The electrochemical polymerization of methylene blue and properties of polymethylene blue

The electrochemical polymerization of methylene blue in the aqueous solutions has been carried out using repeated potential cycling. The scan potential was controlled at the region of −0.40 and 1.10 V, and the region of −0.40 and 0.92 V (vs. saturated calomel electrode, SCE). A blue film, i.e., polymethylene blue was formed on the platinum foil, and had a good electrochemical activity and reversibility in the pH region of 2.0 and 8.0. There are an anodic peak and a cathodic peak on the cyclic voltammograms. The currents of both anodic and cathodic peaks are proportional to υ1/2 at the scan rate (υ) region of 25 and 600 mV s−1. The electrochemical property of polymethylene blue polymerized on the platinum foil is different from that polymerized on the glassy carbon electrode. The visible spectra of polymethylene blue indicate that the wavelengths of absorption peaks are independent of potential at the range between 0.50 and −0.30 V (vs. Ag/AgCl with saturated KCl solution) and change a little with pH at the range between 3.0 and 8.0. The UV–Visible spectra and Raman spectra of polymethylene blue are different from those of methylene blue.