Graphene is a material of growing technological importance due in part to its outstanding properties, numerous and potential applications.

A significant amount of time has been spent in the development and synthesis of graphene with mono- or a few layers; including micro mechanical exfoliation of highly ordered pyrolytic graphite (HOPG), chemical reduction of exfoliated graphite oxide (GO), epitaxial growth, chemical vapor deposition (CVD), thermal exfoliation, bottom-up assembly, electrostatic deposition, liquid phase exfoliation of graphite, arc-discharging and the solvothermal method. In these methods, reduction of GO and liquid phase exfoliation of graphite have been both reliable and reproducible with the opportunity to produce transparent graphene thin films in large scales with increased conductivity. These methods utilized the concept of graphite intercalation compounds (GICs), which have been widely used as precursors for exfoliated graphite (EG) in industry.

Gu and his co workers [Gu et al., doi: 10.1039/b904093p J. Mater. Chem., 2009, 19, 3367] used natural graphite as a starting material whose bonding forces hold parallel graphene sheets in weak van der Waals forces. The spacing between the graphene sheets can be opened significantly to provide a marked expansion in the c direction and thus form an expanded or intumesced structure. In this paper, Gu et al., present a liquid phase exfoliation of worm-like exfoliated graphite (WEG) to prepare graphene sheets of high quality. WEG was prepared by a conventional acid process combining with thermal exfoliation. The obtained WEG was subjected to a final exfoliation to obtain a monolayer or a few layers of graphene sheets by ultrasonication and centrifugation of a 1-methyl-2-pyrrolidinone (NMP). Ultrasonication for 30 min yielded a uniform dispersion which was then centrifuged at 600 rpm for 30min. The top half of the dispersion was collected for further characterization. The microstructure of the graphene sheets was examined using scanning electron microscopy and high resolution transmission electron microscopy. The HRTEM characterization in particular gives further evidence for the perfect crystalline structure of the graphene sheets. Optical diffraction, also known as fast Fourier transformation (FFT), shows a hexagonal pattern revealing the six-fold symmetry feature of graphene. The perfect lattices indicate the absence of topical defects in graphene.

This approach combined with the advances in large scale industry manufacturing of WEG could potentially lead to the development of new and more effective graphene products. Work continues to further verify and improve reproducibility of the production of Graphene sheets from worm-like exfoliated graphite.