Metal-coated fullerenes

When building clusters by coating the fullerenes with metal, features similar to the electronic and geometric shells found in pure metal clusters[9] are observed in the mass spectra. In the case of fullerene molecules coated with alkaline earth metals (section 3), we find that a particularly stable structure is formed... 

In investigating the metal coating of C70, we will also replace Ba by Ca in the data presented. The coaling of the fullerenes with the latter material is basically identical but exhibits additional interesting features that will be discussed below. Figure 3 shows two mass spectra, the upper one of C oCa, the lower of CvoCa, both obtained under similar conditions as the spec-... 

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. 

Laser-induced photofragmentation of transition-metal-coated fullerenes CeoM and CvoM f (M = Ti, V) was also shown to yield MgC clusters as the most abundant product as soon as the laser intensity is sufficiently high to break the fullerene cage and remove the carbon surplus. ... 

In coating fullerenes with alkali metals, the stability of the cluster seemed to be determined primarily by the electronic configuration. The units C qM and C7oMg, where M is any alkali metal, proved to be exceptionally stable cluster building blocks. Coating a fullerene with more than 7 alkali metal atoms led to an even-odd alternation in the mass spectra, inter-... 

Because the forces of attraction prevail when molecules are brought into sufficiently dose proximity under normal conditions, release is best effected if both the strength of the interaction and the degree of contact are minimized. Aliphatic hydrocarbons and fluorocarbons achieve the former effect, finely divided solids the latter. Materials such as microcrystalline wax [64742 42-3] and hydrophobic silica [7631-86-9] combine both effects. Some authors refer to this combined effect as the ball bearing mechanism. A perfluoroalkylated fullerene nanosphere would perhaps be the ultimate example of this combined effect (17). These very general mechanistic remarks can be supplemented by publications on the mechanism of specific classes of release agents such as metallic stearates (18), fatty acids and fluorinated compounds (19), and silicone-coated rdease papers (20,21). The mechanism of release of certain problem adherents, eg, polyurethanes, has also been addressed (22,23). 

The electrochemical method is also used for the synthesis of fullerene derivatives, among them C6o fullerene salts with alkali metals crystallized at the cathode [11, 12]. No evidence on the electrochemical deposition of fullerenes on the electrodes from organic solvents is available although this method for producing fullerene coatings on metals is of indubitable practical interest. 

Carbon-based sorbents are relatively new materials for the analysis of noble metal samples of different origin [78-84]. The separation and enrichment of palladium from water, fly ash, and road dust samples on oxidized carbon nanotubes (preconcentration factor of 165) [83] palladium from road dust samples on dithiocarbamate-coated fullerene Cso (sorption efficiency of 99.2 %) [78], and rhodium on multiwalled carbon nanotubes modified with polyacrylonitrile (preconcentration factor of 120) [80] are examples of the application of various carbon-based sorbents for extraction of noble metals from environmental samples. Sorption of Au(III) and Pd(ll) on hybrid material of multiwalled carbon nanotubes grafted with polypropylene amine dendrimers prior to their determination in food and environmental samples has recently been described [84]. Recent application of ion-imprinted polymers using various chelate complexes for SPE of noble metals such as Pt [85] and Pd [86] from environmental samples can be mentioned. Hydrophobic noble metal complexes undergo separation by extraction under cloud point extraction systems, for example, extraction of Pt, Pd, and Au with N, A-dihexyl-A -benzylthiourea-Triton X-114 from sea water and dust samples [87]. 

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