Electrochemical Sensing of Ascorbic Acid on ZnO-decorated Reduced Graphene Oxide Electrode

Abstract

A voltammetric sensor using differential pulse voltammetry (DPV) was developed for the detection of Vitamin C (ascorbic acid).The sensing platform was ZnO-decorated reduced graphene oxide on glassy carbon electrode (ZnO-RGO-GCE).Graphene oxide, synthesized by an improved Hummers method, was reduced with zinc powder under ultrasonication, followed by washing with HCl.X-ray diffraction and scanning electron microscopy showed ZnO nanoparticles decorating the reduced graphene oxide sheets.ZnO-RGO-GCE showed reversible behaviour with ferricyanide system, had about 3.5 times more surface area than GCE, and exhibited higher currents for ascorbic acid oxidation compared to bare GCE.Ascorbic acid was sensed over a wide range of 1 µM to 5000 µM (R 2 =0.9899) with a sensitivity of 0.178 µA/µM-cm 2 and detection limit of 0.01 µM, with good reproducibility (RSD=2.02%;n=5).The recovery of Vitamin C from pharmaceutical formulations, lemon juice, and gooseberry (amla) extract was also studied and compared against results from colorimetric methods.These results indicate that the developed ZnO-RGO-GCE platform could be used for voltammetric determination of Vitamin C in food samples.