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ZnGa2Se4, a nonlinear material with wide mid infrared transparency and good thermomechanical properties
摘要： During the last decades, mid-infrared (3–12 μm) laser sources using crystals with nonlinear optical properties have attracted a particular attention due to their potential applications in different fields such as optical counter-measures and remote chemical sensing. As transparency of common oxide crystals is limited to about 4 μm, many researches have been focused on chalcopyrite compounds because of their wide transparency in the mid-IR range and their strong nonlinear optical coefficients. There is a need of such crystals able to convert efficiently the near infrared wavelengths from commercially available lasers into wavelengths higher than 5 μm through Optical Parametric Oscillators (OPO) systems. This paper presents a new compound: ZnGa2Se4 (ZGSe). Measurements made on dense polycrystals show a high thermal conductivity value in comparison with other selenides (2.9 W m?1 K?1), a wide transparency from visible to beyond the band III of the mid IR (0.6 μm–17 μm) and a coefficient of thermal expansion inferior to 10?5 K?1. These results are very encouraging and improvements of the growth process are now undertaken to obtain single crystals with the required optical quality.
关键词： Optical materials and properties,ZnGa2Se4,Crystal growth,Thermomechanical properties
更新于2025-11-19 16:56:35
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Green Hydrothermal Synthesis of Fluorescent Carbon Dots from Glucose and Taurine for Fe3+ and pH Sensing
摘要： Carbon nanodots (C-dots), as a class of heavy-metal-free fluorescent nonmaterial have drawn increasing attention due to their strong photoluminescence (PL), good biocompatibility, and low toxicity. Herein, we synthesize nontoxic fluorescent C-dots by hydrothermal treatment of the mixture of glucose and taurine, in which process the formation and the surface passivation of C-dots take place simultaneously. The influence of reaction temperature, reaction time and feed ratio of glucose to taurine on the PL property of C-dots is studied. As the C-dots exhibit sensitive pH and iron ion dependent PL property, they can be used for pH and Fe3+ sensing in solutions.
关键词： Nanoparticles,Optical materials and properties,Carbon materials
更新于2025-09-23 15:22:29
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Label-free nanoparticle sensors based on a triple-layer-coated microsphere structure
摘要： We present a design for a sensitive, label-free nanoparticle sensor based on triple-layer-coated microsphere resonators. The surfaces of the microsphere structure are coated with three layers that have high, low, and high refractive indexes from inside to outside, respectively. We theoretically and numerically investigate two cladding modes, we call the inner mode and outer mode. The resonance wavelengths of the two modes are used to detect the resonance wavelength shift caused by a single-nanoparticle. Numerical calculation suggests that if we change the thickness of the middle layer, the device offers another degree of freedom to obtain higher detection sensitivity. We build a model to accurately describe a nanoparticle close to the microsphere. The method for the sensors may promote the design of biosensing applications.
关键词： Optical materials and properties,Sensors,Simulation and modelling,Microstructure
更新于2025-09-23 15:22:29
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Phase formations and red-luminescence enhancement of Eu3+-activated NaBaY(BO3)2 phosphors
摘要： Eu3+-activated Na1-xKxBaY(BO3)2 (x = 0.1–1.0) phosphor was prepared via facile solid-state reaction ceramic method. The structural Rietveld refinements were completed to confirm the phase formations. The luminescence properties were reported such as photoluminescence excitation (PLE) and emission (PL) spectra, decay lifetime, experimental quantum efficiency (QE) and thermal stabilities. The phase formations and the luminescence properties of the phosphors have a dependence on the K+-substituting for Na+ in the lattices. The results showed that Na1-xKxBaY0.5Eu0.5(BO3)2 (x = 0.1–1.0) phosphors formed the trigonal NaBaY(BO3)2 single phase (Na-phase, space-group of R-3, No.148). Increasing the K+-substituting for Na+ (x ≤ 0.3) induced the appearance of KBaY(BO3)2 phase (K-phase, space-group of R-3 m, No. 166) together with the Na-phase (0.3 < x < 0.6). Heavily K-substituted samples crystallized into a single K-phase. Luminescence characteristics of Eu3+ ions were investigated on the evolution of the substituting-level. It was observed that the phosphors presented the improved emission intensity and thermal stability in the mixed phases.
关键词： Phase transitions,Photoluminescence,Optical materials and properties,Europium,Borates
更新于2025-09-23 15:22:29
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Eu3+ co-doped Sr3Gd(PO4)3:Dy3+ phosphors: luminescence properties and color-tunable white-light emission for NUV-WLEDs
摘要： A series of Dy3+ and Eu3+ co-doped Sr3Gd(PO4)3 phosphors were synthesized by a high-temperature solid-state method. The crystal structure, optical band gap energy, luminescence properties, concentration quenching, energy transfer process and thermal stability were investigated. All the phosphors are pure eulytite-type Sr3Gd(PO4)3 in structure. Under different wavelengths’ excitation, the Sr3Gd(PO4)3:Dy3+, Eu3+ phosphors exhibit different emission intensities for Eu3+ and Dy3+. The color and correlated color temperature (CCT) can be tuned from cool white to warm white by adjusting excitation wavelengths and the doping concentration of Eu3+. Under the 351-nm excitation, the optimal Sr3Gd(PO4)3:0.03Dy3+, 0.085Eu3+ phosphor displays a warm white emission with CIE coordinate of (0.3987, 0.3613), CCT of 3409?K, internal quantum efficiency of 44.8% and activation energy of 0.1883?eV. These results suggest that single-phased white-emitting phosphors Sr3Gd(PO4)3:Dy3+, Eu3+ can be used in the near-ultraviolet light-emitting diodes.
关键词： Optical materials and properties,Luminescence,Energy transfer,Phosphors
更新于2025-09-19 17:13:59
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Eu3+-doped NaYGeO4: A novel red-emitting phosphors for ultraviolet or blue chips excited white LEDs
摘要： A novel red-emitting phosphor NaYGeO4: Eu3+ has been prepared by a high temperature solid state method. All the Eu3+ ions are completely dissolved in the NaYGeO4 host without changing its crystal structure. Under 315 nm host excitation or 464 nm 7F0→5D2 excitation, the phosphor NaYGeO4: Eu3+ presents red emission with the strongest peak at 613 nm. The concentration quenching and luminescence mechanism are also investigated. The optimal NaYGeO4: 0.05Eu3+ phosphor displays high internal quantum efficiency, excellent thermal stability with the activation energy (?E) of 0.2716 eV. The color emission can be tuned by changing the Eu3+ concentration. The phosphor presents a great potential application for ultraviolet or blue excited white LED.
关键词： Optical materials and properties,Thermal stability,Luminescence,Red phosphor
更新于2025-09-12 10:27:22
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Luminescence properties of Sm3+ and Dy3+ co-doped BaY2ZnO5 phosphor for white LED
摘要： Single-phased warm-white-emitting BaY2ZnO5:Dy3+, Sm3+ phosphors were synthesized by a high-temperature solid state reaction method. The crystal structure, luminescence properties, decay lifetimes, thermal stability and internal quantum efficiency (IQE) were investigated. Under 354 nm excitation, the emission spectrum exhibits the characteristic transitions of Sm3+ and Dy3+ and energy transfer mechanism are determined to be the dipole-dipole interactions. Due to the energy transfer from Dy3+ to Sm3+, the color tones and correlated color temperature (CCT) can be changed from near cool-white to warm-white when adjusting Sm3+ concentrations. The optimal BaY2ZnO5: 0.14Dy3+, 0.04Sm3+ emits warm-white light with CIE coordinates of (0.404, 0.367), low CCT of 3337 K, activation energy of 0.2389 eV and IQE of 61.5%, making it as a promising candidate white-emitting phosphor for LEDs application.
关键词： Phosphors,Luminescence,Optical materials and properties,Energy transfer
更新于2025-09-12 10:27:22
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Luminescence properties of new red-emitting phosphor Li2Al2Si3O10:Eu3+ for near UV-based white LED
摘要： Eu3t doped Li2Al2Si3O10 red phosphor was synthesized by the conventional high-temperature solid-state method. The crystal structure, morphology, luminescence properties, thermal stability and quantum efficiency were characterized. The powders show average particle size of 8 μm. The optimum Eu3t dopant concentration is 0.02 in Li2Al2Si3O10 host lattice. Luminescence quenching is attributed to electric dipole–dipole interaction and impurities. The emission intensity of the 5D0 → 7F2 transition (615 nm) is dominant upon the strongest excitation at 394 nm (7F0 → 5L6 transition). The Li2Al2Si3O10: 0.02Eu3t phosphor can be excited by near-ultraviolet (n-UV) light and exhibits red emission with the CIE chromaticity coordinates of (0.6389, 0.3488) and color purity as high as 93%. The Li2Al2Si3O10: 0.02Eu3t phosphor also possesses good thermal stability with quenching energy barrier of 1803 cm?1. The fluorescence lifetime and quantum efficiency are 0.388 ms and 31.5%, respectively. The results suggest that the red phosphor Li2Al2Si3O10:Eu3t can be used for n-UV excited white LEDs.
关键词： Phosphors,Luminescence,Optical materials and properties
更新于2025-09-12 10:27:22
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Self-activated emission and spectral temperature-dependence of Gd8V2O17 phosphor
摘要： Gd8V2O17 was prepared via the facile solid-state reaction. The optical absorption, temperature-dependent luminescence, and decay lifetimes were investigated. Gd8V2O17 has a direct allowed electronic transition with band gap energy of 3.18 eV. Under the excitation of UV light, the phosphor shows the typical self-activated luminescence from the charge transfer (CT) transitions in VO4 3? groups. The emission intensity has a nearly constant value from 10 to 150 K, while it increases above 150 K. And the emission has an abnormal blue-shift with the increase of temperature from 10 to 300 K, so the luminescence color varies from green to blue. Over the whole temperature ranges, the maximum emission wavelength showed a linear dependence on temperature; consequently, the temperature-dependent properties have a potential advantage in luminescence thermometry. The luminescence mechanism was discussed on the proposed two VO4 emission centers and the energy transfer between them.
关键词： Vanadate,Luminescence,Optical materials and properties,Optical thermometry,Phosphorescence
更新于2025-09-10 09:29:36
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Efficient Chemical Synthesis of Functional Rare Earth Orthoborates Nanosheets and Their Photoluminescence Studies
摘要： In contrast to routine methods, LaxY1?xBO3:Eu3+ and Lay Lu1?y BO3:Eu3+ were ef?ciently prepared by a supersonic microwave co-assistance method within 60 minutes at 90 (cid:2)C. Orderly aggregated nanosheets were formed in high yields by preferential crystal growth processes. More importantly, it has never been reported that the magnetic-dipole transition with orange-color emissions (5D0 → 7F1) could be ?nely tuned based on the concentration variation of lanthanum elements. The electronic dipole transition (5D0 → 7F2) increases gradually when La/Y and La/Lu ratios are 4/1 and 7/3 respectively.
关键词： Microwave,Supersonic,Structural,Spectroscopy,Optical Materials and Properties
更新于2025-09-04 15:30:14