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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Verpekin, Victor V., Semeikin, Oleg, V, Vasiliev A. D., Kondrasenko, Alexander A., Belousov Yu. A., Ustynyuk, Nikolai A.
Заглавие : Catalyzed M–C coupling reactions in the synthesis of σ-(pyridylethynyl)dicarbonylcyclopentadienyliron complexes
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [18-73-00150]
Место публикации : RSC Adv. - 2020. - Vol. 10, Is. 29. - P.17014-17025. - ISSN 2046-2069(eISSN), DOI 10.1039/d0ra02333g
Примечания : Cited References: 86. - This research was funded by a grant from the Russian Science Foundation (project No. 18-73-00150).
Предметные рубрики: NONLINEAR-OPTICAL PROPERTIES
METAL ALKYNYL COMPLEXES
CARBON BOND FORMATION
Аннотация: The reactions between terminal ethynylpyridines, (trimethylsilyl)ethynylpyridines and cyclopentadienyliron dicarbonyl iodide were studied under Pd/Cu-catalyzed conditions to develop a synthetic approach to the σ-alkynyl iron complexes Cp(CO)2Fe–C≡C–R (R = ortho-, meta-, para-pyridyl). Depending on the catalyst and reagents used, the yields of the desired σ-pyridylethynyl complexes varied from 40 to 95%. In some cases the reactions with ortho-ethynylpyridine gave as byproduct the unexpected binuclear FePd μ-pyridylvinylidene complex [Cp(CO)Fe{μ2-η1(Cα):η1(Cα)-κ1(N)-Cα=Cβ(H)(o-C5H4N)}(μ-CO)PdI]. The conditions, catalysts, and reagents that provide the highest yields of the desired σ-pyridylethynyl iron compounds were determined. The methods developed allowed the synthesis of the corresponding σ-4-benzothiadiazolylethynyl complex Cp(CO)2Fe–C≡C–(4-C6H3N2S) as well. Eventually, synthetic approaches to σ-alkynyl iron complexes of the type Cp(CO)2Fe–C≡C–R (R = ortho-, meta-, para-pyridyl, 4-benzothiadiazol-2,1,3-yl) based on the Pd/Cu-catalyzed cross-coupling reactions were elaborated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li, Mingze, Li, Yawen, Molokeev M. S., Zhao, Jing, Na, Guangren, Zhang, Lijun, Xia, Zhiguo
Заглавие : Halogen substitution in zero-dimensional mixed metal halides toward photoluminescence modulation and enhanced quantum yield
Место публикации : Adv. Opt. Mater. - 2020. - Vol. 8, Is. 16. - Ст.2000418. - ISSN 2195-1071, DOI 10.1002/adom.202000418
Примечания : Cited References: 34. - M.L., Y.L. contributed equaly to this work. This work was supported by the National Natural Science Foundation of China (51961145101, 51972118, and 51722202), Fundamental Research Funds for the Central Universities (FRFTP-18-002C1), the Guangdong Provincial Science &Technology Project (2018A050506004), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01 x 137). This work was also funded by RFBR according to the research project No. 19-52-80003. The work at Jilin University is supported by the National Natural Science Foundation of China (Grant No. 61722403 and 11674121) and Jilin Province Science and Technology Development Program (Grant No. 20190201016JC). Calculations were performed in part at the high performance computing center of Jilin University.
Предметные рубрики: WHITE-LIGHT EMISSION
PEROVSKITES
EXCITONS
Аннотация: Zero‐dimensional (0D) organic−inorganic hybrid metal halides haveunprecedented degrees of freedom for structural tunability and photoluminescence modulation. Here, the 0D isomorphic hybrid metal mixed halides (C9NH20)9Pb3Zn2Br19(1−x )Cl19x (x = 0–1) with continuous halogen contents control, exhibiting tunable emission and enhancement of photoluminescence quantum yield (PLQY) are reported. The competitive bromine to chlorine substitution process in (C9NH20)9Pb3Zn2Br19(1−x )Cl19x occurs first in [ZnBr4−x Clx ]2− tetrahedron before the [Pb3Br11−x Clx ]5− trimer. The increasing Cl content in samples from x = 0 to 1 results in an expected blue shift of emission peak from 565 to 516 nm, and meanwhile a strikingly room temperature PL quantum yield increase from 8% to 91%. Combined experimental characterizations and theoretical calculations indicate that the blue shift of interband transition energy is responsible for the emission peak shift. Moreover, with the increasing Cl content, the enhanced electron−phonon interaction and the weakened thermal‐assisted nonradiative recombination result in more efficient radiative transition channels and ultimately enhanced PLQY. The impact of halogen substitution on electronic structures and optical properties in 0D hybrid metal halides is emphasized in this work as a new strategy to promote the future development of new luminescent materials.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kostyukov A. I., Snytnikov V. N., Snytnikov V. N., Ishchenko A. V., Rakhmanova M. I., Molokeev M. S., Krylov A. S., Aleksandrovsky A. S.
Заглавие : Luminescence of monoclinic Y2O3:Eu nanophosphor produced via laser vaporization
Место публикации : Opt. Mater. - 2020. - Vol. 104. - Ст.109843. - ISSN 09253467 (ISSN), DOI 10.1016/j.optmat.2020.109843
Примечания : Cited References: 19. - This work is financially supported by the Russian Foundation for Basic Research № 19-32-60027
Аннотация: Europium doped Y2O3spherical nanoparticles with the diameter ~10 nmobtained via cw laser vaporization are shown to crystallize in monoclinic symmetry class (C2/m space group). The size of nanoparticles established via HRTEM coincides with coherent scattering region established by XRD. Luminescence spectrum in the vicinity of ultranarrow transition demonstrates three peaks consistent with three inequivalent positions of Eu3+ ion in monoclinic Y2O3 lattice. Hypersensitive transition dominates in the spectrum, admitting the lack of inversion symmetry at Cs sites occupied by Eu3+. The spectrum of hypersensitive transition is expanded to the red part of spectrum due intense transitions terminating at higher-lying components of crystal-field-split 7F2 energy level. Obtaining chromaticity coordinates (0.669, 0.331)and absolute quantum yield (~21%) is possible using red phosphor based on monoclinic Y2O3:Eu3+.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gardymova, Anna P., Krakhalev M. N., Zyryanov V. Ya.
Заглавие : Optical textures and orientational structures in cholesteric droplets with conical boundary conditions
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [18-72-10036]
Место публикации : Molecules. - 2020. - Vol. 25, Is. 7. - Ст.1740. - ISSN 1420-3049(eISSN), DOI 10.3390/molecules25071740
Примечания : Cited References: 53. - The authors are grateful for the financial support by the Russian Science Foundation (grant No. 18-72-10036).
Предметные рубрики: DISPERSED LIQUID-CRYSTALS
CHIRAL NEMATIC DROPLETS
IONIC MODIFICATION
Аннотация: Cholesteric droplets dispersed in polymer with conical boundary conditions have been studied. The director configurations are identified by the polarising microscopy technique. The axisymmetric twisted axial-bipolar configuration with the surface circular defect at the droplet’s equator is formed at the relative chirality parameter N0≤2.9 . The intermediate director configuration with the deformed circular defect is realised at 2.9N03.95 , and the layer-like structure with the twisted surface defect loop is observed at N0≥3.95 . The cholesteric layers in the layer-like structure are slightly distorted although the cholesteric helix is untwisted.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylova S. N., Aleksandrovsky A. S., Roginskii E. M., Krylov A. A., Gudim I. A., Vtyurin A. N.
Заглавие : Optical properties of the HoGa3(BO3)4 crystal: experiment and ab initio calculation
Место публикации : Ferroelectrics. - 2020. - Vol. 559, Is. 1. - P.135-140. - ISSN 00150193 (ISSN), DOI 10.1080/00150193.2020.1722015
Примечания : Cited References: 22. - This work was supported by the Russian Foundation for Basic Research (grant No 18-02-00754)
Аннотация: Single crystal of HoGa3(BO3)4 has been grown using solution-melt synthesis. The optical band gap determined from the measured absorption spectrum is due to direct allowed transition and equals to 4.14 eV. The optical properties of this crystal are calculated by the plane-wave pseudo-potential method based on density functional theory. The structure of the crystal has been optimized. The electronic structure of HoGa3(BO3)4 is calculated. The experimental and theoretical fundamental absorption spectra are compared. The calculated bandgap is in good agreement with the experimental data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shtarev D. S., Kevorkyants R., Molokeev M. S., Shtareva A. V.
Заглавие : Effect of composition on the optical and photocatalytic properties of visible light responsive materials Bi26-xMgxO40
Место публикации : Inorg. Chem. - 2020. - Vol. 59, Is. 12. - P.8173-8183. - ISSN 00201669 (ISSN), DOI 10.1021/acs.inorgchem.0c00486
Примечания : Cited References: 41. - This study was supported by a grant from the Russian Science Foundation (Project No 19-73-10013). The authors acknowledge the help of the Yu. A. Kosygin Institute of Tectonics and Geophysics FEB RAS in conducting the study and offering their research equipment. The authors also thank the Research Center on Nanophotonics, the Center for Physical Methods of Surface Investigation (Dr. Alexandra Koroleva), and the Computing Centre of the Saint-Petersburg State University. R.K. acknowledges financial support from a grant from the Saint-Petersburg State University (Pure ID 39054581)
Аннотация: We report the synthesis and the crystal and electronic structure as well as the optical and photocatalytic properties of novel photoactive materials of the general formula Bi26–xMgxO40. Two compounds with compositions of Bi24.28(3)Mg1.72(3)O40 and Bi24.05(3)Mg1.95(3)O40 are synthesized using the pyrolytic method. According to X-ray diffraction analysis, the materials are monocrystalline species. Their electronic bandgaps determined from Tauc plots are 2.41 eV [Bi24.28(3)Mg1.72(3)O40] and 2.69 eV [Bi24.05(3)Mg1.95(3)O40]. Keeping in mind that optical bandgaps are typically larger than their electronic counterparts, we find that the bismuthate bandgaps match well that of Bi24Mg2O40 (2.26 eV) predicted by density functional theory. Apparently, the synthesized bismuthates are indirect bandgap semiconductors just like Bi24Mg2O40. Both materials demonstrate nearly identical luminescence spectra. Their luminescence emission at 620 nm is most efficiently excited by 365 nm light. The materials’ photocatalytic properties are evaluated in a visible light-induced photocatalytic phenol degradation reaction. Rather low activity of both compounds is detected. However, Bi24.05(3)Mg1.95(3)O40 is ∼2 times more photocatalytically active than Bi24.28(3)Mg1.72(3)O40, which is associated with a higher Bi5+ content in the former.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vetrov S. Ya., Timofeev I. V., Shabanov V. F.
Заглавие : Localized modes in chiral photonic structures
Место публикации : Phys. Usp. - 2020. - Vol. 63, Is. 1. - P.33-56. - ISSN 1063-7869, DOI 10.3367/UFNe.2018.11.038490. - ISSN 1468-4780(eISSN)
Примечания : Cited References: 251
Предметные рубрики: CHOLESTERIC LIQUID-CRYSTAL
CONTROLLED LIGHT-SCATTERING
SCULPTURED THIN-FILMS
Аннотация: We discuss chiral structures in self-organizing, artificial, and biological materials. A review of experimental studies and recent advances in the localization of light in chiral structures is given. The behavior of polarized resonant modes in such structures is examined using the example of a one-dimensional photonic crystal containing liquid crystal materials. The anomalous spectral shifts of transmission peaks are interpreted as the contribution of the geometric phase caused by the twisting of the layers of the liquid crystal. The optical Tamm state localized at the boundary between chiral and nonchiral mirrors in the form of a cholesteric layer and a polarization-preserving anisotropic mirror is analytically and numerically described. Considerable attention is paid to the presentation of the properties of localized optical modes in the cholesteric with a resonant metal-dielectric nanocomposite. New possibilities for controlling the properties of the photonic structure are noted, due to the combination of the dispersion of the resonant medium and the intrinsic dispersion of the cholesteric. Attention is focused on controlled hybrid modes in the cholesteric structure formed by the coupling of localized modes. Possible applications and further ways of developing the concept of chiral photonic structures are deliberated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Новые методы исследования ориентационного порядка одноосных молекулярных пленок на основе оптических данных
Место публикации : Жидк. кристаллы и их практич. использ. - 2020. - Т. 20, № 1. - С. 41-46. - ISSN 1991-3966, DOI 10.18083/LCAppl.2020.1.41; Liq. Cryst. Appl.
Примечания : Библиогр.: 7
Аннотация: Установлена связь компонент ε(1,2)j(ω) диэлектрической функции εj(ω) = ε1j(ω) + iε2j(ω) для одноосной молекулярной пленки в области изолированной полосы поглощения света, поляризованного вдоль (j = ||) и нормально (j = ⊥) оптической оси пленки, с параметром ориентационного порядка S дипольных моментов молекулярных переходов, отвечающих данной полосе поглощения. Развиты новые методы определения S, подтвержденные для пленки органического полупроводника PTCDA нанометровой толщины с известными зависимостями ε(1,2)j(ω) в областях прозрачности и низкочастотного электронного поглощения. Показано влияние ориентационного порядка и анизотропии динамических диполь-дипольных межмолекулярных взаимодействий (эффектов локального поля) на положение максимумов полос ε2j(ω).The components ε(1,2)j(ω) of the dielectric function εj(ω) = ε1j(ω) + iε2j(ω) for uniaxial molecular film in the region of an isolated absorption band of the light polarized along (j = ||) and across (j = ⊥) the film optical axis were considered. The connection of the components with the orientation order parameter S of the dipole moments of molecular transitions corresponding to a given absorption band was established. New methods for determining S are developed. They are confirmed for the organic semiconductor PTCDA film of nanoscale thickness with the known dependences ε(1,2)j(ω) in the transparency and low-frequency electron absorption regions. The effect of the orientation order and anisotropy of dynamic dipole-dipole intermolecular interactions (local-field effects) on the maxima position of the ε2j(ω) bands was shown.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M., Gorev M. V., Pogoreltsev E. I.
Заглавие : Mixed-valence hydrated iron fluoridotitanate: synthesis, optics and calorimetry
Место публикации : J. Phys. Chem. Solids. - 2020. - Vol. 142. - Ст.109444. - ISSN 00223697 (ISSN), DOI 10.1016/j.jpcs.2020.109444
Примечания : Cited References: 35
Аннотация: Mixed-valence hydrated fluoridotitanate with idealized formula FeTiF6·6H2O is the main product of fluoride processing of natural mineral ilmenite with hydrofluoric acid. Its single crystals were grown and optical and calorimetric experiments were carried out in the temperature range 200–350 K. Charge re-distribution, Fe2+Ti4+ to Fe3+Ti3+, in the compound studied was evident in XPS spectra. A first order ferroelastic phase transition occurs at temperatures T0↓ = 271.5 K, T0↑ = 274 ÷ 275.5 K with the symmetry change P3‾↔ P1‾. The structural transformation is accompanied by the appearance of a very weak optical anisotropy in the slice (001), a small anomaly of the heat capacity (ΔS = 1.5 J/mol K = 0.2R), and positive baric coefficients dT0/dp ≈ 30 ± 10 K/GPa.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li, Mingze, Molokeev M. S., Zhao, Jing, Xia, Zhiguo
Заглавие : Optical functional units in zero-dimensional metal halides as a paradigm of tunable photoluminescence and multicomponent chromophores
Место публикации : Adv. Opt. Mater. - 2020. - Vol. 8, Is. 8. - Ст.1902114. - ISSN 2195-1071, DOI 10.1002/adom.201902114
Примечания : Cited References: 38. - This work was supported by the National Natural Science Foundation of China (Nos. 51961145101, 51722202, and 51972118), Fundamental Research Funds for the Central Universities (D2190980), the Guangdong Provincial Science & Technology Project (2018A050506004), and this work was also funded by RFBR according to the Research Project No. 19-52-80003
Предметные рубрики: PEROVSKITES
LUMINESCENCE
ABSORPTION
EMISSION
Аннотация: Zero-dimensional (0D) organic–inorganic hybrid luminescent metal halides have many promising optoelectronic applications; however, the single building unit in the 0D framework restricts their multimode optical control and photoluminescence tuning. Thus, it remains urgent but challenging to rationally design distinct anionic polyhedral with different optical functions and further expand this family by an equivalent cation substitution and halogen replacement. Herein, (C9NH20)9[Pb3X11](MX4)2 (X = Br and Cl, M = Mn, Fe, Co, Ni, Cu, and Zn) is successfully synthesized verifying the rationality of the design philosophy, and the optical characterizations demonstrate the effects of X‐position anions and M‐position cations on luminescence process. Intriguingly, both [Pb3X11]5− and [MX4]2− perform as inorganic building units in this 0D system and optically active centers, in which the former leads to high‐efficiency broad‐band yellow/green emission originating from self‐trapped excitons and the as‐observed multicomponent chromophores are derived from the absorption of the latter in the visible light region. The present work highlights the importance of different optical functional units showing synergistic effects on the physical properties and inspires future studies to explore multifunctional application of 0D luminescent metal halides.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Аверьянов, Евгений Михайлович
Заглавие : Оптическая анизотропия и ориентационный порядок одноосных пленок сопряженных полимеров
Место публикации : Жидк. кристаллы и их практич. использ. - 2020. - Т. 20, № 1. - С. 53-63. - ISSN 1991-3966, DOI 10.18083/LCAppl.2020.1.53; Liq. Cryst. Appl.
Примечания : Библиогр.: 14
Аннотация: Для одноосной пленки сопряженного полимера с макромолекулами в виде наборов субъединиц разной длины установлена связь компонент e(1,2)j(w) диэлектрической функции ej(w) = e1j(w) + ie2j(w) с параметром ориентационного порядка s дипольных моментов молекулярных переходов, отвечающих изолированной полосе поглощения света c поляризацией вдоль (j = || ) и нормально (j =. ) оптической оси пленки. Новые методы определения s реализованы для пленки полимера P3OT с плоскостной ориентацией субъединиц и известными зависимостями e(1,2)j(w) в областях прозрачности и низкочастотного электронного поглощения. Учтена анизотропия компонент fj(w) = 1 + Lj[ej(w) - 1] тензора локального поля. Экспериментальные значения компонент Lj тензора Лорентца для пленки P3OT определены с использованием зависимостей e1j(w) в видимой области прозрачности. Показано совместное влияние длины и ориентационного порядка субъединиц, а также динамических диполь-дипольных взаимодействий между субъединицами (эффектов локального поля) на положение максимумов полос e2j(w).The uniaxial film of conjugated polymer with macromolecules as a set of subunits of different lengths was studied. For this film, the connection between the components e(1,2)j(w) of the dielectric function ej(w) = e1j(w) + ie2j(w) and the orientation order parameter s was established. The orientation order parameter s of the dipole moments of molecular transitions corresponds to an isolated absorption band of light with polarization along (j = ||) and across (j =. the optical axis of the film. New methods have been implemented for determining s of the P3OT polymer film. The P3OT polymer film is characterized by a planar orientation of subunits and known dependences e(1,2)j(w) in the regions of transparency and low-frequency electron absorption. The anisotropy of the components fj(w) = 1 + Lj[ej(w) - 1] of the local-field tensor was taken into account. The experimental values of the components Lj of the Lorentz tensor for the P3OT film were determined using the dependences e1j(w) in the visible transparency region. The combined effect of the length and orientation order of the subunits, as well as dynamic dipole-dipole interactions between subunits (local-field effects) on the position of the maxima of the e2j(w) bands was shown.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Popova M. N., Chukalina E. P., Erofeev D. S., Jablunovskis A., Gudim I. A., Malkin B. Z.
Заглавие : High-resolution optical spectroscopy and modeling of spectral and magnetic properties of multiferroic ErFe3(BO3)4
Коллективы : Russian Science FoundationRussian Science Foundation (RSF) [19-12-00413]
Место публикации : Phys. Rev. B. - 2020. - Vol. 101, Is. 20. - Ст.205108. - ISSN 2469-9950, DOI 10.1103/PhysRevB.101.205108. - ISSN 2469-9969(eISSN)
Примечания : Cited References: 38. - Financial support of the Russian Science Foundation under Grant No. 19-12-00413 is acknowledged.
Предметные рубрики: F-F TRANSITIONS
ENERGY-LEVELS
ER3+ IONS
GROWTH
Аннотация: We carried out the high-resolution broadband temperature-dependent polarized optical spectroscopy and theoretical studies of ErFe3(BO3)4 single crystals in the paramagnetic and antiferromagnetic (T˂TN=39K) phases. On the basis of the experimentally determined 45 crystal-field (CF) levels of Er3+ ions at sites with the C2 point symmetry, CF calculations were performed, a set of physically grounded CF parameters was obtained and used to model the temperature dependences of the Er magnetic moments measured in neutron-scattering experiments, as well as the magnetic susceptibility and magnetization of the compound; the contributions of the quasi-one-dimensional iron magnetic subsystem were calculated in the frame of the previously developed self-consistent four-particle cluster model. The modeling strongly supports an easy-plane collinear structure of iron magnetic moments and excludes earlier proposed additional magnetic phase.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Немцев, Андрей В.
Заглавие : Ab Initio study of the relation between the structural, magnetic, and optical properties of normal and inverse MnGa2O4 spinels
Коллективы : Russian Foundation for Basic Research, Government of Krasnoyarsk Territory; Krasnoyarsk Regional Fund of Science [18-42-243019]
Место публикации : J. Exp. Theor. Phys. - 2020. - Vol. 130, Is. 3. - P.418-422. - ISSN 1063-7761, DOI 10.1134/S106377612002017X. - ISSN 1090-6509(eISSN)
Примечания : Cited References: 20. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research project no. 18-42-243019: "First-principles studies of the polarization, magnetic, electronic, and magnetoelectric properties of functional compounds with a spinel structure containing 3d and 4f ions."
Предметные рубрики: STABILITY
Аннотация: The electronic, magnetic, and optical properties of MnGa2O4 in the structure of the normal and inverse spinels are subjected to an ab initio investigation and comparison. The generalized gradient approximation (GGA) predicts that the normal MnGa2O4 spinel is a semiconductor with a bandgap of about 0.7 eV, and a bandgap in the structure of the inverse spinel appears only in terms of the GGA + U approach. A simple exchange interaction model is used to calculate exchange integrals. In both structure types, MnGa2O4 exhibits antiferromagnetic behavior, and the normal structure is energetically favorable. The inverse spinel becomes energetically favorable only when a negative pressure is applied. The absorption spectra of the normal spinel are found to have a spectral window at a wavelength larger than 450 nm.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Parshin A. M., Sutormin V. S., Zyryanov V. Ya., Shabanov V. F.
Заглавие : Polar anchoring energy and tilt angle measured by magneto-optical technique in nematic doped with ionic surfactant
Место публикации : Liq. Cryst. - 2020. - Vol. 47, Is. 12. - P.1825-1831. - ISSN 0267-8292, DOI 10.1080/02678292.2020.1733683. - ISSN 1366-5855(eISSN)
Примечания : Cited References: 32
Предметные рубрики: LIQUID-CRYSTAL
TEMPERATURE-DEPENDENCE
INTERFACE
ADSORPTION
Аннотация: The surface anchoring of a nematic doped with the ionic surfactant has been investigated and compared with the one in the undoped sample. The director tilt angle at the substrates coated with the orienting polymer film has been determined by the null method in a rotating magnetic field. The Frederiks transition in a magnetic field has been chosen as a convenient technique to measure the polar anchoring energy Wθ. The temperature dependences of anchoring energy have been obtained for the various nematic cells. The Wθ values for nematic doped with the ionic surfactant are less than for the undoped one. The factors affecting the measurement accuracy have been discussed. The accuracy is higher for the thinner nematic layers and weaker anchoring energy.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu, Dongjie, Yun, Xiaohan, Li, Guogang, Dang, Peipei, Molokeev M. S., Lian, Hongzhou, Shang, Mengmeng, Lin, Jun
Заглавие : Enhanced cyan emission and optical tuning of Ca3Ga4O9:Bi3+ for high-quality full-spectrum white light-emitting diodes
Место публикации : Adv. Opt. Mater. - 2020. - Vol. 8, Is. 22. - Ст.2001037. - ISSN 2195-1071, DOI 10.1002/adom.202001037
Примечания : Cited References: 55. - This work was financially supported by the National Natural Science Foundation of China (NSFC No. 51932009, 51720105015, 51672265, 51672266, 51672257 and 51672259), the Key Research Program of Frontier Sciences, CAS (Grant No. YZDY-SSW-JSC018), Science and Technology Cooperation Project between Chinese and Australian Governments (2017YFE0132300), the Jiangmen Innovative Research Team Program (2017), and the Major Program of Basic Research and Applied Research of Guangdong Province (2017KZDXM083)
Предметные рубрики: ENERGY-TRANSFER
TUNABLE LUMINESCENCE
PHOSPHOR
CRYSTAL
MODULATION
Аннотация: Highly efficient cyan‐emitting phosphor materials are indispensable for closing the cyan gap in spectra of the traditional phosphor‐converted white light‐emitting diodes (WLEDs) to achieve high‐quality full‐spectrum white lighting. In this work, bright cyan‐emitting Ca3Ga4O9 (CGO):0.02Bi3+,0.07Zn2+ phosphor is developed to bridge the cyan gap. Such a Bi3+,Zn2+ codoping enhances the cyan emission of CGO:0.02Bi3+ by 4.1 times due to the influence of morphology and size of phosphor particles, charge compensation and lattice distortion. Interestingly, codoping La3+ ions into the current system can achieve a photoluminescence tuning of CGO:0.02Bi3+ from cyan to yellowish‐green by crystallographic site engineering. Besides, Bi3+–Eu3+ energy transfer is successfully realized in CGO:0.02Bi3+,0.07Zn2+,nEu3+ phosphors and the emission color tuning from cyan to orange is observed. The investigation of thermal quenching behaviors reveals that the incorporation of Zn2+ and La3+ improves the thermal stability of CGO:0.02Bi3+. Finally, CGO:0.02Bi3+,0.07Zn2+,0.10Eu3+ phosphor is employed to obtain a single‐phased warm WLED device. A full‐spectrum WLED device with remarkable color rendering index (Ra) of 97.4 and high luminous efficiency of 69.72 lm W−1 is generated by utilizing CGO:0.02Bi3+,0.07Zn2+ phosphor. This result suggests the important effect of CGO:0.02Bi3+,0.07Zn2+ phosphor on closing the cyan gap, providing new insights of cyan‐emitting phosphors applied in full‐spectrum white lighting.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yun, Xiangyan, Zhou, Jun, Zhu, Yaohui, Molokeev M. S., Jia, Yetong, Wei, Chao, Xu, Denghui, Sun, Jiayue
Заглавие : Thermometry and up-conversion luminescence of Ln3+ (Ln = Er, Ho, Tm)-doped double molybdate LiYbMo2O8
Место публикации : J. Mater. Sci.: Mater. Electron. - 2020. - Vol. 31, Is. 21. - P.18370-18380. - ISSN 0957-4522, DOI 10.1007/s10854-020-04382-8. - ISSN 1573-482X(eISSN)
Примечания : Cited References: 41. - This work is supported by the National Natural Science Foundation of China (No. 21576002 and 61705003) and Beijing Technology and Business University Research Team Construction Project (No. PXM2019_014213_000007)
Предметные рубрики: TEMPERATURE SENSING BEHAVIOR
OPTICAL THERMOMETRY
EMISSION
PHOSPHOR
Аннотация: The discovery of stable and highly sensitive up-conversion (UC) phosphors using the fluorescence intensity ratio (FIR) is a significant challenge in the field of optical temperature sensor. Er3+/Ho3+/Tm3+-doped LiYbMo2O8 UC phosphors with excellent luminescence properties were successfully synthesized through a high-temperature solid-state reaction, and the crystal structure and UC luminescence properties were discussed in detail. The UC process has been investigated by spectra pump power dependence and further explained via the energy level diagram. All emission processes about Er3+ ions and Ho3+ ions are two-photon processes and the blue emission process about Tm3+ ions is a combination of two-photon process and three-photon process. Thermal sensing performances depended on FIR technology were estimated and the sensitivities of LiYb1−xMo2O8:xLn3+ included absolute sensitivity (Sa) and relative sensitivity (Sr) can produce particular change rules with the temperature, which can serve as excellent candidates for applications in optical temperature sensing. With the increase of temperature, the maximum values of Sr of LiYb1−xMo2O8:xLn3+ are 1.16% K−1 (0.05Er3+), 0.25% K−1 (0.01Ho3+), and 0.51% K−1 (0.01Tm3+), respectively. In addition, the Sa value of LiYb0.95Mo2O8:0.05Er3+ phosphor will reach the maximum (1.08% K−1) at 475 K, while the maximum values of Sa of LiYb0.99Mo2O8:0.01Ho3+ and LiYb0.99Mo2O8:0.01Tm3+ are 0.16% K−1, 0.14% K−1.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang, Guangqing, Molokeev M. S., Ma, Qianchao, Yang, Xuening, Han, Shuiquan, Chen, Q.i., Zhong, Binnian, Ma, Bin
Заглавие : Structural analysis and optical temperature sensing performance of Eu3+-doped Ba3In(PO4)3
Место публикации : CrystEngComm. - 2020. - Vol. 22, Is. 35. - P.5809-5817. - ISSN 1466-8033, DOI 10.1039/d0ce00997k
Примечания : Cited References: 52. - This work was supported by the National Natural Science Foundation of China (Grant No. 51802172) and the Qinghai Provincial Natural Science Foundation for Young Scholars (No. 2018-ZJ-957Q)
Предметные рубрики: FLUORESCENCE INTENSITY RATIO
UP-CONVERSION EMISSIONS
RARE-EARTH IONS
Аннотация: Eu3+-Doped Ba3In(PO4)3 was synthesized through a high-temperature solid-phase method. According to the structure refinement based on X-ray diffraction and density functional theory, the crystal and energy band structures of Ba3In(1−x)(PO4)3:xEu3+ were studied and analyzed in detail. The effect of Eu3+ doping concentrations on emission was studied at an excitation wavelength of 393 nm. For the material Ba3In(1−x)(PO4)3:xEu3+(x = 0.01–0.30), the optimal doping level is confirmed to be 0.18. Due to the thermal quenching differences of Eu3+ at the 5D0 and 5D1 energy levels, and based on the temperature-variable fluorescence intensity ratio between emission peaks, the optical temperature measurement performance of this material in the temperature range from 298.15 K to 623.15 K was characterized, and the maximum absolute and relative sensor sensitivities (Sa and Sr) were determined to be 0.1002 K−1 and 4.058%, respectively. With temperature as the only variable, the color of the phosphor changes from red to yellow light with rising temperature. Besides, Sa and Sr values of this phosphor are comparable to other sensing materials. The results indicate that Eu3+-doped Ba3In(PO4)3 phosphors have great potential to be applied in optical temperature sensing.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Maksimov D. N., Bogdanov A. A., Bulgakov E. N.
Заглавие : Optical bistability with bound states in the continuum in dielectric gratings
Коллективы : Government of the Russian Federation through the ITMO Fellowship; Ministry of Science and Higher Education of Russian Federation, goszadanie [2019-1246]; RFBRRussian Foundation for Basic Research (RFBR) [18-32-20205]
Место публикации : Phys. Rev. A. - 2020. - Vol. 102, Is. 3. - Ст.033511. - ISSN 2469-9926, DOI 10.1103/PhysRevA.102.033511. - ISSN 2469-9934(eISSN)
Примечания : Cited References: 53. - This work was financially supported by the Government of the Russian Federation through the ITMO Fellowship and Professorship Program. A.A.B. also acknowledges support by the Ministry of Science and Higher Education of Russian Federation, goszadanie No. 2019-1246 and RFBR (18-32-20205)
Предметные рубрики: COUPLED-MODE THEORY
WAVE-GUIDE
TRANSITION
RESONANCE
ARRAYS
Аннотация: We consider light scattering by dielectric gratings supporting optical bound states in the continuum. Due to the presence of instantaneous Kerr nonlinearity critical field enhancement in the spectral vicinity of the bound state triggers the effect of optical bistability. The onset of bistability is explained theoretically in the framework of the temporal coupled-mode theory. As the central result we cast the problem in the form of a single field-driven nonlinear oscillator. The theoretical results are verified in comparison with numerical simulations.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chirkin A. S.
Заглавие : General formula for the natural width of optical parametric oscillator spectral lines
Место публикации : Laser Phys. Lett. - 2020. - Vol. 17, Is. 11. - Ст.115401. - ISSN 1612-2011, DOI 10.1088/1612-202X/abb6e6. - ISSN 1612-202X(eISSN)
Примечания : Cited References: 21
Предметные рубрики: QUANTUM-FLUCTUATIONS
PHASE MEASUREMENTS
STATES
NOISE
Аннотация: A new approach to the quantum analysis of the spectral linewidths of optical parametric oscillators (OPOs) is proposed. The approach is based on introducing a Hermitian frequency deviation operator. The spectral linewidths in the triply resonant OPO above-threshold regime have been calculated. It has been found that the width of the generated spectral line depends on the loss at all interacting frequencies, the photon number of frequency under study, and the threshold photon number of pump. The formula obtained for the spectral width is general; in particular cases, it yields the well-known results. The developed simple approach can be applied to the quantum analysis of the spectra of various oscillatory systems, for example, the multifrequency parametric and non-linear optomechanical interactions and lasers.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Matsynin A. A.
Заглавие : The effect of the impurities on the magnetic, electronic and optical properties of Mn5Ge3
Место публикации : Chin. J. Phys. - 2020. - Vol. 68. - P.9-18. - ISSN 05779073 (ISSN), DOI 10.1016/j.cjph.2020.06.027
Примечания : Cited References: 29. - The reported study was funded by Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Regional Fund of Science to the research projects № № 19-42-240016 : «Control of structural, magnetic, electronic, and optical properties by pressure and intercalation into functional compounds with a spinel structure containing 3d and 4f ions» and 18-42-243009: «New magnetic film nanocomposites based on layered GeO/Mn systems: synthesis, experimental and theoretical study of structural and magnetic properties». The calculations were performed with the computer resources of "Complex modeling and data processing research installations of mega-class" SRC "Kurchatovsky Institute” ( http://ckp.urcki.ru )
Аннотация: Earlier, we experimentally showed a significant effect of oxygen on the magnetic and structural properties of Mn5Ge3 due to the formation of a Nowotny phase of Mn5Ge3Ox. Here, in continuation of this study, we present a theoretical study of the magnetic and electronic properties of Mn5Ge3 and Mn5Ge3Dx (D = B, C, O). It was found that hexagonal Mn5Ge3 is a ferromagnetic metal with two nonequivalent manganese atoms in the structure. Our ab initio calculations also predict the existence of a spin-crossover in Mn5Ge3 under pressure. Impurities reduce saturation magnetization and electrical and thermal conductivity; however, the magnetic susceptibility and Curie temperature increase. Microscopic mechanisms of the effect of the impurities on the magnetic and electronic properties Mn5Ge3 are discussed.
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