Kids, every time someone writes a line with a pencil, the resulting mark includes bits of the hottest new material in chemistry and nanotechnology: graphene. What do graphite, diamond, and fullerene (aka buckyball) have in common? They are all made of pure carbon! In chemistry terms they are called “allotropes”. And now the latest addition to the family is graphene. Graphene is a single carbon sheet that is one atom thick where the carbon atoms are bonded to each other in a network of repeating hexagons to form a honeycomb array. Believe it or not, the film is stronger than diamond. And it conducts electricity about 100 times better than silicon. These properties make graphene the thinnest material out there, in addition to the strongest.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Graphene comes from graphite, the “lead” in a pencil: a kind of pure carbon formed from flat, stacked layers of atoms. The layered structure of graphite has been known for many years. Graphene is the name given to one sheet of graphite.
Researchers can split graphite crystals into progressively thinner wafers by scraping or rubbing them against another surface. This is called “micromechanical cleavage”. They simply stick a flake of graphite onto plastic adhesive tape, fold the sticky side of the tape over the flake and then pull the tape apart, cleaving the flake in two. As the process is repeated, the resulting fragments grow thinner and thinner until they are only one atom thick. They have high crystal quality and are chemically stable.
We encourage you to watch a YouTube video, “Making Graphene 101, Ozyilmaz' Group” at http://www.youtube.com/watch?v=rphiCdR68TE and try this yourself with an adult partner. As a less involved experiment, just use the side of a pencil tip to fill in an area about 2” square on a sheet of paper, then use adhesive tape on the markings. Use another piece of tape to peel off more from the tape, repeat, and observe what is lifted up.
Commercial applications may be on the way, now that newer methods have been developed that involve etching the carbon away from a silicon, copper, or nickel base. Potential uses include cell phones, touch screens, solar cells, and other energy storage and electronic applications.
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
November 2009
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References:
http://chemistry.about.com/b/2009/07/12/have-you-heard-about-graphene.htm and
April 2008 Scientific American Magazine, “Carbon Wonderland” by Andre K. Geim and Philip Kim.
