New Carbon Nanomaterial

A simple chemical trick changes graphene into a compound with different electronic properties.

Graphene, a single layer of carbon atoms arranged in a honeycomb-like structure, has captured worldwide interest because of its attractive electronic properties. Now, by adding hydrogen to graphene, researchers at the University of Manchester, U.K., have made a new material that could prove useful for hydrogen storage and future carbon-based integrated circuits. While graphene is highly conductive, the new material, called graphane, is an insulator. The researchers can easily convert it back into conductive graphene by heating it to a high temperature.

Versatile graphene: When a highly conductive graphene sheet is exposed to hydrogen atoms (white), they attach to the carbon atoms (black), transforming the material into graphane, an insulator. This is the first evidence that graphene’s properties can be manipulated chemically. Credit: P. Huey/Science

Andre Geim, who led the research and first discovered the nanomaterial in 2004 with Kostya Novoselov, says that the findings suggest that graphene could be used as a base for making entirely new compounds. The hydrogenated compound graphane had been theoretically predicted before, but no one had attempted to create it. "What's important is that you can make another compound of [graphene] and can chemically tune its electronic properties to what you want so easily," Geim says.

Adding hydrogen to graphene is just one possibility. Using other chemicals could yield materials with even more appealing properties, such as a semiconductor. "Hydrogenation may not be the end of the exploration; it may be just the beginning," says Yu-Ming Lin, a nanotechnology researcher at the IBM Thomas J. Watson Research Center, in Yorkstown Heights, NY.

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The latest findings are a step toward practical carbon-based integrated circuits, which could be used for low-power, ultrafast logic processors of the future. The findings also open up the possibility of using graphene for hydrogen storage in fuel cells. "Graphene is the ultimate surface because it doesn't have any bulk--only two faces," Geim says. This large surface area would make an excellent high-density storage material.

As described in Science, the researchers make graphane by exposing graphene pieces to hydrogen plasma--a mixture of hydrogen ions and electrons. Hydrogen atoms attach to each carbon atom in graphene, creating the new compound. Heating the piece to 450 °C for 24 hours reverts it back to the original state. Geim says that the researchers did not expect to be able to make the new substance so easily.