A Glucose Biosensor Based on Glucose Oxidase Immobilized on ZnO/Cu2O Graphene Oxide Nanocomposite Electrode

Abstract

A pencil graphite electrode (PGE) was modified by a nanocomposite of graphene oxide (GO) and ZnO/Cu2O prepared by a simple electrochemical approach. Glucose oxidase (GOx) was immobilized onto the modified electrode (ZnO/Cu2O/GO/PGE) by electrostatic interaction between the negatively charged GOx and positively charged ZnO/Cu2O/GO composite. The results showed that the nanocomposite enhanced adsorption of GOx. Morphology of the modified electrode was studied by scanning electron microscopy. The electrochemical characteristics of the modified electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Then, the interaction of GOx and glucose was studied with differential pulse voltammetry (DPV). The DPV current of GOx decreased with increasing the concentration of glucose. The electron transfer coefficient (α) and electron transfer rate constant (ks) for redox reaction of GOx were found to be 0.48 and 1.52 ± 0.23 s−1, respectively. The biosensor shows a linear response to glucose over a concentration range of 0.01–2 mM with a detection limit of 1.93 μM. The value of Michaelis–Menten constant is 0.16 mM, the small value of which shows a good affinity of biosensor to glucose. It is found that, coupling ZnO/Cu2O and their synergistic effect can improve the properties of the biosensor.