ABSTRACT
Carbon is a very important element in the periodic table that essentially forms the basis of life on Earth. Elemental carbon exists in two natural allotropes, diamond and graphite, having sp3-and sp2-hybridized carbon atoms, respectively. Both these allotropes of carbon represented the carbon family for a long time, until the discovery of fullerene in 1985.1,2
The serendipitous discovery of fullerene, also known as buckminsterfullerene, by Kroto and Smalley2 marked the beginning of an era of synthetic carbon allotropes from the naturally occurring diamond and graphite. Soon after the discovery of 0D fullerene, the synthetic carbon family has been graced by the addition of quasi-1D carbon nanotubes (CNTs), whose discovery in 1991 by Iijima3 created a boom in the scienti c world. Their large length (up to several microns) and small diameter (a few nanometers) result in a large aspect ratio. They can be seen as the nearly 1D form of fullerenes. Therefore, these materials are expected to possess additional interesting electronic, mechanical, and molecular properties. Especially in the beginning, all theoretical studies on CNTs focused on the in‰uence of the nearly 1D structure on molecular and electronic properties. More recently, the discovery of graphene by Novoselov and Geim4 made it a ‰agship material harbingering the age of nanotechnology. Graphene is also advertised as a mother of all synthetic carbon allotropes with its 2D structure.5 The arrangement of carbon atoms in each crystal is the fundamental difference between these various structures.6
