Permanganate-route-prepared electrochemically reduced graphene oxides exhibit limited anodic potential window

Graphene-related materials have been of significant interest in the field of electrochemical sensing and biosensing. Four main methods of synthesizing large quantities of graphene from graphite via graphene oxide have been used to date, using either chlorate (Staudenmaier and Hofmann methods) or permanganate (Hummers and Tour methods) oxidants and strong mineral acids to generate graphite oxide with subsequent reduction. In electrochemical applications, electrochemical reduction is often used to prepare reduced graphenes so as to eliminate any electrochemically reducible groups on the surface of graphene oxides which could interfere with the analytical signals. Here, we show that electrochemical reduction of oxygen-containing groups at graphene oxide surfaces indeed results in materials without inherent electrochemistry for chlorate-based graphene oxides; however, permanganate-based electrochemically reduced materials exhibited significant limitation in the anodic region, starting from μ+0.1 V (vs Ag/AgCl). The effect of the anodic potential windows was studied with uric acid, ascorbic acid, and dopamine, and it was evident that the oxidation signals of the analytes performed on permanganate-based reduced graphene oxides were superposed on the background signals, resulting in wider peaks and larger oxidation currents. Given the fact that the permanganate route (Hummers method) has been most widely used for preparation of graphene oxide, we wish to warn the electrochemical community and to emphasize that the method used for preparation of these reduced graphene materials should be considered in advance as it may be interfering with the response of some compounds.