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The Discovery of Buckyballs
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The 1996 Nobel Prize in Chemistry was awarded to Professors Robert F. Curl, Jr., and Richard E. Smalley, Rice University, Houston, USA, and Professor Sir Harold W. Kroto, University of Sussex, Brighton, U.K. for their discovery of fullerenes in 1985. Kroto worked at the National Research Council (NRC) in Ottawa as a post-doctoral fellow under the supervision of Gerhard Herzberg form 1964-1966. Kroto also collaborated with NRC researchers between 1975 and 1979 to study carbon molecules in space.
Fullerenes are a family of highly symmetrical carbon-cage molecules. The most abundant and well known member of this family is a carbon-cage molecule made up of 60 carbon atoms, C60. C60 was given the name of buckminsterfullerene in honour of architect R. Buckminster Fuller who was a pioneer in the studies of polygonal structures and the inventor of the geodesic dome. Buckminsterfullerene is usually shortened to the catchier name of buckyball.
In 1985 Kroto went to Rice University to use Smalley’s equipment to study the formation of long-chain carbon/nitrogen molecules, cyanopolyynes. Kroto hoped that by using Smalley’s equipment to study the cluster formation of carbon he might be able to gain some insight into how the cyanopolyynes were formed in stellar atmospheres. The experiments were performed with the help of Curl and graduate students J.R. Heath and S.C. O’Brien. The experiment involved vapourizing carbon by directing an intense pulse of laser light at a carbon surface and then condensing the carbon atoms in an atmosphere of inert helium gas. As carbon atoms condensed they combined to form clusters. These carbon clusters were then analysed by a mass spectrometer. The result was the discovery of molecules consisting of large numbers of carbon atoms. It was found that with fine tuning they were able to produce clusters with 60 and 70 carbon atoms with the C60 clusters being the most abundant.
Prior to the discovery of the fullerenes, there were six crystalline forms of the element carbon known. These are two kinds of graphite, two kinds of diamond, chaoit, and carbon(VI). The fullerenes are now the seventh crystalline form of carbon known. The structure of the buckyballs is a spherical polyhedron in which there are 32 faces with 20 hexagonal (6-angled) and 12 pentagonal (5-angled) surfaces. The resulting structure resembles a soccer ball.
The buckyball is of great theoretical significance because it is a highly symmetrical, aromatic, highly stable three dimensional system in which single and double bonds alternate. Curl, Kroto, and Smalley experimented further with C60 by trying to react it with other compounds such as hydrogen, carbon monoxide, and oxygen only to find that the C60 remained unchanged. In fact, all carbon clusters with an even number of carbon atoms from 40-80 reacted just as slowly and suggested that they also had closed structures. The next experiments performed explored the possibility of the buckyball being able to engulf other atoms as it has a hollow interior. Therefore, experiments were attempted to see if a metal atom could be enclosed in it. A graphite sheet was soaked with a solution of lanthanum chloride (LaCl3) and subjected to the vapourisation-condensation experiment. The result was the formation of C60La+: the lanthanum ion was trapped inside the cage!
The discovery that buckyballs and all carbon clusters with an even number of carbon atoms had closed structures led to the possibility that the element carbon could assume an almost infinite number of different structures. These closed structures were named the fullerenes. Following the discovery of fullerenes in 1985 other scientists began to study C60. As a result, the fullerenes now represent well-defined chemical compounds. New chemistry has developed to manipulate and study these new compounds. It is even possible to produce superconducting salts of C60, new three-dimensional polymers, and new catalysts. Scientists are just beginning to explore the vast world of fullerene chemistry.
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