Voltammetric electrodes coated with carboxyl latex particles

Electrochemical properties at the carboxyl latex-coated electrode were examined in the context of accumulation or blocking of redox species in solution. The latex suspension was synthesized by copolymerization of styrene with acrylate, and was composed of spherical particles 0.27 μm in diameter. The deionized suspension showed iridescence. The latex particles were adsorbed strongly on a glass and a platinum surface in a two-dimensionally crystallized layer. One particle had 7.9 × 105 carboxyl groups, which were distributed in the inside of the particle at average concentration of 0.14 M. The latex-coated electrode was electrochemically active for the redox reactions of (ferrocenylmethyl)trimethyl ammonium (FcTMA) and Fe(CN)64- in aqueous solution. The voltammetric currents of FcTMA at pH more than 4 were larger than those without the film, whereas those at pH less than 3 were slightly smaller. The peak current was diffusion-controlled of FcTMA. The accumulation and the blocking were explained quantitatively in terms of Donnan equilibrium of FcTMA with immobilized carboxyl groups, depending on the dissociation constant of the carboxyl group, concentration of salt and pH.