稀土发光材料M_2O_3:RE~(3+)（M＝Y，Gd:RE＝Eu，Tb）体系的AAO模板组装

AAO模板具有高度有序的纳米孔阵列，其孔径可以在5一200nm范围内调节，利用AAO模板进行纳米组装已成为纳米结构材料组装的重要技术之一。目前，采用该技术已经制备出了金属、半导体、碳、导电高分子以及其它材料构成的纳米管、纳米线、纳米纤维、电缆等纳米结构单元和有序纳米阵列材料，同时，研究了它们的光、电、磁和催化等特性及其在光学材料、铿电池的电极材料、垂直磁性记录材料和光催化剂等方面的潜在应用。然而，有关稀土发光材料的AAO模板合成及其性质还鲜见报道。本论文采用二次阳极氧化技术制备出了具有高度有序纳米阵列孔的AAO模板。采用溶胶一凝胶法和水热法对稀土发光材料M2O3:RE3+（M＝Y,Gd; RE＝Eu，Tb）体系进行了AAO组装，得到了纳米线、纳米管及其纳米线阵列。对AAO模板和组装样品的形貌、结构和光谱性质进行了表征，得到了一些令人感兴趣的研究结果，其主要的结果和结论总结如下：（1）采用二次阳极氧化法制备出了孔径约为5Onm、35nm和2Onm等系列高度有序纳米阵列孔的基体铝支持的AAO模板和独立支撑的AAO模板。（2）XRD测试结果表明：退火后的基体铝片，其331晶面优先结晶生长，这有利于高度有序纳米阵列孔AAO模板的制备。使用这些退火后的铝片，通过二次阳极氧化法制备的高度有序纳米阵列孔AAO膜为非晶态，并且在退火后转变为γ-Al2O3。（3）未退火的基体铝支持的AAO模板，在350一600nm范围内发出较强的蓝光，其峰值波长位于435nm。该蓝光发射带经过程序控温慢慢退火后完全消失，这说明它产生于缺陷发光中心。（4）采用溶胶一凝胶法，利用AAO模板首次合成出了（YO.96RE0.05）O3（RE＝Eu，Tb）纳米线及其阵列，并通过SEM、EDX、TEM、SAED、XRD和PL分析测试加以确认。x-射线衍射（XRD）和选区电子衍射（SAED）的结果证明，这些纳米线主要是由立方相的RE2O3（RE＝Y或Gd）多晶材料组成的。光谱测试结果表明，同体相材料相比，Eu3＋的，D0一7F2跃迁发射峰和Tb3＋的5D4一7FJ（J=6，5，4，3）跃迁发射峰出现了宽化，这种现象可能是纳米颗粒的表面界面效应所引起的非均匀宽化造成的。（5）首次观察到利用溶胶一凝胶法组装的一部分M2O3:RE3＋（M＝Y，Gd；RE＝Eu，Tb）样品，沿着AAO模板阵列孔壁的边沿所形成的网状结构，并初步地探讨了其形成的机理。（6）对于M2O3:RE3＋（M=Y，Gd；RE＝Eu，Tb）体系，仅仅依靠毛细作用是难以充分地将溶胶前驱液组装进从O模板的阵列孔中。（7）首次利用水热合成法，在中性条件介质下，将（Y，Gd）2O3:Eu3+样品充分地组装进了AAO模板的纳米孔道中，这说明水热产生的高压可以作为AAO模板组 装样品的驱动力。（8）以M2O3: RE3+（M＝Y，Gd；RE＝Eu，Tb）溶胶或氢氧化物沉淀作为前驱物，分别在酸性和碱性条件下，进行了从0模板水热合成组装。实验结果表明，AAO模板被部分地损坏。但在碱性条件下的高压釜中，却得到了单晶纳米管、纳米片和纳米棒。

Controlled Synthesis of Ln(3+) (Ln = Tb, Eu, Dy) and V5+ Ion-Doped YPO4 Nano-/Microstructures with Tunable Luminescent Colors

YPO4 nano/microcrystals with multiform crystal phases and morphologies, such as hexagonal nano/submicroprisms, spherical-like nanoparticles, and nanorods with different length/diameter ratios as well as tetragonal nanospindles, have been synthesized via a facile hydrothermal route. A series of controlled experiments indicate that the pH values in the initial solution, phosphorus sources, and the organic additive trisodium citrate (Cit(3-)) are responsible for crystal phase and shape determination of final products. It is found that Cit(3-) as a ligand and shape modifier has the dynamic effect by adjusting the growth rate of different facets under different experimental conditions, resulting in the formation of various geometries of the final products. The possible formation mechanisms for products with diverse architectures have been presented.

Fabrication and Luminescence Properties of One-Dimensional CaMoO4: Ln(3+) (Ln = Eu, Tb, Dy) Nanofibers via Electrospinning Process

One-dimensional CaMoo(4):Ln(3+) (Ln = Eu, Tb, Dy) nanofibers have been prepared by a combination method of sol-gel and electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and low voltage cathodoluminescence (CL) as well as kinetic decays were used to characterize the resulting samples. SEM and TEM analyses indicate that the obtained precursor fibers have a uniform size, and the as-formed CaMoO4:Ln(3+) nanofibers consist of nanoparticles. Under ultraviolet excitation, the CaMoO4 samples exhibit a blue-green emission band with a maximum at 500 nm originating from the MoO42- groups. Due to an efficient energy transfer from molybdate groups to dopants, CaMoO4:Ln(3+) phosphors show their strong characteristic emission under ultraviolet excitation and low-voltage electron beam excitation.

Synthesis and characterization of monodisperse spherical SiO2@RE2O3 (RE = rare earth elements) and SiO2@Gd2O3:Ln(3+) (Ln = Eu, Tb, Dy, Sm, Er, Ho) particles with core-shell structure

Spherical SiO2 particles have been coated with rare earth oxide layers by a Pechini sol-gel process, leading to the formation of core-shell structured SiO2@RE2O3 (RE = rare earth elements) and SiO2@Gd2O3:Ln(3+) (Ln = Eu, Tb, Dy, Sm, Er, Ho) particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence spectra as well as lifetimes were used to characterize the resulting SiO2@RE2O3 (RE = rare earth elements) and SiO2@Gd2O3:Ln(3+) (Eu3+, Tb3+, Dy3+, Sm3+, Er3+, Ho3+) samples. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ca. 380 nm), smooth surface and non-agglomeration. The thickness of shells could be easily controlled by changing the number of deposition cycles (40 nm for two deposition cycles).

Self-assembled 3D flowerlike Lu2O3 and Lu2O3 : Ln(3+) (Ln = Eu, Tb, Dy, Pr, Sm, Er, Ho, Tm) microarchitectures: Ethylene glycol-mediated hydrothermal synthesis and luminescent properties

Three-dimensional flowerlike Lu2O3 and Lu2O3:Ln(3+) (Ln = Eu, Th, Dy, Pr, Sm, Er, Ho, Tm) microarchitectures have been successfully synthesized via ethylene glycol (EG)-mediated hydrothermal method followed by a subsequent heat treatment process. X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectra, thermogravimetric and differential thermal analysis, elemental analysis, inductively coupled plasma atomic absorption spectrometric analysis, ion chromatogram analysis, X-ray photoelectron spectra, scanning electron microscopy, transmission electron microscopy, photoluminescence spectra as well kinetic decays, and cathodoluminescence spectra were used to characterize the samples. Hydrothermal temperature, EG, and CH3COONa play critical roles in the formation of the lutetium oxide precursor microflowers. The reaction mechanism and the self-assembly evolution process have been proposed. The as-formed lutetium oxide precursor could transform to Lu2O3 With their original flowerlike morphology and slight shrinkage in the size after postannealing process.

Uniform Lanthanide Orthoborates LnBO(3) (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) Microplates: General Synthesis and Luminescence Properties

A variety of uniform lanthanide orthoborates LnBO(3) (Ln = Gd, Nd, Sm, Eu, Tb, and Dy) microplates have been successfully prepared by a general and facile conversion method. One-dimensional (ID) lanthanide hydroxides were first prepared through a simple hydrothermal process. Subsequently, uniform LnBO(3) microplates were synthesized at the expense of the ID precursors during a hydrothermal conversion process. The whole process in this method was carried out in aqueous condition without the use of any organic solvents, surfactant, or catalyst. The as-obtained rare earth ions doped GdBO3 and TbBO3 microplates show strong light emissions with different colors coming from different activator ions under ultraviolet excitation or low-voltage electron beam excitation, which might find potential applications in fields such as light phosphor powders and advanced flat panel display devices.

Highly uniform and monodisperse beta-NaYF4 : Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: Hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu(3+) (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to D-5(0-3) -> F-7(J) (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively.

VIV-UV excited luminescent properties of LnCa4O(BO3)3 : RE3+(Ln = Y, La, Gd; Re=Eu, Tb, Dy, Ce)

Calcium lanthanide oxyborate doped with rare-earth ions LnCa(4)O(BO3)(3):RE3+ (LnCOB:RE, Ln = Y, La, Gd, RE = Eu, Tb, Dy, Cc) was synthesized by the method of solid-state reaction at high temperature. Their fluorescent spectra were measured from vacuum ultraviolet (VUV) to visible region at room temperature. Their excitation spectra all have a broadband center at about 188 nm, which is ascribed to host absorption. Using Dorenbos' and J phi rgensen's work [P. Dorenbos, J. Lumin. 91 (2000) 91, R. Resfeld, C.K. J phi rgensen. Lasers and Excite States of Rare Earth [M], Springer, Berlin, 1977, p. 45], the position of the lowest 5d levels E(Ln,A) and charge transfer band E-ct were calculated and compared with their excitation spectra.Eu3+ and Tb3+ ions doped into LnCOB show efficient luminescence under VUV and UV irradiation. In this system, Ce3+ ions do not show efficient luminescence and quench the luminescence of Tb3+ ions when Tb3+ and Ce3+ ions are co-doped into LnCOB. GdCOB doped with Dy3+ shows yellowish white light under irradiation of 254 nm light for the reason that Gd ions transfer the energy from itself to Dy.

Sr_4Al_(14)O_(25)∶RE~(3+)(RE=Eu,Ce,Tb)中稀土离子的发光性质

采用高温固相反应合成了Sr4Al14O25∶RE3+(RE=Eu,Ce,Tb)样品,研究了其中Eu3+,Ce3+和Tb3+的光谱性质,以及Ce3+与Tb3+共掺时的能量传递现象;发现Eu3+,Ce3+和Tb3+占有两个格位,与Eu2+在此基质中的情况相似;在Tb3+的发射光谱中同时观察到了来自5D3与5D4的发射,表明两能级间无辐射跃迁过程不显著;Ce3+对Tb3+有敏化作用。

共沉淀法合成稀土正磷酸盐(La,Gd)PO_4∶RE~(3+)(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Gd PO4的红外光谱吸收峰与 La PO4一致 ,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 ,La PO4的价带由 O2 -的 2 p能级构成 ,而 Gd PO4的价带则是由 O2 - 的 2 p能级和 Gd3 +的 4 f能级共同构成.

Preparation and luminescence properties of ormosil hybrid materials doped with Tb(Tfacac)(3)phen complex via a sol-gel process

In this paper, silica-based transparent organic-inorganic hybrid materials were prepared via the sol-gel process. Tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used as the inorganic and organic precursors, respectively. The terbium complex, Tb(Tfacac)(3)phen (Tfacac = 1,1,1-trifluoroacetylacetone, phen = 1, 10-phenanthroline) was successfully doped into organically modified silicate (ormosil) matrix derived from TEOS and GPTMS, and the luminescent properties of the resultant ormosil composite phosphors [ormosil/Th(Tfacac)(3)phen] were investigated compared with those of the Tb(Tfacac)(3)phen incorporated into SiO2 derived from TEOS (labeled as silica/Tb(Tfacac)(3)phen). Both kinds of the materials show the characteristic green emission of Tb3+ ion. The luminescence behavior of the resultant composite products was dependent on the matrix composition. The optimized lanthanide complex concentration in the ormosil/Tb(Tfacac)(3)phen was increased compared with in silica/Tb(Tfacac)(3)phen. Furthermore, the lifetime of Tb3+ in Tb(Tfacac)(3)phen, silica/Tb(Tfacac)(3)phen and ormosil/Tb(Tfacac)(3)phen follows the sequence: onmosil/Tb(Tfacac)(3)phen>silica/Tb(Tfacac)(3)phen>pure Tb(Tfacac)(3)phen.

Preparation and characterization of a layered transparent luminescent thin film of silica-CTAB-Tb(acac)(3) composite with mesostructure

A layered luminescent mesostructured thin film of silica-CTAB-Tb(acac)(3) composite has been synthesized by a dip-coating process through an in situ sol-gel method. The terbium (Tb3+) ion and beta-diketone organic ligand acetylacetone (acac) were introduced into the precursor solution, respectively. The as-synthesized composite film was transparent, colorless and possessed a layered structure. After the composite film was dried at 50 degreesC for a few minutes Tb(acac)(3) complex was synthesized in the mesostructured thin film, which can be indicated by the luminescence of the composite film under the UV lamp. The properties of the samples were characterized by XRD, absorption, Fourier transform infrared spectroscopy, and luminescent spectra.

VUV excitation properties of LnAl(3)B(4)O(12): Re (Ln = Y, Gd; Re=Eu, Tb)

Vacuum ultraviolet excitation spectra of LnAl(3)B(4)O(12):Re (Ln = Y, Gd; Re = Eu, To), along with X-ray photoelectron spectra, were measured. The spectra are tentatively interpreted in terms of the optical properties of the rare earth ions and the band structure. It was found that there is an energy transfer from the hosts to the rare earth ions. It was also found that the top of the valence band in the Gd compound is mainly formed by the 2p levels of O2- and the 4f levels of Gd3+, and in the Y compound mainly by the 2p levels of O2-. (C) 2000 Elsevier Science Ltd. All rights reserved.

Electroluminescent properties of the Tris-(acetylsalicylate)-terbium (Tb(AS)(3))

The solubility of [Tris-(acetylsalicylate)-terbium] [Tb(AS)(3)] is improved to a greater extent than [Tris-(salicylate)-terbium] [Tb(Sal)(3)] following introduction of a flexible acetyl group. Th3+ binds with acetylsalicylate in solution at low pH value and the resultant Tb(AS)(3) has good solubility in chloroform. A Green EL device with the structure ITO/PVK/PVB:PBD: Tb(AS)(3)/ PBD/Al has been fabricated based on soluble Tb(AS)(3), in which Tb(AS)(3) was first used as an emissive center doped with PVK and PBD. The hole-transporting layer and the emissive layer were formed by spin coating. The device exhibited a highly pure characteristic green light of Tb3+. (C) 2001 Elsevier Science B.V. All rights reserved.

Synthesis and luminescence characteristics of LiMgAlF6:Ln(3+) (Ln = Ce, Eu, Tb)

By solid state reaction, LiMgAlF6 and LiMgAlF6:Ln(3+) are synthetized with the ratio 120/100/110 of LiF/MgF2/AlF3, at 1008 K, in high-purity Ar stream. Their crystal structure which belongs to hexagonal system are determined by X-Ray-Diffraction (XRD). Luminescence characteristics of Ce3+, Eu3+, Tb3+ and sensitization of Ce3+ to Tb3+ in LiMgAlF6 are studied. It is shown that the sensitization of Ce3+ to Tb3+ is efficient and a bright green emission is observed.