The Luminescence Properties and Intramolecular Energy Transfer of Rare Earth Complexes with Aromatic Carboxylic Acids

The triplet state energies of para aminobenzoic acid and nicotinic acid were determined by means of low temperature phosphorescence spectrometry.The energy matches between them and the resonant emitting energy levels of Eu^(3+),Tb^(3+),Sm^(3+),Dy^(3+)were studied.The intramolecular energy transfer processes from the two aromatic carboxylic acid ligands to rare earth ions were also discussed on the basis of the measurement results of luminescence intensities,lifetimes and quantum efficiencies.

Photoluminescence and Energy Transfer Process in Bi³⁺/Sm³⁺Co-Doped Phosphate Zinc Lithium Glasses

Present paper reports on luminescence characteristics of individually doped Bi3+: PZL, Sm3+: PZL and co-doped (Bi3+/Sm3+): PZL (50P2O5-30ZnO-20LiF) glasses prepared by a melt quenching method. The results revealed that Bi3+: PZL glass exhibited a broad emission peak at 440 nm (3P1→1S0) under excitation wavelength 300 nm (1S0→3P1). Sm3+: PZL doped glass has shown a prominent orange emission at 601 nm (4G5/2→6H7/2) with an excitation wavelength 403 nm (6H5/2→4F7/2). Later on Bi3+ is added to Sm3+: PZL glass by increasing its concentrations from 0.1 - 1.5 mol%. By co-doping Bi3+ to Sm3+: PZL glass, Sm3+ emission intensity has been considerably enhanced till 1.0 mol% due to energy transfer from Bi3+ to Sm3+ and when its concentration exceeds this critical value (1.0 mol%) there has been a drastic decrease in Sm3+ emission which is explained accordingly from photoluminescence spectra, energy level diagram and lifetime measurements.

Luminescence Properties of Eu^(2+) and Mn^(2+) Co-Doped Ca_8Mg(SiO_4)_4Cl_2

The green phosphor for white LED, Ca 8Mg(SiO 4) 4Cl 2∶Eu 2+, Mn 2+, was synthesized by high temperature solid state reaction under reducing atmosphere. During the process of the phosphor prepared, the excess CaCl 2 can improve the intensity of emission. The experimental results indicate that there is an effective energy transfer from Eu 2+ to Mn 2+in Ca 8Mg(SiO 4) 4Cl 2 host. This kind of energy transfer may be due to resonance transfer, and this energy transfer is limited.

Site Selective Excitation and Energy Transfer in LiKGdF_5 Crystal Co-doped with Er^(3+) and Tb (3+)

Crystals of LiKGdF 5∶Er 3+, Tb 3+ grown by the hydrothermal synthesis technique with concentrations of 2% and 0.4% were analysed. By using site selective excitation measured at low temperature, luminescence and excitation spectra from Er 3+ and Tb 3+ ions embedded in LiKGdF 5 were clearly separated. The lifetimes of the emitting levels 4S 3/2 of Er 3+ and 5D 4 of Tb 3+ were also determined. Following the site selective spectroscopy study, the dominant energy transfer process from Tb 3+ to Er 3+ in the crystal was then investigated via transient experiments.

高性能YVO_(4)基稀土杂化发光材料的构建及其能量传递机制

采用溶剂热和离子交换两步实验法,以YVO_(4)为无机基质,2-噻吩甲酰三氟丙酮(TTA)为有机配体,构建了具有核壳结构的YVO_(4)∶Eu^(3+)@YVO_(4)∶Eu^(3+)-TTA稀土杂化发光材料,研究了其高效的发光性能和内部的能量传递机制。结果表明,在621nm的监控波长下,YVO_(4)∶Eu^(3+)@YVO_(4)∶Eu^(3+)-TTA稀土杂化发光材料在280~420nm范围内有两个很强的吸收峰(即V-O峰和TTA特征吸收峰)。YVO_(4)基质通过交换作用能量传递,而TTA有机配体通过分子内能量传递,可将吸收的紫外光能量有效地传递给Eu^(3+),从而实现了Eu^(3+)更高效的可见光(红光)发射。

Luminescence properties and energy transfer of host sensitized CaMoO_4:Tb^(3+) green phosphors

A series of CaMoO4：xTb3＋ （x=0.01, 0.03, 0.05, 0.07, 0.09, 0.15 and 0.20） phosphors in pure phase were prepared via high temperature solid-state reaction approach. The crystal structure of the phosphors was investigated by X-ray diffraction （XRD）, and the optical properties were investigated by Fourier transform infrared spectroscopy （FT-IR）, ultraviolet-visible spectroscopy （UV-Vis） and photoluminescence （PL） spectroscopy. The PL spectra illustrated that these phosphors could be efficiently excited by the charge transfer band of the host and the energy transfer efficiency from the host to the doped activator reached 60% when the doping con- centration of the activator Th3＋ was 20 mol.%. The concentration quenching occurred at x= 10 mol.%, from which the critical distance of activator was calculated to be about 1.14 nm. The CIE coordinates were estimated to be close to the standard green value. The host sensitized samples had potential application as green phosphors.

新型红色荧光粉Sr_(3)CaNb_(2)O_(9):Sm^(3+),Eu^(3+)的发光特性和能量传递分析

利用高温固相反应法制备一系列单基质荧光粉Sr_(3)CaNb_(2)O_(9):xSm^(3+),yEu^(3+)(x=0.04~0.09,y=0.03~0.15),并对样品的物相形貌、发光性能、能量传递机制和CIE色坐标进行分析。研究表明,Sr_(3)CaNb_(2)O_(9):xSm^(3+)荧光粉在激发波长为407 nm时的浓度淬灭点为x=0.07。在Sr_(3)CaNb_(2)O_(9):0.07Sm^(3+),yEu^(3+)荧光粉中,随着Eu^(3+)掺杂浓度的增加,Sm^(3+)的发光强度降低而Eu^(3+)发光强度却先增加后降低,Eu^(3+)的浓度淬灭点为y=0.09。Sm^(3+)→Eu^(3+)的能量传递以电偶极-电偶极相互作用为主,能量传递效率达到76.6%。色坐标图表明Eu^(3+)离子的加入可使色坐标从橙红色区域向纯红色区域移动。此外,样品还具有较高的色纯度和较低的色温。结果表明,Sr_(3)CaNb_(2)O_(9)∶Sm^(3+),Eu^(3+)荧光粉有望成为白光LED发出红光物质的候选材料。

Photoluminescent properties of LaF_3:Eu^(3+) and GdF_3:Eu^(3+)nanoparticles prepared by co-precipitation method

GdF3：Eu^3＋ and GdF3：Eu^3＋ nanoparticles were prepared by a co-precipitation method in the presence of the chelating agent, citric acid. The structural properties of the products were characterized by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The average crystallite size was estimated from the full-width at half-maximum （FWHM） of the diffraction peaks by the Scherrer equation. The sizes of the nanoparticles were 12 nm for LaF3：Eu3＋ and 17 nm for GdF3：Eu^3＋. The luminescent properties of the nanoparticles were investigated by excitation and emission spectra. Energy transfer from Gd3＋ to Eu3＋ was observed.

Luminescent properties and energy transfer mechanism from Tb^(3+) to Eu^(3+) in CaMoO_4:Tb^(3+),Eu^(3+) phosphors

A series of CaMoO_4：Tb^（3＋）,Eu^（3＋） phosphors were prepared by the method of precipitation. The structure and morphology of the phosphors were characterized by the X-ray diffraction（XRD） and field emission scanning electron microscopy（FE-SEM）. The photoluminescence properties of the prepared products were researched, and the energy transfer from Tb^（3＋） to Eu^（3＋） in CaMoO_4 phosphors was studied. By adjusting the doping concentration of Eu^（3＋） ions in CaMoO_4：Tb^（3＋）,Eu^（3＋） phosphors, the emitting color of the phosphors could be easily tuned from green to red. With Tb^（3＋） doped in the phosphors, the red luminescence of Eu^（3＋） by near UV excitation was significantly enhanced. The energy transfer efficiency, rate and average distance between Tb^（3＋） and Eu^（3＋） in CaMoO_4：5%Tb^（3＋）,x%Eu^（3＋）（mole percent） phosphors（x=0.3-10） were calculated. It was found that the interaction type between Tb^（3＋） and Eu^（3＋） was electric dipole-dipole interaction in the phosphors.

Tb^(3+) concentration dependent optical properties and energy transfer in GdF_3 nanocrystals

By controlling the concentration of Tb3＋, a series of GdF3 samples were synthesized by a hydrothermal method without any surfactant. The samples were characterized by X-ray diffraction （XRD） patterns, field emission scanning electron microscopy （FE-SEM） images, photoluminescence （PL） excitation and emission spectra as well as luminescent dynamic decay curves. The opti-cal properties of Tb3＋, the concentration quenching phenomenon of Tb3＋, and the energy transfer from host Gd3＋to Tb3＋were inves-tigated and discussed based on the concentration of Tb3＋in the GdF3 samples. The experimental results suggested that the optical properties of Tb3＋and the energy transfer from host Gd3＋to Tb3＋could be adjusted by the concentration of Tb3＋in the samples.

Synthesis,optical properties,and energy transfer of Ce^3＋,Tb^3＋ doped KLu2F7

Ce^3＋, Tb^3＋ doped orthorhombic phases of KLu2F7 microcrystals with hexagonal disk morphology were synthesized by a hydrothermal method. Enhanced emissions of Tb^3＋ were observed in the Ce^3＋,Tb^3＋ co-doped KLu2F7 sample compared to the Tb^3＋ single-doped KLu2F7. The energy transfer efficiency from Ce^3＋ to Tb^3＋ was calculated by the photoluminescence intensity in the Ce^3＋,Tb^3＋ co-doped KLu2F7 samples. The average separations between Ce^3＋ and Tb^3＋ were calculated and the critical distance was 0.922 nm estimated by method of concentration quenching. The theoretical calculation proved the results. The theoretical analysis also suggested that the energy transfer from Ce^3＋ to Tb^3＋ in the KLu2F7 occurred predominantly via the dipole-quadrupole interaction. The KLu2F7 should be good host materials for emitters.

Luminescent properties and energy transfer of color-tunable Sr_3Y_2(SiO_3)_6:Ce^(3+),Tb^(3+) phosphors

Phosphors with controlled emission spectra are of great interest due to their application for white light emitting diodes.Herein, a new class of Sr3Y2（SiO3）6：Ce3＋,Tb3＋ phosphors were synthesized by a facile sol-gel combustion method. The phase structure,morphology, and luminescence properties of the phosphors were characterized by using powder X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, and photoluminescence excitation and emission spectra,respectively. The results on luminescence properties indicated that co-doped Ce3＋ ions served as UV-light sensitizers with excitation energy partially transferred to Tb3＋ ions, leading to green emission from Tb3＋. Particularly, the corresponding emitting colors of the phosphors could be well-tuned from deep blue（0.16, 0.05） to green region（0.25, 0.45） by adjusting the molar ratio of Ce3＋/Tb3＋.

Investigation of 2.9 μm luminescence properties and energy transfer in Tm^(3+)/Dy^(3+) co-doped chalcohalide glasses

A series of chalcohalide glasses based on the composition of 0.9（Ge30Ga5Se65）-0.1CsI with different Tm3＋/Dy3＋-codoped ions concentrations were synthesized by melt-quenching technique.The absorption spectra and 2.9 μm mid-infrared fluorescence spectra of glass samples under 800 nm laser excitation were measured.The results showed that Tm3＋ was an efficient sensitizer,which could enhance the Dy3＋： 2.9 μm fluorescence intensity significantly.The effective energy transfer between the two rare-earth ions were mainly attributed to the resonance energy transfer from Tm3＋：3F4 to Dy3＋：6H11/2 level.Emission cross section of 2.9 μm mid-infrared luminescence was also investigated according to Judd-Ofelt theory,σe=2.51×10–20 cm2.

Zr_(0.3)Sc_(1.7)Mo_(2.7)V_(0.3)O_(12):Yb^(3+)/Er^(3+)的发光实验设计及性能研究

基于结构单元共取代的方案,通过Zr^(4+)-V^(5+)离子对部分取代Sc_(2)Mo_(3)O_(12)中的Sc^(3+)-Mo^(6+)单元,采用水热法制备出Yb^(3+)/Er^(3+)掺杂的新型钼酸盐氧化物Zr_(0.3)Sc_(1.7)Mo_(2.7)V_(0.3)O_(12)。通过X射线衍射表征结合精修计算,详细分析了取代前后样品的晶体结构和晶胞参数;在980 nm激光激发下,结构单元共取代后样品发射出强烈的上转换绿光,来源于Er^(3+)离子的^(2)H_(11/2)→^(4)I_(15/2)以及^(4)S_(3/2)→^(4)I_(15/2)跃迁,其发光强度提高了120倍左右;通过发光强度与能量密度的关系分析了Yb^(3+)-Er^(3+)离子间上转换发光机制和能量传递过程;基于Er^(3+)热耦合能级的荧光强度比技术,发现阳离子取代后样品的测温灵敏度提高了3倍左右,在533 K时获得了高达0.01525 K^(-1)的最大绝对灵敏度。

Structure and luminescence properties of color-tunable phosphor Sr_(2)La_(3)(SiO_(4))_(3)F:Tb^(3+),Sm^(3+)

A series of single-phase and color-tunable phosphors Sr_(2)La_(3)(SiO_(4))_(3)F:0.15Tb^(3+),xSm^(3+)(SLSOF:0.15Tb^(3+),xSm^(3+)) was prepared using solid-state route.The X-ray diffraction(XRD) was used to characterize the phase of the as-prepared samples.The synthesized phosphors have apatite-type structure without other impurities.Sm^(3+) and Tb^(3+) ions substitute La^(3+) into the lattice and form a single-phase solid solution.The elements are evenly distributed in the sample according to the scanning electron microscopy(SEM) results.The crystal structure of the host phosphor was refined by the Rietveld method.The optical properties were studied in detail by investigation of the luminescence and diffuse spectra,fluorescence decay curves and energy transfer efficiency.The phosphor color can be changed from green(0.29,0.48) to yellow/orange and red(0.57,0.42) via adjusting the doping ratio of Sm^(3+).The SLSOF:0.15Tb^(3+),xSm^(3+)phosphors can emit typical multicolor light such as green,yellow,orange and red with gradually increasing Sm^(3+)doping concentration.All results indicate the occurrence of the energy transfer which results in the color-tunable properties of the phosphors.

Synthesis and luminescence properties of apatite-type red-emitting Ba_(2)La_(8)(GeO_(4))_(6)O_(2):Eu^(3+)phosphors

A new kind of apatite-type red-emitting Ba_(2)La_(8)(GeO_(4))_(6)O_(2):Eu^(3+)phosphor was prepared by high temperature solid-state method.The Rietveld analysis based on the powder diffraction data shows that Ba_(2)La_(8)(GeO_(4))_(6)O_(2):Eu^(3+)phosphors possess a pure apatite phase without any impurity.The emission spectrum of Ba_(2)La_(8)(GeO_(4))_(6)O_(2):Eu^(3+)phosphor consists of two bands,an orange emission band from 500 to 600 nm and a red emission band from 600 to 680 nm.By varying the amount of the doped europium ions from 0.02 to 0.14 mol,it is found that the luminescent properties of this rare earth phosphor are the best when the concentration of europium ion is 0.08 mol.The optimum concentration is eventually proved to be 0.08 mol.The Eu^(3+)doping dependent luminescence quenching can be further ascribed to dipole-quadrupole interactions.The quantum yield of Ba_(2)La_(7.92)(GeO_(4))_(6)O_(2):0.08 Eu^(3+)is 37.23%.The CIE analysis confirms a reddish emission in the near ultraviolet(n-UV)excitation.All these above properties of the phosphor can help in contribution of promoting white light-emitting diode.

3.1 μm mid-infrared luminescence in Er^(3+) doped ZnF_(2) modified aluminum fluoride glass

Herein,melt-quenching and Er^(3+) doping were used to synthesize fluoride glass specimens with low phonon energies(582 cm^(-1)).These glass specimens exhibit intense 3.1 μm mid-infrared band emission when they are excited by a 980 nm laser diode,achieving a full width at half maximum(FWHM) of about166 nm.This 3.1 μm emission intensity is enhanced by the introduction of ZnF_(2) to the AlF_(3)-based fluoride glass.Up-conversion emission,strong near-infrared emission,and fluorescence lifetime are enhanced to different degrees by increasing the ZnF_(2) content.Moreover,the spectroscopic characteristics of the glass specimens and the highly efficient Er^(3+):~4S_(3/2)→~4F_(9/2) transition's energy transfer mechanism were investigated.The absorption spectra and emission spectra of these aluminum fluoride glass specimens were used to calculate their gain coefficients and maximum cross sections at 1.5 and 3.1 μm.Overall,the spectral properties of these prepared aluminum fluoride glass specimens demonstrate their high potential for use as infrared laser host materials.

Structural and optical properties of Dy^(3+):YAlO3 phosphors for yellow light-emitting diode applications

The spectroscopic properties of a series of Dy^(3+)single-doped and Dy^(3+)/Nd^(3+),Dy^(3+)/Tb^(3+),and Dy^(3+)/Tm^(3+)co-doped YAlO_(3)(yttrium aluminum perovskite,YAP)phosphors were investigated and compared through the measurements of optical absorption,emission spectra,and fluorescence decay curves.For the Dy^(3+)ion single-doped samples,the intensity of each absorption band increases with an increment in Dy^(3+)ion doping concentration,and the identified strong absorption peak at 447 nm indicates that Dy^(3+):YAP phosphors are suitable to be pumped by a blue laser diode(LD).For all co-doped samples,absorption peaks of Dy^(3+)ion along with some of the absorption bands of Nd^(3+),Tb^(3+),and Tm^(3+)ions are observed.Under 351 and 447 nm excitation,a prominent emission peak at 572 nm was obtained in all the samples,corresponding to Dy^(3+):^(4)F_(9/2)→^(6)H_(13/2)transition.Here,2 at%Dy^(3+):YAP phosphor exhibits the highest yellow emission intensity under 447 nm pumping.Among the three kinds of Dy^(3+)co-doped phosphors,Dy^(3+)/Tb^(3+):YAP phosphor possesses the dominant yellow emission.The fluorescence decay curves show exponential behaviour and are fitted well.The Commission International de L’Eclairage(CIE)chromaticity coordinates were calculated following the respective emission spectra,and it is found that all the coordinates locate in the yellow region.The energy transfer(ET)processes were investigated and the concentration quenching mechanism was discussed.The obtained results suggest that Dy^(3+)-activated YAP phosphors are good candidates for yellow LED applications.

Effect of Eu^3+ contents on structure and luminescence properties of Na3Bi2–x(PO4)3:xEu^3+ and Na3Bi1–x(PO4)2:xEu^3+ phosphors

A series of Na3Bi2–x（PO4）3：xEu3＋ and Na3Bi1–x（PO4）2：xEu3＋phosphors were successfully synthesized by solid-state method. The structure and luminescence properties were carefully investigated. The excitation spectra presented an obvious excitation band, and the peak was located at 396 nm, which matched well with the popular emissions from near-UV light-emitting diode chips. With the phase of Na3Bi2–x（PO4）3：xEu3＋ changing to that of Na3Bi1–x（PO4）2：xEu3＋, the intensity of magnetic dipole transition （5D0→F1） at 598 nm became stronger than that of electric dipole transition （5D0→7F2） at 621 nm. Under 396 nm excitation, the chromaticity coor-dinates and the decay curves of the entitled phosphors were also investigated. Based on all experiments without concentration quenching, we could control the luminescence intensity of the material by adjusting the doping amount of the active ions. All results indicated thatNa3Bi2–x（PO4）3：xEu3＋ and Na3Bi1–x（PO4）2：xEu3＋ phosphors have potential application as red phosphors in near UV chip-based white light emitting diodes.

A single-phase full-color phosphor Sr_(2)Ca_(2)La(PO_(4))_(3)O:Eu^(2+),Tb^(3+),Mn^(2+):Photoluminescence and energy transfer

A single-phase full-color emitting phosphor Sr_(2)Ca_(2)La(PO_(4))_(3)O:Eu^(2+),Tb^(3+),Mn^(2+) was synthesized by the high temperature solid-state method.The phase formation,luminescence properties,thermal stability,and energy transfer from Eu^(2+)to Tb^(3+) and Eu^(2+)to Mn^(2+) in Sr_(2)Ca_(2)La(PO_(4))_(3)O were investigated in details.Tunable emission color from blue to blueish green or orange can be observed under 365 nm near-ultraviolet excitation based on the energy transfer from Eu^(2+) to Tb^(3+)or Mn^(2+) ions by varying the ratio of Eu^(2+)/Tb^(3+)or Eu^(2+)/Mn^(2+) ions.White light was obtained with chromaticity coordinates of(0.3558,0.3500)in the Sr_(2)Ca_(2)La(PO_(4))_(3)O:0.04Eu^(2+),0.08Tb^(3+),0.40Mn^(2+) phosphor,suggesting their potential applications in white light emitting diodes.