Properties and Applications
Fullerenes (singular: Fullerene) are ball-shaped molecules build from carbon atoms. The so-called Buckminsterfullerenes C60, or buckyballs, are the currently most adequately investigated molecules of that type. These fascinating molecules were named after Richard Buckminster Fuller (1895-1983), an architect who on the occasion of the Expo 1967 designed a dome structure of pentagonal and hexagonal cells (the so-called geodesic dome). The architecture of Fuller’s geodesic dome is very similar to that of the fullerene molecules.
The C60 molecule, for example, is 0,7nm in diameter and, just like a soccer ball, consists of 20 six-membered and 12 five-membered rings, which is why it is often referred to as “soccer ball molecule”. Comparing the dimensions of one such molecule with those of the Earth, one finds, so to speak, that the fullerene-soccer ball relation corresponds to the relation between a soccer ball and the Earth. Fullerenes, just like diamonds or graphite, are carbon modifications. Their very low density (1,68g/cm³) as compared to graphite (2,1-2,3g/cm³) or even diamond (3,51g/cm³) is due to their having the shape of a hollow ball. Fullerenes, as against graphite, are not electrically conductive.
C60 forms yellow crystals but turns to a deep wine red when dissolved in organic solvents (for example toluene). Fullerenes, thus, are the only allotropic carbon modifications that are soluble in organic solvents. The fullerene cage is destroyed by UV radiation, particularly in the presence of O2. The C60 fullerenes are the smallest ones within the large number of allotropic fullerenes. The next larger fullerene (C70), for example, has the structure of a rugby ball. Other Cn molecules (n = 74, 76, 78, 80, 84, 90, 94) have been isolated, and C240 and C540 are assumed to exist in addition.
Fullerenes are currently applied in cosmetics and sports goods industries. Since C60 molecules have a high electron affinity (radical scavengers) due to which they are supposed to absorb many free radicals (reactive molecular species) that are responsible for aging of the skin, they are used, for example, in anti-aging creams. The sports goods industry makes use of fullerenes mainly in golf clubs, badminton and tennis rackets. The C60 molecules are integrated into shafts and frames to obtain very thin-walled, lightweight robust carbon structures.
Since fullerenes are non-biodegradable molecules whose toxicity has not been studied very well so far, companies such as CIBA (since 1st April 2009 part of BASF SE) and Novartis presently refrain from applying them.
Fullerenes are not self-inflammable. As a mixture with air (dust) fullerenes are flammable under the influence of an ignition source (dust explosion). The behaviour in a dust explosion is similar to that of other, carbon-based materials.
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Natural Occurrence and Production
Fullerenes occur naturally in different stones.It is assumed that they have been synthesized by man accidentally in early times and were deposited as soot on the walls of caves . The possibility of the existence of fullerenes was predicted in 1970 by Japanese chemist Eiji Osawa on the basis of calculations [7,8]. Davidson and Haymet confirmed in 1981 and 1985, the calculations of Osawa. In 1985 Curl, Kroto and Smalley produced for the first time a fullerene, namely C60, in very small quantities via vaporizing graphite in the laser beam , and were awarded the Nobel Prize in Chemistry in 1996 . In 1990, Buckminsterfullerenes were synthesized in a larger scale for the first time by Kraetschmer and Huffmann . Fullerenes are made by vaporizing graphite in the arc or with an electric current in a low-pressure helium or argon atmosphere.
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