Effects of Film Morphology and Surface Chemistry on the Direct Electrochemistry of Cytochromecat Boron-Doped Diamond Electrodes.
The effects of film morphology and surface termination on the direct electron transfer of horse heart cytochromecon boron-doped ultrananocrystalline (B-UNCD) and microcrystalline (B-MCD) diamond thin-film electrodes were investigated. Quasi-reversible, diffusion-controlled cyclic voltammetric responses were observed on oxygen-terminated (atomic O/C ~0.015), but not hydrogen-terminated (atomic O/C ~0.02) diamond thin films. The effect of the surface termination was the same for both the nanostructured B-UNCD film with sp2-bonded carbon atoms in the grain boundaries and the well faceted B-MCD film with micron-sized grains and largely devoid of sp2carbon. Stable cyclic voltammetrici-Ecurves were recorded with cycling for both oxygen-terminated films indicating the absence of protein denaturation and electrode fouling. The peak currents increased linearly with the square root of the scan rate and the protein concentration; both indicative of a reaction rate limited by semi-infinite linear diffusion of the protein. Similar heterogeneous electron-transfer rate constants were observed for oxygen-terminated B-UNCD (3.48 (± 1.25) × 10-3cm/s) and B-MCD films (2.38 (± 0.72) × 10-3cm/s). The results clearly reveal that the oxygen-terminated surface is more active for electron-transfer with this soluble redox protein than is the hydrogen-terminated surface. The film morphology does not influence the diffusion-controlled response of the redox protein.
Department of Chemistry, Michigan State University, East Lansing, MI 48824.
Yingrui
Y
Dai
Department of Chemistry, Michigan State University, East Lansing, MI 48824.
Denis A
DA
Proshlyakov
Department of Chemistry, Michigan State University, East Lansing, MI 48824.
Greg M
GM
Swain
cytochrome c; diamond electrodes; surface chemistry