Conditionally, all carbon nanostructures can be divided into fullerenes and fulleroid structures.
Fullerenes, which are also called footballens, backyball, are a chemically stable closed surface structure of carbon, in which carbon atoms are located at the vertices of regular hexagons or pentagons, regularly covering the surface of a sphere, and the pentagons are isolated from each other, i.e. they do not have common contact points either on the edges or in the vertices. The number of carbon atoms in a fullerene molecule is greater than or equal to 60.
Chemists divide fullerenes into two groups:
- light fullerenes - which include carbon C60 and carbon C70
- and heavy (higher) fullerenes - which include the rest of the fullerenes, the number of atoms in which more than 70.
"Fullerenes" with the number of carbon atoms less than 60 belong to the so - called non-fullerenes, which can have both closed and open structures. In closed structures that look like fullerenes, due to the small number of carbon atoms, there are quite strong stresses between the carbon atoms, which significantly weaken the interatomic interactions in the molecule. Open structures are associated with the shape of broken egg shells. Due to their structural features, not all fullerenes are unstable to external influences.
Fullerene is able to interact with different substances with the formation of stable structures. In this regard, its derivatives are also promising for use in various fields of science and technology. There are endohedral and exohedral derivatives (or complexes). In the first, already synthesized in macro quantities, one or more metal atoms, nonmetals, or even individual molecules are placed inside the carbon sphere. When the latter are formed, the interaction occurs on the outer surface of the fullerene.
From the variety of fulleroid structures – nanotubes, nanoarray (nanobarelle), monoplanar, neolocality and other, currently the greatest interest is carbon nanotubes.
Nanotubes are cylindrical macromolecules consisting of a folded graphite plane consisting of hexagons. As a rule, the ends of nanotubes are closed with so-called "fullerene caps". The diameter of nanotubes does not exceed several nanometers, and the length can be from one to several microns.