Cationic surfactant mediated exfoliation of graphite into graphene flakes

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 ∼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/μm and emission current densities of 0.15 mA/cm2.