Preparation of graphite nanosheets by combining microwave irradiation and liquid-phase exfoliation

We demonstrate a series of experinvolving pretreatment with acid-based solvents, microwave irradiation, and post treatment with organic solvents to prepare graphite nanosheets from graphite powders. It was confirmed by microstructural observation and XRD analysis that a 24 h acid pretreatment forms a graphite intercalation compound (GIC) and a 90 s microwave irradiation promotes exfoliation behavior during transformation into expanded graphite. In the post treatment with organic solvents (liquid-phase exfoliation), the average thickness of prepared graphite nanosheets was influenced dominantly by the surface energy (or surface tension) of the solvent. However, the yield of graphite nanosheets was strongly proportional to the solvent viscosity. The exfoliation of graphite with the series of experiments was successfully conducted and finally transformed into nanosheets with an average thickness of 2.86 nm and a yield of 80% by using 1-cyclohexyl-2- pyrrolidone in the liquid-phase exfoliation.