Electrosynthesis and electrochemical characterisation of phenazine polymers for application in biosensors

A comparative investigation has been undertaken of the electrosynthesis and electrochemical properties of three different electroactive polymers on carbon film electrode substrates: poly(neutral red) from the phenazine dye neutral red, and poly(methylene green) and poly(methylene blue), from the corresponding phenothiazine dyes. The formation of the radical cation at different potentials and the chemical structures of the monomers both influence the electropolymerisation process of the three polyaromatic dyes. Of the three, poly(neutral red) is shown to have the best adhesion at carbon film electrodes. The influence of the electrolyte and pH on film growth and on electrochemical properties was investigated. The formal potential decreased linearly with increase in pH, in the pH range from 1 to 7 for all three polymers. The modified electrodes were also characterised by electrochemical impedance spectroscopy. The bulk and interfacial characteristics of the two phenothiazine polymers were similar and oxygen-dependent, but different to those of the phenazine polymer, poly(neutral red), which were not significantly influenced by the presence of oxygen in solution. Perspectives for use in electrochemical biosensors are indicated.