Analytical Sciences

Controlling Surface Oxygen Concentration of a Nanocarbon Film Electrode for Improvement of Target Analytes

Mitsunobu TAKEMOTO,*,** Tomoyuki KAMATA,*** Dai KATO,*** and Masahiko HARA**

*Nitto Denko Corporation, 1-1-2 Shimohozumi, Ibaraki, Osaka 567-8680, Japan
**School of Materials and Chemical Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8502, Japan
***National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan

A nanocarbon film consisting of nanocrystallites with mixed sp² and sp³ bonds formed by unbalanced magnetron sputtering, was studied with respect to changes in the characteristics caused by the surface oxygen concentration. An electrochemical pretreatment (ECP) was conducted to change the surface oxygen concentration of the nanocarbon film. X-ray photoelectron spectroscopy (XPS) measurements revealed that nanocarbon films with different amounts of surface oxygen could be prepared. In addition, we observed no significant increase of surface roughness (R_a) at the angstrom level after ECP, owing to a stable structure containing 40% of sp³ bonds. The electrode characteristics, including the potential window, and electrochemical properties for some redox species, such as Ru(NH₃)₆^3+/2+, Fe(CN)₆^3−/4− and some biomolecules, were investigated. The anodic potential limit became wider and ΔE_p of Fe(CN)₆^3−/4− became smaller at the treated nanocarbon film electrode than those of the as-deposited nanocarbon film electrode. Based on these results, we realized to measure uridylic acid (UMP) and inosine triphosphate (ITP) with a high oxidation potential by direct oxidation, which was difficult to measure at the as-deposited nanocarbon film electrode.

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