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Synthesis and photoluminescence properties of Ca_3R_(2–x)WO_9:xEu^(3+)(R=Y, Gd) phosphors

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Journal of Rare Earths 2015年第2期33卷 135-139页

作者：茹晶晶秦小焕颜桂炀陈建中 Department of Chemistry Ningde Normal University School of Chemistry and Pharmaceutical Sciences Guangxi Normal Univer-sity College of Chemistry and Chemical Engineering Fuzhou University

Ca3R2–xWO9：xEu^3＋（R=Y, Gd） red-emitting phosphors were prepared by solid state reactions. These samples were characterized by differential scanning calorimetry and thermogravimetry analysis（DSC-TGA）, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, photoluminescence（PL） and field emission scanning electron microscopy（FE-SEM） analyses. The optimum sintering temperature for these phosphors was 1100 ℃, and the optimum sintering time was 2 h. The optimum doped concentration of Eu^3＋ in Ca3Y2–xWO9：xEu^3＋ and Ca3Gd2–xWO9：xEu^3＋ were x=1.5 and x=1.1, respectively. These phosphors could be excited by near-UV light of 394 nm and blue light of 465 nm, and showed strong red emission line at 612 nm（^5D0→^7F2）, which indicated that Ca3R2–xWO9：xEu^3＋（R=Y, Gd） were promising red candidates for white LED.

关键词： tungstate rare earth luminescence LED

Influences of Co-Doping Cation on Properties of PWO∶F- Scintillating Crystal

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Journal of Rare Earths 2006年第Z1期24卷 169-171页

作者： Zhang Mingrong Zhang Chunsheng Fan Yuhong Ge Yuncheng Crystal Laboratory Beijing Glass Research Institute Beijing 100062 China Crystal Laboratory Beijing Glass Research Institute Beijing 100062 China Crystal Laboratory Beijing Glass Research Institute Beijing 100062 China Crystal Laboratory Beijing Glass Research Institute Beijing 100062 China

Whereas the light yield of PWO crystal can be significantly improved by doping with either of F- and Sb3+, effects of heavily co-doping with by F-+Sb3+, F-+Ca2+, and F-+Ca2++Sb3+, respectively, on the properties of PWO scintillation crystals, including optical transmission, luminescence and light yield were studied. The result indicates that co-doping with three dopants, F-+Ca2++Sb3+, is a more effective measure than doping with single dopant F- for the improvement of scintillation properties of PWO crystals, including light yield.

关键词： lead tungstate scintillation crystal light yield doping

Unusual Luminescence of Ca8[Al12O24]（WO4）2: Tb3+

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Chinese Journal of Chemistry 2004年第5期22卷 437-440+407页

作者：刘胜利苏锵 School of Chemistry and Chemical Engineering Hunan University of Science and Technology Xiangtan Hunan 411201 China Key Laboratory of Rare Earth Chemistry and Physics Changchun Institute of Applied Chemistry Chinese Academy of Sciences Jilin 130022

The luminescence properties of aluminate sodalite Ca8[Al12O24](WO4)2 (CAW) undoped and doped with Tb3+ are reported and discussed. At room temperature the emission of tetrahedral 2-4WO in CAW showed an abnor-mally small Stokes shift (9060 cm-1), which is related to the crystal structure of CAW. A strong absorption band in the excitation spectrum of the Tb3+-activated CAW is ascribed to the absorption of the charge transfer state Tb4+- W5+, into which the excitation resulted in the efficient emission from the 5D4 level of Tb3+, but not from the 5D3 level.

关键词： aluminate sodalite terbium ion tungstate charge transfer Stokes shift luminescence

New developments in nonlinear optical crystals of molybdate and tungstate

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New developments in nonlinear optical crystals of molybdate ...

Unusual Luminescence of Ca_8[Al_(12)O_(24)](WO_4)_2: Tb^(3+)

中国化学会第九届全国无机化学学术会议

作者： Xutang Tao Zeliang Gao Youxuan Sun Xiangxin Tian Qian Wu State Key Laboratory of Crystal Materials Shandong University

A series of new nonlinear crystals based on molybdates that containing Tellurium atoms have been grown by flux method and their linear and nonlinear optical properties have been studied. Polycrystalline Ba Te Mo2O9（BTM） samples were synthesized using the traditional solid state reaction techniques. The results indicate temperatures below 570 °C favored production of β-BTM, while higher temperatures led to production of α-BTM. The phase relationship between the two phases has been studied. Since both β-BTM and α-BTM melt incongruently, appropriate fluxes should be introduced to decrease the crystal growth temperature. After a great amount of attempts, the Te O2-Mo O3 flux system was adopted to grow large crystals. The obtained crystals are shown in Fig. 1. The second order nonlinear optical properties of β-BTM were studied by means of the Marker fringe technology and the phase matching method. The values and relative signs of the second order nonlinear optical coefficients were obtained, with the largest one being d31 = 9.88 pm/V. At 1064 nm, the crystal can realize both type I and type II phase matching, and the effective nonlinear coefficient is 10.3 pm/V for phase matching II in the xoy plane.

关键词： Molybdate tungstate phase transfer nonlinear optical

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Chinese Journal of Chemistry 2004年第5期22卷 437-440页

关键词： aluminate sodalite terbium ion tungstate charge transfer Stokes shift luminescence

Microwave Synthesis and Photoluminescence Properties of BaWO<sub>4</sub>of Homogeneous Double Cone Structure

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Journal of Materials Science and Chemical Engineering 2017年第4期5卷 64-69页

作者： Dengfeng Wu Shihao Luo Shuibin Yang Xuehong Liao Hubei Key Laboratory for Processing and Application of Catalytic Materials The College of Chemical Engineering Huanggang Normal University Huanggang China

Barium tungstate of homogeneous double cone structure was synthesized by microwave synthesis method with sodium tungstate, barium nitrate as raw materials, polyethylene glycol (PEG2000) as surfactant. The as-prepared sample was characterized by X-ray diffraction (XRD), scanning electron micrograph (SEM) and photoluminescence spectrum (PL). The XRD Pattern showed that the samples are scheelite structure of BaWO4. The SEM image showed that the majority of as-prepared sample is a double cone structure, and some particles are attached to it. The length of most of the double cone is 10 μm. PL spectra showed that as-prepared sample had strong luminescence properties, and it had purity green emission at 495 nm and 521 nm. The effects of different surface active agent on the luminescence properties were studied. The results showed that when PEG2000 is as surfactant, the luminescence intensity of as-prepared sample was maximum.

关键词： Barium tungstate Nanomaterial Microwave Synthesis Photoluminescence

Alternative Nitrogenases in Anabaena variabilis: The Role of Molybdate and Vanadate in Nitrogenase Gene

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Advances in Microbiology 2013年第6期3卷 87-95页

作者： Teresa Thiel Brenda S. Pratte Department of Biology University of Missouri-St. Louis St. Louis USA

Anabaena variabilis ATCC 29413 has two distinct nitrogenases that function in heterocysts, a conventional Mo-nitrogenase and an alternative V-nitrogenase. Synthesis of these two enzymes was repressed in cells growing with a source of fixed nitrogen, such as ammonium;however, the V-nitrogenase was also repressed by Mo. Expression of the V-nitrogenase which was not affected by V and expression of the Mo-nitrogenase was not affected by the presence or absence of either Mo or V. In the absence of both Mo and V in an environment lacking fixed nitrogen, cells became starved for both metals;however, low levels of nitrogen fixation and slow growth persisted. A mutant lacking the V-nitrogenase was still able to grow very slowly in Mo-and V-free medium;however, loss of the Mo-nitrogenase in a nifDK1 mutant abolished the residual growth, suggesting that only the Mo-nitrogenase functioned under these conditions to support slow growth. The addition of vanadate, molybdate, or tungstate, which is transported by the molybdate transporter, to cells starved for these metals resulted in an increase in nitrogenase activity within two hours after the addition of the metal and this increase required new protein synthesis. While tungstate functioned about as well as vanadate in supporting acetylene reduction, the cells were not able to grow any better with tungstate than with no added metal. A mutant lacking the V-nitrogenase showed no increase in nitrogenase activity upon addition of tungstate, suggesting that the V-nitrogenase was able to incorporate tungstate. tungstate was able to substitute for molybdate in repressing transcription of a Mo-transport gene, but it did not repress transcription of the vnfH gene, which was repressed by Mo. The availability of Mo and V plays an important role in controlling whether the Mo-or the V-nitrogenase is used for nitrogen fixation.

关键词： Cyanobacteria V-Nitrogenase Molybdate Vanadate tungstate

Mortar-Pestle and Microwave Assisted Regioselective Nitration of Aromatic Compounds in Presence of Certain Group V and VI Metal Salts under Solvent Free Conditions

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International Journal of Organic Chemistry 2012年第3期2卷 233-247页

作者： Sariah Sana Kancharla Rajendar Reddy Kamatala Chinna Rajanna Marri Venkateswarlu Mir Moazzam Ali Department of Chemistry Osmania University Hyderabad India

Solvent – free Mortar-pestle (grinding) and microwave-assisted nitration reactions (MWANR’s) underwent smoothly in the presence of group V and VI metal salts with high regio-selectivity for anilides, moderately- and non-activated aro-matic compounds. The reactions were conducted under solvent-free conditions, which afforded good to excellent yields. The observed reaction times in MW assisted conditions are in the range of only few minutes.

关键词： Nitration Mortar-Pestle Microwave-Assisted Nitration Ammonium Molybdate Potassium Chromate So-dium tungstate Bismuth Nitrate Sodium Bismuthate

Visible Light Photocatalytic Degradation of Methylene Blue and Malachite Green Dyes with CuWO<sub>4</sub>-GO Nano Composite

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Modern Research in Catalysis 2018年第2期7卷 17-34页

作者： Sunitha Medidi Sowmyasree Markapurapu Mastan Rao Kotupalli Rama Krishna Reddy Chinnam Venkata Mahalakshmi Susarla Hima Bindu Gandham Paul Douglas Sanasi Department of Engineering Chemistry AU College of Engineering Andhra University Visakhapatnam India SKR College for Women Rajamahendravaram India SKR College for Women Rajamahendravaram India Department of Chemistry University of Dodoma Dodoma Tanzania

Copper tungstate-Graphene Oxide nano composites have been successfully applied as excellent catalysts for the photocatalytic degradation with Methylene blue and Malachite green dyes under visible light irradiation. A facile?solid state metathesis synthesis of copper tungstate (CuWO4) followed by ball milling and subsequent preparation of copper tungstate-graphene oxide?(CuWO4-GO) nano composite using a colloidal blending process and its application as a visible light photocatalyst for the degradation of Malachite green and Methylene blue dyes. The morphology and composition of copper tungstate (CuWO4) nano composite have been characterized using X-Ray Diffraction (XRD), UV-Visible Diffuse Reflectance Spectra (UV-DRS), Raman Spectra, Field Emission Scanning Electron Microscopy (FESEM)-EDS and UV Visible Spectroscopy. It shows a band gap value of 2.13 eV, an increase in range and intensity of light absorption and the reduction of electron-hole pair recombination in CuWO4 with the introducing of GO on to it.

关键词： Copper tungstate Graphene Oxide Metathesis Methylene Blue Malachite Green Visible Light Photodegradation