Effect of electrolyte properties on charge transfer at a monolayer modified electrode

ENVR 184

Chaitanya Gupta, cgupta2@uiuc.edu1, Mark A. Shannon, mshannon@uiuc.edu2, and Paul J. A. Kenis, kenis@uiuc.edu1. (1) Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 114 Roger Adams Laboratory, Box C-3, 600 S. Mathews Avenue, Urbana, IL 61801, (2) Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, Urbana, IL 61801
We describe an experimental methodology to measure charge transfer through ω-functionalized alkanethiol films on gold when there is no electro-active ion in the electrolyte. A generalized expression for the admittance of a model thin-film electrode system is proposed and this expression, when fit to a potential-based spectrum of low frequency impedance values, enables the calculation of parameters that characterize charge transport in the monolayer. We demonstrate the existence of two thermodynamic free energy barriers that limit the kinetics of the charge transfer process: (a) a transport barrier that limits charge transport through the monolayer film and (b) an activation energy barrier to the transfer of electrons across the monolayer-electrolyte interface. Electrolyte properties like pH, salt concentration and cation/anion type are shown to have a significant effect on the observed transport barriers. This enables the use of simple monolayer-modified electrodes as platforms to detect and quantify chemicals within aqueous systems.
 

Sensors for Detection and Quantification of Contaminants in Drinking Water and the Environment
1:30 PM-5:10 PM, Wednesday, April 9, 2008 Morial Convention Center -- Rm. 235, Oral

Division of Environmental Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008