▎ 摘　　要

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.