Catalytic unzipping of carbon nanotubes to few-layer graphene sheets under microwaves irradiation

Catalytic unzipping of single-, double-, and multi-walled carbon nanotubes (SWNTs, DWNTs, and MWNTs), in the presence of Pd nanoparticles and an oxygen-containing liquid medium, to yield the few-layer graphene sheets, was performed under microwaves irradiation. In this unzipping process, the palladium particles act as a pair of scissors to cut the nanotube lengthways. Theoretical simulations with Reactive Forcefields confirm that the presence of Pd nanocatalysts and oxygen next to vacancies facilitate the unzipping process to form graphene from nanotube by significantly lowering the corresponding energy barrier. This synthesis method makes a link between nanotubes and graphene sheets, yielding a significant amount of graphene (between 4 and 8 wt.% with respect to the starting carbon material). Compared to previous methods, scaling-up can easily be achieved by increasing the number of synthesis reactors, leading to gram-amounts of graphene. (C) 2009 Elsevier B.V. All rights reserved.