Synthesis of Nanozymes Using Graphene Oxide and Gold Nanoparticle and Its Application to Electrochemical Biosensor

In this study, we fabricated a nafion/graphene oxide-gold nanoparticle (GO-AuNP) hybrid modified ITO electrode and proposed an electrochemical method to detect hydrogen peroxide (H2O2) using 3,3,5,5,-tetramethylbenzidine (TMB) as a redox mediator. The GO-AuNP hybrids were prepared with a simple procedure and characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The resulting composites were employed as nanozymes, which function as peroxidase mimics and show highly effective catalytic activity. It has been suggested that the improved catalytic activity can be attributed to the promoted electron transfer between nanozymes and substrates and the increased initial adsorption of substrates. Based on the high catalytic activity, enzyme mimics were entrapped on the ITO electrode to construct an electrochemical H2O2 sensor by casting nafion film as a secondary layer. During the catalytic reaction, the peroxidase substrate TMB was oxidized to form the TMB oxidation product, which not only produces a blue color detected by absorbance change, but also generates an electrochemical current. As a result, both spectrophotometric and electrochemical methods were used to determine H2O2 concentration. The spectrophotometric detection displayed a linearity for H2O2 concentration from 10 ??M to 5 mM (r2=0.989), with an estimated detection limit of 2.0 ??M. In the electrochemical detection, the TMB peak current had a good linear relationship with H2O2 concentration from 10 nM to 10 mM, with an estimated detection limit of 1.9 nM, which was much lower than that of the spectrophotometric method result. Furthermore, the electrochemical detection method also exhibited good sensitivity, reproducibility, and reliability.Maste