The effect of the structure of three different redox mediators on the oxidation of tetrabutylammonium acetate was studied in acetonitrile on glassy carbon and HOPG electrodes The direct oxidation of acetate ion is essentially a carbocation process which allows in many Instances the formation of products in solution However a covalent modification of the carbon surface was possible when the oxidation process is mediated by ferrocene derivatives The redox catalysis process occurs at lower potential values than the direct oxidation process which triggers a radical chemistry allowing the grafting of carbon surfaces with methyl groups Depending on the redox potential of the mediator as well as on the number of ferrocene redox centers present in its structure the efficiency of the electrode modification process can be significantly increased Atomic force microscopy images of HOPG modified surfaces by using either a mediator containing one or two redox centers were obtained to show the formation of aggregates distributed in a highly compact layer (C) 2010 Elsevier B V All rights reserved