Sergey K. Evstropiev

The paper presents the results of developing a photocatalytic generator of chemically active oxygen species intended for air disinfection and purification

BACKGROUND: Inhalation of technologically generated singlet oxygen is used empirically in fitness and sports medicine and is proposed for integration into clinical practice. However, the mechanisms of action and safety of this treatment remain unclear. AIM: The study aimed to evaluate the systemic effects of long-term exposure to an air mixture enriched with singlet oxygen in vivo. METHODS: The study was conducted on eight female Wistar rats (200–220 g) which were kept in a barrier animal facility. The experimental group (singlet oxygen, n = 4) received an air mixture enriched with singlet oxygen for free breathing three times a day for 40 minutes for 4 months in an individually ventilated cage via the SmartFlow ventilation system. A custom-built device employing a novel photocatalytic method was used to generate singlet oxygen. Intact rats (n = 4) were used as controls. Body weight, hematological parameters, plasma total antioxidant and pro-oxidant capacities, tissue malondialdehyde levels, and organ histology were evaluated. RESULTS: The singlet oxygen group showed no signs of general toxicity, such as hair loss, inflammation of visible mucous membranes, diarrhea, or behavioral stress. There were no weight differences between groups. An increase in hemoglobin concentrations was observed among the hematological parameters (p = 0.028). No differences were detected in plasma total antioxidant and pro-oxidant capacities. However, lipid peroxidation, as indicated by malondialdehyde levels in liver and kidney tissues, was significantly lower than the baseline values of the intact group (p = 0.043 and p = 0.029, respectively). No histopathological changes were observed in the nasal ciliated epithelium or the parenchyma of the lungs, liver, kidneys, heart, spleen, and thymus. CONCLUSION: The in vivo study demonstrated the safety of long-term inhalation of an air mixture containing singlet oxygen. In the absence of histological changes, trends in lipid peroxidation levels suggest that tissues and organs are adapting to breathing air enriched with singlet oxygen. These systemic changes may result from the pathophysiological mechanism of remote preconditioning.

Subject of study. 1,4-butanediol diglycidyl ether-based epoxy polymers and their multilayer glass composites were studied. Aim of study. The aim of this study was to obtain a new universal, homogeneous, and transparent epoxy composition with high adhesion to the surfaces of both organic and silicate glasses. In addition, the possibility of its application in the fabrication of homogeneous and transparent multilayer elements was investigated. Method. The investigations were conducted in the visible and infrared (IR) spectral regions using optical spectroscopy methods. The kinetics of the structural changes in the epoxy composition during polymerization were investigated by IR spectroscopy. Main results. The results showed that 80% of the structural changes, observed in the epoxy ring during the complete polymerization of its composition, occurred under isothermal exposure at 20°C in the first 160 min. Epoxy compositions with high adhesion to the surfaces of both organic and inorganic glasses were obtained. The compositions were used to fabricate multilayer glass-based materials transparent to visible light. Practical significance. The universal optical adhesive composition obtained in this study can be used for bonding both silicate glasses and organic glasses based on polymethyl methacrylate.

Singlet oxygen is a metastable reactive oxygen species involved in numerous biochemical reactions and physiological processes. This suggests its potential applicability in addressing practical challenges in medicine and human safety. Due to its oxidative properties, singlet oxygen effectively eliminates pathogenic organisms, including bacteria, fungi, and viruses, and is utilized in photodynamic therapy for the treatment of various diseases, including oncological and dermatological pathologies. Traditionally, photosensitizers are employed for its generation; however, they exhibit significant drawbacks, such as toxicity, low selectivity toward affected cells, and the requirement for high-intensity optical radiation. One promising solution involves the use of photocatalytic materials capable of generating singlet oxygen in both liquid and gaseous phases. The lifetime of singlet oxygen molecules in the gas phase is substantially longer than in liquids. Investigating methods for generating singlet oxygen in the gas phase represents a pressing scientific challenge. Currently, there is a lack of publications in scientific literature describing the qualitative and quantitative characteristics of air mixtures enriched with reactive oxygen species. The development of singlet oxygen generators in the gas phase of atmospheric air is an urgent task with multiple functional applications in medicine and safety technologies. This study presents and examines an experimental prototype of a device designed for generating singlet oxygen in the gas phase of atmospheric air. The design incorporates the authors’ research on the development of an original photocatalytic nanocrystalline coating based on ZnO-SnO₂-Fe₂O₃, capable of producing singlet oxygen under irradiation with optical radiation near the visible spectrum (405 nm). A novel device model has been developed, featuring a reusable photocatalyst. The materials were characterized using X-ray diffraction analysis and atomic force microscopy. Singlet oxygen generation activity was assessed via electron paramagnetic resonance spectroscopy. The achieved photogeneration rate of singlet oxygen was 100 (μmol/L)/min. The calculated concentration of singlet oxygen in the air at the device outlet under normal conditions, determined based on the photodegradation rate of rhodamine 6G dye in porous glass, reached 10 (μmol/L)/min. The presented prototype exhibits low energy consumption, environmental safety, cost-effective materials, utilization of near-visible spectrum radiation, and the ability to generate singlet oxygen without toxic oxidizing byproducts. The developed prototype allows for the creation of multiple modifications, enabling a range of multifunctional devices for individual or group therapeutic use as well as for engineering solutions aimed at ensuring a safe living environment. Selective singlet oxygen generation permits the application of these devices in medical settings, both for direct tissue contact and for establishing breathable air environments conducive to human life.

Glass and glass-crystalline MgO-Al₂O₃-SiO₂ system materials have many practical applications including their use as luminophores. To lower the synthesis temperature of such materials is an actual task. In this work, Mn-containing materials of MgO-Al₂O₃-ZrO₂-SiO₂ system were synthesized by sol-gel method. The analytical chemical composition, crystal structure, morphology and luminescence spectra were investigated by X-ray phase analysis, scanning electron microscopy, energy dispersive analysis and luminescence spectroscopy. It was found that the introduction of fluoride component into sols significantly accelerates the crystallization of Mn-containing gels during their heat treatment and has a significant effect on the morphology of xerogels. Fluorides play the role of additional nucleation centers and ensure the formation of numerous small oxide crystals. Energy dispersive analysis showed that fluoride is completely removed from the structure of materials during heat treatment of gels up to 900 °C. According to the data of X-ray phase analysis, the introduction of manganese ions into the structure of forming oxide crystals and deformation of their crystal lattice occurs at the initial stages of the crystallization process. Emission bands of both manganese ions and structural defects formed in the crystal lattice of oxide crystals are observed in the photoluminescence spectra of xerogels. It was shown that in addition to using the sol-gel method, which is a well-known approach, the addition of fluorine-containing precursor significantly accelerates crystallization of gels of MgO-Al₂O₃-ZrO₂-SiO₂ system, promotes formation of dispersed structure of materials, increases intensity, and improves resolution of emission bands in luminescence spectra.

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This work demonstrates for the first time the selectivity of silver molecular clusters luminescence in silicate glass formed by the ion exchange method from a salt melt containing 0.1 mol.% silver nitrate (AgNO3) and 99.9 mol.% sodium nitrate (NaNO3). Commercial silicate microscope slides of the following system were used: SiO2-Na2O-K2O-CaO-MgO-Al2O3 with Fe2O3-SO3 impurities. Molecular clusters were obtained by low-temperature ion exchange in a melt of 0.1 % AgNO3/99.9 % NaNO3 mol.% for 10 and 15 min at 320 °C. The luminescent properties of silver molecular clusters in the ion-exchange layer of microscope slides were studied. Bands of silver clusters of different sizes (Ag1-5) were found in the luminescence spectra. In this case, clusters Ag1-3 are excited by shorter wavelengths, and clusters Ag4-5 only by far ultraviolet and visible radiation up to 500 nm. In the process of ion exchange lasting up to 10 minutes, the appearance of luminescence selectivity was revealed, which occurs due to the presence of a low concentration of silver clusters of different sizes Ag1-5 in the ion-exchange layer. The obtained results can be used in the development of a photosensitive element for a selective ultraviolet radiation detector.

In present work Mn2+-doped MgO-Al2O3-ZrO2-SiO2 materials were synthesized. Their structure, morphology, chemical composition and luminescent properties were studied using X-Ray diffraction, scanning electron microscopy, EDX analysis and luminecent spectroscopy. It was shown that the application of sol-gel method provides the high-volume homogeneity of chemical composition of synthesized materials. Introduction of Mn into the composition of sol-gel materials accelerates significantly the crystalization processes during the thermal treatment. In the luminescence spectra several groups of emission bands are observed. These bands are situated in blue and yellow-red part of spectrum. this phenomenon is related with incorporation of Mn2+ into the structure of different crystals formed during the thermal treatment of gels. Obtained materials can be perspective for application as luminophores in the lighting for plant production.

Synthesis and study on structure and properties of organic-inorganic composites based on epoxy resin, CuO and Fe3O4 absorbing light in infrared part of spectrum was performed. The composites synthesis was performed by introduction of CuO and Fe3O4 micropowders into liquid epoxy composition with subsequent homogenization of the mixture and polymerization. The study on structure and properties of organic-inorganic composites was performed by methods of optical microscopy, infrared and visible spectroscopy, study on microhardness. According to the IR spectroscopy data, introduction of oxide particles leads to decrease in epoxy polymer degree of calcification. The composites containing Fe3O4 show relatively low light reflection until 4.2 % in the spectral range of 1000–1100 nm that corresponds to the theoretical estimation data. Incorporation of CuO and Fe3O4 micropowders into the epoxy polymer leads to an increase in microhardness from 120 to 160 MPa. Obtained experimental data can serve as the base for development of IR-absorbing organic-inorganic composites for laser technology.