A Cyclic Voltammetry Study of Viologen Self-Assembled Monolayer Surface Structure

Modification and functionalization are effective ways to control the function and operation of electrodes. A simple modification process is to form self-assembled monolayers (SAMs) on the electrode surface using redox active molecules. The surface structure of these SAMs impacts the electrode performance, but often the structure is not well understood. In order to fully utilize and optimally functionalize electrodes, it is important to understand the structure at the electrode SAM interface. Herein, we study the surface structure of viologen functionalized Au electrodes through cyclic voltammetry. We demonstrate that cyclic voltammetry can be used to probe the surface structure in two perturbation experiments and propose a model of the viologen SAM. This work provides new insights into the structure of viologen SAM functionalized electrodes including a new coupled redox peak feature in the voltammogram and demonstrates the use of varying scan speed during cyclic voltammetry surface characterization to alter the redox center position in the monolayer. The new redox peak feature was not observed when the scan rate changed from 0.500 V·s^-1 to 0.010 V·s^-1, which can be attributed to restructuring of the viologen position in the SAM.