Electrochemical Quartz Crystal Microbalance Studies of the Formation and Redox Behavior of Poly(Neutral Red) Electrodes

Abstract

Simultaneous piezoelectric microgravimetry and cyclic voltammetry (CV) at an electrochemical quartz microbalance have been used to monitor the growth of poly(neutral red) films on the gold and graphite electrodes during potential cycling between –0.7 V and 0.75 V (vs. SCE) in sodium phosphate buffer (pH 5.3) and NaNO3 solutions. Both the adsorption–desorption of monomer neutral red and the formation of poly(neutral red) film can be followed by microgravimetry. The redox response of the polymer film is similar to that of the monomer attesting that the formation of the polymer takes place without the alteration of the original phenazine structure of the monomer. A shift of ca. –60 mV/pH of the CV peak potentials and the small mass change during the redox transformation of the polymer can be explained by a relatively simple 2H+, 2e– process, at pH<7. Depending on the degree of protonation of the reduced and oxidized forms, respectively, anion sorption–desorption may also occur.