Deactivation of Poly(o-Aminophenol) Film Electrodes After their Interac- tion with Ferric Cations. A Study Applying Interfacial Resistance Measu- rements

The experimental arrangement in this investigation is one in which poly(o-aminophenol) (POAP) films were supported on thin gold films. Freshly prepared POAP film electrodes were firstly deactivated by interaction with a ferric cation solution and then, they were reactivated by treatment with an alkaline solution. Cyclic Voltammetry (CV) and Surface Resistance (SR) measurements were performed to analyze if after consecutive deactivation and reactivation processes, the redox sites distribution (distance between adjacent redox sites) of POAP remained unaltered. By comparing with the resistance response of a freshly prepared POAP film, an attenuation of the gold film resistance within the potential region of maximal electroactivity of POAP was observed after polymer deactivation. This attenuated resistance change was attributed to the creation of polymer inactive zones at the gold film-POAP film interface. Thus, deactivated POAP films exhibit a redox sites distribution with larger distances between active redox sites, as compared with that present at a gold film surface contacting a non-deactivated poly(o-aminophenol) film. Surface Resistance also showed that while the redox sites distribution of a POAP film with a low degree of deactivation ( c < 0.4), can be recovered without distortion, the redox sites distribution of a POAP film with a degree of deactivation higher than 0.4, suffers a irreversible distortion, which remains even after reactivation by alkaline treatment. This work can be interesting from the practical viewpoint, because conducting properties of POAP, which are associated to the electron hopping process between adjacent redox sites, should remain substantially unchanged before and after the polymer has been used. In this regard, the results of this work show the restrictive stability conditions of POAP.