Water-soluble Ln-doped calcium fluoride nanocrystals: Controlled synthesis and luminescence properties

Water-soluble CaF₂ nanocrystals doped with different lanthanide ions (Eu³⁺, Tb³⁺) have been synthesized via a novel method using methanol as solvent. These nanocrystals can well disperse in water, forming a stable and transparent colloidal solution. The colloids of the Eu³⁺ and Tb³⁺ doped nanocrystals display intense red and green luminescence under ultraviolet excitation, respectively. The phase structures, morphology, surface structure and luminescence properties of CaF₂:Ln³⁺ nanocrystals were explored in detail. All of the results showed that these nanocrystals own powerful potentials as Down-conversion fluorescent label materials.     

Luminescence Characteristics and Energy Transfer Machanismof LaOBr:Tb~(3+) (Dy~(3+))

The rare earth luminescence materials LaOBrfTb3+(Dy3+) were synthesized at high temperature,and the structure and luminescence characteristics were studied. The co-doping Dy3+ may make the energy of 5D3 of Tb3+ transfer to 5D4 level, which makes the emission of 5D4-7FJ (J=0,1... 6), specially of 5D4-7F5, enhance obviously, and the total brightness is increased by about 40% in comparison with the samples without Dy3+ cations, as a result of the energy transfer of dipole-dipole interaction.     

溴氧镧铽镝的发光特性及能量传递机理

使用高温常压方法合成了稀土发光材料ＬａＯＢｒ２Ｄｙ＾３＋，Ｔｂ＾３＋，研究了其结构，紫外４主阴极射线激发下的激发与发射光谱，Ｄｙ＾３＋的掺杂可将Ｔｂ＾３＋的＾５Ｄ３能级激光能有地弛豫到＾５Ｄ４能级，从而使５Ｄ４－Ｆ（Ｊ＝０，１）的发射，尤其是＾５Ｄ４－＾７Ｆ５的发射增强，发光亮度提高。     

ZrO2和ZrO2:Dy3+纳米晶发光特性

采用液相沉淀法制备了不同掺杂浓度和尺寸的ZrO2和ZrO2:Dy纳米晶,研究了其发光特性.结果表明在纳米ZrO₂中,存在着宽带激发和发射,起源为电子在价带和导带之间的跃迁.在Dy³⁺掺杂的样品中,随着颗粒尺寸的长大,其发光增强.并且共掺杂Li⁺的样品发光强度被极大地提高.随着Dy³⁺浓度的变化,黄发射和蓝发射的强度比(Y/B)发生改变,且浓度猝灭是通过近邻激活剂间的交换作用进行的.     

SrAl2O4:Eu2+,Dy3+光致发光搪瓷涂层的制备

稀土Eu^2 激活的铝酸盐发光材料是近年来新发展起来的新型长余辉光致发光材料，由于其发光亮度和发光余辉比传统的硫化物高许多，且无毒，无放射性，因而引起广泛关注，采用高温固相反应法制备了SrAl2O4:Eu^2 ,Dy^3 发光材料，并利用SrAl2O4:Eu^2 ,Dy^3 发光材料，参考普通搪瓷的制备工艺，制得了性能稳定的光致发光搪瓷涂层，余辉时间长达12h以上，这种发光搪瓷涂层可用于制造广告牌，交通标牌和建筑物标识牌等，在许多领域有应用前景。     

Photoluminescence and energy transfer study of Er3+ and Dy3+ codoped tellurite glasses

Photoluminescence properties of the Er(3+)-Dy3+ codoped tellurite glasses were studied by absorption and visible emission spectra, which revealed luminescence bands of both Er3+ and Dy3+ when pumping with the wavelength of 325 nm. The concentration quenching occurred as Dy3+ concentration increased beyond 3 mol%. The dependence of Er3+ characteristic emission on Dy3+ concentration indicated energy transfer process between Er3+ and Dy3+. The chromaticity coordinates of these glasses are close to white light, which implies that these glasses might be potential candidates for white lighting through an appropriate combination.     

Combustion synthesis and luminescence characteristic of Eu<Superscript>3+</Superscript>-doped barium stannate nanocrystals

It is the first time that the undoped and Eu³⁺-doped barium stannate nanocrystals with definite morphologies are synthesized using a new combustion method. This method offers several attractive advantages such as: currency for any reagents, simple process, surprisingly short calcination time, availability of mass production and good repeatability with low cost. The characteristics of the as-synthesized nanocrystals are described with X-ray diffraction, transmission electron micrograph and luminescence spectrum.     

光激励发光材料BaFCl：Eu中的发光中心

本文研究了光激励发光材料ＢａＦＣｌ：Ｅｕ中的发光中心。在不同的反应气氛下ＢａＦＣｌ：Ｅｕ具有不同的发光性质。利用光谱的方法、Ｘ射线光电子能谱的方法，研究了在不同条件下制备的ＢａＦＣｌ：Ｅｕ样品中，稀土离子Ｅｕ的性质。     

热释发光-正电子湮灭法研究SrAl2O4基磷光体长余辉发光机制

利用传统陶瓷制备方法合成了长余辉SrAl2O4：Eu，Dy发光粉材料，并利用热释发光—正电子湮灭法对该材料的发光性能及机理进行了研究。研究结果表明，掺杂的Eu在基质材料中主要充当发光中心，而Dy离子主要充当陷阱能级。正电子湮灭试验结果表明，Sr0.94Al2O4：Eu0.02和Sr0.94Al2O4：Eu0.02，Dy0.04存在带负电中心的缺陷，共掺杂的Dy^3 进到Sr^2 位，同时产生一定量的Sr空位，热释发光谱结果表明，单掺杂Eu离子的磷光体中缺陷陷阱深度较深，约为0．95eV，随着Dy的共掺杂，热释发光强度相应增加，陷阱深度降为0．51eV，对于长余辉发光机制，认为陷阱能级捕获的空穴与介稳态(Eu^1 )^*的复合，导致了长余辉现象的发生，并且由于陷阱深度的变化，导致余辉性能出现较大的差异。     

Enhanced luminescence of Cu-In-S nanocrystals by surface modification

We have synthesized highly luminescent Cu-In-S nanocrystals by heating the mixture of metal carboxylates and alkylthiol under inert atmosphere. We modified the surface of CIS nanocrystals with zinc carboxylate and subsequent injection of alkylthiol. As a result of the surface modification, highly luminescent CIS@ZnS core/shell nanocrystals were synthesized. The luminescence quantum yield (QY) of best CIS@ZnS nanocrystals was above 50%, which is more than 10 times higher than the initial QY of CIS nanocrystals before surface modification (QY = 3%). Detailed study on the luminescence mechanism implies that etching of the surface of nanocrystals by dissociated carboxylate group (CH3COO-) and formation of epitaxial shell by Zn with sulfur from alkylthiol efficiently removed the surface defects which are major non-radiative recombination sites in semiconductor nanocrystals. In this study, we developed a novel surface modification route for monodispersed highly luminescent Cu-In-S nanocrystals with less toxic and highly stable precursors.     

Fluorescence properties of Dy(3+) doped La(3)Ga(5.5)Nb(0.5)O(14) nanocrystals

The effects of Dy(3+) doping concentration and calcinations on the fluorescence properties of La(3)Ga(5.5)Nb(0.5)O(14) (Dy:LGN) nanocrystals were examined for the first time. High quality Dy:LGN nanocrystals were synthesized by the sol-gel method. The room temperature fluorescence spectra were measured; they showed a yellow emission, which can be attributed to the (4)F(9/2)-(6)H(13/2) transition. The relationship between the relative emission intensity and the doping concentration of the specimens, sintered at different temperatures, is consistent with a Gaussian distribution according a fitted and modified formula. The optimum value of the Dy(3+) doping concentration in LGN nanocrystals is in the range 2.0-2.5%. Moreover, in LGN bulk crystal for laser use, the optimum value, calculated through the obtained formula, is presumed in the range 1.5-2.0%. The fluorescent lifetime of a 2.0% Dy:LGN nanocrystal is quite short, only about 8.5?ns.     

Photoluminescence of Eu3+-doped LaPO4 nanocrystals synthesized by combustion method

Eu³⁺-doped LaPO₄ nanocrystals were synthesized for the first time by a combustion method with urea as a fuel calcined at 700 °C. The diffraction profile of the obtained sample was indexed as a monoclinic monazite-structure by X-ray diffraction (XRD) data. The obtained nanocrystals appeared to be short rod-like with diameters of 5–10 nm and lengths of 20–70 nm. The luminescence intensities of Eu³⁺-doped LaPO₄ nanocrystals were found to be strongly dependent on the quantities of urea added and the concentration of Eu³⁺.     

White light emission from spin coated Gd2O3:Dy nano phosphors synthesized using polyol technique

Water dispersible Gd2O3:Dy3+ (2%) nanophosphors were synthesized through a facile polyol process and characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Dynamic Light Scattering (DLS) and photoluminescence (PL) spectrophotometry. The results of XRD, TEM and DLS show that resultant nanoparticles are single phasic and have spherical shape with 17 to 22% dispersibility. An efficient energy transfer was observed from host to the dopant ions. Characteristic blue and yellow emissions from Dy3+ ions were observed. The CIE coordinates of the nanophosphor lie in the white light region of the chromaticity diagram. Spin coating of the nanophosphor was done on quartz substrate. Bright white luminescence of this film was observed under ultraviolet light with lamda exc = 310 nm.     

Synthesis of colloidal upconverting NaYF4: Er3+/Yb3+ and Tm3+/Yb3+ monodisperse nanocrystals

The synthesis, characterization, and spectroscopy of upconverting lanthanide-doped NaYF4 nanocrystals (NCs) is presented. The monodisperse cubic NaYF4 NCs were synthesized via a thermal decomposition reaction of trifluoroacetate precusors in a mixture of technical grade chemicals, octadecene and the coordinating ligand oleic acid. In this straightforward method, the dissolved precursors are added slowly to the reaction solution through a stainless-steel canula resulting in highly luminescent nanocrystals with an almost monodisperse particle size distribution. The NCs were characterized through the use of transmission electron microscopy, selected area electron diffraction, 1H NMR, powder X-ray diffraction, and high-resolution luminescence spectroscopy. The NaYF4 NCs are capable of being of dispersed in nonpolar organic solvents thus forming colloidally stable solutions. The colloids of the Er3+, Yb3+ and Tm3+, Yb3+ doped NCs exhibit green/red and blue upconversion luminescence, respectively, under 980 nm laser diode excitation with low power densities.     

Photoluminescence of erbium-oxygen-codoped silicon multilayers prepared by molecular beam epitaxy

Erbium-oxygen-codoped silicon multilayer film, which consists of alternate erbium-oxygen-codoped silicon layers and oxygen-doped silicon layers, was synthesized by molecular beam epitaxy. Er³⁺-related luminescence from erbium-oxygen-codoped multilayer film is stronger than that of erbium-oxygen-codoped monolayer film and shows a weak temperature quenching behaviour. These improvements may be explained by the effect of O-doped Si layers in the multilayer film. The O-doped Si layers have a wide gap which prohibits the energy backtransfer effectively. At the same time, photogenerated carriers from silicon nanocrystals in O-doped Si layers could transfer the energy to neighboring Er³⁺ ions in Er-O-codoped Si layers by a tunneling process, thus enhancing the Er³⁺-related luminescence.     

Preparation of copper-doped CdSe nanocrystals

Sols of stabilized copper-doped CdSe nanocrystals in a nonpolar high-boiling solvent have been synthesized using cadmium oleate, copper stearate, and trioctylphosphine selenide as starting reagents. The average size of the nanocrystals is 2.8–2.9 nm, with a 10% variance, as evaluated from their absorption spectra. The samples show excitonic luminescence and bright near-IR (700–900 nm) luminescence with a lifetime on the order of 0.5–1 μs. The luminescence spectroscopy data are consistent with the assumption that the copper distribution over the nanocrystals follows Poisson’s law. The average copper content of the samples is 0.1–2 atoms per nanocrystal.     

Ultrasound-induced morphology transformation from 3D microspheres to 1D nanorods of luminescent coordination polymer

Hierarchically spherical architectures self-assembled by nanorods of coordination polymer La(1,3,5-BTC)(H2O)6:Dy3+ have been successfully prepared on a large scale via rapid static growth in solution phase at room temperature. Interestingly, these uniform and well-dispersed 3D microspheres are sensitive to ultrasound, which can be completely transformed into 1D nanorods through simple ultrasonic treatment. The photoluminescence properties of the nano/microstructured La(1,3,5-BTC)(H2O)6:Dy3+ are also investigated in detail, indicating that the obtained lanthanum 1,3,5-benzenetricarboxylate is a new promising host material for the luminescence of Dy3+ ions.     

Dy3+掺杂CaWO4荧光粉体的制备及发光性能

采用固相陶瓷方法制备了Dy3+掺杂的CaWO4∶Dyx3+荧光粉体。采用XRD、SEM和FT-IR对制备粉体的微观结构进行了表征;采用荧光分析法研究了制备的荧光体的室温光致发光性能;探讨了掺杂剂Dy3+浓度对CaWO4∶Dyx3+荧光粉体的微结构和光致发光性能的影响。结果表明,制备的CaWO4∶Dyx3+荧光粉体为白钨矿结构,Dy3+的掺入会抑制CaWO4∶Dy3x+晶粒的生长。当Dy3+的掺入量为1%(摩尔分数)时,其在480nm(蓝)和575nm(黄)的发射强度达到最大;随着Dy3+浓度的增加,其特征发射峰(480nm和575nm)强度反而逐渐下降。     

YVO_4:Eu~(3+)纳米晶的沉淀合成及发光性质

采用沉淀法合成了Eu3+不同掺杂浓度的YVO4:Eu3+纳米晶。利用X射线衍射和荧光光谱对材料的结构、发光性能进行了研究。XRD研究结果表明:在较低温度下合成的样品为四方相YVO4,纳米粒子的晶粒尺寸为7nm。发射光谱和激发光谱的研究表明:宽的激发带主要来自于Eu-O和V-O的电荷迁移带。发射峰来自于5D0-7FJ的跃迁。纳米YVO4:Eu3+的猝灭浓度为12%,荧光寿命随Eu3+离子的浓度的增加而缩短。     

Controllable multicolor upconversion luminescence of lanthanide doped NaGdF4 nanocrystals through single laser excitation at 980 nm

Room temperature multicolor Upconversion (UC) luminescence in Yb3+, Tm3+, Er3+ ions doped NaGdF4 nanocrystals have been successfully synthesized by a hydrothermal method. As-prepared nanocrystals are highly crystalline and well-dispersed in cyclohexane to form stable and clear colloidal solutions, which demonstrates strong emission properties with a single laser excitation at 980 nm. The multicolor light consists of blue, green, and red UC radiations that correspond to transitions 1G4 --> 3H6 of Tm3+, 2H(11/2)/4S(3/2) --> 4I(15/2), and 4F(9/2) --> 4I(15/2) of Er3+ ions, respectively. The UC mechanisms were proposed based on spectral, kinetic, and pump power dependence analyses.