Porous silicon (por-Si) is a complex multiphase material, the composition and functional properties of which greatly depend on the features of its formation. In this work, samples of porous silicon with porosity indices from 5 to 80% are obtained by electrochemical etching and their photoluminescence properties are studied. The porosity of the samples is varied by changing the current density of electrochemical anodization during the etching process. The porosity index is calculated according to the X-ray reflectometry method. The aim of our work is to establish correlations between the porosity index, composition, intensity, and mechanism of porous-silicon photoluminescence. The surface composition is controlled by ultrasoft X-ray spectroscopy and infrared spectroscopy. An increase in the degree of oxidation of the surface of the samples with an increase in the porosity index is shown. Two well-known mechanisms of porous silicon photoluminescence associated with the composition and morphology of the surface are found, and it is established at which porosity values they prevail. It is shown that an increase in the porosity index leads to an increase in the intensity of photoluminescence.

Chitosan takes second place of the most abundant polysaccharides naturally produced by living organisms. Due to its abundance and unique properties, such as its polycationic nature, ability to form strong elastic porous films, and antibacterial potential, it is widely used in the food industry and biomedicine. However, its low solubility in both water and organic solvents makes its application difficult. We have developed an environmentally friendly method for producing water-soluble graft copolymers of chitosan and poly (N-vinylpyrrolidone) with high grafting efficiency and a low yield of by-products. By using AFM, SEM, TGA, DSC, and XRD, it has been demonstrated that the products obtained have changed properties compared to the initial chitosan. They possess a smoother surface and lower thermal stability but are sufficient for practical use. The resulting copolymers have a higher viscosity than the original chitosan, making them a promising thickener and stabilizer for food gels. Moreover, the copolymers exhibit an antibacterial effect, suggesting their potential use as a component in smart food packaging.

In our work, we studied thin nickel films deposited by electroless plating for use as a barrier and seed layer in the through-silicon vias (TSV) technology. El-Ni coatings were deposited on a copper substrate from the original electrolyte and with the use of various concentrations of organic additives in the composition of the electrolyte. The surface morphology, crystal state, and phase composition of the deposited coatings were studied by SEM, AFM, and XRD methods. The El-Ni coating deposited without the use of an organic additive has an irregular topography with rare phenocrysts of globular formations of hemispherical shape and a root mean square roughness value of 13.62 nm. The phosphorus concentration in the coating is 9.78 wt.%. According to the results of the X-ray diffraction studies of El-Ni, the coating deposited without the use of an organic additive has a nanocrystalline structure with an average nickel crystallite size of 2.76 nm. The influence of the organic additive is seen in the smoothening of the samples surface. The root mean square roughness values of the El-Ni sample coatings vary within 2.09–2.70 nm. According to microanalysis data the phosphorus concentration in the developed coatings is ~4.7–6.2 wt.%. The study of the crystalline state of the deposited coatings by X-ray diffraction made it possible to detect two arrays of nanocrystallites in their structure, with average sizes of 4.8–10.3 nm and 1.3–2.6 nm.

Porous silicon samples with a porosity index of 5% to 80% were obtained in the work by electrochemical etching and their photoluminescence properties were studied as well, Porosity index was calculated according to the data of X-ray reflectometry technique.Composition of the surface was controlled by ultra-soft X-ray spectroscopy and infrared (IR) spectroscopy. Degree of the sample surface oxidation was shown to be increased with the enhancement of porosity enhancement. Two known mechanisms of photoluminescence in porous silicon were detected related with a composition and morphology of its surface. It was found the values of porosity index specifying the dominations of these mechanisms. An increase of porosity index was shown to result in the enhancement of photoluminescence.

tangar77@mail.ru Abstract. We present an experimental study of multilayer porous silicon formed by elec-trochemical etching. Special emphasis is placed on effects that arise from a stepwise decrease in the current density while maintaining the total etching time. In order to provide a fully understanding of the morphology of the surface, we used scanning electron and atomic force microscopy. X-ray reflectivity was used to assess the porosity of porous layers. It was found that a stepwise decrease in the current density leads to the formation of a two-layer structure without changing the porosity of the base bottom layer. However, the porosity of the top layer can be varied over a wide range, which directly affects the photoluminescence of the samples. Our results show how the sample production conditions affect the fine tuning of the surface layer morphology of multilayer porous silicon.

In this work, the X-ray reflectivity was used to study the porosity of multilayer macroporous silicon samples obtained under various conditions. The porosity calculation is based on a change in the position of the critical angle of total external reflection resulting from a decrease in the density of the porous silicon layer. Our findings show that the absence of photoluminescence in the samples is due to a porosity of about 30 % in the surface layer. The morphological features were characterized by scanning electron and atomic force microscopy.

The impact of layer thickness on the morphology and optical properties of MoS2 nanostructures, including monomolecular layers, formed by the carrier-gas-assisted transport of sulfur vapor to the hot zone of a reactor containing metallic molybdenum and subsequent deposition on mica (muscovite) substrates is investigated. Molybdenum disulfide nanostructures of different thicknesses grown at different temperatures of gas-transport synthesis are studied by atomic-force microscopy, optical absorption spectroscopy, and Raman spectroscopy. It is found that synthesis at temperatures of 525–600°C makes it possible to obtain monomolecular MoS2 layers containing trigonal domains and featuring direct-gap optical transitions at 1.84 eV with the formation of excitons at room temperature. Fractal-type MoS2 substructures are obtained for the first time. The frequencies of intralayer and interlayer vibrational modes $$E_{{2g}}^{1}$$ and A1g, respectively, in their Raman spectra (377.5 and 403.8 cm–1, respectively) differ both from the corresponding values for a monomolecular layer and the known frequencies for bulk samples. The frequency of the $$E_{{2g}}^{1}$$ intralayer mode in these samples (377.5 cm–1) is the lowest of all previously reported.

The new results of cathode surface degradation in muon proportional chambers of CMS after a long-term irradiation with a 90Sr β-source are presented. The data of the complex analysis of the copper foil samples from the cathode are shown. The AFM method revealed the general radiation damage of the copper surface and the dynamics of its change. It is clearly demonstrated that the revealed development of the radiation erosion on the cathode is a result of electron irradiation. Moreover, the nature of erosion and level of the destruction of copper are associated with irradiation intensity. The study of the elemental and phase composition together with the data of structural analysis allowed us to single out the stages of the radiation aging of the copper surface on the cathodes and consider the processes which are at the basis of them.

Abstract. The aim of the work is to show the effect of layer thickness on the features of the morphology and optical properties of MoS2 nanostructures, including the monomolecular layers, formed during the gas transporting transfer of sulfur vapors to the reactor hot zone with a molybdenum metal and subsequent deposition on the mica (muscavite) substrates. The results of the atomic force microscopy, optical absorption spectroscopy and Raman spectroscopy of molybdenum disulfide nanostructures of different thickness, obtained in temperatures interval of gas transport synthesis 525-600°C, show that a monomolecular MoS2 layers, containing trigonal domains and having a width of the band gap 1.84 eV at a direct-gap optical transition with the formation of excitons at room temperature, can be obtained. For the first time, fractal-like substructures were obtained, in the Raman spectra of which the values of the modes of intralayer and interlayer oscillations E12g 377.5 cm-1 and A1g 403.8 differ not only from the corresponding values of the modes of the monomolecular layer, but also from the known values of bulk samples. The frequency of the intralayer mode in these samples, E12g 377.5 cm-1, is the smallest of all known values.

Equilibrium sorption of saponin from Quillaja saponaria Molina with chitosan has been analyzed. The shape of the sorption isotherm is determined by the competing processes of the glycoside association in the solution and its absorption with chitosan, as evidenced by the calculated absorption and association energies and the curves of chitosan dehydration accompanying the saponin sorption. Analysis of the chitosan surface during the saponin sorption by means of atomic force microscopy has revealed the structure-morphology features depending on the glycoside concentration in the external solution.

The structural organization of inulinases from yeasts, fungi, and plants are researched. For studying their sizes, molecular weight, and permolecular organization, an approach consisting of a combination of atomic force microscopy with methods of dynamic light scattering, gel chromatography, and electrophoresis was used. It is shown that inulinases from Kluyveromyces marxianus and Aspergillus niger form geterodimers and inulinases from tubers of Helianthus tuberosus are present as both dimers and monomers. The role of various forms in the functional activity of inulinase molecules is discussed.

Technology of formation for nanostructured magnetic materials on silicon substrate with a mean nanostructures size of similar to 25 nm and a narrow size distribution of these nanostructures was elaborated in the work. Single-domain magnetization character for some of the nanostructures was obtained. Completely optical magnetization of nanostructures was performed by circularly-polarized light at room temperature.

Electrophoretically homogenous preparations of malate dehydrogenase (MDH) isoforms of the bacteria Sphaerotilus natans D-507 with specific activity 7.46 U/mg and 5.74 U/mg with respect to protein concentration have been obtained. The dimeric isoform of the enzyme was shown to function under organotrophic growth conditions, whereas the tetrameric isoform was induced under mixotrophic cultivation conditions. PCR-analysis revealed a single gene encoding the malate dehydrogenase molecule. The topography of the MDH isoform surface was studied by atomic-force microscopy, and a 3D-structure of the enzyme was obtained. Spectraphotometric analysis data allowed us to suggest that stabilization of the tetrameric form of MDH is due to additional bounds implicated in the quaternary structure formation.

Получены в электрофоретически гомогенном состоянии препараты изоформ малатдегидрогеназы (МДГ) из бактерий Sphaerotilus natans Д-507 с удельной активностью 7.46 и 5.74 Е/мг белка. В условиях органотрофного роста бактерий функционирует димерная форма фермента, тогда как при миксотрофном культивировании индуцируется тетрамер. ПЦР-анализ позволил установить наличие одного гена, кодирующего малатдегидрогеназную белковую молекулу. С помощью атомно-силовой микроскопии исследована топография поверхности изоформ МДГ, получено трехмерное изображение молекул фермента. Использование спектроскопического метода позволило предположить, что участие дополнительных связей в формировании четвертичной структуры стабилизирует конформацию молекулы тетрамерной формы МДГ.

Thermal inactivation of the Kluyveromyces marxianus inulinase in a free form and immobilized on VION KN-1 cation exchange fiber was studied. Atomic force microscopy demonstrated an oligomeric structure of this enzyme, composed of two subunits differing in their size. It was assumed that the intersubunit contacts were destroyed at 60°C, and the inulinase molecule dissociated into two monomers located separately.

It has been found using a combination of atomic force microscopy with infrared spectroscopy, gel chromatography, and electrophoresis that inulinase from Kluyveromyces marxianus Y-303 has oligomeric structure, which includes two subunits differing in size, molecular mass, and catalytic activity. It has been shown that the division of the inulinase dimer into monomers leads to an increase in the number of irregular sites by 6% for subunit 1 (54.8 kDa) and by 10% for subunit 2 (8.4 kDa) compared with the native enzyme.