Fullerenes, nanotubes, onions and related carbon structures

Fullerenes, containing five- and six-membered carbon rings, of which C60 and C70 are the prominent members, exhibit phase transitions associated with orientational ordering. When C60 is suitably doped with electrons, it shows novel superconducting and magnetic properties. We review these and other properties of fullerenes in bulk or in film form along with the preparative and structural aspects. Carbon nanotubes and onions (hyperfullerenes) are the other forms of carbon whose material properties have aroused considerable interest. Besides discussing these new forms of carbon, we briefly introduce other possible forms, such as those involving five-, six- and seven-membered rings and hybrids between diamond and graphite.