ELECTROCHEMICAL PREPARATION AND ANALYTICAL APPLICATIONS OF ULTRATHIN OVEROXIDIZED POLYPYRROLE FILMS

Ultrathin overoxidized polypyrrole films have been coated on different substrates (graphite and Pt). The thin films exhibit permselectivity against anions and excellent selectivity toward cations. Two approaches were used to coat the thin films on electrodes. On carbon electrodes, repeated polymerization and overoxidation was used to produce a pinhole-free thin film. On Pt electrodes, an adsorbed pyrrole monolayer was overoxidized to form an ultrathin film permselective against anions. A derivative of pyrrole, pyrrole-2-carboxylic acid, was also used to form thin films. The permselectivity of those thin films is discussed and compared. The practical use of the ultrathin films is demonstrated. The thin film coated ultramicroelectrodes are used to suppress the current of ascorbic acid while the current of dopamine is only slightly affected.