Tan, Sze-yin, Zhang, Jie , Bond, Alan M., Macpherson, Julie V. and Unwin, Patrick R. (2016) Impact of adsorption on scanning electrochemical microscopy voltammetry and implications for nanogap measurements. Analytical Chemistry, 88 (6). pp. 3272-3280. doi:10.1021/acs.analchem.5b04715

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Abstract

Scanning electrochemical microscopy (SECM) is a powerful tool that enables quantitative measurements of fast electron transfer (ET) kinetics when coupled with modeling predictions from finite-element simulations. However, the advent of nanoscale and nanogap electrode geometries that have an intrinsically high surface area-to-solution volume ratio realizes the need for more rigorous data analysis procedures, as surface effects such as adsorption may play an important role. The oxidation of ferrocenylmethyl trimethylammonium (FcTMA+) at highly oriented pyrolytic graphite (HOPG) is used as a model system to demonstrate the effects of reversible reactant adsorption on the SECM response. Furthermore, the adsorption of FcTMA2+ species onto glass, which is often used to encapsulate ultramicroelectrodes employed in SECM, is also found to be important and affects the voltammetric tip response in a nanogap geometry. If a researcher is unaware of such effects (which may not be readily apparent in slow to moderate scan voltammetry) and analyzes SECM data assuming simple ET kinetics at the substrate and an inert insulator support around the tip, the result is the incorrect assignment of tip–substrate heights, kinetics, and thermodynamic parameters. Thus, SECM kinetic measurements, particularly in a nanogap configuration where the ET kinetics are often very fast (only just distinguishable from reversible), require that such effects are fully characterized. This is possible by expanding the number of experimental variables, including the voltammetric scan rate and concentration of redox species, among others.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry
Divisions:	Faculty of Science > Chemistry
Library of Congress Subject Headings (LCSH):	Electrochemistry, Oxidation, Graphite , Electrodes
Journal or Publication Title:	Analytical Chemistry
Publisher:	American Chemical Society
ISSN:	0003-2700
Official Date:	15 March 2016
Dates:	Date Event 15 March 2016 Published 13 February 2016 Available 13 February 2016 Accepted 12 December 2015 Submitted
Volume:	88
Number:	6
Page Range:	pp. 3272-3280
DOI:	10.1021/acs.analchem.5b04715
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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