Synthesis and properties of the TTA/Gd2O3: Eu3+ luminescent system

Journal of Sol-Gel Science and Technology - Hybrid materials based on lanthanide ions or lanthanide-doped nanostructured particles have received a lot of recent attention because organic ligands...     

Eu3+ concentration dependent optical properties and energy transfer from host Gd3+ to Eu3+ in GdF3 nanocrystals

By using a hydrothermal method, a series of Eu³⁺ concentration dependent GdF₃ nanocrystals have been synthesized. The crystalline structures of samples are characterized by XRD patterns, the morphology and size of the samples are illustrated by FE-SEM images, and the optical properties of the samples are presented by PL excitation and emission spectra. The energy transfer from host Gd³⁺ to Eu³⁺ is observed in the Eu³⁺ doped GdF₃ nanocrystals. The optical properties of Eu³⁺ and the energy transfer efficiency from host Gd³⁺ to Eu³⁺ are discussed on the basis of the Eu³⁺ concentration dependent integrated PL excitation and emission spectra of Gd³⁺ and Eu³⁺. The discussion on optical properties of Eu³⁺ and the energy transfer from Gd³⁺ to Eu³⁺ is meaningful to design and synthesize Gd³⁺ based compounds.     

Synthesis and properties of europium-based phosphors on the nanometer scale: Eu2O3, Gd2O3:Eu, and Y2O3:Eu

Nanocrystals of oxides containing europium as the main constituent or as a doping element in RE2O3 ( RE=Y, Gd) have been prepared by direct oxide precipitation in high-boiling polyalcohol solutions and characterized by high-resolution TEM, absorption spectroscopy, and luminescence spectroscopy. The samples obtained consisted of concentrated and colloidally stable suspensions of luminescent oxide nanoparticles with an average grain diameter in the range 2-5 nm. The nanoparticles were found to be highly crystalline despite their ultrasmall size and the low temperature of 180 degrees C applied during the synthesis. Upon UV excitation, the red luminescence relative to the 5D0-->7Fn transition within the cubic form of RE2O3 exhibits some important differences from that usually found in bulk materials.     

核壳型Gd2O3:Eu3+@Y2O3纳米发光材料的制备与发光性能

采用均相沉淀法制备了均匀球形的Gd2O3:Eu3+@Y2O3核壳结构纳米发光材料.XRD结果表明经过800℃焙烧后样品为立方晶系的Gd2O3,并且晶体发育良好,包覆Y2O3之后Gd2O3的衍射峰位置无明显变化,但随着包覆厚度的增加,出现了立方晶系Y2O3的衍射峰.FTIR谱图观测到了Gd-O,Y-O伸缩振动吸收峰,随着包覆厚度的减少吸收峰增强,认为当包覆层的厚度适当时,颗粒表面的悬空键(断键)变少,Gd(Eu,Y)-O键增多所致.SEM表明包覆前后样品为均匀分散的球形结构.XPS分析进一步证明了表面包覆上了Y2O3.荧光光谱表明:纳米Gd2O3:Eu3+表面包覆不同厚度的基质Y2O3后,均观测到Eu3+离子的特征红光发射,当包覆厚度R=4:1时的发光强度比未包覆的Gd2O3:Eu3+增强,认为核-壳型样品降低了纳米Gd2O3:Eu3+的表面效应给发光强度带来的负面影响.     

Novel dumbbell-like LaVO4:Eu3+ nanocrystals and effect of Ba2+ codoping on luminescence properties of LaVO4:Eu3+ nanocrystals

Journal of Sol-Gel Science and Technology - LaVO4:Eu3+ nanocrystals with different morphologies were synthesized via a simple hydrothermal method in a wide pH range. The as-synthesized samples were...     

Electronic polarizability and Judd-Ofelt parameters of Nd3+ and Er3+ ions in transparent crystallized glasses with nonlinear optical Ba2 TiSi2O8 nanocrystals

Transparent crystallized glasses consisting of nonlinear optical Ba(2)TiSi(2)O(8) nanocrystals are prepared in Eu(2)O(3)-, Nd(2)O(3)-, and Er(2)O(3)-doped 40BaO-20TiO(2)-40SiO(2) glasses by a conventional heat treatment method in order to clarify the optical properties of rare-earth (RE) ions in nanocrystals. The electronic polarizabilities of crystallized glasses are evaluated from the values of density and refractive index, and are found to decrease due to nanocrystallization, which indicates that the chemical bonding state in the crystallized glasses is more covalent compared to the precursor glasses. It is proposed from x-ray diffraction analyses and photoluminescence spectra of Eu(3+) ions that RE ions such as Nd(3+) and Eu(3+) are incorporated into Ba(2)TiSi(2)O(8) nanocrystals. The Judd-Ofelt parameters, Omega(t) (t=2, 4, and 6), of Nd(3+) and Er(3+) ions are evaluated from optical absorption spectra. It is observed that the Omega(2) parameter of Nd(3+) and Er(3+) increases largely due to nanocrystallization, suggesting that the site symmetry of Nd(3+) and Er(3+) ions in nanocrystallized glasses is largely distorted due to their incorporations into the Ba(2+) sites in Ba(2)TiSi(2)O(8) nanocrystals. The change in the Omega(4) and Omega(6) parameters due to nanocrystallization is small. It is proposed that nonlinear optical Ba(2)TiSi(2)O(8) nanocrystals including RE ions would have a high potential as active optical materials.     

Preparation and photoluminescence properties of Y2SiO5:Eu3+ nanocrystals

The sol-emulsion-gel method is used for the preparation of about 5-7 nm size Eu2O3 doped and coated Y2SiO5 nanoparticles at 1300 degrees C. Here, we report the role of surface coating, dopant concentration and temperature of heating on the modification of crystal structure and the photoluminescence properties of Y2SiO5:Eu3+ nanocrystals. It is found that photoluminescence properties are sensitive to the crystal structure which is again controlled by surface coating, concentration and heating temperature. The decay times are 0.76, 1.14, 1.23 and 1.40 ms for 0.25, 0.5, 1.0 and 2.5 mol% Eu2O3 doped Y2SiO5 nanocrystals prepared at 1100 degrees C (X1-Y2SiO5). However, in X2-Y2SiO5 crystal phase (at 1300 degrees C) the average decay times are 1.05, 1.35, 1.55 and 1.60 ms for 0.25, 0.5, 1.0 and 2.5 mol% Eu2O3 doped Y2SiO5 nanocrystals, indicating the photoluminescence properties depend on both the crystal structure and the concentration of ions. The emission intensity of the peak at 612 nm (5D0-->7F2) of the Eu3+-ions is found to be sensitive to the doping and surface coating of Y2SiO5 nanocrystals. The decay times are 1.55 and 1.70 ms for 1300 degrees C heated 1.0 mol% Eu2O3 doped and coated Y2SiO5 nanocrystals, respectively. Our analysis suggests that the site symmetry of ions plays a most important role in the modification of radiative relaxation mechanisms and as a result on the overall photoluminescence properties.     

Photoluminescence properties and analysis of spectral structure of Eu3+-doped SrY2O4

The aim of this work is to report on the luminescence properties of SrY2O4 activated by Eu3+ ion. Powder samples were prepared by solid-state reaction. X-ray diffraction powder data, photoluminescence, and high-resolution spectroscopy were carried out. Results revealed that the Eu3+ ions occupied three nonequivalent sites, with one at the Sr site, one at the Y(1) site, and another at the Y(2) site. Their spectra wavelengths for the 7F0-5D0 transition are located at 578.49, 581.86, and 580.63 nm, respectively. The corresponding charge-transfer transitions are located at 248, 257, and 270 nm, respectively, which are also confirmed by theoretical analysis.     

Li+,Zn2+共掺杂对Gd2O3:Eu3+纳米粉结构和发光性能的影响

采用燃烧法制备出Li^＋,Zn^2＋掺杂的Gd2O3：Eu^3＋纳米荧光粉,研究了掺杂离子对Gd2O3：Eu^3＋的结晶性能、晶粒形貌和光致发光特性的影响.以X射线衍射（XRD）、透射电子显微镜（TEM）、发射光谱和衰减时间谱等手段表征材料性能.结果表明,Li^＋,Zn^2＋掺杂可显著提高Gd2O3：Eu^3＋纳米粉在611 nm处的发光强度,最大可达到未掺杂时的2.5倍.发光增强的主要原因可归结为3个方面： （1）使晶粒由单斜相向更利于发光的立方相转变; （2）氧空位的敏化剂作用; （3）掺杂离子的助熔剂效应,使晶粒的结晶性能提高、粒径增大,从而降低表面态引起的发光猝灭.     

BaLiF3∶Eu,Gd中Gd3+→Eu2+的能量传递

研究了BaLiF3中Gd3+和Eu2+的光谱性质及Gd3+对Eu2+的能量传递过程,讨论了传递机理.Gd3+的含量(物质的量分数)为0.3%时,传递效率最高,传递几率PSA＝1.35×105 s-1.当Gd3+的含量高于0.3%时,由于Gd3+和Eu2+竞争吸收Gd3+占优势,增加Gd3+含量,竞争吸收比相应增加,Eu2+自身吸收光子数目减少,发射强度降低.     

痕量双掺Sm3+和Gd3+对Y2O2S:Eu3+发光特性的影响

通过对Y2O2SEu3+红色荧光粉痕量引入Sm3+和Gd3+的研究, 发现可有效地增强发光强度, 明显改善其电压特性(发射强度与激发电压间的关系特性), 且不影响材料的其他物理化学性能. 讨论和分析了发射强度增强、电压特性改善的原因 Gd3+对Y3+的置换, 减少了因Eu3+对Y3+置换所引起的晶格的畸变、缺陷, 使Eu3+离子晶场环境得到改善, 从而减弱了无辐射过程及因晶格畸变所造成的能量损失;Sm3+的发射与Eu3+的吸收(激发)的部分重叠, 且Eu3+激发光谱中包含有Sm3+激发跃迁谱线, 导致了Sm3+→Eu3+共振能量传递可能性, 有效地实现Sm3+对Eu3+的敏化效应.     

Gd2O3:Eu3+ X射线溶胶-凝胶发光薄膜的制备与表征

高分辨率X射线成像系统要求其发光材料同时具有X射线截止本领强、光产额高、余辉短以及与光电器件波长匹配好等特性. Gd2O3:Eu3 因其优越的发光性能和Eu3 红光发射等优点而在高能射线激发发光材料中占有重要地位. 近几年发展起来的透明X射线薄膜发光材料具有更高的衬度和空间分辨率、热传导率、均匀性和附着力等优点[1], 因而有望成为取代传统荧光粉的新一代X射线成像材料. 在各种薄膜制备工艺中, 溶胶-凝胶法以其价格低廉、工艺简单、制备温度低、均匀性好、可实现微量掺杂等优点而日益受到人们重视, 通过该方法并辅以适当的后处理工艺可制备出透明、致密的薄膜.     

Synthesis and optical properties of Gd2O3:Pr3+ phosphor particles

Spherical-shaped Gd₂O₃:Pr³⁺ phosphor particles were prepared with different concentrations of Pr³⁺ using the urea homogeneous precipitation method. The resulting Gd₂O₃:Pr³⁺ phosphor particles were characterized by X-ray diffraction, field emission scanning electron microscope, and photoluminescence spectroscopy. The effects of the Pr³⁺ doping concentration on the luminescent properties of Gd₂O₃:Pr³⁺ phosphors were investigated. Photoluminescence measurements revealed the Gd₂O₃:1?% Pr³⁺ phosphor particles to have the strongest emission. The luminescence properties of Gd₂O₃:Pr³⁺ particles are strongly affected by the phosphor crystallinity and X-ray diffraction measurements confirmed that the crystallinity of Gd₂O₃ cubic structure could be enhanced by increasing the firing temperature. The luminescent Gd₂O₃:Pr³⁺ phosphor particles have potential applications in areas, such as optical display systems, lamps and etc.     

APTES-modified RE2O3:Eu3+ luminescent beads: structure and properties

Europium-doped lanthanide oxide RE(2)O(3):Eu(3+) (RE = Y or Gd) luminescent beads, with a spherical shape and a diameter of 150 ± 15 nm, have been modified by reaction with 3-aminopropyltriethoxysilane (APTES), in order to introduce reactive amine groups at their surfaces. The direct silanation has resulted in the formation of a nanometric layer at the surface of the beads, with an optimum grafting rate of 0.055 ± 0.005 mol APTES/mol RE(2)O(3). Fourier transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies confirmed the condensation of an organosilane layer, made of cross-linked -O-Si-O-Si- and of groups -O-Si-R (with R = (CH(2))(3)NH(2) or O-Et). Titration of the accessible amine groups has been performed by simultaneously measuring the luminescence of grafted fluorescein isothiocyanate and that of core particles: there are about 2.3 × 10(4) (2.8 × 10(4)) -NH(2) per Y(2)O(3):Eu(3+) (Gd(2)O(3):Eu(3+)) bead. The isoelectronic point was shifted by one pH unit after APTES modification. The surface modification by APTES at least preserved (for Gd(2)O(3):Eu(3+)) or improved (for Y(2)O(3):Eu(3+)) the red emission of the beads.     

球形Gd2O3∶Eu纳米发光材料的制备

Spherical nanometer Gd₂O₃∶Eu luminescent materials were prepared by homogeneous precipitation method, and the properties were studied also. TG, FTIR and XRD analysis showed that the precursor was carbonate, the cubic Gd₂O₃was obtained after calcination. TEM photographs indicated that the samples were spherical and well dispersed with nanometer and submicrometer size of 200～300 nm which is the nanoparticles’ aggregate. The mechanics of agglomerating growth is also discussed. ED photograph showed that the particle was crystalline. The PL analysis exhibited that CTB band of nanometer Gd₂O₃∶Eu was of 17 nm red shift to bulk materials, and the emission peak was broadened due to the surface and interface effect of nanocrystals.     

立方Gd2O3∶Eu纳米晶及光谱性质

用透射电镜拍摄球形ＣＧｄ２Ｏ３∶Ｅｕ纳米晶,并研究了室温下它的激发和发射光谱。结果表明,９００℃制备的体材料和相应的纳米晶相比,其激发光谱存在明显差异。前者以基质激发带为主导,电荷转移带（ＣＴＢ）很弱,而后者以ＣＴＢ为主。在绝缘体稀土氧化物中,可以忽略纳米效应对Ｅｕ３＋离子的４ｆ４ｆ能级跃迁的激发和发射光谱峰位的影响     

Thermal study in Eu3+-doped boehmite nanofibers and luminescence properties of the corresponding Eu3+:Al2O3

Eu³⁺-doped boehmite nanofiber materials with different Eu³⁺ concentrations were synthesized without any surfactant, and followed by a series of characterizations. It was found that the boehmite nanofibers became coarser with the increase of Eu³⁺ concentration, which resulted in a gradual decrease of their specific surface areas. Moreover, the thermal stability of the boehmite nanofibers was studied by thermogravimetry–differential scanning calorimetry. All materials showed the phase transition from γ-Al₂O₃ to other forms. Yet the transition temperature was increased with the increase of Eu³⁺ concentration. The Eu³⁺-doped boehmite nanofibers with the maximum Eu³⁺ concentrations showed the best thermal stability. Photoluminescence spectra showed that the 2 mol% of doping concentration of Eu³⁺ ions in Eu³⁺:Al₂O₃ nanofiber was optimum.     

多孔二氧化硅中Gd3+ → Eu3+的能量传递

通过水热反应法，获得了单掺和双掺Eu³⁺，Gd³⁺的多孔二氧化硅组装体，研究了掺杂体系的光谱特性，观察到Gd³⁺ → Eu³⁺的能量传递。分析了能量传递过程，探讨了在多孔二氧化硅中Gd³⁺→Eu³⁺的能量传递的机理，其机理主要为电偶极-电偶极相互作用。     

Effect of thermal annealing on the kinetics of rehydroxylation of Eu3+:La2O3 nanocrystals

Europium-doped lanthanum oxide (5 mol % Eu(3+):La(2)O(3)) was prepared by calcining europium-doped lanthanum hydroxide (5 mol % Eu(3+):La(OH)(3)) previously synthesized by a simple hydrothermal method. Interestingly, we observed different emission Eu(3+) signatures depending on the phase of the host (lanthanum oxide or hydroxide) by cathodoluminescence. Taking into account that lanthanum oxide easily rehydroxylates in air, for the first time, we report the use of cathodoluminiscence as a novel characterization technique to follow the lanthanum oxide rehydroxylation reaction versus time according to different annealing procedures. Additionally, differential thermal-thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques were used to identify the phases formed from the Eu(3+):La(OH)(3) depending on temperature and to study the evolution of La(2)O(3) to La(OH)(3) versus time. The results showed that the higher the temperature and the longer the annealing time, the higher the resistance to rehydroxylation of the Eu(3+):La(2)O(3) sample.