Fullerenes and Carbon Nanotubes

Soots containing abundant fullerenes can be made by striking an electric arc between two graphite electrodes or by controlled combustion of hydro- 

Fullerenes are rather easily oxidized, which explains the fact that, despite their commonplace occurrence in soots, they had escaped detection for so long. Fullerenes have now been found in Precambrian carbonaceous rocks from Karelia, Russia in breccias associated with the 1.85-billion-year-old Sudbury impact structure in Canada and in a sooty layer (believed to be due to fires from the asteroid impact that is thought to have killed off the dinosaurs) marking the Cretaceous-Tertiary boundary in New Zealand.  

Fullerenes can be derivatized by various means. For example, reaction with fluorine gas proceeds stepwise to the formation of colorless CeoFeo, which, according to the F nuclear magnetic resonance (NMR) spectrum, contains just one type of F site and so evidently retains a high degree of symmetry. In view of the low adhesion typical of fluorocarbons, this spherical molecule is expected to have extraordinary lubricant properties. Curiously, bromination of Ceo is reversible on heating otherwise, the reactions of fullerenes resemble those of alkenes or arenes (aromatic hydrocarbons). 

At present, the technological future of fullerenes is unclear, although uses in batteries, as drug delivery vehicles, in polymeric materials, and 

In 1996, the Nobel Prize for chemistry was awarded to R. F. Curl, H. W. Kroto, and R. E. Smalley, in recognition of their discovery of the fullerenes. 

Fullerene chemistry. A. The structures of C j, C70, and corannulene are shown. B. Representative reactions of fullerenes. Shown are prototypical carbene and Diels-Alder reactions. Also shown is a trifunctional reagent used to regioselectively provide a multifunctional fullerene. 

There are two types of bonds in Cao, the 6-6 bonds, which lie at the junctions between two six-membered rings, and the 6-5 bonds, which lie at the junctions of six- and five-membered rings. Considerable alternation in bond lengths is seen, with the 6-6 bonds being —1.38 A and the 6-5 bonds being —1.45 A. Based on these observations, and the reactivity patterns discussed below, the 6-6 bonds are considered to have much more double bond character than the 6-5. 

Radical additions also occur, but they are typically more difficult to control and generally lead to multiple adducts. 

which first undergoes a carbene addition. Heating the adduct promotes a double Diels-Alder reaction, and the constraints provided by the tethers direct the reactions such that a 60% )field of the single adduct shown can be obtained. Many variants of this strategy have been developed. 

A good deal of the excitement surrounding the discovery of the fullerenes was their perceived potential as novel materials for a number of applications. Early speculations suggested that the essentially spherical structure of Cm might be the basis of novel lubricants, providing molecular ball bearings . However, the first hint of special properties came in 1991 when a group at Bell Labs reported superconductivity at 18 K in a sample of Cm that 

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Metal-carbide clusters are relevant to the fonnation of both endohedral fullerenes and carbon nanotubes [1351. There also exists a class of apparently stable metal-carbide cluster ions, = Ti, V, Cr, Zr and Hf), called... 

There are many applications for diamonds and related materials, e.g., diamondlike carbon films, and there are potential applications for Fullerenes and carbon nanotubes that have not yet been realised. However, the great majority of engineering carbons, including most of those described in this book, have graphitic microstructures or disordered graphitic microstructures. Also, most engineering carbon materials are derived firom organic precursors by heat-treatment in inert atmospheres (carbonisation). A selection of technically-... 

Drcssclhaus, M.S., Dresselhaus, G. and Eklund, P.C., Science of Fullerenes and Carbon Nanotubes, 1996, Academic Press, San Diego. 

As further research on fullerenes and carbon nanotubes materials is carried out, it is expected, because of the extreme properties exhibited by these carbon-based materials, that other interesting physics and chemistry will be discovered, and that promising applications will be found for fullerenes, carbon nanotubes and related materials. 

Dresselhaus, M. S., Dresselhaus, G. and Ekiund, P. C., Science of Fullerenes and Carbon Nanotubes, Academic Press, New York, NY, 1996. Salto, R., Dresselhaus, M. S. and Dresselhaus, G., Physical Properties of Carbon Nanotubes, Imperial College Press, London, 1998. 

Mueler et al. and Gottschalk et al. [43, 44] presented a model for predicting concentrations of nanoparticles including nano-Ag, nano-Ti02, nano-ZnO, fullerenes, and carbon nanotubes (CNT) in different environmental compartments. The results of this study demonstrated that modeling is a meaningful utility to carry out quantitative risk assessment of nanoparticles. 

If you stick to the definition of an allotrope being a modification of an element characterized by its x-ray crystal structure. Otherwise carbon may have more modifications, when counting all the different fullerenes and carbon nanotubes as allotropes. 

F. Cataldo, T. Da Ros (eds.) Medicinal Chemistry and Pharmacological Potential of Fullerenes and Carbon Nanotubes,... 

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