Fullerene

A fullerene molecule is made entirely of carbon atoms arranged in a hollow shape, like a sphere, ellipsoid, or tube. The most common fullerene is C60, which looks like a soccer ball. Discovered in 1985, fullerenes are known for their properties, such as high electrical and thermal conductivity, strength, and chemical reactivity, making them useful in electronics and other fields.

1.0What is Fullerene?

Fullerenes are carbon allotropes with molecules formed by carbon atoms connected by single and double bonds, creating a cage-like structure of fused rings. These molecules can be hollow spheres, ellipsoids, tubes, or various other shapes and sizes. When arranged cylindrically, they form carbon nanotubes.

2.0Discovery and Structure of Fullerene

Fullerenes were discovered in 1985 by scientists Harold Kroto, Richard Smalley, and Robert Curl, who later received the Nobel Prize in 1996 for this discovery.

Fullerenes are a class of carbon allotropes characterized by their unique molecular structures, which madeup of carbon atoms connected by single and double bonds, forming a closed or partially closed cage-like structure. Here is a detailed look at their structure:

Basic Structure

1. Carbon Atoms Arrangement:

• Fullerenes are made entirely of carbon atoms.
• The carbon atoms are arranged in a pattern of hexagons and pentagons, similar to the structure of a soccer ball (for spherical fullerenes).

2. Bonding:

• Each carbon atom is sp² hybridized, forming three sigma bonds with neighboring carbon atoms.
• The remaining p-orbital on each carbon atom overlaps to form pi bonds, contributing to the molecule's stability and electron delocalization.

3.0Types of Fullrenes

Spherical Fullerenes (Buckminsterfullerenes):

The most well-known fullerene is C₆₀, consist 60 carbon atoms arranged in the shape of a truncated icosahedron. (20 hexagons and 12 pentagons).

Other spherical fullerenes include C₇₀, C₇₆, and higher fullerenes, with similar structures but different numbers of carbon atoms.

• C₆₀​ is the most well-known spherical fullerene. It consist of 12 pentagons and 20 hexagons, forming a truncated icosahedron.

Ellipsoidal Fullerenes: 

• These include C₇₀, which has a more elongated shape.
• Their structure is similar to spherical fullerenes but stretched along one axis.

Carbon Nanotubes: 

Cylindrical fullerenes, also known as buckytubes, with unique mechanical and electrical properties.

This type of fullerene consists of cylindrical or hollow tubes with very small dimensions, typically a few nanometers wide but ranging from micrometers to several millimeters in length.

Carbon nanotubes can be either closed or open-ended.

Unique molecular structure imparts several distinctive macroscopic properties:

• High tensile strength
• High electrical conductivity
• High ductility
• High heat conductivity
• Relative chemical inactivity

Megatubes are another form of fullerene:

• Larger diameter than nanotubes
• Typically exhibit walls of varying thickness

4.0Comparison of Fullerenes and Carbon Nanotubes

5.0Properties of Fullerene

Important Properties of fullerene are -

• Electrical Conductivity: 

Fullerenes can act as semiconductors or conductors, depending on their structure and the presence of other elements.

• Thermal Conductivity: 

High thermal conductivity is a result of the strong carbon-carbon bonds.

• Strength and Hardness: 

Carbon nanotubes, a form of fullerene, are among the strongest and stiffest materials known.

• Chemical Reactivity: 

Fullerenes can participate in various chemical reactions, including addition reactions and redox reactions.

6.0Applications of Fullerene

Electronics: Used in organic photovoltaics (solar cells), organic light-emitting diodes (OLEDs), and transistors due to their electronic properties.

Medicine: Potential applications in drug delivery systems, cancer therapy, and as antioxidants.

Materials Science: Reinforcing agents in composite materials, producing ultra-strong and lightweight materials.

Energy Storage: Used in the development of supercapacitors and batteries.

Catalysis: Serving as catalysts in various chemical reactions due to their unique structure and reactivity.

Medical Field:

• Used as light-activated antimicrobial agents.
• Utilized in designing high-performance MRI contrast agents and X-ray imaging contrast agents.
• Applied in photodynamic therapy and drug and gene delivery.

Drug Delivery Systems: Buckminsterfullerene is employed in drug delivery systems, lubricants, and as a catalyst.

Conductivity: Used as conductors.

Absorbents: Certain types of fullerenes can absorb gases.

Cosmetics: Incorporated in cosmetic products.

Photovoltaic Applications: C₆₀-based films are used in photovoltaic applications.