Polypyrrole/Poly(methylene blue) Composite Electrode Films on Stainless Steel

Polymerized methylene blue films have been shown to be efficient electron mediators for biological redox compounds. Previously these films have been deposited on noble metal and carbon substrates. In this work, methylene blue has been polymerized on stainless steel by first applying a layer of an electronically conductive polymer to inhibit passivation or corrosion of the metal and to increase the active surface area. The redox activity of the resulting electrodes has been examined by electrochemical impedance spectroscopy and fit to an equivalent circuit model for conductive polymers. The film with methylene blue shows a large decrease in charge transfer resistance, from 130 Omega to 15 Omega, when compared to the bare polypyrrole film. The stability of the films was studied by measuring the impedance changes over time when stored in aqueous solutions. Degradation of the films was found to depend mostly on the doping ion used in the polypyrrole synthesis. NADH oxidation was also measured at different concentrations by CV.