A CV/PBD coupled study of ionic exchanges at poly(pyrrole) films in phosphate buffered solutions

In order to propose new stable immunosensors with potential applications in the phosphate buffer saline solution (aqueous solution at pH 7.2 containin g 0.13 M NaCl and 0.05 M potassium phosphate), poly(pyrrole) films with var ious counter-anions (chloride, benzene sulfonate, benzene disulfonate and d ihydroxybenzene disulfonate) were prepared by electrooxidation of pyrrole i n aqueous solutions. The aim of this work was to determine the ion exchange properties of these poly(pyrrole) films during redox transformations, thes e properties being intimately connected to the probing characteristics of t he sensors. To investigate the system thoroughly, the behaviour of the film s was studied successively in the three following aqueous media: firstly 0. 13 M NaCl, then 0.05 M sodium phosphate at pH 7.2 and finally 0.13 M NaCl 0.05 M sodium phosphate at pH 7.2. This study was carried out by coupling a cyclic voltammetry technique to an optical method which allows the probin g of the ionic fluxes in the diffusion layer of an electroactive material ( probe beam deflection method). The results show that among all synthesized poly(pyrrole)s, only those with Cl- and dihydroxybenzene disulfonate as cou nter-anions have reversible redox changes in the phosphate buffer saline so lution. In the poly(pyrrole) films with Cl- counter-anions, it is shown tha t the Cl- anion is the main ion exchanged during redox changes. On the othe r hand, mainly cationic motion has been found in the poly(pyrrole) films wi th dihydroxybenzene disulfonate anions. (C) 2000 Elsevier Science Ltd. All rights reserved.