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FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C5H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
;
Chen, Hui-Fen
;
Camacho, Cristopher
;
Witek, Henryk A.
;
Hsu, Sheng-Chuan
Photolysis of methane dispersed (1/1000) in solid Ne at 3 K with vacuum-ultraviolet light from a synchrotron produced infrared absorption lines of several products, including new lines at 3319.3 and 1955.5 cm(-1). Based on experiments with isotopic labeling and results of quantum-chemical calculations, these lines are assigned to the C-H stretching and C=C stretching modes, respectively, of interstellar molecule linear C5H radicals.
Synthesis and characterization of highly luminescent CuInS2 and CuInS2/ZnS (core/shell) nanocrystals
(2008-12-01)
Kuo, Kuan-Ting
;
Chen, San-Yuan
;
Cheng, Bing-Ming
;
Lin, Chin-Ching
;
材料科學與工程學系
High-quality CuInS2/ZnS (core-shell) nanocrystals (NCs) were synthesized via a colloidal solvent process and characterized for their optical properties by UV-vis, room temperature solution photoluminescence (PL) spectroscopy, and further obtained powders were characterized by X-ray microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS). diffraction (XRD), transmission electron The obtained CIS and CIS/ZnS core/shell NCs are quasimonodisperse with an average particle size of 2.4 and 4.6 nm, respectively. All of the as-synthesized NCs can be well dispersed in toluene or hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for CIS/ZnS core/shell NCs) under UV excitation. The growth of a ZnS shell on CIS NCs, that is, the formation of CIS/ZnS core/shell NCs, resulted in an impact enhancement in the PL intensity compared to that of bare CIS NCs due to the eliminated surface defects and the reduced lattice mismatch between the core and shell materials. A dramatic increase of the PL intensity can be obtained from the ZnS-capped CIS with respect to that of the bare CIS NCs. (C) 2008 Elsevier B.V. All rights reserved.
Blue/near UV light emission from hybrid InN/TiO2 nanoparticle films
(2011-01-01)
Wu, Chih-Wei
;
Lu, Chih-Wei
;
Lee, Yuan-Pern
;
Wu, Yu-Jong
;
Cheng, Bing-Ming
We report on the enhancement of photoluminescence (PL) from anatase TiO2 thin films covered by InN nanoparticles prepared using plasma enhanced chemical vapor deposition (PECVD). The SEM images and X-ray diffraction spectra illustrate the strong interaction between the InN particles and the TiO2 films. UV-Vis absorption spectra indicate that the InN particles have an increased absorption in the visible light region and may sensitize the TiO2 films. The strong PL band observed in the anatase TiO2 thin films with the addition of InN may have been due to an increased localization of impurities and/or defect-trapped excitons.
Charge-Transfer Luminescence and Energy Transfer in Eu2+-Doped Barium Zirconosilicates
(2011-01-01)
Wang, De-Yin
;
Wang, Ling-Li
;
Lee, Te-Ju
;
Chen, Teng-Ming
;
Cheng, Bing-Ming
Although zirconates are known to show ultraviolet luminescence under X-ray excitation, few have studied the vacuum ultraviolet (VUV) excited luminescence of zirconate compounds. We have investigated the VUV-excited luminescence of zirconate in BaZrSi3O9 and Ba2Zr2Si3O12 using synchrotron radiation, and examined the possibility of sensitizing Eu2+ by hosts that contain zirconate. Upon VUV excitation, BaZrSi3O9 and Ba2Zr2Si3O12 show self-activated emission peaking at 285 nm and 334 nm, which are assigned to Zr4+-O2- charge transfer (CT) luminescence. The evidence for the occurrence of Zr4+-O2- charge transfer in BaZrSi3O9 and Ba2Zr2Si3O12 was further supported by density of state (DOS) calculation. Energy transfer from host excitation (similar to 172 nm) to Eu2+ was observed in BaZrSi3O9:Eu2+ and Ba2Zr2Si3O12:Eu2+, showing that host sensitization of Eu2+ occurs in these materials. Despite that the host emission overlaps with the Eu2+ 4f-5d absorption band significantly, host -to-Eu2+ energy transfer in Ba2Zr2Si3O12:Eu2+ was found to be less efficient than that in BaZrSi3O9:Eu2+ and Eu2+ luminescence was found to be inferior in Ba2Zr2Si3O12:Eu2+. These observations are ascribed to a smaller Zr-O-Ba(Eu) angles and a lower Eu2+-Zr4+ metal-to-metal charge transfer energy in Ba2Zr2Si3O12:Eu2+. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.008112jes] All rights reserved.
Switchable structural modification accompanying altered optical properties of a zwitterionic polysquaraine
(2010-11-01)
Lu, Hsiao-Chi
;
Whang, Wha-Tzong
;
Cheng, Bing-Ming
;
材料科學與工程學系
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Department of Materials Science and Engineering
Active metals induce a variation of the conformation of zwitterionic conducting polymer poly(3-octylpyrrole)squaraine in solution. Evidence from infrared, visible and photoluminescent spectra and from small-angle X-ray scattering profiles unambiguously confirms the isomerization of this polysquaraine induced by the surfaces of active metals. Unlike the irreversible change induced by cations in solution, the folded conformation induced by active metals reverts to its original structure on eliminating contact between the metals and the solution. Accompanied by altered optical properties, this reversible structural modification of the zwitterionic polysquaraine induced by active metals represents a new chemical and physical process. (C) 2010 Elsevier B.V. All rights reserved.
BaMgAl10O17 : Eu blue phosphors with MgO coating and microwave irradiation
(2008-02-01)
Kuo, Kuan-Ting
;
Lee, Shu-Ping
;
Chen, San-Yuan
;
Cheng, Bing-Ming
;
Lu, Hsiao-Chi
Europium-activated barium magnesium aluminate (BaMgAl10O17:Eu (BAM)) phosphor particles were modified by surface coating with MgO using a polyol method. The photoluminescence (PL) properties of the MgO-coated BAM phosphors showed slightly improved blue-emission intensity compared to the unmodified ones, and reached a stronger peak intensity with 5.25% MgO coating, under vacuum ultraviolet (VUV) 147 nm excitation. Upon microwave irradiation on the MgO-coated BAM phosphors, the PL properties of the MgO-coated phosphors exhibited a much enhanced relative PL ratio, and a maximum relative PL ratio can be achieved when as high as 10.5% MgO was deposited on the phosphor surface. However, for mechanically ground phosphor powder, it was found that although the intensity of the MgO-coated BAM turned stronger with increasing MgO concentration under microwave irradiation, the purity of the resulting luminescence was slightly disrupted by the presence of a new peak near 470 nm, corresponding to BaMg3Al14O25 compound. (C) 2007 Elsevier Ltd. All rights reserved.
Effect of microwave irradiation on surface characteristics and luminescent properties of BaMgAl10O17 : Eu blue phosphor
(2008-02-01)
Kuo, Kuan-Ting
;
Lee, Shu-Ping
;
Chen, San-Yuan
;
Cheng, Bing-Ming
;
Lu, Hsiao-Chi
BaMgAl10O17:Eu (BAM) has been an excellent blue-emitting phosphor due to its outstanding luminescence efficiency and purity for plasma display panels. An attempt of employing microwave irradiation to modify the surface properties including morphology and crystallinity of BAM powder was performed in this work. X-ray powder diffraction (XRD) analysis and scanning electron microscopy (SEM) images show that the blue-emitting phosphors after microwave irradiation treatment exhibit better crystallinity and smoother surface. Furthermore, the vacuum ultraviolet photoluminescence spectra show that the luminescent intensity of BAM phosphors can be effectively enhanced by a factor of six times under microwave irradiation treatment. The enhanced luminescent properties can be closely related to the surface modification and reduced defects of the BAM blue-emitting phosphors. (C) 2007 Elsevier Ltd. All rights reserved.
Reversible isomerization of a zwitterionic polysquaraine induced by a metal surface
(2011)
Lu, Hsiao-Chi
;
Whang, Wha-Tzong
;
Cheng, Bing-Ming
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The variation of visible and IR absorption spectra and of small-angle X-ray scattering of poly(3-octylpyrrole)squaraine in trichloromethane solution indicates that, for this zwitterionic conducting polymer (CP), a reversible change of conformation is induced by contact of the solution with the surface of an active metal. The structure of the target polymer might switch from being linear to being folded. For a copper surface, the activation energy of isomerization between the two forms, whatever their nature, is 18.9 +/- 0.7 kJ mol(-1), whereas for the reverse process the activation energy is 38 +/- 6 kJ mol(-1). In a folding transformation, formation of intramolecular hydrogen bonds might play a key role. This observation of a reversible conformation for a zwitterionic polymer induced by a metallic surface provides an impetus to investigate both such a structural modification of other CP and applications of this phenomenon.
Blue/near UV light emission from hybrid InN/TiO(2) nanoparticle films
(2011-01-01)
Wu, Chih-Wei
;
Lu, Chih-Wei
;
Lee, Yuan-Pern
;
Wu, Yu-Jong
;
Cheng, Bing-Ming
We report on the enhancement of photoluminescence (PL) from anatase TiO(2) thin films covered by InN nanoparticles prepared using plasma enhanced chemical vapor deposition (PECVD). The SEM images and X-ray diffraction spectra illustrate the strong interaction between the InN particles and the TiO(2) films. UV-Vis absorption spectra indicate that the InN particles have an increased absorption in the visible light region and may sensitize the TiO(2) films. The strong PL band observed in the anatase TiO(2) thin films with the addition of InN may have been due to an increased localization of impurities and/or defect-trapped excitons.
Charge Transfer Luminescence of Several Zirconium-Containing Compounds Using Synchrotron Radiation
(2011)
Wang, De-Yin
;
Chen, Teng-Ming
;
Cheng, Bing-Ming
;
應用化學系
;
Department of Applied Chemistry
Photoluminescence properties of pristine and Eu(2+)-doped zirconates, viz. BaZr(PO(4))(2), BaZr(4)(PO(4))(6), Ba(2)Zr(2)Si(3)O(12), and Ca(3)ZrSi(2)O(9), excited by vacuum ultraviolet (VUV) light using synchrotron radiation were studied. The undoped zirconates show self-activated emission in the 300-340 nm region under VUV excitation, which is ascribed to the Zr(4+)-O(2-) charge transfer luminescence. Upon doping Eu(2+) into these compounds, no Eu(2+) emission was observed in the rest of compounds, except for a weak Eu(2+) emission observed in Ba(2)Zr(2)Si(3)O(12):Eu(2+). The quenching of Eu(2+) luminescence is rationalized as the presence of Zr(4+)-Eu(2+) metal-metal charge transfer. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3605475] All rights reserved.

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