Metastable TiO(2) polymorphs are more promising materials than rutile for specific applications such as photocatalysis or catalysis support. This was clearly demonstrated for the anatase phase but still under consideration for brookite, which is difficult to obtain as pure phase. Moreover, the surface doping of anatase with lanthanum ions is known to both increase the thermal stability of the metastable phase and improve its photocatalytic activity.
View Article and Find Full Text PDFPolyols were successfully used as size and shape controllers of oxide nanoparticles synthesized by soft chemistry in aqueous solution. The efficiency of acyclic polyols as a complexing agent depends obviously on the number of OH groups bonded to the carbon chain (and thus on the carbon chain length), but also on their stereochemistry. This innovating way to control morphology has been experienced for the synthesis of boehmite nanoparticles, whose morphology variations related to xylitol adsorption (C5 alditol) have been previously reported.
View Article and Find Full Text PDFRecent concepts for nuclear fuel and targets for transmuting long-lived radionuclides (minor actinides) and for the development of innovative Gen-IV nuclear fuel cycles imply fabricating host phases for actinide or mixed actinide compounds. Cubic stabilized zirconia (Zr, Y, Am)O(2-x) is one of the mixed phases tested in transmutation experiments. Wet chemical routes as an alternative to the powder metallurgy are being investigated to obtain the required phases while minimizing the handling of contaminating radioactive powder.
View Article and Find Full Text PDFThe ability to design nanoparticles size and shape through the addition of simple and commercially available organic molecules is of particular interest in the catalytic domain because huge amounts of very fine powders are needed. The origin of this effect is all the more difficult to elucidate because the involved interactions are weak. In this paper, we have investigated the shaping of boehmite AlO(OH) nanoparticles in the presence of polyols like xylitol (C(5) alditol) by a combined experimental and theoretical approach.
View Article and Find Full Text PDFThe regulation of engineered nanoparticles requires a widely agreed definition of such particles. Nanoparticles are routinely defined as particles with sizes between about 1 and 100 nm that show properties that are not found in bulk samples of the same material. Here we argue that evidence for novel size-dependent properties alone, rather than particle size, should be the primary criterion in any definition of nanoparticles when making decisions about their regulation for environmental, health and safety reasons.
View Article and Find Full Text PDFA microporous manganese oxide nanocomposite is synthesized using heteroepitaxy in an aqueous medium at 95 degrees C.
View Article and Find Full Text PDFWhen normalized per unit of surface area, the quantity of arsenic adsorbed at the maghemite surface remains constant for particles between 300 and 20 nm. However, nanoparticles smaller than 20 nm exhibit enhanced adsorption capacity. The origin of this observed size-dependence for adsorption or "nano effect" is unclear.
View Article and Find Full Text PDFFluorescence is increasingly used for in vivo imaging and has provided remarkable results. Yet this technique presents several limitations, especially due to tissue autofluorescence under external illumination and weak tissue penetration of low wavelength excitation light. We have developed an alternative optical imaging technique by using persistent luminescent nanoparticles suitable for small animal imaging.
View Article and Find Full Text PDFTiO2 rutile nanorods of average length L = 160 +/- 40 nm and average diameter D = 15 +/- 5 nm have been synthesized through a seed-mediated growth process by TiCl4 hydrolysis in concentrated acidic solution. These nanorods were dispersed in water to yield stable (aggregation-free) colloidal aqueous suspensions. At volume fractions phi > 3%, the suspensions spontaneously display a phase separation into an isotropic liquid phase and a liquid-crystalline phase identified as nematic by X-ray scattering.
View Article and Find Full Text PDFChem Commun (Camb)
March 2004
This overview features the chemical background on condensation phenomena of iron cations in aqueous solution. The formation of molecular clusters or nanosized solid phases is interpreted with illustrative mechanisms building a bridge between solution chemistry and solid state chemistry. Iron chemistry gives a very nice example of chemical versatility.
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