Preparation of colloidal dispersions of graphene sheets in organic solvents by using ball milling

Abstract

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 40mJ m- 2, such as in N,N-dimethylformamide, at a concentration up to 0.08mg ml - 1, achieving a yield higher than 32.0wt. The graphene materials in the colloidal suspension were characterized using scanning and transmission electron microscopy and atomic force microscopy. Copyright © 2010 Weifeng Zhao et al.