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The aim of the work is to study the influence of the 3-D printing process with the Hercules Original printer by sequentially applying polymer layers using the FDM (Fused Deposition Modeling) method on the microstructural and hydrophilic properties of polyethylene terephthalate glycol (PETG) samples with different printing patterns. X-ray phase analysis revealed the presence of a greater ordering of amorphous PETG polymer chains in printed samples, which occurs during thermal and mechanical impact on the initial filamentous sample during 3D printing. This manifests itself in the increase of relative intensity for the main diffraction peak of the amorphous PETG polymer by an order of magnitude for all of the samples with five different print patterns. At the same time, IR spectroscopy data revealed the preservation of all intrastructural chemical bonds of the polymer both in the original thread and in printed samples. Close contact angles of about q≈50° for all printed samples, which is much smaller than the right angle q=90°, show that the surfaces of all five printed PETG samples with different patterns are hydrophilic

Porous silicon is a promising nanomaterial for optoelectronics and sensorics, as it has a large specific surface area and is photoluminescent under visible light. The deposition of copper particles on the surface of porous silicon will greatly expand the range of applications of the resulting nanocomposites. Copper was chosen due to its low electrical resistivity and high resistance to electromigration compared to other metals. The purpose of this research was to study changes in the structure and composition of porous silicon after the chemical deposition of copper. Porous silicon was obtained by the anodisation of monocrystalline silicon wafers KEF (100) (electronic-grade phosphorus-doped silicon) with an electrical resistivity of 0.2 Ohm·cm. An HF solution in isopropyl alcohol with the addition of H2O2 solution was used to etch the silicon wafers. The porosity of the samples was about 70 %. The porous silicon samples were immersed in copper sulphate solution (CuSO4·5H2O) for 7 days. We used scanning electron microscopy, IR spectroscopy, and ultrasoft X-ray emission spectroscopy to obtain data on the morphology and composition of the initial sample and the sample with deposited copper. The chemical deposition of copper on porous silicon showed a significant distortion of the pore shape as well as the formation of large cavities inside the porous layer. However, in the lower part the pore morphology remained the same as in the original sample. It was found that the chemical deposition of copper on porous silicon leads to copper penetrating into the porous layer, the formation of a composite structure, and it prevents the oxidation of the porous layer during storage. Thus, it was demonstrated that the chemical deposition of copper on a porous silicon surface leads to visible changes in the surface morphology and composition. Therefore, it should have a significant impact on the catalytic, electrical, and optical properties of the material

The growth of nanoscale columnar AlxGa1-xN/AlN heterostructures on the surface of silicon substrates using plasma-activated nitrogen molecular-beam epitaxy was investigated in this work. Silicon substrates include atomic-smooth cSi substrate, Si substrate with a transition layer of porous silicon porSi/cSi and a hybrid substrate involving a silicon carbide layer grown with matched substitution of the atoms on the surface of porous silicon SiC/porSi/cSi. A complex analysis performed using a set of structural and spectroscopic techniques demonstrated that the epitaxial growth of the nuclear AlN layer on all types of the substrates in a N-enriched environment resulted in the formation of AlxGa1-xN/AlN heterostructures with a Ga-polar surface, which was realized only on the SiC/porSi/cSi substrate. The layer of AlxGa1-xN on cSi and porSi/cSi substrates was in the state of disordered alloy with an excess of gallium atom content. It was shown that a great difference in the lattice parameters of a substrate–film pair resulted not only in the appearance of a number of various defects but also in a considerable effect on the chemical process of the formation of the alloys, in our case, the AlxGa1-xN alloy. It was shown that nanoscale columns of AlxGa1-xN formed on SiC/porSi/cSi substrate were inclined relative to the c-axis, which was connected with the features of the formation of a SiC layer by the matched substitution of the atoms on the porous Si substrate, resulting in the formation of the inclined (111) SiC facets at the boundary of the (111) Si surface and pores in Si. Optical studies of the grown samples demonstrated that the optical band-to-band transition for the AlxGa1-xN alloy with Eg = 3.99 eVB was observed only for the heterostructure grown on the SiC/porSi/cSi substrate. A qualitative model is proposed to explain the difference in the formation of AlxGa1-xN layers on the substrates of cSi, porSi/cSi and SiC/porSi/cSi. The results obtained in our work demonstrate the availability of using SiC/porSi/cSi substrates for the integration of silicon technology and that used for the synthesis of nanoscale columnar AlxGa1-xN heterostructures using plasma-activated molecular-beam epitaxy with a nitrogen source.

Introduction. At present, sorption methods of analysis, including the thermal desorption of inert gases, are widely adopted to characterize the porous structure parameters of nanomaterials having a wide range of applications. Nitrogen thermal desorption belongs to the group of nondestructive techniques that provide a rapid analysis of the following parameters exhibited by nanomaterials: specific surface area, average particle size, mesopore size distribution, as well as the presence or absence of micropores in the system. In this work, mesoporous silicon and calcium hydroxyapatite powders are selected as the objects of research. Since modern interference optical filters are cumbersome and expensive to use, meso- and nanoporous silicon nanostructures are of interest in the implementation of filters for fiberoptic communication systems. Hydroxyapatite can potentially provide high corrosion resistance while posing no risk of toxicity to the environment. In addition, anticorrosion hydroxyapatite coatings are of decisive importance for the practical application of magnesium alloys used to reduce the weight of vehicles, aircraft, and electronics housings.Aim. To consider the application of the thermal desorption of inert gases, specifically nitrogen thermal desorption, in the study of the porous structure parameters of nanomaterials having various compositions on the example of mesoporous silicon and hydroxyapatite.Materials and methods. In this work, the thermal desorption of inert gases and capillary condensation were applied to study the porous structure parameters of hydroxyapatite and porous silicon powders. In particular, the nitrogen thermal desorption method was implemented using a Sorbi MS instrument equipped with a Sorbi Prep sample preparation station.Results. Recommendations are provided on choosing the mass of the adsorbent material required for the study, the sample preparation conditions, as well as the relative partial pressure range of the gas adsorbate. The selected sample types were found to lack a micropore system in the structure. Finally, the dependence of the specific surface area of hydroxyapatite powders and the parameters of its mesoporous structure on heat treatment conditions was analyzed.Conclusion. The study of nitrogen adsorption and capillary condensation allows the porous structure parameters of hydroxyapatite and porous silicon to be reproduced, which is of great importance for their use in medicine and radio electronics as anticorrosion coatings, as well as for the implementation of optical filters.

In this study, we analyzed the result of the influence of the non-polar plane of a sapphire substrate on the structural, morphological, and optical properties and Raman scattering of the grown epitaxial GaN film. It was found that selected technological conditions for the performed chloride-hydride epitaxy let us obtain the samples of structurally qualitative semi-polar wurtzite gallium nitride with (11¯22) orientation on m-sapphire. Using a set of structural and spectral methods of analysis the structural, morphological, and optical properties of the films were studied and the value of residual bi-axial stresses was determined. A complex of the obtained results means a high structural and optical quality of the epitaxial gallium nitride film. Optimization of the applied technological technique in the future can be a promising approach for the growth of the qualitative GaN structures on m-sapphire substrates.

Introduction. Global climate changes affect the habitats of insects, including mosquitoes, which are carriers of dangerous natural focal infections. When mosquitos develop new territories, they create a potential threat to people who find themselves in these areas. In the Krasnodar Region, a stable population of Ae. albopictus mosquitoes was formed in the 21st century. These mosquitoes are carriers of many viral pyrrhoid-focal infections, such as Dengue, Chikungunya, Zika fever and Yellow fever. Estimations of biological, epidemiological and cultural data can help to answer the question of the probability of occurrence of autochthonous cases of infection.Aim. To estimate the probability of occurrence of autochthonous cases of viral infections carried by Ae. albopictus mosquitoes on the territory of the Black Sea coast of the Krasnodar territory. For the review, we used scientific publications describing the occurrence of autochthonous diseases in similar climate zones inhabited by Ae. albopictus mosquitoes, the biology of these mosquitoes, as well as official reports of the sanitary services of Europe and the Russian Federation. A stable population of Ae. albopictus mosquitoes has formed on the Black Sea coast of the Krasnodar Territory. The local climate, including the temperature range is favourable for active reproduction of vectors and autochthonous transmission of viral infection.Conclusion. Despite the favourable conditions for the release of mosquitoes and the formation of a stable population, autochthonous transmission requires the introduction of the source of infection during the viremia period to infect the mosquito population. In recent years, isolated cases of such drifts have been reported in the Krasnodar Territory, which indicates a low probability of local cases of transmission. However, with the development of the tourism sector, the flow of tourists from endemic areas will inevitably increase. In addition, the increase in the well-being of the population, trips to these countries will become more frequent this may well increase the risk of transmission of viral infections by local mosquitoes. In any case, the weakening of epidemic control of mosquitoes and medical surveillance of imported cases of tropical fevers will have serious consequences.

Emerging and reemerging infections pose a grave global health threat. The emergence of the SARS-CoV-2 virus and the resulting COVID-19 pandemic have demonstrated the importance of studying of zoonotic viruses directly in natural foci. For SARS-like coronaviruses, as well as for many other zoonotic pathogens (including hemorrhagic fevers and rabies agents), the main reservoir are horseshoe bats (Rhinolophus spp.), which are widely distributed in Eurasia and Africa. Their range also covers the southern regions of Russia, including the North Caucasus and Crimea. Large colonies of these animals are located on the territory of Sochi National Park (SNP; subtropical zone of Krasnodar Territory, Greater Sochi region, North Caucasus). In total, according to long-term observations, up to 23 species of bats were registered here, including the great (Rh. ferrumequinum), the lesser (Rh. hipposideros), and the Mediterranean (Rh. euryale) horseshoe bats. This review provides information on zoonotic viruses associated with species of bats distributed in the subtropical zone of Krasnodar Territory of Russia, and analyzes their possible role as a natural reservoir of emerging and reemerging infections. Studying the circulation of zoonotic viruses in bats is an important element of monitoring viral populations in natural foci.

The aim of this work was the formation of multilayer structures of macroporous silicon and the study of their structural, morphological, and optical properties in comparison with the properties of multilayer structures of mesoporous silicon. The paper presents the results of the development of techniques for the formation of multilayer structures of porous silicon por-Si by stepwise change in the current with two-stage modes of electrochemical etching. The data on the morphology, composition, and porosity of macroporous and mesoporous silicon samples were obtained using scanning electron microscopy, IR spectroscopy, and X-ray reflectivity. It was shown that with the two-stage growth of porous silicon layers, the depth of the boundary between the layers of the structure was determined by the primary mode of electrochemical etching, while the total layer thickness increased with an increase in the current density of electrochemical etching. A comparative analysis of the relative intensity and fine structure of vibrational modes of IR spectra indicated a significantly more developed specific pore surface and greater sorption capacity of mesoporous silicon as compared to macroporous silicon.

In this work, we studied the efficiency of introducing nanoporous silicon as a buffer layer in the growth of AlxGa1–xN/AlN/Si(111) on a single-crystal silicon by molecular beam growth technology. We also considered its influence on the morphological characteristics and atomic composition of the surface layers of heterostructures. As determined by X-ray diffraction, microscopic, and X-ray photoelectron methods, the heterostructure grown on Si(111) n-type monocrystalline silicon wafer with nanoporous por-Si buffer layer has a more homogeneous epitaxial layer, and the surface morphology of the layer is also more homogeneous.

The aim of the work is to study the effect of the 3D printing process on the microstructural and hydrophilic properties of polylactic acid (PLA) samples with various model printing patterns obtained from the black filament PLA by sequentially applying polymer layers using the FDM (fused deposition modeling) method. X-ray phase analysis revealed the partial crystallization of PLA polymer chains in the printed samples, which occurs under thermal and mechanical action on the original amorphous PLA filament during 3D printing to varying degrees, depending on the geometry of the pattern and the morphology of its surface. At the same time, IR spectroscopy data indicate the preservation of all intrastructural chemical bonds of polylactide. Measured at the original installation, the values of the wetting edge angles on the surface of the printed samples are in the range φ = 50–60°, which is significantly less than the right angle. This indicates the hydrophilic properties of the whole sample's surface. At the same time, the influence of different geometries of model drawings in printed samples was found not only on the morphology of the sample's surface according to SEM data but also on its wettability. [ABSTRACT FROM AUTHOR]

Purpose. In this study, some features of the formation of the multilayer structures in porous silicon were investigated by scanning electron microscopy and X-ray emission spectroscopy. Methods and tesniques. Method of electrochemical etching in hydrofl uoric acid solutions was used for the synthesis of substrates. Multi-layered structures were formed by the change of the current density during electrochemical etching (ECE). The morphology of the samples was studied by scanning electron microscopy (SEM). Phase composition of the samples at the different depth of analysis was investigated by ultrasoft X-ray emission spectroscopy (USXES). Computer simulation of the obtained emission spectra was performed using the spectra of references phases. Results. Multi-layered structures of porous silicon were obtained by the electrochemical etching technique at the step change of the current density in the ECE process. Using the SEM technique, pore sizes and the thickness of the formed porous silicon layers were determined. Analysis of the samples by USXES technique with the following computer simulation enabled an understanding of the regularities in the change of the phase composition for the samples of multi-layered por-Si structures of their formation regimes. Conclusion. Features of formation of the multi-layered por-Si structures at the step changes of the current density in ECE process were established. The morphology and phase composition of the porous layer for both single-layer and multilayer structures differed from the surface to the volume and depended on the regime of formation. This fi nding must be taken into account when creating functional electronics based on por-Si multilayers.

Purpose. In this work, we investigated the possibility of modifying porous silicon with silver particles. Methods and methodology. For the synthesis of substrates was used the method of electrochemical etching in hydrofl uoric acid solutions. Аt given technological parameters was formed a porous matrix. The resulting samples were subjected to further functionalization. For the synthesis of silver ink AgNO3 was used the method of colloidal quantum dots and then by the method of electro-thermal diffusion, these particles were deposited in a porous matrix to forming a composite structure. To study the samples was used by scanning electron microscopy. Morphology and diffusion processes were studied using SEM data. To control the functionalization process was used the method of determining the wetting angle. Results. Using the method of centrifugation, a silver layer was deposited on a porous silicon matrix. According to SEM data, it was established that the pore size is d = 50-100 nm, the layer thickness is 25 μm. Base on wetting angle data was concluded that the porous silicon matrix is initially hydrophobic (q ≈ 59°). After the deposition of silver particles, the hydrophobicity changes to hydrophilicity (q ≈ 31°) and further electrothermal effects have little effect on the wetting angle and the nature of hydrophilicity (q ≈ 42°). Conclusion. As a result of research work demonstrated the effectiveness of the electro-thermal methods for introducing silver into the porous silica matrix. It shows that the deposition of silver leads to a decrease in the hydrophobicity of the surface.

The process of desorption of vinpocetine on the surface of crystalline silicon and silicon oxide in various media has been studied by molecular dynamics modeling. The desorption of vinpocetine in water has been established both from the surface of silicon and from the surface of silicon oxide. The character of the desorption of vinpocetine from silicon and silicon oxide at pH 6.8 and pH 7 differs insignificantly (within the error of the simulation results). The desorption of vinpocetine in acidic medium (pH 2) from silicon and silicon oxide occurs more efficiently and at a higher rate, compared to pH 6.8 and pH 7.

Using High Resolution X-ray Diffraction (HRXRD) diagnostic techniques the influence of the transition layer of nanoporous silicon on the practical implementation and certain features of the epitaxial growth of GaN layers with the use of molecular beam epitaxy were investigated by means of plasma activation of nitrogen (MBE PA) on the templates of SiC/por-Si/c-Si. For the first time it was shown that introducing of the transition layer of nanoporous silicon in the template of SiC/por-Si/c-Si where the layer of 3C-SiC was obtained by substitution of the atoms had a number of indisputable advantages as compared with conventional silicon substrates. Particularly, such an approach, in fact, enabled a 90% reduction in the level of stresses in the crystalline lattice of the epitaxial GaN layer which was synthesized on SiC surface of SiC/por-Si/c-Si template by means of MBE PA technique as well as to decrease some of vertical dislocations within GaN layer.

We found and genetically described two novel SARS-like coronaviruses in feces and oral swabs of the greater (R. ferrumequinum) and the lesser (R. hipposideros) horseshoe bats in southern regions of Russia. The viruses, named Khosta-1 and Khosta-2, together with related viruses from Bulgaria and Kenya, form a separate phylogenetic lineage. We found evidence of recombination events in the evolutionary history of Khosta-1, which involved the acquisition of the structural proteins S, E, and M, as well as the nonstructural genes ORF3, ORF6, ORF7a, and ORF7b, from a virus that is related to the Kenyan isolate BtKY72. The examination of bats by RT-PCR revealed that 62.5% of the greater horseshoe bats in one of the caves were positive for Khosta-1 virus, while its overall prevalence was 14%. The prevalence of Khosta-2 was 1.75%. Our results show that SARS-like coronaviruses circulate in horseshoe bats in the region, and we provide new data on their genetic diversity.

Quite a number of studies today focus on the use of biocompatible and biodegradable nanostructures – such as silicon nanostructures and silicon nanopowders – as a practical tool for the diagnostics of various diseases and targeted delivery of drugs or dyes. In order to further improve the technology for the preparation of nanostructured materials for medical applications it is necessary to address a number of problems. They include the peculiarities of the formation process of the samples and their structure, as well as the optical properties of nanostructured materials. The aim of this paper is to study the way that electrochemical etching affects the crystal structure of porous silicon obtained using various techniques. We also focus on the optical absorption properties of the obtained samples and the changes that the optical properties of the samples undergo when the porous layer is ground up to powder. Porous silicon samples were obtained by electrochemical etching of single-crystalline silicon KEF with a resistivity of 0.2 Ohm·cm. The etching current density was j = 25 mA/cm2. The etching was performed for 10 minutes in various solutions of fl uoric acid. Porous silicon powder was obtained via mechanical separation of the porous layer from the Si substrate and its further fractionation in the ultrasonic bath. After that, the powder was separated into light and heavy fractions in a centrifuge. Using the results of X-ray diffraction and the Scherrer equation, we calculated the size of the Si crystals of the porous layer. The lattice constant of these crystals coincided with the lattice constant of the crystalline silicon. In order to determine the mechanisms of optical absorption in the porous layers, the analysis of the absorption spectra of the samples was performed using the Beer–Lambert–Bouguer law. Thus, using X-ray diffraction and UV-spectroscopy we studied two groups of porous silicon with different pore size, as well as the powders obtained from these samples. We found that the electrochemical formation of the porous layer resulted in the disorder of the crystals in the porous layer as compared to the initial substrate. We also determined the characteristic features of the optical absorption spectra of the porous layers and the nanopowders, and the difference between them.

Using a set of spectroscopic methods, the properties of epitaxial GaxIn1–xP alloys with the ordered arrangement of the atoms in a crystal lattice grown by MOCVD on single-crystalline GaAs (100) substrates were studied. Based on the data of the dispersion analysis for IR reflection spectra and UV-spectroscopy data obtained in transmittance-reflection mode, the basic optical characteristics of the ordered GaxIn1–xP alloys were determined for the fi rst time, i.e. dispersion of the refractive coeffi cient and high-frequency dielectric permeability. The study of the optical and photoluminescence properties of the ordered GaxIn1–xP alloys in the UV spectral range confi rms previous data that the metal-organic chemical deposition of the vapors (MOCVD) not only gives rise to a strong CuPt-B type ordering, but also ensures a good uniformity of the fi lm and its transmission capacity. A decrease in the band gap energy on the ordered GaxIn1–xP alloy determined in our experiments at the specifi ed level of distortion and factor of the order is in good agreement with the theoretical data and similar experimental studies. Comparing the value of high-frequency dielectric permeability ε∞ for the epitaxially ordered GaxIn1–xP alloys with that for the disordered alloys of the same composition x ~ 0.50 determined from the analysis of IR refl ection spectra, it was shown for the fi rst time that this parameter for the ordered alloy was 1.5–2 times higher. Also it was shown that the refractive index for the epitaxial fi lms with ordering is 1.5–2.5 times higher than that for disordered values of the same composition x ~ 0.50. Moreover, the maximum value of refractive index for the sample with a high degree of order was n = 5.45 at the wavelength of ~ 680 nm, while the close value for the disordered alloy with a similar composition of x ~ 0.50 was attained in the wavelengths in the range of ~ 330–340 nm.

Alloys based on A3B5 semiconductors have attracted the interest of researchers of semiconductor optoelectronics. These alloys are characterized by a positive formation enthalpy that facilitates superstructure ordered phases on the basis of these alloys, with formation of a domain structure under certain technological conditions. The spontaneous appearance of periodically ordered structures on the surface and in the epitaxial fi lms of A3B5 semiconductors covers a broad range of phenomena in solid state physics and semiconductor technology, specifi ed by the processes of selforganization in the condensed matter. This is of particular interest for the production of semiconductor nanostructures with typical sizes of ≤ 100 nm. This phenomena of the ordering appearance in A3B5 allows the inclusion of narrow-band semiconductors in a wide-band gap matrix and vice versa, thus creating a localizing potential for the current carriers. Periodical structures of these inclusions can form superlattices comprised of quantum wells, wires or quantum dots. Furthermore, the spontaneous appearance of the nanostructures provides a basis for a new technology for the production of ordered arrays of irregularities, moreover, the basis for the next generation opto- and microelectronics. The aim of this study was to investigate the structural properties of epitaxial GaxIn1-xP alloys with atomic ordering grown by MOCVD in a coherent way on GaAs (100) substrates. Epitaxial layers of GaxIn1–xP with ordering matched by the parameter of the crystal lattice with singlecrystalline GaAs (100) substrates were grown by MOCVD in a horizontal reactor. The structural quality of the heterostructures and determination of the lattice parameters in the alloys were performed by X-ray diffraction with an X-ray diffractometer DRON 4-07 and characteristic radiation of cobalt. The study of the surface morphology was performed by atomic-force microscopy using a NTEGRA Therma (NT MDT) microscope. The concentration of the elements in the alloys was refi ned by X-ray microanalysis using an Oxford Instruments attachment to the electron microscope JEOL. Using a set of structural and microscopic methods, the properties of epitaxial GaxIn1-xP alloys with the ordered arrangement of the atoms in a crystal lattice grown by MOCVD on single-crystalline GaAs (100) substrates were studied. It was shown that in the conditions of coherent growth of GaxIn1–xP alloy on the GaAs (100) substrate, the observed atomic ordering and tetragonal distortion resulted in the change in the crystal lattice parameter. Consequently, this led to a reduction in the crystal symmetry, formation of two different nanorelief types on the surface in comparison with the properties of disordered alloys. For the fi rst time, the crystal lattice parameter was calculated for GaxIn1-xP alloys with ordering grown in a range of compositions corresponding to coherent growth taking into account the elastic stresses on GaAs (100) substrates dependent on the order parameter (long-range ordering).