COVALENT MODIFICATION OF CARBON SURFACES BY ARYL RADICALS GENERATED FROM THE ELECTROCHEMICAL REDUCTION OF DIAZONIUM SALTS

Electrochemical reduction of a wide variety of aromatic diazonium salt s on carbon electrodes (glassy carbon, highly oriented pyrolytic graph ite) leads to the covalent attachment of the corresponding aromatic ra dicals. The films thus deposited on glassy carbon surfaces require mec hanical abrasion to be removed. Cyclic voltammetry, X-ray photoelectro n spectroscopy, polarization modulation IR reflection absorption spect roscopy, Auger spectroscopy, and Rutherford backscattering spectroscop y allow the characterization of the overlayer and an estimate of the s urface coverage. The latter can be controlled through diazonium concen tration and electrolysis duration. The mechanism of derivatization is discussed on the basis of the kinetic data obtained from cyclic voltam metry and preparative electrolysis. This versatile method of surface m odification may find applications in the field of carbon-epoxy composi tes as attested by the successful binding of grafted p-aminophenyl gro ups with epichlorhydrin.