▎ 摘　　要

We developed an efficient method for exfoliating pristine graphite in an organic solvent to produce a high yield (14%) and high concentration (5.25 mg/mL) of well-dispersed mono-, bi-, and multi-layered graphene sheets. Pre-thermal activation of pristine graphite at 900 degrees C in a sealed stainless steel bath under high pressure, followed by sonication in a solvent of 1-methyl-2-pyrrolidinone at elevated temperatures produced a solution of homogeneous, well-dispersed, defect-free, and non-oxidized graphene. The resulting electrical conductivities of the graphene sheets were high, up to 849 S/cm. (c) 2014 Elsevier B.V. All rights reserved.