BaFCl：Eu^2＋,Eu^3＋的光激励发光过程

本文首次报道了ＢａＦＣｌ：Ｅｕ＾２＋,Ｅｕ＾３＋的光激励发光。实验结果发现,在ＢａＦＣｌ：Ｅｕ中Ｅｕ＾３＋对Ｅｕ＾２＋的光激励发光有增强作用。在ＢａＦＣｌ：Ｅｕ的光致发射光谱中同时观察到对Ｅｕ＾２＋、Ｅｕ＾３＋及基质的本征发射,而光激励发射光谱中只观察到Ｅｕ＾２＋的发射,表明光致发光与光激励发光存在着很大的差异。这些结果表明,发光中心Ｅｕ＾２＋、Ｅｕ＾３＋及基质之间存在着相互作用和能量传递。本文提     

X-ray imaging plate using CsBr:Eu phosphors for computed radiography

It is shown that X-ray-irradiated Eu-doped CsBr (CsBr:Eu) exhibits intense photostimulated luminescence (PSL). The peak wavelengths of PSL emission and stimulation spectra of CsBr:Eu phosphor ceramic samples are 450 and 690 nm, respectively. The dependence of PSL properties on preparing conditions of phosphor ceramic samples, such as Eu concentration, sintering temperature and sintering time, is studied. It is found that the PSL intensity of CsBr:Eu phosphor ceramics fabricated under optimum preparation condition is higher than that of commercially available imaging plates (IP) using BaFBr:Eu and BaFI:Eu. The image quality of the IP using CsBr:Eu phosphor film is better than that of commercially available IP.     

Luminescence properties of nano-sized Sr2MgSiO5: Eu2+, Mn2+ phosphors prepared by the sol-gel method

Nano-sized Sr2MgSiO5:Eu2+, Mn2+ phosphor was synthesized by the sol-gel method. The preparation conditions of the precursor were determined. The effect of Eu2+ and Mn2+ content on the luminescence intensity was studied. X-ray diffraction (XRD), photoluminescence spectra (PL), and photoluminescence excitation spectra (PLE) were used to characterize the samples. The results showed that the excitation bands ranged from 250 to 450 nm, and their peaks positioned around 365 nm. The emission spectrum consists of three bands: blue, green, and red, respectively. The blue and green emission bands originate from the center of the Eu2+, while the red emission band is attributed to the energy transfer from Eu2+ to Mn2+. White light can be obtained by mixing the three emission colors. The experiment results show that the Sr2MgSiO5:Eu2+, Mn2+ is a single host phosphor with superior properties for use in white light emitting diodes (white LED).     

Controlled synthesis and optical properties of BaFBr:Eu2+ crystals via ethanol/water solutions

BaFBr:Eu²⁺ crystals with different structures were successfully fabricated via a simple precipitation method using ethanol/water mixtures as solvents. The amount of ethanol in the solvent mixtures played a significant role in the formation of final products, enabling the well-controlled growth of the BaFBr crystals. A possible formation mechanism was proposed based on the results of controlled experiments. The phases and morphologies of the resulting samples were systematically investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED) and elementary analysis. The optical properties of the annealed BaFBr:Eu²⁺ nano-cuboids were investigated using photoluminescence (PL), photo-stimulated luminescence spectroscopy (PSL) and kinetic decays. Faster decay behaviors demonstrate that these BaFBr:Eu²⁺ phosphors are promising materials for applications in optical storage fields. Furthermore, it is envisaged that this environmentally benign method can be extended to prepare other fluoride halides.     

The effects of Mn2+ doping on the luminescence properties of 12CaO 7Al2O:Eu2+ nanocrystal phosphor

The long lasting blue phosphorescence (LLP) and photostimulated luminescence (PSL) after ultraviolet light irradiation at room temperature in 12CaO 7Al2O3:xEu2+, yMn2+ (x = 0, 0.001; y = 0, 0.01) prepared by the chemical co-precipitation method were observed. It was shown that novel oxide 12CaO 7Al2O3:Eu2+, Mn2+ (C12A7:Eu2+, Mn2+) with unique nanocage structure can store energy when irradiated with 365 nm photons. And photon energy can be subsequently released by exposed to 980 nm light. The codopant Mn2+ enhances the intensity of the persistent phosphorescence and PSL due to the existence of more shallow and new deeper electron traps in C12A7: Eu2+, Mn2+. A model for energy storing and recovering and the detailed mechanism of PSL are presented through comparing with the luminescence properties of the co-doped C12A7:Eu2+, Mn2+ and C12A7:Eu2+.     

Spherical SiO2 @ GdPO4: Eu3+ core-shell phosphors: sol-gel synthesis and characterization

Nanocrystalline GdPO4 : Eu3+ phosphor layers were coated on non-aggregated, monodisperse and spherical SiO2 particles by Pechini sol-gel method, resulting in the formation of core-shell structured SiO2 @ GdPO4 : Eu3+ particles. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), time-resolved PL spectra and lifetimes were used to characterize the core-shell structured materials. Both XRD and FT-IR results indicate that GdPO4 layers have been successfully coated on the SiO2 particles, which can be further verified by the images of FESEM and TEM. Under UV light excitation, the SiO2 @ GdPO4 : Eu3+ phosphors show orange-red luminescence with Eu3+ 5D0-7F1 (593 nm) as the most prominent group. The PL excitation and emission spectra suggest that an energy transfer occurs from Gd3+ to Eu3+ in SiO2 @ GdPO4 : Eu3+ phosphors. The obtained core-shell phosphors have potential applications in FED and PDP devices.     

Biotemplating of BaFBr:Eu for X-ray storage phosphor applications

The design of hierarchically patterned novel structures by replicating the cellular tissue of wood has recently attained increasing interest. X-ray storage phosphor BaFBr:Eu²⁺ is manufactured via vacuum assisted repeated infiltration of wood tissue (Pinus sylvestris). A submicrometer precipitate is formed via wet chemical reaction of NH₄F, BaBr₂·2H₂O and EuCl₃·6H₂O in methanol. According to scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), the original wood cell walls are filled with the precipitate and completely transformed into BaFBr struts after sintering at 800 °C. The optical properties of the biomorphous phosphor microstructure are determined by photoluminescence spectroscopy (PL) at room temperature, photo-stimulated luminescence spectroscopy (PSL) and cathodoluminescence spectroscopy (CL) in the SEM. A broadening of the PSL peak is observed and ascribed to the incorporation of calcium impurities present in the pine wood tissue. The potential of biotemplates for generating highly oriented and optically isolated μm- and sub-μm matrix of X-ray storage phosphor material is illustrated.     

Optical properties and luminescence dynamics of Eu3+-doped terbium orthophosphate nanophosphors

The development of luminescent inorganic nanocrystals (NCs) doped with rare-earth (RE) ions has attracted increasing interest owing to their distinct optical properties and versatile applications in time-resolved bioassays, multiplex biodetection, DNA hybridization and bioimaging. Hexagonal TbPO4:Eu3+ NCs (10-30 nm) were synthesized via a facile hydrothermal method assisted with oleic acid (OA) surfactants, which exhibit tunable emissions from green to red by varying the concentration of Eu3+. The Tb3+-to-Eu3+ energy transfer efficiency observed reaches up to 94%. Different from their bulk counterparts, a new interface-state band (316 nm) in addition to the commonly observed spin-forbidden 4f-5d transition band (265 nm) of Tb3+ was found to be dominant in the excitation spectrum of NCs due presumably to the formation of surface TbPO4/OA complexes, which provides an additional excitation antenna in practical utilization. Two kinds of luminescence sites of Eu3+ in TbPO4 NCs, with the site symmetry of C2 or C1, were identified based on the emission spectra at 10 K and room temperature. Furthermore, the photoluminescence (PL) dynamics of Tb3+ ions in pure TbPO4 NCs have been revealed. Compared to the exponential PL decay in bulk counterparts induced by very fast energy migration, the non-exponential decay from 5D4 of Tb3+ in TbPO4 NCs is mainly attributed to the diffusion-limited energy migration due to more rapid energy transfer from Tb3+ to defects than the energy migration among Tb3+.     

Synthesis and luminescence properties behavior of Eu(3+)-doped nanocrystalline and bulk GdVO4 phosphors by high-energy ball milling and solid state reaction

Europium-doped nanosized-GdVO4:Eu3+ powders and bulk GdVO4:Eu3+ powders were synthesized using a planetary ball mill and conventional solid state reaction method, respectively. The effects of the grain size on the crystallinity, morphology, structure and luminescence spectra were investigated by X-ray diffraction, field emission-scanning electron microscopy and photoluminescence spectroscopy (PL). The room temperature PL spectra of the GdVO4:Eu3+ nanophosphors showed four emission bands at 611, 615, 619 and 595 nm. The bands at 611, 615 and 619 nm were assigned to the 5D0 --> 7F2 transition of the EU3+ ion when excited with 312 nm light.     

Fabrication and luminescent enhancement of Eu3+-doped Y2O3@YOF core-shell nanocrystals

In this paper, a two-step synthesis method for preparing Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals is introduced. Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals were prepared by combining an autocombustion process with a low temperature solid state reaction. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and fluorescence decay were employed to characterize the prepared samples. The results of XRD, TEM and EDS indicated that the products prepared by this method were not a mixture of Y2O3:Eu3+ and YOF:Eu3+ nanocrystals, but Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals. Compared with Y2O3:Eu3+ nanocrystals, a 20% increment in luminescence intensity was observed in the Eu3+ ion-doped Y2O3@YOF core-shell nanocrystals, thus suggesting that coating with a YOF:Eu3+-shell can efficiently block the nonradiative relaxation channels that are induced by surface defect states.     

Optical spectroscopy of Eu3+ ions in tetragonal ZrO2 nanocrystals

A facile solvothermal method was introduced to incorporate Eu3+ ions into the monodisperse tetragonal ZrO2 nanocrystals (NCs) with small size of approximately 4 nm. The optical properties for Eu3+ doped ZrO2 NCs were investigated in detail by using the photoluminescence (PL) spectroscopy at room and low temperatures. Intense red emissions from Eu3+ ions could be achieved via the host sensitization, which was found to be much more efficient than the direct excitation of lanthanide ions. Moreover, multiple sites of Eu3+ as well as the host-to-Eu3+ energy transfer were also revealed based on the PL analyses.     

Y2O2S:0.03Eu,0.03Ti的长余辉特性及Ti向Eu3+的余辉传能机制

采用高温还原法合成了Eu，Ti共激活橙红色Y2O2S长余辉发光材料，并测量了Y2O2S：0．03Eu,0．03Ti磷光体的荧光光谱，余辉分辨和余辉衰减曲线谱．实验结果表明，Y2O2S：0．03Eu,0．03Ti磷光体的发射谱由一系列Eu^3＋离子内部能级跃迁的尖峰组成；余辉分辨谱则不同，由一个主峰位于565nm的宽发射带和一系列波长范围位于500nm以上的窄发射带两种峰形组成，可分别归为Ti离子的宽带余辉发射和三价Eu^3＋的线状余辉发射,分析认为，样品中存在Ti余辉发射向Eu^3＋内部能级间产生选择性的余辉传能机制，从而导致Y2O2S：0．03Ti，0．03Eu磷光体中同时出现两种发光中心离子的余辉分辨谱现象．     

紫外线辐照下BaFCl：Eu^2＋的电子转移过程

本文研究了BaF_xCl_(2-x):Eu~(2+)荧光材料在紫外线辐照下的光激励发光。在小于Eu~(2+)离化能而大于Eu~(2+)最低激发态的不同能量紫外线辐照后(Eex.相似文献   

Synthesis and optical properties of KCaPO4:Eu phosphor

A series of Eu²⁺ doped KCaPO₄ phosphors were prepared by high temperature solid state reaction and an efficient blue-green emission was observed. The photoluminescence (PL) spectrum of the phosphor appeared one asymmetric peak under near-ultraviolet (n-UV) excitation and two emission bands at 480 nm and 540 nm were obtained using Gaussian fit, which was because Eu²⁺ ions inhabited two different Ca²⁺ sites: Eu(I) and Eu(II) in the host lattice, respectively. The excitation spectrum was a broadband extending from 250 to 450 nm, which matched well with the emission of ultraviolet light-emitting diodes (UV LEDs). The effect of Eu²⁺ concentration on the emission intensity of KCaPO₄:Eu²⁺ phosphor was investigated in detail.     

Preparation and luminescence properties of LaMgAl11O19:Eu3+ phosphor powder

LaMgAl11O19, is a kind of rare earth aluminate with the hexagonal structure, which has been used as a host material for the luminescence of various rare earth and magnet-like ions. LaMgAl11O19:Eu3+ phosphors have been prepared through the one-pot method. X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA) and photoluminescence spectra were used to characterize the resulting phosphors. The results of XRD indicated that the phosphors crystallized completely at 1,400 degrees C. In LaMgAl11O19:Eu3+ phosphors, the Eu3+ shows its characteristic red emission at 615 nm (5D0-7F2) upon excitation into 404 nm, with an optimum doping concentration of 15 mol% of La3+ in the host lattices.     

Sol-gel synthesis and luminescence property of ZnO:(La,Eu)Cl nanocomposite thin films

A kind of ZnO:(La, Eu)Cl nanocomposite thin film phosphor with strong red emission was synthesized by the sol-gel process. X-ray diffraction and scanning electron microscopy characterization indicate that the films were composed of nano-sized grains and a LaOCl phase appeared accompanying with (100) oriented ZnO phase after annealed at 600 °C in oxygen. The photoluminescence properties were investigated by measuring the excitation and emission spectra. These luminescence results suggested that Eu³⁺ ions could incorporate into the LaOCl lattice and charge transfer occurred between LaOCl phase and Eu³⁺ ions. La co-doping with Eu-Cl leads to the improvement of the red luminescence of Eu³⁺ and also suppressed the broad green emission of ZnO host.     

Eu3+掺杂β-NaYF4∶20%Yb3+, 0.5%Tm3+的合成与双频光转换性能

采用高温溶剂热法合成了Eu3+掺杂的双频转换发光材料β-NaYF4∶20%Yb3+,0.5%Tm3+,并使用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)和光致发光谱(PL)仪对所制备样品的物相结构、形貌特征和发光性质进行了表征,通过分析发光原理,解释了上、下转换发光的竞争机制,并探讨了稀土离子Tm3+与Eu3+之间的能量转移。结果表明:所合成的β-NaYF4∶20%Yb3+,0.5%Tm3+,xEu3+为纯六方相晶体,结晶良好,颗粒尺寸在200nm左右。改变Eu3+的掺杂浓度后晶格结构没有发生明显变化,样品可在394nm和980nm光的激发下,分别发生下转换和上转换发光。     

Photoluminescence properties of red emitting BaGdB9O16:Eu phosphor

An investigation is reported of the photoluminescence properties of the BaGdB₉O₁₆:Eu phosphors. Under VUV excitation, BaGdB₉O₁₆:Eu exhibited a bright red luminescence with CIE chromaticity coordinates of (0.66, 0.34). The brightness was 80% of the commercial (Y,Gd)BO₃:Eu under identical excitation conditions. The PL spectrum showed a low field splitting of the ⁷F_J levels of Eu, indicating the Eu ions experience local distortion. It also showed a vibrational mode associated with the Eu-O vibration. The physical mechanism responsible for Eu excitation was investigated by PLE and time-resolved spectroscopy. The PLE spectrum showed sharp lines due to the ⁸S_7/2 – ⁶I_J and ⁶P_J transitions of Gd³⁺ in addition to the f-f transitions of Eu³⁺. The charge transfer band of Eu was observed at 233 nm and the host absorption band was detected at 159 nm. The time-resolved spectroscopy showed that the Eu ions decay purely exponentially with a lifetime of 2.1 ms. Under excitation into the Gd ⁶I_J level located below the fundamental absorption edge, the Eu luminescence was excited through the energy transfer process from Gd to Eu. The energy transfer rate was estimated to be 6000 s^–1.     

Efficient doping and energy transfer from ZnO to Eu3+ ions in Eu(3+)-doped ZnO nanocrystals

Successful doping of Eu3+ ions into ZnO nanocrystals has been realized by using a low temperature wet chemical doping technique. The substitution of Eu3+ for Zn2+ is shown to be dominant in the Eu-doped ZnO nanocrystals by analyzing the X-ray diffraction patterns, transmission electron microscopy images, Raman and selectively excited photoluminescence spectra. Measurement of the luminescence from the samples shows that the excited ZnO transfers the excited energy efficiently to the doped Eu3+ ions, giving rise to efficient emission at red spectral region. The red emission quantum yield is measured to be 31% at room temperature. The temperature dependence of photoluminescence and the photoluminescence excitation spectra have also been investigated, showing strong energy coupling between the ZnO host and Eu3+ ions through free and bound excitons. The result indicates that Eu3+ ion-doped ZnO nanocrystals are promising light-conversion materials and have potential application in highly distinguishable emissive flat panel display and LED backlights.     

Structure, charge transfer bands and photoluminescence of nanocrystals tetragonal and monoclinic ZrO2:Eu

Eu(3+)-doped tetragonal and monoclinic ZrO2 (called t-ZrO2:Eu and m-ZrO2:Eu, respectively) nanoparticles were prepared using the Pechini sol-gel process. The samples were characterized via X-ray diffraction (XRD) and field-emission-scanning electron microscopy (FE-SEM), and with photoluminescence spectra. The influences of the Eu3+ concentration and the fired temperature on the crystal phase composition of the tetragonal and monoclinic ZrO2:Eu were reported. The typical interesting photoluminescence (PL) properties of the t-ZrO2:Eu and m-ZrO2:Eu nanoparticles were presented. In the t-ZrO2:Eu and m-ZrO2:Eu, the main emission peaks were at 607 and 615 nm, respectively, both of which originated from the 5D0-7F2 transition. The excitation band of the t-ZrO2:Eu powder with a lower Eu3+ doping concentration that was obtained at a low temperature (450 degrees C) consisted of a broad band of 230-500 nm. Both broad excitation bands in the t-ZrO2:Eu and m-ZrO2:Eu were ascribed to the O(2-) - Eu3+ charge transfer (CT) transition. The reason was discussed based on the relationship between the CT energy and its crystal structure. The CT energy of m-ZrO2:Eu is higher than that of t-ZrO2:Eu. A detailed chemical bond analysis was performed to explore the CT energy difference between t-ZrO2: Eu and m-ZrO2:Eu.