White light emission from Dy3+-doped LiLuF4 single crystal grown by Bridgman method

Lithium lutetium fluoride （LiLuF4） single crystals doped with different Dy3＋ ion concentrations were grown by Bridgman method. The Judd-Ofelt （J-O） strength parameters （Ω2, Ω4, Ω6） of Dy3＋ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3＋：LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3＋：LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultra- violet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3＋ ion in 2.701% molar doping concentration under excitation of 350 nm.     

Tunable emission,concentration quenching and crystallographic sites of Eu^2＋ in Sr3Y（PO4）3

A series of Sr3Y（PO4）3：Eu^2＋ samples are synthesized by the high temperature solid-state method. Sr3Y（PO4）3：Eu^2＋shows an asymmetrical emission band under excitation of 350 nm. The emission peaks at 426 nm and 497 nm are assigned to the nine-coordination Eu^2＋ and six-coordination Eu^2＋, respectively. The effects of Eu^2＋ doping content on the emission intensity and color are observed, and the concentration quenching effect is also observed. For two different Eu^2＋ luminescence centers, the quenching mechanisms are dipole-dipole interaction and quadrupole-quadrupole interaction, respectively. And the critical distance of energy transfer is calculated by concentration quenching and turns out to be about 3.67 nm. The results above show that the asymmetrical emission band of Sr3Y（PO4）3：Eu^2＋ comes from two different Eu2＋ luminescence centers in the lattice.     

Growth and optical properties of Dy3+/Eu3+ co-doped NaYF4 single crystals with cubic lattice for white LED application

Dy3+/Eu3+ co-doped cubic lattice NaYF4 single crystal with high quality in the size of ~Φ1.0 cm×10.0 cm was grown by an improved Bridgman method using potassium fluoride (KF) as assistant flux. X-ray diffraction (XRD), absorption spectra, excitation spectra and emission spectra are measured to investigate the phase and luminescent properties of the crystal. The effects of excitation wavelength and concentrations of Dy3+ and Eu3+ ions on the luminescent characteristics are analyzed. The NaYF4 single crystal with the doping molar concentrations of 1.205% Dy3+ and 0.366% Eu3+ exhibits an excellent white light emission with chromaticity coordinates of x=0.321, y=0.332. It indicates that the Dy3+/Eu3+ co-doped cubic lattice NaYF4 single crystal can be a potential luminescent material for the ultraviolet (UV) light excited white light emitting diode (w-LED).     

电子基因表达谱分析平台的建立及其应用

建立了利用美国国立生物技术信息中心(NCBI)序列表达标签(EST)数据库(dbEST)电子EST构建特定组织电子基因表达谱的生物信息学分析平台,并利用该平台构建了人正常结直肠组织电子基因表达谱.从dbEST获取人正常结直肠电子EST 20 370条,利用自行开发的GetUni程序包,与下载于本地的人类同一基因转录子(UniGene)数据库匹配,获得了含有4 196个非冗余基因的正常结直肠组织电子基因表达谱.经在线基因组分析工具(Webgestalt)证实,表达谱中97%的基因在结直肠组织中表达,除涉及细胞生长、发育、分化、凋亡等基因外,还包括人正常结直肠功能特异性基因;3%未得到Webgestalt证实的基因经手工回溯查找,确证其EST均来自人正常结直肠.GetUni程序包是一个高效准确的高通量电子EST数据分析平台,构建的人正常结直肠组织基因表达谱将为结直肠特异性标志物的筛选提供大量数据.