This article reports a new straightforward method for producing hydrophobic GeO2 aerogels in a one-pot synthesis. For the first time, the epoxide-induced sol–gel process was combined with the co-precursor method to create hydrophobic aerogels. The application of a complex of analytical methods like SEM, TEM, low-temperature nitrogen adsorption–desorption, SAXS and contact angle measurements enabled us to determine that varying the GeCl4:(C2H5)2GeCl2 ratio allows for targeted adjustments in the morphology, porous structure, and surface properties of aerogels. As the proportion of (C2H5)2GeCl2 grows, the surface area increases from 45 to 123 m2∙g−1 and the contact angle changes from 22.1 to 140.1°. Luminescent properties of the hydrophobic GeO2 aerogels are reported for the first time, and it is established that the ratio of green and blue bands in the luminescence spectra when excited under 390 and 235 nm varies depending on the GeCl4:(C2H5)2GeCl2 ratio used for the aerogel preparation.

BACKGROUND: One of the obstacles in successful radiation therapy of malignant tumors is the emergence of cell subpopulation that have lower radiosensitivity than the original tumor. Use of fractionated irradiation in this case leads to a possibility of the radioresistant cells to substitute the initial cell population. We assume that changes in epigenetic profile of a cell affect chromatin packaging in the cell nucleus. This in turn represents changes leading to formation of the radioresistant phenotype. AIM: The aim is to study the structure of nuclei of a subpopulation of Ehrlich adenocarcinoma cells with a radioresistant phenotype. METHODS: In the present study the cells of ascitic Erlich adenocarcinoma have been sequentially irradiated in the PX-γ-30 (source is 60Co, dose output is 0.87 Gy/min). Then the cells have been inoculated into female outbred mice ICR (CD-1). Irradiation of the original population of Erlich adenocarcinoma showed that cells were losing an ability to transplantation after a dose of 20 Gy. In the series of irradiations with a gradual dose increase (from 10 to 40 Gy) there was obtained a cell subpopulation that retains an ability to transplantation after a dose of 40 Gy. The original and radioresistant cell subpopulations were tested for sensitivity to ionizing radiation. Nuclei were collected from these cells for further structure investigation with the method of small angle X-ray scattering (SAXS). RESULTS: Analysis of SAXS data of the nuclei showed no significant changes in nucleus structures of Erlich adenocarcinoma initial cells that survived irradiation with doses of 20 and 30 Gy. At the same time, Erlich adenocarcinoma cells that survived irradiation with a dose of 40 Gy demonstrated abnormally low fractal dimension on mass fractal mode (in a size of 40–200 nm). CONCLUSION: Observations of chromatin packing variations well conform with data obtained by biological characterization of researched samples and appear as a crucial aspect of understanding mechanisms of radioresistance occurrence.

An Erratum to this paper has been published: https://doi.org/10.1134/S0031918X24120044

A series of silica-based aerogels comprising novel bifunctional chelating ligands was prepared. To produce target aerogels, two aminosilanes, namely (3-aminopropyl)trimethoxysilane (APTMS) and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS), were acylated by natural amino acids ((S)-(+)-2-phenylglycine or L-phenylalanine), followed by gelation and supercritical drying (SCD). Lithium tetrachloropalladate was used as the metal ion source to prepare strong complexes of Pd2+ with amino acids covalently bonded to a silica matrix. Aerogels bearing chelate complexes retain the Pd2+ oxidation state after supercritical drying in CO2, but the Pd ion is reduced to Pd metal after SCD in isopropanol. Depending on the structure of amino complexes, Pd-containing aerogels showed catalytic activity and selectivity in the hydrogenation reactions of C=C, C≡C and C=O bonds.

Ionogels were obtained by impregnating Aerosil A380 with 1-methyl-3-octyl-imidazolium tetrafluoroborate (OMIM BF4) ionic liquid (IL). The IL content of the ionogels varied from 16.3 to 79.9 mol %. There was evidence of the confinement of the IL in silica in the shift and broadening of the BF4 - 19F NMR signal and in the noticeable (similar to 50 degrees C) decrease in the temperature of IL decomposition. For both the ionogels and the pure IL, the frequencies of IR vibrations were different, providing further evidence of the confinement effect. An analysis of textural characteristics revealed that, upon its addition to Aerosil, the IL sequentially adsorbed in the micropores, mesopores and interparticle space. SAXS measurements showed that, in the confined IL, the size of nonpolar correlations substantially increased, from 21.5 & Aring; in the bare IL to 25.6 & Aring; in the ionogel containing 28.1 mol % IL. Unexpectedly, for the ionogel with the lowest IL content (16.3 mol %), no nonpolar correlations were observed, indicating the strong distortion of the structure of the confined ionic liquid. To the best of the authors' knowledge, this is the first report on regular changes in nonpolar correlations in ionic liquids upon confinement in a porous solid. These structural correlations can easily be tuned by simply changing the IL content in the ionogel material.

Nanostructures of a wide range of oxide dispersion strengthened (ODS) steels are characterized using small-angle X-ray scattering (SAXS). The systems of alloying of the studied steels differ in the content of Cr, V, Ti, Al, and Zr. It is shown that the use of SAXS makes it possible to determine the number density of nanosized inclusions in ODS steels and their size distribution.

One step method of iron oxides nanoparticles synthesis using novel type of microreactors was reported. All the data received from analysis of physical and chemical properties demonstrated that the nanoparticles obtained by means of the new method are similar to the nanopowders synthesized by wet precipitation. They are magnetite-maghemite solid solutions with unit cell parameter between 8.362 and 8.374Å, with coherent scattering range values about 9nm. In comparison with precipitated nanopowders they have lesser degree of agglomeration. Samples obtained in microreactor have smaller value and smaller spread in regard of the specific surface (76-86 m2/g) in comparison with precipitated ones (75-125 m2/g). All the samples from microreactor consist of spherical inhomogeneities with a diffuse surface, while sample of iron oxide nanopowder synthesized by the co-precipitation method consists of scattering cylindrical inhomogeneities with nearly smooth phase boundary. It was shown that microreactor with intensively swirling flows has demonstrated several advantages: (i) possibility to control the degree of oxidation of the product which depends on the flow rates of reagents solutions to the reactor; (ii) high productivity (up to 7L/min for the suspension with particles, approx. 200kg/day for the dried particles) that eases the scaling-up of the proposed synthesis method.

Nanopowders of the magnetite–maghemite series have been synthesized by coprecipitation from aqueous solutions and by the sol–gel method, and a comparative comprehensive study of their structure has been carried out using X-ray diffraction analysis, scanning electron microscopy, low-temperature nitrogen adsorption, and small-angle polarized neutron scattering. It has been established that the resulting iron oxide nanopowders are porous systems that, depending on the synthesis method, have a one-level, two-level (for powders obtained by aqueous synthesis), or three-level (for powders obtained by the sol–gel method) hierarchical structure organization with different scales and different types of aggregation for each of the structural levels, and the characteristic size for the larger level in both cases is >45 nm. It has been revealed that the magnetic structure of the obtained iron oxide powders, regardless of the synthesis method, consists of superparamagnetic particles with a characteristic radius of magnetic RM ⁓ 4 nm and magnetic–nuclear cross-correlations RMN ⁓ 3 nm for powders obtained by the sol–gel method, and RM ⁓ 5–11 nm and RMN ⁓ 4–8 nm for powders obtained via aqueous route, depending on the synthesis conditions.

Nanopowders of the magnetite-maggemite series were synthesized by both aqueous precipitation and using sol-gel technology. A comprehensive comparative study of the structure of the synthesized powders was carried out using the methods of X-ray phase analysis (XPA), scanning electron microscopy (SEM), low-temperature nitrogen adsorption and small-angle polarized neutron scattering (SAPNS). It has been established that the synthesized iron oxide nanopowders are porous systems that, depending on the synthesis method, have a one-level or two-level (for powders obtained by aqueous synthesis) and three-level (for powders obtained by the sol-gel method) hierarchical structure organization with different characteristic scales and types of aggregation for each from structural levels, and the characteristic size for the larger level in both cases exceeds 45 nm. It was revealed that the magnetic structure of the obtained iron oxide powders, regardless of the synthesis method, consists of superparamagnetic particles with a characteristic magnetic radius RМ ≈ 4 nm and magnetic-nuclear cross-correlations RMN ≈ 3 nm for powders obtained by the sol-gel method; and with RM ≈ 5–11 nm and RMN ≈ 4–8 nm for powders obtained by aqueous synthesis, depending on the production conditions.

In this work, the nanostructure of oxide dispersion-strengthened steels was studied by small-angle neutron scattering (SANS), transmission electron microscopy (TEM), and atom probe tomography (APT). The steels under study have different alloying systems differing in their contents of Cr, V, Ti, Al, and Zr. The methods of local analysis of TEM and APT revealed a significant number of nanosized oxide particles and clusters. Their sizes, number densities, and compositions were determined. A calculation of hardness from SANS data collected without an external magnetic field, or under a 1.1 T field, showed good agreement with the microhardness of the materials. The importance of taking into account two types of inclusions (oxides and clusters) and both nuclear and magnetic scattering was shown by the analysis of the scattering data.

A first composite material containing uniformly dispersed disaggregated detonation nanocrystalline diamonds (DNDs) in SiO2 aerogel matrix was prepared. The synthetic protocol included hydrolysis of tetramethyl orthosilicate (Si(OMe)4, TMOS) by hydrosol of surface carboxylated DNDs with a typical size of 4‐5 nm with DMSO serving as a cosolvent and a stabilizer of DND single crystals. Composite samples containing DNDs in silica aerogel matrix in concentration 1.0, 0.1 and 0.01% w/w were prepared at ambient temperature. HRTEM data revealed that DNDs nanocrystals were uniformly distributed in aerogel and did not form aggregates. Textural and optical composites’ properties were determined.

The superatomic structure of film-forming sols obtained by the acid hydrolysis of tetraethoxysilane (TEOS) in an aqueous medium (free of organic solvents) was studied using the SAXS method. The formation of nanoparticles (NPs) was confirmed in alcohol-free silica sols with both a low (1 vol. %) content of TEOS and a high (10 vol. %) content of TEOS, hydrolyzed in an aqueous-alcoholic medium. A trimodal size distribution was revealed for the resulting NPs, with radii ranging from less than 1 nm to ~11 nm. The volume fraction of NPs tends to grow with increases in TEOS concentration, as well as with the introduction of magnetic NPs of iron oxides into silica sols. The synthesized silica sols and suspensions based on silica sols with FexOy NPs were used for the pre-sowing treatment of white and cauliflower cabbage seeds in order to provide a functional coating on their surfaces, thereby improving seed germination, stimulating their growth in the early stages of development, and suppressing the effect of phytopathogens. The effect of the pre-sowing seed treatment in sol-gel compositions on seed germination and the growth characteristics of plant seedlings is analyzed, including the influence of iron-oxide magnetic NPs’ compositions and concentrations in silica sols.

Iron oxide nanopowders are synthesized via chemical precipitation. It is shown that synthesis produces an iron oxide phase with a magnetite structure (either a magnetite–maghemite solid solution or a mixture of this solid solution and goethite). The sizes of the CSR and particles for the main phase are 10–20 nm. The synthesized iron oxide powders have developed surfaces, specific surface area SBET ≈ 92 and 117 m2/g, and identical fairly large specific pore volumes ( V_P_/P_0→ 0.99_ = 0.35 cm3/g). It is shown that additional in situ ultrasonic treatment of the magnetic iron oxide nanoparticles in the mother liquor results in abrupt oxidation of iron(II) ions and creates a nonmagnetic impurity phase of goethite.

A new method was proposed to synthesize aerogels based on Al2O3–TiO2 by the hydrolysis of mixed solutions of titanium tetrachloride and aluminum nitrate in the presence of propylene oxide, followed by supercritical drying of the obtained gels. The aerogels are characterized by a high specific surface area (140–500 m2/g) and a high specific porosity (1.7–2.7 cm3/g). Heat treatment of the Al2O3–TiO2 aerogels at temperatures up to 600°C does not lead to crystallization of titanium dioxide, whereas the formation of crystalline anatase in aerogels based on individual TiO2 is observed already at a temperature of 450°C. Using the standardized ISO 24443-2016 method, the SPF value of the obtained materials was determined, which turned out to be comparable to the characteristics of a commercial inorganic UV filter based on TiO2 (Kronos 1171). At the same time, the photocatalytic activity of the Al2O3–TiO2 aerogels turned out to be more than 120 times lower than the similar characteristics of the commercial UV filter based on titanium dioxide. The results obtained demonstrated that the Al2O3–TiO2 aerogels are promising as components of sunscreens.

The Laetoli hominid footprints dating back some 3.6 million years discovered by Leakey in 1978 is an archaeological site of great importance in understanding the humanHuman evolutionEvolution. The footprints of hominids, animals, and birds cast in the volcanic ash consolidated into tuff deposits are also an insight into the evolutionEvolution of the whole biogeosystem of this area dominated by volcanic activity. The volcanic ash deposits consolidated into tuffs are a marker which sets the base line for tracking the further sediment transport in the catchmentCatchment of this historic site. The surface of the tuff exposure along the Garusi river carrying the footprints shows no signs of weatheringWeathering and the soils of the area form in subsequent sediments that filled the valley after the deposition of the tuff material. Following the deposition and consolidation of the airfall tuffs, the biogeosystem of the Laetoli gorge and its surroundings experienced a complex evolutionEvolution which led to formation of the present-day soil cover. The study of clay mineralogyMineralogy of these soils has provided interesting insights into the evolutionEvolution of this system.

The surface of TiO2 nanoparticles was modified with silica prepared by acid hydrolysis of tetraethoxysilane followed by polycondensation. A comparative characterization of the initial and modified nanoparticles by TEM, XRD, specific surface area and ζ-potential measurements as well as the estimation of the surface acid-base properties via dynamic pH measurements revealed that the applied surface modification provided almost no changes in the phase composition, crystallite size range (~16 nm) and mesostructure of the initial anatase nanoparticles, but resulted in a more than twofold increase in the specific surface area and change of the surface functionality from a prominent Lewis acidity toward a relatively weak Broensted acidity. The resulting TiO2@SiO2 “core-shell” particles are shown to exhibit a significant enhancement of singlet oxygen generation compared with the initial TiO2. In conjunction with increased specific surface and modification of the surface centers, this effect promoted a drastic growth of photocatalytic activity indicated by an almost 90% degradation of methylene blue dye upon UV irradiation.

Biomineralization is a universal process that has implications in a variety of areas, from civil engineering to medicine. While crystallization of amorphous CaCO3 formed in vitro is known to precede the vaterite-calcite/aragonite pathway, this process could be significantly altered when induced by bacteria, particularly within the extracellular matrix (ECM) of microbial cells. We used a combination of SEM, SANS, SAXS, FTIR and XRD methods to investigate the structure of CaCO3 formed during biomineralization induced by planktonic Bacillus cereus. Formation of precipitates in the presence of CaCl2 and urea was observed both during bacterial growth and in the medium devoid of bacteria and ECM (cell-free system). The pathway for polymorphic transformations of CaCO3 from the amorphous phase to vaterite and further to calcite was confirmed for the bacterium-induced mineralization and did not depend on the concentration of Ca2+ and urea. The structure of CaCO3 sediments differed when formed in cell-free and bacterial systems and varied depending on time and the medium composition. The rate of precipitation was accelerated in the presence of DNA, which had little effect on the solid phase structure in the cell-free system, while strongly affecting the structure and polymorphic composition of the precipitates in bacterial culture.

Oxide dispersion-strengthened steels are among the most promising materials for Generation IV reactor installations and thermonuclear power generation due to their high heat resistance, which is achieved by a significant number of uniformly distributed oxide particles. These materials can withstand temperatures up to 700°C and mitigate radiation-induced swelling within 200 dpa. The enhanced properties of such steels significantly depend on the specifics of their nanostructure, namely, the size and spatial distribution of dispersive inclusions (oxide particles and clusters). In this study, small-angle neutron scattering is applied to characterize the nanostructure of oxide dispersion-strengthened steels. This method enables the analysis of a large volume of material while retaining the ability to detect features such as clusters with sizes in the range of a few nanometers. The investigated steels have different alloying systems, varying in their concentration of Cr, V, W, Al, and Zr. Small-angle neutron scattering enables determination of the characteristic sizes of nanoscale inclusions in oxide dispersion-strengthened steels and their number densities. The results of small-angle neutron scattering are compared to the findings of transmission electron microscopy and atom-probe tomography.

The chemical immobilization of cobalt(II) ions in a silica aerogel matrix enabled the synthesis of the first representative example of aerogel-based single-ion magnets. For the synthesis of the lyogels, methyl-trimethoxysilane and N-3-(trimethoxysilyl)propyl ethylenediamine were co-hydrolyzed, then the ethylenediamine groups that were immobilized on the silica matrix enabled the subsequent binding of cobalt(II) ions. Lyogels with various amounts of ethylenediamine moieties (0.1–15 mol %) were soaked in isopropanol solutions of cobalt(II) nitrate and further supercritically dried in carbon dioxide to obtain aerogels with a specific surface area of 210–596 m2·g−1, an apparent density of 0.403–0.740 cm3·g−1 and a porosity of 60–78%. The actual cobalt content in the aerogels was 0.01–1.50 mmol per 1 g of SiO2, which could easily be tuned by the concentration of ethylenediamine moieties in the silica matrix. The introduction of cobalt(II) ions into the ethylenediamine-modified silica aerogel promoted the stability of the diamine moieties at the supercritical drying stage. The molecular prototype of the immobilized cobalt(II) complex, bearing one ethylenediamine ligand [Co(en)(MeCN)(NO3)2], was synthesized and structurally characterized. Using magnetometry in the DC mode, it was shown that cobalt(II)-modified silica aerogels exhibited slow magnetic relaxation in a nonzero field. A decrease in cobalt(II) concentration in aerogels from 1.5 mmol to 0.14 mmol per 1 g of SiO2 resulted in a weakening of inter-ion interactions; the magnetization reversal energy barrier likewise increased from 4 to 18 K.

New composite hydrogels (CH) based on bacterial cellulose (BC) and poly-1-vinyl-1,2,4-triazole (PVT) doped with orthophosphoric acid (oPA), presenting interpenetrating polymeric networks (IPN), have been synthesized. The mesoscopic study of the supramolecular structure (SMS) of both native cellulose, produced by the strain Komagataeibacter rhaeticus, and the CH based on BC and containing PVT/oPA complex were carried out in a wide range of momentum transfer using ultra- and classical small-angle neutron scattering techniques. The two SMS hierarchical levels were revealed from 1.6 nm to 2.5 μm for the objects under investigation. In addition, it was shown that the native BC had a correlation peak on the small-angle scattering curves at 0.00124 Å−1, with the correlation length ξ being equal to ca. 510 nm. This motive was also retained in the IPN. The data obtained allowed the estimation of the fractal dimensions and ranges of self-similarity and gave new information about the BC mesostructure and its CH. Furthermore, we revealed them to be in coincidence with Brown’s BC model, which was earlier supported by Fink’s results.