Composite Electrode Material Based on Electrochemically Reduced Graphene Oxide and Gold Nanoparticles for Electrocatalytic Detection of Ascorbic Acid

A nanostructured composite matrix containing gold nanoparticles (AuNPs), graphene oxide (GO), and Nafion was immobilized on the surface of a glassy carbon electrode (GCE) by drop casting. The GO was electrochemically reduced (erGO), in order to obtain a modified interface (GCE/AuNPs-erGO-Nafion) able to detect l-ascorbic acid (AA) at lower oxidation potentials with increased sensitivity. The obtained modified electrode was investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and amperometry. The corroborated results showed that erGO and AuNPs at the interface act as a unique material having both high surface area (due to erGO) and high conductivity (due to AuNPs), being an effective electron transfer promoter in the electro-oxidation process of AA, lowering the oxidation potential of AA by ca. 0.400 V vs. Ag/AgCl,KClsat. The analytical parameters for AA detection at the modified GCE/AuNPs-erGO-Nafion electrode were determined by amperometry with a sensitivity of 39.07 +/- 1.36 mu A/mM and a detection limit of 2.76 mu M AA (signal/noise ratio of 3). The GCE/AuNPs-erGO-Nafion-modified electrode is simple to prepare, reliable, and with high sensitivity and was applied successfully in the routine analysis of AA in pharmaceutical products.