Новые публикации

 10.1109/SIBIRCON56155.2022.10017008

In this work, the approach of ultra-wide band pulses synthesizing is proposed using a broadband low-cost log-periodic dipole antenna and a vector network analyzer. Synthesis of UWB pulse (duration of 2.2ns) became possible due to minimization of antenna dispersion by compensation of amplitude and phase-frequency distortions introduced by the antenna into radiated and received pulse. The method had been developed for a down-looking antenna in a monostatic radar configuration. The antenna return loss was calculated using the model of two-port linear network with S-parameters. To calibrate the model, an original amplitude-phase method was proposed that requires measuring the antenna’s return loss when the antenna is located only at several heights above the reflecting surface (metal sheet). In this case, the antenna return loss in an empty room does not need to be measured. The proposed method for synthesizing UWB pulses does not require changes in the design of the antenna and can be implemented as an additional software calibration of the antenna-feeder path. The proposed method of UWB pulses synthesizing can be implemented using miniature, low-cost vector network analyzers for environment remote sensing from unmanned aerial vehicle using the UWB impulses

 https://doi.org/10.1002/andp.202200543//

Fresnel diffraction on periodic gratings results in a two-dimensional periodic distribution of light intensity, also known as the Talbot effect. Here this approach is extended to the family of superimposed structures with translational symmetry, which consist of superposed spatial harmonics. The Talbot effect is demonstrated to be valid for superimposed gratings. The considered superimposed gratings provide a wide range of textures of optical super-lattices. These texture super-lattices represent a Talbot carpets with a complex motif, which can be varied by choosing structure parameters. These results provide a new functionality for structuring optical lattices and can find potential applications in a wide range of light–matter interactions.

https://doi.org/10.1002/andp.202200480

The near-field effect of diffraction image self-reproduction or self-imaging of a periodic grating illuminated by quasi-monochromatic wave is well-known as the Talbot effect. Introducing a dislocation to a periodic structure provides a fork-shaped modulation of the phase/amplitude, which produces discrete diffraction pattern in a far-field consisting of optical vortices. In this paper, Fresnel diffraction at amplitude fork-shaped grating is theoretically and experimentally studied. The coexistence of spatial ordering and local violation of translational symmetry of the structure manifests itself in a strict diffraction pattern consisting of optical vortices in the far-field, which is shown to be accompanied by formation of a spatially ordered intensity distribution in the near-field, reminiscent the Talbot carpets for periodic structures. These results demonstrate the first evidence of Talbot effect occurred under light diffraction at fork-shaped gratings, being promising for deep understanding of near-field singular optics phenomena.

https://doi.org/10.1016/j.jmmm.2023.170415

Structural and magnetic properties of single crystals of DyMnO3 were investigated by neutron diffraction in order to study the peculiarities of 3d-4f interactions in this compound. Precise magnetic order and its detailed temperature evolution were determined using single crystal neutron diffraction. Elliptical cycloid on manganese subsystem below TCh = 19 K was confirmed, with temperature decrease the elipticity of the Mn magnetic structure reduces significantly, creating almost circular cycloid. Temperature evolution of the magnetic structure demonstrate specific hysteretic behavior. The results show a complex interplay between transition metal and rare earth magnetic sublattices leading to so-called “Mn- controlled” and “Dy- controlled” magnetic states. The strong and complicate 3d-4f interaction leads to the unusual very slow magnetic structure relaxation.

https://doi.org/10.1016/j.physb.2023.414706

Polarized absorption spectra of crystal Ho0.75Nd0.25Fe3(BO3)4 in the region of the 5I8→5F5 absorption band of Ho ions were investigated depending on temperature in the range of 5–20 K. Absorption spectra are decomposed into components of the Lorentz form. The spin-reorientation phase transition was detected at 6.9 K. The observed line position shifts during the reorientation transition were different for different lines, which indicated different local magnetic anisotropy of the Ho ion in its excited states. Significant changes in absorption line intensities as a function of temperature were observed during the reorientation transition and above. These were explained as a consequence of the change in even components of the local crystal field in excited states. These components mix the closely spaced 4f states. Distortion of local symmetry in the ground state was detected at one of the electron transitions.

https://doi.org/10.1038/s41598-021-87854-z

Electro-optical cell based on the cholesteric liquid crystal is studied with unique combination of the boundary conditions: conical anchoring on the one substrate and planar anchoring on another one. Periodic structures in cholesteric layer and their transformation under applied electric field are considered by polarizing optical microscopy, the experimental findings are supported by the data of the calculations performed using the extended Frank elastic continuum approach. Such structures are the set of alternating over- and under-twisted defect lines whose azimuthal director angles differ by 180∘180∘. The U+�+ and U−�−-defects of periodicity, which are the smooth transition between the defect lines, are observed at the edge of electrode area. The growth direction of defect lines forming a diffraction grating can be controlled by applying a voltage in the range of 0≤V≤1.30≤�≤1.3 V during the process. Resulting orientation and distance between the lines don’t change under voltage. However, at V>1.3�>1.3 V U+�+-defects move along the defect lines away from the electrode edges, and, finally, the grating lines collapse at the cell’s center. These results open a way for the use of such cholesteric material in applications with periodic defect structures where a periodicity, orientation, and configuration of defects should be adjusted.

10.1039/d2dt03751c 

Phosphors that exhibit tunable broadband emissions are highly desired in multi-functional LEDs, including pc-WLEDs and pc-NIR LEDs. In this work, broadband emissions were obtained and modulated in the unexpectedly wide spectral range of 517–609 nm for (Lu_0.99−xGd_xBi_0.01)₂WO₆ phosphors by tuning the Gd³⁺ content (x = 0–0.99). The effects of Gd³⁺ doping on phase constituents, particle morphology, crystal structure, and photoluminescence were systematically investigated. Broadband green emission was obtained from Gd³⁺-free (Lu_0.99Bi_0.01)₂WO₆ phosphors (x = 0), whose emission intensity was enhanced by 50% with 5 at% Gd³⁺ (x = 0.05). The phase transition happened when x > 0.50 and the broadband red-NIR emission was obtained when x = 0.75–0.99. Three luminescence centers were proved to be responsible for the broadband green emissions via crystal structure, spectral fitting and fluorescence decay analysis. A pc-WLED with a high color rendering index (R_a = 91.3), a stable emission color, and a low color temperature (3951 K) was fabricated from the (Lu_0.94Gd_0.05Bi_0.01)₂WO₆ broadband green phosphor, and an LED device that simultaneously emits high color rendering index white light and NIR light was obtained with the (Gd_0.99Bi_0.01)₂WO₆ broadband red-NIR phosphor. Night vision and noninvasive imaging were also demonstrated using the latter LED device.

https://doi.org/10.48550/arXiv.2301.04346

We consider light absorption in a germanium grating placed on top of photonic-crystalline substrate. Such a system supports an optical Tamm state decoupled from the continuous spectrum with its frequency within the photonic band gap. We have demonstrated that application of the Tamm state makes in possible to engineer extremely narrow absorber which provides a 100% absorption in a semiconductor grating in the critical coupling regime. The proposed design may be used at both normal and oblique incidence at the telecom wavelength.

https://doi.org/10.1021/acs.chemmater.2c03631

To promote the development of near-infrared (NIR) light sources in optoelectronic and biomedical applications, the discovery of NIR-emitting phosphor materials and their design principles are essential. Herein, we report a novel Eu²⁺-activated broadband NIR-emitting phosphor, BaSrGa₄O₈:Eu²⁺, which features multisite occupation due to Ba/Sr and oxygen site occupancy disorder. With an increase in the Ba/Sr atomic ratio from 1:1 to 1.7:0.3, the Eu²⁺ emission band maximum red-shifts from 670 to 775 nm, along with an enlargement of the full width at half-maximum (FWHM) from 140 to 230 nm. The underlying mechanism for the structure–property relationship is elucidated using density functional theory calculations. The application of the NIR phosphor-converted light-emitting diodes (pc-LEDs) is demonstrated, showing their potential in night-vision technology. Our results can initiate further exploitation of the host structural disorder toward Eu²⁺ broadband NIR luminescence for applications in pc-LEDs.

https://doi.org/10.3390/met13010095

The paper presents the results of tensile and impact bending tests of 17%Cr-19%Mn-0.53%N high-nitrogen austenitic stainless steel in temperatures ranging from −196 to 20 °C. The steel microstructure and fracture surfaces were investigated using transmission and scanning electron microscopes, as well as X-ray diffraction analysis. The steel experiences a ductile-to-brittle transition (DBT); however, it possessed high tensile and impact strength characteristics, as well as the ductile fracture behavior at temperatures down to −114 °C. The correspondence between γ–ε microstructure and fracture surface morphologies was revealed after the tensile test at the temperature of −196 °C. In this case, the transgranular brittle and layered fracture surface was induced by ε-martensite formation. Under the impact bending test at −196 °C, the brittle intergranular fracture occurred at the elastic deflection stage without significant plastic strains, which preceded a failure due to the high internal stresses localized at the boundaries of the austenite grains. The stresses were induced by: (i) segregation of nitrogen atoms at the grain boundaries and in the near-boundary regions, (ii) quenching stresses, and (iii) reducing fcc lattice volume with the test temperature decrease and incorporation of nitrogen atoms into fcc austenite lattice. Anisotropy of residual stresses was revealed. This was manifested in the localization of elastic deformations of the fcc lattice and, consequently, the stress localization in <100>-oriented grains; this is suggested to be the reason of brittle cleavage fracture.

https://doi.org/10.1007/s10854-022-09731-3

The dielectric properties of the Ho_xMn_1−xS (x ≤ 0.1) semiconductors in the frequency range of 100 < ω < 10⁶ Hz at temperatures of 80−550 K have been studied. The temperature crossover from the Debye behavior of the permittivity to the resonance behavior has been found at low holmium concentrations in the compounds. The frequency of the crossover from the migration to dipole orientation polarization with the minimum dielectric loss has been determined. The positive and negative magnetocapacitances for two concentrations of holmium ions have been found. The temperature and frequency ranges of the magnetocapacitance sign change have been established and this phenomenon has been explained using the model of the transition from electrically inhomogeneous to homogeneous states.

https://iopscience.iop.org/article/10.1088/1361-6463/acb0dd

The paper discusses schemes for implementing magneto-mechanical anticancer therapy and the most probable scenarios of damaging mechanical effects on the membranes of malignant cells by targeted magnetic nanoparticles (MNPs) selectively bound to membrane mechanoreceptors employing aptamers. The conditions for the selective triggering of the malignant cell apoptosis in a low-frequency non-heating alternating magnetic field, corresponding to the exceeding threshold value of the force acting on the membrane and its mechanoreceptors, are established using a nanoparticle dynamic simulation. The requirements for the functionality of MNPs and their suitability for biomedical applications are analyzed. Attention is paid to the possibility of the formation of magnetite nanoparticle aggregates in an external magnetic field and their localization near tumor cell membranes. It is shown that the scenario involving the process of aggregation of magnetite nanoparticles provides a sufficient magneto-mechanical impact to achieve a therapeutic effect. A possible explanation for the experimentally established fact of successful application of magneto-mechanical therapy using magnetite nanoparticles is presented, in which complete suppression of the Ehrlich carcinoma in an alternating magnetic field as a response to a magneto-mechanical stimulus was demonstrated. This result confirmed the possibility of using the method for high efficiency treatment of malignant neoplasms. The paper provides an extensive review of key publications and the state of the art in this area.

https://doi.org/10.1007/s40843-022-2315-9

Blue-light-excitable red-emitting phosphors with high thermal stability are essential for fabricating white light-emitting diodes (WLEDs). Herein, Ce3+-doped SrLaScO4 (SLO:Ce3+) phosphor is discovered to have an abnormal red emission band centered at 640 nm when excited at 440 nm. Spectroscopy and structural analyses confirm that Ce3+ ions occupy the [LaO8] polyhedrons competitively, generating a strong crystal field splitting and a large Stokes shift to produce a red emission. To further restrict the thermal quenching of SLO:Ce3+, charge-transfer engineering is implemented by incorporating a large electronegative Ga3+ in the Sc3+ site, which can attract more charges from nearby coordinating groups to decrease the electronic occupation at the bottom of the conduction band and thereby enlarge the band gap. Sc/Ga substitution in SrLa(Sc,Ga)O4:Ce3+ enhances the thermal stability by increasing the intensity ratio from 15% to 31% at 150°C compared with 20°C. This is attributed to the efficient suppression of the thermally stimulated ionization process. This study presents a general design principle for discovering novel Ce3+-doped red phosphors with good thermal stability for WLED applications.

https://doi.org/10.3390/ma16010023

The morphology, structure, and magnetic properties of Fe3O4 and Fe3O4@C nanoparticles, as well their effectiveness for organic dye adsorption and targeted destruction of carcinoma cells, were studied. The nanoparticles exhibited a high magnetic saturation value (79.4 and 63.8 emu/g, correspondingly) to facilitate magnetic separation. It has been shown that surface properties play a key role in the adsorption process. Both types of organic dyes-cationic (Rhodomine C) and anionic (Congo Red and Eosine)-were well adsorbed by the Fe3O4 nanoparticles' surface, and the adsorption process was described by the polymolecular adsorption model with a maximum adsorption capacity of 58, 22, and 14 mg/g for Congo Red, Eosine, and Rhodomine C, correspondingly. In this case, the kinetic data were described well by the pseudo-first-order model. Carbon-coated particles selectively adsorbed only cationic dyes, and the adsorption process for Methylene Blue was described by the Freundlich model, with a maximum adsorption capacity of 14 mg/g. For the case of Rhodomine C, the adsorption isotherm has a polymolecular character with a maximum adsorption capacity of 34 mg/g. To realize the targeted destruction of the carcinoma cells, the Fe3O4@C nanoparticles were functionalized with aptamers, and an experiment on the Ehrlich ascetic carcinoma cells' destruction was carried out successively using a low-frequency alternating magnetic field. The number of cells destroyed as a result of their interaction with Fe3O4@C nanoparticles in an alternating magnetic field was 27%, compared with the number of naturally dead control cells of 6%.

https://doi.org/10.3390/ma16020658

CuOCuO atomic thin monolayer (mlCuOmlCuO) was synthesized recently. Interest in the mlCuOmlCuO is based on its close relation to CuO2CuO2 layers in typical high temperature cuprate superconductors. Here, we present the calculation of the band structure, the density of states and the Fermi surface of the flat mlCuOmlCuO as well as the corrugated mlCuOmlCuO within the density functional theory (DFT) in the generalized gradient approximation (GGA). In the flat mlCuOmlCuO, the CuCu-3dx2−y23��2−�2 band crosses the Fermi level, while the CuCu-3dxz,yz3���,�� hybridized band is located just below it. The corrugation leads to a significant shift of the CuCu-3dxz,yz3���,�� hybridized band down in energy and a degeneracy lifting for the CuCu-3dx2−y23��2−�2 bands. Corrugated mlCuOmlCuO is more energetically favorable than the flat one. In addition, we compared the electronic structure of the considered CuOCuO monolayers with bulk CuOCuO systems. We also investigated the influence of a crystal lattice strain (which might occur on some interfaces) on the electronic structure of both mlCuOmlCuO and determined the critical strains of topological Lifshitz transitions. Finally, we proposed a number of different minimal models for the flat and the corrugated mlCuOmlCuO using projections onto different Wannier functions basis sets and obtained the corresponding Hamiltonian matrix elements in a real space

 https://doi.org/10.3390/photonics10010064

The anodic TiO22 photonic crystals evoke great interest for application as photocatalytic media due to high absorption of light resuling from their specific structure. In this work, the optical properties of the photonic crystal based on a bamboo-type TiO22 nanotube with a metallic coating are analyzed theoretically by the finite-difference time-domain method. The occurrence of Tamm plasmons that appears as a peak in the absorption spectrum is predicted. A Tamm plasmon polariton is a localized state of light excited at the boundary of two highly reflective media, a metal and a Bragg reflector. The integral absorption of the gold-, titanium-, and titanium nitride-coated photonic crystals in the wavelength range of 450–600 nm is calculated. It is established that the titanium nitride-coated structure exhibits the maximum integral absorption.

• https://doi.org/10.1364/JOSAB.477110

It is shown that in the chloroplast periodic structure with a defect, the resonant absorption of light can be implemented. It is found that the resonant light absorption depends significantly on the position of a defect. In terms of the absorption of light energy, an asymmetric resonator is more efficient than a symmetric one

https://doi.org/10.1134/S0021364022601786

The crystal structure and magnetic properties of Fe4BO7 and Mn4BO7 tetraborates have been studied within DFT-GGA. The tetraborates can be found in several possible structural modifications. Three of them, namely, Pbca���� (α-ZnB4O7), Cmcm���� (β-ZnB4O7 structure type), and P6522�6522 (γ-NiB4O7 structure type) have been considered here. The possible magnetic orderings in three structure types are described within group-theoretical analysis. The following DFT calculations allow finding the lowest energy magnetic structure for Fe4BO7 and Mn4BO7 in three structure types. The total energies of tetraborates in three structure types have been compared with and without taking into account the spin polarization. It has been found that Mn4BO7 and Fe4BO7 in the non-spin-polarized case have the α-ZnB4O7 and γ-NiB4O7 structure types as the lowest energy structure, respectively. However, when the magnetic structure is taken into account, the antiferromagnetic α-ZnB4O7 phase becomes the ground state for both tetraborates. The pressure dependence of the enthalpy of Fe4BO7 and Mn4BO7 tetraborates has been studied. It has been found that the applied pressure results in the appearance of the β-ZnB4O7 structure type as the lowest energy structure under pressure.

https://doi.org/10.3390/nano12244366

Mixed Co-Ni bimetallic systems with the structure of a solid substitution solution have been synthesized using the supercritical antisolvent precipitation (SAS) method, which uses supercritical CO₂ as an antisolvent. The systems obtained have been characterized in detail using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared (FTIR) spectroscopy, and magnetostatic measurements. It has been found that Co-enriched systems have a defective hexagonal close-packed (hcp) structure, which was described by a model which embedded cubic fragments of packaging into a hexagonal close-packed (hcp) structure. It has been shown that an increase in water content at the precipitation stage leads to a decrease in the size of cubic fragments and a more uniform distribution of them in Co-enriched systems. It has also been shown that mixed systems have the greatest coercivity in the line of samples. Ni-enriched bimetallic systems have a cubic close-packed (ccp) structure with modified crystal lattice parameters.

https://doi.org/10.1103/PhysRevE.106.064203

It is known that the quantum transport of noninteracting Bose particles across a tight-binding chain is ballistic in the sense that the current does not depend on the chain length. We address the question whether the transport of strongly interacting bosons can be ballistic as well. We find such a regime and show that, classically, it corresponds to the synchronized motion of local nonlinear oscillators. It is also argued that, unlike the case of noninteracting bosons, the transporting state responsible for the ballistic transport of interacting bosons is metastable, i.e., the current decays in the course of time. An estimate for the decay time is obtained.

 https://doi.org/10.3390/e25010117

We analyze the classical and quantum dynamics of the driven dissipative Bose–Hubbard dimer. Under variation of the driving frequency, the classical system is shown to exhibit a bifurcation to the limit cycle, where its steady-state solution corresponds to periodic oscillation with the frequency unrelated to the driving frequency. This bifurcation is shown to lead to a peculiarity in the stationary single-particle density matrix of the quantum system. The case of the Bose–Hubbard trimer, where the discussed limit cycle bifurcates into a chaotic attractor, is briefly discussed.

https://doi.org/10.3390/ma16020537

We present an extensive study of the luminescence characteristics of Mn impurity ions in a YAl₃(BO₃)₄:Mn crystal, in combination with X-ray fluorescence analysis and determination of the valence state of Mn by XANES (X-ray absorption near-edge structure) spectroscopy. The valences of manganese Mn²⁺(d⁵) and Mn³⁺(d⁴) were determined by the XANES and high-resolution optical spectroscopy methods shown to be complementary. We observe the R₁ and R₂ luminescence and absorption lines characteristic of the ²E ↔ ⁴A₂ transitions in d³ ions (such as Mn⁴⁺ and Cr³⁺) and show that they arise due to uncontrolled admixture of Cr³⁺ ions. A broad luminescent band in the green part of the spectrum is attributed to transitions in Mn²⁺. Narrow zero-phonon infrared luminescence lines near 1060 nm (9400 cm⁻¹) and 760 nm (13,160 cm⁻¹) are associated with spin-forbidden transitions in Mn³⁺: ¹T₂ → ³T₁ (between excited triplets) and ¹T₂ → ⁵E (to the ground state). Spin-allowed ⁵T₂ → ⁵E Mn³⁺ transitions show up as a broad band in the orange region of the spectrum. Using the data of optical spectroscopy and Tanabe–Sugano diagrams we estimated the crystal-field parameter Dq and Racah parameter B for Mn³⁺ in YAB:Mn as Dq = 1785 cm⁻¹ and B = 800 cm⁻¹. Our work can serve as a basis for further study of YAB:Mn for the purposes of luminescent thermometry, as well as other applications.

https://doi.org/10.3390/nano13020368

Chevrel non-van der Waals crystals are promising candidates for the fabrication of novel 2D materials due to their versatile crystal structure formed by covalently bonded (Mo₆X₈) clusters (X–chalcogen atom). Here, we present a comprehensive theoretical study of the stability and properties of Mo-based Janus 2D structures with Chevrel structures consisting of chalcogen and halogen atoms via density functional theory calculations. Based on the analysis performed, we determined that the S₂Mo₃I₂ monolayer is the most promising structure for overall photocatalytic water-splitting application due to its appropriate band alignment and its ability to absorb visible light. The modulated Raman spectra for the representative structures can serve as a blueprint for future experimental verification of the proposed structures.

https://doi.org/10.1016/j.ijhydene.2022.12.286

The successful fabrication of H-phase Janus transition metal dichalcogenides (TMDs) has received considerable interest due to its great potential in photocatalytic applications. Here, new A′-XMoY (X/Y = O, S, Se, Te) Janus-type structures belonging to the family of TMDs were theoretically investigated for the first time in terms of photocatalytic water splitting via DFT calculations. For all compounds, the Raman spectra were calculated. The SMoO, SeMoO, SMoSe, SMoTe and SeMoTe compounds are dynamically stable and are semiconductors. Among all considered structures SMoTe is the most promising candidate for solar hydrogen production because valence and conduction bands perfectly engulf the redox potentials of water at both neutral and acidic media, opposite to SMoSe, SMoO, SeMoO suitable only in the acidic media, and SeMoTe – in the neutral media. Moreover, A′-SMoTe demonstrates the outstanding values of the solar-to-hydrogen (STH) conversion efficiencies of 54.0 and 67.1 for neutral and acidic media.

DOI: https://doi.org/10.1103/PhysRevA.106.063507

We consider thermo-optic hysteresis in a silicon structure supporting bound states in the continuum. Taking into account radiative heat transfer as a major cooling mechanism we constructed a nonlinear model describing the optical response. It is shown that the thermo-optic hysteresis can be obtained with low intensities of incident light $I_0\approx 1W/m^2$ at the red edge of the visible under the critical coupling condition.

 https://doi.org/10.1111/jace.18981

During pursuing high color rendering index for full-color-emitting phosphor, low quantum efficiency (QE) is usually accompanying. We intend to elevate the luminescence efficiency when realizing a solar-like spectra distribution, by constructing apatite structure oxynitride, inheriting high covalence and rigidity from oxynitride, and suitable multiple cation sites from oxyapatite compounds. Full-color-emitting apatite structure oxynitride phosphor (Mg,Y)₅Si₃(O,N)₁₃:Ce³⁺,Mn²⁺ has been prepared, and the crystal sites’ occupancies of activators in this host were favorable for white emission. (Mg,Y)₅Si₃(O,N)₁₃:Ce³⁺,Mn²⁺ phosphor shows whole visible light with emission wavelength ranging from 370 to 750 nm, matching the spectra of sunlight quite well. The fabricated white light-emitting diode lamp demonstrated the distinctive overall performance of QE and chromaticity properties (R_a and R₉). Furthermore, correlated color temperature is tunable from cool nature to warm white. The obtained lamp possesses the feature of less blue light hazard and high saturation of red degree, compared with the commercial YAG-based lamp.

https://doi.org/10.1134/S0965544122100176

Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was for the first time employed to investigate in situ paraffin crystallization under CO₂ high-pressure and to evaluate a critical parameter—wax appearance temperature (WAT). To determine the WAT under pressure, conventional calculation methods based on changes in the band of rocking vibrations of CH₂ group were used. Using model 10 wt % paraffin solutions in n-dodecane, temperature effects were investigated under CO₂ pressures of 10, 20, 30, and 40 atm. It was experimentally confirmed that an increase in the CO₂ pressure reduces the WAT. Furthermore, the plot of peak intensity of the spectral band attributed to dissolved CO₂ as a function of temperature showed a maximum that can serve as an additional WAT indicator. This enhances the measurement accuracy and the reliability of WAT evaluation.

https://doi.org/10.1016/j.molstruc.2022.134851

Luminescent (C₅H₁₃N₂S)₂[MnBr₄] (1) and (C₇H₁₇N₂S)₂[MnBr₄] (2) (C₅H₁₂N₂S = N,N′-diethylthiourea, C₇H₁₆N₂S = N,N′-diisopropylthiourea) were prepared via solvothermal method, and the structures of these compounds have been resolved using X-ray single crystal diffraction. The structures consist of electrostatically bound MnBr₄²⁻ anions and organic C₅H₁₃N₂S⁺ and C₇H₁₇N₂S⁺ cations. The intermolecular N−H···Br and N−H···S hydrogen bonds additionally stabilize crystal structures of 1-2. Upon excitation over broadband covering the range 265 to 515 nm, these compounds show green emission peaking at 526 nm for 1 and 522 nm for 2, which is assigned to the ⁴T₁→ ⁶A₁ electronic transition of Mn²⁺ from isolated within the crystal structures MnBr₄²⁻ tetrahedra. The photoluminescence quantum yield (PLQY) of powder 1 is 97 ± 7% for excitation at 440 nm and that of powder 2 is 83 ± 7% for excitation at 365 nm. The high PLQY indicates the absence of noticeable concentration quenching at shortest Mn···Mn distance of 8.11 and 8.73 Å between Mn²⁺ ions within the structures of 1 and 2. The high-performance photoluminescence of 0D (C₅H₁₃N₂S)₂[MnBr₄] and (C₇H₁₇N₂S)₂[MnBr₄] compounds demonstrated promising applications in photonics.

http://nano.ivanovo.ac.ru/journal/en/articles/article.php?year=2022&issue=4&first_page=55

Исследован электрооптический отклик пленок капсулированных полимером жидких кристаллов, в которых полимер задает конические граничные условия для холестерика и нематика. Показано, что для пленки на основе холестерика с относительным хиральным параметром капель, равным 0,32, управляющие напряжения меньше управляющих напряжений для пленок на основе нематика. Пороговые напряжения составляют 2,7 В и 4,9 В, а напряжения насыщения 7,3 В и 9,0 В для пленок на основе холестерика и нематика, соответственно. При напряжении насыщения светопропускание этих пленок составляет более 80 %. Пленка на основе холестерика переходит в состояние сильного рассеяния света в течение 85 мс после отключения напряжения, а пленка на основе нематика переходит в состояние начального рассеяния в течение нескольких дней. Существенные различия в электрооптическом отклике пленок на основе холестерика и нематика были объяснены с помощью исследования электроиндуцированных трансформаций ориентационных структур, формирующихся в каплях нематика и холестерика. Капсулированные полимером холестерические жидкие кристаллы с коническими граничными условиями перспективны для разработки устройств с низковольтным управлением.