Models of nanotubes
Nanotubes are formed by rolling up a graphene sheet into a cylinder and capping each end with half of a fullerene molecule. Shown here is a (5, 5) armchair nanotube (top), a (9, 0) zigzag nanotube (middle) and a (10, 5) chiral nanotube. The diameter of the nanotubes depends on the values of n and m.