Новые публикации

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.