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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.
Switchable structural modification accompanying altered optical properties of a zwitterionic polysquaraine
(2010-11-01)
Lu, Hsiao-Chi
;
Whang, Wha-Tzong
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Cheng, Bing-Ming
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材料科學與工程學系
;
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
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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.
Charge transfer luminescence of hafnates under synchrotron vacuum ultraviolet excitation
(2014)
Wang, De-Yin
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Huang, Chien-Hao
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Cheng, Bing-Ming
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Chen, Teng-Ming
;
Wang, Yu-Hua
Under synchrotron vacuum ultraviolet excitation, three different hafnates (BaHf(PO4)(2), BaHf(BO3)(2) and BaHfSi3O9) show self-activated luminescence with peaks ranging from 275-335 nm, which is attributed to the charge-transfer luminescence from the hafnate (HfO68-) group. Upon doping Eu2+ into BaHfSi3O9, host sensitization of Eu2+ emission via hafnate intrinsic emission is demonstrated.
Luminescence Investigation on Ultraviolet-Emitting Rare-Earth-Doped Phosphors Using Synchrotron Radiation
(2011-07-18)
Huang, Chien-Hao
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Chen, Teng-Ming
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Cheng, Bing-Ming
;
應用化學系
;
Department of Applied Chemistry
Three series of new ultraviolet-emitting Ca(9)Y(PO(4))(7):Ln(3+) (Ln = Ce, Gd, Pr) phosphors were synthesized, and their luminescence was investigated. Under vacuum ultraviolet excitation Ca(9)Y(PO(4))(7):Ce(3+) phosphors emit UVA light with one broad emission centered at 346 nm, on account of the 5d(1)-> 4f(1) transition of Ce(3+) ions; the optimal doping concentration of these phosphors is 0.2 mol. Ca(9)Y(PO(4))(7):G(3+) phosphors show a strong 4f(7)-> 4f(7) transition and a sharp UVB, emission band at 312 nm; the optimal doping concentration of these phosphors is 0.7 mol. The PL spectra of Ca(9)Y(PO(4))(7):Pr(3+) show two broad UVC emission bands centered between 230 and 340 nm, owing to the 4f(1)5d(1)-> 4f(2) transition of Pr(3+) ions; the optimal, doping concentration of these phosphors is 0.2 mol. Under 172 nm excitation, we found that the luminescence intensity of the UVA-emitting Ca(9)Y(PO(4))(7):0.2Ce(3+) is 0.3675 times that of BaSi(2)O(5):0.05Pb(2+), that of the UVB-emitting Ca(9)Y(PO(4))(7):0.7Gd(3+) is 1.7 times that of YAl(3)(BO(3))(4):0.25Gd(3+), and that of the UVC-emitting Ca(9)Y(PO(4))(7):0.2Pr(3+) is 1.5 times that of LaPO(4):0.1Pr(3+). The thermal stability investigation indicated that the luminescence decay was only 9.2%, 18.2%, and 10.3% for Ca(9)Y(PO(4))(7):0.2Ce(3+); Ca(9)Y(PO(4))(7):0.7Gd(3+), and Ca(9)Y(PO(4))(7):0.2Pr(3+) at 250 degrees C relative to that at ambient temperature, respectively. The Ca(9)Y(PO(4))(7):Ln(3+) (Ln = Ce, Gd, Pr) phosphors exhibit high emission efficiency and excellent thermal stability.
Photoluminescence investigations on a novel green-emitting phosphor Ba3Sc(BO3)(3):Tb3+ using synchrotron vacuum ultraviolet radiation
(2012)
Wang, De-Yin
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Chen, Yi-Chin
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Huang, Chien-Hao
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Cheng, Bing-Ming
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Chen, Teng-Ming
Vacuum ultraviolet (VUV) spectroscopic properties of undoped and Tb3+-doped Ba3Sc(BO3)(3) were investigated by using synchrotron radiation. The Tb3+-doped Ba3Sc(BO3)(3) sample crystallized in a flower-like shape even was synthesized at 1100 degrees C. Upon VUV excitation, Ba3Sc(BO3)(3) exhibited an intrinsic broad UV emission centered at 336 nm, which results from radiative annihilation of self-trapped exciton (STE) that may presumably be associated with band-gap excitations or molecular transitions within the BO33- group. The maximum host absorption for Ba3Sc(BO3)(3) was found at about 180 nm. Upon doping of Tb3+ ions into Ba3Sc(BO3)(3), an efficient energy transfer from the host excitations to Tb3+ via STE emission was observed, showing host sensitization of Tb3+ occurs. The energy transfer from host to Tb3+ via STE emission in Ba3Sc(BO3)(3):Tb3+ was studied as a function of temperature and Tb3+ doping concentration. It has been demonstrated that the energy transfer efficiency was increased with either increasing temperature or Tb3+ doping concentration. In the case of temperature dependent energy transfer, the energy transfer from the STE to Tb3+ is thermally activated, probably due to exciton mobility, while in the case of concentration dependent energy transfer, the energy transfer from the STE to Tb3+ is promoted due to a closer distance between the STE and Tb3+ at high Tb3+ concentration.
Host Sensitization of Tb3+ Ions in Tribarium Lanthanide Borates Ba(3)Ln (BO3)(3) (Ln = Lu and Gd)
(2012-03-05)
Wang, De-Yin
;
Chen, Teng-Ming
;
Cheng, Bing-Ming
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應用化學系
;
Department of Applied Chemistry
The vacuum-ultraviolet (VUV) spectroscopic properties of undoped and Tb3+-doped borates Ba(3)Ln(BO3)(3) (Ln = Lu and Gd) with different crystal structures were investigated by using synchrotron radiation. Ba3Lu(BO3)(3) (BLB) crystallizes in a hexagonal structure, whereas Ba3Gd(BO3)(3) (BGB) crystallizes in a trigonal structure. The maximum host absorption for BLB and BGB was found to locate at similar to 179 and similar to 195 nm, respectively. Upon host excitation, BLB exhibits an intrinsic broad UV emission centered at 339 nm, which is attributed to the recombination of self-trapped excitons that may presumably be associated with band-gap excitations or molecular transitions within the BO33- group. In contrast to BLB, no broad emission but line emission ascribed to a Gd3+ P-6(J)-S-8(7/2) 712 transition was observed in the emission spectrum of BGB. Upon doping of Tb3+ ions into the hosts of BLB and BGB, an efficient energy transfer from the host excitations to Tb3+ via host/Gd3+ emission was observed, showing that host sensitization of Tb3+ occurs in these rare-earth borates.
Absorption cross sections of NH3, NH2D, NHD2, and ND3 in the spectral range 140-220 nm and implications for planetary isotopic fractionation
(2006-08-20)
Cheng, Bing-Ming
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Lu, Hsiao-Chi
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Chen, Hong-Kai
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Bahou, Mohammed
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Lee, Yuan-Pern
Cross sections for photoabsorption of NH3, NH2D, NHD2, and ND3 in the spectral region 140-220 nm were determined at similar to 298 K using synchrotron radiation. Absorption spectra of NH2D and NHD2 were deduced from spectra of mixtures of NH3 and ND3, of which the equilibrium concentrations for all four isotopologues obey statistical distributions. Cross sections of NH2D, NHD2, and ND3 are new. Oscillator strengths, an integration of absorption cross sections over the spectral lines, for both A X and B X systems of NH3 agree satisfactorily with previous reports; values for NH2D, NHD2, and ND3 agree with quantum chemical predictions. The photolysis of NH3 provides a major source of reactive hydrogen in the lower stratosphere and upper troposphere of giant planets such as Jupiter. Incorporating the measured photoabsorption cross sections of NH3 and NH2D into the Caltech/JPL photochemical diffusive model for the atmosphere of Jupiter, we find that the photolysis efficiency of NH2D is lower than that of NH3 by as much as 30%. The D/H ratio in NH2D/NH3 for tracing the microphysics in the troposphere of Jupiter is also discussed.

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