Poly(pyrrole) based amperometric sensors : theory and characterization

The utilization of electropolymerized electronically conducting polymers as amperometric chemical sensors and electrocatalysts is described, with specific emphasis on poly(pyrrole) based materials. A theoretical model describing the operational principles of the polymer sensor is also described. The processes of substrate transport to the sensor surface, and subsequent substrate reaction at the latter, were analysed in the context of rotating disc voltammetry. Two distinct situations were considered. In the first, the substrate does not partition into the layer, but simply reacts, via Butler–Volmer kinetics, at the polymer/solution interface. The second situation arises when the substrate partitions into the polymer layer. In this instance, substrate diffusion and reaction within the film was analysed. The porous nature of the polymer film is specifically taken into account. The redox chemistry of poly(pyrrole) films doped with Cl– and DBS– ions was examined using cyclic voltammetry and complex impedance spectroscopy and the mechanism of redox switching in these materials was investigated. The electrode kinetics of the quinone–hydroquinone redox couple at the doped poly(pyrrole) films was also examined using cyclic voltammetry and rotating disc electrode voltammetry, and the mechanistic pathway was elucidated.