Nanoparticles metal oxide nanocrystals

Alivisatos and collaborators [257] demonstrated that transition metal oxide nanocrystals (7-Fc203, Mn304, CU2O) could be prepared using a nonhydrolytic process based on the thermal decomposition of metal Cupferron complexes M Cup (M = metal ion. Cup = CeHsNjNOjO ) in a hot solvent with surfactant. Their results suggest that a good level of control can be achieved when this approach is used to process metal oxide nanoparticles. 

It has been reported that single or mixed metal oxide nanoparticles, such as zinc oxide, copper oxide, aluminum oxide, or titanium oxide, incorporated into a filtration medium containing a binder matrix, can destroy bacteria (57). The metal oxide nanocrystals are included in amounts ranging from approximately 0.1 % up to about 10% by weight, based on the entire filtration medium. In a series of studies, it has been shown... 

Zhu et al. [109] proposed an environmentally innocuous method of preparation by using a single-step solvothermal route in ethanol solutions. The procedure leads to simultaneous rGO reduction and iron or cobalt oxide precipitation due to the fact that the GO/rGO layers act as heterogeneous nucleation seeds during the precipitation of the metal oxide nanocrystals. In a related approach, Han et al. [110] were able to obtain Li4Ti50i2 particles anchored to rGO by solvothermal treatment of H2O/ EtOH-based suspensions of graphite oxide and the oxide powder. The process involves reduction of GO and attachment of the mixed oxide nanoparticles within a single step. 

The inverse-micelle approach may also offer a generalized scheme for the preparation of monodisperse metal-oxide nanoparticles. The reported materials are ferroelectric oxides and, thus, stray from our emphasis on optically active semiconductor NQDs. Nevertheless, the method demonstrates an intriguing and useful approach the combination of sol-gel techniques with inverse-micelle nanoparticle synthesis (with OTO erafe-temperature nucleation and growth). Monodisperse barium titanate, BaTiOs, nanocrystals, with diameters controlled in the range from 6-12nm, were prepared. In addition, proof-of-principle preparations were successfully conducted for Ti02 and PbTiOs. Single-source alkoxide precmsors are used to ensure proper stoichiometry in the preparation of complex oxides (e.g. bimetallic oxides) and are commercially available for a variety of systems. The... 

With the advent of synthetic methods to produce more advanced model systems (cluster- or nanoparticle-based systems either in the gas phase or on planar surfaces), we come to the modern age of surface chemistry and heterogeneous catalysis. Castleman and coworkers demonstrate the large influence that charge, size, and composition of metal oxide clusters generated in the gas phase can have on the mechanism of a catalytic reaction. Rupprechter (Chap. 15) reports on the stmctural and catalytic properties of planar noble metal nanocrystals on thin oxide support films in vacuum and under high-pressure conditions. The theme of model systems of nanoparticles supported on planar metal oxide substrates is continued with a chapter on the formation of planar catalyst based on size-selected cluster deposition methods. In a second contribution from Rupprecther (Chap. 17), the complexities of surface chemistry and heterogeneous catalysis on metal oxide films and nanostructures, where the extension of the bulk structure to the surface often does not occur and the surface chemistry is often dominated by surface defects, are discussed. 

Preformed metal oxide nanoparticles have also been used in the formation of inverse colloidal crystals [24-26]. Slurries of titania nanocrystals and the PS spheres are dropped onto a glass substrate and dried slowly (over 24 h) [24]. After pressing (cold isostatic press) the film is slowly heated to 520 °C to remove the PS and produce a titania matrix of >10 pmxlO mmx2-3 mm with ordered... 

C02-expanded ethanol, porous hollow metal oxide nanoparticles have been prepared using a carbon template by Sun and co-workers.A metal salt, such as C0 j(NO3)3,(CO3)z(OH) , wHaO, can be prepared from the corresponding metal nitrate in COa-expanded ethanol and deposited on the surface of template carbon colloids. Thermal treatment in nitrogen affords CoO nanocrystals. When calcined in air, these can be transformed to C03O4. Electron microscopy images of these dense hollow porous nanostructures are shown in Fig. 9. The improved performance of this material as an anode in Li-02 battery has also been demonstrated, along with the capacity to generate FeO NiO and MnO, nanocomposites. 

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