Electropolymerization of preadsorbed layers of some azine redox dyes on graphite

The redox-active azine dyes Nile blue A (NB) and Toluidine blue O (TB) were electropolymerized after preadsorption onto the surface of graphite electr odes by potential cycling, using an anodic scan limit of 0.9 or 1.0 V vs SC E, where irreversible electrooxidation of the dye proceeds, yielding polyme rizable species. Electropolymerization of both dyes is followed by the prog ressive disappearance of the characteristic current peaks in the cyclic vol tammograms, and formation of new ones, shifted by ca. 0.21 V to the positiv e direction. Also, a decrease and gradual disappearance of the characterist ic luminescence at a maximum of 671 mn was observed during the electropolym erization of NE. The resulting electrodes, modified by electropolymerized d erivatives of NE and TB, were shown to be able to catalyze the electrooxida tion of the coenzyme NADH. Thus, the modified electrodes prepared can be us ed for amperometric detection of the reduced form of the coenzyme. (C) 2000 Academic Press.