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ABSTRACT: The Sr2SiO4:Eu3+, Dy3+ phosphors for white light emitting diodes (LEDs) were synthesized by the sol-gel method. The microstructure and luminescent properties of the obtained Sr2SiO4:Eu3+, Dy3+ particles were well characterized. The results demonstrate that the Sr2SiO4:Eu3+, Dy3+ particles, which have spherical morphology, emitted an intensive white light emission under excitation at 386 nm. The phosphors show three emission peaks: the blue emission at 486 nm corresponding to the 4F(9/2)-6H(15/2) transition of Dy3+, the yellow emission at 575 nm corresponding to the 4F(9/2)-6H(13/2) transition of Dy3+, and the red emission at 615 nm corresponding to the 5D0-7F2 transition of Eu3+. At the same time, the effect of Eu3+ concentration on the emission intensities of Sr2SiO4:Eu3+, Dy3+ was investigated in detail. The phosphors used for white LEDs were obtained by combining near ultraviolet (NUV) light (386 nm) with Sr2SiO4:0.04Dy3+, 0.01Eu3+ phosphors with the characteristic of Commission Internationale de l'Eclairage (CIE) chromaticity coordinate (x, y) of (0.33, 0.34), and color temperature Tc of 5,603 K. In addition, the effect of the charge compensators (Li+, Na+, and K+ ions) on the photoluminescence (PL) emission intensities were studied.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9439-44. · 1.56 Impact Factor
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ABSTRACT: Ba3MgSi2O8:Eu2+, Mn2+ phosphors were synthesized by the sol-gel method and high temperature solid-state reaction method, respectively. XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), PL (photoluminescence spectra), and PLE (photoluminescence excitation spectra) were measured to characterize the samples. Emission and excitation spectra of our Ba3MgSi2O8:Eu2+, Mn2+ phosphors monitored at 441, 515, and 614 nm are depicted in the paper. The emission intensities of 441 and 515 nm emission bands increase with increasing Eu2+ concentration, while the peak intensity of the 614 nm band increases with increasing Mn2+ concentration. We conclude that the 515 nm emission band is attributed to the 4f(6)5d transition of Eu2+ ions substituted by Ba2+ sites in Ba2SiO4. The 441 nm emission band originates from Eu2+ ions, while the 614 nm emission band originates from Mn2+ ions of Ba3MgSi2O8:Eu2+, Mn2+. Nano-crystalline Ba3MgSi2O8:Eu2+, Mn2+ phosphors prepared by the sol-gel method show higher color rendering and better color temperature in comparison with the samples prepared by high temperature solid-state reaction method.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9829-32. · 1.56 Impact Factor
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ABSTRACT: Nano-sized Sr2MgSiO5:Eu2+, Mn2+ phosphor was synthesized by the sol-gel method. The preparation conditions of the precursor were determined. The effect of Eu2+ and Mn2+ content on the luminescence intensity was studied. X-ray diffraction (XRD), photoluminescence spectra (PL), and photoluminescence excitation spectra (PLE) were used to characterize the samples. The results showed that the excitation bands ranged from 250 to 450 nm, and their peaks positioned around 365 nm. The emission spectrum consists of three bands: blue, green, and red, respectively. The blue and green emission bands originate from the center of the Eu2+, while the red emission band is attributed to the energy transfer from Eu2+ to Mn2+. White light can be obtained by mixing the three emission colors. The experiment results show that the Sr2MgSiO5:Eu2+, Mn2+ is a single host phosphor with superior properties for use in white light emitting diodes (white LED).
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9833-5. · 1.56 Impact Factor
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ABSTRACT: Spherical Zn2 SiO4 : Eu3+ phosphors were prepared by a Pechini sol-gel process. The microstructure and luminescent properties of the obtained Zn2 SiO4 : Eu3+ particles were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) spectra. The results of SEM demonstrated that the Zn2 SiO4 : Eu3+ particles with a diameter about 1 -3microm, which have spherical morphology, emitted an intensive red light emission at 613 nm under excitation at 395 nm. Besides, the effects of the Eu3+ concentration, annealing temperature and charge compensators of Li+ ions on the PL emission intensities were investigated in detail. The investigation showed that the PL intensity increased with the annealing temperature increasing. At the same time, the PL intensity firstly increased and then decreased with the Eu3+ and Li+ concentration increasing.
Guang pu xue yu guang pu fen xi = Guang pu 04/2011; 31(4):890-3. · 0.84 Impact Factor
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ABSTRACT: To investigate the chemical constituents of Phyllanthus urinaria L.
Various chromatographic techniques were employed for the isolation and purification. The structure was elucidated by spectral analyses.
A novel ellagitannin named phyllanthusiin G was isolated, its structure was established as 1-O-galloyl-2-phyllanthoyl-3,6-(R)-HHDP-beta-D-glucose.
Phyllanthusiin G is a new compound.
Yao xue xue bao = Acta pharmaceutica Sinica 03/2004; 39(2):119-22.
