Conductive polymers, such as polypyrrole (ppy), have been the subject of numerous studies due to their promising applications in organic solar cells, flexible electronics, electrochromic devices, super capacitors, etc. Yet, their application is still limited as a result of poor processability. Silica has been reported to improve the mechanical strength and adhesion of conductive polymer films. In this work, we propose a controllable electrochemical approach for preparing ppy-silica hybrid thin films from a solution containing both pyrrole and silane monomers. It is known that pyrrole can be electropolymerised using anodic potentials, while silica can be electrodeposited under cathodic potentials. Thus, we studied the formation of ppy-silica hybrid thin films on a stainless steel surface by applying alternating potentials, i.e. cathodic followed by anodic pulses (denoted C + A) or anodic followed by cathodic pulses (denoted A + C). We show that by controlling the deposition potential and time for the cathodic and anodic pulses, the film thickness and composition can be manipulated well as analysed using profilometry and EDX. The element depth profile of the films was characterized using secondary ion mass spectroscopy (SIMS). In essence, for the C + A process, pyrrole diffuses through the cathodically electrodeposited wet silica gel layer and undergoes anodic polymerisation on the substrate, while for the A + C process, silane can be electrodeposited both on top of the anodically electrodeposited conductive ppy films as well as on the stainless steel through the pinholes in the ppy film. This offers a simple approach for tuning the structure of conductive polymer-sol-gel composite films.[on SciFinder (R)]

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)]

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)]

A surface-localized enzymatic AND gate based on scanning electrochemical 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 separating 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 electrochemically 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 biomolecular logic gate, of which we are aware, that is surface-confined and shows the promise held by the localization of biomolecular information-processing species.[on SciFinder (R)]

Measuring the oxidation-reduction potential (Eh) requires an interface that is not selective toward specific species but exchanges electrons with all redox couples in the solution. Sluggish electron transfer (ET) kinetics with the species will not reflect the "true" Eh of the solution. Here, we present a novel approach by which adsorbed metal nanoparticles (NPs) are 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 organic and inorganic species such as l-dopa, dopac, iron(II), and iodide are measured by bare stainless steel and by stainless steel modified by either Pt or Au NPs. We study the effect of the surface coverage of the stainless steel surface by NPs on the electrochemical response. Moreover, 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. We believe that this approach could be a first step toward developing a superior electrode for measuring the "true" Eh of complex aquatic systems.[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)]

Graded SiO2-TiO2 binary composite films were prepd. by a unique electro-assist deposition approach from a mixt. of sol-gel precursors contg. tetramethoxysilane (TMOS) and Ti tetraisopropoxide (TTIP). A neg. potential applied to either stainless steel or ITO substrates causes the redn. of the solvent, thus increasing the concn. of hydroxyl ions, which enhances the precursor condensation and film deposition. The Ti:Si ratio in the films depends on the deposition potential, time and compn. of the precursor soln. This ratio decreases as the films grow thicker due to the more facile kinetics of SiO2 deposition. Nevertheless, the Ti:Si ratio in the films is always lower than in the corresponding precursor soln. As the Ti:Si ratio in the deposition soln. increases, the thickness of the electro-assist deposited films at the same conditions gradually decreases. SIMS and cross-section EDX anal. show that the Ti:Si ratio in the films increases from the surface to the substrate, suggesting electro-assist deposition as a potential method for 1-step prepn. of graded sol-gel films. [on SciFinder(R)]

Conductive polymers, such as polypyrrole (ppy), were the subject of numerous studies due to their promising applications in org. solar cells, flexible electronics, electrochromic devices, super capacitors, etc. Yet, their application is still limited as a result of poor processability. SiO2 is reported to improve the mech. strength and adhesion of conductive polymer films. The authors propose a controllable electrochem. approach for prepg. ppy-SiO2 hybrid thin films from a soln. contg. both pyrrole and silane monomers. Pyrrole can be electropolymd. using anodic potentials, while SiO2 can be electrodeposited under cathodic potentials. Thus, the authors studied the formation of ppy-SiO2 hybrid thin films on a stainless steel surface by applying alternating potentials, i.e. cathodic followed by anodic pulses (denoted C + A) or anodic followed by cathodic pulses (denoted A + C). By controlling the deposition potential and time for the cathodic and anodic pulses, the film thickness and compn. can be manipulated well as analyzed using profilometry and EDX. The element depth profile of the films was characterized using secondary ion mass spectroscopy (SIMS). In essence, for the C + A process, pyrrole diffuses through the cathodically electrodeposited wet silica gel layer and undergoes anodic polymn. on the substrate, while for the A + C process, silane can be electrodeposited both on top of the anodically electrodeposited conductive ppy films as well as on the stainless steel through the pinholes in the ppy film. This offers a simple approach for tuning the structure of conductive polymer-sol-gel composite films. [on SciFinder(R)]

Vanadium dioxide is an intriguing candidate for use in intelligent devices such as sensors, magnetic refrigeration and particularly as solar modulating smart window materials. A facile sol-gel route is developed to produce pure VO2 with different nanostructures in a CO2 atmosphere. It was found that the nanoporous structures demonstrated a 16% increase in the luminous transmittance (Tlum) (from 20% to 36%) compared with the vacuum results, while large supercooling effects of up to 30 °C have been obsd. in zero-dimensional structures. [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)]