John Aebi-Magee
August 5, 2007

Researchers at Northwestern University have fabricated a new type of paper that they hope will create a revolution. This remarkably stiff and strong yet lightweight material should find use in a wide variety of applications. The stiffness and strength should be superior to all other materials, with the possible exception of diamond.

In a paper published July 26 in the journal Nature, researchers led by Rod Ruoff, Professor of Nanoengineering in the Robert R. McCormick School of Engineering and Applied Science, report on the development of "graphene oxide paper."

Ruoff’s research team was the first to develop graphene-based composite materials, which was reported in Nature last year. Graphene -- a sheet of carbon only one atom thick -- has the potential to serve as the basis of an entirely new class of materials.

To form the graphene oxide paper, the group oxidized 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.

“I have little doubt that very large-area sheets of this paper-material could be made in the future,” Ruoff notes. 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.

Of further interest are the electrical properties of the graphene oxide paper in comparison to graphene sheets. “When we oxidize the graphene sheets to create graphene oxide, the material goes from being an electrical conductor to an electrical insulator,” Ruoff says. “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, airplanes, cars, buildings and sporting goods products.

These transparent thin films could find applications in solar cells or a variety of transparent electronics such as electronic paper and flexible color screens. The processing of these films may provide a cheaper alternative to the widely used indium tin oxide coatings that are typically used as the transparent conductive film.

The development of this paper-like material is the latest of several recent advancements by Ruoff’s team in launching the new field of graphene-based materials. For more information, see the full story at the McCormick School of Engineering and Applied Science web site.