Fullerenes

A fullerene is an allotrope of carbon. The molecule of fullerene consists of carbon atoms, connected in a way that it forms a hollow cage-like structure. It is a molecule containing only the atoms of carbon. Fullerene C20 contains 20 atoms of carbon. Fullerene C60 is known as buckminsterfullerene. The following topics, synthesis process, properties, different types, and their applications, give an overview of fullerenes.

Fullerene as Ligands

Ligands act as the donor of electron pairs, and a central atom acts as the acceptor of these electron pairs. Fullerenes were firstly used as ligands. In the system [(Ph3)P]₂Pt(n²-C60)], Fullerene C60 acts as a legend on platinum. For this equation, platinum is the central atom. Fullerene ligands are much like electron-deficient alkenes with a deficiency of electrons. This binding occurs on the junction points of two 6-membered rings.

Synthesis of Fullerene

The arc discharge method is used to synthesise fullerenes. High current is applied between two graphite electrodes in an atmosphere of helium or argon. In this method, the negative carbon electrode gets evaporated. The soot is generated and collected on water-cooled surfaces. For collecting soot, vacuum is broken, and the soot is collected in toluene or benzene. The obtained soot is a mixture of fullerenes.

Physical Properties of Fullerene

• Solubility in Water

Fullerenes are not soluble in water and many solvents.

• Conductivity

Fullerenes cannot conduct electricity. They are insulators in their pure form. They act as superconductors or semiconductors only when they are doped with any alkali metals.

• Volatility

Fullerenes do not evaporate at normal temperatures. They are volatile in nature.

• Soft and Slippery

The intermolecular forces of fullerene are weak. Little energy is needed to overcome these forces. They are soft and slippery and have a low melting point.

Chemical Properties of Fullerene

• Solubility in organic solvents

Fullerenes are not soluble in water but can easily dissolve in organic solvents. Solvents like chlorobenzene, 1,2,3-trichloropropane, and toluene can dissolve fullerenes.

• Superconductivity

When fullerenes are mixed with alkali metals, they conduct electricity and show the properties of a superconductor.

• Catalyst

When hydrogen sulphide, H2S, is oxidised to form Sulphur (S), fullerene C60 acts as the catalyst and speeds up the process.

• Aromaticity

Fullerenes may display aromatic properties only when the number of atoms in a molecule equals to 2(N+1)2 , when N is an integer.

• Electron affinity

Fullerenes easily accept electrons and can react with free radicals. They can take more than three electrons and are a great oxidising agent.

• Ferromagnetic

Fullerenes show the property of ferromagnetism.

Types of Fullerenes

There are different types of fullerenes based on the variation in structures. Some of them are :

• Buckyball Clusters

It is one of the types of fullerene that is among the first discovered nanoparticles. Its size ranges from 20 to 60 carbon atoms. The most common size of the buckyball cluster is 60.  

• Nanotubes 

These are hollow tubes made of carbon atoms. The diameter of the atoms are usually measured in nanometres. It may have single or multiple walls. It is widely used in the electronic industry.

• Megatubes

These are larger than nanotubes in terms of the dimension of the atoms. These are generally used in transporting different molecules having different dimensions.

• Polymers

These are macromolecules. They share covalent chemical bonds. They are composed of carbon chains. Two or three-dimensional polymers are formed on exposure to high temperature or high pressure.

• Nano-onions

Nano-onions are spherical particles composed of multiple carbon layers, surrounding the core of buckyball. It is a kind of cage-within-cage-like onion.

• Linked “ball and chain” dimers

As the name suggests, it is a type of fullerene in which a carbon chain links two buckyballs.

• Fullerene rings

These are the rings of buckyballs that are linked together.

Applications of Fullerenes

• Fullerenes have great applications in the medical field. They are used as an antioxidant, anti-microbial agent, and photosynthesizers in photodynamic therapy. As fullerenes are cage-like structures, they are used for drug delivery.

• Fullerenes are used as a catalyst for the purification of water.

• Due to the spherical structure of fullerenes, they are used as a lubricant. They act as molecular ball bearings.

• Fullerenes are used as superconductors when they are mixed with alkali metals.

• They are used in electronics, microelectronic fields, and non-linear optical devices.

Conclusion

Fullerenes have emerged as an important molecule in the field of science and technology. A derivative of fullerenes has been synthesised that can dissolve in water. It can inhibit the activities of HIV. It could be used in medicine for treating AIDS. The tensile strength in every nanotube may prove useful in nanosurgery or microsurgery. It will greatly impact building construction, aircraft, and automobiles. Fullerenes are an important topic for research in the field of different industries and nanotechnology because of their practical properties.