▎ 摘　　要

This research presents two new modified Hummers' methods which include the pre-oxidation of graphite powder by mixtures of H3BO3/H2SO4 and H3BO3/H2SO4/CrO3. Compared to the traditional Hummers' method, these significant improvements substantially enhanced the number of oxygen functionalities onto graphene oxide (GO) layers. The GO samples were characterized by X-ray photoelectron spectroscopy (XPS), Boehm titration, Raman spectroscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), and zeta potential analysis. Boehm titration results showed that GO layers contain oxygen functionalities such as phenolic, ketone, lactone, carboxyl, and epoxy. Quantitative XPS analysis reveals that GO obtained using a pre-oxidation step with H2SO4/H3BO3/CrO3 mixture has a higher oxidation degree (C/O = 1.03). Moreover, this sample possessed a greater number of electronegative functional groups, resulting in the decrease of the zeta potential (-43.3 mV). Raman analysis revealed a slightly higher structural disorder in GO layers during the increase in oxidation levels. Further, reduced GO (rGO) obtained from new synthesized GO were tested as label-free H2O2 sensors electrodes. The electrochemical investigations showed that the samples were prospective on H2O2 sensing. Our results suggest that the properties of rGO can be tuned by varying the oxidation degree of GO, which may stimulate new developments in rGO-based sensors.