稀土荧光粉预制品制备新工艺

分析了高温固相合成生产稀土荧光粉和湿法共沉淀预制备法生产稀土荧光粉的特点,表明通过湿法共沉淀可以在较短时间和较低温度下合成稀土荧光粉, 介绍了Y2O3∶ Eu, LaPO4∶ Ce, Tb和SrAl2O4∶ Eu2+的湿法共沉淀预制备的方法.     

稀土离子掺杂LaPO4纳米结构材料形貌、物相的调控及发光性能

利用水热合成技术,通过改变掺杂稀土离子的种类、掺杂浓度及添加剂的种类可实现LaPO4纳米结构材料形貌及物相的调控,同时还研究了合成材料的光致发光性能.结果表明:Ce3+离子掺杂浓度的增加可导致LaPO4纳米棒发生由单斜相向六方相的转变,而Tb3+离子掺杂浓度增加到相同的范围则不能够引起该相转变的发生;具有较小尺寸的LaPO4纳米棒易于"肩并肩"聚集形成纳米棒束;改变掺杂稀土离子的种类和浓度可调控纳米棒束的长度(150 nm～2.0μm),但对纳米棒束的直径影响不大(40～60 nm);添加剂的加入使纳米棒束更均一,对其相结构则基本没有影响;在紫外光激发下,单掺杂Ce3+或Tb3+离子的LaPO4纳米棒束分别表现出Ce3+或Tb3+离子的特征发射,由于Ce3+,Tb3+离子间存在有效的能量传递,Ce3+,Tb3+离子共掺杂的LaPO4纳米棒束表现出较强的Tb3+离子的绿光发射.     

共沉淀法合成稀土正磷酸盐(La,Gd)PO4∶RE3+(RE=Eu,Tb)及其真空紫外光谱特性

采用共沉淀法制备了稀土正磷酸盐荧光粉(La,Gd)PO4∶RE3+(RE=Eu,Tb).红外光谱分析发现GdPO4的红外光谱吸收峰与LaPO4一致,只是峰位向高波数方向移动.(La,Gd)PO4∶RE3+的真空紫外光谱特性研究表明,Gd3+在能量传递过程中起中间体作用.XPS研究揭示,LaPO4的价带由O2-的2p能级构成,而GdPO4的价带则是由O2-的2p能级和Gd3+的4f能级共同构成.     

稀土磷酸盐纳米发光材料的研究进展

纳米发光材料;荧光性能;壳核结构;稀土磷酸盐;稀土离子掺杂     

共沉淀法合成稀土正磷酸盐(La,Gd)PO4:RE3+(RE=Eu,Tb)及其真空紫外光谱特性

采用共沉淀法制备了稀土正磷酸盐荧光粉(La,Gd)PO4:RE3+(RE=Eu,Tb).红外光谱分析发现GdPO4的红外光谱吸收峰与LaPO4一致,只是峰位向高波数方向移动.(La,Gd)PO4:RE3+的真空紫外光谱特性研究表明,Gd3+在能量传递过程中起中间体作用.XPS研究揭示,LaPO4的价带由O2-的2p能级构成,而GdPO4的价带则是由O2-的2p能级和Gd3+的4f能级共同构成.     

SrAl2O4∶Tb3+荧光粉的合成与发光性研究

报道了以高温固相法合成SrAl2O4 Tb3+光致绿色荧光粉, 并用X射线粉末衍射对其结构进行了表征.在SrAl2O4 Tb3+体系中加入Ce3+, 得到了发绿色光的长余辉荧光粉, 利用荧光分光光度计测定了两种荧光粉的激发光谱和发射光谱.对荧光体发光机理进行了探讨 认为O2-空位Vo是一种电子俘获陷阱, 是形成余辉的根本原因, Ce3+的加入使陷阱的深度适宜而使余辉时间延长.     

Tb3+掺杂CePO4核壳微球的水热合成及其发光性能

在pH=1无模板条件下水热合成出直径为2~3 μm的CePO4∶Tb核壳微球结构。 其核壳表面由直径为20~30 nm、长度为200~300 nm的纳米棒组成。 产物生长过程实验表明,首先形成球状团聚产物,然后一些颗粒在表面生长,由于奥斯瓦尔德熟化效应产物尺寸变大,最后表面上的部分颗粒消耗内部的核而外延生成一维纳米棒。 CePO4∶Tb核壳微球的荧光性质和荧光寿命测试表明,当Tb3+摩尔分数为10%时,发射强度达到最大值,Tb3+浓度再增加其荧光发射强度由于浓度淬灭作用而迅速降低。     

荧光纳米材料YPO4∶Sm3+@YPO4@聚乙二醇的构筑及其荧光性能

为了改善稀土磷酸盐的疏水性和荧光性能,利用水热和微波的方法构筑了双层荧光纳米材料YPO₄∶Sm³⁺@YPO₄@PEG (PEG为聚乙二醇)。首先通过调控YPO₄∶Sm³⁺与YPO₄的物质的量之比制备不同壳厚的核壳结构纳米发光材料YPO₄∶Sm³⁺@YPO₄,优选能够增强主体荧光性能的最佳物质的量之比。然后选用PEG进行包覆,得到YPO₄∶Sm³⁺@YPO₄@PEG。利用X射线衍射、扫描电子显微镜、透射电子显微镜、傅里叶变换红外光谱和荧光光谱对产物的结构、形貌和荧光性能进行了表征。结果表明：包覆前后的纳米荧光粉都具有单一的四方晶系(YPO₄)结构,呈纳米球型,半径60~100 nm,包覆层的厚度10~20 nm。双层核壳结构的YPO₄∶Sm³⁺@YPO₄@PEG的荧光强度比纳米荧光粉YPO₄∶Sm³⁺增强了6倍多。可见该双层荧光纳米材料不仅具有亲水性和生物相容性,也增强了YPO₄∶Sm³⁺的荧光强度。     

Ag@SiO2@Y2O3:RE3+（RE=Eu,Tb）核壳结构发光材料的制备与性能

采用均相沉淀法制备了Ag@SiO2@(Y,RE)(OH)CO3.H2O(RE=Eu,Tb)核壳结构微球,经过700℃焙烧后成功制备出Ag@SiO2@Y2O3:RE3+(RE=Eu,Tb)核壳结构发光材料。XRD谱图表明Ag核具有结晶良好的面心立方结构;SiO2层为无定型;Y2O3层为立方晶系。FTIR谱图表明核壳之间以化学键相结合。TEM照片表明合成了核壳结构的表面光滑的复合微球,分散良好,大小均匀,Ag核的粒径分布为50±20 nm;SiO2层的厚度为20～30 nm;Y2O3:RE3+(RE=Eu,Tb)层厚度约为125 nm。电子衍射图像表明Ag@SiO2@Y2O3:RE3+(RE=Eu,Tb)为多晶结构。UV-Vis光谱表明表面包覆使Ag离子的等离子体共振吸收峰发生了红移。荧光光谱表明Ag@SiO2@Y2O3:Eu3+具有Eu3+的特征红光发射,Ag@SiO2@Y2O3:Tb3+具有Tb3+的特征绿光发射,但是发光强度均比纯的Y2O3:RE3+有所减弱,说明贵金属的引入对稀土Y2O3:RE3+(RE=Eu,Tb)的发光起到了荧光猝灭的作用。     

Eu~(3+)掺杂的LaPO_4和LaAlO_3纳米体系及其发光性质

Eu3+离子掺杂的LaPO4纳米线或纳米棒通过一种简单的水热反应方法被成功地合成出来.水热反应条件以及生成产物的烧结条件对LaPO4基质材料的形貌和结构的影响,通过扫描电子显微镜和X射线衍射等表征手段进行了研究.生成物的物相和形貌可以通过改变反应条件得到很好的控制.LaAlO3也是一种很重要的无机材料,其粉末状态有较高活性和选择性,因而作为催化剂被广泛研究.其体相材料因具有钙钛矿结构,与Y-Ba-Cu-O和Bi-Sr-Ca-Cu-O等超导体系有很好的点阵匹配和热扩散匹配.稀土离子掺杂的镧系化合物的光致发光性不仅与基质材料的组成结构有关,而且与晶体的形貌和尺寸也有关,所以Eu3+离子分别被掺入到单斜晶系独居石结构的LaPO4和钙钛矿结构的LaAlO3中以作对比实验.为了了解反应物周围环境对产物性质的影响,LaPO4:Eu3+和LaAlO3:Eu3+的纳米颗粒同时用共沉淀法制得.不同形貌的LaPO4:Eu3+纳米体系的发光强度略有不同.掺杂的单斜晶系独居石结构的LaPO4和钙钛矿结构的LaAlO3纳米颗粒发光最强时,Eu3+离子的最佳掺杂摩尔百分比分别为5.0%和3.5%.在适当的紫外光照射下,LaAlO3:Eu3+(3.5mol%)比LaPO4:Eu3+(5.0mol%)发射更亮的红光,这是由于两者有不同的自旋轨道耦合和共价键,这表明在纳米尺度下,LaAlO3也是一种很好的稀土离子掺杂的基质材料.     

Systematic synthesis and characterization of single-crystal lanthanide orthophosphate nanowires

A simple hydrothermal method has been developed for the systematic synthesis of lanthanide orthophosphate crystals with different crystalline phases and morphologies. It has been shown that pure LnPO(4) compounds change structure with decreasing Ln ionic radius: i.e., the orthophosphates from Ho to Lu as well as Y exist only in the tetragonal zircon (xenotime) structure, while the orthophosphates from La to Dy exist in the hexagonal structure under hydrothermal treatment. The obtained hexagonal structured lanthanide orthophosphate LnPO(4) (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) products have a wirelike morphology. In contrast, tetragonal LnPO(4) (Ln = Ho, Er, Tm, Yb, Lu, Y) samples prepared under the same experimental conditions consist of nanoparticles. The obtained hexagonal LnPO(4) (Ln = La --> Tb) can convert to the monoclinic monazite structured products, and their morphologies remained the same after calcination at 900 degrees C in air (Hexagonal DyPO(4) is an exceptional case, it transformed to tetragonal DyPO(4) by calcination), while the tetragonal structure for (Ho--> Lu, Y)PO(4) remains unchanged by calcination. The resulting LnPO(4) (Ln = La --> Dy) products consist almost entirely of nanowires/nanorods with diameters of 5-120 nm and lengths ranging from several hundreds of nanometers to several micrometers. Europium doped LaPO(4) nanowires were also prepared, and their photoluminescent properties were reported. The optical absorption spectrum of CePO(4) nanowires was measured and showed some differences from that of bulk CePO(4) materials. The possible growth mechanism of lanthanide phosphate nanowires was explored in detail. X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, electron diffraction, infrared absorption spectra, X-ray photoelectron spectroscopy, optical absorption spectra, and photoluminescence spectra have been employed to characterize these materials.     

Luminescence switching behavior through redox reaction in Ce3+ co-doped LaPO4:Tb3+ nanorods: re-dispersible and polymer film

Re-dispersible Tb(3+) doped LaPO(4) nanorods have been prepared using ethylene glycol (EG) as a capping agent as well as reaction medium at a relatively low temperature of 150 °C. The X-ray diffraction study reveals that all the doped samples are well crystalline with a monoclinic structure of the LaPO(4) phase. The luminescence intensity of (5)D(4)→(7)F(5) transition at 543 nm (green) is more prominent than that of (5)D(4)→(7)F(6) transition at 487 nm (blue) for all the samples. This is related to the polarizing effect from [PO(4)](3-) to the Tb(3+) site. Concentration dependent luminescence study shows that the luminescence intensity of Tb(3+) increases up to 10 at.% and decreases above this. This is due to the concentration quenching effect arising from cross relaxation among Tb(3+)-Tb(3+) ions. The results show that nanoparticles prepared in EG medium gives an enhanced luminescence compared to that prepared in water. This is attributed to the multiphonon relaxation effect from O-H groups surrounding over nanoparticles as well as the extent of increase of agglomeration among particles for samples prepared in water. Significant enhancement in the emission of Tb(3+) is also observed when Ce(3+) is used as the sensitizer in LaPO(4):Tb(3+)nanorods. The optimum concentration of Ce(3+) for maximum luminescence is found to be 7 at.% in Ce(3+) sensitized LaPO(4):Tb(3+) (5 at.%). Based on the energy transfer process from Ce(3+) to Tb(3+), the luminescence of Tb(3+) can be switched OFF and ON by performing oxidation and reduction of Ce(3+)?Ce(4+) using KMnO(4) and ascorbic acid, respectively. The samples are re-dispersible in water, methanol and can be incorporated into polyvinyl alcohol (PVA) films. They show a dark green emission under ultraviolet radiation.     

Eu~(3+)-doped LaPO_4 and LaAlO_3 nanosystems and their luminescence properties

Eu3+ ion-doped LaPO4 nanowires or nanorods have been successfully synthesized by a simple hydrothermal method.The influence of varying the hydrothermal and subsequent sintering conditions on the morphology and structure of the LaPO4 host has been investigated by scanning electron microscopy(SEM) and X-ray diffraction(XRD).For comparison,the Eu3+ ions were also doped into monoclinic monazite LaPO4 nanoparticles and perovskite LaAlO3 nanoparticles.The relative intensities of the emission lines of the LaPO4:Eu...     

Electronic transition and energy transfer processes in LaPO4-Ce3+/Tb3+ nanowires

Ce3+ and Tb3+ coactivated LaPO4 nanowires and micrometer rods were synthesized by hydrothermal methods. Their fluorescent spectra and dynamics were systematically studied and compared. The results indicated that the extinction coefficients of Ce3+ and Tb3+ in nanowires were higher than those in micrometer rods. The electronic transition rates of Ce3+ and Tb3+ in nanowires had little variation in contrast to those in micrometer rods, and the energy transfer rate and efficiency of Ce3+ --> Tb3+ in nanowires were reduced greatly. It is important to observe that the brightness for the 5D4-7F5 green emissions of Tb3+ via energy transfer of Ce3+ --> Tb3+ in nanowires increased several times that in micrometer rods. This was attributed to the decreased energy loss in the excited states, being higher than 5D4 due to the hindrance of the boundary.     

基于LaPO_4∶Ce,Tb-Au发光共振能量转移测定细胞色素C

以膦酰基羧酸共聚物为修饰剂,采用水热法制备了LaPO_4∶Ce,Tb发光纳米粒子,该粒子具有良好的水溶性和生物相容性。对合成的纳米粒子进行了发光光谱、X-射线衍射、透射电子显微镜和红外光谱表征。以制备的纳米粒子为能量供体,纳米金为能量受体,细胞色素C(Cyt C)为桥,构建了LaPO_4∶Ce,Tb-Au发光共振能量转移(LRET)体系,据此建立了测定Cyt C的新方法。实验结果表明,当Cyt C的浓度在0.333~21.0μg·mL~(-1)范围时,LRET体系发光猝灭程度与Cyt C浓度呈良好线性关系,检出限(S/N=3)为0.2μg·mL~(-1),相对标准偏差(RSD)为0.46%(c=10.0μg·mL~(-1),n=11)。该方法用于实际样品的测定,回收率范围为100%~101%。     

Epitaxial synthesis of uniform cerium phosphate one-dimensional nanocable heterostructures with improved luminescence

Uniform CePO(4)@LaPO(4) and CePO(4):Tb(3+)@LaPO(4) one-dimensional single-crystalline nanocable heterostructures with highly enhanced photoluminescent emission have been synthesized via a mild and simple hydrothermal approach. The resulting one-dimensional single-crystalline nanocable heterostructures have smooth and uniform LaPO(4) sheaths, which is of great significance in effectively eliminating surface trap-states and suppressing the energy quenching in energy-transfer processes. The photoluminescence results for these one-dimensional nanocable heterostructures illustrate that the uniform LaPO(4) sheaths remarkably increase the luminescent efficiency.     

液相浸渗法制备Y-TZP/LaPO4可加工复相陶瓷

通过往ZrO2多孔陶瓷浸渗LaPO4液态先驱液制备了具有可加工性的Y－TZP／LaPO4复相陶瓷。加入30％（体积分数）石墨可以得到具有35％（体积分数）开孔气孔率的ZrO2预烧结陶瓷体。采用不同浸渗和热分解周期可以得到不同LaPO4含量的Y－TZP／LaPO4复相陶瓷。研究了该材料的可加工性和力学性能。结果表明，含有3.5%-7.5%(体积分数）LaPO4的Y－TZP／LaPO4复相陶瓷具有良好的可加工性，同时保持优良的力学性能。     

Synthesis of Eu3+-doped core and core/shell nanoparticles and direct spectroscopic identification of dopant sites at the surface and in the interior of the particles

A variety of redispersible Eu(3+)-doped LaPO(4) nanoparticles have been prepared in a high-boiling coordinating solvent mixture, and the Eu(3+) lattice sites of these materials have been investigated by luminescence line-narrowing measurements. In this spectroscopic method, Eu(3+) ions occupying different lattice sites are selectively excited with a tunable narrow-bandwidth laser system and distinguished by their luminescence spectra ("site-selective spectroscopy"). Depending on the concentration of the dopant, up to three different lattice sites could be identified in the interior of the LaPO(4) nanoparticles. These sites correspond to those known from bulk LaPO(4). In addition, a variety of surface sites is observed, which could be converted completely into bulk sites by overgrowing the nanoparticles with a shell of pure LaPO(4). The surface sites are identical to those obtained by reacting Eu(3+) with the surface of pure LaPO(4) nanoparticles. The spectroscopic properties of Eu(3+)-doped LaPO(4) nanoparticles differ from those of pure EuPO(4) nanoparticles, which were also investigated. Remarkably, the core/shell synthesis investigated in this paper allows one to prepare doped nanoparticles that contain no other dopant sites than those known from the corresponding bulk material.     

A simple mixed-solvothermal route for LaPO4 nanorods: synthesis, characterization, affecting factors and PL properties of LaPO4:Ce3+

In this paper, LaPO(4) nanorods have been successfully synthesized via a simple water-ethyleneglycol (H(2)O-EG) mixed-solvothermal route, employing lanthanum nitrate (La(NO(3))(3)·xH(2)O) as a La(3+) ion source and monobasic sodium phosphate (NaH(2)PO(4)·2H(2)O) as a PO(4)(3-) ion source. The as-obtained products were characterized by means of X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), (high resolution) transmission electron microscopy (HR/TEM), selected area electron diffraction (SAED) and field emission scanning electron microscopy (FESEM). Some factors influencing the formation of LaPO(4) nanorods, including the reaction temperature, the volume ratio of water/EG and the original amount of H(2)PO(4)(-) ions, were investigated. Experiments showed that the volume ratio of water/EG and the original amount of H(2)PO(4)(-) ions could markedly affect the morphology of the final product.