ELECTROREFLECTANCE STUDY OF REDOX REACTIONS OF METHYLENE-BLUE INCORPORATED INTO POLYPYRROLE COATED ON A PYROLYTIC-GRAPHITE ELECTRODE

The redox reactions of methylene blue (MB) incorporated into polypyrro le (PPy) on pyrolytic graphite (BPG) electrodes were investigated by t he potential-modulated electroreflectance (ER) method. The incorporati on of MB into the PPy film was achieved by either electropolymerizatio n of pyrrole in the presence of MB or polarization of the PPy-coated e lectrode at negative potentials in an MB solution. The ER spectrum of MB incorporated into the PPy-film, which was similar to that of MB ads orbed directly to the BPG electrode, suggested that MB in the PPy film diffused out during deaeration of the electrolyte solution and only M B adsorbed on the BPG electrode surface reacted. In the presence of MB in both the PPy film and solution phase, the measured ER spectrum was the sum of the ER spectra of MB adsorbed on the BPG electrode surface and MB in both the PPy film and solution phase. Each of the two spect ra was detected separately using the phase-shift method.