1. Carbon nanotubes

The basic element of life as we know it, carbon is an astonishing atom, capable of forming a wide variety of chemical bonds with other carbon atoms. This versatility is due to carbon's particular electronic structure, which makes it bi-, tri- or tetravalent. It is therefore possible to encounter one-, two- or three-dimensional forms of carbon, known as allotropic forms of carbon.

Hexagonal graphite is the thermodynamically stable form of carbon under normal temperature and pressure conditions, all other forms being thermodynamically unstable or metastable.

The best-known three-dimensional structure of carbon is diamond, where the atoms are tetravalent. Graphite has a lamellar structure made up of a stack of sheets, each made up of trivalent carbon atoms forming a two-dimensional hexagonal lattice. Graphene is an isolated sheet of graphite,...