The discovery of graphene—a one-atom-thick sheet of carbon atoms arranged in a honeycomb pattern that boasts outstanding mechanical and electronic properties--has won physicists Andre K. Geim, 51, and Konstantin S. Novoselov, 36, both of the University of Manchester, in the U.K., the 2010 Nobel Prize in Physics. The researchers will share nearly $1.5 million in prize money.
The idea that a single "freestanding" sheet of graphene—meaning a one-atom-thick carbon film that rests on or is suspended from but is not tightly attached to a support—could be isolated, had been investigated since the 1980s, when carbon nanotubes and buckeyballs were discovered.
Yet after years of trying unsuccessfully to separate graphite into its constituent graphene sheets, researchers had concluded by the early part of this decade that freestanding graphene could not be isolated. Thermodynamics principles predicted that the material would spontaneously roll up into a nanotube or other curved structure. "At that time, graphene was considered a hypothetical or academic material," Geim told C&EN in 2009 .
THE STORY could start even earlier because graphite has been used as pencil "lead" for centuries, which means that graphene actually has been close at hand for a very long time. Every time someone scribes a line with the ubiquitous pencil, the resulting mark contains bits of this hot "new" material, Geim says. But graphene isn't readily available in freestanding, single-sheet form in ordinary pencil markings, so its properties cannot be explored or exploited.
Not surprisingly, scientists have been trying for a long time to split graphite into its constituent parts. For years, their efforts met with little success. Early on, researchers tried a chemical method for thrusting molecules or atoms in between graphite's layers to pry apart the graphene sheets. This chemical exfoliation technique generally yielded a slurry or sludge of graphitic particles similar to wet soot. The chemical method soon gave way to a mechanical approach to cleaving graphite.
By rubbing or scraping graphite against a surface, researchers managed to peel off microscopic chunks as thin as roughly 100 atomic layers. Referred to as micromechanical cleavage, that method was taken up by scientists in many labs and worked well enough almost 20 years ago to produce graphite slivers that were optically transparent. Yet the slices still weren't atomically thin.
Yet in 2004, Geim and Novoselov, who was a postdoc at that time, worked out a surprisingly simple method for exfoliating little chips of graphite by folding adhesive tape against the crystals and peeling apart the tape repeatedly. The team showed that not only could single sheets of graphene be isolated, but they remain particularly stable at room temperature (Science 2004, 306, 666).
The discovery of that rudimentary method for isolating graphene sheets led to an explosion in graphene research. The material has quickly become a top choice for advanced computing applications, digital displays and other types of flexible electronics, and advanced composite materials. Experts contend that graphene's usefulness is only just beginning to be discovered.
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