Carbon 60

The discovery of Carbon 60, C60, is one of the most important discoveries in the 20th century. It was even more important that it lead its professors to winning a Nobel Prize later on. Carbon 60 was discovered unintentionally in a regular science experiment. The goal of the experiment was simulating conditions under which carbon nucleates in the atmosphere of a cool carbon-rich red giant star. The heart of the experiment was to explore the possibility that long carbon chain molecules, such as HCN, can form when carbon vapor nucleates in the presence of hydrogen and nitrogen.

During the experiment, Hary Kroto, Richard Smalley and Robert Carl later on, the researchers behind this experiment and later the founders of C60, discovered that a variety of carbon clusters were produced and that the distribution of cluster sizes depended on the experimental conditions. When the firing of the vaporization laser was delayed until most of the helium pulse had passed, a large even-numbered clusters with 38-120 carbon atoms resulted. The C60 peak was largest but not dominant. When the vaporization laser was fired of maximum helium density, the C60 peak grew 5 times stronger, besides C70. When these conditions were duplicated, the cluster distribution was completely dominated by C60. The carbon molecule that resulted from the experiment consisted of 60 carbon atoms, which has a mass of 60 times 12 grams that equals 720 grams. This important discovery was then published in 1985 in an article in “Nature” by the three researches mentioned above.

Now that C60 was discovered, scientists have found a way to produce it in macroscopic quantities. In 1990, Wolfgang Kratschmer and Donald Huffman, two famous scientists, discovered C60 in graphitic carbon “soot”, which is produced by evaporating graphite in an atmosphere of ~100 torr helium. It turned out that C60 and C70 were the smallest carbon clusters for which the production of them using macroscopic quantities method can be achieved.

To confirm this discovery and the structure of C60, scientists have used spectroscopic techniques, for example the mass spectrum. Originally, theorists had previously showed that C60 have four infrared active vibration modes, and positions of their peaks matched calculated line positions. The four-line IR Spectrum for C60 supported these results, also, the C60 NMR spectrum of the purified C60 showed the same thing. To sum this up, the C60 NMR spectrum showed that C60 existed and that the spectrum showed five peaks with C60 as the dominating one. These techniques have showed how the number 60 in the C60 molecule was important as the bonding structure of the molecule had a special shape. Each carbon atom in the molecule is three-connected to other atoms by one double bond and two single bonds. That kind of bonds has a hybridization of SP2. The bonds between atoms form a pattern of joined hexagons and pentagons that are similar to the panels of a soccer ball.

After the discovery and the confirmation of C60, the scientists behind this experiment could not find a name for this molecule. However, later on they decided to call it the “Buckminsterfullerene” molecule because the shape of it was reminiscent of the geodesic domes popularized by the architect Buckminster Fuller.

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