Cyanographene and Graphene Acid: The Functional Group of Graphene Derivative Determines the Application in Electrochemical Sensing and Capacitors

Well-defined, stoichiometric derivatives of graphene afford many opportunities in fine-tuning of graphene properties and hence, extend the application potential of this material. Here, we present the electrochemical properties of cyanographene (G−CN), and graphene acid (G−COOH) in order to understand the role of the covalently attached functional groups on the graphene sheet in electrochemical sensing for the detection of biomarkers. G−CN shows better performance for the negatively charged analytes ascorbic and uric acids when compared to G−COOH. The less-favourable performance of G−COOH is explained by repulsion between negatively charged analytes and negatively charged functional groups of G−COOH. The capacitance of both materials is in a comparable range, but chronopotentiometry reveals that G−CN shows a greater capacitance than G−COOH. The identified differences in electrochemical properties imprinted by the functional group show that its chemical nature can be exploited in fine-tuning of the selectivity of electrochemical sensing and energy storage applications.