Nanotechnologies in Russia最新文献

Тhe efficiency and the performance of membrane electrode assemblies (MEAs) of the anion exchange membrane (AEM) water electrolyzer is determined to a significant degree by the properties of the materials used as porous transport layers (PTLs). Due to the high surface roughness, porosity, and pore size, the direct use of Ni foam as an electrode material is difficult, and its preliminary compression is required, which irreversibly affects the electrode structure. In the presented work, the effect of Ni foam compression on the structure of an electrode based on it, as well as on the AEM water electrolyzer MEA is considered, including the distribution of voltage losses. The effect of the compression degree on the Ni-foam electrode structure and the performance of the AEM water electrolyzer MEA is considered. The optimal electrode compression provides a significant decrease in the loss of microporous layer particles and catalyst layer nanoparticles in deep surface voids of the PTL, and the development of an interface between the nanostructured catalyst layer and the electrode.

Тhe results of the heterophase interaction of nanoparticles of refractory phases with iron melts containing harmful impurities (sulfur, antimony, tin, and copper) are studied and generalized. It is shown that the degree of the removal of impurities (~0.05 wt %) in the Fe–S, Fe–Sn, Fe–Sb, and Fe–Cu systems after the introduction of nanoparticles ranges from 10 to 37 rel %. As a result of the interaction of nanoparticles with impurities of the metal melt, the formation of ensembles with new surface properties is proposed. It is shown that the redistribution of ensembles in the melt and their removal to the phase interface can be represented as a two-stage process.

Нafnium oxide is currently considered one of the most promising metal-oxide materials for creating memristive structures. Memristive structures find their application in many areas of science and technology; for example, with their help, the biosimilar emulation of synapses in neuromorphic computing systems is possible. One of the important obstacles to the industrial use of memristors is the variability of resistive switching. Nonstoichiometry in memristor structure can be an important tool for controlling resistive switching. Therefore, in this work, memristors based on hafnium oxide in a metal–insulator–metal sandwich structure are synthesized by electron-beam deposition, which makes it possible to create nonstoichiometric films. The effect of resistive switching is studied depending on the material of the upper electrode and the thickness of the hafnium-oxide layer. The synthesis parameters are determined to achieve a balance between the main memristive characteristics.

Abstract

The influence of the hydroxyl group in the aglycone of the antitumor antibiotic doxorubicin on the spectrophotometric and dimensional characteristics of nanocomplexes of doxorubicin–polyvinylpyrrolidone–selenium nanoparticles is established. The involvement of components of ternary complexes in intermolecular interactions is assessed using the spectrophotometric method. The radii of gyration (40–60 nm) and hydrodynamic radii (20–70 nm) of the synthesized nanocomplexes are determined using static- and dynamic-light scattering methods. The hydroxyl group present in the structure of the antitumor antibiotic contributed to the formation in an aqueous environment of a more loose, permeable shell of the nanocomplex compared to the daunomycin–polyvinylpyrrolidone–selenium nanoparticles nanocomplexes. An increase in the Se concentration during the synthesis of nanocomplexes leads to expansion of the loose shell. The revealed patterns will further contribute to the development of methods for synthesizing nanocomplexes for the modification of water-soluble antitumor antibiotics.

Abstract

A comparative analysis of the microstructure and electrochemical behavior of platinum–carbon electrocatalysts containing 20 and 40% platinum from different manufacturers for fuel cells with a proton-exchange membrane is carried out. The degree of degradation of the catalysts during accelerated stress testing in laboratory conditions is assessed based on the results of not only residual functional characteristics, but also microstructural parameters after electrochemical tests. It is determined that 20 and 40% PM series catalysts contain smaller platinum nanoparticles, characterized by a narrower size and more uniform spatial distribution, compared to analogues of the HiSPEC series. Due to these microstructural features, a PM-series platinum–carbon catalysts are characterized by a higher electrochemically active surface area (EASA) and mass activity values initially and after stress testing.

Тhe search for new materials with high conductivity and biocompatibility for use in biosensors is an important task. One promising material is bacterial cellulose (BC) due to its high surface area, high porosity, and biocompatibility. In this study, bacterial cellulose is modified with the PEDOT:PSS conductive gel and carbon nanomaterials to increase conductivity. Thermally expanded graphite/BC/PEDOT:PSS/graphene composition is used to immobilize Gluconobacter oxydans acetic-acid bacteria on the surface of a screen-printed carbon electrode. The effect of individual components of the composite on the catalytic activity of bacteria in the presence of 2,6-dichlorophenolindophenol redox mediator is studied. The addition of BC to the composition provides a higher stability of the electrode: the drop in signal within 35 days is 9%. A microbial biosensor based on TEG/PEDOT:PSS/Graphene/BC/G. oxydans composite show better sensitivity (36.4 µA mM^–1 cm^–2) and lower detection limit (0.005 mM) as well as the widest linear detection range (0.005–2 mM) compared to the other compositions. Thus, bacterial cellulose modified with conductive additives can be applied as a matrix for the immobilization of bacteria in microbial biosensors and microbial fuel cells.

Abstract

Preparations based on silybin are used as hepatoprotectors in the treatment of liver lesions of various etiologies. The main disadvantage limiting their use is low bioavailability associated with the low solubility of silybin in water. To solve this problem, numerous delivery systems are created that increase its solubility, including those based on biodegradable polymers. This study presents a method for producing a polymer composition containing silybin (PCS) based on copolymers of lactic and glycolic acids. The content of the active ingredient in the product is 5%, its entrapment efficiency in particles is more than 90%; the Z-average particle size in an aqueous suspension is about 200 nm, the polydispersity index is less than 0.2, and the zeta potential is from ‒1 to ‒5 mV. The high antioxidant activity of silybin in the polymer composition by galvanostatic coulometry, as well as in the reaction of the nonenzymatic autoxidation of adrenaline, is shown. In an in vivo study on a model of acute toxic hepatitis induced by carbon tetrachloride, the more pronounced hepatoprotective effect of PCS is found compared with free silybin.

Тhis work suggests ways to improve the bioavailability of low-solubility drugs by precipitation from solutions in universal solvents on nanostructured surfaces including nanoparticles (NPs) such as SiO₂ and Fe₃O₄. The same effect is found on metal-polymer composites containing Co, Ni, and Fe obtained from unsaturated dicarboxylates. In both cases, this is achieved by increasing the total desorption surface. The examples of resveratrol and of the preparation of the sum of furocoumarins Ammifurin show an increase of the relative desorption ratio of drugs by two orders of magnitude from the surface of nanostructured CaCO₃ particles into aqueous solutions. The results of MTT tests show the comparable effects of Ammifurin and of the used metal-polymer nanocomposites on HeLa cervical cancer cells and human HepG2 liver carcinoma, thereby making their combined use potentially possible. Thus, we propose a way to improve the bioavailability of a wide class of drugs, potentially applicable for all cases when the toxicity of the carrier NPs does not exceed the independent toxicity of the target substance. The possibility of the mutual enhancement of toxicity requires a separate study and is not considered here.

Abstract

Remagnetization processes of amorphous glass-coated microwires have been studied using First Order Reversal Curve (FORC) analysis. This method allows us to study the magnetostatic interactions in these samples. The number, shape, size, and location of the peaks in the FORC diagram can provide information about the different remagnetization processes of the microwires and their system. The sign of magnetostriction of the sample strongly influences the type of FORC diagram. The remagnetization process also depends on the mechanical stresses at the ends of the Fe-based microwire. This dependence tends to zero with increasing wire length. For Co-based samples, the effect of the demagnetization factor on the FORC diagram has been described. In addition, the magnetostatic interactions for a system of densely packed microwires with positive magnetostriction are visualized in this work.

Abstract

The large-scale commercialization of polymer electrolyte membrane (PEM) water electrolyzers is still constrained by their high capital cost, which is largely associated with the use of noble metal-based electrocatalysts. There is an urgent need to reduce their loading in the composition of electrocatalytic layers. In the present work, an approach of the microporous sublayer made of titanium nitride (TiN_x) and formed over the anode surface by magnetron sputtering is proposed. It contributes to an increase in the anode electrocatalyst utilization, opening up wide possibilities to reduce its loading.