†National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan
‡Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan
§Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
University of Tsukuba, 1-1-1 Tenno-dai, Tsukuba, Ibaraki 305-8571, Japan
MES-Afty Corporation, 2-35-2 Hyoe, Hachioji, Tokyo 192-0918, Japan
J. Am. Chem. Soc., 2011, 133 (13), pp 4840–4846
DOI: 10.1021/ja108614d
Section:Abstract
We have developed a new carbon film electrode material with thornlike surface nanostructures to realize efficient direct electron transfer (DET) with enzymes, which is very important for various enzyme biosensors and for anodes or cathodes used in biofuel cells. The nanostructures were fabricated using UV/ozone treatment without a mask, and the obtained nanostructures were typically 2−3.5 nm high as confirmed by atomic force microscopy measurements. X-ray photoelectron spectroscopy and transmission electron microscopy revealed that these nanostructures could be formed by employing significantly different etching rates depending on nanometer-order differences in the local sp3 content of the nanocarbon film, which we fabricated with the electron cyclotron resonance sputtering method. These structures could not be realized using other carbon films such as boron-doped diamond, glassy carbon, pyrolyzed polymers based on spin-coated polyimide or vacuum-deposited phthalocyanine films, or diamond-like carbon films because those carbon films have relatively homogeneous structures or micrometer-order crystalline structures. With physically adsorbed bilirubin oxidase on the nanostructured carbon surface, the DET catalytic current amplification was 30 times greater than that obtained with the original carbon film with a flat surface. This efficient DET of an enzyme could not be achieved by changing the hydrophilicity of the flat carbon surface, suggesting that DET was accelerated by the formation of nanostructures with a hydrophilic surface. Efficient DET was also observed using cytochrome .
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