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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) : 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) : 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) : Паршин, Александр Михайлович, Баранник, Алексей Владимирович
Заглавие : Оптическое пропускание доменной структуры нематика на поверхности полимера в магнитном поле
Место публикации : Жидк. кристаллы и их практич. использ. - 2020. - Т. 20, Вып. 2. - С. 62-68. - ISSN 1991-3966, DOI 10.18083/LCAppl.2020.2.62; Liq. Cryst. Appl.
Примечания : Библиогр.: 20
Предметные рубрики: LIGHT-SCATTERING
DEFECTS
Аннотация: Исследовано распространение лазерного луча через слой гибридно-упорядоченного нематика с поверхностной линией дисклинации, состоящий из доменов с радиальной конфигурацией нематического директора на пленке поликарбоната. Ориентационная структура в объеме домена трансформируется в планарную одноосную, задаваемую линией дисклинации, либо в гомеотропную под действием магнитного поля. Получена зависимость интенсивности света, прошедшего через слой, от магнитного поля, прикладываемого перпендикулярно поверхности полимера. Оптическое пропускание сопровождалось интерференционными минимумами и максимумами. Представлена модель интерференции света, основанная на двулучепреломлении, учитывающая рассеяние на ориентационно-структурных неоднородностях доменного ансамбля. Из рассмотрения свободной энергии жидкого кристалла и эффектов двулучепреломления выведено аналитическое выражение, устанавливающее зависимость между интенсивностью света и напряженностью магнитного поля, совпадающее с экспериментом.The propagation of a laser beam through a layer of a hybrid ordered nematic on a polycarbonate film is studied. The nematic has a surface disclination line consisting of domains with a radial configuration of the nematic director. The orientational structure in the domain volume can be transformed into a planar uniaxial structure defined by a disclination line or into a homeotropic one under the influence of a magnetic field. The dependence of the light intensity transmitted through the layer on the magnetic field applied perpendicular to the polymer surface is obtained. Optical transmission was accompanied by interference minima and maxima. Light interference model based on birefringence which takes into account scattering by the orientation-structural inhomogeneities of the domain ensemble is presented. Considering the analysis of the liquid crystal free energy and the birefringence effects, an analytical expression is derived. It establishes the relationship between the light intensity and the magnetic field strength, which coincides with the experiment.
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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) : 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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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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10.

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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