Publications: Articles

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

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Resume: Silicon nanostructures are synthesized with a DC atmospheric pressure microplasma jet using an Ar/SiH4/H2 gas mixture. The plasma is characterized by OES and imaged using an EMCCD camera. The effect of hydrogen admixture to the formed structures is studied by transmission electron microscopy. Under specific conditions, crystalline silicon nanoparticles grow in an amorphous matrix investigated by electron energy loss spectroscopy. As-grown silicon nanoparticles are collected in ethanol for dynamic light scattering and photoluminescence measurements. The size distribution peaks at 4â??nm. The silicon nanocrystals exhibit roomtemperature photoluminescence that peaks at ~415 and ~465 nm

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Equipe: Département CP2S : Expériences et Simulations des Plasmas Réactifs - Interaction plasma-surface et Traitement des Surfaces ESPRITS

Resume: Psychotria douarrei and Geissois pruinosa are known as a hypernickelophore plants. The study of their chemical characteristics was revisited to demonstrate a novel potential of this natural resource for Green Chemistry. P. douarrei showed a unique composition, which led to a novel concept of plant-based catalytic chemistry. The supported Biginelli reaction illustrated an interest of this concept for green organic synthesis.

Equipe: Département CP2S : Chimie et électrochimie des matériaux