What is Fullerene?
Fullerene is a general term for cage-like carbon atom clusters, including C60/C70 molecules, carbon nanotubes, onion-like fullerenes, etc. Fullerene materials can be prepared by laser gasification of graphite in ultrasonic nitrogen flow, or by arc method with graphite rods as electrodes or by plasma method. In fullerene materials, a non-planar five-membered or six-membered ring constitutes a closed hollow spherical or ellipsoidal structure of conjugated alkenes, also known as carbon spheres. The fullerene carbon spheres that have been isolated are mainly C60 and C70, etc. The molecular structure of C60 is spherical 32-hedron, which is a football-shaped hollow symmetrical molecule formed by 60 carbon atoms connected by 20 six-membered rings and 12 five-membered rings. C60 is the most stable fullerene material. Fullerene materials have been used in optical, electrical and magnetic materials due to their superconductivity, soft ferromagnetism and nonlinear optical effects.
Figure 1. Structure of C60
What are the Application of Carbon Nanotubes?
- Fullerene for Hard Materials: The structure of cage fullerenes gives them special stability, hardness is harder than diamond, and ductility is 100 times stronger than steel. Since fullerenes are easily soluble in non-polar organic molecular solvents such as benzene and toluene, complex surfaces can be directly immersed in the organic solution at room temperature, and a film of fullerene molecules is left after the solvent evaporates. This layer of film gives the material high hardness and can be used in high-strength operations, such as gears with high hardness surface, high-strength fibers covered with a thin layer of fullerene can be used as wire saws, and the surface of armored vehicles is covered with a thin layer of fullerene for impact resistance.
- Fullerene for Lubricant: The molecules in the spherical fullerene material are spherical in shape. At the molecular level, these spherical molecules are hard and stable and can act as "molecular balls" to make lubricants.
- Fullerene for Memory: Fullerene carbon materials are generally non-conductive. But inserting alkali metals (lithium, sodium, potassium, ruthenium, cesium) or alkaline earth metals (beryllium, magnesium, calcium, strontium, barium, radium) between fullerene materials can change the conductive properties of this new compound. Some can become metallic conductors, and some are even superconductors. For example, the rare earth element "gadolinium" wrapped in C60 is a material with special optoelectronic and magnetic properties. This material is made into a polymer with polyethylene, which can be used as a flash memory with excellent performance.
- Fullerene for Optical Device: C60 can accept visible light in a wide range and has a high photoelectric conversion rate. It is a good material for photosensitive elements. By combining some material molecules with good optical properties with C60, better optical materials will be obtained. For example, combining C60 with a photostatic material can replace the photosensitive material in a copier.
- Fullerene for Hydrogen Storage and Oxygen Storage: The hydrogenated compound of fullerene is very stable, and the fullerene material can safely collect and store hydrogen in large quantities. As a material for storing hydrogen, fullerenes can be used in hydrogen purification, absorption, hydrogen combustion engines and "hydrogen-air fuel cells". It has an important position in clean energy. C60 can also be used to store oxygen and plays an important role in absorbing, purifying and storing oxygen.
- Poulomi Bhakta, Bhavna Barthunia. Fullerene and its applications: A review[J]. Journal of Indian Academy of Oral Medicine and Radiology, 2020, 32(2), 159-163.