Scanning Electrochemical Microscopy. Application to Polymer and Thin Metal Oxide Films

Scanning electrochemical microscopy (SECM) In the feedback mode, where the steady-state faradalc current at a microdisk electrode tip Is measured as the tip is scanned close to a surface, was used to Investigate several different polymer films on electrode surfaces: poly(vinylferrocene), N, N′-bis[3-(trimethoxysilyl)propyl]-4.4′-blpyridinium dibromide, and Naflon containing Os(bpy)₃²⁺. The tip response (i.e., positive or negative feedback) depends upon the nature of the polymer, the substrate electrode potential, the identity of the solution redox species, and the tip potential. Studies carried out with polymer films on interdigitated array (IDA) electrodes with different redox species in the cell solution demonstrate that the SECM images can be used to distinguish chemically different sites on a substrate surface. It was also possible with similar methods to distinguish Au and oxide-covered Cr electrodes In an IDA.