Cartenoid self-assembly on the gold electrode surface

Self-assembly of 4'-thioxo-beta,beta-caroten-4-one on the polycrystalline disk gold electrode (0.5 mm diameter) was performed ex situ by contact with carotenoid solution in acetonitrile for 10 - 30 minutes. Studies by cyclic voltammetry at 100 mV/s were subsequently performed in an aqueous, 0.01 M HClO4 solution. A strong inhibition of electron transfer reaction for species such as ferrocyanide /ferricyanide suggests that the surface layer exhibits a compact and well-ordered structure. Oxygen reduction is also partially inhibited by the carotenoid SAM. In addition, prolonged voltage cycling in the oxygen reduction range results in the gradual disappearance of the oxygen wave, although no oxygen depletion occurs in the solution. Presumably, some cross-linking of adsorbed carotenoid molecules take place under the effect of intermediate oxygen radicals.