A new form of carbon called graphene was discovered by British scientists in 2004. It consists of  a single layer of atoms bonded in a hexagon pattern, similar to chicken wire. The graphite component in pencil lead is a stack of many tiny layers of graphene. The two-dimensional carbon structure has unusual properties. For example, it is one of the strongest materials known. If a large sheet could be fabricated, it would take an elephant, balanced on a pencil, to break through the surface. Thus far, however, such sheets are not available. Graphene fragments have only been made on the microscopic level.

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Graphene structure

Graphene makes an excellent sensor for chemicals because it is entirely surface area, both top and bottom, with no interior volume. A single molecule adsorbed onto graphene changes its conduction of electricity in a measureable way. The conductivity of graphene can also be controlled with external electric fields. That is, the material can be turned on as a conductor, or turned off as an insulator. This behavior is the key to the semiconductors used throughout solid state electronics, and graphene eventually may replace silicon in modern technology.

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