Pliable carbon

Researchers have made graphene paper. Graphene is the net of carbon atoms, reminiscent of chicken wire, that forms graphite and carbon nanotubes.

In graphite, electrostatic forces make graphene layers cling together and form microscopic stacks, says Rodney Ruoff, a physical chemist at Northwestern University in Evanston, Ill. Different stacks don’t stick together well, which is why pencil lead is soft. But a graphene layer itself is one of the strongest materials in nature, Ruoff says.

Ruoff’s team sought to take the layers apart and reassemble them in a new way. The researchers oxidized graphite and shook it in water, producing a suspension of graphene fragments up to 1 micron wide in which about every other carbon atom was strongly bonded to an oxygen atom.

After most of the water has been filtered out, the fragments stuck together to create a new material in the form of a pliable sheet. Remaining water molecules held graphene layers less than a nanometer apart, the team reports in the July 26 Nature. “Water is playing the role of a sort of molecular glue,” Ruoff says.

The graphene paper is about as strong as aluminum foil, but Ruoff says that replacing water with better molecular glues could lead to new, superstrong materials.