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1.
Phys Chem Chem Phys ; 21(10): 5455-5465, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30801105

RESUMO

Repeated attacks using organophosphorus compounds, in military conflicts or terrorist acts, necessitate developing inexpensive and readily available decontamination systems. Nanosized cerium oxide is a suitable candidate, acting as a heterogeneous catalyst for the degradation of organophosphorus compounds such as VX agent or sarin. However, the reaction mechanism of the phosphatase mimetic activity of CeO2 nanoparticles is not fully described. Adsorption, surface-promoted hydrolysis, and desorption cycles strongly depend on the physico-chemical characteristics of the facets. In this study, CeO2 nanoparticles with different shapes were elaborated by hydrothermal synthesis. Nano-octahedra, nanocubes, or nanorods were selectively obtained under different conditions (temperature, concentration and nature of the precursors). The degradation activity according to the crystal faces was evaluated in vitro by measuring the degradation kinetics of paraoxon organophosphate in the presence of CeO2 nanoparticles. The results show an influence of both specific surface area and crystal faces of the nanoparticles, with higher activity for {111} facets compared to {100} facets at 32 °C. The relative activity between the facets is ascribed to the adsorption probability, assuming coordination between the phosphoryl oxygen and cerium atoms, but also to the surface density of the Ce doublets with relevant spacing for phosphatase mimetic activity.

2.
Inorg Chem ; 52(21): 12811-7, 2013 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-24156475

RESUMO

ZnO nanocrystals were prepared from polyol-mediated synthesis. Two key parameters, that is, the zinc precursor concentration and the alcohol mixture chosen as synthesis medium, were varied. The increase of the precursor concentration and the decrease of the permittivity of the alcohol mixture were shown to favor the crystallite growth, leading to crystallite sizes ranging from 5 to 35 nm. The aggregation behavior of the nanocrystal units to form or not polycrystalline spheres, depending on the van der Walls interaction density, was shown and explained. Every sample was accurately characterized by X-ray diffraction; cell parameters were extracted from full pattern matching refinements. A clear correlation between crystallite size and cell parameters, that is, an asymptotic decrease of a and c cell parameters versus the crystallite size, was established. A simple model was also successfully developed to interpret the as-established correlation.

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