Bright Red Light Research Articles

Novel self-activated red-emitting CsSrEu (PO3)6 phosphor: Synthesis, luminescent properties and enhancement by partially anion substitution

Novel self-activated red-emitting CsSrEu(PO3)6 was synthesized by high-temperature solid-phase method, and their enhanced luminescence were obtained by the modification of local structure. CsSrEu(PO3)6 was efficiently excited at 394 nm and emitted bright red light centered around 609 nm. Their luminescence intensity of CsSrEu(PO3)6 phosphor substituted by (BO3)3-/(SiO4)4- is about 1.346 or 1.454 times of the initial values respectively. The temperature-dependent luminescent spectra show that the emission intensity of CsSrEu(PO3)6 substituted by (BO3)3-/(SiO4)4- at 423 K remains 90.9 % and 86.6 % of the initial value respectively. The internal quantum efficiency is 88.4 % and 83.5 % respectively. White light-emitting diode fabricated by the phosphors, commercial blue-green phosphors and 395 nm chips show high color quality. The overall results indicate that the CsSrEu(PO3)6 phosphor substituted by (BO3)3-/(SiO4)4- group is promising candidate in warm white LED and anionic group substitution can be used to optimize luminescent properties of phosphors.

Genesis and Related Reservoir Development Model of Ordovician Dolomite in Shuntogol Area, Tarim Basin

The Ordovician thick dolostone in Shuntogol area of the Tarim Basin has the potential to form a large-scale reservoir, but its genesis and reservoir development model are still unclear. Starting from a sedimentary sequence, this study takes a batch of dolostone samples obtained from new drilling cores in recent years as the research object. On the basis of core observation and thin section identification, trace elements, cathodoluminescence, carbon and oxygen isotopes, rare earth elements, and X-ray diffraction order degree tests were carried out to discuss the origin of the dolomite and summarize the development model of the dolostone reservoir. The analysis results show that the Ordovician dolomite in the study area had a good crystalline shape, large thickness, high Fe and Mn values, and mostly showed bright red light or bright orange–red light under cathode rays. The ratio of δ18O values to seawater values at the same time showed a negative bias; the δCe values were negative anomalies, the δEu values were positive anomalies, and the order degree was high. This indicates that the dolomitization process occurred in a relatively closed diagenetic environment. The Ordovician carbonate rocks in the study area were low-lying during the sedimentary period, and with the rise of sea level, the open platform facies continued to develop. When the Middle and Lower Ordovician series entered the burial stage, the main hydrocarbon source rocks of the lower Cambrian Series entered the oil generation peak, and the resulting formation overpressure provided the dynamic source for the upward migration of the lower magnesium-rich fluid, and the dolomitization fluid entered the karst pore system in the target layer to produce all the dolomitization. This set of dolostone reservoirs is large in scale and can be used as a favorable substitute area for deep carbonate exploration for continuous study.

Alkali Metal–Substitution–Induced Confinement Effect for Designing High Phase–Transition–Temperature Molecular–Based Compounds Exhibiting Strong Photoluminescence

AbstractOrganic–inorganic hybrid phase–transition molecular materials have attracted increasing attention due to their excellent properties of combining inorganic and organic components. However, few research has been conducted on rare‐earth–based bimetallic organic–inorganic hybrids. Here, we successfully constructed a series of rare–earth–based organic–inorganic hybrid multifunctional materials, (C6H14N2)2EuX(NO3)6O2 (X=Na, K, Rb), with reversible phase transition, switchable dielectric, photoluminescence and semiconductor properties. Specifically, the phase‐transition temperature of three compounds are determined to be 364, 405 and 440 K, respectively. By the confinement effect caused by the variation of alkali metal elements in the two–dimensional structure, the phase transition temperature is successfully increased by 76 K. Meanwhile, the solid–state photoluminescence of three compounds displays bright red light at room temperature. Additionally, the bandgaps of three compounds are determined to be 3.21, 3.53 and 3.32 eV, respectively. It is expected that the strategy of alkali metal substitution proposed in this work will provide new thoughts for the design of multifunctional organic‐inorganic hybrid crystals.

Combustion synthesis, structural and photoluminescent investigations of Eu3+ activated crystalline Ba2BiV3O11 nanomaterials for multifunctional applications

Nanocrystalline Ba2BiV3O11 phosphor activated with lanthanide ion (Eu3+) has been successfully developed via a solution combustion approach. Various characterization techniques were implemented to explore the crystal structure, morphological behavior, photoluminescence, and chromatic aspects of Eu3+: Ba2BiV3O11 nanophosphors. Rietveld refinement was exercised to attain the phase purity and various crystallographic parameters. Transmission Electron Microscopy (TEM) technique was employed to analyze the crystallite size of the developed nanocrystals which is also in agreement with the size calculated from Scherrer formalization and W-H (Williamson-Hall) plot. Morphological behavior was studied with the help of Scanning Electron Microscopy (SEM) measurements. The most intense peak centered at 622 nm (5D0 → 7F2) in emission spectra was noted for Eu3+: Ba2BiV3O11 nanophosphors under 348 nm excitation. Kubelka-Munk function computed the Egap for the host along with the optimized sample and the outcomes evolved as 3.47 eV and 3.41 eV, respectively. Auzel’s model was executed to attain the radiative lifetime (1.3467 ms) for 5D0 electronic state. The CIE coordinates (x = 0.5990, y = 0.4003), CCT values (1710 K), quantum efficiency (87 %), and emission of bright red light indicate the promising behavior of Ba2Bi0.9Eu0.1V3O11 nanophosphor to use in the imaging applications, wLEDs, temperature sensing, and solid-state lighting (SSLs) appliances.

Er3+/Yb3+ ions doped chiral inorganic nanostructured BiOCl phosphor as a novel temperature sensing material

AbstractInorganic chiral materials have attracted increasing attention due to their application prospects. In this work, we synthesized the chiral nanostructured bismuth oxychloride co‐doped with Er3+/Yb3+ phosphor (D‐BYEP) by hydrothermal growth with a subsequent air‐annealing strategy using chiral sugar alcohols as the chiral inducer. The D‐BYEP emitted bright red light under the excitation of 980 nm near‐infrared laser. The temperature sensing behavior was evaluated by employing the thermally coupled (TCLs) or non‐thermally coupled (NTCLs) levels of Er3+. The maximum relative sensitivities (SR) obtained are 0.84% K−1 and 1.30% K−1 (298 K), respectively. The results show that the D‐BYEP may be ideal candidates for optical temperature sensors. We anticipate that this new type of inorganic chiral phosphor may have a range of applications in temperature measurement of light sources.

Ultra-broadband bright light emission from a one-dimensional inorganic van der Waals material

One-dimensional (1D) van der Waals materials have emerged as an intriguing playground to explore novel electronic and optical effects. We report on inorganic one-dimensional SbPS4 nanotube bundles obtained via mechanical exfoliation from bulk crystals. The ability to mechanically exfoliate SbPS4 nanobundles offers the possibility of applying modern 2D material fabrication techniques to create mixed-dimensional van der Waals heterostructures. We find that SbPS4 can readily be exfoliated to yield long (>10 μm) nanobundles with thicknesses that range from 1.3 to 200 nm. We investigated the optical response of semiconducting SbPS4 nanobundles and discovered that upon excitation with blue light, they emit bright and ultra-broadband red light with a quantum yield similar to that of hBN-encapsulated MoSe2. We discovered that the ultra-broadband red light emission is a result of a large ∼1 eV exciton binding energy and a ∼200 meV exciton self-trapping energy, unprecedented in previous material studies. Due to the bright and ultra-broadband light emission, we believe that this class of inorganic 1D van der Waals semiconductors has numerous potential applications, including on-chip tunable nanolasers, and applications that require ultraviolet to visible light conversion, such as lighting and sensing. Overall, our findings open avenues for harnessing the unique characteristics of these nanomaterials, advancing both fundamental research and practical optoelectronic applications.

Mitochondria-targeted fluorescent probe for simultaneously imaging viscosity and sulfite in inflammation models.

Many diseases in the human body are related to the overexpression of viscosity and sulfur dioxide. Therefore, it is essential to develop rapid and sensitive fluorescent probes to detect viscosity and sulfur dioxide. In the present work, we developed a dual-response fluorescent probe (ES) for efficient detection of viscosity and sulfur dioxide while targeting mitochondria well. The probe generates intramolecular charge transfer by pushing and pulling the electron-electron system, and the ICT effect is destroyed and the fluorescence quenched upon reaction with sulfite. The rotation of the molecule is inhibited in the high-viscosity system, producing a bright red light. In addition, the probe has good biocompatibility and can be used to detect sulfite in cells, zebrafish and mice, as well as upregulation of viscosity in LPS-induced inflammation models. We expect that the dual response fluorescent probe ES will be able to detect viscosity and sulfite efficiently, providing an effective means of detecting viscosity and sulfite-related diseases.

Facile fabrication of PF-540-Eu@TOCNF films with hydrophobic and photoluminescent properties

Based on the biodegradable natural polymer compound TEMPO-oxidized cellulose nanofibrils, and using EuCl3·6H2O, 3-aminopropyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyltrimethoxysilane as functional reagents, a novel type of cellulose nanofibril composite films with hydrophobic and photoluminescent properties was fabricated by a simple solvothermal method. The effects of reaction time, reaction temperature, Vol.% C2H5OH, solvents dosage, and n (Eu3+: COOH) on the photoluminescence and hydrophobicity of the films were investigated, while the films were characterized by using UV meter, fluorescence spectrometer, contact angle meter, FT-IR, XPS, SEM, EDS, TEM, XRD and TG. The results demonstrate that the surface of the film is uniformly loaded with Eu3+ and emits bright red light under UV irradiation, which has excellent photoluminescence, hydrophobicity (water contact angle 137.6°) and higher thermal stability. And high-value applications of nanocellulose in the fields of bioimaging, anti-counterfeiting and sensing detection in the low-temperature and high-humidity environment will be expanded.

Structure, luminescence properties and anti-thermal quenching of a novel Eu3+-activated red phosphor based on the negative thermal expansion material In0.5Sc1.5(MoO4)3

A new Eu3+-doped phosphor was synthesized by the high-temperature solid-state method based on In0.5Sc1.5(MoO4)3 with negative thermal expansion characteristics in the wide temperature range. The phosphor was pure phase, and the Eu3+ occupied the Sc3+-site. The main emission peak of the phosphor was located at 615 nm, which was attributed to the 5D0-7F2 energy level transition of Eu3+, and the fluorescence lifetime was between 297 and 493 μs. Its quenching concentration was 8 mol%, and the non-radiative energy transfer mechanism between Eu3+ ions was mainly exchange interaction. Under the excitation of 246 nm, the luminous intensity of phosphor was thermically enhanced after 348 K and showed near-zero thermal quenching characteristic. It could be attributed to the positive thermal expansion of phosphor change into two-dimensional negative thermal expansion. At 465 nm excitation, it also exhibited the anti- thermal quenching property and the luminous intensity remained 103.4 % at 423 K of that at the room temperature. The internal quantum efficiency of In0.5Sc1.5(MoO4)3: 8 mol% Eu3+ phosphor was 57.8 %, while the overall color purity was as high as 99.52 %. The LED device packaged it with a commercial LED chip could emit bright red light. Its comprehensive luminous properties were better than the commercial red phosphor Y2O3: Eu3+. The results showed that In0.5Sc1.5(MoO4)3: Eu3+ was a new red phosphor with good luminous performance and anti-thermal quenching characteristic.

Al3+ doping enhanced photoluminescence properties of Ca2InNbO6: Mn4+ far-red phosphor for plant cultivation

The study focuses on the synthesis of far-red phosphors Ca2InNbO6: xMn4+ (0 ≤ x ≤ 0.006) and Ca2InNbO6: 0.003Mn4+, yAl3+ (0 ≤ y ≤ 0.024). First-principles calculations confirmed that the indirect bandgap of Ca2InNbO6 used to be 3.522 eV. Photoluminescence spectroscopy was used to examine the luminescence characteristics and energy transfer mechanism of CINO: xMn4+ and CINO: 0.003Mn4+, yAl3+ phosphors. When Mn4+ ions undergo the 2Eg → 4A2g transition under 380 nm excitation, brilliant red light with a central wavelength of 688 nm is released. In addition, the emission intensity reaches 2.6 times that of CINO: 0.003Mn4+, when Al3+ has a 1.2% optimal doping concentration. At the same time, the thermal stability of the material is improved. The reasons for the enhanced fluorescence and thermal stability were analysed by lattice distortion and blocking of energy transfer. Additionally, the prepared red LED lamps, which shown a bright red light even after long periods of operation at high temperatures, were used for the cultivation of plant seeds, and the germination rate as well as the stems and leaves thriving growth were significantly better than the cultivation without the red LED, suggesting that Al3+ doping Ca2InNbO6: Mn4+ has potential applications in the field of plant cultivation and growth LEDs, and is a guide for ion-doped modified phosphors.

Blue, Yellow, and Red Carbon Dots from Aromatic Precursors for Light-Emitting Diodes.

In this work, multicolor fluorescent carbon dots with red (R-CDs), yellow (Y-CDs), and blue (B-CDs) emissions were prepared by choosing proper aromatic precursors with different amounts of benzene rings through a simple solvothermal method. The characterization showed that the prepared carbon dots were spherical with a size under 10 nm, rich surface functional groups, and good stability. The emission wavelengths were located at 440, 530, and 580 nm under the excitation of 370 nm. The relative fluorescence quantum yield (QY) of R-CDs, Y-CDs, and B-CDs was 11%, 59%, and 33%, respectively. The related characterization demonstrated that the redshift in the photoluminescence was caused by the synergistic effect of the increasing graphitic nitrogen content, quantum size effect and surface oxidation state. By mixing the three prepared CDs into a PVA matrix, the transparent and flexible films produced relucent blue, yellow, and red emissions under 365 nm UV light, and solid-state quenching was effectively avoided. LEDs were fabricated by using B-CDs, Y-CDs, and R-CDs/PVA with a semiconductor chip. These CDs-based LEDs produced bright blue, yellow, and red light with CIE color coordinates of (0.16, 0.02), (0.38, 0.58), and (0.50, 0.49) were successfully manufactured utilizing the prepared blue, yellow and red multicolor carbon dots as the solid luminescent materials. The results showed that the synthesized CDs can be potentially applied in multi-color monitors as a promising candidate for light-emitting diodes (LEDs). This work blazes a novel trail for the controllable preparation of multicolor fluorescent carbon dots.

Effects of Europium Complex on Thermal and Photoluminescence Properties of Polyurethane-Europium Materials.

A europium complex with double bonds was synthesized with crotonic acid as the ligand and a europium ion as the center ion. Then, the obtained europium complex was added to synthesized poly(urethane-acrylate) macromonomers to prepare the bonded polyurethane-europium materials by the polymerization of the double bonds in the complex and the poly(urethane-acrylate) macromonomers. The prepared polyurethane-europium materials had high transparency, good thermal stability and good fluorescence. The storage moduli of polyurethane-europium materials are obviously higher than those of pure polyurethane. Polyurethane-europium materials exhibit bright red light with good monochromaticity. The light transmittance of the material decreases slightly with increases in the europium complex content, but the luminescence intensity gradually increases. In particular, polyurethane-europium materials possess a long luminescence lifetime, which has potential applications for optical display instruments.

Structural, morphological, and photoluminescence study of Europium doped spinel ZnAl2O4 phosphors

Nanocrystalline Eu-doped Zinc aluminate spinel was produced by a combustion method. Different methods, including X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and photoluminescence spectroscopy, were used to examine the prepared spinel type ZnAl2O4 ceramic material and characterize its structural, morphological, and photoluminescent properties. The formation of a pure phase with a spinel structure and the space groupfd3 ̅m is confirmed by the zinc aluminate material's X-ray diffraction pattern. Scan and transmission electron microscopy were used to further establish the average surface structure and crystalline size. The PL spectra show the strongest emission at 616 nm corresponds to the 5D0 → 7F2 transition of Eu3+. Photometric parameters like CIE coordinates and CCT values show that prepared phosphor that gives off a bright red light is used in the display and lamp industries.

Concentration quenching inhibition and fluorescence enhancement in Eu3+-doped molybdate red phosphors with two-phase mixing.

Red phosphor plays a crucial role in improving the quality of white light illumination and backlight displays. However, significant challenges remain to enhance red emission intensity in different matrix materials. Herein, a class of two-phase mixing red phosphors of NaIn1-x(MoO4)2:xEu3+ (NIMO:xEu3+) has been successfully prepared by the traditional high-temperature solid-state reaction method. The coordination environment, phase structure, excitation and emission spectra, fluorescence kinetics, and temperature-dependent luminescence properties of the system have been studied comprehensively. It is worth mentioning that the red emission intensity continues to increase with the increased Eu3+ doping concentration, and the fluorescence lifetimes remain unchanged. These extraordinary phenomena mainly stem from the special concentration quenching mechanism in such two-phase mixing material, namely, the increased lattice interface barriers from Eu six-coordinated units and Eu eight-coordinated units can effectively block the non-radiation by enlarging the average distance between luminescent centers. The improved fluorescence thermal stability and suppressed non-radiative transition rate in NIMO:40%Eu3+ sample are further proving regulatory role of lattice interface barriers. In addition, a warm white light-emitting diode (LED) is successfully fabricated, exhibiting Commission Internationale de l'Eclairage (CIE) coordinates of (0.343, 0.335), a color rendering index (CRI) of 92.1, and a correlated color temperature (CCT) of 5013 K, showing significant application prospects for high-quality lighting devices.

Occipital cortex activity in response to melanopsin in healthy humans

AbstractPurpose: Melanopsin‐expressing retinal ganglion cells (mRGCs) signal light information to the brain and mediate non‐visual physiologic responses. Animal studies suggest that melanopsin also influences the visual pathway via synaptic contacts in the lateral geniculate nucleus and the superior colliculus. In healthy and blind humans, blue light exposure results in modulation of occipital activity in neuroimaging studies, presumably from melanopsin interaction with photoreceptors. This study examined if melanopsin activation influences the visual evoked potential (VEP).Methods: We recorded VEPs to light flash stimuli to activate cones, rods and melanopsin in 30 healthy volunteers (red: 630 nm, blue: 445 nm, intensities: 0.00003 to 150 cd/m2). Dark adaptation was used to sensitize rods. At 2 log cd/m2, rods are saturated, and bright blue lights are considered more melanopsin activating. Under photopic conditions, red light activates M‐L cones. Amplitude and latency of the N2 and P2 components of the VEP were evaluated.Results: P2 obtained from the melanopsin stimulus presented under dark‐adaptation (MEL1) had the largest amplitude and shortest latency of all VEPs including the melanopsin stimulus presented non‐dark adapted condition (MEL2). There was no difference of N2 between MEL1 and MEL2 conditions. The latency of N2 and P2 from rods was longer than that from MEL1 and MEL2. P2 from MEL2 was equivalent in amplitude and latency to the P2 of the brightest cone stimulus (30 cd/m2 red light).Conclusion: Under non‐dark‐adapted conditions, bright blue light evokes a similar VEP as bright red light, suggesting that cones are the predominant influence in these conditions. However, bright blue light presented under dark adaptation modified the VEP latency and amplitude. As rod VEPs are distinguished by slow latencies, then we propose that these changes arise from mRGCs influence on cone‐mediated visual pathways to the occipital cortex.

Synthesis and optical properties of Mn4+ activated double-perovskite niobate deep red phosphors for WLEDs and plant cultivation

Mn 4+ doped oxides red phosphors have great potential for white-light-emitting diodes (WLEDs) and plant growth light. Herein, deep red phosphors Ba 2 LuNbO 6 :xMn 4+ with perovskite structure were synthesized by solid state method in air atmosphere. The crystal structure, morphology, composition and optical properties of Ba 2 LuNbO 6 :Mn 4+ phosphors were systematically studied by X-ray diffraction, Rietveld refinement, SEM and EDS and photoluminescence spectra. Under excitation by 380 nm NUV light, the phosphor emitted bright red light around 670 nm and far-red light around 697 nm owing to the spin-forbidden 2 E g → 4 A 2g transition of Mn 4+ ions. Temperature-dependent photoluminescence spectra confirmed the high thermal stability of Mn 4+ -activated Ba 2 LuNbO 6 phosphors. The fluorescence intensity maintained about half of the initial intensity at 400 K, and the thermal quenching was due to the increase of non-radiative transitions at high temperature. Finally, LED devices were fabricated using 365 nm NUV chips with commercial blue, green phosphors and Ba 2 LuNbO 6 :Mn 4+ red phosphors for the use of outdoor lighting, which had color rendering index (CRI) of 84.4 and color temperature (CCT) of 5710 K. The results indicate that Ba 2 LuNbO 6 :Mn 4+ phosphors have great potential as a deep red phosphor in the field of WLEDs and plant growth light. • Deep red phosphor Ba 2 LuNbO 6 :Mn 4+ were prepared by high temperature solid state method in air atmosphere for WLEDs and plant cultivation. • The Ba 2 LuNbO 6 :Mn 4+ phosphor presents deep red emission from 650 nm to 720 nm. • Ba 2 LuNbO 6 :Mn 4+ phosphors have excellent photoelectric performance for LED application.

Novel Sm3+-activated YCa4O(BO3)3 phosphors with high quantum efficiency and thermal stability for red-backlight display and indoor illumination

Novel Sm3+-activated YCa4O(BO3)3 (YCOB) phosphors with high color purity, excellent thermal stability and high luminescence quantum efficiency were developed. Upon 405 nm excitation, all samples displayed strong orange-red emissions. The crystal structure and luminescence characteristics of YCOB in relation to Sm3+ concentrations were explored. The optimal doping concentration was found to be 5% mol with remarkable color purity of 97.73%. The concentration quenching mechanism in YCOB host lattices was dominated by dipole-dipole interaction. Meanwhile, temperature-dependent luminescence spectra revealed that the investigated phosphors have excellent thermal stability. Impressively, it was calculated that the internal quantum efficiency of synthesized phosphors was as high as 76.54%. To further verify the practicability of synthesized phosphors, both red light-emitting diodes and white light-emitting diodes were fabricated using YCOB: 5%Sm3+ phosphors, and they exhibited bright red and white light, respectively. These results suggest that the novel YCOB: Sm3+ phosphors with high quantum efficiency and luminescent stability were promising for red-backlight display and indoor illumination.

Red-emitting carbon dots as luminescent agent in wide-range water detection in organic solvents and polarity-selective zebrafish imaging

Heteroatom-doped carbon dots with promising luminescent properties are excellent candidates for sensing and imaging applications. Herein, we reported a facile one-step hydrothermal synthesis of highly-fluorescent red-emitting carbon dots (R-CDs) with quantum yield of 37.2 %. R-CDs exhibit a maximum emission band at 640 nm under the excitation wavelength of 500 nm. Furthermore, R-CDs show excitation-dependent and solvent-engineered fluorescent characteristics that the luminescent properties could be greatly affected by polarity. Due to the sensitivity to polarity, a quick and precise approach for wide-range water detection in organic solvents has been developed. Because of the low autofluorescence background, R-CDs were applied to the zebrafish larvae imaging. Polarity-selective bright red light from R-CDs is seen in the low-polarity organs like yolk sac and eyes, which contain abundant lipids and lipoprotein. Our results demonstrate that R-CDs could be used as bio-imaging agents and fluorescent sensors for quantitative and visual water detection in various organic solvents. • High-fluorescent red-emitting carbon dots are synthesized from hydrothermal treatment of DMAB and boric acid. • Bright red emission at 640 nm (λ ex = 500 nm) and high QY of 37.2 % are achieved. • The variation of the emission intensity of R-CDs is highly dependent on solvent polarity. • Polarity-selective bright red light from R-CDs is seen in the low-polarity organs like yolk sac and eyes.

Bright light therapy as a non-pharmacological treatment option for multiple sclerosis-related fatigue: A randomized sham-controlled trial

Fatigue is a common symptom in people with multiple sclerosis (pwMS) that significantly impairs quality of life. Bright light therapy may be a cheap treatment option with little to no adverse events. To evaluate the effectiveness of bright light therapy as a treatment option for MS-related fatigue. This was randomized sham-controlled trial including 26 pwMS with a Fatigue Severity Scale (FSS) Score ≥36. Participants were assigned to receive either bright white light therapy (n = 13) or dim red light (sham-intervention; n = 13). Participants used the respective intervention for 30 min each morning for two weeks, followed by a two-week washout period. The primary endpoint was the difference in FSS scores following light treatment as calculated by analysis of covariance. There was no significant difference in FSS (F(1,23) = 2.39, p = .136, partial ⴄ2 = .094). However, FSS scores generally improved over the course of the study in a clinically relevant manner. Bright light therapy decreased FSS scores over the course of this study. However, this effect was not significant in comparison to a sham intervention.

High Thermal Stability and Color Purity of Y2SrAl4SiO12: Eu3+ Garnet-Variant-Structured Phosphor for Warm White Light LED-Lamp

Red LEDs with a high color purity and high color rendering index are often used to compensate for the lack of red-light components in current white LEDs. Therefore, the new type of garnet-structured high color purity red phosphor Y2−xSrAl4SiO12: xEu3+ was synthesized by the solid-state method. The band gap structure of the host matrix was studied through the DFT calculation and found that the matrix belongs to a direct band gap structure with a band gap size of 4.535 ev. The phosphor exhibits a wide excitation spectrum under the monitoring of 710 nm. The strongest excitation wavelength is 393 nm, and it exhibits bright red light under the excitation of 393 nm, and the emission peak positions are located at 570 nm, 597 nm, 613 nm, 650 nm, 710 nm and 748 nm, respectively, which are attributed to the 5D0→7Fj of Eu3+ (j = 0–5) electronic transitions. In the crystal structure of Y2SrAl4SiO12, Eu3+ occupies a symmetry site. The compositional changes and thermal studies found favorable at 20% mol. At this concentration, the luminescence intensity gradually weakened due to the Eu3+ electric multi-level interaction. It is worth noting that the emission intensity of Y2SrAl4SiO12: 20%Eu3+ at 433 K can be maintained to 92% of that at 293 K. Finally, we combined it with the NUV chip and packaged it into a red LED with a color purity of up to 90% and a correlated color temperature of 1492 K. The high purity, low color temperature and thermal stability indicate that it has a place in LED applications.