The novel synthesis of highly water-soluble few-layer graphene nanosheets by a simple one-pot chemical route and without any modification

Abstract

In this study, a simple one-pot and scalable process including mild oxidation of graphite in mixture of H2SO4/KMnO4 at 60 °C was developed to synthesize water-soluble graphene. In this process, effects of the oxidant amount and reaction time on oxidation and exfoliation degree of graphite were explored. At this temperature, most oxygen-containing functional groups were introduced at the edges of graphite by preserving the pristine sp2carbon-bonded structure. These functional groups were responsible for exfoliation of edge-functionalized graphite (EFG) sheets to edge-graphene oxide (EGO). Various techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction pattern (XRD) and direct-current measurements proved that resulting EGO was formed from few-layer graphene nanosheets (GNS) with sub-2 nm thickness, low-defect sites in basal plane owing good solubility in water from pH 6 to 11 through electrostatic stabilization, as determined by zeta-potentiometry. This low-cost and high-efficiency solution processing techniques has enabled to produce aqueous graphene dispersions without need to use polymeric or surfactant stabilizers for many technological applications.