Buckyballs are defined as “Compounds composed solely of an even number of carbon atoms, which form a cage-like fused-ring polycyclic system with twelve five-membered rings and the rest six-membered rings. The archetypal example is C60 fullerene, where the atoms and bonds delineate a truncated icosahedron. The term has been broadened to include any closed cage structure consisting entirely of three-coordinate carbon atoms.”
Buckminsterfullerene was discovered by Sir Harry Kroto of the University of Sussex and Richard Smalley and Bob Curl of Rice University in 1985 during a joint research project. Their discovery lead to a Nobel Prize in 1996.
The serendipitous discovery took place during experiments involving a cluster beam which uses a laser to vaporise a graphite rod in a helium atmosphere to produce carbon plasmas. The research was aimed at characterizing unidentified interstellar matter. Mass spectrometry evidence from these experiments indicated that carbon molecules with C60 atoms were forming, with a spheroidal geometry being most likely.
In 1989 work by Krätschmer, Fostiropoulos and Huffman later produced C60 by arcing carbon rods in an inert atmosphere. Production efficiencies were claimed to me much higher then those produced using the cluster beam. Their finding were confirmed by IR and UV measurements
The structure was named after the architect Richard Buckminster Fuller’s geodesic dome structure which bore a resemblance to the structure of the C60 Buckminsterfullerene structure. These same structures are also known as Buckyballs or fullerenes.
Buckminsterfullerene is the third allotrope of carbon along with graphite and diamond.
Since their discovery, Buckyballs have become such a hot topic of research that they have spawned their own branch of chemistry. So much so that the journal “Fullerene Science and Technology” dedicated to fullerenes was launched in 1993.
The basic C60 structure consists of 60 carbon atoms that link together to form a hollow cage-like structure. The structure consists of 32 faces of which 20 are hexagons and 12 are pentagons. Of these, no two pentagons share a vertex. A similar structure has been used to make soccer balls, in particular the Telstar supplied by Adidas and used in the 1970 and 1974 World Cups.
They are closely related to carbon nanotubes or buckytubes which have a cylindrical structure.
Other similar structures have since been discovered that have more then 60 carbon atoms. Some of the more popular ones include C70 and C76, although many contain as few as 28 and as many as 600 carbon atoms.
Although fullerenes have been found in seemingly simple things as candle soot, the most common technique for the production of fullerenes involves establishment of an electric arc between two carbon electrodes. Under these conditions, the energy from the arc is dissipated by breaking carbon from the surface. The carbon cools in the inert atmosphere and forms buckyballs. This technique however, is not scalable to be able to produce commercial quantities.
The first commercial production technique was the Kratschmer-Huffman arc discharge technique, from 1990 which used graphite electrodes. This technique primarily produces C60 and C70 but could be modified to produce larger fullerenes.
Shortly afterwards in 1991 a research group at MIT lead by Jack Howard in 1991 reported another technique based on a 1st generation combustion synthesis process.
The C60 molecule is extremely stable, being able to withstand high temperatures and pressures. The exposed surface of the structure is able react with other species while maintaining the spherical geometry.
The hollow structure is also able to entrap other smaller species such as helium, while at the same time not reacting with the fullerene molecule. In fact the interior of most buckyballs is so spacious, they can encase any element from the periodic table.
Buckyballs do not bond to one another. They do however, stick together via Van der Waals forces.
By doping fullerenes, they can be electrically insulating, conducting, semiconducting or even superconducting.
Some potential applications for fullerenes include:
• Catalysts due to their high reactivity
• Drug delivery systems, pharmaceuticals and targeted cancer therapies.
• Hydrogen storage as almost every carbon atom in C60 can absorb a hydrogen atom without disrupting the buckyball structure, making it more effective than metal hydrides. This could lead to applications in fuel cells.
• Optical devices
• Chemical sensors
• Polymer electronics such as Organic Field Effect Transistors (OFETS)
• Polymer additives
• Cosmetics, where they “mop up” free radicals.
• Diamonds, fullerenes have been used as precursors to produce diamond films