characterized by microanal., FTIR and 1H-NMR. The electrochem. attachment of DSBD to the electrode was studied and compared with the electrochem. behavior of DSBD analogous mols., i.e. 4-aminophenyl disulfide, p-aminothiophenol and Ph disulfide. [on SciFinder(R)]