共查询到20条相似文献,搜索用时 15 毫秒
1.
Wang Z Lil G Quan Z Kong D Liu X Yu M Lin J 《Journal of nanoscience and nanotechnology》2007,7(2):602-609
Nano-submicrostructured CaWO4, CaWO4 : Pb2+ and CaWO4 : Tb3+ particles were prepared by polyol method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), thermogravimetry-differential thermal analysis (TG-DTA), photoluminescence (PL), cathodo-luminescence (CL) spectra and PL lifetimes. The results of XRD indicate that the as-prepared samples are well crystallized with the scheelite structure of CaWO4. The FE-SEM images illustrate that CaWO4 and CaWO4 : Pb2+ and CaWO4 : Tb3+ powders are composed of spherical particles with sizes around 260, 290, and 190 nm respectively, which are the aggregates of smaller nanoparticles around 10-20 nm. Under the UV light or electron beam excitation, the CaWO4 powders exhibits a blue emission band with a maximum at about 440 nm. When the CaWO4 particles are doped with Pb2+, the intensity of luminescence is enhanced to some extent and the luminescence band maximum is red shifted to 460 nm. Tb(3+)-doped CaWO4 particles show the characteristic emission of Tb3+ 5D4-7FJ (J = 6 - 3) transitions due to an energy transfer from WO4(2-) groups to Tb3+. 相似文献
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The multicolor patterned luminescent films of CaWO(4):Eu(3+) (red), CaWO(4):Tb(3+) (green), and pure CaWO(4) (blue) on quartz substrates were fabricated by the facile and low-cost microcontact printing (μCP) method combining with the Pechini sol-gel route. On the basis of the μCP process, a hydrophobic self-assembled monolayer (SAM) was first created on the hydrophilic surface of quartz substrates by poly(dimethylsiloxane) (PDMS) mold printing, and then, the multicolor patterned luminescent films were selectively deposited on the hydrophilic regions via a spin coating process and heating treatment. The X-ray diffraction, optical microscopy, scanning electron microscopy, and photoluminescence (PL) spectra were used to characterize the structure and fluorescence properties of the corresponding samples. The results demonstrate that the μCP process can be used for patterning the inorganic phosphor materials and have potential for fabricating rare-earth luminescent pixels for the applications of display devices. 相似文献
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《Journal of Experimental Nanoscience》2013,8(4):301-311
Eu3+-doped GdVO4 has been synthesised via hydrothermal method by altering the hydrothermal temperature, reaction time and surfactant. The microstructure and morphology information of the phosphors were investigated via the techniques of X-ray powder diffraction and scanning electronic microscopy, which show that the phosphors wear tetragonal phase and the products present various regular morphologies under different reaction conditions such as bulk and nanoparticle. Moreover, the morphologies of the products have been controlled by altering reaction temperature. In addition, the surfactant was also included to control the morphologies of the products and the phosphors present different morphologies. All the phosphors exhibit the characteristic fluorescence of Eu ion (5D0 → 7F2 and 5D0 → 7F2). The electric dipole transition 5D0 → 7F2 of Eu3+ is dominant indicating that most sites of Eu3+ ions in GdVO4 have no inversion centre. Furthermore, we found that the reaction time and the morphologies have great influence on optical properties. 相似文献
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Spindle-like CaWO4:Sm3+ phosphors were prepared via a Polyvinylpyrrolidone (PVP)-assisted sonochemical process, and characterized by using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and photoluminescence spectroscopy (PL). The XRD results suggested that the prepared samples are single-phase. The FE-SEM images indicated that the prepared CaWO4:Sm3+ phosphors are composed of many spindles with maximum average diameter of 150 nm and maximum average length of 500 nm. Under 404 nm excitation, the characteristic emissions corresponding to 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2 and 11/2) transitions of Sm3+ in CaWO4 phosphors were observed. The color coordinates for 1 mol% Sm3+ doped CaWO4 phosphor were calculated to be (0.595, 0.404). The fluorescent concentration quenching of Sm3+ doped spindle-like phosphors was studied based on the Van Uitert's model, and it was found that the electric dipole–dipole (D–D) interaction is the dominant energy transfer mechanism between Sm3+ ions in the CaWO4:Sm3+ phosphors. The critical energy transfer distance was estimated. 相似文献
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Kong D Wang Z Lin C Yang P Quan Z Lin J 《Journal of nanoscience and nanotechnology》2008,8(3):1228-1233
In this paper, nanocrystalline YVO4:Eu3+ powders have been successfully synthesized via high-temperature solution-phase synthesis process. The nanocrystalline YVO4:Eu3+ particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV/Nis absorption spectra and luminescence spectra, luminescence decay curve and Fourier transform infrared (FT-IR), X-ray photoelectron spectra (XPS) respectively. The as-prepared nanocrystalline YVO4:Eu3+ particles are well crystallized with ellipsoidal morphology. The emission of YVO4:Eu3+ particles show emission originating from the 5D0 level, with 5D0-7F2 at 616 nm as the most prominent group. The excitation spectrum fits basically with the absorption spectrum from the vanadate ions. FT-IR and XPS spectra indicate that the surface ligands of nanocrystalline particles were oleic acid and oleylamine. The lifetime for the luminescence of Eu3+ in the as-prepared YVO4:Eu3+ samples are shorter than that of the bulk material due to the absorption of organic ligands on the nanoparticle surface. 相似文献
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Molten salt synthesis,characterization, and luminescence of SrWO4, SrWO4:Tb3+ and SrWO4:Eu3+ powders
Xiaoyu Sun Xiaodan Sun Xingang Li Jian He Binsheng Wang 《Journal of Materials Science: Materials in Electronics》2014,25(5):2320-2324
SrWO4, SrWO4:Tb3+, and SrWO4:Eu3+ powders were synthesized by a method of molten salt. XRD patterns showed that the synthesized powders have a pure tetragonal scheelite structure without the presence of deleterious phases. Scanning electron microscopy images show that powders are in the range of 20–35 nm. The emission spectrum of SrWO4 shows the emission peak in the blue spectral region. The excitation spectra of SrWO4:Tb3+ and SrWO4:Eu3+ show the energy transfer from WO4 2? group to Tb3+ and Eu3+ ions with a high efficiency. The emission spectrum of SrWO4:Tb3+ shows the green emission at 545 nm corresponding to the 5D4 → 7F5 transition of Tb3+. The emission spectrum of SrWO4:Eu3+ shows the red emission located at 612 nm corresponding to the 5D0 → 7F2 transition of Eu3+. The asymmetry ratio of SrWO4:Eu3+ is found to be 5.54, which indicates that the Eu3+ ions are located in a lower symmetric site. 相似文献
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Fengwen Kang Yihua Hu Li Chen Xiaojuan Wang Haoyi Wu 《Materials Science and Engineering: B》2013,178(7):477-482
The red afterglow phosphors of CaWO4 doped with Eu3+, Zn2+ or (and) Si4+ were prepared by solid state reaction. All crystalline phases were identified by the X-ray powder diffraction (XRD). The photoluminescence spectra and decay curves as well as thermoluminecence (TL) curves of all samples were also investigated. In comparison to CaWO4:Eu3+ phosphor, the luminescence and afterglow properties could be improved greatly after being doped with Zn2+ or (and) Si4+ ions. 相似文献
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Yu H Song H Pan G Qin R Fan L Zhang H Bai X Li S Zhao H Lu S 《Journal of nanoscience and nanotechnology》2008,8(3):1432-1436
This paper describes a procedure based on electrospinning for generating europium-doped yttrium vanadate (YVO4:Eu3+) nanofibers with diameters ranging from 30 to 50 nm. The YVO4:Eu3+ nanofibers were obtained through calcining precursory nanofibers, which were prepared through the electrospinning method. Suitable electrospinning parameters, such as concentration of PVP in solution, spinneret tip-to-collector plate distance (TCD), and applied voltage between spinneret and collector plate, are used to obtain thinner and more uniform precursory nanofibers of YVO4:Eu3+, which is important for preparing smaller diameter pure YVO4:Eu3+ nanofibers. The luminescent properties of the YVO4:Eu3+ nanofibers including excitation and emission spectra and fluorescence lifetime were studied. The excitation spectrum shows a broad band extending from 200 to 350 nm, which corresponds to the strong vanadate absorption in YVO4:Eu3+. The emission spectrum is dominated by the red 5D0 --> 7F2 hypersensitive transition of Eu3+. The fluorescence lifetime of Eu3+ 5D0 --> 7F2 (619 nm) is determined to be 493 micros at room temperature, which is basically in accordance with that in the bulk (521 micros). 相似文献
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The branch-shaped NaGdF4:Eu3+ nanocrystals (NCs) were synthesized by using polyvinylpyrrolidone (PVP) as a capping agent in ethylene glycol (EG) solution. The NCs were readily dispersed into water or ethanol to form a relatively stable suspension, which may facilitate their applications in biological fields. Meanwhile, the crystal structures of the NCs were tunable from the mixture of the α-(cubic) and β-(hexagonal) phases to the pure β-phase by varying the F?/Ln3+ molar ratio or the reaction temperature. The pure β-phase NCs were obtained at relatively high F?/Ln3+ molar ratio and reaction temperature. In addition, the Eu3+-doping concentration—dependent optical properties of the NaGdF4:Eu3+ NCs were investigated in detail. The result shows that the emissions from high energy level transitions (e.g., 5D1, 5D2, and 5D3) are significantly impaired with increasing the Eu3+-doping concentration due to the cross-relaxation process, and the emission at 612 nm is predominant since the doped Eu3+ ions locate in the crystal fields without inversion center. 相似文献
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Lizhu Tong Deming Liu Jianhui Shi Xuwei Yang Hua Yang 《Journal of Materials Science》2012,47(1):132-137
The multifunctional Fe3O4@Y2O3:Eu3+ nanocomposites were prepared by a facile solvothermal method with Fe3O4 nanoparticles as the core and europium-doped yttrium oxide (Y2O3:Eu3+) as the shell. It is shown that Fe3O4@Y2O3:Eu3+ nanocomposites have a strong photoluminescence and special saturation magnetization Ms of 6.1 emu/g at room temperature.
The effects of the magnetic field on the luminescence intensities of the nanocomposites are being discussed. The multifunctional
nanocomposites with magnetic resonance response and fluorescence probe properties may be useful in biomedical applications,
such as cell separation and bioimaging. 相似文献
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CaWO4:Eu3+ (Ca0.925Eu0.05WO4) and CaWO4 phosphors were synthesized by solid state method. Here, the pressure effect on the photoluminescence of CaWO4:Eu3+ has been investigated with a diamond anvil cell up to 20 GPa at room temperature. It is observed that pressure has a great influence on the fluorescence intensity and the energy levels. With increasing pressure, the spectral features shift towards lower energies, and the 7F1 multiplet will split into three Stark levels due to the removal of the degeneracy by the crystal-field interaction. In addition, the emission intensity of the 5D0 → 7F1 transition decreases significantly. Raman experiments further confirm the scheelite to wolframite structure transformation presents at around 10 GPa. Upon release of pressure, this high-pressure phase transforms back to the original scheelite phase, and continuously remains stable to ambient conditions. 相似文献
16.
Hongtao Yuan Yingjie Qiao Hua Yang 《Journal of Materials Science: Materials in Electronics》2014,25(9):4001-4003
YVO4:Eu3+ nanophosphors were prepared by a sol–gel method. The structure and luminescent properties of YVO4:Eu3+ nanophosphors are characterized by XRD and luminescent spectrophotometer. There are excellent luminescent properties for YVO4:Eu3+ nanophosphors. The nanophosphors are applied in bioapplications field. 相似文献
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Hongming Wu Hu Chen Yunfei Liu Yinong Lu Duoqing Zhang 《Journal of Materials Science: Materials in Electronics》2014,25(7):3109-3115
Uniform and well-crystallized NaLa(MoO4)2 microspheres were prepared by a facile microwave-assisted hydrothermal method at low temperature without any surfactants or templates. The as-prepared products were systematically characterized by powder X-ray diffractometer, scanning electron microscope, high resolution transmission electron microscope (HRTEM) and photoluminescence (PL) spectrometer. The results indicate that the phase, morphology, and size of the products can be tuned by altering reaction temperature and time. A possible formation mechanism of the microspheres was proposed based on the time-dependent experiments and HRTEM results, which contained an oriented attachment and Ostwald ripening process. Under ultraviolet excitation, the NaLa(MoO4)2:Eu3+ microcrystals exhibit strong red luminescence at 613 nm which attributes to 5D0 → 7F2 transition of Eu3+. The dependence of NaLa(MoO4)2:Eu3+ PL intensity on different morphologies have been investigated in detail. The results revealed that the PL intensity of NaLa(MoO4)2:Eu3+ microspheres is higher than that of polyhedrons and dendrites particles, and proved that the microspheres might have potential application in solid lighting technology. 相似文献
19.
Juan Wang Mirabbos Hojamberdiev Yunhua Xu Jianhong Peng 《Materials Chemistry and Physics》2011,125(1-2):82-86
YVO4:Eu3+ powders with different morphologies were fabricated by a simple hydrothermal method at 180 °C for 24 h in a wide pH range with the assistance of polyvinylpyrrolidone (PVP) as a nonionic surfactant. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). The obtained results showed that the pH value of synthesis solution played a key role in the formation of final products with different morphologies, such as, microspheres, irregular microspheres with grain-like nanoparticles, stone-like structures with regular short nanorods, and smooth rhombohedrons. The PL measurements revealed that the emission intensity of the samples was first decreased, and then increased with increasing the pH value due mainly to the increase in crystallinity and decrease in surface defects. 相似文献
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A novel precursor PMA–Si was synthesized by modifying 1,2,4,5-benzene-tetracarboxylic acid (PMA) with 3-aminopropyltriethoxysilane (APTES). Then the hybrids were prepared by PMA–Si coordinating to lanthanide ions (Eu3+ and Tb3+) in sol–gel process. In order to improve luminescent efficiency, 1,10-Phenanthroline (Phen) was introduced to the system as the second ligand. As-prepared compounds in sol condition were coated on quartz plates to form a layer of thin film, which was different from other similar hybrids. The properties of the hybrids were characterized by FT-IR, fluorescence spectra, TG and SEM. The results showed that the obtained materials enhanced thermal stability, mechanical resistances, waterproofness as well as machining properties. 相似文献