Metal inorganic oxide surface-mediated

Syntheses of medium- and high-nuclearity ruthenium and osmium clusters continue to be largely by thermolyses of lower nuclearity precursors, but surface-mediated methods have also been employed the use of inorganic oxides or zeolites in the preparation of metal carbonyl clusters, including pentaosmium and hexaruthenium carbido clusters, and the decaosmium complexes [H50sio(CO)24] and [Osio(/t6-C)(CO)24], has been reviewed. 

Inorganic substances Uke small metal clusters, metal oxides etc. may also be deposited on the surface of single or bundled carbon nanotubes. It is possible, for instance, to decorate multiwalled nanotubes with nanoparticulate oxides of zinc or magnesium. To this end, a surfactant-mediated dispersion of MWNT is solubilized in cyclohexane with Triton X-114 as a surface-active agent to obtain a water/ oil emulsion. Aqueous solutions of the respective metal acetates are added afterward and are then found in the aqueous portion of the emulsion. Subsequently increasing the pH value to about 9.5 causes a precipitation of the metal hydroxides that deposit on the nanotube surface in the shape of hollow spheres. Final calcination at 450 °C transforms these hollow particles into the crystalhne metal oxides. Particles measuring about 5 nm or 30-40 nm have been observed for ZnO or MgO, respectively (Figure 3.84b). 

The ability of mineral oxide particles to generate oxidants by the Fenton reaction has been established in vitro (15), thus supporting a role for complexed iron in oxidant generation by these dusts. Participation of this metal in free radical production and lipid peroxidation mediated by mineral oxides has also been demonstrated (16-20). Complexion of iron from both inorganic sources in the earth s crust and body sources onto the surface of these dusts with the resulting oxidant generation may be an essential aspect in their toxicity. 

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