Poly(vinyl alcohol) is one of the commonly used polymeric matrices for the fabrication of photocatalysts due to its ability to form hybrid photocatalysts with titanium compounds. However, it has several limitations, including low strength and solubility in aqueous media. In the present work, poly(vinyl alcohol) was modified with the cross-linking agent TiOSO4 to form a photocatalyst for Cr(VI) reduction, followed by Cr(III) precipitation. The photocatalyst was well characterized using SEM, IR, UPS, and XPS to describe its structure and the photoreduction mechanism that occurs due to the reversible transition between Ti(IV) and Ti(III) in the polymeric matrix. The formation of new Ti(III) states significantly increases light absorption, which is why the photocatalyst can be used for flow-mode water treatment. The photocatalytic flow plane reactor for Cr(VI) photoreduction was tested at different Cr(VI) concentrations from 5 to 400 mgL-1, at different wavelengths of 350, 400, and 500 nm, and in the pH range from 0.5 to 9.0. The Cr(III) solution obtained after photoreduction was used for pigment preparation. This work demonstrates the potential of the new photocatalyst for the efficient photoreduction of Cr(VI) in a flow-mode in-plane photoreactor.

Finding new, effective photocatalysts for the degradation of organic pollutants is a pressing issue in water treatment. Oxide photocatalysts are difficult to synthesize and impractical to use because they are most effective in the form of suspensions, sols, or nanoscale powders. This article demonstrates the photocatalytic ability of a hybrid polyvinyl alcohol-titanyl film photocatalyst to degrade Rhodamine B and formaldehyde. This hybrid material is an easily synthesized alternative to oxide photocatalysts that can be used to photodegrade organic pollutants. 99.8 % of Rhodamine B is degraded in 90 min with a catalyst-to-solution ratio of 1:100 for a 0.05 mM Rhodamine B solution. The film photocatalyst is transparent and colorless, with a band gap of 3.39 eV and an adsorption edge at 354 nm, corresponding to a forbidden direct transition. After irradiation, the photocatalyst's color changed to blue, and new photodegradation activity peaks were registered at 400 and 500 nm. The reversible color change of the photocatalyst enhances light absorption and promotes the effective separation of electron-hole pairs. Based on data from the Scavenger study and TOC measurements, a mechanism for the photodegradation of Rhodamine B on a hybrid polyvinyl alcohol-titanyl photocatalyst was proposed. The structure of the hybrid photocatalyst was characterized using XPS and IR spectroscopy, and the distribution of titanium in polymeric matrix was analyzed by SEM combined with EDX. This work demonstrates the potential of the synthesized polyvinyl alcohol-titanyl hybrid photocatalyst for the efficient photodegradation of organic pollutants.

Currently, a substantial amount of research is related to high-entropy alloys (HEAs) based on refractory metals (Hf, Ta, Mo, Nb, V, W, Cr, Zr, Ti). The inclusion of refractory elements contributes to an increase in the melting point (Tm) of the alloy and, thus, makes it a potential candidate for use at high temperatures, along with existing superalloys. One of the promising technologies for improving the characteristics of HEAs is plasma activation (modification) of the surface, as a result of which the resistance to fatigue deformation and abrasion increases, hardness, tensile strength and corrosion resistance increase. When studying complex multifunctional structures, it is necessary to conduct preliminary thermodynamic studies that have predictive potential for various properties of materials, as well as significantly reduce the amount of experimental research and, thereby, reduce time and material costs. In this work, thermodynamic modeling of the behavior of a high–entropy NbTaMoW alloy of equimolar composition under conditions of a low-temperature argon plasma is carried out: the temperature range is 300–10 000 K, the total pressure is P = 105 Pa. The simulated system consists of a condensed phase (an ideal NbTaMoW solution) and a gas phase above it. The temperature dependences of the equilibrium composition of the condensed and gaseous phases formed by heating this alloy with an argon plasma stream, as well as the thermodynamic characteristics (enthalpy, entropy, and Gibbs energy) of the simulated system are calculated. It is shown that the temperature dependences of the thermodynamic characteristics are not monotonous, but have kinks due to phase transformations that occur during equilibrium heating.

Composites based on melamine and titanium dioxide at different initial ratios 4 : 1, 6 : 1, 8 : 1, and 10 : 1 were obtained by polymerization in air at a temperature of 550°C. The morphology of the samples was investigated, and the elemental mapping of the sample composition was carried out using scanning electron microscopy. It was found that the initial melamine particles have a size of more than 20 μm, and its polymerization leads to the formation of g-C3N4 layers up to 5 μm in size. TiO2 particles have an average size of 150 nm, and the resulting g-C3N4/TiO2 heterostructures consist of particles with a size of 20–30 nm, which form agglomerates of about 2 μm in size. It was shown that the specific surface area decreases from 67 to 41 m2/g with increasing melamine content in the initial mixture. A single-phase composition TiN0.24O1.88 was formed when the initial components were mixed at a ratio of 4 : 1. When the ratio of the initial melamine and titanium dioxide was increased to 8 : 1 and 10 : 1, a two-phase system was formed, which consisted of Ti0.72O2 in an amount from 12 to 13

NbC/NbTaC2 nanocomposite with unique porous structure was prepared by carbidization by using electrochemical transport reactions. The chemical and phase composition, character of porosity, morphology, and pore size distribution were studied by using mass spectrometry, XRD, HRTEM, SEM, EBSD, and BET methods. The effect of high-temperature annealing on the porosity was considered. The powder consisted of spherical nanoparticles with internal cavities. The nanocomposite contained pores of various sizes and types. The main size of pores was about 13 nm. The agreement of the results obtained by different methods also confirms the correctness of the approximations used to study the porosity by the N2 adsorption-desorption method. Synergetic effect of the precursors (including Ta) and preparation method on the development of unique mesopores plays a crucial role. Such type of porosity allows filling the nanocomposite with additional particles or molecules of various sizes. This paper proposes a convenient route to prepare unique porosity nanocomposites, which are capable to act as a matrix for introducing additional elements or gases, i.e. for synthesizing composites with new properties. Such nanocomposites can also act as an electrocatalyst and accumulator for gas storage.

In this work, nanosized titanium dioxide was synthesized and the effect of acidity of the medium on its structure and properties was studied. Photocatalysts were prepared by a sol–gel method from titanium tetrabutoxide, ethyl alcohol, and water in a ratio of 1 : 1 : 4 at different pH (3, 7, and 9). Powder modification was carried out by annealing in air at 150–750°C. The structure of the synthesized initial and modified annealed photocatalysts was studied by XRD analysis and the phase ratios were determined. An analysis of the experimental data showed that the acidity of the medium did not have a strong influence on the phase formation and phase ratio of the resulting photocatalysts. It was found that the annealing temperature had a greater effect on the structure and properties: the phase ratio, coherent scattering regions (CSR), and specific surface area were changed. The powders prepared in this work had high specific surface area and complicated phase composition, which made them promising for photocatalysis, in particular, in a hydrogen evolution reaction.

Over the last decades, significant progress in the development of methods for obtaining and applying quantum dots (QDs) in various fields of biology, medicine and technology has been made. As a result, a detailed study of their toxic effect on living organisms and cells is becoming crucial. Physicochemical interaction takes place between the surface of biological component and surface of NPs. This "bio-nano" interaction depends on concentration, size, charge, shape of NPs and cells culture properties. In the present work, early cytopathic changes in fibroblast cells and HeLa cells were studied during conjugation with colloidal solutions of CdS QDs. To meet modern requirements of green chemistry, QDs were obtained by using a simple synthesis method, in an aqueous solution, without the use of high-temperature. To obtain trustworthy results, MTT test, NCR method and vital staining with trypan blue were used. The results of these methods were compared. All precursors of CdS QDs solutions affected the vital activity of cells, but the mechanisms of influence and early pathological changes in cells were different. It was shown that additional removing residues of unreacted precursors from solutions after synthesis reduce cytotoxicity index (IC) from moderate to low. Simultaneous use of several in vitro methods allows one to observe early pathological changes in cells before the onset of cytopathic effect (CPE) and to obtain the most complete information about possible CPE of new functional materials.

The electrochemical behavior of disordered systems, such as high-entropy alloys, is a stochastic random process. To accurately predict and analyze the behavior of such systems under operating conditions, it is necessary to use new computational and experimental methods along with classical electrochemical methods. Using equimolar rare-earth alloys GdTbDyHoSc and GdTbDyHoY as an example, we demonstrate the efficiency of using fast Fourier transform and wavelet analysis to estimate the electrochemical behavior of stochastic systems. The time series of potential fluctuations of alloy samples are measured in 0.01 M NaCl solution within 12 h at a current density of 0.2–0.5 mA/cm2. Fast Fourier transform analysis of the obtained time series shows that the slope of the logarithm of spectral power density to the logarithm of frequency increases with the current density. In particular, coefficient β changes from –1.93 to –1.77 for a GdTbDyHoY sample and from –1.46 to –1.35 for a GdTbDyHoSc sample. In addition, wavelet analysis is used to process the time series obtained for both alloys at current densities from 0.2 to 0.5 mA/cm2. To illustrate the intensity of the electrochemical dissolution of the alloy surface, we construct scalograms for the obtained time series. The scalograms are used to calculate the global energy spectra distributed over frequency ranges and the total energies of the systems under study. The GdTbDyHoY alloy exhibits higher total energies as compared to the GdTbDyHoSc alloy. The total energy for the GdTbDyHoY alloy increases from 0.97 to 2.03 kV2 when the current density increases from 0.2 to 0.5 mA/cm2. For the GdTbDyHoSc alloy, the total energy increases from 0.50 to 0.84 kV2. Fast Fourier transform and wavelet analysis are found to be effective tools for understanding the electrochemical behavior of locally disordered chemical systems, such as high-entropy GdTbDyHoSc and GdTbDyHoY alloys, in addition to classical electrochemical methods.

Machine learning interatomic potential for LiGe2(PO4)3 in a form of a set of neural networks (DeePMD-model) was trained on DFT data. DFT simulations in GGA PBE approximation were performed for ordered and disordered LiGe2(PO4)3 supercell with 432 atoms which allowed the developed potential to describe crystalline, molten and glassy states. The developed DeePMD-potential was verified using literature and our experimental data demonstrating good agreement with it. Neural network molecular dynamic simulations indicate that P atoms have tetrahedral oxygen environment in both crystalline and glassy state. Coordination environment of Ge atoms is more complex. They have octahedral oxygen environment in crystalline state and mixed environment in glassy state: 4-, 5- and 6-coordinated Ge atoms were found. It was shown by calculation of orientational order parameters that in glassy LiGe2(PO4)3 4-coordinated Ge atoms have tetrahedral oxygen environment, while 6-coordinated Ge atoms have octahedral oxygen environment. Analysis of O-Ge-O angle distribution for 5-coordinated Ge atoms in glassy LiGe2(PO4)3 demonstrates that the environment of Ge atoms in this case is represented by various structures: square pyramids, trigonal bipyramids and transitional structures from 5-coordinated Ge atoms to tetrahedrons.

High-entropy alloys attract researcher’s attention due to the presence of a set of new properties. The paper considers the factors affecting the structure of high-entropy alloys (HEAs) based on the elements Ti, Zr, Hf, V, and Nb. The structure data of four-component Ti25Zr25V25Nb25 and five-component Ti20Zr20Hf20V20Nb20 alloys, which were obtained under the same melting and cooling conditions in an arc furnace, are presented. The data of the EDX analysis showed that the chemical composition of the alloys corresponded to the nominal one. Analysis of micrographs of the ingots surface allows us to conclude that the applied melting mode led to overheating of the four–component alloy, but not for the five-component one. It was experimentally found that the primary formation of the four-component alloy occurs faster than that of the five-component one, but further remelting under overheating conditions leads to multiphase structure formation. The maximum content of BCC solid solution (98%) in Ti25Zr25V25Nb25 alloy was achieved during the first remelting, another phase was FCC solid solution (2%). The maximum content of BCC solid solution (95%) in Ti20Zr20Hf20V20Nb20 alloy was obtained by repeated remelting, BCC, HCP solid solutions, and the Laves phase were presented in the amount of 3% or less. The crystal lattice parameters of the BCC main phases for the Ti25Zr25V25Nb25 and Ti20Zr20Hf20V20Nb20 alloys were 3.270 and 3.362 Å, respectively. It was established that to obtain refractory HEAs with a single-phase structure it is important both fulfilment of thermodynamic conditions and correct choice of time-temperature conditions of melting and crystallization for each specific alloy composition.

Developing light yet strong aluminum (Al)-based alloys has been attracting unremitting efforts due to the soaring demand for energy-efficient structural materials. However, this endeavor is impeded by the limited solubility of other lighter components in Al. Here, we propose to surmount this challenge by converting multiple brittle phases into a ductile solid solution in Al-based complex concentrated alloys (CCA) by applying high pressure and temperature. We successfully develop a face-centered cubic single-phase Al-based CCA, Al55Mg35Li5Zn5, with a low density of 2.40 g/cm3 and a high specific yield strength of 344×103 N·m/kg (typically ~ 200×103 N·m/kg in conventional Al-based alloys). Our analysis reveals that formation of the single-phase CCA can be attributed to the decreased difference in atomic size and electronegativity between the solute elements and Al under high pressure, as well as the synergistic high entropy effect caused by high temperature and high pressure. The increase in strength originates mainly from high solid solution and nanoscale chemical fluctuations. Our findings could offer a viable route to explore lightweight single-phase CCAs in a vast composition-temperature-pressure space with enhanced mechanical properties. By overcoming the limited solubility of other lighter components in aluminum using high pressure and high temperature, a low-density, high specific strength, and single-phase aluminum-based complex concentrated alloy is developed.

Titanium dioxide synthesis and modification by chemical, electrochemical, and mechanochemical methods are briefly outlined. The atomistic structure, nanostructure, morphology, optical characteristics, functional properties, and peculiar features of the semiconductor material are described. Practical applications of titanium dioxide in catalysis, sorption, and biomedicine are described.

Quantum dots are the most exciting representatives of nanomaterials. They are synthesized using advanced methods of nanotechnology pertaining to both inorganic and organic chemistry. Quantum dots possess unique physical and chemical properties; therefore, they are used in very different fields of physics, chemistry, biology, engineering and medicine. It is not surprising that the Nobel Prize in chemistry in 2023 was given for discovery and synthesis of quantum dots. This review addresses modern methods for the synthesis of quantum dots and their optical properties and practical applications. In the beginning, a short insight into the history of quantum dots is given. Many gifted scientists, including chemists and physicists, were engaged in these studies. The synthesis of quantum dots in solid and liquid matrices is described in detail. Quantum dots are well-known owing to their unique optical properties; that is why the attention in the review is focused on the quantum-size effect. The causes for fascinating blinking of quantum dots and techniques for observation of a single quantum dot are considered. The last part of the review describes mportant applications of quantum dots in biology, medicine and quantum technologies. The bibliography includes 772 references.

Al-based foams have drawn increasing attention from industry due to their integration of structure and functional properties. However, large-sized Al-based foams still cannot be homogeneously strengthened by long-time aging due to their low thermal conductivity. In this study, we proposed an age-hardening approach that was applied in large-sized Al-0.16Sc-0.17Zr (wt.%) foams via micro-alloying with Zr and Ti compared with Al-0.21Sc foams; it not only achieved homogeneous strength by long-term aging but also reduced the cost of the alloy by substituting Zr and Ti for the more expensive Sc content. The results show that the Al3(Sc, Zr, Ti) phase with a core–shell structure as a crucial precipitation strengthening phase by micro-alloying with Zr and Ti was less prone to coarsening after a prolonged aging heat treatment. Therefore, the yielding strength of Al-Sc foam micro-alloying with Zr and Ti remained almost unchanged after a maximum aging time of 1440 h due to less coarsening precipitate, which is consistent with the results of mechanical experiments. These findings provide a new way for the heat treatment strengthening of large-sized Al-based foams, thus promoting their industrial applications.

Face-centered cubic (FCC) high-entropy alloys (HEAs) exhibit excellent fracture toughness and fatigue properties at both ambient and cryogenic temperatures. However, the relatively low strength of FCC HEAs at room temperature limits their widespread application. Herein, we present a novel approach to tailoring the microstructure of the Al0.1CoCrFeNi HEA and improving its room temperature tensile strength through multiaxial cryogenic forging (MACF) and low temperature annealing (LTA). After the treatments, the tensile strength increases from 687 MPa for the as-prepared fine-grained HEA to 1487 MPa for the MACF specimens annealed at 673 K for 48 h. Our analysis indicates that the strengthening mechanisms are twofold: the tensile strength increased by about 455 MPa after the MACF treatment, which is due to the synergistic effect of dislocations and nanotwins; after LTA, the tensile strength abnormally increased by about 345 MPa, which can be attributed to stacking faults, hexagonal close-packed, and 9R structures formed by thermal relaxation of nanotwin boundaries.

This article considers how the shape of the inner channel in the anode assembly affects plasma flow velocity in a plasma torch. Three different shapes of the anode assembly were analyzed, all with a conical confusor part of 50 mm in length: with a diameter transition from 12 to 6 mm, from 12 to 8 mm, and from 12 to 10 mm. A computer experiment was performed using the finite element method and then validated by the subsequent full-scale experiment on a laboratory plasma unit. The obtained results were verified. The verification outcomes showed a satisfactory convergence and were consistent with the published data. A review of the existing plasma unit designs for powder production, application of functional coatings, and surface modification was carried out. The software packages implementing the finite element method to solve these problems were examined. The study yielded practical recommendations for consumers and developers of plasma equipment and identified the shapes of the anode assembly enabling both supersonic and subsonic plasma flow regimes.

Short-range ordering (SRO) is one of the most important structural features of high entropy alloys (HEAs). However, the chemical and structural analyses of SROs are very difficult due to their small size, complexed compositions, and varied locations. Transmission electron microscopy (TEM) as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys. In this short communication, we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs. By using advanced TEM techniques, not only the existence of SROs was confirmed, but also the effect of SROs on the deformation mechanism was clarified. Moreover, the perspective related to application of TEM techniques in HEAs are also discussed.

Over the last decade, great attention of researchers has been focused on nanoscale self-assembly due to increasingly technology-relevant applications. Pattern formation by colloidal droplet evaporation is one of the fascinating subjects to study. A deep understanding of physical and chemical processes of the deposited structure formation allows the development of bioprinting methods, nanoarchitectures for optics and electronics, methods for detecting the state of peptides, proteins, etc. In the present work, the effect of organic ligands (MPS, BSA, GSH, EDTA, TG) on Ag2S NP self-assembly during solution droplet evaporation was investigated. The synthesis conditions were optimized to minimize or neglect the contribution of surface roughness, substrate thermal conductivity, NP shape and size, type of solvent. Properties of a stabilizer, such as molecular length, reactivity, tendency to polycondensate or chelate, and their relative concentration affect the nanoparticle–nanoparticle interactions, which results in several types of pattern formation. The dominant forces in different regions of the evaporated droplet via ligand were discussed. The models of pattern formation were proposed. Thus, depending on the ligand, Ag2S NPs tend to form rings (MPS, BSA), concentric rings (BSA), net like structures (TG), and chains (MPS, TG). In addition, it was shown that replacing water with deuterium can significantly change self-organized architectures.

Recent discoveries of low-dimensional and ultra-dispersed magnetocaloric materials revealed interesting results that help to uncover some fundamental aspects related to the magnetocaloric effect. One of the promising way to obtain ultra-fine metallic nanocomposites resistant to environmental conditions is the use alloy systems showing a liquid miscibility gap. Within this study we fabricate some monotectic composites containing YGdTbDyHo high-entropy alloy and examine their structure, microstructure, thermal conductivity, magnetic and magnetocaloric properties, employing X-ray diffraction, electron microscopy, magnetometry and ab initio molecular dynamics simulations. The results reveal that the use of chromium, vanadium and their mutual alloys as a host monotectic matrix in combination with standard arc-melting enables the YGdTbDyHo high-entropy alloy to be evenly dispersed in the form of small irregularly-shaped particles (droplets or lamellae) of less than 1–2 μm in size, practically uncontaminated with the host metal in which these inclusions are distributed. The monotectic composites have increased Neel points, but reduced magnetocaloric response compared to non-dispersed as-cast YGdTbDyHo alloy. The observed tendencies in the behavior of magnetic properties of the developed monotectic alloys turned out to be similar to the micron powders and thin films based on rare-earth metals studied to date, i.e. the effects of micro- and nanostructuring in all systems are of the same nature and play a decisive role in their magnetism. The study results allow us to conclude that using immiscible metals in alloy fabrication process is effectient for dispersing rare-earth high entropy alloys and opens up new prospects in designing low-dimensional and nanoscale magnetic phases with adjustable magnetocaloric properties.

The photocatalytic activity of the g-C3N4/TiO2 composite samples in the processes of dye (methylene blue) decomposition and hydrogen evolution from an aqueous ethanol solution under the action of visible radiation (400 nm) has been studied. A new original method for the synthesis of the g-C3N4/TiO2 composite by depositing g-C3N4/TiO2 to TiO2 nanoparticles during sol-gel synthesis is proposed. The synthesized photocatalysts were characterized by X-ray diffraction, low-temperature gas adsorption, X-ray photoelectron spectroscopy, high-resolution transmission microscopy, and diffuse reflectance spectroscopy in the UV and visible regions. The maximum activity in the hydrogen evolution reaction was 1.3 mmol g_cat^ - 1 h–1, which exceeds the rate of hydrogen evolution on the unmodified g-C3N4 and TiO2 samples.