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The role of silver ions in the seed-mediated growth of gold nanostructures has been investigated. Silver submonolayer or monolayer on specific facet of gold is assumed in previously suggested mechanism owing to underpotential deposition (UPD) of silver by ascorbic acid having weak reducing power. Silver overpotential deposition by ascorbic acid, however, is confirmed by electrochemical stripping voltammetry, whereas submonolayer of silver on gold is spontaneously formed by anti-galvanic reduction in the absence of ascorbic acid. In the presence of cetyltrimethylammonium bromide (CTAB), silver overpotential deposition by ascorbic acid does not occur, but submonolayer of silver is formed on gold surface. Adsorption of silver and CTAB on gold dramatically hindered the electron transfer by the oxidation of ascorbic acid on gold, which reduces gold ions to metallic gold in seed-mediated growth. These results provide the evidence to the in-depth observation of mechanism in seed-mediated growth where the blockin...

A hydrogel pen consisting of a microscopic pyramid containing an electrolyte offers a localized electroactive area on the nanometer scale via controlled contact of the apex with a working electrode. The hydrogel pen merges the fine control of atomic force microscopy with non-linear diffusion of an ultramicroelectrode, producing a faradaic current that depends on the small electroactive area. The theoretical and experimental investigations of the mass transport behavior within the hydrogel reveal that the steady-state current from the faradaic reaction is linearly proportional to the deformed length of the hydrogel pen by contact, i.e. signal transduction of deformation to an electrochemical signal, which enables the fine control of the electroactive area in the nanometer-scale regime. Combined with electrodeposition, localized electrochemistry of the hydrogel pen results in the ability to fabricate small sizes (110 nm in diameter), tall heights (up to 30 μm), and arbitrary structures, thereby indicating an additive process in 3 dimensions by localized electrodeposition.

Size reduction of neural electrodes is essential for improving the functionality of neuroprosthetic devices, developing potent therapies for neurological and neurodegenerative diseases, and long-term brain–computer interfaces. Typical neural electrodes are micromanufactured devices with dimensions ranging from tens to hundreds of micrometers. Their further miniaturization is necessary to reduce local tissue damage and chronic immunological reactions of the brain. Here we report the neural electrode with subcellular dimensions based on single-crystalline gold nanowires (NWs) with a diameter of ∼100 nm. Unique mechanical and electrical properties of defect-free gold NWs enabled their implantation and recording of single neuron-activities in a live mouse brain despite a ∼50× reduction of the size compared to the closest analogues. Reduction of electrode dimensions enabled recording of neural activity with improved spatial resolution and differentiation of brain activity in response to different social situations for mice. The successful localization of the epileptic seizure center was also achieved using a multielectrode probe as a demonstration of the diagnostics potential of NW electrodes. This study demonstrated the realism of single-neuron recording using subcellular-sized electrodes that may be considered a pivotal point for use in diverse studies of chronic brain diseases.

Department of Applied Chemistry, Kumoh National Institute of Technology, Gumi, Kyungbuk 730-701, Republic of Korea(Received January 24, 2011 : Accepted February 8, 2011)Abstract: Polypyrrole (Ppy) nanowire has been electrochemically synthesized via vertically ori-ented mesoporous silica template. The mesoporous template is also electrochemically depositedon indium tin oxide coated (ITO) glass from tetraethyl orthosilicate (TEOS) and cetyltrimeth-ylammonium bromide (CTAB) surfactant. The highly ordered silica template is demonstratedto be 100~120nm thick with the pores of 4~5 nm diameter by scanning electron microscope(SEM) and transmission electron microscope (TEM). Ppy is formed to fill pores of the silicatemplate from pyrrole solution by electrochemical oxidation. The Ppy in Ppy/silica/ITO compositewas found to exhibit reversible electrochemical activity, as characterized by cyclic voltammetry (CV).Keywords : Polypyrrole, Nanowire, Mesoporous silica, Electrochemical capacitor

A nanowire electrode (NWE) was fabricated using a single-crystalline Au nanowire (NW) synthesized by vapor transport method without catalysts. Au NWEs were simply fabricated by manipulating a Au NW under an optical microscope. The successful fabrication was confirmed by electrochemical oxidation and reduction of a Au NW, from which we further observed well-defined geometry and {111}-faceted surface of Au NWEs. We also obtained a steady-state cyclic voltammogram, indicating enhanced mass transport. The potential application of Au NWEs to drug delivery into biological substances was suggested by immobilizing DNA on Au NWEs and its electrochemical release.