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Articles:

El Hichou, Ahmed, Diliberto, Sébastien and Stein, Nicolas
Surface and Coatings Technology, 270(0):236-242
2015

Mots clefs: Electrodeposition Zinc oxide film Aluminum doping

Resume: Abstract Undoped and aluminum doped zinc oxide thin films were successfully deposited by electrodeposition technique from aqueous solution onto ITO substrates at optimized experimental conditions. The variations of the structural, electrical and optical properties with the doping concentration were investigated. X-ray diffraction analysis showed typical patterns of the hexagonal ZnO structure for both doped and undoped films. The films are single phase and polycrystalline with the (002) preferred orientation. The grain size, texture coefficient and optical band gap values were evaluated for different aluminum salt concentrations. The films, obtained from a 10? 7 M aluminum electrolyte, exhibit the highest crystallographic quality and lowest electrical resistivity of 2 × 10? 4 ?·cm with an energy band gap of 3.35 eV.

Equipe: Département CP2S : Chimie et électrochimie des matériaux

Escande, Vincent, Petit, Eddy, Garoux, Laetitia, Boulanger, Clotilde and Grison, Claude
ACS Sustainable Chemistry & Engineering,
2015

Resume: A novel Mn-derived catalyst was prepared starting from biomass of Mn-hyperaccumulating plants growing on metal-rich soils. Recovery of this biomass as value-added ?ecocatalysts? provides incentives for the development of phytoextraction programs on soils degraded by mining activities. Characterization of the resulting plant-based ?Eco-Mn?? catalyst by inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF) and X-ray photoelectron spectroscopy (XPS) demonstrated the presence of unusual polymetallic complexes of Mn(II) in the catalyst, along with Fe(III). Incorporation of these species into montmorillonite K10 as solid support provided a supported Eco-Mn? catalyst, whose properties were investigated for alkene epoxidation with H2O2 (30 wt%)/NaHCO3 (0.2 M) as a green terminal oxidizing reagent. The supported Eco-Mn? catalyst demonstrated a high efficiency for styrene epoxidation, with only 0.31 mol% of Mn, a much lower content of Mn than in previously described Mn-derived heterogeneous catalysts. Whereas Fe was also present in the supported Eco-Mn? catalyst, comparison experiments showed that Fe had only a limited role in the catalysis. The water content in the reaction medium had a beneficial effect, increasing the reaction efficiency. The supported Eco-Mn? catalyst was recycled four times without any loss of activity. Comparison of its properties to those of heterogeneous catalysts made by incorporation of commercial MnCl2.4H2O and FeCl3.6H2O highlighted the superior catalytic activity of polymetallic species present in the biosourced catalyst. The substrate scope of the method was extended to various alkenes, including bulky natural products, which were epoxidized with high yields (up to 99%), sometimes much higher than those obtained with already described Mn-derived heterogeneous catalysts. Finally, by simple adjustments of reaction conditions, the method allowed controlled access to aldehydes by oxidative cleavage of various styrene-derived substrates (up to 93% yield). The method thus constitutes a valuable alternative not only to classical epoxidation reagents, but also to oxidative cleavage of styrene-derived molecules, which usually involves toxic and hazardous reagents.

Equipe: Département CP2S : Chimie et électrochimie des matériaux

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