Preparation of Colloidal Dispersions of Graphene Sheets in Organic Solvents by Using Ball Milling

A top‐down method was developed for producing colloidal dispersions of graphene sheets. Graphite nanosheets comprising hundreds of carbon layers were dispersed and gently ball‐milled to exfoliate into graphene in a variety of organic solvents. After 30 hours of the shear‐force‐dominated grinding and a subsequent 4000 r.p.m. of centrifugation, single‐ and few‐layer graphene sheets were readily prepared and homogeneously and stably suspended in the good solvent medium which possesses a surface tension value close to 40 mJ m−2, such as in N,N‐dimethylformamide, at a concentration up to 0.08 mg ml−1, achieving a yield higher than 32.0 wt%. The graphene materials in the colloidal suspension were characterized using scanning and transmission electron microscopy and atomic force microscopy.