▎ 摘　　要

A simple and effective method for the preparation of a few layered graphene nanoflakes directly from graphite has been successfully demonstrated. Mild ultrasonication of highly ordered pyrolytic graphite, in presence of a cationic surfactant cetyltrimethylammonium bromide and acetic acid yielded graphene nanoflakes, which formed a stable colloidal suspension in organic solvent such as N,N-dimethyl formamide. Scanning and transmission electron microscopic analyses showed that the dispersed phase consist of mainly few layered graphene nanoflakes. Average thickness of the flakes was found to be similar to 1.18 nm. Energy dispersive X-ray analysis indicated the absence of graphene oxide. Field emission measurements for the nanoflakes showed a turn on voltage of 7.5 V/mu m and emission current densities of 0.15 mA/cm(2). (C) 2009 Elsevier Ltd. All rights reserved.