Preparation and luminescence characteristics of Sr3SiO5：Eu^2＋ phosphor for white LED

The Sr3SiO5：Eu^2＋ phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5：Eu^2＋ shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5：Eu^2＋ is influenced by the Eu^2＋ concentration. The relative emission spectra of the white-emitting InGaN-based YAG：Ce^3＋ LED and Sr3SiO5：Eu^2＋ LED were investigated. The results show that the color development of InGaN-based Sr3SiO5：Eu^2＋ is better than that of InGaN-based YAG：Ce^3＋, and the CIE chromaticity of InGaN-based Sr3SiO5：Eu^2＋ is （x=0.348, y=0.326）.     

Visible-light-driven Ag/Ag3PO4-based plasmonic photocatalysts: Enhanced photocatalytic performance by hybridization with graphene oxide

An efficient visible-light-driven plasmonic photocatalyst with regard to graphene oxide(GO) hybridized Ag/Ag3PO4(Ag/Ag3PO4/GO) nanostructures has been facilely synthesized via a deposition-precipitation method.The synthesized nanostructures have been characterized by means of scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDX),X-ray diffraction(XRD),UV-vis spectra,Fourier transform infrared spectra(FT-IR),X-ray photoelectron spectroscopy(XPS),and Raman spectra.It has been disclosed that compared with the bare Ag/Ag3PO4 nanospecies,the GO hybridized nanostructures display enhanced photocatalytic activity for the photodegradation of methyl orange pollutant under visible-light irradiation.It is suggested that the reinforced charge transfer and the suppressed recombination of electron-hole pairs in Ag/Ag3PO4 /GO,the smaller size of Ag/Ag3PO4 nanospecies in Ag/Ag3PO4/GO,all of which are the consequences of the hybridization of GO,are responsible for the enhanced photocatalytic performance.The investigation might open up new opportunities to obtain highly efficient Ag3PO4-based visible-light-driven plasmonic photocatalyst for the photodegradation of organic pollutants.     

Preparation and Composition-Structure-Thermal Stability Relation of a Novel Open-framework Vanadium Phosphate (H3NCH2CH2NH3)3[(VO)4(PO4)2(HPO4)4]

A novel open-framework vanadium(Ⅳ) phosphate (H3NCH2CH2NH3)3[(VO)4(PO4)2(HPO4)4] (short for V2P3-en) has been prepared. It is synthesized hydrothermally in the presence of ethylenediamine (en) at 170℃ for 5 days by self-assembly from structurally simple precursors V2O5, H3PO4 and H2O. The compound is characterized by means of Fourier transform-infrared spectroscopy (FT-IR), Thermogravimetry-differential thermal analysis (TG-DTA), X-ray powder diffraction analysis (XRD) and Scanning electron microscopy (SEM). Furthermore, the composition-structure-thermal stability relation of V2P3-en is explored in terms of crystal chemistry, and the potential approach to the enhancement of its thermal stability is proposed.     

Preparation and luminescence characteristics of Sr_3SiO_5:Eu~(2 ) phosphor for white LED

The Sr3SiO5:Eu2 phosphor was synthesized by high temperature solid-state reaction. The emission spectrum of Sr3SiO5:Eu2 shows two bands centered at 487 and 575 nm, which well agree with the theoretic values of emission spectrum. The excitation spectrum for 575 nm emission center has several excitation bands at 365, 418, 458 and 473 nm. And the results show that the emission spectrum of Sr3SiO5:Eu2 is influenced by the Eu2 concentration. The relative emission spectra of the white-emitting InGaN-based YAG:Ce3 LED and Sr3SiO5:Eu2 LED were investigated. The results show that the color development of InGaN-based Sr3SiO5:Eu2 is better than that of InGaN-based YAG:Ce3 , and the CIE chromaticity of InGaN-based Sr3SiO5:Eu2 is (x=0.348, y=0.326).     

Synthesis of 1 -（5 - nitro - 3 - phenylazophenyl）-triazene and Its Color Reaction with Cobalt

A new chromogenie reagent, 1 -(5-nitro- 3-benzopsendothiazde)- 3 -(4-phenylazophenyl)-triazene (NBPTPAPT) has been synthesized and used as a sensitive reagent for the spectrophotometric determination of cobalt.In the presence of Tween-80, the reagent with Co (Ⅱ)forms a yellow complex (1 2) in the buffer solution of Na2B4O7-NaOH at pH 10.54. The apparent molar range of 0-240 μg/ L for Co (Ⅱ) by dual-wavelength spectrophotometry. Trace cobalt in vitamin B12 and tea samples has been determined with satisfactory results.     

The development of silicate matrix phosphors with broad excitation band for phosphor-convered white LED

This paper briefly reviews the recent progress in alkaline earth silicate host luminescent materials with broad excitation band for phosphor-convered white LED. Among them, the Sr-rich binary phases （Sr, Ba, Ca, Mg）2SiO4：Eu^2＋ and （Sr, Ba, Ca, Mg）3SiO5：Eu^2＋ are excellent phosphors for blue LED chip white LED. They have very broad excitation bands and exhibit strong absorption of blue radiation in the range of 450-480 nm. And they exhibit green and yellow-orange emission under the InGaN blue LED chip radiation, respectively. The luminous efficiency of InGaN-based （Sr, Ba, Ca, Mg）=SiO4： Eu^2＋ and （Sr, Ba, Ca, Mg）3SiO5：Eu^2＋ is about 70-80 lm/W, about 95 %-105% that of the InGaN-based YAG ：Ce, while the correlated color temperature is between 4600--11000 K. Trinary alkaline earth silicate host luminescent materials MO（M=Sr, Ca, Ba）-Mg（Zn）O-SiO2 show strong absorption of deep blue/near-ultraviolet radiation in the range of 370-440 nm. They can convert the deep blue/near-ultraviolet radiation into blue, green, and red emissions to generate white light. The realization of high-performance white-light LEDs by this approach presents excellent chromaticity and high color rendering index, and the application disadvantages caused by the mixture of various matrixes can be avoided. Moreover, the application prospects and the trends of research and development of alkaline earth silicate phosphors are also discussed.     

Half-sandwich β-diketonato complexes of zirconium and their application as catalysts to ethylene polymerization

The bis(β-diketonato) Zr complexes CpZr(acac)2Cl (acac = acetylacetonato) (1) and Cp*Zr(acac)2Cl (2) can be synthesized by the reac-tion of Cp′ZrCl3(Cp′ = Cp or Cp*) with 2 equiv of lith-ium acetylacetonate. CpZr(acac)2Cl (1) can be quan-titatively prepared by treatment of Cp2ZrCl2 with ex-cess acetylacetone. The tris(β-diketonato) Zr com-plex CpZr(tfac)3 (tfac = trisfluoroacetylacetonato) (3) has been prepared by treatment of CpZrCl3 with so-dium trisfluoroacetylacetonate. The replacement of both chlorine atoms and one Cp group from zir-conocene dichloride by nonfluorinated diketone,acetylacetone,readily occurs at room temperature in triethylamine medium,offering the tris(β-diketonato) Zr complex CpZr(acac)3 (4). The complexes were characterized by 1H NMR spectroscopic methods. In addition,the molecular structures of complexes 3 and 4 have been determined by X-ray diffraction methods. When activated by excess methylaluminoxane (MAO),these complexes were active for ethylene polymerization,offering polyethylenes with high mo-lecular weights and narrow molecular weight distribu-tions. Complex 4 showed a very high ethylene po-lymerization activity of up to 7100 kg PE/mol Zr·h at 5 atm. Complexes 1 and 2 were also active for ethyl-ene/1-hexene copolymerization.     

Synthesis and characterization of organometallic macrocyclic rhodium (Ⅲ) complex with pyrazine ligands

The synthesis and structure research of organometal-lic macrocyclic complexes has been a very active field of modern chemistry [1—3]. In this field, Pd2+, Pt2+ complexes were first used as the building block, connected by het-erocyclic ligands, to construct metal macrocyclic com-pound[4,5]. The fac-Re(CO)5X (X = Cl, Br) fragment, for example, was shown to be a versatile building block for the synthesis of metallamacrocycles[6]. Some of this kind of molecule have been found applications in…     

The luminescence properties of Sr3Gd(BO3)3: Tb3+ phosphors under vacuum ultraviolet excitation

Tb3+-activated Sr3Gd(BO3)3 green phosphors were prepared by conventional solid-state reaction. The vacuum ultraviolet (VUV) excitation, photoluminescence (PL) and decay properties of the phosphors in the visible range were investigated. The excitation spectrum showed a strong broad band from 160 to 200 nm with a maximum at 183 nm which was adjacent to the VUV excitation light source of 172 nm. Under excitation at 172 nm, the optimum co-doping concentration of Tb3+ was 10 mol%, and the emission intensity of Sr3Gd0.9(BO3)3:0.1Tb3+ was comparable to that of commercial Zn2SiO4:Mn2+. The strongest emission peak of Sr3Gd0.9(BO3)3:0.1Tb3+ was at 543 nm with chromaticity coordinates of (0.2626, 0.4922) and a lifetime of 2.32 ms. The optical properties of the green phosphor Sr3Gd(BO3)3:Tb3+ make it suitable for use in Hg-free fluorescent lamps and plasma display panels.     

Transient spinodal decomposition during annealing of rapidly solidified Al-10Sr alloy

Rapidly solidified Al-10Sr alloy ribbons were prepared using a single roller melt spinning technique. The annealing process of the rapidly solidified Al-10Sr alloy has been carried out using differential scanning calorimetry (DSC). The microstructure of as-annealed Al-10Sr alloy has been characterized by transmission electron microscopy (TEM). The equilibrium AUSr phase is dominant in the as-annealed alloy. Besides the Al₄Sr phase, an AlSr phase is also found in the alloy isothermally annealed at 873 K for 90 min. Furthermore, a modulated nanostructure was observed in the alloy isothermally annealed at 873 K for 90 min. With further prolonged annealing time, however, the AlSr phase disappears in the as-annealed alloy. The dependence of particle size and growth rate on annealing time as well as the modulated structure shows that the occurrence of the AlSr phase may be due to the spinodal decomposition.     

Photoluminescence and cathodoluminescence properties of a novel CaLaGa307：Dy3＋ phosphor

A single host white emitting phosphor, CaLaGa3O7:Dy3+, was synthesized by chemical co-precipitation. Field emission scanning electron microscopy, X-ray diffraction, laser particle size analysis, and photoluminescence and cathodoluminescence spectra were used to investigate the structural and optical properties of the phosphor. The phosphor particles were composed of microspheres with a slight tendency to agglomerate, and an average diameter was of about 1.0 μm. The Dy3+ ions acted as luminescent centers, and substituted La3+ ions in the single crystal lattice of CaLaGa3O7 where they were located in Cs sites. Under excitation with ultraviolet light and a low voltage electron beam, the CaLaGa3O7:Dy3+ phosphor exhibited the characteristic emission of Dy3+ (4F9/2-6H15/2 and 4F9/2-6H13/2 transitions) with intense yellow emission at about 573 nm. The chromaticity coordinates for the phosphor were in the white region. The relevant luminescence mechanisms of the phosphor are investigated. This phosphor may be applied in both field emission displays and white light-emitting diodes.     

碱土金属卤磷酸盐光激励发光材料的研制

本文测定了在X射线辐照下碱土金属卤磷酸盐的光激励谱和光激励发射光谱。研究了助熔剂含量及改变碱土金属卤磷酸盐基质组成对样品的光激励发光强度的影响。找出了Eu~(2+)的最佳含量。确定了碱土金属卤磷酸盐中以Sr_3Ca_2(PO_4)_3Cl:Eu_(0.04)~(2+)的光激励发光最强。     

Photoluminescence and cathodoluminescence properties of CaLaGa<Subscript>3</Subscript>O<Subscript>7</Subscript>:Eu<Superscript>3+</Superscript> phosphors

The CaLaGa₃O₇:Eu³⁺ phosphor was prepared by a chemical co-precipitation method. Field emission scanning electron microscopy (FE-SEM), laser particle size analysis, X-ray diffraction (XRD), photoluminescence (PL), and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphor. The results revealed that the phosphor was composed of microspheres with a slight agglomerate phenomenon and was spherically shaped. The average grain size was about 1.0 μm. Eu³⁺ ions, as luminescent centers, substituted La³⁺ ions into the single crystal lattice of CaLaGa₃O₇ with the sites of C_s. Although the CL spectrum was greatly different from the PL spectrum, it had the strongest red emission corresponding to the ⁵D₀ →⁷F₂ transition of Eu³⁺. Under the excitation of UV light (287 nm) and electron beams (1.0–7.0 kV), the chromaticity coordinates of the phosphor were found to be in the nearly red and orange light regions, respectively.     

（Y，Zn，Sr）_3（P，VO_4）_2：Eu~（3＋），Bi~（3＋）的基质

研究了基质组成、化学键结构对荧光材料（Ｙ，Ｚｎ，Ｓｒ）３（Ｐ，ＶＯ４）２：Ｅｕ３＋，Ｂｉ３＋的发光性质和基质敏化的影响。实验表明在基质中引入Ｙ—Ｏ—Ｖ直线链，对基质的吸收和发射跃迁、能量传递有着良好的敏化作用。从理论上探讨了能量传递机理。     

Eu~(3+)激活的La_2Na_2Sr_6(PO_4)_6Br_2和Y_2Na_2Ca_6(PO_4)_6F_2晶体中的发光中心

采用高温固相法合成了La_2Na_2Sr_6(PO_4)_6Br_2和Y_2Na_2Ca_6(PO_4)_6F_2。X射线衍射分析证明它们都为单一物相。用Sr_(10)(PO_4)_6Br_2和Ca_(10)(PO_4)_6F_2同晶指标化法进行指标化,结果表明:它们都属六方晶系的磷灰石结构,空间群为P6_3/m。计算了它们的晶胞参数。以Eu~(3+)做结构探针,研究了Eu~(3+)所处晶格的点对称性。研究表明:在La_2Na_2Sr_6(PO_4)_6Br_2中Eu~(3+)占据4f格位,为C_3点群,而在Y_2Na_2Ca_6(PO_4)_6F_2中Eu~(3+)处于6h格位,为C_6点群。     

铽离子在氯磷酸锶镧中的发光和铈对它的敏化发光

本文报道了Tb~(3+)在氯磷酸锶镧中的发光性质、浓度猝灭和Ce~(3+)对Tb~(3+)的敏化发光。实验表明在该基质中Ce~(3+)对Tb~(3+)有良好的敏化作用。文中探讨了Ce~(3+)→Tb~(3+)的能量传递机理,证明为偶极子-偶极子相互作用的共振能量传递。     

Up-conversion luminescence of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4

The synthesis and up-conversion luminescent properties of YTaO4：Er^3＋ and YTaO4：Er^3＋/Yb^3＋ are reported for the first time. According to the measurement results of up-conversion spectra, Yb^3＋ co-doping can remarkably enhance the green （^2H11/2/^4S3/2→^4I15/2） and red （^4F9/2→^4I15/2） emissions, but depress the infrared emission （^4I9/2→^4I15/2）. With the increase of the Yb^3＋ concentration, the intensity of green emission increases, after that, when the Yb^3＋ concentration increases continuously, the intensity of green emission decreases, while those of the red and infrared emissions increase and decrease alternately. In addition, the up-conversion mechanisms of Er^3＋ doped and Er^3＋/Yb^3＋ co-doped YTaO4 are also discussed. It is found that the transform of up-conversion mechanism from two-step energy transfer to cooperating sensitization takes place when Yb^3＋ concentration is increased up to 12 mol%. With the further increase of Yb^3＋ concentration, the energy-back-transfer gradually becomes the dominant up-conversion mechanism, which results in the quenching of the green emission and slight increasing of the red and infrared emissions.     

Ca_8Mg(SiO_4)_4Cl_2:Eu~(2+),Mn~(2+)绿色荧光粉的光谱性质

在还原气氛下采用高温固相反应法合成了白光LED用绿色荧光粉Ca8Mg(SiO4)4Cl2:Eu2 ,Mn2 .在荧光粉的制备过程中,加入过量的CaCl2有利于提高荧光粉的发射强度.从实验结果可以看出,在Ca8Mg(SiO4)4Cl2基质中Eu2 -Mn2 间存在着能量传递,Mn2 的发射是来源于Eu2 的能量传递,能量传递的方式可能是共振传递.     

燃烧法合成xSrO.yAl2O3:Eu2+,Dy3+发光材料及其表征

用燃烧法成功制备了SrAl2O4Eu2+,Dy3+发光材料,样品无需球磨.用x射线粉末衍射和SEM表征材料的相组成、晶体结构和形貌;用激发和发光光谱和紫外-可见光谱表征材料的光学性质.结果表明当锶铝摩尔比Sr/A1=12时,发光基质主相为SrAl2O4,杂质相为Sr3Al206;随着Sr/Al比值减少,发光主相由SrAl204转为Sr7Al12O25,且发光强度增强,说明Sr7Al12O25发光强度大于SrAl204发光强度,Sr3Al206对发光性能有较大的负面影响.这种磷光体的主发射峰是位于570nm附近的带状谱.