Direct exfoliation of natural graphite into micrometre size few layers graphene sheets using ionic liquids

Abstract
Stable high-concentration suspensions (up to 0.95 mg mL−1) of non-oxidized few layer graphene (FLG), five or less sheets, with micrometre-long edges were obtained via direct exfoliation of natural graphite flakes in ionic liquids, such as 1-butyl-3-methyl-imidazolium bis(trifluoro-methane-sulfonyl)imide ([Bmim]-[Tf2N]), by tip ultrasonication.