News — rGO

Graphene oxide is part of the graphene family – two dimensional materials based on a honeycomb framework of carbon atoms. While graphene is pure carbon, graphene oxide has a series of oxygen functionalities decorating the surface of the honeycomb carbon structure. The oxygen functional groups can be complex, often containing alcohol, acid and epoxy units.

The presence of oxygen groups leads to significantly different properties when comparing graphene and graphene oxide. For example, graphene oxide can disperse easily in water, while graphene will not disperse. This is because the oxygen groups make graphene oxide a hydrophilic material, allowing water molecules to intercalate between the layers, separating them and forming a stable dispersion. As graphene is a hydrophobic material, this does not occur when trying to disperse graphene in water.

Another interesting difference between graphene and graphene oxide are their conductive properties, in terms of both thermal and electrical conductivity. While graphene has exceptionally high conductivity, graphene oxide is considered an insulator. Both materials have the same carbon framework, and as such the difference in functionality is directly related to the presence of the oxygen groups. The lower the oxygen content in graphene oxide, the higher the conductivity of the material.

There are some instances where the dispersion characteristics of graphene oxide are needed, but the properties of graphene are more relevant. In these instances, it is sometimes possible to convert graphene oxide into a material more similar to graphene in situ. This is done by reducing the graphene oxide, either chemically or thermally, to leave reduced graphene oxide. Reduced graphene oxide has a significantly lower oxygen content than graphene oxide, resulting in properties much closer to those of graphene. Reduced graphene oxide is distinguished from graphene because it will not have a pristine surface – the removal of oxygen groups usually leaves some defects on the surface, including some remaining oxygen functionality. For many applications, the surface of reduced graphene oxide is appropriate for yielding the desired functionality, in other instances the defects can lead to new, different properties for the material which make it interesting in its own right.

For more information on graphene oxide and how it could be of use for your research, please get in touch and a member of our team will be happy to discuss your work.

The GOgraphene Team have been investigating how to reduce graphene oxide to rGO

The GOgraphene team believe that understanding graphene oxide is the key to finding suitable applications. For many applications, the properties of reduced graphene oxide rather than graphene oxide are required by the user. It is well known that graphene oxide can be reduced through either chemical or thermal treatments, however the GOgraphene team wanted to obtain their own data. Considering the thermal reduction of graphene oxide, the GOgraphene team decided to investigate how to reduce their graphene oxide.

A small sample of graphene oxide flake was placed in a convection oven at 200 °C and left for 15 minutes. The material removed from the oven was visually different from the graphene oxide flake used. The relatively even size distribution of brown/amber coloured graphene oxide discs had become black, with variable shapes and sizes observed.

XPS analysis was conducted to determine how much the oxygen content within the material had dropped by. The graphene oxide flake used had an oxygen content of 21.2% before thermal treatment and 12.9% after treatment. This coincides well with the TGA (thermogravimetric analysis) carried out on GOgraphene’s graphene oxide flake which shows multiple decomposition steps when analysed between ambient and 1000 °C. Based on the TGA data, to achieve full reduction the GOgraphene team would predict that the sample would need to be heated to 350 – 550 °C.

In the future, the GOgraphene team intends to continue the investigation of thermal reduction of graphene oxide to rGO (reduced graphene oxide), with the intention of understanding how low the oxygen content can be driven. The team will also expand their work to examine chemical reductions, which in some applications may be more suitable than thermal reduction. In the meantime, the GOgraphene team hope that those interested in learning more about how to reduce graphene oxide find this latest news both interesting and useful. If you have any questions, please get in touch.