Colloidal ruthenium catalysts for selective quinaldine hydrogenation: Ligand and solvent effects

International audienceColloidal Ru nanoparticles (NP) display interesting catalytic properties for the hydrogenation of (hetero)arenes as they proceed efficiently in mild reaction conditions. In this work, a series of Ru based materials was used in order to selectively hydrogenate quinaldine and assess the impact of the stabilizing agent on their catalytic performances. Ru nanoparticles stabilized with polyvinylpyrrolidone (PVP) and 1‐adamantanecarboxylic acid (AdCOOH) allowed to obtain 5,6,7,8‐tetrahydroquinaldine with a remarkable selectivity in mild reaction conditions by choosing the suitable solvent. The presence of a carboxylate ligand on the surface of the Ru NP led to an increase in the activity when compared to Ru/PVP catalyst. The stabilizing agent had also an impact on the selectivity, as carboxylate ligand modified catalysts promoted the selectivity towards 1,2,3,4‐tetrahydroquinaldine, with bulky carboxylate displaying the highest ones

In Situ Ruthenium Catalyst Modification for the Conversion of Furfural to 1,2-Pentanediol

International audienceExploiting biomass to synthesise compounds that may replace fossil-based ones is of high interest in order to reduce dependence on non-renewable resources. 1,2-pentanediol and 1,5-pentanediol can be produced from furfural, furfuryl alcohol or tetrahydrofurfuryl alcohol following a metal catalysed hydrogenation/C-O cleavage procedure. Colloidal ruthenium nanoparticles stabilized with polyvinylpyrrolidone in situ modified with different organic compounds are able to produce 1,2-pentanediol directly from furfural in a 36% of selectivity at 125 °C under 20 bar of H2 pressure

An organometallic approach for very small maghemite nanoparticles: Synthesis, characterization, and magnetic properties

Maghemite (gamma-Fe2O3) nanoparticles stabilized by long-alkyl-chain amines are synthesized by using an orgonometallic approach. This method consists of the hydrolysis and oxidation of an organometallic precursor, Fe[N(SiMe3)(2)](2), in the presence of amine ligands as stabilizing agent in an organic solvent, namely tetrohydrofuron or toluene. Whatever the experimental conditions, particles with a diameter of 2.8 nm are obtained. The use of high-resolution transmission electron microscopy and wide-angle X-ray scattering, together with Mossbauer spectroscopy and SQuld magnetometry, allows a complete characterization of these particles. Herein, we show that their structure is composed of a well-ordered core surrounded by a more disordered shell. The size of the latter varies from 0.65 to 0.50 nm depending on the experimental conditions and is of prime importance for the understanding of the magnetic properties. We demonstrate that the shorter the alkyl chain length of the amine 1) the better the crystallinity of the particle's core and 2) the stronger the interparticle interactions

Urea-assisted cooperative assembly of phosphorus dendrimer–zinc oxide hybrid nanostructures

International audienceHerein, phosphorus dendrimer-assisted sol–gel mineralisation of molecular zinc species is explored to access porous dendrimer–zinc oxide hybrid materials. Screening of various second-generation dendrimers peripherally-functionalized by phosphonate, catechol, ammonium and acetylacetonate groups showed a marked difference in terms of their morphology and hybrid composition, thereby highlighting the importance of surface-chemistry for the nucleation and growth of the zinc oxide inorganic phase. The homogeneous composition and distribution of the two dissimilar dendritic and metal oxide building-blocks is reached using phosphonate-terminated and catechol-terminated dendrimers. In contrast, significant leaching occurs in the case of ammonium-terminated and acetylacetonate-terminated dendrimers, leading rather to an enriched zinc oxide monophasic system. When urea was added as a ternary component, beyond improving mineralisation, interesting cooperative assembly was observed, particularly in the case of phosphonate-terminal dendrimers, which resulted in the formation of mesoporous phosphorus-containing lamellar zinc oxide hybrid materials

Oxidation of methane to methanol over Pd@Pt nanoparticles under mild conditions in water

10.1039/D1CY00273

Iron/iron oxide nanoparticles coated with silica as a nanoplatform for multimodal biomedical imaging

International audienc