New Publications

https://doi.org/10.1080/00150193.2024.2305092

The article presents the results of studies of theBaMg_1/3Ta_2/3O₃ (BMT) complex perovskite crystal using Raman spectroscopy and density functional theory (DFT) calculation. The polarized Raman spectra of a cubic BMT single crystal are obtained in two different geometries in a broad temperature range (5–580 K). The density functional theory calculations of the lattice dynamics and vibrational spectra of the BMT crystal in the Г point of the trigonal phase are carried out. The simulated Raman spectra are analyzed in comparison with the experimental spectra of cubic single crystals and those of ceramics in the trigonal phase. The Raman spectra peculiarities are observed and explained.

https://doi.org/10.1080/00150193.2024.2305091

BaMg_1/3Ta_2/3O₃ (BMT) crystals belong to the family of complex perovskites and are well known for their excellent microwave dielectric properties. In this work, structural optimization of the lattice parameters was performed. Electron density functional theory calculations of the electronic band structure of BMT crystal of the trigonal phase were carried out along Г–A–K–M–L directions of the Brillouin zone. The calculated band gap energy was 3.554 eV. The partial density of states of BMT crystal in P-3 m1 phase was simulated. Top of the valence band was formed by 2p-states of O and bottom of the conduction band – by 5d-states of Ta.

https://doi.org/10.3390/s24196308

Multilayered [Cu(3 nm)/FeNi(100 nm)]₅/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/FeNi(10 nm)/Cu(150 nm)/[Cu(3 nm)/FeNi(100 nm)]₅ structures were obtained by using the magnetron sputtering technique in the external in-plane magnetic field. From these, multilayer magnetoimpedance elements were fabricated in the shape of elongated stripes using the lift-off lithographic process. In order to obtain maximum magnetoimpedance (MI) sensitivity with respect to the external magnetic field, the short side of the rectangular element was oriented along the direction of the technological magnetic field applied during the multilayered structure deposition. MI sensitivity was defined as the change of the total impedance or its real part per unit of the magnetic field. The design of the elements (multilayered structure, shape of the element, etc.) contributed to the dynamic and static magnetic properties. The magnetostatic properties of the MI elements, including analysis of the magnetic domain structure, indicated the crucial importance of magnetostatic interactions between FeNi magnetic layers in the analyzed [Cu(3 nm)/FeNi(100 nm)]₅ multilayers. In addition, the uniformity of the magnetic parameters was defined by the advanced technique of the local measurements of the ferromagnetic resonance field. Dynamic methods allowed investigation of the elements at different thicknesses by varying the frequency of the electromagnetic excitation. The maximum sensitivity of 40%/Oe with respect to the applied field in the range of the fields of 3 Oe to 5 Oe is promising for different applications.

https://doi.org/10.1111/jace.20155

Despite being the key component in modern electronic devices or power systems, ceramic dielectric capacitors have drawbacks like low energy storage density and efficiency that limit their extensively wide application. This work adopted a different route to improve energy storage performance compared with the frequently utilized composition modification. 0.98Ba_0.65Sr_0.245Bi_0.07TiO₃-0.02Ce Pb-free ceramics with different polyvinyl alcohol (PVA) contents were prepared through viscous polymer processing. The rheological and energy-storing performance were systematically studied. It can be seen that high PVA content results in more pores and larger grain sizes that will deteriorate the breakdown strength of ceramics. The highest breakdown strength reached 420 kV/cm while the concentration of PVA was 5 wt%. The mechanism of grain sizes on breakdown strength is studied by electrical tree simulation based on COMSOL. Viscous polymer processing with proper PVA content is very effective in generating dense and homogenous structures. Finally, the ceramic with 5 wt% PVA possesses a high density of up to 4.41 J/cm³ and an efficiency of about 84.21% at 420 kV/cm. Simultaneously, this ceramic improved stability of both temperature (30–150°C) and frequency (1–300 Hz) at 350 kV/cm, while the η kept above 90% and W_rec exceeding 3.6 J/cm³.

https://doi.org/10.1080/01431161.2024.2408036

In this paper, the changes in the character of time shapes, amplitudes, frequency spectra, and time delay of ultra-wideband (UWB) impulses (duration of 0.33 ns) reflected from the layer of wet sand with a rough upper boundary were investigated. It was shown that the attenuation of UWB impulse amplitude, which is reflected from the upper rough boundary of the sand layer, can be described by the model of Fresnel reflection coefficient for a smooth surface using the Gaussian correction factor (FRGC). At this root-mean-square (RMS), height of soil surface roughness was in the range of ~0–21 mm, but the determination coefficient and RMS error (RMSE) were found to be equal to 0.94 and 0.02, respectively. An experiment close to linear increase/decrease in the propagation time of impulses reflected from the upper/lower boundary of the layer, respectively, was found with increasing the RMS heights of upper boundary. It is shown that the propagation time of such impulses can be described by the modified FRGC model with an error from RMSE = 0.09 ns to RMSE = 0.15 ns. The results of these findings are of practical importance for the interpretation of remote sensing data for precise soil moisture measurements from unmanned aerial vehicle platforms using UWB impulses.

https://doi.org/10.48550/arXiv.2408.16203

The relation of the magnetically dead layer and structural defects in ultrafine interacting NiFe2O4 nanoparticles (<d> = 4 nm) have been investigated using transmission electron microscopy, X-ray diffraction, ^57Fe Mössbauer spectroscopy, and dc magnetization and ac susceptibility measurements. According to the magnetic data, we found out three magnetic subsystems in NiFe2O4 nanoparticles. The first one with the lowest blocking (spin freezing) temperature (TS = 8 K) established by atomic magnetic moments of magnetically disordered particles with the d < 4 nm. The other two subsystems are formed by the magnetic moments of the "core" of nanoparticles having size more than 4 nm and correlated surface spins in nanoparticle clusters, correspondingly. Magnetic moments of ferrimagnetically ordered "core" are blocking at a higher temperature ( \approx 40 K). It has been shown that the most significant contribution to the energy dissipation is made upon blocking of the correlated nanoparticle surface spins from the magnetically dead layer on the nanoparticles' surface. By the magnetic data, the thickness of this layer is dmd \approx 1 nm for a particle with the <d> \approx 4 nm. At the same time or meanwhile, the ^57Fe Mössbauer spectroscopy has revealed a structural disorder penetrating to a depth of up to dcd \approx 0.6 nm in a particle with <d> = 4 nm. This evidences for a faster destruction of the magnetic order as compared with the crystal order upon moving away from the center of a particle to its periphery.

https://doi.org/10.1134/S1063784224070041

Study of the mechanisms of the solid-state reactions in Sn/Fe/Cu thin films is interesting both from a fundamental point of view and from a view of the importance of emerging intermetallics in the technology of solder joints and thin-film lithium-ion batteries. By the integrated approach, including both X-ray phase analysis and local elemental analysis of the cross-sections of the films, the phase composition and the mutual arrangement of phases were studied, at various stages of the solid-state reaction occurring at different temperatures. The observed sequence of the appearing phases differs significantly from the expected one if the mass transfer took place by a volume diffusion through the forming layers.

https://doi.org/10.1007/s10854-024-13521-4

The magnetic, transport and acoustic properties of materials Tm_XMn_1−XSe (0.025 ≤ X ≤ 0.2) have been studied in magnetic fields of up to 12 kOe at temperatures of 80‒600 K. The magnetic phase transition temperatures (T_N) and change in the sign of resistance at DC current in vicinity of the T_N were established. The temperature and concentration ranges corresponding to the maximum magnetoresistance (− 50% for X = 0.025) and magnetoimpedance (12% for X = 0.2) have been determined. The mechanism of relaxation has been established from the impedance spectrum and the activation energy change upon temperature and concentration has been found. The difference between the dc and ac magnetoresistances has been disclosed. The concentration range with hole and electron type carriers is determined. The mobility anomalies in the vicinity of the valence transition have been established. It is shown that the current and electrical resistance in the Tm_XMn_1−XSe compound can be manipulated by ultrasound and a magnetic field. A qualitative difference between the interaction of current and ultrasound in the magnetically ordered and paramagnetic regions is found

https://doi.org/10.1016/j.solidstatesciences.2024.107703

Calorimetric, dilatometric and pressure studies of (NH₄)₃WO₂F₅ were performed over a wide temperature range, including the Pm-3m ↔ Pa-3 phase transition. Comparison of the obtained results with data for related fluorides (NH₄)₃SnF₇ and (NH₄)₃TiF₇ undergoing the same structural changes showed a significant role of chemical pressure in the formation of thermal and barocaloric properties. A decrease in anomalous entropy in oxyfluoride, ΔS₀ = 12.2 J/mol·K, is accompanied by a significant increase in sensitivity to hydrostatic pressure, dT₀/dp = 93 K/GPa, the preservation of a large change in anomalous deformation δ(ΔV/V)₀ = 0.45 % and a small temperature hysteresis, δT₀ < 1 K. This combination of thermal characteristics has led to both a significant increase in extensive and intensive barocaloric parameters in the low pressures area, and to their high reversibility in the modes of increasing and decreasing pressure.

 https://doi.org/10.1002/lpor.202401089

DOI: 10.18083/LCAppl.2024.3.71

The magnetic susceptibility and diamagnetic anisotropy of the mixtures of nematic 5CB with chlorophyll a (Chl. a), chlorophyll b (Chl. b) and carotenoids, which were synthesized in the form of extracts, with different concentrations of components have been studied. The pigments were extracted from finely ground powder of air-dried biomass of the aquatic plant Ceratophyllum demersum L., grown from a laboratory culture. The probable configuration of the molecules of substances in a magnetic field was considered. Taking into account the orientational features of the liquid crystal 5CB, the expressions for the diamagnetic anisotropy of its mixtures with various extracts were derived. Using the Faraday method, with the direct measurement of the force acting on a mixture in a magnetic field, the dependences of longitudinal and transverse components of the magnetic susceptibility and diamagnetic anisotropy of the mixtures on temperature were obtained. The amplitude differences in the temperature dependences of diamagnetic anisotropy for various mixtures were analyzed. The influence of currents in benzene rings of the liquid crystal and in conjugated aromatic porphyrin macrocycles, as well as in aliphatic chains of organic molecules on diamagnetic anisotropy was estimated

 https://doi.org/10.3390/met14090991

The present study considers the samples of an Ti-6Al-4V alloy obtained by selective laser melting with the addition of a 10% Cu-Al powder mixture. The microstructure, elemental composition and phase composition, as well as the physico-chemical properties, have been investigated by the methods of electron microscopy, X-ray phase analysis, and bending testing. The obtained samples have a relative density of 98.5 ± 0.1%. The addition of the Cu-Al powder mixture facilitates supercooling during crystallization and solidification, which allows decreasing the size and changing the shape of the initial β-Ti grains. The constant cooling rate of the alloy typical for the SLM technology has been shown to be able to prevent martensitic transformation. The formation of a structure that consists of β-Ti grains, a dispersed eutectoid mixture of α-Ti and Ti₂Cu grains, and a solid solution of Al in Cu has been revealed. In the case of doping by the 10% Cu-Al mixture, the physico-mechanical properties are improved. The hardness of the samples amounts to 390 HRC, with the bending strength being 1550 ± 20 MPa and deformation of 3.5 ± 0.2%. The developed alloy can be recommended for applications in the production of parts of jet and car engines, implants for medicine, and corrosion-resistant parts for the chemical industry.

https://doi.org/10.1016/j.optmat.2024.116135

The photoluminescence and UV–Vis absorption spectra of copolyamides containing 1,9-anthrazoline with para- and meta-[(substituted carbonyl)amino]phenyl-1-ene moieties in a polymer backbone were studied by a combination of experimental and theoretical approaches. The investigation was accomplished through time-dependent density functional theory electronic structure calculations of small-molecule models mimicking a polymer chain. Theoretical absorption and luminescence spectra of ten atomistic models were compared with corresponding experimental data, and the optical properties of two new luminescent molecules with bromine auxochrome were predicted. An analysis of the optical properties demonstrate an identical effect of the type and position of a substituent on the spectra for para- and meta-[(substituted carbonyl)amino]phenyl-1-ene moieties. It was found that the absorption and luminescence spectra of theoretical para-models demonstrate red shifts relative to the corresponding meta-ones. The same phenomenon was observed in experimental spectra of low-molecular-mass compounds and corresponding copolyamides in solution and bulk. Unique optical properties allow anthrazoline-based polymer compounds to be used in numerous advanced optoelectronic applications with desired optical and electronic characteristics.

https://doi.org/10.1021/acs.chemmater.4c01851

This work addresses a comprehensive study of six new complexes of the constitution [Ln(MeDPQ)₂Cl₃] (Ln³⁺ = Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, and Y³⁺; MeDPQ─2-methyldipyrido-[3,2-f:2′,3′-h]-quinoxaline) with good thermal stability up to 446 °C. Statistical substitution of Sm³⁺, Tb³⁺, Gd³⁺, and Dy³⁺ with a second Ln³⁺ ion led to [Ln_1–xLn′_x(MeDPQ)₂Cl₃] solid solutions, which exhibit temperature-dependent luminescent properties. Their visible emission and intensity ratios of transitions vary with temperature in the range of 253–353 K. In the case of the composition [Tb_1–xEu_x(MeDPQ)₂Cl₃], the maximum relative thermal sensitivity S_r values were determined as 3.77% K^–1, 3.97% K^–1, and 3.97% K^–1 for x(Eu³⁺) = 0.01, 0.05, and 0.1, respectively. The compositions [Dy_1–xEu_x(MeDPQ)₂Cl₃] and [Tb_1–xSm_x(MeDPQ)₂Cl₃] also showed significant performance. For the pair Dy³⁺–Eu³⁺, the S_r values were determined as 3.88%K^–1, 3.91% K^–1, and 3.80% K^–1 for x(Eu) = 0.01, 0.05, and 0.1, respectively. For the pair Sm³⁺–Tb³⁺, the S_r values are 3.28% K^–1 and 3.82% K^–1 for x(Sm) = 0.9 and 0.1, respectively. The largest thermal sensitivity value S_r of 4.11% K^–1 was achieved for the composition [Gd_0.8Tb_0.18Eu_0.02(MeDPQ)₂Cl₃]. In addition, patterns of thermometric performance are bound to the energy transfer efficiency Tb³⁺ → Eu³⁺, Dy³⁺ → Eu³⁺ → Dy³⁺, and Tb³⁺ → Sm³⁺, as this characteristic is strongly temperature-dependent in the studied range.

https://doi.org/10.1016/j.ceramint.2024.09.268

Solid-state synthesis is widely used in exploratory research to study various structural modifications that affect the properties (critical temperature, critical current density, irreversibility field, etc.) of superconductors. The popularity of this method is due to its relative simplicity and availability of the necessary equipment. Combining solid-state synthesis and top-seeded melt growth allows us to increase the grain size in a Tm- and Nd-based 1-2-3 superconductor. Samples with a grain size up to 0.1 mm have been obtained. X-ray diffraction, scanning electron microscopy and magnetization measurements have been used for investigating this superconducting material. The magnetization width ΔM has increased significantly in the synthesized samples. However the temperature dependence of the intragrain critical current density and the pinning force scaling give evidences that the pinning mechanism in the obtained superconductor is essentially the same as in polycrystalline superconductors synthesized by standard solid-state technology. The increase in grain size in the synthesized samples is the main reason for the high values of ΔM

https://doi.org/10.1007/s10854-024-13521-4

The magnetic, transport and acoustic properties of materials Tm_XMn_1−XSe (0.025 ≤ X ≤ 0.2) have been studied in magnetic fields of up to 12 kOe at temperatures of 80‒600 K. The magnetic phase transition temperatures (T_N) and change in the sign of resistance at DC current in vicinity of the T_N were established. The temperature and concentration ranges corresponding to the maximum magnetoresistance (− 50% for X = 0.025) and magnetoimpedance (12% for X = 0.2) have been determined. The mechanism of relaxation has been established from the impedance spectrum and the activation energy change upon temperature and concentration has been found. The difference between the dc and ac magnetoresistances has been disclosed. The concentration range with hole and electron type carriers is determined. The mobility anomalies in the vicinity of the valence transition have been established. It is shown that the current and electrical resistance in the Tm_XMn_1−XSe compound can be manipulated by ultrasound and a magnetic field. A qualitative difference between the interaction of current and ultrasound in the magnetically ordered and paramagnetic regions is found.

https://doi.org/10.1007/s00339-024-07921-w

ZnO films grown on a glass substrate through the magnetron sputtering were subjected to ion implantation of Ni⁺ and Ag⁺with different irradiation doses. The resulting ZnO: Ag and ZnO: Ni films were studied using optical and magneto-optical spectroscopy. Magnetic circular dichroism (MCD) spectra for the samples were analyzed along with MCD spectra for nickel and silver nanoparticles (NPs). The MCD data for Co-doped ZnO films was also considered. It has been found that MCD spectrum shape reflects different polarization states of charge carriers in the samples, as well as their magnetic behavior. In addition, it has been established that MCD spectroscopy can serve as a tool for the detection of Ni and Ag nanoparticles in matrices of ZnO: Ni and ZnO: Ag solid solutions. The general pattern of the MCD spectra observed for doped ZnO films in various magnetic and polarized states is expected to apply to other dilute oxides.

https://doi.org/10.1016/j.jallcom.2024.176577

There is an urgent need to develop stable and high-energy storage dielectric ceramics; therefore, in this study, the energy storage performance of Na_0.5-xBi_0.46-xSr_2xLa_0.04(Ti_0.96Nb_0.04)O_3.02 (x = 0.025–0.150) ceramics prepared via the viscous polymer process was investigated for energy storage. It was found that with increasing Sr²⁺ content, the material transforms from a mixture of rhombohedral and tetragonal phases (x = 0.025) to a mixture of orthorhombic and pseudo-cubic phases (x = 0.15). The emergence of a dielectric plateau for the sample with x = 0.15 widens the applicability of the host compound. Finite element simulations show that a smaller grain size has a beneficial effect on the critical breakdown electric field and that the relaxor transformation benefits from the reduction of residual polarization (P_r). The obtained ceramics achieve a value of 6.69 J/cm³ for the energy storage density (W_rec) and 89.48 % for the energy storage efficiency (η) under an applied electric field of 400 kV/cm, with a discharge time (t_0.9) of 0.168 μs at 90 % of the energy under an electric field of 280 kV/cm, and a power density (P_d) of 148 MW/cm³. This study shows a novel strategy for the modification of the dielectric and ferroelectric properties of NBT-based ceramics, providing an effective way to expand the operational temperature range and improve energy storage performance.

https://doi.org/10.1557/s43578-024-01442-1

Magnetic properties of mixed spinel ferrites are determined, in great extent, by the magnetic cation distribution among tetrahedral and octahedral positions in a crystal. In the case of CoZn-ferrites, most researchers reported a predominant localization of the divalent cobalt ions in octahedral positions. Using the citrate precursor auto-combustion method, we successfully synthesized Co_xZn_1-xFe₂O₄ nanoparticles (x changed from 0.0 to 0.5) with an approximately evenly distribution of Co²⁺ ions between these interstitial positions. Fe³⁺ ions are localized preferably in octahedral positions. This type of 3d-ion distribution predetermined the combination of the large saturation magnetization and very low coercive field of the nanoparticles, which may be of importance for applications. MCD spectra of Co_xZn_1-xFe₂O₄ nanoparticles are studied here for the first time. Revealed intense MCD peak at 1.75 eV corresponds to the emission wavelength (710 nm) of some lasers, e.g., ALP-710 nm (NKT Photonics, Denmark) which may be of interest for photonic devices.

DOIhttps://doi.org/10.1039/D4CP00778F

Plasmonics serves as a most outstanding feature of nanoparticle technology and is nowadays used in numerous applications within imaging, sensing and energy harvesting, like plasmonically enhanced solar cells, nanoparticle bioimaging, plasmon-controlled fluorescence for molecular tracking in living cells, plasmon-controlled electronic molecular devices and surface enhanced Raman spectroscopy for single molecular detection. Although plasmonics has been utilized since ancient times, the understanding of its basic interactions has not been fully achieved even under the emergence of modern nanoscience. In particular, it has been difficult to address the “ultra-fine” 1–10 nm regime, important for applications especially in bioimaging and biomedical areas, where neither classical nor quantum based theoretical methods apply. Recently, new approaches have been put forward to bridge this size gap based on semi-empirical discrete interaction models where each atom makes a difference. A primary aim of this perspective article is to review some of the most salient features of these models, and in particular focus on a recent extension – the extended discrete interaction model (Ex-DIM), where the geometric and environmental features are extended – and highlight a set of benchmark studies using this model concerning size, shape, material, temperature dependence and other characteristics of ultra-fine plasmonic nanoparticles. We also analyze new possibilities offered by the model for designing ultra-fine plasmonic particles for applications in the areas of bioimaging, biosensing, photothermal therapy, infrared light harvesting and photodetection. We foresee that future modelling activities will be closely connected to collaborative experimental work including synthesis, device fabrication and measurements with feedback and validation in a systematic fashion. With this strategy we can expect that modelling of ultra-fine plasmonics particles can be integrated in the development of novel plasmonic systems with unprecedented performance and applicability.

https://doi.org/10.1080/1536383X.2024.2400270

It was shown that the method of mechanical separation with filtration could be used to separate metal nanoparticles in a carbon shell. The method was used for separation of FeNi nanoparticles with a carbon shell, previously isolated from carbon condensate by boiling in acids. The particles had a crystalline structure and magnetic characteristics (Mr/Ms = 0.30, Hc = 270 Oe). Method of mechanical separation with filtration made it possible to separate the sample into particles coated with a carbon shell (particles size 40–50 nm, size of the metal core 10–15 nm), and into metal particles with a diameter of 6–15 nm, dispersed in a carbon matrix. The work shows that the samples have similar magnetic properties (Mr/Ms = 0.27, Hc = 236 Oe) and chemical composition (Ni ∼ 10 wt.%, Fe ∼ 12 wt.%, C ∼ 57 wt.%). However, the samples differ in structure, one contains FeNi(220), FeNi(200), FeNi(111) and C(002) phases, while the other contains only FeNi(200) and C(002) phases.

https://doi.org/10.33383/2024-011

Experimental photo-biological studies have been carried out to find effective stable spectral PAR fluxes for cultivating tomato seedlings and to estimate the effect of the change in the spectral irradiation mode during the growing season under electrical light.
The purpose of the study was to test the capabilities of the newly developed LED irradiators with an adjustable PAR radiation spectrum to estimate the effectiveness of spectral irradiation modes to treat tomatoes for the formation of high-quality seedlings and to increase tomato yields by changing the PAR radiation spectrum during the plant flowering stage under electrical light.
The study showed that for the formation of high-quality seedlings with a well-developed photosynthetic apparatus and a well-formed habitus, the most favourable was the PAR spectrum with proportions of blue (400–500) nm and red (600–700) nm rays of about 30 % and green (500–600) nm – about 40 % in a three-component PAR flux.
The change of the spectral irradiation mode during the stage of mass fruiting of tomato plants grown for fruit production, namely, an increase in the proportion of radiation in the red (600–700) nm spectral region by 15 % at the expense of the green (500–700) nm spectral region, caused tomato fruits to ripen 20 days earlier. Parameters of the biochemical composition of the fruits (carbohydrate and vitamin C contents) were also higher in the treatment with the change of spectrum. The experiments demonstrated that by changing the spectrum of the prototypes of the phosphor LED irradiators with the adjustable spectrum in certain stages of plant growth, these irradiators could be effectively used to cultivate long-season crops (for example, tomatoes).
The results obtained can be used to select spectral irradiation modes for producing greenhouse tomato seedlings and growing fruit-bearing tomato plants under electrical light in northern regions and in isolated spaces in various climatic zones using “City-farm” technologies.

https://doi.org/10.1016/j.solidstatesciences.2024.107703

Calorimetric, dilatometric and pressure studies of (NH₄)₃WO₂F₅ were performed over a wide temperature range, including the Pm-3m ↔ Pa-3 phase transition. Comparison of the obtained results with data for related fluorides (NH₄)₃SnF₇ and (NH₄)₃TiF₇ undergoing the same structural changes showed a significant role of chemical pressure in the formation of thermal and barocaloric properties. A decrease in anomalous entropy in oxyfluoride, ΔS₀ = 12.2 J/mol·K, is accompanied by a significant increase in sensitivity to hydrostatic pressure, dT₀/dp = 93 K/GPa, the preservation of a large change in anomalous deformation δ(ΔV/V)₀ = 0.45 % and a small temperature hysteresis, δT₀ < 1 K. This combination of thermal characteristics has led to both a significant increase in extensive and intensive barocaloric parameters in the low pressures area, and to their high reversibility in the modes of increasing and decreasing pressure.

https://doi.org/10.1016/j.cjph.2024.08.018

The all-dielectric germanium nanohole (GNH) metasurface with a sub-wavelength thickness supports simultaneous excitation of quasi bound state in the continuum (BIC) and super radiant mode. By selecting the different hole depths in a germanium slab, we present a trade-off metasurface between high Q-factor and high absorption in the photonic system. The presented device demonstrated absorption of super-radiant mode ∼98.5% and quasi-BIC ∼93% without back-metal reflector at the telecommunication wavelength. The numerical results, obtained by the finite difference time domain (FDTD) method are explained in the framework of temporal coupled mode theory (TCMT).

https://doi.org/10.1007/s10948-024-06829-z

We studied the dynamical spin susceptibility within the Hubbard model for hole-doped cuprates using cluster perturbation-based methods. Together with the one-electron spectral function, the two-particle response for 3 × 3 and 4 × 4 clusters are calculated and compared to each other. The results obtained are in qualitative agreement with the resonant inelastic neutron scattering and quantum Monte Carlo data.

https://doi.org/10.1134/S2635167624600834

The need to develop a surgical instrument that can most effectively and minimally invasively remove a malignant tumor, and distinguish and destroy only tumor cells without damaging the normal cells of healthy tissue surrounding the tumor is being considered. To achieve this goal, it is proposed to use nanodiscs with special magnetic, electronic and optical properties. Nanodiscs modified with recognition ligands (aptamers) are able to bind to tumor cells and destroy them under the influence of a weak, nonheating alternating magnetic field. This allows for effective tumor destruction while minimizing the impact on surrounding healthy tissue.

https://doi.org/10.1134/S2635167624600731

Aptamers, short oligonucleotides, are capable of high-affinity binding to targets due to their unique structure. Shortening the aptamer while maintaining the active site will increase the affinity and reduce the cost of synthesis. Using the example of the aptamer LC-224, a method for rational optimization of its length and verification of the validity of the developed approach is tested. The use of computer modeling and small-angle X‑ray scattering shows the possibility of optimizing the aptamer structure by removing nucleotides that do not participate in binding to the target. It is shown that truncation of the aptamer does not reduce the affinity and specificity of the DNA aptamer. Thus, theoretical and experimental studies demonstrate successful experience in optimizing the structure of a DNA aptamer by shortening it without compromising its affinity and specificity for its target.

10.23919/INC-USNC-URSI61303.2024.10632342

Accelerated technological progress responds to the dynamic evolution of wireless communication systems, fueled by the advent of 5G, the emergence of 6G, and the pervasive integration of the IoT paradigm. Smart antennas play a pivotal role in this advancement, facilitating electronic beam steering to meet escalating demands for enhanced bandwidth and elevated operating frequencies. The spotlight shifts to reconfigurable reflectarray antennas, gaining prominence over conventional phased arrays. Notably, liquid crystals (LCs) emerge as a promising avenue for creating electronically reconfigurable/switchable reflectarrays, specifically tailored for short millimeter and terahertz waves. LCs, as a unique aggregate state combining solid and liquid features, address current technology limitations. Their uniaxial nature and the ability to manipulate molecule orientation enable effective fine-tuning of dielectric permittivity without drawbacks present in existing technologies.

DOI: 10.21883/TPL.2022.02.53582.19042 

A plasma-chemical method for the modification of silicon carbide particles is presented, which makes it possible to obtain particles with a controlled surface morphology. The variable parameter of particle processing was the ratio of the fraction of plasma-forming (Ar) and additional (H) gases. It was shown that at Ar/H = 100/0, the formation of a carbon shell is observed; at Ar/H ratios of 91/9 and 84/16, the particles are characterized by a carbon shell decorated with silicon nanoparticles or nanowires, respectively. The modified particles were analyzed using scanning electron microscopy and Raman spectroscopy. Keywords: silicon carbide, plasma chemistry, surface morphology, nanoparticles, nanowires, carbon shell, core-shell

https://doi.org/10.1116/6.0003772

Using the methods of atomic force and electron microscopy and the magneto-optical Kerr effect, the role of the interface, roughness, and thickness of the magnetic layer in the temperature-dependent magnetic properties of thin Al₂O₃–Co films with a naturally oxidized cobalt surface was studied. The layers were deposited by magnetron sputtering. The thickness of the cobalt layer varied from 2 to 100 nm. For the first time, the dependences of coercive forces and exchange displacements on the thickness of the cobalt film in the temperature range from 80 to 300 K were obtained and analyzed. The contribution to the coercive force and exchange displacement from the oxidized cobalt surface increases as the temperature decreases below 160 K. The magnitude of the contribution depends on the base material on which the cobalt film is deposited and is maximum for a cobalt film with a thickness of ∼20 nm in the Al₂O₃/Co structure. A weakly magnetic layer was found at the Al₂O₃/Co interface. The behavior of the exchange bias in this layer is similar to the behavior of a ferromagnetic Co core with a naturally oxidized CoO shell. The thickness of this layer depends on the speed and order of deposition of the layers. When the order of deposition of layers (Co/Al₂O₃) changes, the behavior of the exchange displacement of the interface becomes similar to that observed in the ferromagnet/antiferromagnet system. That is, when the deposition order changes, the value of the exchange shift changes sign when the cobalt layer thickness is below 10 nm.