Hierarchically driven IrO 2 nanowire electrocatalysts for direct sensing of biomolecules

Applying nanoscale device fabrications toward biomolecules, ultra sensitive, selective, robust, and reliable chemical or biological microsensors have been one of the most fascinating research directions in our life science. Here we introduce hierarchically driven iridium dioxide (IrO 2) nanowires directly on a platinum (Pt) microwire, which allows a simple fabrication of the amperometric sensor and shows a favorable electronic property desired for sensing of hydrogen peroxide (H 2O 2) and dihydronicotinamide adenine dinucleotide (NADH) without the aid of enzymes. This rational engineering of a nanoscale architecture based on the direct formation of the hierarchical 1-dimensional (1-D) nanostructures on an electrode can offer a useful platform for high-performance electrochemical biosensors, enabling the efficient, ultrasensitive detection of biologically important molecules. © 2012 American Chemical Society

Growth of highly single crystalline IrO 2 nanowires and their electrochemical applications

We present the facile growth of highly single crystalline iridium dioxide (IrO 2) nanowires on SiO 2/Si and Au substrates via a simple vapor phase transport process under atmospheric pressure without any catalyst. Particularly, high-density needle-like IrO 2 nanowires were readily obtained on a single Au microwire, suggesting that the melted surface layer of Au might effectively enhance the nucleation of gaseous IrO 3 precursors at the growth temperature. In addition, all the electrochemical observations of the directly grown IrO 2 nanowires on a single Au microwire support favorable electron-transfer kinetics of [Fe(CN 6)] 4-/3- as well as Ru(NH 3) 63+/2+ at the highly oriented crystalline IrO 2 nanowire surface. Furthermore, stable pH response is shown, revealing potential for use as a miniaturized pH sensor, confirmed by the calibration curve exhibiting super-Nernstian behavior with a slope of 71.6 mV pH -1. © 2012 American Chemical Society

Single carbon fiber decorated with RuO 2 nanorods as a highly electrocatalytic sensing element

We demonstrate highly efficient electocatalytic activities of single crystalline RuO 2 nanorods grown on carbon fiber (CF), i.e., RuO 2 nanorod-CF hybrid microelectrode, prepared by a simple thermal annealing process from the Ru(OH) 3 precursor at 300 °C. The general electrochemical activity of a RuO 2 nanorod-CF microelectrode represents faster electron transfer for the [Fe(CN) 6] 3-/4- couple than that of the bare CF microelectrode which are confirmed from the cyclic voltammetry (CV) measurement. Also, the amperometric response for the H 2O 2 oxidation is remarkably facilitated at the RuO 2 nanorod-CF microelectrode by not only the enlarged surface area but the high electrocatalytic activity of the RuO 2 nanorod material itself. Furthermore, a single microelectrode of RuO 2 nanorod-CF exhibits the superior tolerance to Cl - ion poisoning unlike Pt-based electrocatalysts, indicating the promising sensor candidate in physiological conditions. © 2012 American Chemical Society