Synthesis and structure of macrocyclic dinickel(II) complex with 5-(4-pyridyl)tetrazolate as coligand

The dinuclear nickel(II) complex [Ni2LmClO4] + , where Lm represents a 24-membered macrocyclic hexaaza-dithiophenolate ligand, reacts with 5-(4-pyridyl)tetrazole (PyrCN4H) to give the dinuclear complex [Ni2Lm(PyrCN4)]+ . The new complex was both isolated as perchlorate or tetraphenylborate salts and characterised by elemental analysis and IR spectroscopy. The structure of [Ni2Lm(PyrCN4)]BPh4 ⋅ MeCN was determined by single crystal X-ray diffraction, showing that tetrazolate units are in a N2,N3-bridging mode to generate dioctahedral N3Ni(µ-S)2(µ-N4CPyr)NiN3 core.

Quantum chemical study of NO reduction mechanism on Ag /Al2O3 catalysts

It was shown that N2O content among NO reduction products increases with an increase of the silver concentration in the catalyst because the nature of the catalytic centers changes and leads to a subsequent change in the mechanism of the reaction. Two reaction mechanisms were proposed and studied by means of quantum chemistry: a two-stage mechanism that proceeds via NO dimer formation on catalysts with high (above 2 wt. %) silver concentration and a parallel mechanism with isocyanates involved on catalysts with low (below 2 wt. %) silver concentration. It was demonstrated that on catalysts with high silver concentration mechanism that involves stepwise NO reduction via N2O to N2 is realised. Moreover, the final stage is complicated by the fact that formed intermediates and N2O are likely to desorb from the catalyst surface. In the case of catalysts with low silver concentration, the formation of both products (N2O and N2) proceeds in parallel and the lower activation barriers of the reaction leading to N2, as well as the thermodynamic profitability of its formation, lead to the predominance of the target product. The competition between the proposed mechanisms was studied in the case of catalytic centers represented by silver dimers. It was shown that activation barriers of reaction proceeding via NO dimer formation are lower than the corresponding barriers of the reaction with isocyanates involved, which confirms the prevalent realisation of the first process and the predominance of N2O among the final products. The obtained results explain the experimental data and are significant for further modelling of the mechanism of nitrogen oxides catalytic reduction considering the Al2O3 support.

Synthesis of benzotriazole-intercalated dispersions of molybdenum, tungsten and vanadium oxides for tribochemical applications

The effect of dispersed particles of lamellar molybdenum, tungsten and vanadium oxides on the lubrication properties of mineral oil was investigated. It is shown that in the presence of particles of hexagonal molybdenum oxide the coefficient of friction falls two-fold (from 0.08 to 0.04) exhibiting further decrease under high mechanical load, i. e. molybdenum oxide behaves as an adaptive lubricant. The intercalation of benzotriazole into molybdenum oxide ensures additional reduction of mechanical wearing due to suppressing the tribocorrosion.

Sampling and concentration of polycyclic aromatic hydrocarbons from exhaust gases from a plant for synthesis of carbon nanomaterials

Currently, there is an increase in the production of carbon nanomaterials in the world, which is associated with their unique physical and mechanical properties and their use in various fields of science, industry and technology. Investigation of the chemical composition of waste gases from a propane-butane mixture pyrolysis unit during the synthesis of carbon nanomaterials is of scientific and applied value, since it allows one to study both the chemistry of the pyrolysis process of hydrocarbon mixtures and determine the degree of toxicity of waste gas from pyrolysis units. The quantitative determination of polycyclic aromatic hydrocarbons in the gaseous products of pyrolysis of a propane-butane mixture during the synthesis of carbon nanomaterials has shown that when sampling with a small amount of the Supelpak-2 adsorbent, which is widely used in international and domestic methods, efficient capture of multinuclear aromatic hydrocarbons is not ensured. Therefore, an important research issue is the development of a simple and effective method for sampling polycyclic aromatic hydrocarbons with their subsequent GC-MS analysis. The principal essence of the technique is the impregnation of two fiberglass filters with an organic low-volatile solvent – diethylene glycol, tetraethylene glycol or dimethyl sulfoxide. The latter is characterised by the highest extracting power in relation to polycyclic aromatic hydrocarbons. The developed technique makes it possible to increase the efficiency of capturing multinuclear aromatic hydrocarbons (with four or more rings in a molecule) to 96–98 % compared to a solid adsorbent under equal conditions (pyrolysis conditions, weight of adsorbent equal with filters impregnated with a solvent), where the degree of their extraction is 1–5 %. The established values of the degree of recovery of the measured components are explained by the high extracting ability of dimethyl sulfoxide in relation to multinuclear aromatic hydrocarbons.

Interaction of nitrobenzoxadiazole derivatives of piperazine and aniline with bovine serum albumine in silico and in vitro

Albumin is a globular protein of plasma of mammalian blood participating in transport of hydrophobic metabolites and drugs. Thus, studies devoted to its binding are valuable as a part of evaluation of new potential drugs or fluorescent probes for in vivo usage. Here we describe results concerning synthesis and bovine serum albumin binding assay both in silico (docking) and in vitro (spectrophotometric and spectrofluorimetric titrations) for four new 7-nitrobenzoxadiazol-4-yl (NBD) derivatives of aniline and piperazine. Experimental dissociation constant for NBD-ethynylaniline 4 was calculated to be about 10 µmol/L.

Preparation and study of thermostable composites based on solid magnesium phosphate and calcium phosphate binders

Thermostable composite materials based on solid magnesium phosphate and calcium phosphate, as well as hybrid calcium magnesium phosphate binders have been developed and investigated. Thermal and phase transformations of the phosphate composites have been studied. Strength characteristics of composite materials have been determined in the temperature range of 20–1000 °C. It is shown that the obtained phosphate composites have high strength properties (compressive strength reaches 120–130 MPa) and are characterised by high thermal stability in the temperature range up to 1000 °С. The low weight loss of the studied composites (no more than 10 %) and the absence of significant thermal effects indicate that they are promising for use as a thermostable matrix for obtaining functional composite materials.

Thin composite polymethyl methacrylate films with silicon dioxide nanoparticles

Techniques for the formation of thin polymer films based on polymethyl methacrylate and composite coatings with silicon dioxide nanoparticles on glass and silicon substrates have been optimised, and their structural characteristics have been studied by atomic force microscopy. The effect of the introduction of silicon dioxide nanoparticles and their content on the structure and wettability of the formed composite coatings is described. Experimental data are presented which prove that the incorporation of SiO2 nanoparticles into the structure of the polymethyl methacrylate polymer matrix leads to changes in the roughness parameters of the coatings.

Re-emitting oxide – copper iodide(I) films for silicone solar cells

The effect of Al2O3 – CuI oxide films on the photoelectric parameters of silicon solar cells (SCs) has been studied. The largest increase in the external quantum efficiency of photoelectric conversion of SCs in the near UV range is observed for monolayer films of the 50Al2O3 – 50CuI composition, heat-treated at 280 °C for 30 min, which corresponds to a relative increase in the photocurrent upon exposure to radiation of spectral composition AM1.5 (1000 W/m2 ) by more than 35 %. This confirms the efficiency of using re-emitting Al2O3 – CuI films to increase the efficiency of silicon SCs.

Preparation procedure to obtain iron nanopowder under non-isothermal conditions

The kinetics for the procedure of preparing iron nanopowder from α-FeOOH by hydrogen reduction under non-isothermal conditions were studied. The reduction of α-FeOOH nanopowder was shown to occur within the temperature range from 180 to 550 °С, with a maximum specific rate value attained at 500 °С. The activation energy for the reduction process α-FeOOH nanopowder was measured to be ~43 kJ/mol, evidencing a mixed reaction mode. Performing the reduction of α-FeOOH at 500 °С accelerated the process while ensuring the required properties of the product obtained. The Fe nanoparticles thus prepared were of rounded shape, the size ranging from 70 to 100 nm.

Dynamics of cavitation zone development during sonication of suspensions of magnesium particles

The cavitation activity during ultrasonic treatment of magnesium particles has been investigated. The cavitation activity recorded in a continuous mode of ultrasonic treatment altered in a wide range at constant output parameters of the generator. The rate and nature of cavitation activity variation depended on the mass fraction of particles in the suspension. It has been demonstrated that during the ultrasonic treatment of magnesium aqueous suspensions it is possible to determine the following stages: growth of cavitation activity, reaching a maximum followed by a decrease and reaching a plateau (or repeated cycles of increasing or decreasing cavitation activity). The complex nature of the cavitation activity dynamics is associated with the participation of hydrogen released as a result of the chemical interaction of magnesium particles with water in the formation of the cavitation zone. The magnesium particles modified with ultrasound were characterised with the use of scanning electron microscopy, X-ray phase analysis and thermal analysis. It has been found that ultrasonic treatment of magnesium particles resulted in the formation of magnesium hydroxide and magnesium hydride phases.