Hernandez et al ArXiv

We have demonstrated a method to disperse and exfoliate graphite to give graphene suspended in water-surfactant solutions. Optical characterisation of these suspensions allowed the partial optimisation of the dispersion process. Transmission electron microscopy showed the dispersed phase to consist of small graphitic flakes. More than 40% of these flakes had <5 layers with ~3% of flakes consisting of monolayers. These flakes are stabilised against reaggregation by Coulomb repulsion due to the adsorbed surfactant. However, the larger flakes tend to sediment out over ~6 weeks, leaving only small flakes dispersed. It is possible to form thin films by vacuum filtration of these dispersions. Raman and IR spectroscopic analysis of these films suggests the flakes to be largely free of defects and oxides. The deposited films are reasonably conductive and are semi-transparent. Further improvements may result in the development of cheap transparent conductors. Introduction The discovery of monolayer graphene in 2004 has led to the demonstration of a host of novel physical properties in this most exciting of nanomaterials. Graphene is generally made by micromechanical cleavage, a process whereby monolayers are peeled from graphite crystals. However, this process has significant disadvantages in terms of yield and throughput. As such, there has been significant interest in the development of a large scale production method for graphene. In the long term, for many research areas the growth of graphene monolayers is by far the most desirable route. However, progress has been slow and in any case, this technique will be unsuitable for certain applications. Thus, in the medium term, the most promising route is the exfoliation of graphite in the liquid phase to give graphene-like materials. The most common technique has been the oxidisation and subsequent