Chemical polymerization and electrochemical characterization of thiazines for NADH electrocatalysis applications

Electrochemically polymerized azines have been employed frequently as NADH electrocatalysts in biosensors and biofuel cells. However, some applications of these electrocatalysts do not lend themselves to electropolymerization. Therefore, this research investigates the chemical synthesis and application of poly(methylene blue) (PMB) and poly(methylene green) (PMG) in electrocatalysis. In an attempt to develop a simple synthesis for polymerized thiazines that could be immobilized on any surface, we investigated several polymerization protocols that are described in this paper. Structural analyses imply that the chemically synthesized polymers are chemically unique in comparison to the electropolymerized polymers. Amperometric investigations were used to compare the catalytic activity of chemically and electrochemically synthesized polymers as electrocatalysts for the oxidation of NADH and the chemically synthesized polymers were employed at the bioanode of a methanol/air biofuel cell to show their utility for this application.