Papers by Author: Yong Sheng Wang

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Authors: Li Er Deng, Yong Sheng Wang, Ming Fu
Abstract: The ordered colloidal crystals were prepared by sedimentation of a solution of silica colloidal spheres of 298nm. Colloidal crystals were obtained after evaporation at 50°Cfor eight days while solution evaporates. These colloidal crystals were used to be templates and MMA was filled in the gap of silica spheres. SiO2/PMMA structures with a overlayer of PMMA were obtained by polymerization reaction carried out at 80°C for 24 h. After etched with the hydrofluoric acid (HF) for 24h, a piece of bluish violet film can be obtained. The film is flexible and free-standing and is enough tough to be curled to various shape. This kind of film can extend the usage of macroporous structures and have various potential applications in flexible photoelectronic device.
Authors: Da Wei He, Xin Rong Zhou, Yong Sheng Wang
Abstract: A series of phosphor of (MxMg1-x)2SiO4: Dy3+, Eu3+ (M=Ca, Sr, Ba) were synthesized by high temperature solid-state reaction method and studied. The structure and emission spectrum excited by near violet light were investigated. The excitation spectra of single-doped (MxMg1-x)2SiO4: Dy3+ show strong absorption near 322nm, 347nm, 362nm and 391nm due to 6H15/2→4I9/2, 6H15/2→6P5/2, 6H15/2→4F7/2, 6H15/2→4G11/2 transition of Dy3+. The emission light is at about 469nm, 474nm, 483nm and 494nm under 391nm UV excitation. In order to obtain white light emission, (MxMg1-x)2SiO4: Dy3+, Eu3+ (M=Ca, Sr, Ba) were prepared to enhance the red light emission.
Authors: Da Wei He, Fang Shen, Xin Li, Peng Zhi Lu, Yong Sheng Wang
Abstract: The excitation spectrum of BaZr(BO3)2:Eu3+ is composed of two broad bands. One band in the range from 120 nm to 170 nm is attributed to the borate groups, and the other band at 230 nm is due to the charge-transfer state (CTS) of the Eu3+ ion. The excitation spectrum of BaZr(BO3)2:Tb3+consists of one broad band in the range from 120 nm to 170 nm and the bands peaking at 226 nm, 245 nm and 272 nm respectively. The former is also attributed to the absorption of the BO3 groups. The latter correspond to the 4f8-4f75d transition of Tb3+.Main peak of the host absorption moves about 30 nm to high energy region as Sr2+ replaces Ba2+ partially.
Authors: Peng Zhi Lu, Da Wei He, Xin Li, Yong Sheng Wang
Abstract: New phosphors of Tm3+ doped Re2SiO4 (Re=Mg, Ba, Sr) were prepared by the solid-state reaction and their luminescent properties were investigated. X-ray powder diffraction analysis confirmed the formation of Re2SiO4: Tm3+ (Re=Mg, Ba, Sr). The excitation spectra indicated that this phosphor can be effectively excited by 161nm. It consists of peaked at 175nm and a broad excitation band from 184nm to 300nm, corresponded to the absorption of the host lattice and the O−Tm3+ charge transfer transitions. The emission peaks at about 357nm, 459nm, 485nm is separately corresponds to the 1D2 → 3H6, 1D2 → 3H4, 1G4 → 3H6 transitions of Tm3+. As the radius of alkali earth ion in Re site increases, the main emission peaks changed to 478nm from 459nm.
Authors: Cheng Zhu Lu, Jung Yohn Cho, Ho Jung Chang, Sang Woo Joo, Yong Sheng Wang
Abstract: We synthesized ZnO nanocrystal colloids adopting sol-gel method using zinc acetate dehydrate as precursor, and prepared ZnO films on glass substrates by a spin-coating technique. The effect of annealing temperature on the structure, optical and electrical properties has been studied. The crystallinity and morphologies were improved by the annealing. All film samples show high transmittance of above 80% in the wavelength ranging from 400nm to 1000nm. A minimum resistivity of 5.5x10-3 􀀀 cm was obtained for the film annealed at 500oC. The crystallinity, oxygen vacancies, and nanocrystalline boundaries seems likely to be crucial factors for these properties
Authors: Chun Xiu Zhang, Zhi Qun He, Jia Ling Pu, Jun Jie Wang, Yong Sheng Wang, Zhong Xiao Li, Shi Ye
Abstract: A novel discotic triphenylene derivative bearing one triphenylene discogen as core and three cyano-biphenyl moieties was synthesized and its thermal behavior was studied using polarizing optical microscope, differential scanning calorimeter and X-ray diffraction. It was found that this molecule containing [decylene?] spacers showed nematic phase. After being mixed with methyl methacrylate (MMA), the discogen showed nematic phase at the mesophase temperature range (64~85 °C) and oriented spontaneously in the mixture after annealing for 2 hours in the mixture. The orientation can be stabilized by the polymerization of MMA. The orientation can be fixed by the polymerization of MMA. It was treated directly on glass substrate, which surface did not treat by polyimide film and confirmed the orientation was proved by X-ray diffraction. This offers If the alignment of the discotic molecules can be freely controlled and fixed, a useful mean to produce new area of optically anisotropic film will be produced with this material.
Authors: Xin Li, Da Wei He, Peng Zhi Lu, Yong Sheng Wang
Abstract: A series of phosphor of MBPO7:Tm3+, and MBPO7:Tm3+, Gd3+ (M= Mg, Sr, Ca) were prepared and studied. The XRD data showed Tm3+, Gd3+ didn’t affects the lattice parameters. Excitation spectra exhibited high absorption in vacuum ultraviolet (VUV) region. There existed strong emission peaking at 453nm and 363nm correspond to the 1D2 →3HJ (J=4, 6) emission transition of Tm 3+ when excited under VUV. With the changes of cation in the samples, the excitation spectra changed greatly, and lead a great change in its emission spectra. The crystal lattice parameters affect the ratio of intensity of the peak at 454nm and 312nm.
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