Vol 59, No 10 (2023)

In this paper, we discuss general trends in the IR luminescence of colloidal PbS quantum dots 3 nm in average size, capped with thioglycolic acid molecules (PbS/TGA QDs). Treatment of the PbS/TGA QDs with a KI solution has been shown to cause a shift of a composite luminescence band peaking at 1120 nm to shorter wavelengths, to 1060 nm; an increase in the quantum yield of its shorter wavelength component, related to excitonic emission, from 1 to 10%; and quenching of its longer wavelength component, due to radiative recombination at defect levels. In this process, the cubic structure of PbS undergoes no changes. The average size of the PbS/TGA QDs has been shown to decrease slightly, by 0.2–0.3 nm. The conclusion has been drawn that the increase in the quantum yield of excitonic emission from the PbS/TGA QDs as a result of KI treatment is due to the more efficient passivation of interfacial defects, which act as both recombination luminescence and nonradiative carrier recombination channels. Using thermoluminescence in the temperature range from 80 to 350 K, we have demonstrated the presence of two types of shallow localized states, at 0.17- and 0.25-eV depths, whose density is only slightly sensitive to treatment of the PbS/TGA QDs with a KI solution. We assume that some of the traps identified are due to native defects in the nanocrystals—interstitial lead and sulfur ions—rather than to dangling bonds of surface lead and sulfur atoms.

In this paper, we report the synthesis of crystalline ruthenium ditelluride (RuTe2) and its thermodynamic properties in the range from 10 to 965 K, evaluated from its isobaric heat capacity Cp determined using calorimetry. At low temperatures, between 6.86 and 335.11 K, the heat capacity of the synthesized material—pure, free of impurities and foreign phases—was determined by adiabatic calorimetry. In the range 315.3–965.3 K, Cp was determined by differential scanning calorimetry. The data obtained above 298 K have been used to determine empirical coefficients of the Maier–Kelley and Khodakovsky equations. In the range 10–965 K, we have evaluated the standard thermodynamic functions: heat capacity, entropy, enthalpy increment, and reduced Gibbs energy. At 298.15 K, we have obtained 
 = 72.43 ± 0.14 J/(K mol), S° = 94.94 ± 0.19 J/(K mol), Н°(298.15 K) − Н°(0) = 14.60 ± 0.03 kJ/mol, and Ф° = 45.97 ± 0.09 J/(K mol). Using the absolute entropy determined by us and data in the literature and handbooks, we have estimated the standard Gibbs energy of formation of RuTe2: ΔfG°(RuTe2, cr, 298.15) = −130.5 ± 2.9 kJ/mol.

We have studied the effect of the composition of starting Mg1 – хNiх(OH)2 nanoplates on the formation of (Mg1 – хNiх)3Si2O5(OH)4 nanoscrolls under hydrothermal conditions and determined the structure, morphology, size parameters, and specific surface area of the synthesized nanopowders based on (Mg1 – хNiх)3Si2O5(OH)4 hydrosilicates with the chrysotile structure. The thermodynamically driven dehydration of the starting (Mg1 – хNiх)(OH)2 hydroxide with х ≳ 0.4 during hydrothermal treatment of a mixture of magnesium nickel hydroxide nanoplates and silica gel (SiO2∙nH2O) particles dispersed in an aqueous sodium hydroxide solution has been shown to play a key role in determining the formation and structural characteristics of (Mg1 – хNiх)3Si2O5(OH)4 nanopowders with tubular structure.

A ternary molybdate with the composition KBаLu(MoO4)3 and a monoclinic scheelite-like structure has been synthesized. Codoping KBаLu(MoO4)3 with Er3+/Yb3+ ions, we have obtained an upconversion phosphor exhibiting anti-Stokes luminescence in the range 400–700 nm under IR excitation. The synthesized phosphor has been characterized by X-ray diffraction, differential thermal analysis, and vibrational spectroscopy, and its IR, Raman, and luminescence spectra have been measured.

In this paper, we report a theoretical study of the electronic structure of copper oxides. The band structure of the copper oxides Cu2O and CuO has been calculated in the density functional approach by the full-potential linearized augmented plane wave method, using the modified Becke–Johnson (mBJ) potential. The results demonstrate that the use of the modified Becke–Johnson potential ensures better agreement of band structure calculation results for the copper oxides with experimental data then does the generalized gradient approximation (GGA). The use of the mBJ potential allows both compounds to be described as semiconductors whose band structure parameters are in qualitative agreement with experimental data. We have calculated copper L3-edge and oxygen K-edge X-ray absorption near edge structure spectra of Cu2O and CuO at different occupancies of the core level from which an electron transition occurs and compared the calculation results with experimental data.

Organomineral sorbents have been prepared by “mild” mechanical activation of air-dry clinoptilolite rocks with synthetic polymer (polyacrylamide) additions in an IVCh-3 laboratory-scale vibratory attritor (shear impact treatment for 3 min; specific mechanical energy delivered to the material, 2.16 kJ/g). The materials were characterized by scanning electron microscopy, infrared spectroscopy, differential scanning calorimetry, thermogravimetry, X-ray powder diffraction, and low-temperature nitrogen adsorption–desorption measurements. We have determined their specific surface area, specific pore volume, pore diameter, loose bulk and true densities, hygroscopic humidity, and oil sorption capacity. Modification of clinoptilolite rocks with 5 and 10 wt % polyacrylamide has been found to reduce the oil sorption capacity of the zeolites by 6–18%. The oil sorption capacity of the material modified with 20 wt % polyacrylamide was essentially the same as that of mechanically activated polymer-free clinoptilolite rocks.

Titanium nickelide alloys have been prepared by pressure-assisted electrothermal explosion (ETE) synthesis. We have examined the effect of Joule heating power on ETE parameters and the physicomechanical properties of the synthesized alloys. The results demonstrate that raising the electrical voltage applied to the starting mixture leads to a decrease in ignition time and increase in the maximum ETE temperature. The ignition temperature was 350°C, independent of the Joule heating power. X-ray diffraction characterization showed that the major phase in the alloys was NiTi. According to uniaxial compression test results, the compressive strength of the alloys is 1980 MPa. Their microhardness HV is 6.4 ± 0.8 GPa. Instrumental indentation has been used to determine their hardness under load (HM = 9.4 GPa) and characteristics of their plastic and elastic deformation. The synthesized alloys have been shown to have high plasticity.