Graphene dispersion in a surfactant-free, polar solvent

Here, we demonstrate dispersion of graphene nanoplatelets (GNPs) in ethylene glycol (EG), a polar dispersion medium, by a liquid-phase exfoliation method involving sonication and centrifugation. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy are used for qualitative and quantitative characterization of the graphene dispersions. TEM micrographs confirm the exfoliation and production of monolayer GNPs after sonication. Statistical analysis of TEM micrographs shows that increasing the sonication time increases the degree of exfoliation of GNPs. Raman spectroscopy studies also show that high-power probe sonication exfoliates multi-layer GNPs to few-layer GNPs. The proposed method is promising to provide monolayer and few-layer graphene dispersed in a polar medium, practical to multiple engineering applications including polymer nanocomposites.