Onion fullerenes

Fig. 7 TEM micrograph of NbS2 nanoparticle with nested ( onion ) fullerene-like structure (courtesy of Dr. M. Homyonfer, Weizmann Institute). The layerto layer distance is 0.59 nm.

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. 

High-resolution transmission electron microscopy (HREM) is the technique best suited for the structural characterization of nanometer-sized graphitic particles. In-situ processing of fullerene-related structures may be performed, and it has been shown that carbonaceous materials transform themselves into quasi-spherical onion-like graphitic particles under the effect of intense electron irradiation[l 1],... 

In this paper, we analyze the methods of synthesizing multi-shell fullerene structures and try to gather some information about their formation mechanism. We also discuss some particularities of the energetics of onion-like graphitic particles. The understanding of the parameters involved would allow the development of efficient production procedures. 

The remarkable stability of onion-like particles[15] suggests that single-shell graphitic molecules (giant fullerenes) containing thousands of atoms are unstable and would collapse to form multi-layer particles in this way the system is stabilized by the energy gain from the van der Waals interaction between shells [15,26,27],... 

We hope that macroscopic samples of quasi-spherical onion-like particles will soon become available, and then we will be able to characterize these systems in detail. Probably a new generation of carbon materi-aks can be generated by the three-dimensional packing of quasi-spherical multi-shell fullerenes. 

The final section of the volume contains three complementary review articles on carbon nanoparticles. The first by Y. Saito reviews the state of knowledge about carbon cages encapsulating metal and carbide phases. The structure of onion-like graphite particles, the spherical analog of the cylindrical carbon nanotubes, is reviewed by D. Ugarte, the dominant researcher in this area. The volume concludes with a review of metal-coated fullerenes by T. P. Martin and co-workers, who pioneered studies on this topic. 

An alternative mode for dehydrobenzoannulene decomposition was recently reported by Vollhardt et al. [58]. Non-planar hybrid 81, prepared in low yield via cyclodimerization of known triyne 82 [Eq.(3)], reacted explosively at ca. 250°C to give a nearly pure carbon residue. Solvent extraction of the black powder failed to yield soluble materials such as fullerenes however, analysis of the residue by TEM showed formation of bucky onions and bucky tubes [59], in addition... 

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 ). 

CNTs can be chemically functionalized to achieve good dispersion in polymer/ CNT composites and strong interface adhesion (Gao et al., 2004). CNTs can be assembled as ropes or bundles, and there are some catalyst residuals, bucky onions, spheroidal fullerenes, amorphous carbon, polyhedron graphite nanoparticles, and other forms of impurities during the growth process of CNTs. 

M. Terrones, G. Terrones, H. Terrones, Structure, chirality, and formation of giant icosahedral fullerenes and spherical graphitic onions, Struct. Chem., vol. 13, pp. 373-384, 2002. 

Liu W, Meng QS (2009) An effective method of increasing production rate of onion-like fullerenes. J Phys Conf Ser 188 012035... 

Many nanomaterials can be made in different forms. We are familiar with the example of carbon, which we can find as diamond films, carbon black, fullerenes, and multi- and single-walled nanotubes. M0S2 can be made as nanotubes, onions (multi-walled fullerene-type structures), and thin films. 

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... 

The discovery of fullerenes in 1985 led to the era of nanomaterials.1 The three-dimensional geometry of these molecules as well as their unique properties distinguishes them from conventional molecules encountered in organic chemistry. Due to recent discoveries in this field, the horizons of this area have broadened to encompass various new molecules such as endohedral fullerenes, nanotubes, carbon nanohorns, and carbon nano-onions. This chapter discusses the electrochemical behavior of some of these carbon nanoparticles with special emphasis on endohedral fullerenes. Since a large number of fullerene derivatives have been prepared and their various electrochemical studies in different solvents and electrolytes have been reported, the electrochemistry of these derivatives is beyond the scope of this text.2 3 Among the other carbon nanoparticles, the electrochemistry of derivatives of carbon nanotubes has been reported. These studies have been highlighted in the final part of the chapter. 

The A-potential model multiwalled doped fullerene onions 19... 

For neutral doped fullerene onions A C6o C24o, A C6o C24o Cs4o, etc., the confining potential Vn of a multiwalled cage is replaced by a linear combination of corresponding single-walled potentials V [32]... 

---