单分散GdxY2-xO3:Eu3+纳米颗粒的制备及其荧光性能

本文采用均相沉淀法制备了单分散Gd_xY_2-xO₃:Eu³⁺纳米颗粒,并利用SEM,TEM,XRD和荧光光谱对产品的形貌,晶体结构和荧光性能进行了表征.结果发现适量Gd³⁺的加入对Y₂O₃:Eu³⁺的发光具有显著的增强作用.同时达到最大荧光强度所需的价格较贵的Gd³⁺用量,也从燃烧法的80%大幅减少到20%.另外,本文还进一步研究了Eu³⁺浓度对纳米颗粒荧光性能的增强效果.     

Eu3+:Y2O3 microspheres and microcubes: a supercritical synthesis and characterization

A new approach that uses mixed supercritical solvents of water/1-propanol and water/methanol (400 °C, 40 MPa) to prepare morphology-controlled precursor materials in a very short reaction time, such as 10 min, followed by calcinations has been developed to form Eu(3+):Y(2)O(3) microspheres of 2-3 μm in diameter or microcubes of 2-3 μm in side length, respectively. Eu(3+):Y(2)O(3) microspheres and microcubes exhibited strong red emission at 610 nm corresponding to (5)D(0) → (7)F(2) transition. The highest photoluminescence emission was obtained for the microspheres after calcination at 1000 °C for 1 h in air.     

Site selection spectroscopy of SiO2:Eu3+ gels

Silica gels doped with Eu³⁺ ions were studied at temperatures between 10 K and 300 K by site selection spectroscopy in samples heated up to 200°C. The ⁵D₀ ⁷F₀ transition shows internal structures due to the different environments of the europium ions. Lifetimes, energy levels and homogeneous linewidths are site dependent. In the wet gel the Eu³⁺ ions prefer a liquid-like environment and only when the liquid is removed by heat treatment, the ion is linked more strongly to the silica network.     

Fabrication and photoluminescence of chemically stable La2O3:Eu3+-La2Sn2O7 core-shell-structured nanoparticles

Core-shell-structured La2O3:Eu3+-La2Sn2O7 nanoparticles were fabricated through SnO2-coating of LaOF:Eu3+ in an aqueous solution and subsequent heat treatments at a higher temperature. The nanoparticles exhibited high chemical stability under an ambient atmosphere and intense red photoluminescence upon irradiation with ultraviolet light.     

Thermoluminescent Properties of Tridymite SiO2 : Al3+, Eu3+

SiO₂ crystals have been used in electroluminescence devices and thermoluminescence (TL) dosimeters. However, their emission mechanisms have not yet been clearly explained. Recently, it has become possible to obtain amorphous, highly pure, SiO₂ prepared by the sol-gel method. The emission mechanism of TL was investigated using Al³⁺ and/or Eu³⁺-doped SiO₂ crystalline samples prepared by heat-treating under much lower temperature than the melting point of SiO₂. The TL spectrum of Eu³⁺-doped sample had main peaks due to the electron transitions from ⁵D₂ to ⁷F₅ (ca. 570 nm, yellow peak) and from ⁵D₀ to ⁷F₂ (ca. 610 nm, red peak). The yellow peak intensity has a maximum value in the SiO₂ doped with near 1 mmol% of Eu₂O₃, while the red peak intensity was almost constant. These facts suggest that bright yellow emission of SiO₂TL phosphor is synthesized by the diffusion of Eu³⁺ ion in SiO₂ matrix prepared by sol-gel method.     

Core-shell structured SiO2@YVO4:Dy3+/Sm3+ phosphor particles: sol-gel preparation and characterization

Spherical SiO(2) particles have been coated with YVO(4):Dy(3+)/Sm(3+) phosphor layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO(2)@YVO(4):Dy(3+)/Sm(3+) particles. X-ray diffraction (XRD), Fourier-transform IR spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting SiO(2)@YVO(4):Dy(3+)/Sm(3+) core-shell phosphors. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 300 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (20 nm for one deposition cycle). The core-shell particles show strong characteristic emission from Dy(3+) for SiO(2)@YVO(4):Dy(3+) and from Sm(3+) for SiO(2)@YVO(4):Sm(3+) due to an efficient energy transfer from YVO(4) host to them. The PL intensity of Dy(3+) and Sm(3+) increases with raising the annealing temperature and the number of coating cycles.     

Sr2SiO4:Eu3+发光材料的制备及其光谱特性

采用溶胶-凝胶法制备了Sr2SiO4:Eu3+发光材料. 测量了Sr2SiO4:Eu3+材料的激发与发射光谱, 发射光谱主峰位于618 nm处;监测618 nm发射峰时, 所得激发光谱主峰分别为320、397、464 和518 nm. 研究了Sr2SiO4:Eu3+材料在618 nm的主发射峰强度随Eu3+浓度的变化情况. 结果显示, 随Eu3+浓度的增大, 发射峰强度先增大; 当Eu3+浓度为7%时(x), 峰值强度最大; 而后随Eu3+浓度的增大, 峰值强度减小. 在Eu3+浓度为7%的情况下, 研究了电荷补偿剂Li+的掺杂浓度(x(Li+))对Sr2SiO4:Eu3+材料发射光谱强度的影响. 结果显示, 随x(Li+)的增大, 材料发射光谱强度先增大后减小, 当x(Li+)为8%时, 峰值强度最大.     

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.     

Energy Transfer Between Eu3+ Ions and CdS Quantum Dots in Sol-Gel Derived CdS/SiO2 : Eu3+ Gel

We have investigated the energetic correlation between rare-earth ions and semiconductor nanocrystals, using europium ion (Eu³⁺) doped silica (SiO₂) gel with adsorbed cadmium sulfide (CdS) particles. Samples were prepared by a sol-gel technique, in which several methods for the precipitation of CdS colloids were attempted. The fluorescence intensities were compared for different gels, with and without CdS particles. The intrinsic emission lines due to ⁵D₀ ⁷F_J(J = 0–4) transitions of Eu³⁺ were observed, which were enhanced for 24 h-immersed gel (dried at 50°C). From the results on the decay dynamics of fluorescence, we proposed the model that surface-trapped electrons on CdS particles nonradiatively excited 4f electrons in Eu³⁺ ions due to an energy transfer process.     

Zn2SiO4基体掺杂稀土离子纳米粉体的制备和光谱特性

采用sol-gel法在Zn2SiO4基体中掺杂稀土离子Eu^3 和Y，制备了Zn2SiO4:Eu及Zn2SiO4:Eu,Y纳米粉体，研究不同稀土离子浓度对荧光强度的影响，并采用热重－差热分析，X射线粉末衍射，荧光光谱分析等技术手段进行表征，目标产物的平均粒径分别为31nm和27nm。     

掺Eu的SiO2-B2O3体系和SiO2-B2O3-Na2O体系的结构及Eu3+的发光性质

采用溶胶-凝胶技术制备了掺Eu3+的以SiO2-B2O3和SiO2-B2O3-Na2O为基质的玻璃态发光材料. 通过激发光谱、发射光谱研究了Eu3+的发光性质, 通过红外光谱、 TEM 、 XRT进一步研究了基质结构变化对发光性能的影响. 结果显示 材料经 600 ℃退火处理后, 结构已十分稳定. 在588 nm和613 nm处显示弱的Eu3+的特征发射光谱, 对应于Eu3+的5D0-7Fj(j=1,2)跃迁. 以SiO2-B2O3为基质的玻璃材料的红外光谱显示形成了Si-O-B键. 该结构对Eu3+的发光有严重的淬灭作用, 使Eu3+的发光强度大大减弱. 以SiO2-B2O3-Na2O为基质的玻璃材料显示Eu3+的发光增强, 红外光谱显示不存在Si-O-B键的振动吸收. 可能是Na取代B的位置, 形成了Si-O-Na键. 此结构对Eu3+的发光有一定增加作用.     

Synthesis and characterization of SiO2/Gd2O3:Eu core-shell luminescent materials

Europium-doped Gd2O3 with an average size of approximately 15 nm was coated on the surface of preformed silica nanospheres by the wet chemical method. SEM and TEM photographs showed that SiO2/Gd2O3:Eu core-shell submicrospheres are obtained. XRD patterns indicated that the Gd2O3:Eu shell is crystalline after heat treatment. FTIR and XPS spectra showed that the Gd2O3:Eu shell is linked to the silica surface by forming a Si-O-Gd bond. Photoluminescence studies showed that the luminescent properties are still retained after coating on an inert silica core; additionally, we noted that the emitting peaks are broadened, which results from size effects and interface effects of nanocrystal.     

Sr3SiO5:Eu2+荧光粉的微波合成及性能研究

0 引 言 白光LED是一种具有广阔前景的节能照明灯具,被誉为人类的第四代照明用灯具.白光LED实现主要有两种方案,其中在蓝光LED芯片上涂覆黄色荧光粉,蓝光芯片发出的蓝光与荧光粉发出的黄光复合而获得白光,受到人们的重点关注[1-5].     

SiO2／LaF3：Eu3＋核壳结构发光粒子的制备与表征

采用简单的液相法合成了SiO2/LaF3:Eu3 核壳结构发光粒子,并对其结构及发光性能进行了表征.XRD分析表明包覆层LaF3:Eu3 为立方晶相结构,红外光谱表明SiO2颗粒表面有柠檬酸的修饰,电镜照片表明合成了球形的核-壳结构的复合粒子,包覆层厚度为10～20 nm,光谱测试表明核-壳复合粒子与纯的LaF3:Eu3 具有相同的发光性能,均以589 nm附近的5D0-7F1磁偶极跃迁为最强发射峰,说明Eu3 在LaF3基质中占据的格位相同.     

Effect of pH on the synthesis and properties of luminescent SiO2/calcium phosphate:Eu3+ core-shell nanoparticles

A novel method for the synthesis of luminescent SiO(2)/calcium phosphate (CaP):Eu(3+) core-shell nanoparticles (NPs) was developed via a sol-gel route followed by annealing at a temperature of 800 °C. The object of this study was the investigation of the effect of pH on the formation of a CaP shell around the silica core. The resulting annealed NPs exhibited an amorphous SiO(2) core and a crystalline luminescent shell. The formation of a CaP layer was possible at pH below 4.5 and above 6.5 during the coating step. The crystal structure of the shell was studied by X-ray diffraction analysis. Hydroxyapatite (HAp) and α-tricalcium phosphate were detected as crystal phases of the surrounding layer. However, NPs produced under basic conditions exhibited a higher crystallinity of the CaP layer than did samples coated at pH below 4.5. In the pH interval between 4.5 and 6.5, no shell growth but the formation of secondary NPs containing CaO and Ca(OH)(2) was observed. Furthermore, SiO(2)/CP:Eu(3+) core-shell NPs were investigated by transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectrometry, and photoluminescence spectroscopy. The resulting HAp-coated NPs were successfully tested by a cell-culture-based viability assay with respect to a later application as a luminescent marker for biomedical applications.     

均分散球形氧化铕超细微粒的制备和表征

采用尿素分解法制备了均分散球形Eu(OH)CO~3·H~2O超细沉淀粒子,进一步在空气中750℃下焙烧4h,得到了均分散球形氧化铕超细微粒。考察了各种反应条件的影响,获得了最佳的制备条件。用XRD,IR,TEM,TG以及比表面测定等手段对样品进行了表征。     

纳米线堆积的铁硅球体催化剂用于费托合成

以共沉淀法所制的工业铁硅球体催化剂(indus-FS)为原料,用改进的有机胺蒸气相传输转化法,得到了负载高分散铁的交织氧化硅纳米线球体催化剂(NW-FS),并用于费托合成反应.在所制纳米线催化剂中,原料催化剂中氧化硅在氧化铁诱导下成功地转变成纳米线交织微球载体,而氧化铁组分则高度分散在氧化硅纳米线上.用扫描电镜、透射电镜、X射线衍射、低温氮吸附、X射线光电子能谱和程序升温还原等方法对所得纳米线催化剂进行了表征.在费托合成中,纳米线铁硅催化剂由于其特殊的堆积结构所导致的低的扩散阻力和高的铁活性组分分散度,提高了低碳烯烃尤其是乙烯的选择性.纳米线铁硅催化剂上低碳产物(C2–C4)的烯烷比为3.3,高于母体工业催化剂的1.9.     

Enhanced luminescence of SiO2:Eu3+ by energy transfer from ZnO nanoparticles

ZnO nanoparticles embedded into SiO(2) by an ex situ method were shown to result in stable green emission with a peak at 510 nm compared to the normal peak at 495 nm from micron-sized ZnO powders. Green emission from ZnO nanoparticles was completely suppressed when they were embedded in SiO2 doped with Eu3+. Instead, the f-f emissions from Eu3+ were enhanced 5-10 times by energy transfer from the embedded ZnO nanoparticles to Eu3+. The Eu3+ luminescence increased as the Eu3+ concentration increased from 1 vs 5 mole % (for 10 mole % ZnO). In addition, the intensity increased as the embedded ZnO nanoparticles concentration increased up to 10 mole % (for 5 mole % Eu3+). The effects of phonon mediated energy transfer, quenching by activator interactions between Eu3+ ions, and energy back-transfer from Eu3+ ions to ZnO nanoparticles were discussed.     

溶胶-凝胶法制备Eu3+掺杂SiO2玻璃粉体及其性质

采用溶胶-凝胶方法制备了从1%-10%不同浓度Eu离子掺入的SiO2玻璃,并对于不同浓度掺杂和退火处理对其结构和发光性能的影响进行了研究。X射线衍射测试显示,制备出了Eu离子掺入的无定形SiO2玻璃。SEM显示,退火处理后的样品呈多孔“蜂窝”状结构。稀土离子掺入的浓度和退火温度等对Eu离子掺入的SiO2玻璃的结构和荧光发光性质有十分显著的影响。发现稀土离子掺杂浓度从1%-10%的过程中出现了两次浓度淬灭等现象。     

掺Eu3+离子Y2SiO5晶体格位选择光谱研究

分别利用白光灯、４５７－９ ｎｍ 氩离子激光、二倍频ＹＡＧ∶Ｎｄ 激光泵浦的诺丹明６Ｇ 可调谐窄线宽（０－５ ｃｍ －１） 染料激光作为光源， 以单色仪锁相放大器光电倍增管计算机数据采集系统记录光谱， 测量并研究了Ｙ２ＳｉＯ５∶Ｅｕ３ ＋ 晶体的透射光谱、荧光光谱、激发光谱和格位选择荧光光谱。５Ｄ０ →７Ｆ０，１ ，２ ，３，４ 跃迁，３０ 多根谱线（总数为５０ 根） 被观察到。在该晶体中Ｅｕ３＋ 替换Ｙ３＋ 离子， 占据两个较低对称性的光学格位， 这两个格位的５Ｄ０ ７Ｆ０ 能级跃迁谱线相隔大约只有０－２ ｎｍ ， 在室温下有一定的光谱关联。并用Ｘ射线谱对晶体的晶格常数ａ ， ｂ，ｃ 和晶面角度β进行测量， 测量结果显示掺杂后的晶格常数和未掺杂的Ｙ２ＳｉＯ５ 晶格常数基本一致。