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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhou, Cheng, Peng, L.u., Kong, Zihui, Wu, Meihan, Molokeev M. S., Zhou, Zhi, Wang, Jing, Xia, Mao
Заглавие : A high thermal stability Cr3+-doped gallate far red phosphor for plant lighting: structure, luminescence enhancement and application prospect
Место публикации : J. Mater. Chem. C. - 2022. - Vol. 10, Is. 15. - P.5829-5839. - ISSN 2050-7526, DOI 10.1039/d2tc00614f. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 39. - The authors would like to gratefully acknowledge funds from the National Natural Science Foundation of China (Grant no. 51974123), the Distinguished Youth Foundation of Hunan Province (Grant no. 2020JJ2018), Key R & D projects in Hunan Province (2020WK2016 & 2020SK2032), the Hunan High Level Talent Gathering Project (2019RS1077 & 2020RC5007), the Natural Sciences Foundation of Hunan Agricultural University (19QN11), the Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Resource Utilization Science Foundation (19KFXM12), the Changsha Science and technology plan (KH2005114), the Scientific Research Fund of Hunan Provincial Education Department (19C0903) and the Innovation Training Program for College Students of Hunan Province (No. S202010537012)
Предметные рубрики: EMITTING PHOSPHOR
TUNING PHOTOLUMINESCENCE
LEDS
Аннотация: Cationic substitution is a common material modification strategy. Generally, it follows the principles of radius matching, valency equilibrium and stoichiometric substitution. However, radius-mismatched, nonstoichiometric-ratio ion substitution can achieve unexpected experimental results. Such unexpected results are very important for expanding the research of materials, but the modification mechanism is still unclear. In this work, the optical performance of ZnGa2O4:0.02Cr3+ (ZGO:0.02Cr3+) is effectively regulated by chemical unit cosubstitution (Ge4+–Li+/Na+ for Ga3+–Zn2+) and excess cation substitution synergetic strategies, and the thermal stability is retained at 97.7% at room temperature and 150 °C. Ge4+–Li+ and Ge4+–Na+ replace the lattice position of Ga3+–Zn2+ to enhance the photoluminescence (PL) intensity and quantum efficiency (QE) of ZGO:0.02Cr3+. The optimal doping contents of Ge4+–Li+ and Ge4+–Na+ are all 0.3 mol (PL intensity is 130.3% and 153.4% and QE = 77.4% and 85.1%). With further addition of Li+ ions, the emission intensity and QE continued to increase to 176.4% and 83.8%, respectively. The synergistic effect of the mechanism on optical properties is explained via Rietveld refinement, optical band gap energy and thermoluminescence. Finally, LED devices were fabricated by using the ZGO:0.02Cr3+,0.03Ge4+,0.11Li+ phosphor to investigate the effect on plant growth. The growth period was reduced and the fruit quality was improved in dwarf potted tomato, which shows the application prospect in plant growth of the ZGO:0.02Cr3+ phosphor.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gai S. J., Zhou C., Peng L., Wu M. H., Gao P. X., Su L. J., Molokeev M. S., Zhou Z., Xia M.
Заглавие : A novel Cr3+-doped stannate far red phosphor for plant lighting: structure evolution, broad-narrow spectrum tuning and application prospect
Место публикации : Mater. Today Chem. - 2022. - Vol. 26. - Ст.101107. - ISSN 24685194 (ISSN), DOI 10.1016/j.mtchem.2022.101107
Примечания : Cited References: 50. - The authors would like to gratefully acknowledge funds from the National Natural Science Foundation of China (Grant No. 51974123), the Distinguished Youth Foundation of Hunan Province (Grant No.2020JJ2018), the Key R & D projects in Hunan Province (2020WK2016, 2020SK2032, 2021SK2047, 2022NK2044), the Natural Science Foundation of Hunan Province, China (Grant No. 2021JJ40261), the Hunan High Level Talent Gathering Project (2019RS1077&2020RC5007), the Scientific Research Fund of Hunan Provincial Education Department (19C0903), the Natural Sciences Foundation of Hunan Agricultural University, China (Grant No. 19QN11), Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Resource Utilization Science Foundation (19KFXM12), Changsha Science and technology plan (KH2005114 and KH2201428), the Hunan Graduate Scientific Research Innovation Project (2022XC017) and the College Students' Innovative Training (S202110537012 and s202210537079x)
Аннотация: Chemical unit cosubstitution is an effective strategy to regulate the luminescence properties of phosphors, and it has attracted huge attention in the last few years. Following the design principles of the match of effective ion radius, atomic valence equilibrium and stoichiometric substitution, the local structure of crystal can be well customized, which is beneficial to develop high-performance luminescent materials. In this work, Mg2+-Sn4+ sites were cosubstituted by Zn2+-Ti4+ ion pairs in Mg2SnO4: Cr3+, respectively, and the emission spectra was successfully serially tuned from broad-band to narrow-band along with a unique variation trend of blue shift first and then slightly red shift. The photoluminescence excitation (PLE), photoluminescence (PL) spectra, lifetime decay, Raman spectra and electron paramagnetic resonance (EPR) were used to analyze the mechanism of luminescence tuning. Based on the manipulation of local structure, the as-observed distinct luminescence tuning can be well understood by the crystal field theory, nephelauxetic effect and changed Cr3+ capacity in this phosphor. Moreover, the adjusted narrow-band far-red emission spectra peak at 732 nm, matching the characteristic absorption of plant phytochrome PFR, has broad application prospects in the field of plant growth lighting. In addition, light-regulated dwarf potted tomato experiments were carried out to verify the application of far-red light in plant growth.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Arkhipkin V. G., Gunyakov V. A., Myslivets S. A., Zyryanov V. Ya., Shabanov V. F.
Заглавие : Angular tuning of defect modes spectrum in the one-dimensional photonic crystal with liquid-crystal layer
Место публикации : Eur. Phys. J. E. - NEW YORK: SPRINGER, 2007. - Vol. 24, Is. 3. - С. 297-302. - NOV. - ISSN 1292-8941, DOI 10.1140/epje/i2007-10239-7
Примечания : Cited Reference Count: 28
Предметные рубрики: PERIODIC STRUCTURE
REFRACTIVE-INDEX
ENHANCEMENT
LIGHT
LASER
Ключевые слова (''Своб.индексиров.''): 42.25.bs wave propagation, transmission and absorption--42.70.df liquid crystals--42.70.qs photonic bandgap materials--angles of incidence--angular tuning--defect modes--electric polarization--photonic bandgap materials--radiation losses--absorption--defects--light polarization--liquid crystals--one dimensional--phase shift--wave propagation--photonic crystals
Аннотация: A one-dimensional ZrO2/SiO2 photonic crystal with a 4-n -pentyl-4'-cyanobiphenyl (5CB) nematic defect layer was used to investigate the transmission spectra of light polarized parallel and perpendicular to the liquid-crystal director at different angles of incidence. The spectra of the photonic crystal were shown to split into four polarized components T-ij at oblique incidence. When the incident angle increased, the bandgap edges and the defect modes shifted towards short wavelengths, while the amplitudes of the defect modes increased for the transverse magnetic polarization and decreased for the transverse electric polarization. The observed discrepancy between the defect mode amplitudes in the center and near the edges of the photonic bandgap was found to be related to the radiation losses inside the defect layer of a non-ideal photonic crystal. The simulated transmission spectra obtained using recurrence relations and taking into account the decay of defect modes are in good agreement with the experimental data.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu Q., Dang P., Zhang G., Lian H., Li G., Molokeev M. S., Cheng Z., Lin J.
Заглавие : Broad luminescence tuning in Mn2+-doped Rb2Zn3(P2O7)2 via doping level control based on multiple synergies
Место публикации : CrystEngComm. - 2022. - Vol. 24, Is. 31. - P.5622-5629. - ISSN 14668033 (ISSN), DOI 10.1039/d2ce00719c
Примечания : Cited References: 31. - We acknowledge the financial support from the National Natural Science Foundation of China (NSFC No. 51932009, 51720105015, 51929201, 52072349, and 52172166), Projects for the Science and Technology Development Plan of Jilin Province (20210402046GH), and the Natural Science Foundation of Zhejiang Province (LR22E020004)
Аннотация: Here we constructed a series of novel non-centrosymmetric structure phosphors [Rb2Zn3(P2O7)2:Mn2+] by a high-temperature solid-state reaction. The multiband emission can be designed by Mn2+ preferentially occupying three types of crystallographic sites in Rb2Zn3(P2O7)2:Mn2+. The emission color could be continuously tuned from yellow-green to orange-red via multiple synergies among crystallographic site engineering, energy transfer, and Mn-Mn dimmers alone through the dopant concentration. These color-tunable phosphors have good thermal stability (I150 °C/I25 °C = 91%). The as-prepared pc-WLED has a low corresponding color temperature (CCT = 4820 K) and a high color rendering index (Ra = 90.4) with CIE color coordinates of (0.351, 0.358). These results show that emission-tunable Rb2Zn3(P2O7)2:xMn2+ phosphors are potential candidates for application in n-UV-based pc-WLED devices. This study offers a new insight for wide-range tuning of PL properties by using crystallographic site engineering through changing the doping level in Mn-activated phosphors.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Bogdanov E. V., Laptash N. M.
Заглавие : Chemical pressure as an effective tool for tuning the structural disordering and barocaloric efficiency of complex fluorides (NH4)3MF7 (M: Sn, Ti, Ge, Si)
Колич.характеристики :18 с
Место публикации : J. Phys. D: Appl. Phys. - 2024. - Vol. 57, Is. 17. - Ст.175301. - ISSN 00223727 (ISSN), DOI 10.1088/1361-6463/ad211b. - ISSN 13616463 (eISSN)
Примечания : Cited References: 39. - The study was supported by a Grant from the Russian Science Foundation No. 23-22-00115, https://rscf.ru/project/23-22-00115/
Аннотация: Double fluoride salts (NH4)3M4+F7 (M4+: Sn, Ti, Ge, Si) demonstrate a high efficiency of using chemical pressure as a tool for control and tuning structural ordering/disordering, sensitivity to hydrostatic pressure, successions of the phase transitions, etc and, as a result, for purposeful variation within a wide range of parameters of barocaloric effect (BCE). The conventional and inverse BCEs near the triple points were found on the T − p phase diagrams, combination of which can be used to construct original cooling cycle in narrow temperature and pressure ranges. Reconstructive transformation between two cubic phases, Pm3-m ↔ Pa3-, realized in (NH4)3SnF7 at atmospheric pressure and in (NH4)3TiF7 at p ˃ 0.4 GPa are characterized by rather low thermal hysteresis, δT0 = 1 K, and a great entropy change, ΔSBCE = 110–152 J (kg · K)−1, depending on the size of the central atom. At above 300–350 K, a contribution to BCE associated with the regular thermal expansion of the crystal lattice becomes comparable to entropy and temperature changes under pressure in the region of the phase transitions. An analysis of the absolute, relative and integral barocaloric characteristics of (NH4)3M4+F7 compounds showed their high competitiveness with respect to other barocaloric materials considered as promising solid-state refrigerants.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xia, Zhiguo, Ma C., Molokeev M. S., Liu Q., Rickert K., Poeppelmeier K. R.
Заглавие : Chemical unit cosubstitution and tuning of photoluminescence in the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ phosphor
Место публикации : J. Am. Chem. Soc.: American Chemical Society, 2015. - Vol. 137, Is. 39. - P.12494-12497. - ISSN 0002-7863, DOI 10.1021/jacs.5b08315
Примечания : Cited References: 24. - This work was supported by the National Natural Science Foundations of China (Grant Nos. 51572023 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), and the Funds of the State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, CAS (RERU2015022). C.M. acknowledges financial support from National Natural Science Foundation of China (Grant No. 11204393), Natural Science Foundation Project of Chongqing (Grant No. CSTC2014JCYJA50034), and National Training Programs of Innovation and Entrepreneurship for Undergraduates (Grant No. 201410617001). K.R. recognizes that this material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-1324585.
Предметные рубрики: LUMINESCENCE PROPERTIES
TRANSITIONS
IONS
Аннотация: The union of structural and spectroscopic modeling can accelerate the discovery and improvement of phosphor materials if guided by an appropriate principle. Herein, we describe the concept of chemical unit cosubstitution as one such potential design scheme. We corroborate this strategy experimentally and computationally by applying it to the Ca2(Al1-xMgx)(Al1-xSi1+x)O7:Eu2+ solid solution phosphor. The cosubstitution is shown to be restricted to tetrahedral sites, which enables the tuning of luminescent properties. The emission peaks shift from 513 to 538 nm with a decreasing Stokes shift, which has been simulated by a crystal-field model. The correlation between the 5d crystal-field splitting of Eu2+ ions and the local geometry structure of the substituted sites is also revealed. Moreover, an energy decrease of the electron-phonon coupling effect is explained on the basis of the configurational coordinate model. © 2015 American Chemical Society.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zheng Y., Zhang H., Zhang H., Xia Z., Liu Y., Molokeev M. S., Lei B.
Заглавие : Co-substitution in Ca1−xYxAl12−xMgxO19 phosphors: local structure evolution, photoluminescence tuning and application for plant growth LEDs
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 15. - P.4217-4224. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc00165k
Примечания : Cited References: 47. - The present work was supported by the National Natural Science Foundation of China (Grant No. 21671070), the Project for Construction of High-level University in Guangdong Province, and the Teamwork Projects funded by the Guangdong Natural Science Foundation (Grant No. S2013030012842), and the Guangzhou Science & Technology Projects (No. 201704030086, 201605030005), and the reported study was funded by the RFBR according to the research project 17-52-53031. Special Funds for the Cultivation of Guangdong College Students’ Scientific and Technological Innovation (‘‘Climbing Program’’ Special Funds) were granted for Dr Yinjian Zheng.
Ключевые слова (''Своб.индексиров.''): co substitution--crystal structure transformation--high temperature solid-state reaction--lighting systems--local structure--luminescence measurements--structural refinement--tunable luminescences
Аннотация: Herein, Mn4+-activated Ca1-xYxAl12-xMgxO19 (x = 0-0.50) solid solutions were prepared using a conventional high-temperature solid-state reaction. Crystal structure transformation via chemical co-substitution of Y3+/Mg2+ for Ca2+/Al3+ was investigated in detail. The optical properties of Ca1-xYxAl12-xMgxO19 (x = 0-0.50) have been reported for the first time using a combination of techniques including structural refinement and luminescence measurements. Co-doping of Mg and Y cations within the CaAl12O19 host in a controlled manner resulted in the as-prepared samples with red/far-red ratio-tunable luminescence properties. The emission bands well-matched with the absorption band of phytochrome. Interestingly, enhanced Mn4+ luminescence can be obtained upon the addition of Mg2+ and Y3+. Unexpectedly, the quantum yields exhibit a slight change when x is in the range from 0.05 to 0.40; this indicates that these solid solutions have significant potential as lighting systems for plant growth.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazakova M. A., Semikolenova N. V., Korovin E. Y., Zhuravlev V. A., Selyutin A. G., Velikanov D. A., Moseenkov S. I., Andreev A. S., Lapina O. B., Suslyaev V. I., Matsko M. A., Zakharov V. A., Lacaillerie J. -B.D.D.
Заглавие : Co/multi-walled carbon nanotubes/polyethylene composites for microwave absorption: Tuning the effectiveness of electromagnetic shielding by varying the components ratio
Место публикации : Compos. Sci. Technol. - 2021. - Vol. 207. - Ст.108731. - ISSN 02663538 (ISSN), DOI 10.1016/j.compscitech.2021.108731
Примечания : Cited References: 45. - This work was supported by the Ministry of Science and Higher Education of the Russian Federation within the state assignment for Boreskov Institute of Catalysis (project # АААА-А21-121011390054-1)
Аннотация: We present novel polyethylene (PE) composites for electromagnetic interference (EMI) shielding application. They are based on cobalt modified multi-walled carbon nanotubes (MWCNTs) produced via in situ polymerization of ethylene, with the Ti-Ziegler–Natta catalyst preliminarily immobilized on Co/MWCNT hybrids. The electromagnetic properties of the composites were tuned by varying the filler loading and Co:MWCNT ratio. The microstructure of the composites and electromagnetic absorption process were carefully characterized by transmission and scanning electron microscopy, X-ray diffraction, vibrating sample magnetometry, ferromagnetic resonance and vector network analysis. The electromagnetic wave absorbing properties of the nanocomposite were investigated in the 10 MHz−18 GHz frequency range revealing that the EMI absorption properties can be tuned by varying the Co:MWCNT weight ratio in the filler. Interestingly, the Co/MWCNT-PE composite with a total filler and Co loading of only 12 and 1.7 wt%, respectively, showed extremely high reflection loss (RL) of −55 dB. More importantly, an effective bandwidth of 12.8–17.8 GHz (RL below −10 dB) was achieved for a matching thickness of only 1.5 mm. The specific RL value (RL/filler loading) of the composite was superior in comparison with the previously reported nanostructured carbon materials. The highly effective absorbing properties of Co/MWCNT-PE composites are explained primarily by the unprecedented uniform filler distribution in the polyethylene as well as by the synergistic effect of MWCNTs and Co nanoparticles. This approach thus offered an effective strategy to design cost-effective, lightweight and flexible EMI shielding materials with tunable dielectric and magnetic performance.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liang S. S., Dang P. P., Li G. G., Molokeev M. S., Wei Y., Lian H. Z., Shang M. M., Al Kheraiff A. A., Lin J.
Заглавие : Controllable two-dimensional luminescence tuning in Eu2+,Mn2+ doped (Ca,Sr)9Sc(PO4)7 based on crystal field regulation and energy transfer
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 25. - P.6714-6725. - ISSN 2050-7526, DOI 10.1039/c8tc01825a. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 63. - This work was financially supported by the National Natural Science Foundation of China (NSFC No. 51672265, 51672266, 21521092, 51750110511, 51672257, and 51672259), the Key Research Program of Frontier Sciences of CAS (Grant No. YZDY-SSW-JSC018), the National Basic Research Program of China (2014CB643803), the Scientific and Technological Department of Jilin Province (Grant No. 20150520029JH and 20170414003GH), Jiangmen Innovative Research Team Program (2017) and Major Program of Basic Research and Applied Research of Guangdong Province (2017KZDXM083), the Russian Science Foundation (Grant No. 17-12-01047), and the Distinguished Scientist Fellowship Program of King Saud University, as well as the Deanship of Scientific Research at King Saud University through research group no. (RG-1939-038).
Предметные рубрики: SOLID-SOLUTION PHOSPHORS
LIGHT-EMITTING-DIODES
CATION SUBSTITUTION
Аннотация: Currently, controllable luminescence tuning and the generation of single component white emission are viable strategies to modify and optimize the luminescence performances of phosphors, which offer appealing prospects for the w-LED lighting industry. In this paper, we designed two-dimensional (2D) tunable color coordinates on the CIE diagram in the Eu2+,Mn2+ doped (Ca,Sr)9xSc(PO4)7 system by a combination of crystal field regulation and the energy transfer method. X-ray powder diffraction (XRD) and Rietveld refinement were utilized to analyze the phase composition and structural variation of the studied phosphors. The transmission electron microscopy (TEM) and photoluminescence spectra were exploited to analyze the generation of nanosegregation. The effects of the schedule of cation substitutions and energy transfer on the photoluminescence properties were investigated in detail. The corresponding luminescence mechanisms of the red-shifted emission with Sr2+ → Ca2+ substitution and Eu2+ → Mn2+ energy transfer were deeply discussed and proposed. In addition, the temperature-dependent thermal quenching behavior and the electroluminescence (EL) performance of the fabricated w-LED devices were also investigated to characterize the prepared Ca9(1−0.03−x−y)Sr9xSc(PO4)7:0.27Eu2+,9yMn2+. Finally, a representative w-LED device composed of a 369 nm UV chip and Ca9(1−0.03−0.02−0.5)Sr4.5Sc(PO4)7:0.27Eu2+,0.18Mn2+ could present excellent EL performance with the parameters CRI = 88, CCT = 3122 K and color coordinate (0.45, 0.44), which could well meet the commercial standard of warm white light. Therefore, our results suggest that this two-step luminescence tuning method is feasible to be applied in other phosphor systems for obtaining efficient white emitting phosphors.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lai S., Zhao M., Qiao J., Molokeev M. S., Xia Z.
Заглавие : Data-driven photoluminescence tuning in Eu2+-doped phosphors
Место публикации : J. Phys. Chem. Lett. - 2020. - Vol. 11, Is. 14. - P.5680-5685. - ISSN 19487185 (ISSN), DOI 10.1021/acs.jpclett.0c01471
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundations of China (Grant No. 51972118, 51961145101 and 51722202), Fundamental Research Funds for the Central Universities (D2190980), Guangzhou Science & Technology Project (202007020005), Guangdong Provincial Science & Technology Project (No. 2018A050506004), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137). This work is also funded by RFBR according to the research project No. 19-52-80003
Предметные рубрики: Phosphors
Luminescence properties
Crystal structure
Ions
Quantum mechanics
Аннотация: Discovery of rare earth phosphors has generally relied on the chemical intuition and time-intensive trial-and-error synthesis; therefore, finding new materials assisted by data-driven computations is urgent. Herein, we utilize a regression model to predict the emission wavelengths of Eu2+-doped phosphors by revealing the relationships between the crystal structure and luminescence property. The emission wavelengths of [Rb(1–x)K(x)]3LuSi2O7:Eu2+ (0 ≤ x ≤ 1) phosphors, as examples for the data-driven photoluminescence tuning, are successfully predicted on the basis of the existing data of only eight systems, also consistent with the experimental results. These phosphors can be excited by blue light and exhibit broad-band red and near-infrared emission ranging from 619 to 737 nm. These findings in Eu2+-doped silicate phosphors indicate that data-driven computations through the regression mode would have bright application in discovering novel phosphors with a target emission wavelengths.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang H.-T., Wu P.-C., Timofeev I. V., Zyryanov V. Ya., Lee W.
Заглавие : Dynamic tuning and memory switching of defect modes in a hybrid photonic structure
Место публикации : Crystals. - 2016. - Vol. 6, Is. 10. - Ст.129. - ISSN 20734352 (ISSN), DOI 10.3390/cryst6100129
Примечания : Cited References: 32. - This work was financially sponsored by the Ministry of Science and Technology (MOST), Taiwan, under grant No. 103-2923-M-009-003-MY3, the Ministry of Education and Science of the Russian Federation under state order No. 3.1276.2014/K, and by the Siberian Branch of the Russian Academy of Sciences under Complex Program II.2P (projects Nos. 0358-2015-0010 and 0358-2015-0011).
Ключевые слова (''Своб.индексиров.''): dual-frequency liquid crystals--energy-efficient photonic devices--photonic crystals
Аннотация: We propose a memorable and electrically tunable photonic device by infiltrating a dual-mode chiral-doped dual-frequency liquid crystal (LC) as the central defect layer in a one-dimensional photonic crystal (PC). According to the transmission properties of this structure, the wavelength tunability of defect modes is obtained by manipulating the LC layer in the dynamic mode due to the electrically controlled birefringence effect. Moreover, the switching between two memorable states, the splay and π-twist states, creates two distinct sets of defect modes at null voltage. The spectral characteristics of this device ensure its potential application as an energy-efficient multichannel wavelength filter.
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12.

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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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Lai S., Zhao M., Zhao Y., Molokeev M. S., Xia Z.
Заглавие : Eu2+Doping concentration-induced site-selective occupation and photoluminescence tuning in KSrScSi2O7:Eu2+ phosphor
Место публикации : ACS. Mater. Au. - 2021. - Vol. 2, Is. 3. - P.374-380. - ISSN 26942461 (ISSN), DOI 10.1021/acsmaterialsau.1c00081
Примечания : Cited References: 43. - This work was supported by the International Cooperation Project of National Key Research and Development Program of China (2021YFE0105700), the National Natural Science Foundations of China (Grant Nos. 51972118 and 51961145101), the Guangzhou Science & Technology Project (202007020005), the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137), and the China Postdoctoral Science Foundation (2021M700298). This work was also funded by RFBR according to research project No. 19-52-80003
Аннотация: Regulation of Eu2+ dopants in different cation sites of solid-state materials is of great significance for designing multicolor phosphors for light-emitting diodes (LEDs). Herein, we report the selective occupation of Eu2+ for multiple cationic sites in KSrScSi2O7, and the tunable photoluminescence from blue to cyan is realized through Eu2+ doping concentration-dependent crystal-site engineering. Eu2+ preferably occupies the K and Sr sites in KSrScSi2O7 at a low doping concentration, resulting in a 440 nm blue emission. As the Eu2+ concentration increases, a new Eu2+ substitution pathway is triggered, that is, Eu2+ enters the Sc site, leading to the red-shifted emission spectra from 440 to 485 nm. The doping mechanism and photoluminescence properties are corroborated by structural analysis, optical spectroscopy study, and density functional theory calculations. The optical properties of the as-fabricated white LEDs are studied, which demonstrates that these phosphors can be applied to full-spectrum phosphor-converted LEDs. This study provides a new design strategy to guide the development of multicolor Eu2+-doped oxide phosphors for lighting applications.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yan W., Wei Y., Molokeev M. S., Wang S., Li G.
Заглавие : Green-emitting Bi3+-doped La2SrSc2O7 phosphor for pc-WLED lighting: Luminescent properties and energy transfer strategy
Место публикации : J. Alloys Compd. - 2022. - Vol. 908. - Ст.164621. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2022.164621
Примечания : Cited References: 63. - This work was supported by the National Natural Science Foundation of China (Grant Nos. 52072349)
Аннотация: The crystal structure, photoluminescence properties, thermal stability and corresponding mechanisms of the novel Bi3+, Eu3+-doped La2SrSc2O7 (LSS) phosphors have been measured and analyzed in details. The emission spectrum of LSS: 1.0%Bi3+ phosphor shows a novel green emission centered at 530 nm under 340 nm excitation, which is attributed to the 3P1→1S0 transition of Bi3+ ions. By designing Bi3+→Eu3+energy transfer strategy, luminescence colors of LSS: 1.0%Bi3+, yEu3+ (y = 0–5.0%) phosphors can be tuned from green to orange with increasing Eu3+ concentration, which achieve multiple emission colors in LSS host. The photoluminescence decay curves, average decay lifetimes, energy transfer efficiency and time-resolved emission spectra of LSS: 1.0%Bi3+, yEu3+ (y = 0–5.0%) phosphors prove the existence of energy transfer from Bi3+ to Eu3+. The prototype pc-WLED device with green-emitting LSS: 1.0%Bi3+ possesses high color rendering index (CRI = 96.0) and low correlated color temperature (CCT = 4306 K). These results provide clear evidences that LSS: Bi3+and LSS: 1.0%Bi3+, Eu3+ phosphors would be novel promising green-to-orange tunable phosphor candidates for pc-WLED applications.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Liu Q.
Заглавие : Insights into Ba4Si6O16 structure and photoluminescence tuning of Ba4Si6O16:Ce3+,Eu2+ phosphors
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2015. - Vol. 3, Is. 48. - P.12477-12483. - ISSN 20507534 (ISSN), DOI 10.1039/c5tc03271g
Примечания : Cited References: 39. - This work was supported by the National Natural Science Foundations of China (Grant No. 51572023 and 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306), and Fundamental Research Funds for the Central Universities (FRF-TP-14-005A1).
Предметные рубрики: LIGHT-EMITTING-DIODES
ENERGY-TRANSFER
LUMINESCENCE PROPERTIES
WHITE-LIGHT
GLASS-CERAMICS
BA PHOSPHORS
EMISSION
GREEN
EU2+
FLUORESCENCE
Аннотация: The versatile polymorphism and chemical compositions of barium silicates have been studied for a long time and their crystal structures have been established. Herein, we focused on the understanding of the crystal structure of the Ba4Si6O16 phase and the structural correlation of Ba4Si6O16 and Ba2Si3O8; moreover, the luminescence properties of Ce3+,Eu2+-co-activated Ba4Si6O16 phosphors have been discussed. Ba4Si6O16:Ce3+,Eu2+ phosphors show tunable blue-green emission upon excitation with 365 nm ultraviolet (UV) light. The blue emission originates from Ce3+, whereas the bluish-green emission is ascribed to Eu2+, and variation in the emission peak wavelength from 442 to 497 nm can be achieved by properly tuning the Ce3+/Eu2+ ratio. Energy transfer from Ce3+ to Eu2+ in the Ba4Si6O16 host has been validated by the variation of emission spectra as well as the variation of Ce3+ decay lifetimes with increasing Eu2+ concentration, and the energy transfer mechanism is demonstrated to be a resonant type via a dipole-dipole process. The results suggest that Ba4Si6O16:Ce3+,Eu2+ phosphors are potential candidates as a blue-green component for UV-excited white light-emitting diodes. © 2015 The Royal Society of Chemistry.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhao M., Xia Z., Huang X., Ning L., Gautier R., Molokeev M. S., Zhou Y., Chuang Y. -C., Zhang Q., Liu Q., Poeppelmeier K. R.
Заглавие : Li substituent tuning of LED phosphors with enhanced efficiency, tunable photoluminescence, and improved thermal stability
Место публикации : Science Adv. - 2019. - Vol. 5, Is. 1. - Ст.eaav0363. - ISSN 2375-2548, DOI 10.1126/sciadv.aav0363
Примечания : Cited References: 38. - This research was supported by the National Natural Science Foundation of China (nos. 51722202, 91622125, 51572023, and 11574003) and Natural Science Foundations of Beijing (2172036), and this work was also supported by funding from the National Science Foundation (award DMR-1608218) and French National Agency for Research (ANR Young Researchers: ANR-16-CE08-0003-01).
Предметные рубрики: MATERIALS SCIENCE
Аннотация: Solid-state phosphor-converted white light-emitting diodes (pc-WLEDs) are currently revolutionizing the lighting industry. To advance the technology, phosphors with high efficiency, tunable photoluminescence, and high thermal stability are required. Here, we demonstrate that a simple lithium incorporation in NaAlSiO4:Eu system enables the simultaneous fulfillment of the three criteria. The Li substitution at Al sites beside Na sites in NaAlSiO4:Eu leads to an enhanced emission intensity/efficiency owing to an effective Eu3+ to Eu2+ reduction, an emission color tuning from yellow to green by tuning the occupation of different Eu sites, and an improvement of luminescence thermal stability as a result of the interplaywith Li-related defects. A pc-WLED using the Li-codoped NaAlSiO4:Eu as a green component exhibits improved performance. The phosphorswithmultiple activator sites can facilitate the positive synergistic effect on luminescence properties.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Balaev D. A., Krasikov A. A., Knyazev Yu. V., Yaroslavtsev R. N., Velikanov D. A., Mikhlin Yu. L., Volochaev M. N., Bayukov O. A., Ladygina V. P., Stolyar S. V., Iskhakov R. S.
Заглавие : Magnetic collective state formation upon tuning the interparticle interactions in ensembles of ultrafine ferrihydrite nanoparticles
Колич.характеристики :13 с
Место публикации : Nano-Struct. Nano-Objects. - 2024. - Vol. 37. - Ст.101089. - ISSN 2352507X (ISSN), DOI 10.1016/j.nanoso.2023.101089. - ISSN 23525088 (eISSN)
Примечания : Cited References: 93. - The authors thank M.N. Volochaev for the TEM investigations
Аннотация: The results of a study of the dynamic (alternating current magnetic susceptibility) and static magnetic properties, as well as 57Fe Mössbauer spectrometry and ferromagnetic resonance of two-line ferrihydrite nanoparticle systems with varying intensities of magnetic interparticle interactions are reported. The strength of the magnetic interparticle interactions has been tuned by coating (with various degrees of coating) the ferrihydrite particles (2–4 nm in size and an average size ∼2.7 nm) of the initial synthetic sample by arabinogalactan. Also, a biogenic ferrihydrite sample (an average particle size of 2-nm) with a natural organic coating was studied and it has the weakest magnetic interparticle interactions among of all the samples. Relaxation times of the particle’s magnetic moment were determined by the data of static and dynamic magnetic susceptibilities and from analysis of 57Fe Mössbauer spectrometry. Based on the temperature dependences of the relaxation times, it has been concluded that the predominantly collective processes of freezing of the particle magnetic moments occur under the action of the magnetic interparticle interactions. It is shown that an important role in these processes is played by a magnetic subsystem of the surface spins of the particles. The effect of the interplay between the surface spin and magnetic moment subsystems on the static magnetic properties (low-temperature magnetic hysteresis loops) and the parameters of the microwave absorption line under the magnetic resonance conditions is discussed.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gao P., Li Q., Li S., Gai S., Li Y., Ma Y., Zhang Z., Molokeev M. S., Zhou Z., Xia M.
Заглавие : Multiple strategies to approach high-efficiency luminescence controllable in blue/cyan/green-emitting Bi3+-activated phosphors
Место публикации : J. Phys. Chem. C. - 2022. - Vol. 126, Is. 21. - P.9195-9206. - ISSN 19327447 (ISSN), DOI 10.1021/acs.jpcc.2c02560
Примечания : Cited References: 53. - The authors would like to gratefully acknowledge funds from the National Natural Science Foundation of China (grant no. 51974123), the Distinguished Youth Foundation of Hunan Province (grant no.2020JJ2018), the Key R&D projects in Hunan Province (2020WK2016, 2020SK2032, 2021SK2047, and 2022NK2044), the Natural Science Foundation of Hunan Province, China (grant no. 2021JJ40261), the Hunan High Level Talent Gathering Project (2019RS1077 and 2020RC5007), the Scientific Research Fund of Hunan Provincial Education Department (19C0903), the Natural Sciences Foundation of Hunan Agricultural University, China (grant no. 19QN11), the Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Resource Utilization Science Foundation (19KFXM12), the Changsha Science and Technology Plan (KH2005114, KH2201428), and the College Students’ Innovative Training (S202110537012)
Аннотация: Cyan gap is a major block in achieving high-quality white light-emitting diodes (WLEDs). Hence, a novel cyan-emitting phosphor Sr2GdGaO5/0.02Bi3+ with optical tuning performance is synthesized based on the local crystal field regulation strategy surrounding the luminescence center. With the substitution of Al3+ for Ga3+, the photoluminescence (PL) spectra of Sr2GdGa1–xAlxO5/0.02Bi3+ (0 ≤ x ≤ 1) phosphors adjust from cyan (466 nm) to blue (450 nm). Moreover, such a Ba2+ doping adjusts the PL spectra of Sr2–xBaxGdGaO5/0.02Bi3+ (0 ≤ x ≤ 0.5) phosphors from cyan (466 nm) to green (482 nm). These phenomena are contributed to the crystal field splitting and nephelauxetic effect. The energy transfer from Bi3+ to Eu3+ is realized by co-doping Bi3+ and Eu3+ ions in the A2GdBO5/Bi3+ (A = Sr, Ba; B = Ga, Al) host materials, and two single-phase white phosphors Sr2GdGaO5/0.02Bi3+, 0.05Eu3+ and Sr1.5Ba0.5GdGaO5/0.02Bi3+, 0.05Eu3+ are obtained. Finally, a WLED with high color rendering index (Ra = 93.6) is prepared by using red/green/blue (RGB) phosphors and Sr2GdGaO5/0.02Bi3+ phosphor, which is higher than that of the WLED prepared by RGB phosphors (Ra = 86.7), indicating that Sr2GdGaO5/0.02Bi3+ phosphor can close the cyan gap. These results provide multiple strategies in achieving luminescence controllable and WLED.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang M., Xia Z., Molokeev M. S., Shi L., Liu Q.
Заглавие : New insight into the crystal structure of Sr4Ca(PO4)2SiO4 and the photoluminescence tuning of Sr4Ca(PO4)2SiO4:Ce3+,Na+,Eu2+ phosphors
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2016. - Vol. 4, Is. 38. - P.9078-9084. - ISSN 20507534 (ISSN), DOI 10.1039/c6tc03373c
Примечания : Cited References: 31
Ключевые слова (''Своб.индексиров.''): calcium--energy transfer--europium--light emission--light emitting diodes--luminescence--phosphate minerals--phosphors--photoluminescence--positive ions--rietveld refinement--tuning--chemical compositions--energy transfer mechanisms--green component--hexagonal cells--luminescence properties--single phase--solid state method--white lightemitting diodes (wleds)--crystal structure
Аннотация: A new single phase based on the substitution of a Sr cation by a Ca cation in the apatite-type Sr5(PO4)2(SiO4) has been fabricated with the nominal chemical composition of Sr4Ca(PO4)2(SiO4), which appears as a definite compound rather than a solid solution between (Sr,Ca)3(PO4)2 and (Sr,Ca)2SiO4. The crystal structure of Sr4Ca(PO4)2(SiO4) has been firstly analysed by the difference electron map, and further resolved by the Rietveld refinement, and the final composition has been determined as Sr4Ca(PO4)(2+x)(SiO4)(1-x)(OH)x (x = 0.64) with a hexagonal cell (P63/m). The Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been designed and prepared by the solid state method, and the photoluminescence tuning from blue to green upon 365 nm ultraviolet (UV) radiation can be realized, which is ascribed to the energy transfer from Ce3+ to Eu2+ ions. The luminescence properties and the energy transfer mechanism in Ce3+/Eu2+ codoped Sr4Ca(PO4)2SiO4 phosphors have been discussed, which might act as potential candidates for blue-green components in UV-pumped white light emitting diodes (WLEDs). © 2016 The Royal Society of Chemistry.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gao P. -X., Dong P., Zhou Z. -Y., Zhang X. -J., Li Y. -N., Yang J. -K., Li Q., Chen K., Molokeev M. S., Zhou Z., Xia M.
Заглавие : Novel far-red phosphors (La, Gd, Y)2MgTiO6:Cr3+ with tunable luminescence spectra for grow light
Разночтения заглавия :
Место публикации : Faguang Xuebao/Chin. J. Lumines. - 2022. - Vol. 43, Is. 1. - P.58-68. - ISSN 10007032 (ISSN), DOI 10.37188/CJL.20210327
Примечания : Cited References: 27. - Supported by National Natural Science Foundation of China(51974123); The Distinguished Youth Foundation of Hunan Province(2020JJ2018); Key R & D Projects in Hunan Province(2020WK2016&2020SK2032&2022NK2044), Hunan High Level Talent Gathering Project(2019RS1077&2020RC5007); Natural Science Foundation of Hunan Province(2021JJ40261); The Scientific Research Fund of Hunan Provincial Education Department(19C0903); The Natural Sciences Foundation of Hunan Agricultural University(19QN11); Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Resource Utilization Science Foundation(19KFXM12); Changsha Science and Technology Plan(KH2005114)
Аннотация: Cr3+-activated double perovskite structure phosphor has drawn wide attention due to its far-red and near-infrared emission. In this work, we synthesized a series of (La,Gd,Y)2MgTiO6∶Cr3+ phosphors which can be excited by ultraviolet light of about 345 nm, and the emission bands are in the range of 700-900 nm. The spectra were tuned by ions substitution strategy. The main emission peaks were blue shifted from 766 nm to 737 nm and 757 nm by substituting the La site with Gd and Y, respectively. Meanwhile, the thermal stability at 150 ℃ increased from 41.7% to 69.1% and 67%, respectively. The crystal structure, microstructure, decay time, thermal stability and band gap were investigated systematically. The substitution of Gd/Y ions causes the lattice contraction, which results in the change of the nephelauxetic effect, and eventually leads to the blue shift of the spectra. The emission spectra of these phosphors have good matching with the 730 nm absorption peak of phytochrome FR(PFR), indicating their application prospect in plant growth lighting. Cationic substitution strategy can regulate the luminescence properties of Cr3+, which provides ideas for the development of phosphors for plant growth lamps in the future.
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