Polypyrrole SECM studies

SECM can also be used to study the flux of species produced at a modified electrode surface, such as one with a film of polymer (Section 14.2.3). In one type of experiment, the tip is held at a potential where it can detect an electroactive ion released from the polymer film during a redox process (30-32). For example the SECM was used to detect the release of Br during the reduction of oxidized polypyrrole (PP) in the form, PP" Br . During a reductive cyclic voltammetric scan, Br was found to be released only in a later part of the scan, after an appreciable amount of cathodic charge had passed. This result suggested that during the early phase of the reduction the uptake of cations, rather than the release of anions, maintained charge balance in the film. 

A general approach to fabricating solid-state ion-selective microelectrodes has been described whereby a conducting electroactive polymer, which is both an electronic and an ionic conductor (e.g., polypyrrole, polythiophene, or polyaniline), is used to mediate charge exchange between an ion-selective membrane (an ion conductor) and a metal substrate (an electronic conductor) [28]. These electrodes are reported to be robust and mechanically flexible while exhibiting good potential stability with no redox sensitivity. While applications to potentiometric SECM have been described [28], these electrodes have yet to find use in corrosion studies. 

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