Chemical modification of gold electrodes via non-covalent interactions

Abstract

Chemically modifying electrode surfaces with redox active molecular complexes is an effective route to fabricating tailored functional materials. Surface modification has generally required the installation of reactive functional groups for direct covalent attachment that can present synthetic challenges. An alternative, milder method that utilizes π-interactions to physisorb the molecular complex onto a surface is described herein. Firstly, a gold electrode was modified with pyrene via covalent thiolate bonds. A pyrene-functionalized ferrocene was then physisorbed onto the pyrene-modified gold electrode. X-ray photoelectron spectroscopy, infrared spectroscopy, and cyclic voltammetry were used to demonstrate successful physisorption of the pyrene-functionalized ferrocene onto the pyrene-modified gold surface. Physisorption is attributed to pyrene–pyrene (π) interactions, as the ferrocene compound was not observed after identical treatment of a clean gold electrode surface. Additionally, cyclic voltammetry demonstrates facile electron transfer between the electrode and ferrocene through the non-covalent interactions at the interface. Since this approach of surface modification only requires functionalizing the target molecular complex with the relatively inert pyrene functionality, it broadens the range of experimentally accessible molecular precursors for chemically modified electrodes.