Russian Journal of Inorganic Chemistry最新文献

The paper studies the synthesis process of nanosized tin dioxide obtained by a combination of direct chemical precipitation and hydrothermal treatment using tin(II) acetate as a precursor. A comparative analysis of the chemical composition, microstructure, and crystal structure of the samples obtained under different conditions is performed. Thus, the thermal behavior of the obtained powders in the temperature range of 25–1000°C was studied using synchronous thermal analysis (TGA/DSC), the set of functional groups in the powders was studied using IR spectroscopy, and X-ray powder diffraction was used to study the crystal structure of the powders and determine the size of the coherent scattering region. Using scanning electron microscopy and transmission electron microscopy, the effect of hydrothermal treatment on the size of primary particles and agglomerates formed on their basis is shown. It was found that during hydrothermal treatment, the primary particles enlarge from 2.2 ± 0.4 nm to 2.6 ± 0.6 nm, while the microstructure of the samples becomes more uniform and the size of the agglomerates decreases from 42 ± 12 nm to 40 ± 8 nm. The morphology of the films formed using the obtained nanopowders was studied using atomic force microscopy (AFM). Within the framework of AFM, Kelvin probe force microscopy (KPFM) was used to construct surface potential distribution maps, as well as to estimate the electron work function from the surface of the materials.

Ternary Ti–Sc–O thin films were prepared by atomic layer deposition (ALD) at 300°C via the alternation of reaction cycles with the TiCl₄ or Sc(MeCp)₃ precursor and H₂O as the co-reactant. Materials with [Sc]/([Ti] + [Sc]) = 13, 25, 44, 64, or 82% were prepared at various ratios between the alternating cycles. The films were characterized by spectroscopic and single-wavelength null ellipsometry, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction. Film growth occurred within the temperature window of ALD and was substrate-inhibited. The dominant oxidation states of the metals were Ti⁴⁺ and Sc³⁺. Low scandium concentrations (up to [Sc]/([Ti] + [Sc]) = 25%) suppressed film crystallization into anatase as opposed to what was observed for TiO₂ films. The materials formed in the range [Sc]/([Ti] + [Sc]) = 44–100% had cubic structures; as the scandium concentration increases, the structure changed from disordered fluorite Sc₄Ti₃O₁₂ to Sc₂O₃-base cubic solid solution. The refractive indices n(E), absorption coefficients k(E), and optical bandgaps were well fitted to the Tauc–Lorentz model with a sharp absorption edge. They varied between the respective parameters of TiO₂ and Sc₂O₃ depending on the composition, which is topical for applied problems in optics, photonics, solar energy, and photocatalysis.

Effects of the percentage and type of functional groups on the selectivity of modified poly(3-aminopropyl)silsesquioxanes (PSs) in silver(I) extraction from multicomponent aqueous solutions was studied. The sorbents were prepared by modifying poly(3-aminopropyl)silsesquioxane with sulfur-containing reagents in various temperature schedules in order to vary the ratio of monosubstituted to disubstituted thiourea groups as well as amino groups. The sorbent structure was determined by IR spectroscopy and elemental analysis. An increase in the percentage of monosubstituted thiourea groups (from 40 to 75%) in the sorbent structure was found to increase the silver(I) percent extraction and selectivity at in the range 1–4. A heating stage was added to help the formation of a larger number of monosubstituted groups. The recovery of accompanying metal (copper(II), calcium(II), and magnesium(II)) ions was minimal over a wide pH range. Our results will help the purposeful regulation of the sorption and selective properties of materials via varying the ratio of the surface functional groups of the sorbent.

A partial substitution of Zr⁴⁺ in silicophosphate Na₃Zr₂Si₂PO₁₂ by trivalent element has been studied. By the example of Fe³⁺-substituted NASICON, it has been shown that the resulting complex does not correspond to the generally accepted formula Na_{3 + y}({text{M}}_{y}^{{{text{III}}}})Zr_2 – ySi₂PO₁₂, where electroneutrality of obtained compound is reached due to charge compensation by additional Na⁺ ions. On the basis of X-ray powder diffraction data, scanning electron microscopy, and the Rietveld refinement of crystal lattice parameters, the formation of complexes Na₃({text{M}}_{y}^{{{text{III}}}})Zr_2 – ySi_2 – yP_1 + yO₁₂ has been found. Precursor of composition Na_3 + y({text{M}}_{y}^{{{text{III}}}})Zr_2 – ySi₂PO₁₂ is excessive toward Na and Si for Fe-substituted complex. Elements that proved to be super-stoichiometric for the new crystal lattice are partially inserted in the main NASICON phase thus increasing unit cell parameters and are partially involved in the formation of additional phases (amorphous or crystalline). Amorphous phase is formed at the grain boundaries of low doped materials. Admixture crystalline phases appear in high doped samples.

The study aims at comparing the properties of magnetically recoverable Ag/FeO_x catalysts synthesized by different methods (impregnation, coprecipitation, and impregnation of a pre-reduced support) and at testing their activity in 4-nitrophenol reduction in an aqueous solution at room temperature. The most active catalysts in 4-nitrophenol reduction are the samples obtained by impregnation with Ag precursors (AgNO₃ and [Ag(NH₃)₂]NO₃) of the γ-Fe₂O₃ support (k = 2.19 min^–1) and the iron oxide support pre-reduced in an H₂/Ar flow at 250°C (k = 3.21 min^–1). This is due to the in situ formation of dispersed and active Ag particles from the cationic silver precursor under the action of the reducing agent NaBH₄. The nature of the Ag precursors (Ag⁺ or ({text{Ag}}left( {{text{N}}{{{text{H}}}_{{text{3}}}}} right)_{2}^{ + })) affects the activity of Ag particles. Catalysts in which the ammonia complex ({text{Ag}}left( {{text{N}}{{{text{H}}}_{{text{3}}}}} right)_{2}^{ + }) was the silver precursor exhibit lower activity compared to samples in which AgNO₃ was used. Differences in the thermodynamics and kinetics of the Ag⁺ or ({text{Ag}}left( {{text{N}}{{{text{H}}}_{{text{3}}}}} right)_{2}^{ + }) reduction to Ag⁰ determine the morphology and dispersion of the metallic silver particles, which affects the activity of the resulting catalysts. The presence of magnetic properties of the catalyst samples is shown by exposing them to an external magnetic field.

Titanium dioxide nanotube photoanodes were fabricated by anodizing titanium foil at 60 V in an ethylene glycol-based electrolyte using a two-step scheme. This process included intermediate removal of the amorphous coating followed by annealing at a temperature of 450°C. The nanotubes consist of titanium dioxide in the anatase form and have a length of 20–22 μm, an average diameter of 90–100 nm, and a wall thickness of 20 nm. The activity of this photoanode was studied in the photoelectrochemical oxidation reaction of ibuprofen (IBP), both in its molecular form and its ionic form as the potassium salt of 2-(4-isobutylphenyl)propionic acid (2-(4-IBP)K). Regardless of the form of IBP, its photoelectrocatalytic oxidation on the titanium dioxide nanotubes proceeds via the intermediate formation of oxygenated forms of IBP. The results from intensity-modulated photocurrent spectroscopy (IMPS) show that the addition of IBP to a saline solution (physiological saline) suppresses the recombination of electron-hole pairs due to an increased charge transfer rate to IBP. The stable operation of the TNT/Ti photoanode during prolonged photoelectro-oxidation of IBP was demonstrated.

Two novel bis-cyclometalated iridium(III) complexes with 1,2‑diphenylbenzimidazole (pbi) and ancillary 1-methyl-2-(pyridin-2-yl)-1H-perimidine (L₁, complex 1) or ethyl 2-(2-(pyridin-2-yl)-1H-perimidin-1-yl)acetate (L₂, complex 2) were synthesized and characterized by physicochemical methods. Comparison of the results of crystal packing analysis and electronic absorption spectroscopy demonstrates that while exclusion of the rigid pyrimidine system from conjugation does not allow red-shifting of absorption maxima, both complexes exhibit broad absorption up to 600 nm (ε = 27 000–800 M ^–1 cm ^–1), comparable to iridium analogs. The results of the study clarify the influence of steric factors on the absorption properties of the complexes and will be used for further development of strongly light-absorbing materials.

A critical review of studies on attempts to synthesize FeF₄ molecules and mass spectrometric investigations of the proposed reaction equilibria involving them does not provide a definitive answer regarding the existence of this compound. However, when combined with the results of infrared spectroscopy studies in noble gas matrices and quantum-mechanical calculations, reliable values for the bond dissociation energy (D_{0}^{ circ })(FeF₃ – F) = 195 ± 10 kJ/mol and the standard enthalpy of formation of gaseous iron(IV) fluoride Δ_fH°(FeF₄, 0) = –843 ± 10 kJ/mol can be recommended. A comparison with the thermodynamic characteristics of similar tetrafluorides is provided.

The heat capacity of β-pyrochlore CsTeMoO₆ and CsV_0.625Te_1.375O₆ complex oxide was investigated by adiabatic vacuum calorimetry and differential scanning calorimetry in the temperature range T = 5–500 K. The standard thermodynamic functions (heat capacity (C_{{text{p}}}^{ circ }), enthalpy [H°(T) − H°(0)], absolute entropy [S°(T)], and Gibbs free energy [G°(T) − H°(0)] were calculated for the range from T → 0 to 500 K based on the obtained experimental data. The low-temperature (T < 50 K) heat capacity was analyzed in terms of the multifractal model, and the layered–chain structure topology of the studied compounds was established.

The compound Bi_1.3Yb_0.7O₃ was prepared by solid-phase reactions. The compound had a cubic structure, space group Fm3m, with the unit cell parameter a = 0.54202 nm. The solution enthalpy of Bi_1.3Yb_0.7O₃ as measured by solution calorimetry in 2 M HCl was Δ_solH ⁰ = −227.8 ± 6.3 kJ/mol. The measured enthalpy of solution was used to calculate the standard enthalpy of Bi_1.3Yb_0.7O₃ formation as Δ_fH ⁰ = −996.0 ± 7.9 kJ/mol. The lattice enthalpy for Bi_1.3Yb_0.7O₃ was calculated using the Born–Haber cycle as Δ_latH ⁰ = −13278 kJ/mol.