Browsing by Author "Cheng, Bing-Ming"

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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.
Absorption spectra in the vacuum ultraviolet region of methanol in condensed phases
(2007-10-15)
Kuo, Yu-Ping
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Lu, Hsiao-Chi
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Wu, Yu-Jong
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Cheng, Bing-Ming
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Ogilvie, J. F.
With radiation from a synchrotron we measured the spectra of pure solid methanol and of methanol dispersed in solid argon (molar ratio 200) and krypton (molar ratio 250) at 10 K from the onset of absorption in the vacuum ultraviolet region until the limits imposed by LiF windows or the Ar or Kr dispersant. We fitted the total absorption profile divided by wavenumber to gaussian curves of minimal number. and made tentative assignments of electronic transitions and vibrational structure by comparison with spectra of gaseous methanol and with energies and intensities from our published quantum-chemical calculations. (C) 2007 Elsevier B.V. All rights reserved.
Absorption spectra in the vacuum ultraviolet region of small molecules in condensed phases
(2008-12-15)
Lu, Hsiao-Chi
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Chen, Hong-Kai
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Cheng, Bing-Ming
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Ogilvie, J. F.
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材料科學與工程學系
With radiation from a synchrotron we measured the spectra of several small molecular species in the, solid phase at 10K, either pure -O(2), NO, CO(2), N(2)O, H(2)O and NH(3) - or, for NH3 also dispersed in Ar at, molar ratio 1/250, from the onset of absorption in the ultraviolet region until the limits of transmission by crystalline LiF or solid At. In a quantitative treatment of spectral data, we fitted the total absorption profile divided by wavenumber to Gaussian curves of minimal number, and made tentative assignments of electronic transitions and vibrational structure by comparison with spectra of gaseous species. These results illuminate the nature of electronic spectra of samples in solid phases in the vacuum ultraviolet region. (C) 2008 Elsevier B.V. All rights reserved.
BaMgAl10O17 : Eu blue phosphors with MgO coating and microwave irradiation
(2008-02-01)
Kuo, Kuan-Ting
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Lee, Shu-Ping
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Chen, San-Yuan
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Cheng, Bing-Ming
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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.
Blue/near UV light emission from hybrid InN/TiO(2) nanoparticle films
(2011-01-01)
Wu, Chih-Wei
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Lu, Chih-Wei
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Lee, Yuan-Pern
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Wu, Yu-Jong
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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.
Blue/near UV light emission from hybrid InN/TiO2 nanoparticle films
(2011-01-01)
Wu, Chih-Wei
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Lu, Chih-Wei
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Lee, Yuan-Pern
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Wu, Yu-Jong
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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 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
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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.
Charge Transfer Luminescence of Several Zirconium-Containing Compounds Using Synchrotron Radiation
(2011)
Wang, De-Yin
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Chen, Teng-Ming
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Cheng, Bing-Ming
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應用化學系
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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.
Charge-Transfer Luminescence and Energy Transfer in Eu(2+)-Doped Barium Zirconosilicates
(2011-01-01)
Wang, De-Yin
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Wang, Ling-Li
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Lee, Te-Ju
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Chen, Teng-Ming
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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 BaZrSi(3)O(9) and Ba(2)Zr(2)Si(3)O(12) using synchrotron radiation, and examined the possibility of sensitizing Eu(2+) by hosts that contain zirconate. Upon VUV excitation, BaZrSi(3)O(9) and Ba(2)Zr(2)Si(3)O(12) show self-activated emission peaking at 285 nm and 334 nm, which are assigned to Zr(4+)-O(2-) charge transfer (CT) luminescence. The evidence for the occurrence of Zr(4+)-O(2-) charge transfer in BaZrSi(3)O(9) and Ba(2)Zr(2)Si(3)O(12) was further supported by density of state (DOS) calculation. Energy transfer from host excitation (similar to 172 nm) to Eu(2+) was observed in BaZrSi(3)O(9):Eu(2+) and Ba(2)Zr(2)Si(3)O(12):Eu(2+), showing that host sensitization of Eu(2+) occurs in these materials. Despite that the host emission overlaps with the Eu(2+) 4f-5d absorption band significantly, host -to-Eu(2+) energy transfer in Ba(2)Zr(2)Si(3)O(12):Eu(2+) was found to be less efficient than that in BaZrSi(3)O(9):Eu(2+) and Eu(2+) luminescence was found to be inferior in Ba(2)Zr(2)Si(3)O(12):Eu(2+). These observations are ascribed to a smaller Zr-O-Ba(Eu) angles and a lower Eu(2+)-Zr(4+) metal-to-metal charge transfer energy in Ba(2)Zr(2)Si(3)O(12):Eu(2+). (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.008112jes] All rights reserved.
Charge-Transfer Luminescence and Energy Transfer in Eu2+-Doped Barium Zirconosilicates
(2011-01-01)
Wang, De-Yin
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Wang, Ling-Li
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Lee, Te-Ju
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Chen, Teng-Ming
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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.
Effect of alkyl position of pyrrole on structures and properties of conjugated polysquaraines
(2010-05-01)
Lu, Hsiao-Chi
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Whang, Wha-Tzong
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Cheng, Bing-Ming
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材料科學與工程學系
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Department of Materials Science and Engineering
Poly(1-octylpyrrolyl)squaraine and poly(3-octylpyrrolyl)squaraine were synthesized from squaric acid with 1-octylpyrrole and 3-octylpyrrole under identical conditions of condensation. Visible absorption spectra, photoluminescence spectra, TGA curves, and IR spectra were recorded to characterize the structures of these polymers as synthesized: the measured optical and thermal properties are consistent with backbone structures. The polysquaraine from 3-octylpyrrole possesses mostly zwitterionic repeating units (>97%), but the polymer from 1-octylpyrrole consists of zwitterionic and covalent repeating units in a ratio 2:1. Observations from the visible absorption and photoluminescence spectra in varied solvents, TGA curves, and thermal IR measurements for these two polymers reconciled to their structures. This result indicates that the position of the alkyl group in the pyrrole derivative affects the conformation in the condensation of poly(pyrrolyl)squaraine. These polysquaraines are stable below temperature 155 C and their visible absorption and photoluminescence properties in hydrogen-bonding solvents exhibit negative solvatochromism. (C) 2010 Elsevier B.V. All rights reserved.
Effect of microwave irradiation on surface characteristics and luminescent properties of BaMgAl10O17 : Eu blue phosphor
(2008-02-01)
Kuo, Kuan-Ting
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Lee, Shu-Ping
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Chen, San-Yuan
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Cheng, Bing-Ming
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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.
FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C(5)H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
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Chen, Hui-Fen
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Camacho, Cristopher
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Witek, Henryk A.
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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 C(5)H radicals.
FORMATION AND IDENTIFICATION OF INTERSTELLAR MOLECULE LINEAR C5H FROM PHOTOLYSIS OF METHANE DISPERSED IN SOLID NEON
(2009-08-10)
Wu, Yu-Jong
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Chen, Hui-Fen
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Camacho, Cristopher
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Witek, Henryk A.
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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.
Host Sensitization of Tb3+ Ions in Tribarium Lanthanide Borates Ba(3)Ln (BO3)(3) (Ln = Lu and Gd)
(2012-03-05)
Wang, De-Yin
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Chen, Teng-Ming
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Cheng, Bing-Ming
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應用化學系
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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.
Infrared absorption spectra of vinyl radicals isolated in solid Ne
(2008-05-28)
Wu, Yu-Jong
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Lin, Meng-Yeh
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Cheng, Bing-Ming
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Chen, Hui-Fen
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Lee, Yuan-Pern
Irradiation of samples of solid Ne near 3.0 K containing ethene (C(2)H(4)) with vacuum ultraviolet radiation at 120 nm from synchrotron yielded new spectral lines at 3141.0, 2953.6, 2911.5, 1357.4, 677.1, 895.3, and 857.0 cm(-1). These features are assigned to alpha-CH stretching (nu(1)), CH(2) antisymmetric stretching (nu(2)), CH(2) symmetric stretching (nu(3)), CH(2)-bending (nu(5)), HCCH cis bending (nu(7)), CH(2) out-of-plane bending (nu(8)), and alpha-CH out-of-plane bending (nu(9)) modes of C(2)H(3), respectively, based on results of (13)C- and D-isotopic experiments and quantum-chemical calculations. These calculations using density-functional theory (B3LYP and PW91PW91/aug-cc-pVTZ) predict vibrational wavenumbers, IR intensities, and isotopic ratios of vinyl radical that agree satisfactorily with our experimental results. (C) 2008 American Institute of Physics.
Investigation of Pr(3+) as a sensitizer in quantum-cutting fluoride phosphors
(2008-02-25)
Lee, Te-Ju
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Luo, Li-Yang
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Cheng, Bing-Ming
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Diau, Wei-Guang
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Chen, Teng-Ming
A quantum-cutting (QC) phosphor K(2)GdF(5):Eu(3+) shows poor optical absorption and a theoretical quantum efficiency (QE) of 107% in the ultraviolet (UV) and vacuum ultraviolet (VUV) excitation spectral ranges. Pr(3+) was codoped as a sensitizer in K(2)GdF(5): Eu(3+) thus increasing the absorption in the UV and VUV spectral regions; the theoretical QE of K(2)GdF(5): Eu(3+), Pr(3+) was increased to 138%. The spectra indicate that the possible mechanisms of QC and energy transfer differ from those of phosphors containing the Gd(3+) -Eu(3+) couple. Temporally resolved measurements of fluorescence decay confirm the proposed QC mechanism for the phosphor containing the Gd(3+) -Eu(3+),Pr(3+) system. (C) 2008 American Institute of Physics.
Isotopic fractionation of nitrogen in ammonia in the troposphere of Jupiter
(2007-03-10)
Liang, Mao-Chang
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Cheng, Bing-Ming
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Lu, Hsiao-Chi
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Chen, Hong-Kai
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Alam, M. S.
Laboratory measurements of the photoabsorption cross section of (NH3)-N-15 at wavelengths between 140 and 220 nm are presented for the first time. Incorporating the measured photoabsorption cross sections of (NH3)-N-15 and (NH3)-N-14 into a one-dimensional photochemical diffusive model, we find that at 400 mbar, the photolytic efficiency of (NH3)-N-15 is about 38% greater than that of (NH3)-N-14. In addition, it is known that ammonia can condense in the region between 200 and 700 mbar, and the condensation tends to deplete the abundance ratio of (NH3)-N-15 and (NH3)-N-14. By matching the observed ratio of (NH3)-N-15 and (NH3)-N-14 at 400 mbar, the combined effect of photolysis and microphysics produces the ratio of (2.42 +/- 0.34) x 10(-3) in the deep atmosphere, in excellent agreement with the Galileo spacecraft measurements. The usefulness of the isotopic composition of ammonia as a tracer of chemical and dynamical processes in the troposphere of Jupiter is discussed.
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
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應用化學系
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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.
Photoabsorption cross sections of NH3, NH2D, NHD2, and ND3 in the spectral range 110-144 nm
(2007-10-21)
Wu, Yu-Jong
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Lu, Hsiao-Chi
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Chen, Hong-Kai
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Cheng, Bing-Ming
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Lee, Yuan-Pern
Cross sections for photoabsorption of NH3, NH2D, NHD2, and ND3 near 298 K were measured in the spectral range of 110-144 nm using radiation from a synchrotron. Absorption cross sections and oscillator strengths of NH3 agree satisfactorily with previous reports; those of ND3 are improved over those in a previous report, whereas those of NH2D and NHD2 are new. The oscillator strengths of transitions to D, D-', D-'', F, and G states are nearly the same among all four isotopic variants, but those to D-''' and E states vary substantially. Observed absorption bands are arranged into vibrational progressions in accord with known Rydberg transitions. All progressions show a common trend of vibrational intervals increasing with vibrational quantum numbers. The Rydberg orbitals for states D(3de('')), D-'(4sa(1)(')), D-''(3da(1)(')), D-'''(4pe(')), and E(4de('')) are readily assigned with quantum defects determined in these experiments, but assignments for F(5de('')) and G(6de('')) are uncertain. Absorption cross sections of dissociative continua underneath discrete structures are larger for NH2D and NHD2 than for NH3 and ND3, indicating that the rate of dissociation of ammonia might increase when its symmetry is broken. (C) 2007 American Institute of Physics.