 Carbon nanotube

A carbon nanotube is a cylindrical carbon nanostructure with a graphitic bonding framework. Single-walled tubes can be described by the way a graphene-like sheet wraps around the cylinder; multiwalled tubes contain nested shells.

Diameter and wrapping geometry influence electronic and optical properties, including whether an idealized tube behaves as metallic or semiconducting. Thus carbon composition alone cannot predict the behavior of a particular nanotube.