Homoepitaxial single-crystal boron-doped diamond electrodes for electroanalysis

In order to study the properties of single-crystal boron-doped diamond electrodes for electroanalysis, (100) and (111) boron-doped homoepitaxial single-crystal and polycrystalline diamond thin films were deposited by means of microwave plasma-assisted chemical vapor deposition. Features in the cyclic voltammograms (CVs) for aqueous H2SO4 supporting electrolyte and Fe(CN)(6)(3-)/(4-) in aqueous Na2SO4 for polycrystalline electrodes were dominated by behavior typical of (111) single-crystal facets, rather than (100) facets. Apparent heterogeneous electron-transfer rate constants (k(0)) for various redox systems were estimated with CV simulation at polycrystalline, (111) and (100, off-axis, 4degrees). Based on comparison with the Marcus model, the behavior of the k(0) values, except for that of Fe(CN)(6)(3-)/(4-), indicates apparent outer-sphere electron-transfer, but with a lower density of states compared to glassy carbon or typical metal electrodes. The (111) homoepitaxial film performed better than a polycrystalline film in the cyclic voltammetric detection of serotonin, with signal-to-background ratios of 5 and 2, respectively. Single-crystal diamond may thus be an even more optimal electrode material for electroanalysis than polycrystalline diamond, which has been shown to have superior characteristics as an electrode material. (C) 2002 The Electrochemical Society.