▎ 摘　　要

A novel route is proposed to produce graphite nanoplatelets (GNPs) and graphene sheets. The natural graphite flakes were directly exfoliated by ultrasonication in formic acid. A stable graphene aqueous dispersion was obtained using the as-produced GNPs after two processing steps: (i) chemical oxidation of GNPs to graphite oxide nanoplatelets (GONPs); and (J) chemical reduction of graphite oxide nanoplatelets to graphene. The total duration for oxidation and production of stable graphite oxide colloid was significantly shortened due to the use of exfoliated GNPs with large surface area. The work proposed here has several advantages over the previous methods, including a high efficiency of exfoliation process, the use of a non-toxic, environmental-friendly intercalant and the capability for mass production of graphene for industrial applications. (C) 2009 Elsevier Inc. All rights reserved.