Kratschmer-Huffman method

The prototype of all fullerenes is Buckminsterfullerene ,. Since it is the most abundant fiillerene obtained from macroscopic preparation procedures such as the classical Kratschmer-Huffman method, its chemical and physical properties were developed in very quick sucession soon after it became available in 1990. The icosahedral football shaped Buckminsterfrdlerene 60 is now the most intensively studied molecule of all. Many principles of the chemistry of C , are known. These allowone to tailor design new fuUerene derivates with specific properties useful for biological applications or as new materials. The main types of fullerene derivative are exohedral addition products, endohedral fullerenes, heterofullerenes and cluster opened systems. Whereas many examples of the first two groups are already known, sophisticated methods for the synthesis of the latter two groups have started to emerge only recently. 

The quantities produced with the laser vaporization method were however not even sufficient for doing experiments to verify the proposed structure. This was solved by Kratschmer, Huffman and their students who had as early as in 1982, [144-146] i.e. three years before the discovery of Ceo in 1985, produced Ceo without knowing it. They used an electric arc in a helium atmosphere of 150 torr and produced a special kind of soot with a unique type of optical absorption known as the camel hump smoke in the UV region. Their recorded spectrum fitted however very nicely to some predictions of the present author [147]. After a number of trials, they found in 1990 [148] that the special carbon soot could be dissolved in benzene, which provided the possibility to separate Ceo from the carbon particles [149], record a UV visible spectrum and even fabricate crystals of Ceo and C70 and determine the crystal structure. Suddenly a new kind of carbon material had been found in addition to the commonly known diamond and graphite. 

Returning to La Cn Alvarez et al. showed that the Kratschmer-Huffman contact arc method, with rare-earth oxides mixed with graphite, also produced significant amounts of endohedral complexes. A191] They focused their attention on La2 Cn, and found a phenomenon similar to what was seen in La C while the raw soot contains en-dohedrals with a broad spectrum of n, the toluene extract contains only La2 C8o and La C82- That result was also confirmed by Ross et al., who... 

Since the discovery by Kratschmer and Huffman last year of a simple method for producing macroscopic quantities of Cjo, C70, and some of the higher empty fullerenes, we have searched for a means of extending this technique to fill the void and make macroscopic quantities of internally substituted fullerenes— endohedral fullerene complexes. We report below our first success in this search. It involves a simple revision to the laser-vaporization method originally used in 1985 just do it in an oven at 1200 C. 

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