Engineering Low Cost ZnO/RGO Nanocomposite for the Picomolar Sensing of Epinephrine, Uric Acid and Tyrosine

This paper demonstrates a highly sensitive, selective, biocompatible and cost-effective method for the simultaneous determination of Epinephrine (EPN), Uric acid (UA) and Tyrosine (TYR). Superior electrochemical performance was achieved using ZnO/RGO/CPE modified electrodes compared to individual components, graphene oxide (GO) and ZnO modified electrodes. The electrochemical activity of the fabricated sensor is examined through cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). A sharp increase in anodic peak current and negative shift in the electrode potential upon modification indicates enhanced electrocatalytic activity of ZnO/RGO/CPE. Well distinguishable voltammetric peaks with base-to-base separation and better anodic current were achieved with modified electrode in a mixture of EPN, UA and TYR. The developed sensor exhibits good electrocatalytic activity and an excellent rate of electron transfer arising from the synergistic effect of ZnO and RGO. The detection limit of each biomolecule calculated using DPV is 310 pM for EPN, 340 pM for UA and 730 pM for TYR. The practical feasibility of the proposed sensor is demonstrated by recording satisfactory voltammetric responses in human urine and serum samples.