Nested fullerenes

Hyperfullerenes consisting of smaller fullerenes nested within larger one have been found to form on heating soot and fullerenes to very high temperatures [4]. These... 

The discovery of perfect geodesic dome closed structures of carbon, such as C o has led to numerous studies of so-called Buckminster fullerene. Dislocations are important features of the structures of nested fullerenes also called onion skin, multilayered or Russian doll fullerenes. A recent theoretical study [118] shows that these defects serve to relieve large inherent strains in thick-walled nested fullerenes such that they can show faceted shapes. 

Let us note in addition that the layered sulfides M0S2 and WS2 have been found to form nanotubes and other fullerene-type structures, on account of their highly folded and distorted nature that favors the formation of rag and tubular structures. Such materials have been synthesized by a variety of methods [78] and exhibit morphologies, which were described as inorganic fiillerenes (IF), single sheets, folded sheets, nanocrystals, and nested IFs (also known as onion crystals or Russian dolls ). 

Figure 4. Schematic representation of the growth model of the inorganic fullerene-like of MoS2 (a) WS2 (b) nested polyhedra from oxide nanoparticles (31a).

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Nested fullerene-type structures with other inorganic layered materials have been investigated recently. Tenne et al (1992) have shown that MoSj is formed in a nested (onion-like) structure when MoOj is reduced by HjS in the gas phase at 1070-1220K (Feldman et al, 1995). Similar results have been obtained with WSj. The idea seems to be more general, being applicable to other inorganic layered structures, as... 

Nested (or onion-like) fullerenes built of several cages buried inside one another such as C60 C240 c540 C960 308, were found by using a Tunneling... 

In contrast, fullerenes after two years of effort are continuing to attract more practitioners to the field. Related areas of research are appearing such as giant and nested fullerenes as well as buckytubes. Such growth and branching is a sign of a developing discipline. 

Onion-like structures analogous to nested fullerenes were also obtained in considerable yields (Fig. 5). The heating arrangement with a tubular furnace employed for the preparation of MoS2 nanotubes is shown in Fig. 7. MoOj being sublimable, the Furnace ... 

Carbon nanotubes and nested fullerenes were also prepared by reductive carbonization of CO2 with magnesium metal. Motiei et al. [104] reported on the production of nanotubes in ca. 0% yield and nested fullerenes in ca. 12% yield at 1000°C by the reaction of dry ice and magnesium. The reductive carbonization of CO2 is reminiscent of the HiPco process [105, 106], based on disproportionation of carbon monoxide (the Boudouard reaction) ... 

Motiei, M. Hacohen, Y.R. Calderon-Moreno, J. Gedanken, A. Preparing carbon nanotubes and nested fullerenes from supercritical CO2. J. Am. Chem. Soc. 2001, 225, 8624-8625. 

An interesting property of the fullerenes is that, because they are completely hollow (i.e. all the atoms lie on the surface), fullerenes of different sizes can in principle be nested within each other like Russian dolls, in an arrangement sometimes referred to as a buckonion [672]. 

Apart from C o, also larger fullerenes like C70 may be employed in this reaction. The sole prerequisite is the use of nanotubes with a sufficient irmer diameter. Especially the intercalation of endofuUerenes has been studied extensively. The resultant products are doubly nested objects as a metal atom is contained inside each of the fullerene molecules incorporated in the tube (Figure 3.98). These substances may be considered M C SWNT (M = Gd, Dy, La, Sm). The endo-fuUerenes included are not necessarily isolated from each other. Upon heating to 1200 °C or irradiation of electrons, there is rather observed a coalescence of neighboring fullerenes and, to some extent, an oxidation of the metal atoms (Figure 3.98). In the latter process the nanotubes act as electron acceptor. Yet it is not only mononuclear endofuUerenes, but also dimetallofuUerenes that can be intercalated. Among others, these may be La2 Cgo, Gd2 C92 and Ti2 Qo. 

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