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


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.

Environ Toxicol Pharmacol ; 53: 18-28, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28499266


Degradation and body surface decontamination is vital to prevent the skin penetration of paraoxon (POX), an organophosphorus pesticide, and victims poisoning. CeO2 demonstrated a good efficacy for the degradation of POX. The aim of the study was to develop a model which includes the impact of weight of CeO2, POX and diluent volumes on the degradation kinetics. The modelling was realized with rapid and simple experiments carried out in tubes, in aqueous diluent which contained ions in order to be in accordance with in vitro skin decontamination conditions. CeO2 had degraded from 5% (in case of 7.5mmol of POX per gram of CeO2) to 100% (0.002mmol of POX per gram of CeO2) of POX. Different kinetic models were tested. Using the particle aggregation kinetic model, the simulated and experimental data were in a good accordance. It highlighted the importance of particles aggregation due to salts and consistency of the mix on the degradation efficiency of CeO2. The model worked also really well to predict the degradation efficiency of CeO2 powders during in vitro skin experiments. However, it did not correctly forecast with an aqueous decontaminant, containing CeO2.

Cério/química , Descontaminação/métodos , Nanopartículas Metálicas/química , Modelos Teóricos , Paraoxon/química , Praguicidas/química , Animais , Técnicas In Vitro , Pele , Suínos , Água/química