Oxide nanoparticles preparation

Stengl V, Bakardjieva S, Marikova M, Bezdicka P, Subrt J (2003) Magnesium oxide nanoparticles prepared by ultrasound enhanced hydrolysis of Mg-alkoxides. Mater Lett 57 3998 1003... 

Catalytic activity of MCM-41 with rhodium oxide nanoparticles prepared by addition of RhClj 3H2O in sol-gel mixture were studied in the high-tempera-ture NO-CO catalytic reaction [22]. Catalyst containing RhO nanoparticles with diameters less than 3 run exhibited a novel promotional effect in the amount of N2 and N2O formation with excess O2, while most of Rh catalysts become poisoned with the O2 excess. The authors also claim that catalysts with 6-8 nm RhO nanoparticles in the MCM-41 had drastically retarded the formation of target molecules. Since the Rh precursor is added to the sol-gel mixture and particles can be located in the siHca body, the comparison of solely particle size in determination of catalytic properties can be misleading, as particle location (accessible for gases or not) may be a crucial feature. 

W.-N. Wang, Y. Itoh, I. W. Lenggoro, K. Okuyama Nickel and nickel oxide nanoparticles prepared from nickel nitrate hexahydrate by a low pressure spray pyrolysis, Mat. Sci. Eng. B. Ill (1), 69-76 (2004). 

Camtakan Z, Erenturk S, Yusan S (2012) Magnesium oxide nanoparticles Preparation, characterization, and uranium sorption properties. Environ Progr Sustain Energy 31 536-543... 

Fig. 16 Schematic of multifunctional iron oxide nanoparticles, prepared using a co-precipitation method, and subsequently reacted with functionalised dopamine derivatives. Reproduced with permission from ref. 63. Copyright 2013 Royal Society of...

Matsuno R, Otsuka H, Takahara A (2006) Polystyrene-grafted titanium oxide nanoparticles prepared through surface-initiated nitroxide-mediated radical polymerization and their application to polymer hybrid thin films. Soft Matter 2(5) 415... 

Fig. 2 Electron microscopy images of iron oxide nanoparticles prepared from high temperature precursor decomposition, with average sizes of (i) 7.4 nm, (b) 8.1 nmand (c) 45 nm." Changes in reaction conditions result in tailoring of particle size. 2011 American Chemical Society.

Fig. 18 (a) Scheme showing the role of acetic acid in the preparation of highly pure, surfactant free metal oxide nanoparticles, driven by a controlled oxidative dissolution process, (b) Aqueous dispersions of metal oxide nanoparticles prepared by this route. 2012 WILEY -VCH Verlag GmbH Co. KGaA, Weinheim. 

In contrast with the Schiff base salen, salicylaldehyde oxime (79) (salox) complexes of Co have received comparatively little attention, but a series of bis-bidentate divalent complexes of the form iraiis-Co(sa 1 ox)2( D M SO)2 have been reported.343 The heterocyclic bidentate oxime violurate (lH,3H-pyrimidine-2,4,5,6-tetrone 5-oximate, Hvi) (80) and its /V-methyl (mvi) and /V,/V -dimethyl (dmvi) derivatives form high-spin divalent [Co(vi)]+ and Co(vi)2 complexes, whereas [Co(vi)3] is low spin.344 The mixed-ligand Co(dmvi)2(phen) complex is also low spin. The crystal structure of m-Co(pxo)2Br2 (pxo = 2-acetylpyridine-l-oxide oxime) is isostructural with the Ni11 relative.345 The dichloro complex also adopts a cis configuration. The tridentate dioximes 2,6-diformyl-4-methylphenol dioxime and 2,6-diacetyl-4-methylphenol dioxime (Hdampo) form binuclear complexes of the type (81a) and (81b) respectively.346 Cobalt oxide nanoparticles were prepared by... 

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... 

Kopping JT, Patten TE (2008) Identification of acidic phosphorus-containing ligands involved in the surface chemistry of CdSe nanoparticles prepared in tri-n-octylphosphine oxide solvents. J Am Chem Soc 130 5689-5698... 

Ag/Si02 composites prepared by the one-step method and two-step methods were characterized by TGA/DTA, FTIR, XRD, and TEM. The results showed that Ag or silver oxide nanoparticles in 20 to30 nm were dispersed on the surface of the carrier Si02. The calcination temperature and prepared method affect the crystal phase of the functional component. 

Immobilizing DENs within a sol-gel matrix is another potential method for preparing new supported catalysts. PAMAM and PPI dendrimers can be added to sol-gel preparations of silicas " and zinc arsenates to template mesopores. In one early report, the dendrimer bound Cu + ions were added to sol-gel silica and calcined to yield supported copper oxide nanoparticles. Sol-gel chemistry can also be used to prepare titania supported Pd, Au, and Pd-Au nanoparticle catalysts. Aqueous solutions of Pd and Au DENs were added to titanium isopropoxide to coprecipitate the DENs with Ti02. Activation at 500°C resulted in particles approximately 4 nm in diameter. In this preparation, the PAMAM dendrimers served two roles, templating both nanoparticles and the pores of the titania support. 

Y. Koltypin, S. I. Nikitenko, and A. Gedanken, The sonochemical preparation of tungsten oxide nanoparticles, J. Mater. Chem. 12, 1107-1110 (2002). 

Various metal and metal oxide nanoparticles have been prepared on polymer (sacrificial) templates, with the polymers subsequently removed. Synthesis of nanoparticles inside mesoporus materials such as MCM-41 is an illustrative template synthesis route. In this method, ions adsorbed into the pores can subsequently be oxidized or reduced to nanoparticulate materials (oxides or metals). Such composite materials are particularly attractive as supported catalysts. A classical example of the technique is deposition of 10 nm particles of NiO inside the pore structure of MCM-41 by impregnating the mesoporus material with an aqueous solution of nickel citrate followed by calicination of the composite at 450°C in air [68]. Successful synthesis of nanosized perovskites (ABO3) and spinels (AB2O4), such as LaMnOs and CuMn204, of high surface area have been demonstrated using a porous silica template [69]. 

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