SCANNING ELECTROCHEMICAL MICROSCOPY .5. A STUDY OF THE CONDUCTIVITY OF A POLYPYRROLE FILM

The potential dependence of the conductivity of a polypyrrole polymer film was studied by scanning electrochemical microscopy (SECM) operating in the feedback mode, where the steady-state faradaic current at an ultramicroelectrode tip increased or decreased depending on the conductivity of a sample as the tip was moved near the surface of the sample immersed in an electrolyte solution. From the measurement of tip current as the potential of a polypyrrole film was scanned, the region of potential where the film is conductive could be obtained. When a disk-shaped ultramicroelectrode tip (12.5 µm radius) was two-dimensionally scanned above the boundary region of the platinum-polypyrrole substrate (a Pt disk, 1 mm radius, half of which was covered by the polypyrrole film ca. 2000Å thick), the tip currents could be used to image the substrate. The effect of tip scanning speed and the substrate potentials were employed to study the conductivity of the polypyrrole film and the diffusion hysteresis in SECM in the feedback mode. © 1990, The Electrochemical Society, Inc. All rights reserved.