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In this work, a two-step method for preparation of CZTSe (Cu2ZnSnSe4) single crystals was demonstrated for the first time by recrystallization of a polycrystalline material in a KI-KCl meltsolution in a temperature gradient. At the first step, a polycrystalline material consisting of a mixture of metal selenides was synthesized by direct fusion of elemental Cu, Zn, Sn, and Se at 1000°C. Next, recrystallization process was carried out at a temperature gradient of 100°C, while the temperature of the cold zone was 750°C. The phase and chemical composition of the crystals were studied by energy dispersive X-ray and Raman spectroscopy. It was shown that the charge composition does not affect the composition of the obtained crystals. According to the amount of the remaining charge in the hot zone, one can speak of a very low recrystallization rate and a low product yield. Analysis of the elemental composition of crystals from the cold zone revealed a high inhomogeneity even in one experiment, which indicates the need to optimize the experimental parameters. On the other hand, according to the full line width at half height of the main peak, it can be argued that the obtained samples have a high degree of order in the structure and are suitable for measuring of physical characteristics. [ABSTRACT FROM AUTHOR]

Bulk crystals of new huntite type borates were grown by TSSG method using eutectic LiBO2-LiF as a flux. Chemical composition, X-ray diffraction, optical absorption and fluorescence spectra of the grown samples were studied. [ABSTRACT FROM AUTHOR]

This study presents the temporal and spatial variability of U/U activity ratios in the Shu River and provides interpretation to explain the downstream changes of uranium and the U/U activity ratios in the study area. The positive linear correlation ( R = 0.98, p < 0.001) between uranium concentration and specific electrical conductance is consistent with rock weathering and leaching as the major contributor of dissolved uranium in the studied area of the river. The U/U activity ratio ranged between ~1.6 in the upper reaches of the river to ~1.15 furthest downstream. Activity ratios at specific sampling points do not show significant seasonal variability. [ABSTRACT FROM AUTHOR]

This study presents the results of the synthesis of silver chloride nanoparticles dispersed within ammonium nitrate matrix via displacement mechanochemical reaction NH4Cl + AgNO3 + zNH4NO3 = (z+1)NH4NO3 + AgCl at z = z1 = 7:22 and z = z2 = 3:64. The intermediate compound, NH4Ag(NO3)2, was identified after mechanochemical processing of studied system. Use of simultaneous thermogravimetry and differential scanning calorimetry provide a new means for preparing silver chloride nanoparticles in their free form by thermal treatment. [ABSTRACT FROM AUTHOR]

The data of studies on the effectiveness of impregnation with polysulfide solutions of shell limestone used as facing and wall material, as well as for the manufacture of road products are presented. Modification of the limestone with the impregnating composition «Akvastat» created by the authors which is sulfur-containing water-based solution of calcium polysulfide containing alcohols and surfactants, can significantly reduce water absorption and increase durability of limestone. Impregnating composition on the basis of calcium polysulfide possesses density of 1.22–1.24 g/cm3, the infiltrant penetrates into the pore structure of limestone to a depth of 4 cm or more, depending on the density and structure of the sample. While the material is drying, sulfur nanoparticles are crystallized from the polysulfide solution in its pores. They partially fill pore space and form protective durable insoluble hydrophobic coating that impedes the penetration of water into the pores of the limestone, but preserves its vapor permeability, which is important for wall and decoration materials. The evaluation of protective coatings was performed with laser particle size analyzer, scanning probe microscope and a diffractometer. It showed that the average size of the particles forming the protective coating is in the range of 20–25 nm, the particles shape is spherical, the particles are elemental sulfur with orthorhombic structure of the crystal lattice. The processing of shell limestone with calcium polysulphide solution provides formation of coating based on nanosized sulfur on the surface of stone pores. The coating partially fills the pore space and, as it is hydrophobic, reduces the water absorption of the samples by a factor of 5–8, increases their average density by 22–27%, strength in 1,2–1,3 times, the softening factor by 6–19%, that makes possible to predict the increase of the durability of building materials based on shell limestone to 1.5–2 times or more. Impregnation of the wall, facing and road construction materials and limestone products with polysulfide omposition «Akvastat» allows improving their operational properties, increasing resistance to weathering, expanding their area of application in the climatic conditions of Central Russia.

The results of research on hydrophobic impregnation of dense concrete with composition «Aquastat» designed for manufacture of road and airfield plates are presented. It was found that after having been treated with waterrepellent agent the concrete sample is resistant to wetting, i.e. it gets hydrophobic properties. At the same time the water absorption of the samples treated for 24 hours at atmospheric pressure is reduced in three times, and soaked for 0.5 hours under vacuum decreases 5.5 times. It was revealed that the hydrophobic properties of fine-grained concrete impregnated with «Aquastat» may be at the same level of those of dense concrete based on coarse filler. Substantially increased hydrophobic properties of dense concrete (more than 5 times) allow authors to forecast twice increased service life of road and airfield plates treated by «Aquastat» composition.

This study presents the results of the synthesis of silver chloride nanoparticles dispersed within ammonium nitrate matrix via displacement mechanochemical reaction NH4Cl + AgNO3 + zNH4NO3 = (z+1)NH4NO3 + AgCl at z = z1 = 7:22 and z = z2 = 3:64. The intermediate compound, NH4Ag(NO3)2, was identified after mechanochemical processing of studied system. Use of simultaneous thermogravimetry and differential scanning calorimetry provide a new means for preparing silver chloride nanoparticles in their free form by thermal treatment. [ABSTRACT FROM AUTHOR]

Ternary ZnS/ZnO/graphitic carbon nitride (gCN) photocatalysts were prepared by coupling gCN sheets with ZnO nanorods under solvothermal conditions followed by sulfurization using Na 2 S. SEM and TEM analyses show that small-sized ZnS particles (ca. 7.2 nm) deposit homogeneously on the surface of ZnO/gCN nanohybrids. Photoluminescence and electrochemical impedance spectroscopy show that ZnS allows for an enhanced charge separation efficiency as well as prolonged lifetime of photogenerated charge carriers, leading to improved hydrogen photoproduction under UV light irradiation compared to ZnO/gCN. Moreover, the deposition of ZnS nanoparticles improves the photostability of the ZnS/ZnO/gCN catalyst for hydrogen production. A double Z-scheme mechanism is proposed for hydrogen photoproduction using the ZnS/ZnO/gCN heterojunction.

This study demonstrates rapid photocatalytic oxidation of a benzene, toluene, ethylbenzene, and xylene (BTEX) mixture over TiO 2 /volcanic glass. The assessment of the photocatalytic oxidation of BTEX was conducted under conditions simulating those found in indoor environments affected by aromatic hydrocarbon release. We show, under UV-A intensities of 15 mW/cm 2 and an air flow rate of 55 m 3 /h, that low ppmv levels of BTEX concentrations can be reduced to below detectable levels. Solid-phase microextraction technique was employed to monitor the levels of BTEX in the test chamber throughout the photocatalytic oxidation, lasting approximately 21 h. Destruction of BTEX from the gas phase was observed in the following sequence: o -xylene, ethylbenzene, toluene, and benzene. This study identified sequential degradation of BTEX, in combination with the stringent regulatory level set for benzene, resulted in the air quality hazard indexes (Total Hazard Index and Hazard Quotient) remaining relatively high during the process of photocatalytic oxidation. In the practical application of photocatalytic purification, it is crucial to account for the slower oxidation kinetics of benzene. This is of particular importance due to not only its extremely low exposure limits, but also due to the classification of benzene as a Group 1 carcinogenic compound by the International Agency for Research on Cancer (IARC). Our study underscores the importance of taking regulatory considerations into account when using photocatalytic purification technology.

A review of the current literature shows there is no clear consensus regarding the reaction mechanisms of air-borne aromatic compounds such as toluene by photocatalytic oxidation. Potential oxidation reactions over TiO 2 or TiO 2 -based catalysts under ultraviolet and visible (UV/VIS) illumination are most commonly considered for removal of these pollutants. Along the pathways from a model pollutant, toluene, to final mineralization products (CO 2 and H 2 O), the formation of several intermediates via specific reactions include parallel oxidation reactions and formation of less-reactive intermediates on the TiO 2 surface. The latter may occupy active adsorption sites and causes drastic catalyst deactivation in some cases. Major hazardous gas-phase intermediates are benzene and formaldehyde, classified by the International Agency for Research on Cancer (IARC) as Group 1 carcinogenic compounds. Adsorbed intermediates leading to catalyst deactivation are benzaldehyde, benzoic acid, and cresols. The three most typical pathways of toluene photocatalytic oxidation are reviewed: methyl group oxidation, aromatic ring oxidation, and aromatic ring opening.

The Syr Darya is one of the major rivers supplying the Aral Sea with freshwater. Soviet programs aimed at maximizing agricultural productivity in the Syr Darya basin increased diversion of water drastically affecting its water quality with significant consequences to its suitability for irrigation, fisheries and other uses. While water quality standards for trace elements are typically measured in the dissolved phase, there is evidence that adsorbed phases may also be relevant. Here we report potentially available heavy metals and metalloid concentrations in the Syr Darya water through the treatment of unfiltered waters samples with dilute nitric acid. Significant differences were found for most studied elements (Mann-Whitney U Test, p < 0.05) between their dissolved and acid-leachable concentrations. For Sr and Se in both sampling campaigns, no significant differences were found between their dissolved and acid-leachable concentrations, indicating their low geochemical reactivity. Dissolved V concentrations and acid-leachable Ni and Zn were found to exceed Kazakhstan Maximum Permissible Concentrations (MPC) values for the protection of fishery water quality. Our study evaluates the importance of considering regulatory issues of measuring trace metal concentrations to assess the water suitability for fisheries and irrigation., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Bolat Uralbekov and Bagdat Satybaldiyev report financial support was provided by Committee of Science of the Ministry of Education and Science of the Republic of Kazakhstan., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

NaSrR(BO 3 ) 2 (R = Ho-Lu, Y, Sc) compounds were obtained for the first time. Their structures exhibit disordered positions of Sr 2+ and Na + atoms while RO 6 polyhedra are connected through the BO 3 groups. Large distances between R atoms and high transparency in the range of 250-900 nm make them promising for phosphor applications. A pathway to obtain single crystals was shown by growing NaSrY(BO 3 ) 2 and NaSrYb(BO 3 ) 2 by the top seeded solution growth method with Na 2 O-B 2 O 3 -NaF flux.

Doping of transition metals within a semiconductor quantum dot (QD) has a high impact on the optical and magnetic properties of the QD. In this study, we report the synthesis of Mn 2+ -doped Ag-In-Ga-Zn-S (Mn:AIGZS) QDs via thermolysis of a dithiocarbamate complex of Ag + , In 3+ , Ga 3+ , and Zn 2+ and of Mn(stearate) 2 in oleylamine. The influence of the Mn 2+ loading on the photoluminescence (PL) and magnetic properties of the dots are investigated. Mn:AIGZS QDs exhibit a diameter of ca. 2 nm, a high PL quantum yield (up to 41.3% for a 2.5% doping in Mn 2+ ), and robust photo- and colloidal stabilities. The optical properties of Mn:AIGZS QDs are preserved upon transfer into water using the glutathione tetramethylammonium ligand. At the same time, Mn:AIGZS QDs exhibit high relaxivity ( r 1 = 0.15 mM -1 s -1 and r 2 = 0.57 mM -1 s -1 at 298 K and 2.34 T), which shows their potential applicability for bimodal PL/magnetic resonance imaging (MRI) probes., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Photocatalysts composed of graphitic carbon nitride (g-CN) and TiO 2 were efficiently prepared by thermolysis of the MIL-125(Ti) metal organic framework deposited on g-CN. The heterojunction between the 12 nm-sized TiO 2 nanoparticles and g-CN was well established and the highest photocatalytic activity was observed for the g-CN/TiO 2 (3:1) material. The g-CN/TiO 2 (3:1) composite exhibits high visible light performances both for the degradation of pollutants like the Orange II dye or tetracycline but also for the production of hydrogen (hydrogen evolution rate (HER) up to 1330 μmolh -1 g -1 and apparent quantum yield of 0.22% using NiS as a cocatalyst). The improved visible light performances originate from the high specific surface area of the photocatalyst (86 m 2 g -1 ) and from the efficient charge carriers separation as demonstrated by photoluminescence, photocurrent measurements, and electrochemical impedance spectroscopy. The synthetic process developed in this work is based on the thermal decomposition of metal organic framework deposited on a graphitic material and holds huge promise for the preparation of porous heterostructured photocatalysts.

A facile two-step method was developed to prepare core/shell ZnO/rGO particles from ZIF-8/rGO composites. ZIF-8 particles were first grown at the surface of rGO sheets. Next, ZIF-8 particles were transformed into ZnO particles by thermal decomposition under air at 500 °C. All materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and Brunauer-Emmett-Teller analyses. Results obtained show that ZIF-8 particles strongly associate with rGO sheets and that the calcination of this material produces porous core/shell ZnO/rGO particles with an average diameter of ca. 40 nm. The wt % of rGO associated with ZIF-8 particles was varied from 5 to 20%. The ZnO/rGO (10%) particles exhibit the highest photocatalytic activity for the degradation of the Orange II dye under simulated solar light irradiation of weak intensity (5 mW/cm 2 ). This high photocatalytic activity was demonstrated to originate from superoxide O 2 •- radicals due to the efficient trapping of photogenerated electrons in ZnO by rGO., Competing Interests: The authors declare no competing financial interest.

The concentrations of (238)U, (234)U, (226)Ra, (210)Po and (210)Pb have been determined in surface waters collected along the course of the Shu River, lying on the border between Kazakhstan and Kyrgyzstan. In the study area, the river runs through some of the largest uranium deposits worldwide, which were actively exploited during the nuclear weapons and nuclear energy programmes of the former Soviet Union. The data show an increasing trend in uranium concentrations downstream the river from the city of Tokmak to the city of Shu, with good correlation between total uranium concentrations and total dissolved solids. Data on uranium isotopes disequilibrium show the presence of technogenic uranium inputs into the Shu River downstream from the city of Karasu, evidenced by a decrease in the measured (234)U/(238)U isotopic ratio from 1.63 in uncontaminated sites to 1.29 in sites affected by past mining activities.