Spreadsheet-Based Cyclic Voltammetry Simulation of Mediated Ferrocyanide Oxidation By Ferrocene Derivatives in Alkanethiol-Based Self-Assembled Monolayers on Gold Electrodes

Abstract

Electron-transfer mediation reactions via surface-confined redox molecules in monolayer assemblies on electrodes have been studied for decades, but treatments that consider the electrode reaction in terms of microscopic rates for the relevant reactions are not so common. The critical reactions are (1) electron transfer between the immobilized redox molecule and the electrode, and (2) electron exchange between the immobilized redox molecule on the electrode and a second redox molecule in solution. Analytical solutions are available for limiting cases, e.g. no concentration polarization or convective mass transfer via electrode rotation, but not for the general case of cyclic voltammetry in quiescent solution, with full accounting of concentration polarization during the scan. This talk will present a spreadsheet-based digital simulation of this specific situation. A key element needed for the simulation is the surface flux condition, which is solved analytically as a kinetics problem considering reactions 1 and 2 above with a steady-state assumption. Simulated voltammograms will be presented and compared with experimental data for ferrocene-containing monolayers mediating ferrocyanide oxidation in solution. The simulation model allows for prediction of trends with respect to systematic changes in ferrocene surface coverage, ferrocyanide concentration, relative redox potentials for ferrocene and ferrocyanide redox, ferrocene oxidation / reduction rate constant, potential scan rate, and other parameters. Application in electrochemical biosensing at monolayers that also contain bioaffinity ligands will also be considered. Figure 1