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225 results on '"Qiao, Chun Feng"'

22. Synthesis and Spectroscopic Properties of LiY(WO 4)(MoO 4): Eu 3+ Red Phosphors for White LEDs

Author

Tong Hui Zhou, Xian Ju Zhou, Ying Mao Li, and Qiao Chun Feng

Subjects
Materials science, business.industry, Doping, Analytical chemistry, Phosphor, General Medicine, Molybdate, law.invention, chemistry.chemical_compound, Optics, chemistry, Impurity, law, Calcination, Luminescence, Dispersion (chemistry), business, Light-emitting diode
Abstract

A series of LiY(WO4)(MoO4):Eu3+red phosphors have been synthesized by solid state reactions at high temperatures. The effect of Eu3+doping concentration, calcination temperature, reaction time and ratio of W/Mo on the optical properties of the red phosphors are studied and optimized. The phase impurity and spectroscopic properties are characterized by X-Ray Diffraction (XRD) and Photo-Luminescence (PL) spectra respectively. It is found that all the samples can be excited efficiently both by near ultraviolet light (395 nm) and blue light (464.5 nm), which match well with the emission of GaN based LED chips. The luminescent intensity maximizes for the sample of Eu3+5 mol % in doping concentration (replacing Y) and W:Mo=1:1 in mole with calcinated of 750°C. To improve the dispersion and change the morphology of the phosphor powders, the sample is post-processed through ultrasonic dispersing method and the luminescent intensity of the post-treated sample increases by nearly 20%.

Published
2011

24. [Electronic spectra and energy levels analysis of Ho3+ in Cs2NaYF6]

Author

Xian-ju, Zhou, Chong-dan, Ren, Bin, Luo, and Qiao-chun, Feng

Abstract

The electronic spectra and energy levels of Ho3+ in Cs2NaYF6 were studied on basis of rare earth (RE) spectrum, quantum mechanics and crystal field theory. Detailed analysis on electronic absorption spectra at temperatures down to 10 K in the range of 4600-24,000 cm(-1) was carried out. The transitions, with zero phonon lines (ZPL) and abundant vibronic sidebands, from ground states to different excited states such as 5I(J); (J = 7, 6, 5, 4), 5F(S) (S = 5, 4, 3), 5G(P) (P = 6, 5) and (3)K8 were clearly observed. All the transitions have been assigned and 50 experimental crystal field levels have been obtained. The dataset has been investigated by standard f-shell program, which gave out the calculated energy levels and the corresponding empirical Hamiltonian parameters. The comparison of the energy levels and Hamiltonian parameters was made with that of Cs2NaYCl6 : Ho3+ as well.

Published
2010

27. Bioassay-Guided Isolation of Xanthones and Polycyclic Prenylated Acylphloroglucinols from Garcinia oblongifolia

Author

Huang, Sheng-Xiong, Feng, Chao, Zhou, Yan, Xu, Gang, Han, Quan-Bin, Qiao, Chun-Feng, Chang, Donald C., Luo, Kathy Qian, Xu, Hong-Xi, Huang, Sheng-Xiong, Feng, Chao, Zhou, Yan, Xu, Gang, Han, Quan-Bin, Qiao, Chun-Feng, Chang, Donald C., Luo, Kathy Qian, and Xu, Hong-Xi

Abstract

Bioassay-guided fractionation of the acetone extract of the bark of Garcinia oblongifolia has resulted in the isolation of three new xanthones, oblongixanthones A-C (1-3), three new polyprenylated benzoylphloroglucinols, oblongifolins E-G (4-6), and 12 known compounds. Oblongifolins 1 (5) and J (6) are the first natural products that have similar structural features to those of two known oxidation products of garcinol. The structures of the new compounds 1-6 were characterized by spectroscopic data interpretation. All isolates were assayed for their apoptosis-inducing effects against HeLa-C3 cells. Oblongifolin C (16) was found to be the most potent apoptotic inducer of the compounds evaluated.

Published
2009

28. Polyprenylated Xanthones from Garcinia lancilimba Showing Apoptotic Effects against HeLa-C3 Cells

Author

Han, Quan-Bing, Tian, Hong-Lei, Yang, Nian-Yun, Qiao, Chun-Feng, Song, Jing-Zheng, Chang, Donald C., Luo, Kathy Q., Xu, Hong-Xi, Han, Quan-Bing, Tian, Hong-Lei, Yang, Nian-Yun, Qiao, Chun-Feng, Song, Jing-Zheng, Chang, Donald C., Luo, Kathy Q., and Xu, Hong-Xi

Abstract

Three new prenylated xanthones, 1-3, along with ten known compounds, were isolated from the stem bark of Garcinia lancilimba. Their structures were elucidated by extensive spectroscopic analysis, including 1D- and 2D-NMR spectra, as well as HR-MS experiments. Some of these compounds showed apoptotic effects or growth-inhibition effects against HeLa cells expressing a caspase sensor protein.

Published
2008

29. Bioassay and Ultraperformance Liquid Chromatography/Mass Spectrometry Guided Isolation of Apoptosis-Inducing Benzophenones and Xanthone from the Pericarp of Garcinia yunnanensis Hu

Author

Xu, Gang, Feng, Chao, Zhou, Yan, Han, Quan-Bin, Qiao, Chun-Feng, Huang, Sheng-Xiong, Chang, Donald C., Zhao, Qin-Shi, Luo, Kathy Q., Xu, Hong-Xi, Xu, Gang, Feng, Chao, Zhou, Yan, Han, Quan-Bin, Qiao, Chun-Feng, Huang, Sheng-Xiong, Chang, Donald C., Zhao, Qin-Shi, Luo, Kathy Q., and Xu, Hong-Xi

Abstract

Bioassay and ultraperformance liquid chromatography/photodiode array/mass spectrometry (UPLC/PDAMS) guided isolation of the apoptosis-inducing active metabolites on HeLa-C3 cells from the pericarp of Garcinia yunnanensis (Guttiferae) yielded five active compounds, including the new garciyunnanins A (1) and B (2). The structures of the compounds were elucidated by comprehensive nuclear magnetic resonance and mass spectrometry analysis. Garciyunnanin B (2), featured with a natural tetracyclic xanthone skeleton derived from a polyisoprenylated benzophenone, is structurally interesting since it can be seen as an evidence of the previously described cyclization of garcinol by 2,2-diphenyl-1-picrylhydrazyl (DPPH). Garciyunnanin A (1) contains a 3-monohydroxy benzophenone skeleton, which is rarely found in Garcinia species. Both new compounds induce HeLa-C3 cells into apoptosis after 72 h of incubation at 15 mu M. It is noteworthy that oblongifolin C (4), the major constituent of this plant, has proved to be the most active one among the isolates for inducing apoptotic cell death in cervical cancer derived HeLa-C3 sensor cells.

Published
2008

44. Bioassay and Ultraperformance Liquid Chromatography/Mass Spectrometry Guided Isolation of Apoptosis-Inducing Benzophenones and Xanthone from the Pericarp of Garcinia yunnanensis Hu

Author

Xu, Gang, primary, Feng, Chao, additional, Zhou, Yan, additional, Han, Quan-Bin, additional, Qiao, Chun-Feng, additional, Huang, Sheng-Xiong, additional, Chang, Donald C., additional, Zhao, Qin-Shi, additional, Luo, Kathy Q., additional, and Xu, Hong-Xi, additional

Published
2008
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