Solvothermal synthesis of homogeneous graphene dispersion with high concentration

We developed a simple surfactant-free approach to graphene dispersion through a solvothermal reduction of graphene oxides in N,N-dimethylformamide, and the concentration of the as-prepared graphene dispersion can reach up to 0.3 mg mL−1. The as-prepared graphene could be re-dispersed well in more than six kinds of solvents, such as N-methylpyrrolidone, N,N-dimethylacetamide, and acetonitrile. In the solvothermal reduction process, no extra reducing agent and/or stabilizer is needed, and the deoxygenation is promoted by the relatively high temperature and autogenous pressure in the autoclave. Atomic force microscopy analysis shows most of the graphene sheets in the as-prepared dispersion are single-layered. X-ray photoelectron spectroscopy, thermal gravimetric analysis, and infrared spectroscopy confirm the efficient removal of the oxygen-containing groups.