Wide Excitation Band Research Articles

The role of co-dopant Ce3+ on the spectral properties of Dy3+ activated YAG single crystal for yellow green laser application

Ce3+ and Dy3+ co-doped Y3Al5O12 (abbr. as Ce, Dy: YAG) single crystal was grown by the Czochralski method. As compared with the absorption spectrum of Dy: YAG crystal, the synchronous doping of Ce3+ ions into Dy: YAG crystal resulted in a wide excitation band in the 425–500 nm region peaking around 447 nm owing to the 4f→5d transition of Ce3+ ions, and inhomogeneous broadening absorption with the full width at half maximum (FWHM) from 4 nm to 39 nm. Furthermore, due to the efficient energy transfer from Ce3+ to Dy3+ ions in YAG crystal, under 447 nm excitation Ce, Dy: YAG crystal showed intense and wide characteristic yellow green emission, whose intensity increased by 12.3 times and FWHM from 12 nm to 113 nm as compared with Dy: YAG crystal. The fluorescence lifetime of Dy3+: 4F9/2 level has increased from 693.1 μs to 2.062 ms. Based on the above results, Ce, Dy: YAG crystal would be an excellent candidate for the realization of yellow green waveband laser output.

Terbium(III) oxide as rare earth metal modifier in PbO/Bi2O3 sodium borate glasses for highly efficient optoelectronic devices: Synthesis, characterization, and applications

This paper explores the incorporation of Terbium(III) oxide as a rare earth metal modifier in sodium borate glasses containing PbO/Bi2O3, aiming to enhance the efficiency of optoelectronic devices. The synthesis and characterization of these glasses are detailed, highlighting the unique properties introduced by Terbium(III) oxide. The study investigates the regularities in the characteristics such as physical, XRD, UV, FTIR, and optical properties of 70B2O3–15Na2O – 15PbO – (5-x)Bi2O3 – xTb2O3, where x = 0; 1; 2; 3; 5 mol% prepared glassy samples, considering varying concentrations of bismuth and the modifier (e.g. Tb2O3), and examines their mutual impact on the borate glass matrix involved. It is found that there are sharp peaks on the diffraction pattern, which increase in width and intensity with increasing Terbium concentration from 3 to 5 mol% in the glass matrices, e.g. two-phase structures, amorphous and crystalline, are observed. Moreover, a wide excitation band in the glass matrix is also observed in the region of 200–320 nm. The study delves into the potential applications of these modified glasses in highly efficient optoelectronic devices, contributing valuable insights to the advancement of materials for technological applications.

Red Fluorescent Eu(TTA)3BIP Complex and Its Application in Blue Light‐Reducing Film

AbstractIn this work, a Eu(TTA)3BIP complex with a novel structure was synthesized and characterized. The Eu(TTA)3BIP complex has a wide excitation band and can be excited by light in the ultraviolet and blue regions. The characteristic red light of Eu(III) is emitted when the complex is excited. The use of the 2‐(Pyrimidin‐2‐yl)‐1H‐benzo[d]imidazole (BIP) ligand improved the UV resistance of the complex. Moreover, the blue light reducing film prepared by the Eu(TTA)3BIP complex can effectively weaken blue light irradiation. In addition, the Eu(TTA)3BIP complex exhibits fluorescence thermal quenching properties. This provides the possibility for temperature sensing.

Low temperature synthesis and enhancement of blue emitting CaMgSi2O6:Eu2+ phosphor by co-doping

Near UV excitable blue emitting Eu2+ activated CaMgSi2O6 phosphor has been synthesized by urea assisted pyrolysis technique. The effects of flux (H3BO3, NH4F, NH4Br, NH4Cl, CaF2, BaF2), sintering temperature (700–1100 °C), activator concentrations and co-dopants (Zn2+, Y3+, Al3+ and Gd3+) on the photoluminescence properties of CaMgSi2O6:Eu2+ were studied systematically. Zn2+, Y3+, Al3+ and Gd3+ co-doped CaMgSi2O6:Eu2+ phosphors improved the PL intensity and also exhibited a wide excitation band in the region of 250–420 nm, and emission at 447 nm found suitable for nUV based white LED applications. The PL emission intensity of Y3+ co-doped CaMgSi2O6:Eu2+ is comparable to that of the commercial BaMgAl1O17:Eu2+ blue emitting phosphor. However, Y3+ co-doped CaMgSi2O6:Eu2+ showed a higher thermal quenching when compared with BaMgAl1O17:Eu2+. The crystalline phase formation and morphology of synthesized silicate phosphors were confirmed by powder XRD and SEM analysis.

Sol-Gel Synthesis and Photoluminescence Properties of a Far-Red Emitting Phosphor BaLaMgTaO6:Mn4+ for Plant Growth LEDs.

Far-red (FR) emitting LEDs are known as a promising supplement light source for photo-morphogenesis of plants, in which FR emitting phosphors are indispensable components. However, mostly reported FR emitting phosphors are suffering from problems of wavelength mismatch with LED chips or low quantum efficiency, which are still far from practical applications. Here, a new efficient FR emitting double-perovskite phosphor BaLaMgTaO6:Mn4+ (BLMT:Mn4+) has been prepared by sol-gel method. The crystal structure, morphology and photoluminescence properties have been investigated in detail. BLMT:Mn4+ phosphor has two strong and wide excitation bands in the range of 250-600 nm, which matches well with a near-UV or blue chip. Under 365 nm or 460 nm excitation, BLMT:Mn4+ emits an intense FR light ranging from 650 to 780 nm with maximum emission at 704 nm due to 2Eg → 4A2g forbidden transition of Mn4+ ion. The critical quenching concentration of Mn4+ in BLMT is 0.6 mol%, and its corresponding internal quantum efficiency is as high as 61%. Moreover, BLMT:Mn4+ phosphor has good thermal stability, with emission intensity at 423 K keeping 40% of the room temperature value. The LED devices fabricated with BLMT:Mn4+ sample exhibit bright FR emission, which greatly overlaps with the absorption curve of FR absorbing phytochrome, indicating that BLMT:Mn4+ is a promising FR emitting phosphor for plant growth LEDs.

A high absorption efficiency blue-emitting phosphor NaSrScSi2O7:Eu2+ for near-UV-pumped white light-emitting diodes

The Eu2+ ion is extensively used as an activator due to its wide excitation band and high efficiency emission spectrum. However, most Eu2+-activated blue-emitting phosphors have low absorption efficiency in the near-ultraviolet (n-UV) region or lack the short-wavelength blue light emission (<450 nm), resulting in UV light leakage or poor color rendering. Herein, we have successfully prepared a brand-new blue phosphor NaSrScSi2O7: Eu2+ by solid-state reaction method. The Rietveld refinement of the powder diffraction data, luminescent properties, decay lifetime, quantum efficiencyand thermal quenching have been investigated in detail. Under 345 nm excitation, the NaSrScSi2O7: 0.03Eu2+phosphor manifests an asymmetric emission spectrum centered at 427 nm, and notably, shows a high absorption efficiency of 84.35%. Finally, we encapsulated two white light-emitting diodes (WLEDs) devices using as-prepared blue-emitting phosphor and three commercial phosphors. At 80 mA drive current, both packaged devices demonstrate warm white light. Meanwhile, the WLED-2 with NaSrScSi2O7: 0.03Eu2+ blue-emitting phosphor has a lower correlated color temperature of 3726 K, its spectrum complements more short-wavelength spectrum, and the special color rendering index R6 and R7 increased from 95.2, 94.5 to 98.3, 96.5, respectively, compared with WLED-1 without present phosphor. These results demonstrate that NaSrScSi2O7: Eu2+ blue-emitting phosphor is a prospective novel luminescent material for WLEDs.

In vitro irradiation of doxorubicin with 18F-FDG Cerenkov radiation and its potential application as a theragnostic system.

Doxorubicin (DOX), an effective chemotherapeutic agent, has a wide excitation band centred at 480 nm. Cerenkov radiation (CR) is considered an internal light source in photodynamic therapy (PDT). DOX could be photoactivated by CR and thus, enhancing its cytotoxicity. In this work, 18F-FDG was used to evaluate the effect of Cerenkov radiation on DOX, in comparison to irradiation with a 450-nm laser beam, in terms of ROS production. The production of 1O2 and O2⁎- reactive species during DOX irradiation was detected indirectly by ABMA and DCPIP bleaching, respectively. The cytotoxic effect of the DOX / 18F-FDG CR system was evaluated in the T47D breast cancer cell line. The irradiation of DOX produced 1O2 and O2⁎- species using both 18F-FDG CR and a 450-nm laser beam. The majority reactive species produced in both cases was 1O2; a favourable result, given the greater cytotoxicity of this species. The viability of T47D cells in presence of DOX (5 nM), 18F-FDG (37.5 μCi) and DOX (5 nM)/18F-FDG (37.5 μCi) was (86 ± 9)%, (84 ± 8)% and (64 ± 5)%, respectively; these results suggest a synergistic cytotoxic effect derived from the cytotoxic activity of DOX and its photoactivation by 18F-FDG CR. It is worth noting that the system could be optimized in terms of DOX concentration and 18F-FDG activity for better results. Due to the fact that 18F-FDG is widely used in nuclear imaging, the DOX/18F-FDG system also possesses theragnostic characteristics. Thus, in this work, it is demonstrated that DOX can be used in a dual therapy system based on chemotherapy-PDT when 18F-FDG CR is used as a DOX excitation source.

Luminescence properties and energy transfer of Tb3+, Eu3+ co-doped YTaO4 phosphors obtained via sol-gel combustion process.

Tantalate is considered as a valuable and efficient luminescence host because of its intense absorption in the ultraviolet area and excellent chemical properties. In this work, a series of pure YTaO4:Eu3+ and/or Tb3+ crystals were prepared via a sol–gel combustion method. The morphology, structure, and optical properties of the samples were discussed in detail. The Eu3+, Tb3+ co-doped YTaO4 samples are consisted of small spherical particles of around 18 nm. The prepared YTaO4:Tb3+ and/or Eu3+ samples exhibit the characteristic wide excitation band around 210–300 nm, the characteristic narrow red emission of Eu3+ (5D0 → 7F2) transitions and green emission of the Tb3+ (5D4 → 7F5) transitions when excited by UV light. It is focused on the energy transfer processes from the YTaO4 to Tb3+ as well as Eu3+ ions and from Tb3+ to Eu3+ ions of YTaO4:Eu3+/Tb3+ phosphors. Color-tunable emissions are realized through adjusting the types of rare earth ion (Eu3+ and Tb3+) and relative doping concentrations excited by a single wavelength. That is to say, the obtained Tb3+ and Eu3+ co-doped YTaO4 phosphors have a promising prospect in lasers, white light diodes (WLED), fluorescent lamp, and field emission display devices, etc.

Спектрально-люминесцентные свойства тербийсодержащих циркономолибдатов

К настоящему времени всесторонне изучены двойные молибдаты одно- и четырёхвалентных элементов, достаточно полно исследованы системы с молибдатами одно- и трёхвалентных элементов. Некоторые материалы на основе двойных молибдатов, например, содержащие лантаниды, являются перспективными для лазерной техники и электроники. Между тем, сведения о свойствах, особенно оптических, у молибдатов, содержащих редкоземельные элементы и цирконий, ограничены. Целью данной работы являлось исследование люминесцентных свойств самоактивированных тербийсодержащих циркономолибдатов составов Tb2Zr3(MoO4)9 (1:3) и Tb2Zr(MoO4)5 (1:1),кристаллизующихся в двух разных структурных типах.Порошковые образцы исследуемых молибдатов синтезированы керамической технологией. В работе использованы методы измерения спектров поглощения, возбуждения и люминесценции с помощью спектрофотометра Perkin Elmer Lambda 950. Люминесценция возбуждалась ксеноновой лампой ДКСШ-250 мощностью 250 Вт через монохроматор МДР-2 и регистрировалась с помощью двойного монохроматора СДЛ-1 с решеткой 600 штрихов/мм. В работе исследованы оптические свойства новых циркономолибдатов, содержащих ионы Tb3+. В них обнаружена яркая люминесценция в зелёной области спектра, обусловленная переходами внутри 4f- оболочки редкоземельного иона Tb3+, возбуждающегося как в полосах, связанных с 4f–4f переходами, так и в полосе с переносом заряда.Идентифицированы наблюдаемые спектральные линии и полосы люминесценции и возбуждения.Показано, что положение широкой полосы возбуждения, связанное с переходами «с переносом заряда» от O2– в группах MoO4 2– через связи Mo–O к люминесцентным центрам (Tb3+), не зависит от структуры матрицы. Структура и интенсивность наблюдаемых спектральных линий, свидетельствующие о низкой симметрии кристаллического окружения Tb3+, коррелируют с данными структурного анализа. Полученные в работе результаты могут быть использованы при создании перспективных люминофоров в зеленой области спектра при ультрафиолетовомвозбуждении.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; ЛИТЕРАТУРА&#x0D; 1. Софич Д. О., Доржиева С. Г., Чимитова О. Д., Базаров Б. Г., Тушинова Ю. Л., Базарова Ж. Г., Шендрик Р. Ю. Гиперчувствительный переход 5D0−7F2 трехвалентного европия в двойных молибдатах.Изв. РАН, Сер. физич. 2019;83(3): 384–387. DOI: https://doi.org/10.1134/S03676765190302202. Sofi ch D., Tushinova Yu. L., Shendrik R., Bazarov B. G., Dorzhieva S. G., Chimitova O. D., BazarovaJ. G. Optical spectroscopy of molybdates with composition Ln2Zr3(MoO4)9 (Ln: Eu, Tb). Opt. Mater. 2018;81:71–77. DOI: https://doi.org/10.1016/j.optmat.2018.05.0283. Софич Д., Доржиева С. Г., Чимитова О. Д., Базаров Б. Г., Ю.Л. Тушинова Ю. Л., Базарова Ж. Г.,Шендрик Р. Ю. Люминесценция ионов Pr3+ и Nd3+ в двойных молибдатах. ФТТ. 2019;61(5): 943–945.DOI: https://doi.org/10.21883/FTT.2019.05.47598.35F4. Доржиева С. Г., Тушинова Ю. Л., Базаров Б. Г., Непомнящих А. И., Шендрик Р. Ю, Базарова Ж. Г.Люминесценция Ln-Zr-содержащих молибдатов. Изв. РАН. Сер. физич. 2015;79(2): 300–303.DOI: https://doi.org/10.7868/S03676765150200765. Baur F., Justel Th. New red-emitting phosphor La2Zr3(MoO4)9:Eu3+ and the infl uence of host absorptionon its luminescence effi ciency. Aust. J. Chem. 2015;68(11): 1727–1734. DOI: https://doi.org/10.1071/CH152686. Qi S., Huang Y., Cheng H., Seo H. J. Luminescence and application of red-emitting phosphors of Eu3+-activated R2Zr3(MoO4)9 (R = La, Sm, Gd). Electron. Mater. Lett. 2016;12(1): 171–177. DOI: https://doi.org/10.1007/s13391-015-5244-17. Базарова Ж. Г., Тушинова Ю. Л., Базаров Б. Г., Доржиева С. Г. Двойные молибдаты редкоземель-ных элементов и циркония. Изв. АН. Сер. химич. 2017;(4): 587–592. Режим доступа: https://elibrary.ru/item.asp?id=291126318. Клевцова Р. Ф., Солодовников С. Ф., Тушинова Ю. Л., Базаров Б. Г., Глинская Л. А., Базарова Ж. 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A perovskite-like LaSrGaO4:Mn2+, Nd3+, Yb3+ NIR luminescent material for fluorescent temperature sensor

A NIR phosphor of the Mn2+, Nd3+, Yb3+ ions doped perovskite-like host LaSrGaO4 is successfully synthesized by high temperature solid phase method, and the energy transfer process about them is analyzed in detail. By measuring the temperature spectra of different samples and calculating the temperature sensitivities, it is found that the temperature sensitivity can be improved by adding Mn2+ and Yb3+ into LaSrGaO4:Nd3+, and that the maximum absolute sensitivity can be 5.64321%/K and that the relative sensitivity can be maintained at 0.474%/K. This NIR luminescent material LaSrGaO4:Mn2+, Nd3+, Yb3+ can be used as the NIR fluorescent temperature sensor for biological detection. In addition, the wide excitation bands of Mn2+, Nd3+ in visible region match well with the solar spectrum (AM 1.5), and the wide emission bands of Nd3+, Yb3+ in near infrared 900–1100 nm region are located in the spectral response curve of c-Si solar cells, so NIR luminescent material LaSrGaO4:Mn2+, Nd3+, Yb3+ may have the potential application in the spectral converter of c-Si solar cells to improve the conversion efficiency.

Energy transfer from Mn4+ to Mn5+ and near infrared emission with wide excitation band in Ca14Zn6Ga10O35:Mn phosphors

Ca14Zn6Ga10-xO35:xMn(CZG:xMn) phosphors were synthesized by high temperature solid state reaction. High doping concentration as 30 mol% for Mn ions can be realized in the compounds due to the existence of the multiple valance of Mn ions. Both red emission from Mn4+ and near infrared (NIR) emission from Mn5+ were observed from CZG:xMn phosphors. The energy transfer from Mn4+ ions to Mn5+ ions was detected, which makes it possible for CZG:xMn phosphors to emit 1152 nm light under the excitation of the whole visible light region, especially under the commercial blue chips (450 nm). This means the CZG: xMn phosphors can be used in the manufacture of NIR sources with small size, simple structure and low cost. Because CZG:xMn can be excited by 600 ~ 700 nm and emits 1152 nm, the phosphors show the application in the real-time biochemical detection because of the excellent penetration capacity of biological tissue for 600 ~ 700 nm and 1152 nm light. With the aid of low-temperature PL spectra, it was found that two zero phonon lines and multiple vibration bands are responsible for the five compact emission band from 650 ~ 750 nm of Mn4+ ions. The results are helpful to comprehend the mechanism of the emission of Mn ions in CZG:xMn and promote the phosphors application.

A luminescent Eu coordination polymer with near-visible excitation for sensing and its homologues constructed from 1,4-benzenedicarboxylate and 1H-imidazo[4,5-f][1,10]-phenanthroline

Ln-CPs were constructed to achieve luminescent Eu-CP excited at a wide excitation band including the visible region for sensing.

Enhancement of red emission assigned to inversion defects in ZnAl2O4:Cr3+ hollow spheres

ZnAl2O4:Cr3+ hollow spheres composed of secondary nanoparticles with single spinel phase were fabricated using carbon templets. Monitoring the emission of 687 nm, two wide excitation bands attributed to the electrons of Cr3+ transiting from 4A2g (4F) → 4T1g (4F) and 4A2g (4F) → 4T2g (4F) were observed. The broad excitation band at about 397 nm was asymmetric and consisted of two peaks, indicating that there was a trigonal distortion existing in the lattices. The intensity of all emitting peaks revealed sharp increasing trend with the sintering temperature increase, and the intensity of emission at 698 nm assigned to inversion defects was more intense than that of emission at 687 nm assigned to octahedral Cr3+ ions in the undistorted spinel lattice. The samples with higher synthesized temperature revealed longer decay time, and the relative weightage of shorter decay time component decreased with the increase of sintering temperature, indicating that the surface defects decreased.

The synthesis and luminescent properties of bonded Eu(III) polymer phosphors for white light‐emitting diode

AbstractA coordination and copolymerization strategy was adopted to synthesize bonded Eu(III) polymer phosphor poly(MMA‐co‐Eu(BTZ)2(Phen)(UA)) (PM‐Eu for short) with methyl methacrylate (MMA) as polymer matrix and Eu‐complex monomer Eu (BTZ)2(Phen)(UA) using azodiisobutyronitrile as initiator. The copolymer PM‐Eu exhibits thermal stability up to 266°C. It also exhibits wide and strong excitation bands from 230 to 380 nm monitored at 612 nm, matching well with the 365 nm of ultraviolet (UV) chip. PM‐Eu displays Eu(III) characteristic peaks at 579, 591, 612, 650, and 700 nm under the excitation of 365 nm of UV light. Meanwhile, it has a fluorescence lifetime of 0.582 ms, and it has a higher quantum yield of 0.672. All the results prove that the polymer PM‐Eu can be applied as a red component for fabrication of near UV‐based white light‐emitting diode (LED).

Highly efficient and thermally stable CaMgLaSbO6:Mn4+ red phosphor for indoor plant growth

CaMgLaSbO6 (CMLS): Mn4+ far-red phosphors were successfully synthesized by high temperature solid state reaction. X-ray diffraction (XRD), photoluminescence excitation (PLE) spectra, photoluminescence emission (PL) spectra, ultraviolet-visible spectra, the relationship between emission intensity and temperature and internal quantum efficiency (IQE) were used to analyze the characteristics and optical properties of the samples. It was found that CMLS: Mn4+ phosphor has a strong wide excitation band in the range of 200–550 nm. There is a broad emission band centered at 695 nm between 600 and 760 nm. The optimum doping concentration of Mn4+ is approximately 0.6 mol%. In addition, the chromaticity coordinates of CMLS:Mn4+ appear in the far-red region. The concentration quenching mechanism is attributed to the dipole-quadrupole interaction of Mn4+ ions. Beside, CMLS: 0.006Mn4+ shows remarkable thermal stability (I423K/I298K = 67.1%). Importantly, the IQE of CMLS: 0.006 Mn4 + phosphor was as high as 46.5%. Finally, a 365 nm light emitting diode (LED) chip and CMLS: 0.006Mn4+ phosphor are used to fabricate the LED device. The above results manifested that CMLS:Mn4+ phosphors are expected to make a contribution to indoor plant cultivation.

Multiwavelength near infrared downshift and downconversion emission of Tm3+ in double perovskite Y2MgTiO6:Mn4+/Tm3+ phosphors via resonance energy transfer

Multiwavelength near infrared emission of Tm3+ in double perovskite Y2MgTiO6:Mn4+/Tm3+ (in brief YMT: Mn4+/Tm3+) phosphors is to easily achieve by resonance energy transfer and downshift (or downconversion) between rare earth ions and transition metal ions. In this study, we observe the multiwavelength near infrared emissions of Tm3+ in Mn4+-Tm3+ co-doped YMT phosphors synthesized by a high temperature solid-state reaction. During the resonance energy transfer from Mn4+ to Tm3+, the YMT:Mn4+/Tm3+ phosphor exhibits three wavelength near-infrared emission around 800, 1488 and 1800 nm originating in 3H4→3H6, 3H4→3F4 and 3F4→3H6 of Tm3+ with a wide excitation band extending from 250 to 550 nm. The cascade emission of two wavelengths (1488 and 1800 nm) is mainly contributed to downconversion of Tm3+ ions. Based on Dexter's theory, the energy transfer mechanism is mainly contributed to a dipole-dipole interaction between Mn4+ and Tm3+ ions, which is responsible for the largely enhanced multiwavelength near infrared emission of Tm3+. Multiwavelength near infrared emission of Tm3+ make them potential application in solid state lasers, bioimaging, Ge photovoltaic devices (band gap approximately 0.67 eV) and so on.

Luminescence properties of Y5Si3O12N:Ce3+/Tb3+ co-doped oxynitride phosphors

As possible alternative applying to trichromatic white LEDs, oxynitirde phosphors which are consist of a range of Y-Si-ON: single doped Ce3+ and Y-Si-ON: Ce3+\\Tb3+ co-doping were smoothly prepared with the use of typical solid state reaction route. Not only the purity of the resulting phosphors was raised, but also the intensity of emission was enhanced due to the introduction of Li2CO3 flux (5wt %). A strong wide excitation band is suitable for UV LED chips that is ranging from 200 nm to 400 nm having maximum peak around 358 nm has been noticed. In the Ce3+ mono-doped phosphor, we noted a strong blue emission whose peak is at 439 nm at this excitation wavelength and in the Y5Si3O12N:Ce3+/Tb3+ co-doped phosphors two different light bands were also noted: the blue band was at 439 nm when reached its peak due to the Ce3+ ion and because of the and a highly efficient green emission of having maximum peak around 549 nm as a result of Tb3+ ions transitions (5D4→7F5).

Highly efficient and thermally stable of a novel red phosphor Sr3NaSbO6:Mn4+ for indoor plant growth

Far red-emitting Mn4+-activated oxide phosphor based on the substitution of Mn4+ for Sb5+ in the lattice of Sr3NaSbO6 (SNSO) was prepared via solid state reaction process. The crystal structure of the host was carefully discussed and studied. The resultant phosphors were characterized by X-ray powder diffraction, fluorescence spectra, ultraviolet-visible diffuse reflectance spectra, temperature-dependent emission spectra (298–548 K), luminescence decay curves and electroluminescence spectra. Excitation and emission spectra indicated that the sample had a wide excitation band in UV(250–400 nm) and exhibited the strong emission band centered at 695 nm. The band structure for SNSO was calculated based on the density functional theory, and the bandgap value of SNSO host is ∼2.92 eV. In addition, the mechanism of quenching concentration and energy-transfer of SNSO:Mn4+ were explored and analyzed in detail through calculation. The UV–Vis diffusion reflectance spectra demonstrated that samples had strong absorption (200–550 nm) in the ultraviolet(UV) and near-ultraviolet(NUV) region. The thermal stability of SNSO:Mn4+ was excellent (I423K/I273K = 39.84%). The internal quantum efficiency is 56.2%. In brief, the prepared phosphors had potential application in indoor plant growth as a LED lamp.

Near UV excitable warm white light emitting Zn doped γ-Ga2O3 nanoparticles for phosphor-converted white light emitting diode

Optical properties of Zn doped γ-Ga2O3 nanoparticles are investigated for the generation of white light, using near UV LED chip for phosphor-converted WLED (pc-WLED) application. Sol-gel combustion technique is adopted for the synthesis of Zn doped γ-Ga2O3 nanoparticles. The synthesized Ga2O3 nanoparticles are formed as metastable γ-phase with the face-centred cubic crystal structure. The structural stability is maintained up to 15 mol% doping of Zn ions. Formation of aggregated ultrafine particles of undoped and Zn doped γ-Ga2O3 with size less than 4 nm is found from TEM results. Doping of Zn ions has altered the optical band gap of γ-Ga2O3, and it varies from 4.13 to 3.97 eV. Broad visible emission in the wavelength range of 400–600 nm is observed and broadening of emission band increases after Zn doping. Formation of high defect concentration and smaller size of 10 mol% Zn doped γ-Ga2O3 nanoparticles resulted in higher emission intensity. Wide photoluminescence excitation band from 330 to 475 nm suggests that wide visible emission can be obtained from Zn doped γ-Ga2O3 nanoparticles with the excitation of both near UV and blue light. The bi-exponential behavior of PL decay curves of emission bands at the blue and yellow region indicated the complicate luminescence process of Zn doped γ-Ga2O3. The estimated lifetime of blue emission varies from 30 to 37 ns and of yellow emission varies from 54 to 62 ns. Under the excitation of 375 nm LED chip, warm white light emission with CIE color coordinates of (0.42, 0.33), color rendering index of ~ 87 and CCT of 2365 K is obtained for 10 mol% Zn doped γ-Ga2O3 nanoparticles which exemplifying its potential application in pc-WLED fabrication.

Color-Tunable Phosphor [Mg1.25Si1.25Al2.5]O3N3:Eu2+—A New Modified Polymorph of AlON with Double Sites Related Luminescence and Low Thermal Quenching

Aluminum oxynitride (AlON) was commonly used in functional ceramic materials, including phosphors for white light-emitting diodes (LEDs). In the current work, a new polymorph of AlON structure, single phase [Mg1.25Si1.25Al2.5]O3N3, has been devised and synthesized through the solid-state reaction at a rather low temperature of 1550 °C. Its structure has been calculated by the Rietveld refinement. The [Mg1.25Si1.25Al2.5]O3N3 crystallizes in trigonal with lattice parameters of a = b = 3.0312 Å, c = 41.5758 Å, V = 330.83 Å3, respectively, and it is formed by Mg2+ and Si4+ ions replacing partical Al3+ ions of Al5O3N3. The photoluminescence spectra of a series of Eu2+ doped [Mg1.25Si1.25Al2.5]O3N3 show a tunable light ranging from cyan to orange with a full-spectrum-covered emission and a wide excitation band with two peaks located at 290 and 335 nm. This is resulted from the two possible sites offered by the cation substitution for Eu2+ to occupy and thus broadening the emission spectra, which significantly enrich the monotonous luminescent properties of conventional AlON phosphors. Additionally, the energy transfer from one site to another has been identified using the decay curves and time-resolved emission spectra. The scanning electron microscopy and transmission electron microscopy characterization confirmed the sample's great crystallinity and the thermal stability with more than 85% of the initial intensity at 250 °C further indicates its potential in white LED applications.