Cyclodextrin-based systems for the stabilization of metallic(0) nanoparticles and their versatile applications in catalysis

International audienceIn order to better respond to environmental standards, the development of metal nanoparticles using green approaches has exponentially grown for the last decade. Cyclodextrins, which are cyclic oligosaccharides composed of 6(α), 7(β) or 8(γ) glucopyranose units, have appeared to be interesting candidates for the synthesis of metal nanoparticles. Indeed, through the ability to form inclusion complexes or supramolecular adducts with organic molecules or metal precursors, cyclodextrins can be successfully employed to stabilize size-controlled zerovalent metallic nanoparticles active for hydrogenation reactions carried out in aqueous or gas-phase media. In this summary of our works, we report that cyclodextrins could be used in various forms and environments: (i) in free form, (ii) in complexed form with appropriate guests molecules, (iii) in combination with polymer matrices, (iv) in thermosensitive hydrogels and (v) immobilized onto porous carbons supports. All these studies highlight the fact that cyclodextrins can be seen as multi-task agents for nanocatalysis

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

In memoriam Professor Jean-Antoine Rioux (1925-2017)

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N-donor ligands based on bipyridine and ionic liquids: an efficient partnership to stabilize rhodium colloids. Focus on oxygen-containing compounds hydrogenation.

International audiencePolynitrogen ligands and/in ionic liquids (ILs) are described as a pertinent tandem to efficiently stabilize rhodium nanoparticles (NPs) in the size range of 2.0 nm for catalytic applications. Several N-donor ligands based on bipyridine skeleton were used as extra protective agents in [BMI][PF(6)] and compared in the hydrogenation of functionalized aromatic compounds at 80 °C and under 40 bar H(2). The nature of the bipyridine derivative and its influence on the coordination mode on the particle surface were proposed to explain the observed different kinetic properties. The hydrogenation of various oxygen-containing arenes was investigated and original results were described in the reduction of anisole and cresols as model lignin compounds, providing a significant ratio of ketone derivatives. A first explanation based on possible reaction routes is proposed to justify the formed products

Amines as effective ligands in iridium-catalyzed decarbonylative dehydration of biosourced substrates

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Competitive hydrogenation/dehalogenation of halogenoarenes with surfactant-stabilized aqueous suspensions of rhodium and palladium colloids: A major effect of the metal nature

International audienceThe original palladium colloidal suspensions with an average size of 2.7 nm have been synthesised by reducing Na2PdCl4 with sodium borohydride and were stabilized by water soluble N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride salt. The catalytic hydrogenation and dehalogenation of various halogenoarenes have been investigated with this aqueous suspension of palladium nanoparticles and compared with the well-known rhodium suspension. The influences of the halogen fragment and the experimental conditions have also been studied. It was observed that the kinetics and selectivity of the competitive dehalogenation/hydrogenation depend on the nature of metal colloids and the hydrogen pressure

Eggplant-Derived Biochar-Halloysite Nanocomposite as Supports of Pd Nanoparticles for the Catalytic Hydrogenation of Nitroarenes in the Presence of Cyclodextrin

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Rhodium Colloidal Suspensions Stabilised by Poly-N-donor Ligands in Non-Aqueous Ionic Liquids: Preliminary Investigation into the Catalytic Hydrogenation of Arenes

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