Stiff and strong

Researchers at Northwestern University have fabricated a new type of paper that could find use in a variety of applications.

To create the paper, the researchers, led by Prof Rod Ruoff from the McCormick School of Engineering and Applied Science, first oxidised graphite to create graphite oxide, which falls apart in water to yield well-dispersed graphene oxide sheets.

After filtering the water, the team was able to fabricate pieces of graphene oxide 'paper' more than five inches in diameter and with thicknesses from about one to 100 microns, in which the individual micron-sized graphene oxide sheets are stacked on top of each other.

In addition to their superior mechanical properties as individual sheets, the graphene oxide layers stack well, which could be key to the development of other materials.

‘You can imagine that these microscale sheets may be stacked together and chemically linked, allowing us to further optimise the mechanical properties of the resulting macroscale object,’ Ruoff said. ‘This combination of excellent mechanical properties and chemical tunability should make graphene-based paper an exciting material.’

Of further interest are the electrical properties of the graphene oxide paper in comparison to graphene sheets. ‘When we oxidise the graphene sheets to create graphene oxide, the material goes from being an electrical conductor to an electrical insulator,’ Ruoff said.

‘This is an important step and in the future it will be possible to tune the material as a conductor, semiconductor or insulator. One will be able to control the electrical properties without sacrificing exceptional mechanical properties.’

Ruoff sees a wide variety of applications for graphene oxide paper, including membranes with controlled permeability, and for batteries or supercapacitors for energy applications. Graphene oxide paper could also be infused to create hybrid materials containing polymers, ceramics or metals, where such composites would perform much better than existing materials as components in, for example, aeroplanes, cars, buildings and sporting goods products.