Electrochemical behaviour of FAD and FMN immobilised on TiO2 modified carbon fibres supported by ATR-IR spectroscopy of FMN on TiO2

Carbon fibre electrodes were modified with titanium oxide and used to adsor b some flavins on the electrode surface. FAD and FMN strongly adsorbed on t he titanium oxide dispersed on carbon fibres and remained stable for at lea st 2 months. The formal potential (E-alpha) at pH 7.0 of adsorbed FAD and F MN were - 245 and - 250 mV vs. SCE, respectively. The shift of the E-alpha of about 200 mV towards more positive values at pH 7.0 compared with that o f the dissolved flavin Ras assigned to the interaction between titanium oxi de and the flavins. The variation of the E-alpha with pH between 1 and 8 wa s also very much less than for dissolved flavins. The adsorbed flavins show ed a good electrocatalytic activity for NADH oxidation in aqueous solution applying a potential of 0 mV vs. SCE. The stability of the electrode was ve ry good and no significant change in either surface coverage of FMN or FAD or electrocatalytic response for NADH oxidation was observed after 250 cycl es. A linear response range for NADH between 1 and 6 mM was obtained. Addit ionally, attenuated total reflectance IR-spectra of FMN adsorbed on titaniu m films were recorded to clarify the interaction between the flavin and the support. (C) 1998 Elsevier Science S.A. All rights reserved.