Determination of the concentration of ascorbic acid in a solution has attracted intense recent interest. Here we demonstrate the feasibility of electro-oxidation of ascorbic acid on spherical cobalt core-shell nanoparticles (10-50 nm dia.) prepared by electrochemical deposition on a H-terminated Si(100) substrate. Depth-profiling X-ray photoelectron spectroscopy reveals that these nanoparticles consist of a metallic cobalt core covered by a Co(OH)2 shell without any evidence of CoOx. Glancing-incidence X-ray diffraction studies further show that the metallic Co core consists of a mixture of hexagonal close packed and face centered cubic structures, the relative composition of which can be easily controlled by the deposition potential. We further demonstrate that when these Co nanoparticles are deposited on a high-surface-area electrode as provided by a Si nanowire template, the resulting nanostructured Co-coated Si nanowire electrode offers a promising high-performance sensor platform for ascorbic acid detection.

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