To fully exploit the excellent properties of graphene, scientists need to be able to produce few and single-layer nanosheets in a simple way, explains Barron. The sheets also need to be soluble in a non-polar solvent that allows for typical organic reactions. "Our work achieves both of these goals," he told

Easily scaled up
The new method involves dispersing various graphitic materials in ortho-dichlorobenzene (ODCB) and then applying a sonic probe to the solutions. The technique can easily be scaled up, unlike most other methods to produce graphene. It also avoids the use of harsh oxidizing chemicals and the sheets produced have high electrical conductivity.

The "peeling off" technique to produce graphene (the method used to first isolate graphene by Andre Geim's group at the University of Manchester) is impractical for large-scale manufacture, as is epitaxial vapour deposition. Another common approach, oxidizing to graphite oxide using strong chemicals, is not only toxic for the environment but produces graphene that contains significant defects, say the researchers. This is because the chemicals disrupt the regular hexagonal carbon lattice in the material.

The team hopes that its work will encourage other scientists to expand on the different types of chemistry experiments that can be performed on graphene nanosheets. These include functionalization of the materials, something that will be essential for making devices.

Spurred on by their results, Barron and co-workers say that they are now looking at using graphene sheets in energy applications, such as transparent electrodes for solar cells, for example. Graphene might also be employed as the anode material in lithium batteries, as well as to help improve capacitors thanks to the very high surface of electrodes potentially made of the material.

They reported their work in Nano Letters.