Electrochemical quartz crystal microbalance studies of the formation and redox behavior of poly(neutral red) electrodes

Simultaneous piezoelectric microgravimetry and cyclic voltammetry (CV) at a n electrochemical quartz microbalance have been used to monitor the growth of poly(neutral red) films on the gold and graphite electrodes during poten tial cycling between -0.7 V and 0.75 V (vs. SCE) in sodium phosphate buffer (pH 5.3) and NaNO3 solutions. Both the adsorption-desorprion of monomer ne utral red and the formation of poly(neutral red) film can be followed by mi crogravimetry. The redox response of the polymer film is similar to that of the monomer attesting that the formation of the polymer rakes place withou t the alteration of the original phenazine structure of the monomer. A shif t of ca. -60 mV/pH of the CV peak potentials and the small mass change duri ng the redox transformation of the polymer can be explained by a relatively simple 2H(+), 2e(-) process, at pH < 7. Depending on the degree of protona tion of the reduced and oxidized forms, respectively, anion sorption-desorp tion may also occur.