Nickel phosphide nanocatalysts for the chemoselective hydrogenation of alkynes

[EN] Well-defined 25 nm nickel phosphide nanoparticles act as a colloidal catalyst for the chemoselective hydrogenation of terminal and internal alkynes. Cis-alkenes are obtained in mild conditions with good conversion and selectivity. The phosphorus inserted in the Ni-P nanoparticles is critical for the selectivity of the nanocatalyst. Mechanistic investigations using isotope labeling provide insight on the reactants interaction with the nanoparticles surface. They pinpoint the occurrence of C-H bond cleavage in terminal alkynes during the reaction. (C) 2012 Elsevier Ltd. All rights reserved.The DGA, the Ecole Polytechnique, the CNRS and the UPMC are acknowledged for financial support.Carenco, S.; Leyva Perez, A.; Concepción Heydorn, P.; Boissiere, C.; Mezailles, N.; Sanchez, C.; Corma Canós, A. (2012). Nickel phosphide nanocatalysts for the chemoselective hydrogenation of alkynes. Nano Today. 7:21-28. doi:10.1016/j.nantod.2011.12.003S2128

Dealloying of Cobalt from CuCo Nanoparticles under Syngas Exposure

International audienceThe structure and composition of core−shell CuCo nanoparticles were found to change as a result of cleaning pretreatments and when exposed to syngas (CO + H 2) at atmospheric pressure. In situ X-ray absorption and photoelectron spectroscopies revealed the oxidation state of the particles as well as the presence of adsorbates under syngas. Transmission electron microscopy was used for ex situ analysis of the shape, elemental composition, and structure after reaction. The original core−shell structure was found to change to a hollow CuCo alloy after pretreatment by oxidation in pure O 2 and reduction in pure H 2. After 30 min of exposure to syngas, a significant fraction (5%) of the particles was strongly depleted in cobalt giving copper-rich nanoparticles. This fraction increased with duration of syngas exposure, a phenomenon that did not occur under pure CO or pure H 2. This study suggests that Co and Cu can each individually contribute to syngas conversion with CuCo catalysts

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Nanoparticules contenant des métaux : design et réactivité Metal-Containing Nanoparticles: Design and Reactivity

In this manuscript, a first section discusses the context of current research on nanoparticles design and on the study of their reactivity. A second section describes recent results in the synthesis of metal, metal carbides, metal phosphides and metal oxysulfides nanoparticles. The role of surface ligands in controlling the reactivity of these objects is investigated for a few systems.A last section proposes future direction of work. Finally, the conclusion discusses activities “beyond the bench”, in particular in scientific outreach and for a better recognition of chemistry and chemists in the times to come

Carbon Monoxide-Induced Dynamic Metal-Surface Nanostructuring

International audienceCarbon monoxide is a ubiquitous molecule in surface science, materials chemistry, catalysis and nanotechnology. Its interaction with a number of metal surfaces is at the heart of major processes, such as Fischer-Tropsch synthesis or fuel-cell optimization. Recent works, coupling structural and nanoscale in situ analytic tools have highlighted the ability of metal surfaces and nanoparticles to undergo restructuring after exposure to CO under fairly mild conditions, generating nanostructures. This Minireview proposes a brief overview of recent examples of such nanostructuring, which leads to a discussion about the driving force in reversible and non-reversible situations

Les processus de recrutement pour des postes académiques

International audienceLe Bureau régional du Réseau des Jeunes chimistes Ile-de-France de la Société Chimique de France (RJ-IdF) a organisé à l’automne dernier une demi-journée d’information sur les carrières académiques intitulée « Comprendre les processus de recrutement pour mieux s’y préparer ».Cette action faisait suite à diverses discussions avec des doctorants, docteurs et jeunes recrutés qui ont révélé une méconnaissance des processus de recrutement pour obtenir un poste académique. Certains aspects de la phase de recrutement, parfois mal compris, conduisent en particulier à une autocensure du candidat qui ne dépose pas de dossier