The Many Faces of Carbon

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Yesterday the Royal Swedish Academy of Sciences announced that this year's Nobel Prize in Physics will go to Andre Geim and Konstantin Novoselov "for groundbreaking experiments regarding the two-dimensional material graphene." Graphene is one of many allotropes, or forms, of the element carbon. Carbon is special because it has so many different allotropes (the main ones are highlighted below), many of which have special characteristics:

Diamond: Carbon atoms line up and bond together in a tight lattice to create this extremely hard, transparent natural substance. The diamonds people dig up today were formed 100 miles or more beneath the Earth's surface where the carbon was subjected to tremendous heat and pressure more than a billion years ago. Manufacturers can now also grow diamonds in a lab to create jewels or for industrial purposes.

Graphite: The soft lead in a pencil is really graphite, a flaky, flexible hexagonal lattice of carbon atoms. Unlike diamond, graphite is soft and conducts electricity.

Graphene: This thin sheet of carbon is just one atom thick. Geim and Novoselov created the first sheet of graphene by using a simple piece of adhesive tape to lift up a flake of carbon off of graphite. Graphene is a good conductor of electricity, and scientists think it might be useful in technologies such as touch screens and solar cells. (An interesting side note: Geim is the first person ever to win both a Nobel Prize and an Ig Nobel. He was awarded the Ig Nobel in 2000 for levitating a frog with magnets.)

Buckminster-fullerenes: These hollow carbon molecules, whose discoverers were awarded the 1996 Nobel Prize in Chemistry, get their name from their resemblence to the geodesic structures of Bucky Fuller. The molecules come in sphere shapes—called buckyballs—and can also be fashioned into carbon nanotubes, which are 100 times stronger than steel but one-sixth the weight.

Carbon nanofoam: This foam, made entirely of carbon atoms, is one of the least dense substances in the world. Carbon in this form acts as a semiconductor and is magnetic.

Not all carbon, however, joins together into complex crystalline structures with special properties. The jumbled up form is called amorphous carbon.

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