Discovery of a palladium-platinum-gold-mercury bitumen in the Boss mine, Clark County, Nevada

A bitumen containing high concentrations of sulfur, palladium, platinum, gold, and mercury has been found in the Boss mine, Clark County, Nevada, where rich ores of 'invisible' palladium and platinum were mined from 1916 to 1919. The bitumen, analyzed with X-ray energy dispersive spectrometry on areas devoid of discrete particles down to a 40 Å limit, contains 2.74 wt percent Pd + Pt + Au (Pd = 1.85%) and 5.83 wt percent Hg. It is associated with particulate potarite (Pd, Au, Pt) Hg, native gold, plumbojarosite, hydronium jarosite, argentojarosite, florencite, and bismuth oxides. The first four mineral species are also found included in the bitumen. The paragenesis was derivation and formation of bitumen from the local limestone, followed by interaction with the hydrothermal potarite and the supergene jarosite. This type of organic material, highly enriched in platinum group elements, previously had been reported only in Polish Kupferschiefer thucholite.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

TiO2-supported Rh nanoparticles: From green catalyst preparation to application in arene hydrogenation in neat water

45-4 FIELD Section Title:Industrial Organic Chemicals, Leather, Fats, and Waxes 67 Ecole Nationale Superieure de Chimie de Rennes, UMR 6226, CNRS, Rennes, Fr. FIELD URL: written in EnglishInternational audienceTiO2-supported Rh(0) nanoparticles were prepd. by an easy method under mild conditions in neat water. They proved to be highly active catalysts for arene hydrogenation in water with TOFs up to 33 333 h-1. [on SciFinder(R)

Loop-stabilized BAB triblock copolymer morphologies by PISA in water

International audienceA straightforward strategy to synthesize in water, loop-stabilized particles via PISA is developed. These particular structures can in theory be obtained through the synthesis of amphiphilic BAB triblock copolymers, starting from a hydrophilic middle block A, which is chain extended in an aqueous PISA process by two hydrophobic external blocks B. For that purpose, symmetrical bifunctional poly(N,N-dimethylacrylamide) macroRAFT agents with a central benzoic acid group and an alkyl chain as Z group are used in the aqueous dispersion polymerization of diacetone acrylamide. For the first time, stable BAB flower-like particles are formed via PISA in pure water. It is shown that the colloidal stability and the resulting particle morphology (spheres, worms, vesicles) strongly depend on the degree of ionization of the central charge in the stabilizer loop, thus on the pH at which PISA is performed. Moreover, the influence of the length of the alkyl Z group (dodecyl and butyl alkyl chains) on the colloidal stability is studied

Preparation of Highly Anisotropic Cobalt Ferrite/Silica Microellipsoids Using an External Magnetic Field

International audienceMagnetic cobalt ferrite/silica microparticles having both an original morphology and an anisotropic nanostructure are synthesized through the use of an external magnetic field and nanoparticles characterized by a high magnetic anisotropy. The association of these two factors implies that the ESE (emulsion and solvent evaporation) sol-gel method employed here allows the preparation of silica microellipsoids containing magnetic nanoparticles aggregated in large chains. It is clearly shown that without this combination, microspheres characterized by an isotropic distribution of the magnetic nanoparticles are obtained. While the chaining of the cobalt ferrite nanoparticles inside the silica matrix is related to the increase of their magnetic dipolar interactions, the ellipsoidal shape of the microparticles may be explained by the elongation of the sol droplets in the direction of the external magnetic field during the synthesis. Because of their highly anisotropic structure, these microparticles exhibit permanent magnetic moments, which are responsible, at a larger scale, for the existence of strong magnetic dipolar interactions. Therefore, when they are dispersed in water, the microellipsoids self-assemble into large and irregular chains. These interactions can be reinforced by the use of external magnetic field, allowing the preparation of very large permanent chains. This research illustrates how nanostructured particles exhibiting complex architectures can be elaborated through simple, fast, and low-cost methods, such as the use of external fields in combination with soft chemistry

Using Prussian blue analogue nanoparticles confined into ordered mesoporous silica monoliths as precursors of oxides

International audiencePowdered Prussian blue analogues (PBAs) and PBAs confined in ordered mesoporous silica monoliths were used as oxide precursors through thermal treatment under an oxidizing atmosphere. The study focuses on the transformation of the alkali cation-free CoCo PBA of chemical formula K0.1CoII4[CoIII(CN)6]2.7·20 H2O. The compounds were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), IR spectroscopy and small-angle X-ray scattering (SAXS), and the magnetic properties of the calcined samples were investigated. In both cases, powdered and confined PBAs, the coordination polymers are transformed into well-crystallized Co3O4 spinel oxide. In the case of the confined PBA, isolated Co3O4 single crystals confined within the ordered mesoporosity of the monoliths were evidenced by HRTEM. A preliminary study shows an effect of particle size and confinement on the magnetic properties of the confined oxide particles

From mesoporous alumina to Pt/Al2O3 catalyst: A comparative study of the aluminas synthesis in aqueous medium, physicochemical properties and stability

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Co, Fe and CoFe oxide nanoparticle assemblies within an ordered silica matrix: effects of the metal ions and synthesis pathway on the microstructure and magnetic properties

The magnetic properties of nanoparticle assemblies strongly depend on the structural and morphological characteristics of the individual nanoparticles as well as on their organization within the assembly. Here, we present the synthesis of cobalt and/or iron oxide nanoparticles within the ordered mesoporosity of a silica monolith by two different synthesis pathways (using either Prussian blue analogues or nitrate salts as a precursor). We describe the influence of the nature of the metal ion and of the synthesis pathway on the morphology of the nanoparticles. With respect to these observations, we present and discuss the temperature-dependent magnetic behaviors of the final nanocomposites

Facile synthesis of palladium nanowires by a soft templating method

International audienceVery long and thin monocrystalline Pd nanowires were synthesized by decomposition using hydrazine vapour treatment of Pd2(DBA)3 confined in the oil phase of a hexagonal mesophase. The mesophase is composed of toluene-swollen tubes, doped with the Pd precursor, stabilized by a monolayer of surfactant and cosurfactant molecules, and arranged on a triangular lattice in water. Our synthesis is selective and the experiments show that both the confinement and the nature of the surfactant are essential to obtain these Pd nanowires

Fluorescent core-shell nanoparticles and nanocapsules using comb-like macromolecular RAFT agents: synthesis and functionalization thereof

International audienceFluorescent nanoparticles and nanocapsules (FNPs) were synthesized via a one-pot RAFT miniemulsion process copolymerizing BODIPY-methacrylate and styrene in water. Ultra-bright sub-100 nm core–shell nanoparticles could be obtained with BODIPY covalently linked in the core, and possessing various shells. The nature and architecture of the particle shells could be tuned by using different macromolecular RAFT (macro-RAFT) agents in the miniemulsion polymerization process. The macro-RAFT agents were composed of poly(ethylene oxide) acrylate (PEOA) and/or acrylic acid (AA), owing to their biocompatibility and functionality respectively, in different proportions. Interestingly, with comb-like macro-RAFT agents comprising a high number of PEOA, nanocapsules were formed, while with linear macro-RAFT agents or with those exhibiting a high number of AA, full core–shell nanoparticles were obtained. For all the structures the control over the polymerization, the size, morphology, and zeta-potential as well as the photophysical properties were measured and compared with FNPs exhibiting a linear PEO-b-PAA block copolymer shell structure (C. Grazon, J. Rieger, R. Méallet-Renault, G. Clavier and B. Charleux, Macromol. Rapid Commun., 2011, 32, 699). Regardless of the shell structures, the brightness of the formed nanoparticles was estimated to be 100–1000 times higher than that of quantum dots. Ultimately, the shell of the different FNPs was functionalized with a second fluorophore via the AA's carboxyl groups. Thus, water-soluble ultra-bright FNPs with two fluorophores in distinct environments (water and in polystyrene) were obtained. They should have great potential for bioimaging applications