Alexander Yu. Ustinov

One-pot green synthesis of luminescent gold nanoparticles using imidazole derivative of chitosan

Water soluble luminescent gold nanoparticles with average size 2.3nm were for the first time synthesized by completely green method of Au(III) reduction using chitosan derivative-biocompatible nontoxic N-(4-imidazolyl)methylchitosan (IMC) as both reducing and stabilizing agent. Reduction of Au(III) to gold nanoparticles in IMC solution is a slow process, in which coordination power of biopolymer controls both reducing species concentration and gold crystal growth rate. Gold nanoparticles formed in IMC solution do not manifest surface plasmon resonance, but exhibit luminescence at 375nm under UV light excitation at 230nm. Due to biological activity of imidazolyl-containing polymers and their ability to bind proteins and drugs, the obtained ultra-small gold nanoparticles can find an application for biomolecules detection, bio-imaging, drug delivery, and catalysis. Very high catalytic activity (as compared to gold nanoparticles obtained by other green methods) was found for Au/IMC nanoparticles in the model reaction of p-nitrophenol reduction providing complete conversion of p-nitrophenol to p-aminophenol within 180-190s under mild conditions.

Kinetics of soot oxidation catalyzed by CuMoO4

The kinetics of the catalytic soot combustion was studied for each identified stage of structural transformations of the CuMoO4 catalyst. The formation of the catalytically active phase Cu4−xMo3O12 during the process through the redox transformation of the catalyst is controlled by the reduction of CuMoO4 on the catalyst surface by the soot. The oxidation of the soot by the active phase of the catalyst could be described by the Avrami-Erofeev equation for the three-dimensional growth of randomly formed combustion centers. The quantity of the Cu4−xMo3O12 molybdate on the catalyst surface remains constant throughout the catalytic reaction. A macrokinetic model equation describing dependence of the total reaction rate from the rates of redox catalyst transformation and catalytic soot oxidation steps was obtained.

Composition, Structure, and Catalytic Activity of SiO2+TiO2/Ti and MnOx+SiO2+TiO2/Ti Composites Formed by Combination of the Methods of Plasma Electrolytic Oxidation, Impregnation and Annealing

New data on the structure of silicon-containing oxide layers SiO2+TiO2 on titanium formed by the method of plasma electrolytic oxidation (PEO) as well as on the structure and catalytic activity in CO oxidation of MnOx+SiO2+TiO2/Ti composites formed on their basis using impregnation and annealing methods have been obtained. It has been demonstrated that silicon and titanium are rather homogeneously distributed over the SiO2+TiO2 coating bulk. The coating outer part is silicon-enriched titanium-depleted. The MnOx+SiO2+TiO2/Ti composites catalyze the CO conversion at temperatures above 100°C. Nanowhiskers consisting predominantly of manganese oxides have been found on the surface of the MnOx+SiO2+TiO2/Ti composites.

Magnetic Properties of Plasma Electrolytic Iron-Containing Oxide Coatings on Aluminum and Simulation of Demagnetizing Process

Magnetic properties of iron-containing coatings obtained on aluminum by plasma electrolytic oxidation were analyzed in this paper. Theoretical curves of demagnetization of these objects are obtained. It is shown that the magnetic states of the analyzed samples can be caused by the presence of several phases with very different magnetic properties.

Quantum chemical calculations of anion complex [B12Hx(CF3)12-x]2−, x = 9 – 12

The geometric, energetic, spectral and electronic properties of the most stable isomers of B12Hx(CF3)12-X2− anion complex with x = 9 – 12 have been studied using Density Functional Theory (B3LYP/6-311++G**). It was shown that these isomers are characterized by the preference to form the most symmetric structures with uniformly distributed charge densities. However, when replacing a hydrogen atom with fluoromethyl group, an inductive effect occurs. Blue shifts in the IR spectrum compared to the vibrations of the free CF3 molecule are in the range of 2 – 69 cm−1 and points to the stability of B12Hx(CF3)12-x2− anions.

Nanostructured Composite FeOF-FeF3 as Anode Material for Li-Ion Battery: The Original Method of Pulsed High-Voltage Discharge

The prospects of an original method of pulsed high-voltage discharge in synthesis of nanostructured FeOF–FeF3 composite anode for Li-ion battery has been demonstrated. Scanning electron microscopy investigation shows as-synthesized FeOF–FeF3 consists of nanocrystallites ranging in sizes from 10 to 300 nm. Galvanostatic discharge–charge cycling of the Li/FeOF–FeF3 half-cell at current density of 10 mA g–1 in the range from 3.0 to 0.005 V yields 210 mAh g–1 after 10 cycles. The electrochemical reaction mechanism within the Li/FeOF–FeF3 has been investigated by the cyclic voltammetry method.

Effect of Hf-doping on electrochemical performance of anatase TiO2 as an anode material for lithium storage

Hafnium-doped titania (Hf/Ti = 0.01; 0.03; 0.05) had been facilely synthesized via a template sol–gel method on carbon fibre. Physico-chemical properties of the as-synthesized materials were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis and Brunauer–Emmett–Teller measurements. It was confirmed that Hf4+ substitute in the Ti4+ sites, forming Ti1–xHfxO2 (x = 0.01; 0.03; 0.05) solid solutions with an anatase crystal structure. The Ti1–xHfxO2 materials are hollow microtubes (length of 10–100 µm, outer diameter of 1–5 µm) composed of nanoparticles (average size of 15–20 nm) with a surface area of 80–90 m2 g–1 and pore volume of 0.294–0.372 cm3 g–1. The effect of Hf ion incorporation on the electrochemical behaviour of anatase TiO2 in the Li-ion battery anode was investigated by galvanostatic charge/discharge and electrochemical impedance spectroscopy. It was established that Ti0.95Hf0.05O2 shows significantly higher reversibility (154.2 mAh g–1) after 35-fold cycling at a C/10 rate in comparison with undoped titania (55.9 mAh g–1). The better performance offered by Hf4+ substitution of the Ti4+ into anatase TiO2 mainly results from a more open crystal structure, which has been achieved via the difference in ionic radius values of Ti4+ (0.604 Å) and Hf4+ (0.71 Å). The obtained results are in good accord with those for anatase TiO2 doped with Zr4+ (0.72 Å), published earlier. Furthermore, improved electrical conductivity of Hf-doped anatase TiO2 materials owing to charge redistribution in the lattice and enhanced interfacial lithium storage owing to increased surface area directly depending on the Hf/Ti atomic ratio have a beneficial effect on electrochemical properties.

Correlation of the Microrelief of the Surface of Structure and Magnetic Properties of Oxidic Coverings on the Titan

The technique of system parametrization of a microrelief of surfaces plasma electrolytic oxidation coverings on the titan is offered. Correlation of topology of surfaces of oxidic coverings with their thickness and magnetic properties is established.