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

Scannlng electrochemical microscopy (SECM) in the feedback mode, where the steady-state faradaic current at a mlcrodlsk electrode tip Is measured as the tip Is scanned close to a surface, was used to lnvestlgate several dlfferent polymer films on electrode surfaces: poly( vlnylterrocene), N,N’-Ms[3-(t))prop~lE4,4‘-blp~ridkdun e r n e , and Naflon containing Os(bpy);+. The tip response (Le., positive 01 negative feedback) depends upon the nature of the polymer, the substrate electrode potential, the Identity of the solutlon redox specles, and the tip potential. Studles carrled out wlth polymer films on lnterdlgltated array (IDA) electrodes wlth dlfferent redox specles in the cell solution demonstrate that the SECM Images can be used to dlstlngulsh chemically dlfferent sltes on a substrate surface. I t was also posslble wlth similar methods to dlstlnguish Au and oxide-covered Cr electrodes in an IDA.