Improving the Analytical Performance of Graphene Oxide towards the Assessment of Polyphenols

The presence of oxygen functionalities on graphene surface has enormous influence on its electrochemical and electroanalytical properties. The oxygen-containing groups on graphene platforms can strongly affect the electrochemical response, being either detrimental for the heterogeneous charge transfer or promoting a favourable interaction with the specific analyte. In this study, by electrochemically reducing graphene oxide material at increasing negative potentials (from -0.25 to -1.50 V) we obtained eight electrochemically reduced graphene oxide (ERGO) platforms carrying a decreasing amount of oxygen functionalities. Subsequently, we analysed the electroanalytical response of each ERGO material for the detection of gallic acid, a standard polyphenol that is correlated to the antioxidant activity of food and beverages. The graphene platform providing the best electroanalytical performance in terms of sensitivity, selectivity and linearity of response was then employed for the analysis of commercial fruit juice samples. Herein we demonstrated that graphene materials can be electrochemically tuned to optimise their electrochemical response towards the detection of biologically important analytes.