A straightforward electrochemical deposition process was developed to grow gold nanostructures, including nanocoral, nanothorn, branched belt, and nanoparticle, on carbon electrodes by reducing HAuCl4 under constant potentials in mixtures containing CTAC and/or NaNO3. Among the nanostructures, the quasi-one-dimensional nanocoral electrode showed the highest surface area. Because of this, it provided excellent electrochemical performances in cyclic voltammetric (CV) studies for kinetic-controlled enzyme-free glucose oxidation reactions. In amperometric studies carried out at 0.200 V in PBS (pH 7.40, 0.100 M), the nanocoral electrode showed the highest anodic current response. It also offered the greatest sensitivity, 22.6 μAmM(-1)cm(-2), an extended linear range, 5.00×10(-2) mM to 3.00×10(1) mM, and a low detection limit, 1.00×10(1) μm among the electrodes investigated in this study. In addition, the glucose oxidation by the nanocoral electrode started at -0.280 V, more negative than the one of using a commercial Au electrode as the working electrode. This is attributed to the presence of exposed Au (110) surfaces on the electrode. The feature was applied to oxidize glucose selectively in the presence of ascorbic acid (AA) and uric acid (UA), common interferences found in physiological analytes. With an applied voltage at -0.100 V, the AA oxidation (started at -0.080 V) can be avoided while the glucose oxidation still provides a significant response.

Tunnel-structured potassium titanate with a K(3)Ti(8)O(17) phase was synthesized by direct oxidation of titanium powder mixed with KF(aq) in water vapor at 923 K. The reaction conditions were adjusted so that uniform single crystalline potassium titanate nanowires with [010] growth direction (length: 5-30 μm, diameter: 80-100 nm) were obtained. Nitridation of the nanowires by NH(3)(g) at 973-1073 K converted the titanate nanowires into rock-salt structured cubic phase single crystalline titanium oxynitride TiN(x)O(y) nanotubes (x = 0.88, y = 0.12, length = 1-10 μm, diameter = 150-250 nm, wall thickness = 30 - 50 nm) and nanorods (x = 0.5, y = 0.5, length = 1-5 μm, diameter = 100-200 nm) with rough surfaces and [200] growth direction. The overall conversion of the titanate nanowires into the nanotubes and the nanorods can be rationalized by Ostwald ripening mechanism. We fabricated an electrode by adhering TiN(x)O(y) nanotubes (0.2 mg) on a screen-printed carbon electrode (geometric area: 0.2 cm(2)). Electrochemical impedance spectroscopy demonstrated its charge transfer resistance to be 20Ω. The electrochemical surface area of the nanotubes on the electrode was characterized by cyclic voltammetry to be 0.32 cm(2). This property suggests that the TiN(x)O(y) nanostructures can be employed as potential electrode materials for electrochemical applications.

Urchin-like Ag nanowires were prepared by reacting AgNO 3 (aq) with Cu metal in the presence of cetyltrimethylammonium chloride and HNO 3 (aq) on a screen printed carbon electrode at room temperature. The diameters of the nanowires were about 100 nm, while the lengths were up to 10 mm. Cyclic voltammetric experiments using the Ag nanowires as the working electrode showed electrocatalytic H 2 O 2 reduction. The electrode exhibited a high sensitivity of 4705 mA mM -1 mg -1 cm -2 from 50 mM to 10.35 mM and a measurable detection limit of 10 mM in amperometric detection. This is the first report on Ag NWs for non-enzymatic H 2 O 2 sensing.