Theoretical and Experimental Chemistry最新文献

A number of CsPbBr₃/h-BN nanocomposites with different contents of inorganic halide perovskite (IHP) nanoparticles, which are characterized by bright photoluminescence (PL) in the green region of the spectrum, were obtained by mechanochemical synthesis. It is shown that the use of a mechanochemical approach leads to a significant delamination of boron nitride (both at the stage of preliminary grinding of h-BN with cesium bromide and in the process of mechanochemical production of nanocomposites), the degree of which decreases in the range of CsBr/h-BN = 1:10 > 1 :50 > 1:100 > 1:250. The increase in the content of boron nitride in the reaction mixture during the mechanochemical synthesis of CsPbBr₃/h-BN nanocomposite contributes to a reduction of the size of the formed perovskite nanoparticles leading to a significant increase in the PL intensity (I_PL). Optimal content of IHP in the synthesized nanocomposites (~25 wt.%) for obtaining the material with the highest PL intensity has been estimated from the extreme dependence between the I_PL value of CsPbBr₃/h-BN nanocomposites and their CsPbBr₃ content.

Modified nickel composites based on stabilized zirconia as prototypes of anode materials of solid oxide fuel cells (SOFC) showed high catalytic activity and stability in the oxidative reforming of alkanes (tri-reforming of methane and steam-(oxygen) reforming of butane). Modification of Ni-10Sc1CeSZ composite with Cu and CeO₂ increases its resistance to carbonization, and doping with platinum or palladium (0.1 wt.%) increases the resistance to H₂S poisoning. Structured Ni-(CeO₂, La₂O₃)-Al₂O₃/cordierite catalysts are characterized by high activity and stability in the oxidative reforming of C₁-C₃ alkanes into syngas and can be effective in an external processor integrated with SOFC. Bench tests of the fuel cell showed the achievement of acceptable electrical characteristics.

On the basis of quantum-chemical analysis, it has been shown that the formation of silicon carbide nanoclusters can occur due to the chemical reaction between two CH₃SiCl₃ molecules on the first step of the process with the subsequent reaction between CH₃SiCl₃ and the formed clusters, rather than due to the homolytic C–Si bond rupture in the CH₃SiCl₃ molecule. Cases where a chlorine atom of a CH₃SiCl₃ molecule interacts with one hydrogen atom of another CH₃SiCl₃ molecule or cluster, and three chlorine atoms of a methyltrichlorosilane molecule form a three-center complex with three hydrogen atoms of a cluster have been considered. It is shown that the second case leads to the formation of SiC nanoparticles.

The current research on clusteroluminescence of nonconventional luminescent materials, which is associated with the occurrence of through-space conjugation due to the overlapping of electronic orbitals of atoms in aggregates formed at high concentrations of substances in solutions or solid states, is considered. It is shown that this phenomenon is typical for a wide range of substances, in particular, various low molecular weight organic compounds, polymers containing heteroatoms, inorganic substances and some hybrid (composite) materials. The possible practical use of clusteroluminogens in versatile fields is demonstrated, especially ecosystem monitoring, encryption materials, optoelectronics, medical and biological applications.

For the first time, the possibility of a CsPbBr₃/h-BN nanocomposite preparing by a mechanochemical treatment of a dry mixture of PbBr₂ and a hexagonal boron nitride delaminated with cesium bromide has been demonstrated. X-ray diffraction and electron microscopy studies show that the use of this method leads to the formation of crystalline CsPbBr₃ nanosheets. Unlike to the mechanochemically synthesized individual CsPbBr₃, the CsPbBr₃/h-BN nanocomposite is characterized by bright green luminescence. The nanocomposite has enhanced resistance to air moisture and sunlight due to the presence of a hydrophobic thermally conductive layers of boron nitride.

The study of catalytic properties of calix[4]arene with choline groups has shown a significant increase in the initial rate of a hydrolysis reaction of 4-nitrophenyl acetate and 4-nitrophenyl palmitate in aqueous borate buffer solutions. The acceleration for 4-nitrophenol ester reaches 200 times and exceeds the effect of cationic surfactants cetyltrimethylammonium bromide and N-cetylpyridinium chloride more than an order of magnitude. The structure of calixarene aggregates in solutions and the nature of their influence on the rate of hydrolysis reactions have been analyzed.

NiO-Al₂O₃ and Co₃O₄ oxide catalysts modified with palladium and oxides of rare earth metals (Ce and La) and formed on structured cordierite supports have been studied in the process of methane oxidation at different O₂/CH₄ ratios. It is shown that methane oxidation proceeds without the formation of CO even at an O₂/CH₄ ratio of < 2 (in contrast to nickel-containing catalysts) in the presence of cobalt-containing catalysts modified with cerium and lanthanum oxides. The addition of CeO₂ promotes Co₃O₄ dispersion, increases the number of oxygen vacancies, and prevents agglomeration of the active phase of the catalyst at high temperatures. The modification of Co₃O₄-CeO₂/cordierite with palladium (0.1%) enhances its activity due to increased surface oxygen mobility as a result of the interphase interaction of palladium with cobalt oxides and ceria (according to the TPR-H₂ and XPS data).

A critical review of the last decade’s literature on the synthesis, modification, and properties of layered double hydroxides (LDHs) regarding their use as sorbents for the removal of radionuclides from aquatic environments has been conducted. The evaluation of their adsorption capacity against U(VI), ¹³⁷Cs, ⁹⁰Sr, ⁶⁰Co, ^152+154Eu(III), and ²⁴¹Am has been performed on the basis of the analysis of the effect of the LDH preparation method, the nature of the metal ions in the material layers and compounds intercalated into their interlayer space. It is shown that magnetic composites of LDHs chelated forms have significant advantages for a practical use for the removal of both cationic and, especially, anionic forms of uranium(VI) from aquatic environments. Zn,Al-LDHs intercalated with the inorganic compounds, namely hexacyanoferrate(II) anions and copper(II) hexacyanoferrate, are found to be the most effective for the sorption extraction of ¹³⁷Cs and ⁹⁰Sr radionuclides.

Catalytic properties of two series of Keggin-type heteropolycompounds, H_3–2xMn_xPMo₁₂O₄₀ and (NH₄)_3–2xMn_xPMo₁₂O₄₀ (x = 0.25-1.5), have been studied in the process of oxidation of cyclohexanone and/or cyclohexanol to adipic acid, using 30% hydrogen peroxide, in the absence of organic solvent. The main products and by-products have been identified by means of GC-MS analysis. The highest yields of adipic acid are found in the case of H_1.5Mn_0.75PMo₁₂O₄₀ and (NH₄)₂Mn_0.5PMo₁₂O₄₀ compounds.