The Study of Thermal Stability of Mn-Zr-Ce, Mn-Ce and Mn-Zr Oxide Catalysts for CO Oxidation.

MnOx-CeO2, MnOx-ZrO2, MnOx-ZrO2-CeO2 oxides with the Mn/(Zr + Ce + Mn) molar ratio of 0.3 were synthesized by coprecipitation method followed by calcination in the temperature range of 400-800 °C and characterized by XRD, N2 adsorption, TPR, TEM, and EPR. The catalytic activity was tested in the CO oxidation reaction. It was found that MnOx-CeO2, MnOx-ZrO2-CeO2, MnOx-ZrO2 catalysts, calcined at 400-500 °C, 650-700 °C and 500-650 °C, respectively, show the highest catalytic activity in the reaction of CO oxidation. According to XRD and TEM results, thermal stability of catalysts is determined by the temperature of decomposition of the solid solution Mnx(Ce,Zr)1-xO2. The TPR-H2 and EPR methods showed that the high activity in CO oxidation correlates with the content of easily reduced fine MnOx particles in the samples and the presence of paramagnetic defects in the form of oxygen vacancies. The maximum activity for each series of catalysts is associated with the start of solid solution decomposition. Formation of active phase shifts to the high-temperature region with the addition of zirconium to the MnOx-CeO2 catalyst.

"Missing" One-Dimensional Red-Phosphorus Chains Encapsulated within Single-Walled Carbon Nanotubes.

We identify the "missing" 1D-phosphorus allotrope, red phosphorus chains, formed in the interior of tip-opened single-walled carbon nanotubes (SWCNTs). Via a comprehensive experimental and theoretical study we show that in intermediate diameter cavities (1.6-2.9 nm), phosphorus vapor condenses into linear P8]P2 chains and fibrous red-phosphorus type cross-linked double-chains. Thermogravimetric and X-ray photoelectron spectroscopy analysis estimates ∼7 atom % of elemental phosphorus in the sample, while high-resolution energy dispersive X-ray spectroscopy mapping reveals that phosphorus fills the SWCNTs. High-resolution transmission electron microscopy (HRTEM) shows long chains inside the nanotubes with varying arrangement and packing density. A detailed match is obtained between density functional theory (DFT) simulations, HRTEM, and low-frequency Raman spectroscopy. Notably, a signature spectroscopic signal for phosphorus chain cross-linking is identified. When coupled with reinterpretation of literature data and wide-ranging DFT calculations, these results reveal a comprehensive picture of the diameter dependence of confined 1D-phosphorus allotropes.

Formation of gallic acid layer on γ-AlOOH nanoparticles surface and their antioxidant and membrane-protective activity.

In the reported study we prepared gallic acid modified γ-AlOOH nanoparticles. We proposed mechanism of phenolic compounds binding on the alumina, suggesting covalent and electrostatic interactions. Most of the properties of alumina nanoparticles (NPs) are unchanged, but there is partial reduction of surface charge. Prepared samples are colloidally stable hydrosols. It allowed us to perform biological studies on cellular and non-cellular models, which showed nontoxicity of both pure and hybrid γ-AlOOH nanoparticles. Furthermore, pure alumina NPs exhibit antioxidant properties, which are enhanced after gallic acid immobilization on their surface. Also, hybrid alumina-gallic acid NPs showed membrane-protective activity.

Direct TEM observation of the "acanthite α-Ag2S-argentite ß-Ag2S" phase transition in a silver sulfide nanoparticle.

For the first time, the α-Ag2S (acanthite)-ß-Ag2S (argentite) phase transition in a single silver sulfide nanoparticle has been observed in situ using a high-resolution transmission electron microscopy method in real time. Colloid solutions of Ag2S nanoparticles and nanostructured powders of silver sulfide have been synthesized by one-stage chemical bath deposition from an aqueous solution of silver nitrate, sodium sulfide and sodium citrate. Ag2S nanoparticles were heated to different temperatures directly in an electronic microscope by regulating the energy of the electron beam. This allowed observation of the transition of acanthite into argentite and the reversible transition of argentite into acanthite in real time, and this phase transition to be filmed. Temperature dependence of the lattice constant a arg of argentite ß-Ag2S in the temperature range 448-723 K is established by in situ high-temperature X-ray diffraction. The orientation relationships between the monoclinic acanthite α-Ag2S and the body-centered cubic argentite ß-Ag2S are determined. It is shown that the possible distances between silver atoms in cubic argentite, in contrast to those in acanthite, are too small for the positions of the metal sublattice to be occupied by Ag atoms with a probability equal to 1.

Silica-containing inclusions in the cytoplasm of diatom Synedra acus.

Cells of the araphid pennate diatom Synedra acus subsp. radians contain large inclusion (1-15 µm) storing silica, as revealed by transmission electron microscopy and EDX-analysis. The size of the inclusions increases with the time of cultivation of diatoms. Approximate concentration of SiO2 in the inclusions is 1-4%. It is assumed that silica in the inclusions is present as gelatinized silica-gel. These results explain the possible mechanism of transport of silicic acid into the cell against the concentration gradient.