Nanotechnologies in Russia最新文献

Memristive structures of Ti/HfO₂/Au/c-Si, which are characterized by high ductility, are studied using the impedance spectroscopy method. Impedance hodographs are obtained for several stable resistive states. An equivalent circuit is proposed that takes into account the change in the resistance of filaments during their growth and allows for a good description of the observed changes in the type of the hodograph. Using simulation, the numerical values of the equivalent-circuit parameters are calculated. It is shown that during the switching process a significant change in the capacitance of the structure occurs. The data obtained allow us to better understand the processes that occur in such structures during switching, and open up the possibility of creating elements in which both resistance and capacitance can be controllably changed simultaneously.

We report a comprehensive investigation of Cu(II) and Pb(II) ion sorption kinetics on magnetically functionalized Ti₃C₂T_x MXene composites. The composite material was synthesized by functionalizing multilayer MXenes with iron oxide nanoparticles through a co-precipitation method, resulting in a magnetic sorbent with a saturation magnetization of 32 ± 3 A m²/kg. The experimental data were analyzed using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The sorption process for both metal ions followed pseudo-second-order kinetics (R² > 0.99), with activation energies of –61.5 and ‒24.8 kJ/mol for Cu(II) and Pb(II), respectively. The analysis revealed that Cu(II) sorption involves both chemical interactions with functional groups and diffusion processes, while Pb(II) sorption is primarily diffusion-controlled. External diffusion rates were found to be an order of magnitude higher than internal diffusion rates for both metal ions, suggesting that the 2D structure of MXenes may influence the intraparticle diffusion of heavy metals. The magnetic functionalization enables efficient separation of the sorbent after treatment, making this composite material promising for heavy metal removal applications in water treatment processes.

The effects of copper oxide nanoparticle solutions stabilized by nonionic surfactants (Tween 20 and Triton X100) and polyhexamethylene biguanide (PHMB) on various stages of clonal micropropagation of white poplar × aspen plants (Populus alba × Populus tremula) in culture in vitro are discussed. The use of stabilized nanoparticles at a concentration of 5 mg/L in the Murashige–Skoog culture medium at the stage of introduction into the culture in vitro allows an increase in the yield of sterile viable explants by 16.7–26.7%. During the multiplication stage, the positive effect of nanopreparations is noted by the multiplication coefficient. The maximum value of this indicator (3.3) was obtained for 5 mg/L nanoparticles stabilized with PHMB (compared to 2.6 in the control). For stimulating root formation in poplar microshoots, media with the addition of copper oxide nanoparticles stabilized by Triton X100 and Tween 20 turned out to be optimal. An increase in the number of rooted shoots by 10% and the number of roots per shoot by up to 46% is experimentally confirmed.

Two-dimensional MXene materials are attracting attention as nanoadsorbents for the removal of heavy metals from aqueous media. The adsorption properties of the magnetic composite Ti₃C₂T_x/Fe₃O₄ are investigated in relation to Fe(III) ions. It is found that the sorption capacity is 64.5 mg/g at a composite concentration of less than 10 mg/L. The kinetics of sorption is best described by a pseudo-second-order model, which indicates a chemical interaction between the sorbent and the sorbate. The calculated conditional activation energy (–17 kJ/mol) confirms that the sorption rate is limited by the diffusion stage. The magnetic characteristics of the composite provide the possibility of effective magnetic separation of the material after sorption.

Complexes of block copolymers of poly-2-ethyl-5,6-dihydrooxazine and poly-2-isopropyl-5,6-dihydrooxazine with curcumin have been prepared. The binding constants were determined, the high values of which indicate a strong binding of curcumin to the block copolymers. Self-organization in aqueous solutions of the obtained complexes was studied by light scattering and turbidimetry. It has been shown that on heating one phase transition was observed in the complex solutions. Concentration dependences of the phase separation temperature have been determined. It has been established that the phase separation temperature increases by 2–4°C on passage from block copolymer solutions to solutions of the complexes.

Grafted copolymers based on natural polysaccharides are interesting from the standpoint of creating targeted drug delivery systems. The properties of graft copolymers of pullulan with side chains of poly(2-methyl-2-oxazoline) and poly(2-ethyl-2-oxazoline) are studied. The conformational and hydrodynamic characteristics of the indicated polymers, such as the coefficient of translational diffusion, characteristic viscosity, molecular weight, equilibrium rigidity, and hydrodynamic diameter of chains, are determined using nuclear magnetic resonance, dynamic light scattering, analytical ultracentrifugation, viscometry, and a number of combined techniques. Increase of the value of equilibrium rigidity of grafted polymers with poly(2-oxazoline) side chains was detected.

The work presents and describes various mechanisms for the formation of a conductive channel in bipolar memristors of the vacancy and ionic types: in the first case, due to the generation and growth of conductive threads, and in the second, due to segregation processes with the formation of spatial associations of ions from the material of the active electrode. The current—voltage characteristics for both types of memristors are presented and a comparison of the design features of these memristors is conducted.

The paper focuses on developing, manufacturing, and testing a two-dimensional X-ray focusing device based on silicon planar compound refractive lenses. Using compound refractive lenses installed in cross geometry one after another along the optical axis allows for generating a beam with specified parameters. A distinctive feature of the developed device is the ability to correct astigmatism of the optical system. Two-dimensional focusing of X-ray radiation with astigmatism correction was experimentally demonstrated at the RKFM beamline “KISI–Kurchatov.” The resulting focused X-ray beam, characterized using the knife-edge technique, had a size of approximately 1.5 µm, with equal dimensions in both the vertical and horizontal directions. The experimental results were compared with theoretical estimates and computer simulations.

The use of microneedles for discrete and continuous monitoring and correction of the body’s state is a progressive direction in personalized medicine. The desire to minimize the adverse effects of invasive diagnostic methods and increase the effectiveness of pharmacotherapeutic interventions determines the intellectualization of microneedles, their designs, and technologies of use. Microneedles and their arrays are presented as complex functional microsystems, the creation of which is based on the use of microtechnology and nanotechnology processes, as well as heterogeneous organic–inorganic compositions.

The pulsed laser ablation of targets is a promising direction for creating metal nanoparticles that are widely used in various fields of science, technology, and for biomedical applications. To improve laser technologies, it is necessary to control the ablation process, ensuring the necessary size distribution of the resulting nanoparticles, which is often bimodal. The work proposes an approach that allows one to estimate the mass of the nanoparticle fraction during laser ablation with short pulses from a scanning electron microscopy (SEM) image or microphotograph of holes in a metal film. The investigation is carried out using nanosecond laser pulses and gold films 50 nm in thickness.