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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mishra S., Yogi P., Chaudhary A., Pathak D. K., Saxena S. K., Krylov A. S., Sagdeo P. R., Kumar R.
Заглавие : Understanding perceived color through gradual spectroscopic variations in electrochromism
Коллективы : Department of Science and Technology (DST), Govt. of India; MHRD; CSIR (Govt. of India); DST under FIST scheme [SR/FST/PSI-225/2016]
Место публикации : Indian J. Phys. - 2019. - Vol. 93, Is. 7. - P.927-933. - ISSN 0973-1458, DOI 10.1007/s12648-018-1353-7. - ISSN 0974-9845(eISSN)
Примечания : Cited References: 34. - Authors acknowledge financial support from the Department of Science and Technology (DST), Govt. of India. Authors are thankful to Dr. K. V. Adarsh (IISER Bhopal) for Raman measurements. Authors thank Prof. V.D. Vankar (IIT Delhi) for useful discussions. Authors (AC and DKP) are thankful to MHRD and CSIR (Govt. of India), respectively, for providing fellowships. Support received from DST under FIST scheme (grant number: SR/FST/PSI-225/2016) is also acknowledged.
Предметные рубрики: 3 REDOX FORMS
TUNGSTEN-OXIDE
RAMAN-SPECTRA
VIOLOGEN
SALTS
Аннотация: A bias-dependent in situ Raman scattering and UV–Vis absorption spectroscopic change has been correlated with the corresponding color change of an electrochromic device in an attempt to explain how to understand the relationship between actual perceived color and its absorption/transmittance spectra. For this, the bias across an electrochromic device was increased gradually, rather than abruptly turning ON and OFF, to see subtle variations in Raman and absorption spectra due to bias. Raman scattering establishes that viologen changes its oxidation state reversibly between two redox species (EV2+ to EV+•) as a result of bias-induced dynamic redox process. A gradual variation in Raman and absorption spectra, which shows maximum absorption corresponding to the yellow light, accompanies similar variation in color change of the device as visible by naked eye. These spectroscopic results are correlated with the perceived blue color, in the reflected light, by the eye to understand the actual reason behind this. Maximum absorption of yellow light by the device resulting in blue appearance has been explained using the concept of additive and subtractive primary colors.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liao H., Zhao M., Zhou Y., Molokeev M. S., Liu Q., Zhang Q., Xia Z.
Заглавие : Polyhedron Transformation toward Stable Narrow-Band Green Phosphors for Wide-Color-Gamut Liquid Crystal Display
Место публикации : Adv. Funct. Mater. - 2019. - Vol. 29, Is. 30. - Ст.1901988. - ISSN 1616301X (ISSN) , DOI 10.1002/adfm.201901988
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundations of China (Grant Nos. 51722202, 91622125, and 51572023), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF‐TP‐18‐002C1), and the Guangdong Provincial Science & Technology Project (No. 2018A050506004).
Аннотация: A robust and stable narrow-band green emitter is recognized as a key enabler for wide-color-gamut liquid crystal display (LCD) backlights. Herein, an emerging rare earth silicate phosphor, RbNa(Li3SiO4)2:Eu2+ (RN:Eu2+) with exceptional optical properties and excellent thermal stability, is reported. The resulting RN:Eu2+ phosphor presents a narrow green emission band centered at 523 nm with a full width at half maximum of 41 nm and excellent thermal stability (102%@425 K of the integrated emission intensity at 300 K). RN:Eu2+ also shows a high quantum efficiency, an improved chemical stability, and a reduced Stokes shift owing to the modified local environment, in which [NaO8] cubes replace [LiO4] squares in RbLi(Li3SiO4)2:Eu2+ via polyhedron transformation. White light-emitting diode (wLED) devices with a wide color gamut (113% National Television System Committee (NTSC)) and high luminous efficacy (111.08 lm W−1) are obtained by combining RN:Eu2+ as the green emitter, K2SiF6:Mn4+ as the red emitter, and blue-emitting InGaN chips. Using these wLEDs as backlights, a prototype 20.5 in. LCD screen is fabricated, demonstrating the bright future of stable RN:Eu2+ for wide-color-gamut LCD backlight application.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Hu T., Molokeev M. S., Xia Z., Zhang Q.
Заглавие : Aliovalent substitution toward reinforced structural rigidity in Ce3+-doped garnet phosphors featuring improved performance
Место публикации : J. Mater. Chem. C. - 2019. - Vol. 7, Is. 46. - P.14594-14600. - ISSN 20507534 (ISSN), DOI 10.1039/c9tc05354a
Примечания : Cited References: 38. - This work was supported by the National Natural Science Foundation of China (No. 51722202 and 51972118), the Guangdong Provincial Science & Technology Project (2018A050506004) and the Fundamental Research Funds for the Central Universities (D2190980).
Аннотация: Highly efficient phosphors with thermal stability and color-tunable emission are required for the fabrication of phosphor-converted white light-emitting diodes (pc-WLEDs). Currently developed engineering strategies are generally successful in photoluminescence tuning but, unfortunately, suffer severe deterioration in emission intensity/efficiency and/or thermal stability. Herein, an efficient aliovalent substitution strategy toward reinforced structural rigidity is proposed and demonstrated experimentally. By incorporating Be2+ ion into the garnet-type Lu2SrAl4SiO12:Ce3+ phosphor, the phosphor shows enhanced internal/external quantum efficiency, from 79.2%/26.7% to 84.5%/32.9%, photoluminescence tuning from green (peaking at ∼512 nm) to yellow (peaking at ∼552 nm), and zero thermal quenching, even up to 200 °C. The Be2+ substitution at the Al2/Si2 site enables stable and rigid local surroundings around the Ce3+ activator, which is responsible for the unprecedented performance. In addition, high-quality warm WLED devices with a luminous efficiency of 158.1 lm W-1, correlated color temperature of 3858 K and high color rendering index of 81.7, are obtained by combining Lu2SrAl4SiO12:Ce3+,Be2+ as the yellow emitter, CaAlSiN3:Eu2+ as the red emitter and a blue-emitting InGaN chip. These findings highlight a new strategy for performance optimization of LED phosphors by selecting rigid covalent compounds with further reinforced structural rigidity via aliovalent substitution.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Шабанов, Александр Васильевич, Коршунов, Михаил Анатольевич, Буханов, Евгений Романович
Заглавие : Особенности усиления электромагнитного поля и увеличение плотности фотонных состояний в растительных фотонно-кристаллических структурах
Место публикации : Комп. оптика. - 2019. - Т. 43, № 2. - С. 231-237. - ISSN 0134-2452, DOI 10.18287/2412-6179-2019-43-2-231-237; Comput. Opt. - ISSN 2412-6179(eISSN)
Примечания : Библиогр.: 29
Предметные рубрики: BLUE IRIDESCENCE
LIGHT
COLOR
PULSE
BAND
Аннотация: Проведены расчёты с использованием метода трансфер матриц одномерных фотонных кристаллов с низким контрастом и разнопериодными асимметричными структурами. Такие структуры были найдены во многих растениях. При состыковке двух последовательно соединённых подрешёток с разными периодами отмечается увеличение амплитуды электромагнитного поля и плотности фотонных состояний внутри структуры и их изменение в зависимости от асимметрии толщин подрешёток.Calculations were performed using the transfer matrix of one-dimensional photonic crystals with low contrast and asymmetric structures of different periods. Such structures have been found in many plants. When joining two successively connected sublattices with different periods, an increase is observed in the amplitude of the electromagnetic field and the density of photon states inside the structure, and their change depends on the asymmetry of the thickness of the sublattices.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Deng J., Zhang H., Zhang X., Molokeev M. S., Qiu J., Liu Y., Lei B., Ma L., Wang X.
Заглавие : Enhanced luminescence performance of CaO:Ce3+,Li+,F- phosphor and its phosphor-in-glass based high-power warm LED properties
Место публикации : J. Mater. Chem. C. - 2018. - Vol. 6, Is. 15. - P.4077-4086. - ISSN 20507534 (ISSN), DOI 10.1039/c8tc00813b
Примечания : Cited References: 44. - The present study was supported by the National Natural Science Foundation of China (Grant No. 21671070), the Project for Construction of High-level University in Guangdong Province, the Teamwork Projects funded by the Guangdong Natural Science Foundation (Grant No. S2013030012842), the Guangzhou Science & Technology Project (No. 201704030086) and the Open Project Fund from Key Laboratory of Advanced of Materials of Yunnan Province (No. 2018KF01).
Ключевые слова (''Своб.индексиров.''): correlated color temperature--critical concentration--doping concentration--enhanced luminescence--high color rendering index--high power white led--high temperature solid-state reaction--thermal and chemical stabilities
Аннотация: To obtain white light-emitted diodes (wLEDs) with a low correlated color temperature (CCT) and a high color rendering index (CRI), red-emission is indispensable in their emission spectra. Herein, CaO:Ce3+,Li+,F- yellow phosphors with more red spectral component have been prepared via a high temperature solid-state reaction. As compared to the F- undoped samples, CaO:Ce3+,Li+,F- phosphor have lower critical doping concentration of Ce3+ and show stronger luminescence. At the critical concentration, a quantum efficiency of 66.4% and enhanced thermal and chemical stability were obtained in CaO:Ce3+,Li+,F-. Furthermore, a CaO:Ce3+,Li+,F--based phosphor-in-glass (PiG) using the red-emitting glass system with the composition of SiO2-Na2CO3-Al2O3-CaO:Eu3+ as the host material was constructed and used for high-power white LED applications. Such PiG samples with different phosphor doping concentrations can satisfy various light color demands and display higher reliability than the CaO:Ce3+,Li+,F- phosphor. An optimal PiG-based wLED exhibits color coordinates of (0.3769, 0.3386), a CCT of 3774 K, a CRI of 82.5 and a LE of 73.1 when the mass ratio of phosphor to glass matrix was 7:50 in PiG. Moreover, such PiG-based wLED also showed acceptable color stability under different drive currents. All the above results demonstrate that CaO:Ce3+,Li+,F- can be expected to be a potential alternative yellow phosphor for blue light excited PiG based warm wLEDs, particularly for high-power devices.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liao, Hongxu, Zhao, Ming, Molokeev M. S., Liu, Quanlin, Xia, Zhiguo
Заглавие : Learning from a mineral structure toward an ultra-narrow-band blue-emitting silicate phosphor RbNa3(Li3SiO4)4:Eu2+
Место публикации : Angew. Chem. - Int. Edit. - 2018. - Vol. 57, Is. 36. - P.11728-11731. - ISSN 1433-7851, DOI 10.1002/anie.201807087. - ISSN 1521-3773(eISSN)
Примечания : Cited References: 22. - This work was supported by the National Natural Science Foundations of China (Grant Nos. 51722202, 91622125 and 51572023), and Natural Science Foundations of Beijing (2172036), and M.S.M. acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Предметные рубрики: RED PHOSPHORS
COLOR-GAMUT
LUMINESCENCE
Ключевые слова (''Своб.индексиров.''): luminescence--minerals--phosphors--rigid structure--silicates
Аннотация: Learning from natural mineral structures is an efficient way to develop potential host lattices for applications in phosphor converted (pc)LEDs. A narrow‐band blue‐emitting silicate phosphor, RbNa3(Li3SiO4)4:Eu2+ (RNLSO:Eu2+), was derived from the UCr4C4‐type mineral model. The broad excitation spectrum (320–440 nm) indicates this phosphor can be well matched with the near ultraviolet (n‐UV) LED chip. Owing to the UCr4C4‐type highly condensed and rigid framework, RNLSO:Eu2+ exhibits an extremely small Stokes shift and an unprecedented ultra‐narrow (full‐width at half‐maximum, FWHM=22.4 nm) blue emission band (λem=471 nm) as well as excellent thermal stability (96 %@150 °C of the initial integrated intensity at 25 °C). The color gamut of the as‐fabricated (pc)LEDs is 75 % NTSC for the application in liquid crystal displays from the prototype design of an n‐UV LED chip and the narrow‐band RNLSO:Eu2+ (blue), β‐SiAlON:Eu2+ (green), and K2SiF6:Mn4+ (red) components as RGB emitters.
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhao, Ming, Liao, Hongxu, Molokeev M. S., Zhou, Yayun, Zhang, Qinyuan, Liu, Quanlin, Xia, Zhiguo
Заглавие : Emerging ultra-narrow-band cyan-emitting phosphor for white LEDs with enhanced color rendition
Место публикации : Light: Sci. Appl. - 2019. - Vol. 8. - Ст.38. - ISSN 2047-7538, DOI 10.1038/s41377-019-0148-8
Примечания : Cited References: 31. - The present work was supported by the National Natural Science Foundations of China (Grant Nos. 51722202, 51572023 and 91622125), Natural Science Foundations of Beijing (2172036), Fundamental Research Funds for the Central Universities (FRF-TP-18-002C1), and the Guangdong Provincial Science & Technology Project (No. 2018A050506004). M.S.M. is grateful for the support from the Russian Foundation for Basic Research (Grant No. 17-52-53031).
Предметные рубрики: LUMINESCENCE PROPERTIES
TEMPERATURE
ROUTE
Аннотация: Phosphor-converted white LEDs rely on combining a blue-emitting InGaN chip with yellow and red-emitting luminescent materials. The discovery of cyan-emitting (470–500 nm) phosphors is a challenge to compensate for the spectral gap and produce full-spectrum white light. Na0.5K0.5Li3SiO4:Eu2+ (NKLSO:Eu2+) phosphor was developed with impressive properties, providing cyan emission at 486 nm with a narrow full width at half maximum (FWHM) of only 20.7 nm, and good thermal stability with an integrated emission loss of only 7% at 150 °C. The ultra-narrow-band cyan emission results from the high-symmetry cation sites, leading to almost ideal cubic coordination for UCr4C4-type compounds. NKLSO:Eu2+ phosphor allows the valley between the blue and yellow emission peaks in the white LED device to be filled, and the color-rendering index can be enhanced from 86 to 95.2, suggesting great applications in full-spectrum white LEDs.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Huang J., Su B., Song E., Molokeev M. S., Xia Z.
Заглавие : Ultra-broad-band-excitable Cu(I)-based organometallic halide with near-unity emission for light-emitting diode applications
Место публикации : Chem. Mater. - 2021. - Vol. 33, Is. 12. - P.4382-4389. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.1c00085
Примечания : Cited References: 43. - This research was supported by the National Natural Science Foundation of China (Grant Nos. 51961145101 and 51972118), the Fundamental Research Funds for the Central Universities (D2190980), the Guangzhou Science and Technology Project (202007020005), International Cooperation Project of National Key Research and Development Program of China (2021YFE0105700), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01X137). The reported study was also funded by RFBR according to research project no. 19-52-80003
Аннотация: Low-dimensional hybrid metal halides demonstrate broad-band emission and high photoluminescence quantum yield (PLQY) acting as excellent candidates for a new generation of luminescent materials in lighting fields. However, most luminescent metal halides can only be excited by ultraviolet radiation, and the discovery of high-efficient emitters with broad-band excitation characteristics, especially upon efficient blue light irradiation, is a challenge. Herein, a zero-dimensional (0D) Cu(I)-based organometallic halide (18-crown-6)2Na2(H2O)3Cu4I6 (CNCI) was prepared with a green emission band centered at 536 nm and a near-unity PLQY (91.8%) upon excitation of 450 nm. Importantly, the ultrabroad excitation band covering a 300-500 nm range was observed in CNCI, and the luminescence mechanism has been discussed in detail. A white light-emitting diode (WLED) was fabricated with high luminous efficiency of 156 lm/W and a high color rendering index of 89.6. This work provides guidance for designing high-performance luminescent metal halides with suitable excitation characteristics and also promotes the application prospects of such materials in WLED fields.
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9.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Gunyakov V. A., Zhuikov V. A., Zyryanov V. Ya., Smorgon S. L., Shabanov V. F.
Заглавие : Two-color display based on polymer dispersed liquid crystals films
Коллективы : Summer European Liquid Crystals conference
Место публикации : First Summer European Liquid Crystal Conference: abstracts. - Vilnius, 1991. - Vol. 1. - P.90
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wu, Yanzheng, Li, Weiqiang, Zheng, Yifan, Xu, Yiqin, Wen, Dawei, Molokeev M. S., Pan, Zaifa
Заглавие : Apatite oxynitride phosphor (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+: A single-phased host with solar-like and efficient emission
Место публикации : J. Am. Ceram. Soc. - 2023. - Vol. 106, Is. 5. - P.2985-2996. - ISSN 00027820 (ISSN), DOI 10.1111/jace.18981. - ISSN 15512916 (eISSN)
Примечания : Cited References: 35. - This work was supported by the National Natural Science Foundation of China (Project No. 10804099, 21804119), Key projects of Zhejiang Natural Science Foundation (Project No. LZ18B050002), GDAS’ Project of Science and Technology Development (Nos. 2021GDASYL-20210103069, 2021GDASYL-20210103071)
Аннотация: During pursuing high color rendering index for full-color-emitting phosphor, low quantum efficiency (QE) is usually accompanying. We intend to elevate the luminescence efficiency when realizing a solar-like spectra distribution, by constructing apatite structure oxynitride, inheriting high covalence and rigidity from oxynitride, and suitable multiple cation sites from oxyapatite compounds. Full-color-emitting apatite structure oxynitride phosphor (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+ has been prepared, and the crystal sites’ occupancies of activators in this host were favorable for white emission. (Mg,Y)5Si3(O,N)13:Ce3+,Mn2+ phosphor shows whole visible light with emission wavelength ranging from 370 to 750 nm, matching the spectra of sunlight quite well. The fabricated white light-emitting diode lamp demonstrated the distinctive overall performance of QE and chromaticity properties (Ra and R9). Furthermore, correlated color temperature is tunable from cool nature to warm white. The obtained lamp possesses the feature of less blue light hazard and high saturation of red degree, compared with the commercial YAG-based lamp.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wang, Xuejiao, Feng, Xiaowen, Molokeev M. S., Zheng, Huiling, Wang, Qiushi, Xu, Chunyan, Li, Ji-Guang
Заглавие : Modulation of Bi3+ luminescence from broadband green to broadband deep red in Lu2WO6 by Gd3+ doping and its applications in high color rendering index white LED and near-infrared LED
Место публикации : Dalton Trans. - 2023. - Vol. 52, Is. 9. - P.2619-2630. - ISSN 14779226 (ISSN), DOI 10.1039/D2DT03751C. - ISSN 14779234 (eISSN)
Примечания : Cited References: 4. - This work is supported in part by the Project of Education Department of Liaoning Province (Grant No. LQ2019014) and he Natural Science Foundation of Liaoning Province (Grant No. 2020-MS-286). The authors are thankful for the support for the 4B9A Beamline from the Beijing Synchrotron Radiation Facility (BSRF) (Project No. 2021-BEPC-PT-005290). The authors would like to thank Siqi Liu from Shiyanjia Lab (
Аннотация: Phosphors that exhibit tunable broadband emissions are highly desired in multi-functional LEDs, including pc-WLEDs and pc-NIR LEDs. In this work, broadband emissions were obtained and modulated in the unexpectedly wide spectral range of 517–609 nm for (Lu0.99−xGdxBi0.01)2WO6 phosphors by tuning the Gd3+ content (x = 0–0.99). The effects of Gd3+ doping on phase constituents, particle morphology, crystal structure, and photoluminescence were systematically investigated. Broadband green emission was obtained from Gd3+-free (Lu0.99Bi0.01)2WO6 phosphors (x = 0), whose emission intensity was enhanced by 50% with 5 at% Gd3+ (x = 0.05). The phase transition happened when x 0.50 and the broadband red-NIR emission was obtained when x = 0.75–0.99. Three luminescence centers were proved to be responsible for the broadband green emissions via crystal structure, spectral fitting and fluorescence decay analysis. A pc-WLED with a high color rendering index (Ra = 91.3), a stable emission color, and a low color temperature (3951 K) was fabricated from the (Lu0.94Gd0.05Bi0.01)2WO6 broadband green phosphor, and an LED device that simultaneously emits high color rendering index white light and NIR light was obtained with the (Gd0.99Bi0.01)2WO6 broadband red-NIR phosphor. Night vision and noninvasive imaging were also demonstrated using the latter LED device.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen J., Zou X., Li W., Zhang H., Zhang X., Molokeev M. S., Liu Y., Lei B.
Заглавие : Strategy to construct high thermal-stability narrow-band green-emitting Si-CDs@MAs phosphor for wide-color-gamut backlight displays
Место публикации : Adv. Opt. Mater. - 2022. - Vol. 10, Is. 21. - Ст.2200851. - ISSN 21951071 (ISSN), DOI 10.1002/adom.202200851
Примечания : Cited References: 47. - The work was supported by the Ministry of Science and Technology of China (No. G2021030022L), the Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams (No. 2021KJ122), the National Natural Science Foundations of China (No. 52102042), the Independent Research and Development Projects of Maoming Laboratory (No. 2021ZZ004), the Key Realm R&D Program of Guangdong Province (No. 2021B0707010003), the Guangzhou Science & Technology Project (Nos. 202007020005 and 202103000059), the Guangdong Provincial Science and Technology Project (Nos. 2021A0505050006 and 2022A1515010229), and the Project of GDUPS (2018) for B.L.
Аннотация: Developing innovative narrow-band green-emitting phosphors featuring low thermal quenching and eco-friendliness for white light-emitting diode (WLED) backlights is a pivotal challenge. Benefitting from narrowband and low toxicity of green-emitting silanized carbon dots (Si-CDs), an efficient confinement and protection strategy through embedding Si-CDs in mesoporous aluminas (MAs) is proposed to construct MAs and Si-CDs composites (Si-CDs@MAs) with superior luminescence properties. Si-CDs@MAs phosphor exhibits green emission at 526 nm with narrow full width at half maximum of 51 nm, zero-thermal quenching even up to 423 K (104.1%@423 K of the emission peak intensity at 298 K), and the internal quantum efficiency of 64.46%. Compared with broad-band yellow-emitting solid-state Si-CDs (S-Si-CDs), the thermal stability, photostability, and water stability of Si-CDs@MAs phosphor are remarkably improved due to surface protection. The WLED backlight is fabricated with optimized Si-CDs@MAs phosphor, which shows high luminous efficacy of 117.43 lm W?1 and wide color gamut (107% NTSC). Furthermore, this work provides the design principles of realizing stable narrow-band solid-state fluorescence carbon dots, suggesting its great potential for wide-color-gamut display application.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhang, Qiuhong, Li, Junhao, Jiang, Wei, Lin, Litian, Ding, Jianhong, Brik, Mikhail G., Molokeev M. S., Ni, Haiyong, Wu, Mingmei
Заглавие : CaY2Al4SiO12:Ce3+,Mn2+: a single component phosphor to produce high color rendering index WLEDs with a blue chip
Место публикации : J. Mater. Chem. C. - 2021. - Vol. 9, Is. 34. - P.11292-11298. - ISSN 2050-7526, DOI 10.1039/d1tc01770e. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 35. - This work has been financially supported by the National Nature Science Foundation of China (51902063, 51902354, U1801253), the Science and Technology Project of Guangdong Province (2018A050506061), the Science and Technology Project of Guangzhou City (202007020005, 202007020008) and GDAS' Project of Science and Technology Development (2020GDASYL-20200302010, 2018GDASCX-0110). M. G. Brik also thanks the support from the Chongqing Recruitment Program for 100 Overseas Innovative Talents (Grant No. 2015013), the Program for the Foreign Experts (Grant No. W2017011) and Wenfeng High-End Talents Project (Grant No. W2016-01) offered by Chongqing University of Posts and Telecommunications (CQUPT), Estonian Research Council grant PUT PRG111, European Regional Development Fund (TK141) and NCN project 2018/31/B/ST4/00924
Предметные рубрики: GARNET PHOSPHOR
ENERGY-TRANSFER
RED EMISSION
LUMINESCENCE PROPERTIES
Аннотация: A high color rendering index white light emitting diode (WLED) is generally produced by combining yellow and red mixed phosphors on a blue chip. Herein we report a single component phosphor based on CaY2Al4SiO12 (CYAS) to achieve warm white light emission with a high color rendering index (Ra), which can be up to 90.5. Ce3+, Mn2+ singly doped and co-doped CYAS phosphors have been synthesized by solid state reactions, respectively, for comparative investigations. The Rietveld X-ray diffraction (XRD) refinements show that the CYAS host crystallizes in a cubic structure with the Ia[3 with combining macron]d space group. The valence states of Ce and Mn inside the CYAS host have been confirmed by XPS and EPR. Ce3+ occupies the Ca2+/Y3+ site and generates a yellow emission band around 543 nm from its characteristic 5d–4f transition. Mn2+ occupies both the dodecahedron Ca2+/Y3+ and octahedral Al3+ sites, emitting red and deep red lights at 616 nm and 750 nm, respectively. These two emission bands are attributed to the 4T1(4G)–6A1(6S) transitions of Mn2+. Upon 460 nm light excitation, both the Ce3+ and Mn2+ characteristic emissions can be obtained, in which the emissions of Mn2+ result from the occurrence of energy transfer from Ce3+ in CYAS. All the results indicate that the prepared CYAS:Ce3+,Mn2+ could be a promising single component phosphor for blue chip WLEDs.
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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) : 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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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen M., Xia Z., Molokeev M. S., Lin C. C., Su C., Chuang Y. -C., Liu Q.
Заглавие : Probing Eu2+ luminescence from different crystallographic sites in Ca10M(PO4)7:Eu2+ (M = Li, Na, and K) with β-Ca3(PO4)2-type structure
Место публикации : Chem. Mater.: American Chemical Society, 2017. - Vol. 29, Is. 17. - P.7563-7570. - ISSN 08974756 (ISSN), DOI 10.1021/acs.chemmater.7b02724
Примечания : Cited References: 34. - The present work was supported by the National Natural Science Foundation of China (Grants 51722202, 91622125, and 51572023), Natural Science Foundations of Beijing (2172036), and Fundamental Research Funds for the Central Universities (FRF-TP-16-002A3). C.C.L. and C.C.S. acknowledge the financial support from the Ministry of Science and Technology of Taiwan (Contract No. MOST 104-2113-M-027-007-MY3), and M. Molokeev acknowledges support of the Russian Foundation for Basic Research (17-52-53031).
Ключевые слова (''Своб.индексиров.''): calcium--doping (additives)--excited states--light emission--lithium--luminescence--phosphors--photoluminescence--positive ions--rietveld refinement--single crystals--color tuning--crystallographic sites--different distributions--emission bands--local environments--long wavelength bands--luminescent centers--power diffraction data--europium
Аннотация: Eu2+ local environments in various crystallographic sites enable the different distributions of the emission and excitation energies and then realize the photoluminescence tuning of the Eu2+ doped solid state phosphors. Herein we report the Eu2+-doped Ca10M(PO4)7 (M = Li, Na, and K) phosphors with β-Ca3(PO4)2-type structure, in which there are five cation crystallographic sites, and the phosphors show a color tuning from bluish-violet to blue and yellow with the variation of M ions. The difference in decay rate monitored at selected wavelengths is related to multiple luminescent centers in Ca10M(PO4)7:Eu2+, and the occupied rates of Eu2+ in Ca(1), Ca(2), Ca(3), Na(4), and Ca(5) sites from Rietveld refinements using synchrotron power diffraction data confirm that Eu2+ enters into four cation sites except for Ca(5). Since the average bond lengths d(Ca-O) remain invariable in the Ca10M(PO4)7:Eu2+, the drastic changes of bond lengths d(M-O) and Eu2+ emission depending on the variation from Li to Na and K can provide insight into the distribution of Eu2+ ions. It is found that the emission band at 410 nm is ascribed to the occupation of Eu2+ in the Ca(1), Ca(2), and Ca(3) sites with similar local environments, while the long-wavelength band (466 or 511 nm) is attributed to Eu2+ at the M(4) site (M = Na and K). We show that the crystal-site engineering approach discussed herein can be applied to probe the luminescence of the dopants and provide a new method for photoluminescence tuning.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Miao, Shihai, Xia, Zhiguo, Molokeev M. S., Chen, Mingyue, Zhang, Jie, Liu, Quanlin
Заглавие : Effect of Al/Si substitution on the structure and luminescence properties of CaSrSiO4:Ce3+ phosphors: analysis based on the polyhedra distortion
Место публикации : J. Mater. Chem. C: Royal Society of Chemistry, 2015. - Vol. 3, Is. 18. - P.4616-4622. - ISSN 2050, DOI 10.1039/c5tc00339c. - ISSN 20507534(eISSN)
Примечания : Cited References:30. - The present work was supported by the National Natural Science Foundations of China (Grant No. 51002146, 51272242), Natural Science Foundations of Beijing (2132050), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), Beijing Nova Program (Z131103000413047), Beijing Youth Excellent Talent Program (YETP0635), the Funds of the State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University (KF201306) and the excellent tutor section of the Fundamental Research Funds for the Central Universities of China University of Geosciences, Beijing (2652015027).Cover image: Artwork representing main idea of this article
Предметные рубрики: LIGHT-EMITTING-DIODES
COLOR-TUNABLE PHOSPHOR
ENERGY-TRANSFER
Аннотация: Blue-emitting CaSrSiO4:Ce3+,Li+ phosphors were prepared by a high temperature solid-state method, and the effect of substituting Al3+ for Si4+ in CaSrSiO4:Ce3+,Li+ has been studied. Crystal structures of the as-prepared Ca1−ySr1−ySi1−xAlxO4:yCe3+,yLi+ phosphors were resolved by the Rietveld method, which suggested that all the samples belonged to the orthorhombic symmetry (Pnma) group of α-CaSrSiO4. The photoluminescence (PL) emission and excitation spectra, the lifetime, and the effect of Al3+ concentration on the PL properties were investigated in detail. The emission peaks of the CaSrSi1−xAlxO4:Ce3+,Li+ (x = 0–0.10) phosphors were red-shifted from 452 to 472 nm with increasing Al/Si ratio. The red-shift of the Ce3+ emission is ascribed to the polyhedra distortion of the cations, originating from the variation in the neighboring [(Si,Al)O4] polyhedra, and the detailed mechanism has been discussed.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Guo Q., Liao L., Molokeev M. S., Mei L., Liu H.
Заглавие : Color tunable emission and energy transfer of Ce3+ and Tb3+ co-doped novel La6Sr4(SiO4)6F2 phosphors with apatite structure
Место публикации : Mater. Res. Bull.: Elsevier, 2015. - Vol. 72. - P.245-251. - ISSN 0025-5408, DOI 10.1016/j.materresbull.2015.07.029
Примечания : Cited References: 37. - This present work is supported by the National Natural Science Foundations of China (Grant No. 41172053).
Предметные рубрики: LIGHT-EMITTING-DIODES
LUMINESCENCE PROPERTIES
PHOTOLUMINESCENCE PROPERTIES
EU2+
LEDS
Ключевые слова (''Своб.индексиров.''): inorganic compounds--luminescence--phosphors--optical properties--crystal structure
Аннотация: Single-phase La6Sr4(SiO4)6F2: Ce3+, Tb3+ samples with apatite-like structure have been synthesized via solid-state reaction method. The phase structure, luminescence properties, lifetime, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples. Effective energy transfer occurs from Ce3+ to Tb3+ in La6Sr4(SiO4)6F2, which shows more intense Blue-Green light under UV light excitation. In addition, a possible mechanism of the energy-transfer from Ce3+ to Tb3+ ion is also proposed. The critical distance RC of Ce3+ to Tb3+ ions in La6Sr4(SiO4)6F2 host was calculated to be 11.878 Å. All the results indicate that La6Sr4(SiO4)6F2:Ce3+, Tb3+ phosphors have potential applications to be used as near UV-convertible phosphors for white light-emitting diodes. © 2015 Elsevier Ltd. All rights reserved.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pustovarov V. A., Ogorodnikov I. N., Omelkov S. I., Molokeev M. S., Kozlov A. V., Isaenko L. I.
Заглавие : Photoluminescence of monoclinic Li3AlF6 crystals under vacuum ultraviolet and soft X-ray excitations
Место публикации : Opt. Mater.: Elsevier, 2015. - Vol. 49. - P.201-207. - ISSN 0925-3467, DOI 10.1016/j.optmat.2015.09.011
Примечания : Cited References: 49. - This work was partly supported by the Ministry of Education and Science of the Russian Federation (the basic part of the government mandate); Center of Excellence "Radiation and Nuclear Technologies" (Competitiveness Enhancement Program of Ural Federal University, Russia), HASYLAB DESY (Projects Nos. 20110843, 20080119EC), European Social Fund ("Mobilitas" program, MJD219), Estonian Research Council (Institutional Research Funding IUT02-26) and Baltic Science Link project coordinated by the Swedish Research Council, VR
Предметные рубрики: LiBaAlF6 single-crystals
F-type centers
LiBaF3 crystals
Color-centers
Recombination luminescence
Rietveld refinement
VUV spectroscopy
Trapped excitons
Energy-transfer
Pure
Ключевые слова (''Своб.индексиров.''): li3alf6--time-resolved luminescence--vuv spectroscopy--defects
Аннотация: Using Bridgman technique we have grown monoclinic β-LiAF crystals suitable for optical studies, performed XRD-identification and Rietveld refinement of the crystal structure and carried out a photoluminescence study upon vacuum ultraviolet (VUV) and extreme ultraviolet (XUV)-excitations, using the low-temperature (T = 7.2 K) time-resolved VUV-spectroscopy technique. The intrinsic PL emission band at 340–350 nm has been identified as due to radiative recombination of self-trapped excitons. The electronic structure parameters were determined: bandgap E g ≈ 12.5 eV, energy threshold for creation of unrelaxed excitons 11.8 eV < E n < 12.5 eV . The PL emission bands at 320–325 and 450 nm were attributed to luminescence caused by lattice defects. We have discovered an efficient excitation of PL emission bands in the energy range of interband transitions ( E ex > 13.5 eV), as well as in the energy range of core transitions at 130 eV. We have revealed UV–VUV PL emission bands at 170 and 208 nm due to defects. A reasonable assumptions about the origin of the UV–VUV bands were discussed.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Liu C., Xia, Zhiguo, Chen M., Molokeev M. S., Liu Q.
Заглавие : Near-infrared luminescence and color tunable chromophores based on Cr3+-Doped Mullite-Type Bi2(Ga,Al)4O9 solid solutions
Место публикации : Inorg. Chem.: American Chemical Society, 2015. - Vol. 54, Is. 4. - P.1876-1882. - ISSN 0020-1669, DOI 10.1021/ic502779d
Примечания : Cited References: 26. - The present work was supported by the National Natural Science Foundations of China (Grants 51002146, 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), Beijing Youth Excellent Talent Program (YETP0635), 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: PERSISTENT LUMINESCENCE
PHOSPHORS
PIGMENT
GARNET
OXIDES
FIELD
RED
Аннотация: Cr3+-activated mullite-type Bi2Ga(4-x)AlxO9 (x = 0, 1, 2, 3, and 4) solid solutions were prepared by the solid state reaction, and their spectroscopic properties were investigated in conjunction with the structural evolution. Under excitation at 610 nm, Bi2[Ga(4-y)Aly]3.97O9:0.03Cr3+ (y = 0, 1, 2, 3, and 4) phosphors exhibited broad-band near-infrared (NIR) emission peaking at ?710 nm in the range 650?850 nm, and the optimum Cr3+ concentrations and concentration quenching mechanism were determined. Except for the interesting NIR emission, the body color changed from white (at x = 0) to green (at x = 0.08) for Bi2Ga4?xO9:xCr3+, and from light yellow (at x = 0) to deep brown (at x = 0.08) for Bi2Al4?xO9:xCr3+, respectively. Moreover, as a result of variable Al/Ga ratio, the observed body color for Bi2[Ga(4-y)Aly]3.97O9:0.03Cr3+ (y = 0, 1, 2, 3, and 4) varied from deep brown to green. The relationship between the observed colors and their diffuse reflectance spectra were also studied for the understanding of the different absorption bands. The results indicated that Cr3+-doped Bi2Ga(4-x)AlxO9 solid solutions appeared as the bifunctional materials with NIR phosphors and color-tunable pigments.
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