KINETIC-BEHAVIOR OF A ROTATING GOLD DISK ELECTRODE MODIFIED WITH A SELF-ASSEMBLED FERROCENECARBOXAMIDOYL MONOLAYER BASED ON ZIRCONIUM PHOSPHONATE

A rotating gold disk electrode was modified with a ferrocenecarboxamid oyl monolayer, which is ionically bound to a well-ordered zirconium ph osphonate film on electrode surface. Voltammetric behaviors on a modif ied Au disk electrode have been studied in solutions containing electr oactive species. This electroactive film with constant thickness of ca . 29 Angstrom simultaneously shows not only an electron-transfer block ing property but also an electron-transfer mediating property. The lim iting steady-state current was measured as a function of rotation rate and overpotential for monomer-mediated oxidation of Fe(CN)(6)(4-) and was analyzed to get kinetic parameter values (k(et), K-0, and alpha) by a simulation fitting program. The extracted values of rate constant for the monomer/redox couple electron-exchange reaction and the irrev ersible charge transport reaction indicate that a relatively facile el ectron transfer reaction occurs in the high overpotential region even though the zirconium phosphonate film makes the electron propagation r ate through the film slower. (C) 1996 Elsevier Science Ltd.