K. Miyata et al., SURFACE DISTRIBUTION AND ELECTRON-TRANSFER REACTION OF OSMIUM COMPLEXMEDIATOR ENTRAPPED ON POROUS CARBON ELECTRODE, Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 66(2), 1998, pp. 186-193
Enzyme-sensors using a porous carbon electrode with an Os complex as a
redox mediator have been described in previous studies. In this paper
, the distribution of the Os complex adsorbed on the porous carbon, co
mpared with plastic formed carbon (PFC), and the electron transport me
chanism were examined by XPS, CV and PSCC methods, respectively. XPS r
esults showed that the outermost surface of the porous carbon was main
ly covered with a Nafion layer, and the Os complex was present in the
inner pores of the porous carbon, indicating it has passed through the
Nafion layer. In contrast, the Os complex existed mainly in the Nafio
n layer on PFC electrode, on the basis of the XPS spectra. These resul
ts were confirmed by electrochemical analyses. The diffusion coefficie
nt for the Os complex on the porous carbon was found to be 8.92 x 10(-
12) cm(2)/sec, based on PSCC analysis. This value is about 20 times hi
gher than that of the Os complex passing through the Nafion layer, and
increased with an increase in its concentration, These results sugges
ted that the charge on the Os complex, produced by the redox reaction,
was transported into the electrode via electron self-exchange.