GO nano

While graphene continues to dominate the materials landscape, its less celebrated cousin graphene oxide (GO) is gaining its own following. GO can be used to synthesize graphene, but it also has some fascinating properties in its own right; although naturally insulating, its electronic properties can be manipulated by selective reduction. However one problem with GO is that the usual method of production results in particles with a range of sizes. If GO is ever to be used commercially, then the particle size will have to be considerable more uniform.

 

GO is typically formed by oxidizing graphite powders. As the material is processed, the particles are broken up, with the result being a collection of GO sheets with vastly different sizes; ranging from nanometers to micrometers. Research being performed by Assistant Professor Jiaxing Huang and colleagues at Northwestern University may have solved this problem, as the group has been able to consistently produce GO nanoparticles [Luo et al., JACS (2010) doi:10.1021/ja1078943].

 

The key to the production of the sub-100 nm sheets was to use graphite nanofibers rather than a regular powder. The result was GO sheets that were far more uniform than those produced using standard methods. By altering the reaction time, average sizes of between 50 and 20 nanometers were obtained, demonstrating that the size can be easily tuned.

 

However, the most exciting result was the revelation that nanoparticles in solution act very differently to regular particles. Due to the higher charge density at the particle edges, the nanosheets are more hydrophilic, and so are less eager to move to the surface. This not only means that GO can remain dispersed within water droplets, but also explains why the nanocolloids are far less prone to precipitation.  According to Huang, “The enhanced stability is important for the solution-processing of these graphene materials in applications like energy storage and polymer composites.” “Our work shows that going nano can greatly change a material's solution properties”.

 

The Northwestern team believes that the increased stability of the nanocolloids makes them excellent candidates for use as dispersal agents for insoluble materials, such as carbon nanotubes. This new application of GO could mean that it’s possible to create a host of new materials; an avenue of research that Huang is keen to explore. “Since we can use GO to disperse carbon nanotubes, next we would like to create functional composite materials entirely made of carbon nanomaterials for energy related applications.”