A Northwestern University professor and his students have found a new way of turning graphite oxide – a low-cost insulator made by oxidising graphite powder – into graphene, a hotly studied material that conducts electricity.
The process was invented by Jiaxing Huang, assistant professor of materials science and engineering at Northwestern’s McCormick School of Engineering and Applied Science, his graduate student Laura Cote and postdoctoral fellow Rodolfo Cruz-Silva.
Materials scientists have previously used high-temperature heating or chemical reduction to produce graphene from graphite oxide. However, these techniques could be problematic when graphite oxide is mixed with another material, such as a polymer, because the polymer component may not survive the high-temperature treatment or could block the reducing chemical from reacting with graphite oxide.
In Huang’s flash reduction process, researchers simply hold a consumer camera flash over the graphite oxide and, a flash later, the graphene if formed.
Huang said: ‘The light pulse offers very efficient heating through the photothermal process, which is rapid, energy efficient and chemical free.’
When using a light pulse, photothermal heating not only reduces the graphite oxide, but it also fuses the insulating polymer with the graphene sheets, resulting in a welded conducting composite.
Using patterns printed on a simple overhead transparency film as a photo-mask, flash reduction creates patterned graphene films. This process creates electronically conducting patterns on the insulating graphite oxide film – essentially a flexible circuit.
Next, the research group hopes to create smaller circuits on a single graphite-oxide sheet at the single-atom layer level. The current process has been performed only on thicker films.
‘If we can make a nano circuit on a single piece of graphite oxide, it will hold great promise for patterning electronic devices,’ added Huang.