title: Feedback effects in combined fast-scan cyclic voltammetry-scanning electrochemical microscopy.
abstract: Fast-scan cyclic voltammetry at scan rates between 5 and 1000 V s(-1) was performed at the tip of a scanning electrochemical microscope immersed in a solution of redox mediator. The effect of conducting and insulating substrates on the voltammetric signal was investigated as a function of scan rate and tip-substrate distance. It was found that diffusional interactions between the tip and the substrate are greatest at lower scan rates and on the reverse sweep of the voltammogram. At the fastest scan rates used, the tip could be brought to with 1 microm of the substrate without appreciable perturbation of the voltammogram. By selecting scan rates and tip-substrate distances such that feedback effects were negligible, it was possible to image the diffusion layer of a 10 microm Pt substrate electrode. With the tip placed 1 microm above a biological cell, tip-substrate diffusional interactions were greatly diminished at a scan rate of 100 V s(-1) and absent at a scan rate of 1000 V s(-1). These results suggest conditions can be selected that allow chemical imaging of substrates without the feedback interactions typically encountered in scanning electrochemical microscopy.
authors.affiliation: Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Schrock
authors.forename: David O
authors.initials: DO
authors.lastname: Wipf
authors.forename: John E
authors.initials: JE
authors.lastname: Baur
mesh_terms: D002244:Carbon / Q000737:chemistry; D004058:Diffusion; D004553:Electric Conductivity; D004563:Electrochemistry; D004566:Electrodes; D020527:Microscopy, Scanning Probe / Q000379:methods*; D010084:Oxidation-Reduction; D010984:Platinum / Q000737:chemistry*; D017975:Ruthenium Compounds / Q000032:analysis* / Q000737:chemistry; D012680:Sensitivity and Specificity; D012996:Solutions / Q000737:chemistry; D013997:Time Factors
chemical_list: D017975:Ruthenium Compounds; D012996:Solutions; D010984:Platinum; D002244:Carbon