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)]

A surface-localized enzymic AND gate based on scanning electrochem. microscopy was designed and studied. The gate is composed of an insulating glass surface modified with the enzyme glucose oxidase (GOx) and another surface opposing it made of a microelectrode. The latter was modified with a second enzyme, invertase (INV). The distance sepg. the modified microelectrode and surface controlled the output of the AND gate produced upon the biocatalytic reaction of the confined enzymes. Specifically, as the GOx-modified glass substrate entered the diffusion layer of the microelectrode, it catalyzed the regeneration of an electron-transfer mediator, ferroceniummethanol, generated electrochem. at the tip by oxidizing glucose, also generated at the tip, by catalytic cleaving of sucrose by INV. To enhance the activity of the GOx, mutarotase was added to convert α- to β-glucose to be further consumed by GOx. Hence, an increase of the current at the microelectrode was obtained by approaching the glass surface only in the presence of all the components. This is the first micrometer-sized biomol. logic gate, of which the authors are aware, that is surface-confined and shows the promise held by the localization of biomol. information-processing species. [on SciFinder(R)]

Measuring the oxidn.-redn. potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in the soln. Sluggish electron transfer (ET) kinetics with the species will not reflect the true Eh of the soln. Here, the authors present a novel approach by which adsorbed metal nanoparticles (NPs) were used for enhancing ET exchange rates between redox species and electrode surface and therefore affect significantly the measurement of the open circuit potential (OCP) and cyclic voltammetry (CV). The OCP and CV of various org. and inorg. species such as l-dopa, dopac, Fe(II), and iodide are measured by bare stainless steel and by stainless steel modified by either Pt or Au NPs. The authors study the effect of the surface coverage of the stainless steel surface by NPs on the electrochem. response. Also, the stainless steel electrode was modified simultaneously by Au and Pt nanoparticles. This improved concurrently the stainless steel response (CV and potentiometry) toward two different species; l-dopa, which shows fast electron transfer on Pt, and catechol, which exhibits fast electron transfer on Au. Probably this approach is a 1st step toward developing a superior electrode for measuring the true Eh of complex aquatic systems. [on SciFinder(R)]

Ti-doped V oxide thin films were fabricated by electrochem. deposition on linear polyethylenimine (LPEI)-modified In Sn oxide-coated glass from mixed V oxide and Ti oxide solns. with different Ti concns. The as-prepd. films were studied by XRD, at. force microscopy (AFM), and XPS. The electrochem. behavior of the films was studied using cyclic voltammetry (CV) in 1.0 M LiClO4/propylene carbonate soln. Electrochromism of the oxide films upon Li-ion intercalation/deintercalation was studied by transmittance measurements during the CV process. The charge transfer resistance of the Ti-doped V oxide film was systematically analyzed with electrochem. impedance spectroscopy (EIS). The amorphous Ti-doped V oxide film contg. 4 mol% Ti exhibited the highest transmittance contrast (Δ%T = Tmax - Tmin) of ∼51.1%T, and coloration efficiency of 95.7 cm2 C-1 at 415 nm. By increasing the Ti content to 10 mol%, the Ti-doped V oxide film exhibited high switching speed and good cycling reversibility reaching 80% of coloring and bleaching time of 5 and 6 s, resp. Also, the transmittance contrast drops by only 10% after 600 cycles in a two-electrode system. [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)]

Novel biocompatible hybrid-material composed of iron-ion-cross-linked alginate with embedded protein molecules has been designed for the signal-triggered drug release. Electrochemically controlled oxidation of Fe(2+) ions in the presence of soluble natural alginate polymer and drug-mimicking protein (bovine serum albumin, BSA) results in the formation of an alginate-based thin-film cross-linked by Fe(3+) ions at the electrode interface with the entrapped protein. The electrochemically generated composite thin-film was characterized by electrochemistry and atomic force microscopy (AFM). Preliminary experiments demonstrated that the electrochemically controlled deposition of the protein-containing thin-film can be performed at microscale using scanning electrochemical microscopy (SECM) as the deposition tool producing polymer-patterned spots potentially containing various entrapped drugs. Application of reductive potentials on the modified electrode produced Fe(2+) cations which do not keep complexation with alginate, thus resulting in the electrochemically triggered thin-film dissolution and the protein release. Different experimental parameters, such as the film-deposition time, concentrations of compounds and applied potentials, were varied in order to demonstrate that the electrodepositon and electrodissolution of the alginate composite film can be tuned to the optimum performance. A statistical modeling technique was applied to find optimal conditions for the formation of the composite thin-film for the maximal encapsulation and release of the drug-mimicking protein at the lowest possible potential.[on SciFinder (R)]

Nanoelectrode ensembles (NEEs) have been fabricated by the electrodeposition of Au nanoparticles (AuNPs) on single-layer graphene oxide (GO) sheets coated on a glassy carbon electrode (GCE). The fabricated NEEs show a typical sigmoidal shaped voltammetric profile, arising from the low coverage density of AuNPs on GCE and large distance among them, which can be easily controlled by varying the electrodeposition time. As a proof of concept, after the probe HS-DNA is immobilized on the NEEs through the Au-S bonding, the target DNA is detected with the methylene blue intercalator. Our results show that the target DNA can be detected as low as 100 fM, i.e. 0.5 amol DNA in 5 μL solution.[on SciFinder (R)]

Novel biocompatible hybrid-material composed of iron-ion-crosslinked alginate with embedded protein mols. has been designed for the signal-triggered drug release. Electrochem. controlled oxidn. of Fe2+ ions in the presence of sol. natural alginate polymer and drug-mimicking protein (bovine serum albumin, BSA) results in the formation of an alginate-based thin-film crosslinked by Fe3+ ions at the electrode interface with the entrapped protein. The electrochem. generated composite thin-film was characterized by electrochem. and at. force microscopy (AFM). Preliminary expts. demonstrated that the electrochem. controlled deposition of the protein-contg. thin-film can be performed at microscale using scanning electrochem. microscopy (SECM) as the deposition tool producing polymer-patterned spots potentially contg. various entrapped drugs. Application of reductive potentials on the modified electrode produced Fe2+ cations which do not keep complexation with alginate, thus resulting in the electrochem. triggered thin-film dissoln. and the protein release. Different exptl. parameters, such as the film-deposition time, concns. of compds. and applied potentials, were varied in order to demonstrate that the electrodeposition and electrodissoln. of the alginate composite film can be tuned to the optimum performance. A statistical modeling technique was applied to find optimal conditions for the formation of the composite thin-film for the maximal encapsulation and release of the drug-mimicking protein at the lowest possible potential. [on SciFinder(R)]

Nanoelectrode ensembles (NEEs) have been fabricated by the electrodeposition of Au nanoparticles (AuNPs) on single-layer graphene oxide (GO) sheets coated on a glassy carbon electrode (GCE). The fabricated NEEs show a typical sigmoidal shaped voltammetric profile, arising from the low coverage d. of AuNPs on GCE and large distance among them, which can be easily controlled by varying the electrodeposition time. As a proof of concept, after the probe HS-DNA is immobilized on the NEEs through the Au-S bonding, the target DNA was detected with the methylene blue intercalator. The authors' results show that the target DNA can be detected as low as 100 fM, i.e. 0.5 amol DNA in 5 μL soln. [on SciFinder(R)]

In this work, "neg." fingermarks have been developed on paper, even after soaking in water, by the application of a new bifunctional reagent attached to gold nanoparticles, and then a silver phys. developer. The bifunctional reagent is composed of an active head, i.e., a polar group with high affinity to cellulose, attached by a long chain to an active tail contg. a sulfur group, which can stabilize gold nanoparticles. Through the active head, the gold nanoparticles, which are stabilized by the active tail, adhere preferentially to the paper cellulose rather than to the fingerprint material, to which they conventionally bind. Consequently, silver developer, which normally develops sebaceous fingermarks by pptg. dark silver on the sebaceous material, ppt. preferentially on the gold-coated areas giving rise to the appearance of uncolored ridge detail on a dark background. In this competing process, the paper itself serves as the substrate, whereas the fingermarks serve as a mask. This process may increase the overall yield of developed fingermarks as it bypasses the issue of the remarkable differences in sweat compn. between individual persons. [on SciFinder(R)]