Fullerene-like

Regarding a historical perspective on carbon nanotubes, very small diameter (less than 10 nm) carbon filaments were observed in the 1970 s through synthesis of vapor grown carbon fibers prepared by the decomposition of benzene at 1100°C in the presence of Fe catalyst particles of 10 nm diameter [11, 12]. However, no detailed systematic studies of such very thin filaments were reported in these early years, and it was not until lijima s observation of carbon nanotubes by high resolution transmission electron microscopy (HRTEM) that the carbon nanotube field was seriously launched. A direct stimulus to the systematic study of carbon filaments of very small diameters came from the discovery of fullerenes by Kroto, Smalley, and coworkers [1], The realization that the terminations of the carbon nanotubes were fullerene-like caps or hemispheres explained why the smallest diameter carbon nanotube observed would be the same as the diameter of the Ceo molecule, though theoretical predictions suggest that nanotubes arc more stable than fullerenes of the same radius [13]. The lijima observation heralded the entry of many scientists into the field of carbon nanotubes, stimulated especially by the un-... 

Fullerene chemistry leading to novel fullerene-like molecules with new chemical groups that are radially attached has become a very active research field, largely because of the uniqueness of the Cgo molecule and the variety of chemical reactions that appear to be possible [30, 31]. Many new fullerene-based molecules have already been synthesized and characterized chemically,... 

Borafullerenes B2C58, B oCso, Bl2C48, BKP44, Bl8C42, B oClo, and fullerene-like B32, B42 clusters 98KK896. 

R. Tenne, Advances in the synthesis of inorganic nanotubes and fullerene-like nanoparticles. Angew. Chem. Int. Ed. 42 (2003) 5124. 

Chen, J. and F. Wu, Review of hydrogen storage in inorganic fullerene-like nanotubes. Appl. Phys. A, 78, 989-994, 2004. 

Inorganic Nanoclusters with Fullerene-Like Structure and Nanotubes... 

II. CLASSIFICATION OF DIFFERENT INORGANIC COMPOUNDS FORMING FULLERENE-LIKE STRUCTURES AND NANOTUBES... 

III. SYNTHESIS OF INORGANIC NANOTUBES AND FULLERENE-LIKE NANOPARTICLES... 

Figure 2. The TEM image of an edge of a multiwall fullerene-like particle (a) and nanotube (b) of MoS2, seven molecular layer thick (4). The distance between each two layers is 6.15 A. The c axis is always normal to the surface of the nanotube.

In contrast to carbon, which forms structures derived from both sp2 and sp3 bonds, silicon is unable to form sp2 related structures. Since one out of four sp3 bonds of a given atom is pointing out of the cage, the most stable fullerene-like structure in this case is a network of connected cages. This kind of network is realized in alkali metal doped silicon clathrate (19), which were identified to have a connected fullerene-like structure (20). In these compounds, Si polyhe-dra of 12 five-fold rings and 2 or 4 more six-fold rings share faces, and form a network of hollow cage structures, which can accommodate endohedral metal atoms. Recently, the clathrate compound (Na,Ba), has been synthesized and demonstrated a transition into a superconductor at 4 K (21). The electronic structure of these compounds is drastically different from that of sp3 Si solid (22). 

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

The Ba.C) N, nanotubes and fullerene-like structures have been synthesized by various laboratories in recent years. The most popular method is the plasma arc technique. The first report on the synthesis of BN nanotubes was by Zettl and coworkers (55). Since BN is an insulator, a composite anode was prepared from a tungsten rod with an empty bore in the center, which was stuffed with a pressed hexagonal BN powder. For the cathode, a water-cooled Cu rod was used. The collected gray soot contained limited amount of multi wall BN nanotubes. It is possible that in this case, the tungsten serves also as a catalyst. By perfecting this method, macroscopic amounts of double-wall BN nanotubes of a uniform diameter (2 nm)... 

Measurements of the optical properties in this range of wavelengths can probe the fundamental electronic transitions in these nanostructures. Some of the aforementioned effects have in fact been experimentally revealed in this series of experiments (90). As mentioned above, the IF nanoparticles in this study were prepared by a careful sulfidization of oxide nanoparticles. Briefly, the reaction starts on the surface of the oxide nanoparticle and proceeds inward, and hence the number of closed (fullerene-like) sulfide layers can be controlled quite accurately during the reaction. Also, the deeper the sulfide layer in the nanoparticle, the smaller is its radius and the larger is the strain in the nanostructure. Once available in sufficient quantities, the absorption spectra of thin films of the fullerene-like particles and nanotubes were measured at various temperatures (4-300 K). The excitonic nature of the absorption of the nanoparticles was established, which is a manifestation of the semiconducting nature of the material. Furthermore, a clear red shift in the ex-citon energy, which increased with the number of sulfide layers of the nanoparticles, was also observed (see Fig. 21). The temperature dependence of the exciton... 

Raman and resonance Raman (RR) measurements of fullerene-like particles of MoS2 recently have been carried out (93). By using 488-nm excitation from an Ar ion laser light source, the two strongest Raman features in the Raman spectrum of the crystalline particles, at 383 and 408 cm-1, which correspond to the E g and Aig modes, respectively (see Table I), were found to be dominant also in IF-MoS2... 

A comparable addition pattern with as many as five attached groups allowing further functionalization is represented in pentaaryl-fullerenes like 25-27 (Troshina et al., 2007 Zhong et al., 2006). Whereas the free acids are virtually insoluble in pure water, the use of basic water in the case of 25 (Zhong et al., 2006) and conversion of the polyacids 26 and 27 to the corresponding potassium salts leads to stable aqueous solutions with high fullerene concentrations. 

Danilov OB, Belousova IM, Mak AA, Belousov VP, Grenishin AS, Kiselev VM, Kris ko AV, Ponomarev AN, Sosnov EN (2003) Generation of singlet oxygen with the use of optically excited fullerenes and fullerene-like nanoparticles. Optics and Spectroscopy 95 833-842. 

As a third group of fullerene-like systems whose synthetic development is identified as a major future challenge are structurally defined single-walled carbon nanotubes (SWNTs) with uniform helicity and length, including their covalent and non-covalent derivatives. SWNTs can be considered as elongated giant fullerenes. 

Single spatial molecules fullerens, single-walled nanotubes, fullerene-like structures... 

The synthesis and structures of transition metal complexes of anionic cyclo-polypnictogen ligands, e.g. cyclo-P5, are discussed in Section 7.2.1 and 11.2. An exciting recent development involves the use of these complexes as building blocks for the construction of novel supramolecular assemblies, including one-dimensional (ID) and two-dimensional (2D) polymers and even soluble spherical fullerene-like aggregates.Complexes that have been used for this... 

The physical-chemical properties of a synthetic gallophosphate molecular sieve, the 30-A supercage cloverite , have been assessed [18]. Instead of attempting to list the burgeoning number of fullerene publications, attention is drawn to the formation and characterization of fullerene-like nanocrystals of tungsten disulfide [19,20]. Preparation, characterization and utilization of carbon nanotubes have been the subject of a number of reports from several laboratories [21-27]. 

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