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51.
Hexane was reacted in mixtures with excess hydrogen on 5% Rh on different supports: Al2O3 and SiO2, the latter catalyst in two states: after reduction at 603 K (LT) and after a prereduction at 1253 K (HT). The main reaction was hydrogenolysis. The catalysts were characterized with the fragment composition at different temperatures and hydrogen pressures. Two surface states could be distinguished: one with more hydrogen favored single rupture, the other with less hydrogen preferred multiple fragmentation. The transition between these states could be rather abrupt, as the surface hydrogen availability changed. The tendency to produce multiple fragments increased in the order Rh/Al2O3< Rh/SiO2-LT < Rh/SiO2-HT. 相似文献
52.
A Tris(triazolate) Ligand for a Highly Active and Magnetically Recoverable Palladium Catalyst of Selective Alcohol Oxidation Using Air at Atmospheric Pressure
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Dr. Dong Wang Christophe Deraedt Dr. Lionel Salmon Christine Labrugère Laetitia Etienne Dr. Jaime Ruiz Prof. Didier Astruc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(17):6501-6510
High efficiency and selectivity, easy magnetic recovery and recycling, and use of air as the oxidant at atmospheric pressure are major objectives for oxidation catalysis in terms of sustainable and green processes. A tris(triazolyl) ligand, so far only used in copper‐catalyzed alkyne azide cycloadditions, was found to be extremely efficient in SiO2/γ‐Fe2O3‐immobilized palladium complexes. It was characterized by inductively coupled plasma (ICP) analysis, transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy‐dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectra (XPS) and found to fulfill the combined conditions for the selective oxidation of alcohols to aldehydes and ketones. 相似文献
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Marianne Vandenbossche Gesine Gunkel-Grabole Anja Car Laetitia Bernard Patrick Rupper Katharina Maniura-Weber Manfred Heuberger Greta Faccio Dirk Hegemann 《Plasma Chemistry and Plasma Processing》2018,38(4):851-870
Using low pressure plasma polymerization, nano-scaled oxygen-rich plasma polymer films (CO) were deposited onto pristine silicon wafers as well as on nitrogen-containing plasma polymer (CN) model surfaces. We investigate the influence of the nature of the substrate as well as a potential sub-surface effect emerging from the buried CO/CN interface, just nanometers below the surface. X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry revealed two important phenomena that occurred during the deposition of the terminal CO layer: (1) a strong degree of oxidation, already for 1 nm nominal thickness, and (2) a gradual transition in chemical composition between the two layers, clearly indicating that effectively a vertical chemical gradient results, even when a two-step coating process was applied. Such terminal gradient film structures were used to study film stability in aqueous environments. Molecular rearrangements were scrutinized in the top-surface in contact with water and we found that the top-surface chemistry and wetting properties of the oxygen-rich termination layer matched those of thick CO reference coatings. Nevertheless, the adsorption of green fluorescent protein (GFP) was observed to be sensitive to the CO terminal layer thickness. Namely, an enhanced protein adsorption was observed for 1–2 nm thick CO layers on CN, whereas a significantly reduced protein adsorption was seen on ≥?3 nm thick CO terminal layers. We conclude that both, surface and sub-surface conditions significantly affect protein adsorption as opposed to the traditional consideration of surface properties alone. 相似文献
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Laetitia Ancel Agnieszka Niedźwiecka Colette Lebrun Christelle Gateau Pascale Delangle 《Comptes Rendus Chimie》2013,16(6):515-523
Lanthanide-binding peptides are very attractive for the design of bioprobes. Indeed, they combine the amazing properties of lanthanide ions, such as their time-resolved luminescence (Eu, Tb) or electronic relaxation (Gd) to the characteristics of the peptide scaffold, such as large solubility in water and ability to recognize biological substrates. Peptides derived from natural amino acids are reviewed in a first section. Some of their lanthanide complexes have already demonstrated their efficiency in determining protein structures and functions. Then, we will show how insertion of chelating unnatural amino acids modulates peptide-lanthanide complexes properties, such as luminescence and stability. 相似文献
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Kavita Kumar Laetitia Dubau Michel Mermoux Jingkun Li Andrea Zitolo Jaysen Nelayah Frdric Jaouen Frdric Maillard 《Angewandte Chemie (International ed. in English)》2020,59(8):3235-3243
Fe‐N‐C catalysts containing atomic FeNx sites are promising candidates as precious‐metal‐free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The durability of Fe‐N‐C catalysts in fuel cells has been extensively studied using accelerated stress tests (AST). Herein we reveal stronger degradation of the Fe‐N‐C structure and four‐times higher ORR activity loss when performing load cycling AST in O2‐ vs. Ar‐saturated pH 1 electrolyte. Raman spectroscopy results show carbon corrosion after AST in O2, even when cycling at low potentials, while no corrosion occurred after any load cycling AST in Ar. The load‐cycling AST in O2 leads to loss of a significant fraction of FeNx sites, as shown by energy dispersive X‐ray spectroscopy analyses, and to the formation of Fe oxides. The results support that the unexpected carbon corrosion occurring at such low potential in the presence of O2 is due to reactive oxygen species produced between H2O2 and Fe sites via Fenton reactions. 相似文献
59.
Molecularly Imprinted Polymers: Compromise between Flexibility and Rigidity for Improving Capture of Template Analogues
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Antonelle Pardo Dr. Laetitia Mespouille Prof. Dr. Philippe Dubois Prof. Dr. Bertrand Blankert Prof. Dr. Pierre Duez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(12):3500-3509
New synthetic strategies for molecularly imprinted polymers (MIPs) were developed to mimic the flexibility and mobility exhibited by receptor/enzyme binding pockets. The MIPs were prepared by bulk polymerization with quercetin as template molecule, acrylamide as functional monomer, ethylene glycol dimethacrylate as cross‐linker, and THF as porogen. The innovative grafting of specific oligoethylene glycol units onto the imprinted cavities allowed MIPs to be obtained that exhibit extended selectivity towards template analogues. This synthetic strategy gives promising perspectives for the design of molecular recognition of molecules based on a congruent pharmacophore, which should be of interest for drug development. 相似文献
60.
Antoine dAleman Oscar Gayraud Catherine Fressign Emilie Petit Laetitia Bailly Jacques Maddaluno Michaël De Paolis 《Chemical science》2023,14(8):2107
The lactonization of 2-(2-nitrophenyl)-1,3-cyclohexanediones containing an alcohol side chain and up to three distant prochiral elements is reported by isomerization under the mediation of simple organocatalysts such as quinidine. Through a process of ring expansion, strained nonalactones and decalactone are produced with up to three stereocenters in high er and dr (up to 99 : 1). Distant groups, including alkyl, aryl, carboxylate and carboxamide moieties, were examined.Nine- and ten-membered lactones with up to three non-vicinal stereocenters (up to 99 : 1 er and dr) were prepared by ring expansion of prochiral alcohols (21 examples) upon exposure to quinidine and derivatives. 相似文献