The Preparation Of High Quality Graphene Dispersion

In this paper, high quality graphene dispersions have been successfully synthesized. We obtained large sized graphene oxide dispersions through improved preparation method, following chemical reduction carried out by hydrous hydrazine to prepare large sized graphene dispersions. Further more, graphite was solvent exfoliated in N,N-Dimethylformamide (DMF) and Chloroform, to produce graphene dispersions at high concentration in a short time. And the concentration of graphene dispersions were investigated with different preparation conditions.By using large sized graphite, mild oxidation, and low power bath sonication for short times, stable large sized graphene oxide disperisions were obtained. Transmission electron microscopy (TEM) and optical microscope shows that the single layer graphene oxide sheet can reach80μm×50μm.Stable large sized graphene dispersions were obtained by using hydrous hydrazine to reduce large sized graphene oxide sheets in DMF/H2O (9:1). TEM and optical microscope shows that the single layer graphene sheet can reach25μm×20μm. Hydrous hydrazine had showed obvious effects on chemical reduction, which was proved by fourier transform infrared spectroscopy(FTIR), Raman spectroscopy,thermogravimetry analysis (TGA), X-ray diffraction (XRD) analysis and X-ray photoelectron spectroscopy (XPS).Simply tip sonicating graphite in DMF and Chloroform for less than1h, followed by centrifugation, gives dispersed graphene at concentration up to1.7164mg/ml and0.4758mg/ml. TEM shows that those dispersions consist of graphene flakes of～1μm length and with a thickness of less than5layers. FT-IR and TGA shows that the as-prepared graphene had relatively high thermal stability and was not heavily oxided.