Cobalt-Mediated Modification of Oxide Surfaces with Redox-Active Molecules

A new and general cobalt carbonyl-mediated method for the modification of indium-tin-oxide (ITO) electrode surfaces with redox-active molecules is reported. ITO substrates treated with Cl₃SiCo(CO)₄ yield surfaces with reactivity toward molecules that possess alcohol, amine, thiol, carboxylic acid, and amide functionalities. Surface coverages of the modifying reagents as determined by cyclic voltammetry are consistent with monolayers. Cyclic voltammetry of the redox-modified substrates indicates that ~1% of the active Si-Co(CO)₄ sites remain unreacted, and those that do may be rendered inactive by irreversible oxidation of the surface-bound cobalt species. Cl₃Si-H modified ITO also yields surfaces susceptible to reaction with alcohol and thiol functionalities, but submonolayer coverages were found after equivalent soaking times. Introduction of Co₂(CO)₈ into the modifying solutions increased the rates for surface modification and led to complete monolayer coverages after equivalent soaking times.