Elena Suvorova Buffat

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Dispersed Ag nanoparticles were prepared in aqueous solutions in the presence of pure poly[2-(dimethylamino)ethyl methacrylate] (poly-DMAEMA), poly[2-deoxy-2-methacrylamido-d-glucose] (poly-MAG), and their copolymers of poly[MAG–DMAEMA] with different mole ...

Synthesis of Pd nanoparticles with controlled size (d(Pd) = 1-3.6 nm) was carried out within the pores of the mesoporous HMS and SBA-15 silicas. Pd was ion-exchanged on non-calcined silicas, prepared by solvent extraction of the templates. A high concentration of silanol groups on the mesopore surface allowed attaining Pd loading up to 4.4. wt.%. The Pd/HMS and Pd/SBA-15 were characterised by chemical analysis, XRD, N2 adsorption-desorption and transmission electron microscopy (TEM) methods. The materials p

Wetlands often act as sinks for uranium and other trace elements. Our previous work at a mining-impacted wetland in France showed that a labile noncrystalline U(IV) species consisting of U(IV) bound to Al-P-Fe-Si aggregates was predominant in the soil at locations exhibiting a U-containing clay-rich layer within the top 30 cm. Additionally, in the porewater, the association of U(IV) with Fe(II) and organic matter colloids significantly increased U(IV) mobility in the wetland. In the present study, within th

It has generally been assumed that the bioreduction of hexavalent uranium in groundwater systems will result in the precipitation of immobile uraninite (UO2). In order to explore the form and stability of uranium immobilized under these conditions, we intr ...

Chromate is one of the major anthropogenic contaminants on Earth. Leucobacter chromiiresistens is a highly chromate-resistant strain, tolerating chromate concentrations in LB medium of up to 400 mM. In response to chromate stress, L. chromiiresistens forms ...

A comparative characterization of crystal structure, morphology, sizes, and orientation in Ca phosphate precipitation from aqueous solutions, the mineral phase in bones, and mineral deposits on cardiac valves has been performed by high-resolution transmission electron microscopy to model possible mechanisms of Ca loss by bones. Physiological changes occurring in organisms can lead to deep perturbations of the natural calcium phosphate supersaturation and its local distribution, which in turn influences the

The chemical stability of bacteriogenic “UO2” is one of the seminal issues governing its success as an in-situ waste form in remediated subsurface locations. Little detail is known about the structure and reactivity of this material, but based on comparison to its closest abiotic analog, UO2+x (0 < x < 0.25), we expect that it is complex and defected, likely to exhibit non- stoichiometry, and capable of structurally incorporating common groundwater cations as well as U(VI). This complex behavior is expected

Desulfotomaculum reducens strain MI-1 is a Gram-positive, sulfate-reducing bacterium also capable of reducing Fe(III). Metal reduction in Gram-positive bacteria is poorly understood. Here, we investigated Fe(III) reduction with lactate, a non-fermentable s ...

The chemical stability of bacteriogenic “UO2” is one of the seminal issues governing its success as an in-situ waste form in remediated subsurface locations. Little detail is known about the structure and reactivity of this material, but based on comparison to its closest abiotic analog, UO2+x (0 < x < 0.25), we expect that it is complex and defected, likely to exhibit non- stoichiometry, and capable of structurally incorporating common ground water cations as well as U(VI). This complex behavior is expecte

High-resolution transmission electron microscopy (HRTEM), electron microdiffraction, and X-ray diffraction were used to study hydroxyapatite specimens with particle sizes from a few nanometers to several hundreds of nanometers. Diffuse scattering (without clear reflections in transmission diffraction patterns) or strongly broadened peaks in X-ray diffraction patterns are characteristic for agglomerated hydroxyapatite nanocrystals. However, HRTEM and microdiffraction showed that this cannot be considered as

The effects of 107 MeV Kr-84(17+) ion irradiation on YBa2Cu3O7-x-based second-generation coated conductors were investigated using a combination of transmission electron microscopy, diffraction and X-ray energy dispersive spectrometry. Defects 3-5 nm in di ...

High-resolution transmission electron microscopy (HRTEM) and HRTEM simulation by the Bloch wave method (JEMS) are used to determine the structure and thickness of micro- and nanocrystals of biominerals and hydroxyapatite grown from aqueous solutions. It is established that thin (from one to several lattice parameters) crystals, including hydroxyapatite in mineralized biological tissues, are usually formed in low-temperature (up to 40degreesC) solutions. Relatively thick (up to several tens of lattice parame

Nano- and thin-film technologies based on novel systems associating metals particles to polymer matrix open a broad range of different applications. Such composites were found to be more efficient and safe, for instance, in biomedical needs. The Ag/poly(N- ...

The structure of Al, Ge, Mo-doped Higher Manganese Silicide (HMS) crystals with the general formulas Mn(Si0.99Ge0.01)(1.75), Mn(Si0.995Ge0.005)(1.75) and (Mn0.98Mo0.02)(Si0.98Ge0.02)(1.75)Al-0.01 was investigated by scanning and transmission electr ...

Oxidative dissolution controls uranium release to (sub)oxic pore waters from biogenic uraninite produced by natural or engineered processes, such as bioremediation Laboratory studies show that uraninite dissolution is profoundly influenced by dissolved oxy ...

Gold nanoparticles were supported on activated carbon fibers (ACF) using the aq. soln. of [Au(en)2]Cl3 via ion-exchange with surface hydroxyl groups followed by redn. in H2. The obtained catalysts were tested in CO oxidn. at room temp. Surface phenolic groups fix Au3+-ions leading to the formation of small Au particles (.apprx.5 nm) after the redn. with high activity in the reaction. AAS, TPD, HRTEM/EDAX and XPS were used for characterization of the catalysts and supports.

The reduction of soluble hexavalent uranium to tetravalent uranium can be catalyzed by bacteria and minerals. The end-product of this reduction is often the mineral uraninite, which was long assumed to be the only product of U(VI) reduction. However, recen ...

High resolution transmission electron microscopy (HRTEM) and X-ray energy dispersive spectroscopy (EDS) were applied to study the structure of hydroxyapatite (HAP) coatings deposited by plasma spraying on different substrates (Cu, Cr, Ni, NaCl, BaF2). Coatings were obtained with a 13.56 MHz RF argon plasma at 1 Pa by placing a HAP target as the RF electrode. The typical rate of coating formation was about 1.0 - 1.5 nm/s and the total thickness was 350 - 400 nm. For all coating conditions and substrates inve

Elena Suvorova Buffat

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Mechanism of formation of silver nanoparticles in MAG-DMAEMA copolymer aqueous solutions

Pd/SiO2 catalysts: synthesis of Pd nanoparticles with the controlled size in mesoporous silicas

Geochemical control on uranium(IV) mobility in a mining-impacted wetland

Uranium speciation and stability after reductive immobilization in sediments

Chromate Resistance Mechanisms in Leucobacter chromiiresistens

Model of the mechanism of Ca loss by bones under microgravity and earth conditions

The effect of competing electron acceptors on U(VI) reduction by Desulfotomaculum reducens

Biogeochemical processes governing the stability of bacteriogenic UO2+x

Characterization of the surfaceome of the metal-reducing bacterium Desulfotomaculum reducens

Coupled Biogeochemical processes governing the stability of bacteriogenic UO2+x

Size effect in X-ray and electron diffraction patterns from hydroxyapatite particles

Structure analysis of the YBCO layer in Ag/YBCO/metal oxide buffer/Hastelloy composite tape before and after 107 MeV Kr17+ irradiation

HRTEM simulation in determination of thickness and grain misorientation for hydroxyapatite crystals

Stability of Ag nanoparticles dispersed in amphiphilic organic matrix

Structure of precipitates and orientation relationships in Al, Ge, Mo-doped higher manganese silicide crystals

Structural similarities between biogenic uraninites produced by phylogenetically and metabolically diverse bacteria

Long-term in-situ oxidation of biogenic uraninite in an alluvial aquifer: impact of dissolved oxygen and calcium

Gold nanoparticles on activated carbon fibers: Role of carbon surface groups for controlling the Au-particle size and catalytic activity

Quantitative separation of monomeric U(IV) from UO2 in products of U(VI) reduction

Nanostructure of hydroxyapatite coatings sprayed in argon plasma