Carbon 60 (C60) is a molecular compound composed solely of 60 carbon atoms, representing a distinct form, or allotrope, of the element carbon. This molecule is a member of the fullerene family, a class of closed-cage carbon structures named after architect Buckminster Fuller. The molecule is widely known by its common nickname, “Buckyball,” due to its spherical appearance. Its discovery in 1985 by scientists Harold Kroto, Richard Smalley, and Robert Curl, who were later awarded the 1996 Nobel Prize in Chemistry, introduced a third major class of carbon materials alongside diamond and graphite.
The Unique Molecular Architecture
C60’s structure is defined by the arrangement of its 60 carbon atoms into a truncated icosahedron, the exact geometry of a standard soccer ball. This architectural marvel is constructed from a mesh of 12 pentagonal faces and 20 hexagonal faces.
Each carbon atom within the structure is bonded to three neighboring carbon atoms, creating a network of single and double bonds. The presence of the pentagonal rings is the reason for the curvature, as introducing a five-membered ring into an otherwise flat sheet of six-membered rings forces the surface to dome. This combination results in a highly symmetrical structure, contributing to the molecule’s stability.
The diameter of the C60 molecule measures approximately 0.7 nanometers. This nanoscale dimension makes C60 a foundational element in nanotechnology and materials science. The hollow cage structure allows for the encapsulation of other atoms or small molecules inside, leading to a class of compounds called endohedral fullerenes.
Key Physical and Chemical Characteristics
Its remarkable stability allows the molecule to remain intact even under high temperatures and extreme pressures. This inherent strength is a consequence of the robust, closed-shell arrangement of its carbon framework.
A defining chemical feature is its high electron affinity, meaning C60 readily accepts electrons. This property classifies the molecule as an electron acceptor, making it highly effective at facilitating charge transfer.
C60 is hydrophobic and virtually insoluble in water or other polar solvents. However, it exhibits significant solubility in various organic solvents, especially aromatic ones like toluene and xylene. Solutions of pure C60 in these solvents display a distinctive deep purple color. This solubility profile is leveraged in the purification and processing of C60.
Synthesis and Natural Occurrence
While C60 is most often associated with laboratory synthesis, it does occur naturally, albeit in very small quantities and often in impure forms. Trace amounts of C60 have been detected in geological formations, the soot created by burning common organic materials, and even in the vastness of interstellar space and the remnants of dying stars.
Because the naturally occurring amounts are too small and impure for commercial or research applications, C60 is primarily produced artificially. The most widespread method for synthesis is the arc-discharge method. This process involves creating an electric arc between two graphite electrodes in an inert helium atmosphere, which vaporizes the carbon and causes the C60 molecules to form in the resulting soot.
Another technique used for production is laser ablation, which involves intensely firing a laser at a graphite target to vaporize the carbon. After either method, the fullerenes are extracted from the resulting carbon soot using organic solvents and then purified through chromatography to separate the C60 from other fullerenes. This process is necessary to obtain the high-purity C60 required for advanced technological use.
Current Applications Across Fields
C60’s unique properties have led to its application across several distinct fields, starting with materials science. Its exceptional mechanical properties allow for its use in creating high-performance composite materials and advanced coatings. The spherical shape and stability also make C60 an effective additive in lubricants, where it helps to improve anti-wear and anti-friction characteristics in mechanical systems.
In the field of electronics, C60 is highly valued for its electron-accepting nature, which makes it a good n-type semiconductor. This capability is instrumental in the development of organic photovoltaic (OPV) solar cells, where C60 derivatives are used to efficiently separate and transport electrons generated from absorbed sunlight. It is also being incorporated into components for organic transistors and other flexible electronic devices.
Within biological and health contexts, the molecule is used in various research applications, particularly in its role as a potent radical scavenger. C60 exhibits strong antioxidant properties, meaning it can neutralize free radicals that cause oxidative stress in biological systems. This characteristic is the basis for its inclusion in some dietary supplements and its use in preliminary research exploring treatments for conditions involving oxidative damage.