Fullerenes are molecules that composed entirely of carbon. They are similar in structure to graphite, which is composed of a sheet of linked hexagonal and pentagonal rings that prevent the sheet from being planar. Each carbon atom on the surface of fullerenes is bonded to three carbon neighbors, therefore, is sp2 hybridized. Fullerenes are in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical fullerenes C60, the first fullerene molecule manufactured in 1985, is named as buckminsterfullerene, resembles the balls used in football. Cylindrical fullerenes are known as carbon nanotubes (CNTs). As the discovery of fullerenes came after buckminsterfullerene, the shortened name “fullerene” is used to refer to the family of fullerenes, of which each carbon atom is covalently bonded to three others.
The most specific feature of fullerenes is that they are excellent electron acceptors (n-type semiconductors), which are suitable for organic electronic materials with electron carriers. Fullerenes can be used to fabricate polymer/fullerene blend for organic photovoltaics, in which fullerene acts as the n-type semiconductor. Fullerenes are powerful antioxidants, which react readily and at a high rate with free radicals. These free radicals usually lead to cell damage or death. Therefore, fullerenes show great promise in health and personal care applications, in which the prevention of oxidative cell damage or death is desirable. Fullerenes are also used in non-physiological applications, where oxidation and radical processes are destructive (food spoilage, plastics deterioration, metal corrosion). Research interests on fullerenes include also the use of fullerenes to control the neurological damage of diseases such as Alzheimer’s disease and Lou Gehrig’s disease. Fullerenes are used as additives for polymers to create copolymers or composites with specific physical and mechanical properties. Fullerenes can be doped with rubidium and cesium to fabricate superconductors with electron carriers, of which the superconducting transitions occur at more than 30 K.
