Browsing by Author "Lin, Sheng Hsien"

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A High-Pressure Infrared Spectroscopic Study on the Interaction of Ionic Liquids with PEO-PPO-PEO Block Copolymers and 1,4-Dioxane
(2011-02-10)
Jiang, Jyh-Chiang
;
Li, Sz-Chi
;
Shih, Pao-Ming
;
Hung, Tzu-Chieh
;
Chang, Shu-Chieh
We have investigated the effect of pressure on imidazolium C-H-O interactions in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMI(+)TFSA(-))/L64 and EMI(+)TFSA(-)/1,4-dioxane mixtures. The addition of Pluronic L64 to EMI(+)TESA(-) leads to appreciable changes in band frequencies and shapes of the imidazolium C-H stretching bands. A possible explanation is the formation of C-H-O interactions between imidazolium C-H groups and oxygen atoms of polyethylene oxides (PEOs). In other words, L64 can be added to change the relative contribution of the isolated and associated components of EMI(+)TESA(-). In contrast to L64, the oxygen atoms of 1,4-dioxane cannot perturb the local structures of imidazolium C-H groups of EMI(+)TFSA(-) and the association configuration is still favored in the presence of 1,4-dioxane. As the pressure is elevated, 1,4-dioxane molecules tend to associate with themselves and TFSA-interacts with EMI(+) to form associated configurations. Our results suggest the formation of association between EMI(+) cation and L64 and the complexes are stable up to the pressure of 2.5 GPa.
A High-Pressure Study of the Effects of TiO(2) Nanoparticles on the Structural Organization of Ionic Liquids
(2011-12-08)
Chang, Hai-Chou
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Chang, Shu-Chieh
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Hung, Tzu-Chieh
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Jiang, Jyh-Chiang
;
Kuo, Jer-Lai
The local structures between nano-TiO(2) and 1-ethyl-3-methylimidazolium trifluorornethanesulfonate (EMI(+)TFS(-) ) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMI(+)TES(-)) were investigated using high-pressure infrared spectroscopy. No significant changes in C-H spectral features of EMI(+)TFS(-) were observed in the presence of nano-TiO(2) under ambient pressure. As the EMI(+)TES(-)/nano-TiO(2) mixture was compressed to 0.3 GPa, the imidazolium C-H absorptions became two sharp bands at 3108 and 3168 cm(-1), respectively, and the alkyl C-H stretching absorption exhibits a new band at 3010 cm(-1) associated with a weaker band at 3028 cm(-1). It appears that pressure stabilizes the isolated conformations due to pressure-enhanced imidazolium C-H-nano-TiO(2) interactions. Our results also reveal that alkyl C-H groups play non-negligible roles at the conditions of high pressures. The results of BMI(+)TFS(-)/nano-TiO(2) are remarkably different from what is revealed for EMI(+)TFS(-)/nano-TiO(2). The spectral features and band frequencies of BMI(+)TFS(-)/nano-TiO(2) are almost identical to those of pure BMI(+)TES(-) under various pressures. This study demonstrates that changes to the alkyl chain length of the cation could be made to control the order and strength of ionic liquid/nano-TiO(2) interactions.
A High-Pressure Study of the Effects of TiO2 Nanoparticles on the Structural Organization of Ionic Liquids
(2011-12-08)
Chang, Hai-Chou
;
Chang, Shu-Chieh
;
Hung, Tzu-Chieh
;
Jiang, Jyh-Chiang
;
Kuo, Jer-Lai
The local structures between nano-TiO2 and 1-ethyl-3-methylimidazolium trifluorornethanesulfonate (EMI+TFS- ) and 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMI+TES-) were investigated using high-pressure infrared spectroscopy. No significant changes in C-H spectral features of EMI+TFS- were observed in the presence of nano-TiO2 under ambient pressure. As the EMI+TES-/nano-TiO2 mixture was compressed to 0.3 GPa, the imidazolium C-H absorptions became two sharp bands at 3108 and 3168 cm(-1), respectively, and the alkyl C-H stretching absorption exhibits a new band at 3010 cm(-1) associated with a weaker band at 3028 cm(-1). It appears that pressure stabilizes the isolated conformations due to pressure-enhanced imidazolium C-H-nano-TiO2 interactions. Our results also reveal that alkyl C-H groups play non-negligible roles at the conditions of high pressures. The results of BMI+TFS-/nano-TiO2 are remarkably different from what is revealed for EMI+TFS-/nano-TiO2. The spectral features and band frequencies of BMI+TFS-/nano-TiO2 are almost identical to those of pure BMI+TES- under various pressures. This study demonstrates that changes to the alkyl chain length of the cation could be made to control the order and strength of ionic liquid/nano-TiO2 interactions.
A TDDFT study on the excited-state double proton transfer reaction of 8-hydroxyquinoline along a hydrogen-bonded bridge
(2017-08-21)
Liu, Yu-Hui
;
Wang, Shi-Ming
;
Zhu, Chaoyuan
;
Lin, Sheng Hsien
;
應用化學系
The mechanism of the excited-state double proton transfer (ESDPT) reactions of 8-hydroxyquinoline (8HQ) along three types of hydrogen-bonded bridges-ammonia (NH3), water (H2O) and acetic acid (AcOH) has been investigated by using time-dependent density functional theory. Based on the analysis of hydrogen bond strengths and the excited-state potential energy surfaces (PES) along the proton transfer coordinates, it is concluded that the hydrogen bonds play the key role in the excited-state multiple proton transfer reaction. Moreover, three different concerted mechanisms have been found in 8HQ center dot NH3, 8HQ center dot H2O and 8HQ center dot AcOH complexes. Upon photoexcitation, the deprotonation of a hydroxyl group in 8HQ would occur first in 8HQ center dot NH3 due to the stronger hydrogen bond -OH center dot center dot center dot NH3. On the contrary, the hydrogen bond -OH center dot center dot center dot O-C-OH is much weaker in the 8HQ center dot AcOH complex, and this leads to a fast protonation of -N- in the 8HQ moiety. For the 8HQ center dot H2O complex, the hydrogen bond strengths are almost the same, so that both protons would transfer simultaneously in a symmetrical and concerted fashion.
A theoretical search for stable bent and linear structures of low-lying electronic states of the titanium dioxide (TiO(2)) molecule
(2011-01-01)
Lin, Chih-Kai
;
Li, Jun
;
Tu, Zheyan
;
Li, Xiangyuan
;
Hayashi, Michitoshi
In this work geometric optimization and potential energy surface (PES) scan for the TiO(2) molecule were carried out to find out possible stable structures by using quantum chemical calculations. The ground state (S(0) 1 (1)A(1)) has the only equilibrium with a symmetric bent structure, whereas the linear conformer is unstable. The first singlet excited state (S(1) 1 (1)B(2)), on the other hand, possesses two potential minima where one is bent around the Franck-Condon region and the other is linear. The second singlet excited state (S(2) 1 (1)A(2)) has only one minimum which is linear, and at which geometry the first two excited states degenerate. Other low-lying singlet and triplet excited states have been investigated accordingly. Among the functionals applied in the present DFT calculations, B3LYP gave results most close to available experimental data, while some recently developed ones including HSE06, omega B97X-D and CAM-B3LYP were not satisfactory for this small system. Ab initio methods such as CASSCF, CASPT2 as well as CCSD-related calculations have been applied, and the latter two showed good results similar to DFT/B3LYP.
A theoretical search for stable bent and linear structures of low-lying electronic states of the titanium dioxide (TiO2) molecule
(2011-01-01)
Lin, Chih-Kai
;
Li, Jun
;
Tu, Zheyan
;
Li, Xiangyuan
;
Hayashi, Michitoshi
In this work geometric optimization and potential energy surface (PES) scan for the TiO2 molecule were carried out to find out possible stable structures by using quantum chemical calculations. The ground state (S-0 1 (1)A(1)) has the only equilibrium with a symmetric bent structure, whereas the linear conformer is unstable. The first singlet excited state (S-1 1 B-1(2)), on the other hand, possesses two potential minima where one is bent around the Franck-Condon region and the other is linear. The second singlet excited state (S-2 1 (1)A(2)) has only one minimum which is linear, and at which geometry the first two excited states degenerate. Other low-lying singlet and triplet excited states have been investigated accordingly. Among the functionals applied in the present DFT calculations, B3LYP gave results most close to available experimental data, while some recently developed ones including HSE06, omega B97X-D and CAM-B3LYP were not satisfactory for this small system. Ab initio methods such as CASSCF, CASPT2 as well as CCSD-related calculations have been applied, and the latter two showed good results similar to DFT/B3LYP.
A theoretical study on the spectroscopy and the radiative and non-radiative relaxation rate constants of the S(0) (1)A(1)-S(1) (1)A(2) vibronic transitions of formaldehyde
(2010-01-01)
Lin, Chih-Kai
;
Li, Ming-Chung
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Yamaki, Masahiro
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Hayashi, Michitoshi
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Lin, Sheng Hsien
We have carried out a close examination on the mathematical treatments and the first-principle computations concerning the vibronic transitions between the S(0) (1)A(1) and the S(1) (1)A(2) states of formaldehyde. The simulation of absorption spectrum was presented with peak intensities calculated according to vibronic-coupled transition dipole moments and Franck-Condon factors. The radiative and non-radiative transition rate constants from the excited to the ground states were calculated with formulas based on Fermi's golden rule. It is concluded that our simulated absorption spectrum between 300 and 360 nm, as well as the estimated relaxation rate constants, showed good agreements with experimental reports.
A theoretical study on the spectroscopy and the radiative and non-radiative relaxation rate constants of the S-0 (1)A(1)-S-1 (1)A(2) vibronic transitions of formaldehyde
(2010-01-01)
Lin, Chih-Kai
;
Li, Ming-Chung
;
Yamaki, Masahiro
;
Hayashi, Michitoshi
;
Lin, Sheng Hsien
We have carried out a close examination on the mathematical treatments and the first-principle computations concerning the vibronic transitions between the S-0 (1)A(1) and the S-1 (1)A(2) states of formaldehyde. The simulation of absorption spectrum was presented with peak intensities calculated according to vibronic-coupled transition dipole moments and Franck-Condon factors. The radiative and non-radiative transition rate constants from the excited to the ground states were calculated with formulas based on Fermi's golden rule. It is concluded that our simulated absorption spectrum between 300 and 360 nm, as well as the estimated relaxation rate constants, showed good agreements with experimental reports.
Ab initio studies of excited electronic state S(2) of pyrazine and Franck-Condon simulation of its absorption spectrum
(2009-07-07)
He, Rongxing
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Zhu, Chaoyuan
;
Chin, Chih-Hao
;
Lin, Sheng Hsien
;
應用化學系分子科學碩博班
The equilibrium geometry and 24 vibrational-normal-mode frequencies of the excited state S(2)((1)B(2u))of pyrazine are calculated and characterized using the complete active space self-consistent field method in the adiabatic representation. The displaced harmonic oscillator approximation is used to simulate the absorption spectrum of the S(2)((1)B(2u)) state along with the Franck-Condon approximation. It is found that the totally symmetric mode v(1) plays the most important role and this exactly agrees with the experimental observations. The simulated absorption spectrum agrees well with those experimentally observed. This indicates that the present S(2)((1)B(2u)) state calculated in the adiabatic representation effectively includes contribution from the diabatic vibronic coupling through the conical intersection. (C) 2009 Elsevier B.V. All rights reserved.
Ab initio studies of excited electronic state S-2 of pyrazine and Franck-Condon simulation of its absorption spectrum
(2009-07-07)
He, Rongxing
;
Zhu, Chaoyuan
;
Chin, Chih-Hao
;
Lin, Sheng Hsien
;
應用化學系分子科學碩博班
The equilibrium geometry and 24 vibrational-normal-mode frequencies of the excited state S-2(B-1(2u))of pyrazine are calculated and characterized using the complete active space self-consistent field method in the adiabatic representation. The displaced harmonic oscillator approximation is used to simulate the absorption spectrum of the S-2(B-1(2u)) state along with the Franck-Condon approximation. It is found that the totally symmetric mode v(1) plays the most important role and this exactly agrees with the experimental observations. The simulated absorption spectrum agrees well with those experimentally observed. This indicates that the present S-2(B-1(2u)) state calculated in the adiabatic representation effectively includes contribution from the diabatic vibronic coupling through the conical intersection. (C) 2009 Elsevier B.V. All rights reserved.
Absorption and fluorescence spectra of the neutral and anionic green fluorescent protein chromophore: Franck-Condon simulation
(2012-07-10)
Huang, Tsung-wei
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Yang, Ling
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Zhu, Chaoyuan
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Lin, Sheng Hsien
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應用化學系分子科學碩博班
Absorption and fluorescence spectra of the neutral and anionic green fluorescent protein (GFP) chromophore, namely p-hydroxybenzylideneimidazolidinone (p-HBDI), have been simulated using the Franck-Condon factors including inhomogeneous broadening of solvent effect. Ground and the first excited states were calculated by time dependent density functional theory with and without the polarizable continuum model environment. Simulated peak of the neutral/anionic p-HBDI at 380 nm (423 nm)/421 nm agrees with experiment value 370 nm (434 nm)/419 nm for absorption (fluorescence) spectrum. Simulated width of the neutral/anionic p-HBDI at 0.51 eV (0.54 eV)/0.57 eV agrees with experiment value 0.54 eV (0.66 eV)/0.56 eV for absorption (fluorescence) spectrum. (C) 2012 Elsevier B. V. All rights reserved.
Adiabatically driven Brownian pumps
(2013-07-08)
Rozenbaum, Viktor M.
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Makhnovskii, Yurii A.
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Shapochkina, Irina V.
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Sheu, Sheh-Yi
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Yang, Dah-Yen
We investigate a Brownian pump which, being powered by a flashing ratchet mechanism, produces net particle transport through a membrane. The extension of the Parrondo's approach developed for reversible Brownian motors [Parrondo, Phys. Rev. E 57, 7297 (1998)] to adiabatically driven pumps is given. We demonstrate that the pumping mechanism becomes especially efficient when the time variation of the potential occurs adiabatically fast or adiabatically slow, in perfect analogy with adiabatically driven Brownian motors which exhibit high efficiency [Rozenbaum et al., Phys. Rev. E 85, 041116 (2012)]. At the same time, the efficiency of the pumping mechanism is shown to be less than that of Brownian motors due to fluctuations of the number of particles in the membrane.
Algorithmic decoherence time for decay-of-mixing non-Born-Oppenheimer dynamics
(2008-07-14)
Cheng, Shu Chun
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Zhu, Chaoyuan
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Liang, Kuo Kan
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Lin, Sheng Hsien
;
Truhlar, Donald G.
The performance of an analytical expression for algorithmic decoherence time is investigated for non-Born-Oppenheimer molecular dynamics. There are two terms in the function that represents the dependence of the decoherence time on the system parameters; one represents decoherence due to the quantum time-energy uncertainty principle and the other represents a back reaction from the decoherent force on the classical trajectory. We particularly examine the question of whether the first term should dominate. Five one-dimensional two-state model systems that represent limits of multidimensional nonadiabatic dynamics are designed for testing mixed quantum-classical methods and for comparing semiclassical calculations with exact quantum calculations. Simulations are carried out with the semiclassical Ehrenfest method (SE), Tully's fewest switch version (TFS) of the trajectory surface hopping method, and the decay-of-mixing method with natural switching, coherent switching (CSDM), and coherent switching with reinitiation (CSDM-D). The CSDM method is demonstrated to be the most accurate method, and it has several desirable features: (i) It behaves like the representation-independent SE method in the strong nonadiabatic coupling regions; (ii) it behaves physically like the TFS method in noninteractive region; and (iii) the trajectories are continuous with continuous momenta. The CSDM method is also demonstrated to balance coherence well with decoherence, and the results are nearly independent of whether one uses the adiabatic or diabatic representation. The present results provide new insight into the formulation of a physically correct decoherence time to be used with the CSDM method for non-Born-Oppenheimer molecular dynamic simulations. (c) 2008 American Institute of Physics.
Analysis of Initial Reactions of MALDI Based on Chemical Properties of Matrixes and Excitation Condition
(1970-01-01)
Lai, Yin-Hung
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Wang, Chia-Chen
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Chen, Chiu Wen
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Liu, Bo-Hong
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Lin, Sheng Hsien
"This investigation concerns the initial chemical reactions that affect the ionization of matrixes in matrix-assisted laser desorption/ionization (MALDI). The study focuses on the relaxations of photon energy that occur on a comparable time scale to that of ionization, in which the available laser energy is shared and the ionization condition is changed. The relaxations include fluorescence, fragmentation, and nonradiative relaxation from the excited state to the ground state. With high absorption cross section and long excited-state lifetime, photoionization of matrix plays an important role if sufficient laser energy is used. Under other conditions, thermal ionization of the molecule in the ground state is predicted to be one of the important reactions. Evidence of change in the branching ratio of initial reactions with the matrix and the excitation wavelength was obtained with alpha-cyano-4-hydroxycinnamic acid, sinapinic acid, 2,5-dihydroxybenzoic acid, and 2,4,6-trihydroxyacetophenone. These matrixes are studied by obtaining their mixed crystal absorption spectra, fluorescence properties, laser-induced infrared emission, and product ions. The exact ionization pathway depends on the chemical properties of matrixes and the excitation conditions. This concept may explain the diversity of experimental results observed in MALDI experiments, which provides an insight into the ensemble of chemical reactions that govern the generation of ions."
Anharmonic Franck-Condon Simulation of the Absorption and Fluorescence Spectra for the Low-Lying S(1) and S(2) Excited States of Pyridine
(2009-12-31)
Wang, Huan
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Zhu, Chaoyuan
;
Yu, Jian-Guo
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Lin, Sheng Hsien
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應用化學系分子科學碩博班
Anharmonic effects of the absorption and fluorescence spectra of pyridine molecule are studied and analyzed for the two-low lying singlet excited states S(1)((1)B(1)) and S(2)((1)B(2)). The complete active space self-consistent field (CASSCF) method is utilized to compute equilibrium geometries and all 27 vibrational normal-mode frequencies for the ground state and the two excited states. The present calculations show that the frequency differences between the ground and two excited states are small for the ten totally symmetric vibrational modes so that the displaced oscillator approximation can be used for spectrum Simulations. The Franck-Condon factors within harmonic approximation basically grasp the main features of molecular spectra, but simulated 0-0 transition energy position and spectrum band shapes are not satisfactorily good for S(1)((1)B(1)) absorption and fluorescence spectra in comparison with experiment observation. As the first-order anharmonic correction added to Franck-Condon factors, both spectrum positions and band shapes can be simultaneously improved for both absorption and fluorescence spectra. It is concluded that the present anharmonic correction produces a significant dynamic shifts for spectrum positions and improves spectrum band shapes as well. The detailed structures of absorption spectrum of S(2)((1)B(2)) state observed from experiment can be also reproduced with anharmonic Franck-Condon simulation, and these were not shown in the harmonic Franck-Condon simulation with either distorted or Duschinsky effects in the literature.
Anharmonic Franck-Condon Simulation of the Absorption and Fluorescence Spectra for the Low-Lying S-1 and S-2 Excited States of Pyridine
(2009-12-31)
Wang, Huan
;
Zhu, Chaoyuan
;
Yu, Jian-Guo
;
Lin, Sheng Hsien
;
應用化學系分子科學碩博班
Anharmonic effects of the absorption and fluorescence spectra of pyridine molecule are studied and analyzed for the two-low lying singlet excited states S-1(B-1(1)) and S-2(B-1(2)). The complete active space self-consistent field (CASSCF) method is utilized to compute equilibrium geometries and all 27 vibrational normal-mode frequencies for the ground state and the two excited states. The present calculations show that the frequency differences between the ground and two excited states are small for the ten totally symmetric vibrational modes so that the displaced oscillator approximation can be used for spectrum Simulations. The Franck-Condon factors within harmonic approximation basically grasp the main features of molecular spectra, but simulated 0-0 transition energy position and spectrum band shapes are not satisfactorily good for S-1(B-1(1)) absorption and fluorescence spectra in comparison with experiment observation. As the first-order anharmonic correction added to Franck-Condon factors, both spectrum positions and band shapes can be simultaneously improved for both absorption and fluorescence spectra. It is concluded that the present anharmonic correction produces a significant dynamic shifts for spectrum positions and improves spectrum band shapes as well. The detailed structures of absorption spectrum of S-2(B-1(2)) state observed from experiment can be also reproduced with anharmonic Franck-Condon simulation, and these were not shown in the harmonic Franck-Condon simulation with either distorted or Duschinsky effects in the literature.
Anharmonic Franck-Condon simulation of the absorption and fluorescence spectra for the low-lying S-1 and S-2 excited states of pyrimidine
(2012-05-25)
Yang, Ling
;
Zhu, Chaoyuan
;
Yu, Jianguo
;
Lin, Sheng Hsien
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應用化學系分子科學碩博班
Intensities and profiles of vibronic spectra of the low-lying singlet excited states were investigated with anharmonic and harmonic Franck-Condon simulations for pyrimidine. The first-order anharmonic correction shows dynamic shift of spectra that is exactly same as difference of reorganization energy between ground and excited states. The first-order correction show intensity enhancement of absorption and intensity weakening of fluorescence for S-1 state, and dynamic shift is also significant. On the other hand, the first-order correction is negligible for S-2 state. The main spectral progressions are well described by totally symmetry modes v(6a), v(1) and v(12). One mode from non-total symmetry v(16a) contributes to the weak band at 16a(2) transition for S-1 state. Four ab initio methods were employed in simulation; CASSCF, CASPT2, DFT and TD-DFT, and coupled-cluster singles-doubles (CCSD) and the equation-of-motion (EOM-CCSD) methods. They all work well, but CASSCF method show the best agreement with experiment for the weak-band intensities. (C) 2012 Elsevier B.V. All rights reserved.
Association structures of ionic liquid/DMSO mixtures studied by high-pressure infrared spectroscopy
(2011-01-28)
Jiang, Jyh-Chiang
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Lin, Kuan-Hung
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Li, Sz-Chi
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Shih, Pao-Ming
;
Hung, Kai-Chan
Using high-pressure infrared methods, we have investigated close interactions of charge-enhanced C-H-O type in ionic liquid/dimethyl sulfoxide (DMSO) mixtures. The solvation and association of the 1-butyl-3-methylimidazolium tetrafluoroborate (BMI(+)BF(4)(-)) and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate (BMM(+)BF(4)(-)) in DMSO-d(6) were examined by analysis of C-H spectral features. Based on our concentration-dependent results, the imidazolium C-H groups are more sensitive sites for C-H-O than the alkyl C-H groups and the dominant imidazolium C-H species in dilute ionic liquid/DMSO-d(6) should be assigned to the isolated (or dissociated) structures. As the dilute mixtures were compressed by high pressures, the loss in intensity of the bands attributed to the isolated structures was observed. In other words, high pressure can be used to perturb the association-dissociation equilibrium in the polar region. This result is remarkably different from what is revealed for the imidazolium C-H in the BMM(+)BF(4)(-)/D(2)O mixtures. DFT-calculations are in agreement with our experimental results indicating that C(4)-H-O and C(5)-H-O interactions seem to play non-negligible roles for BMM(+)BF(4)(-)/DMSO mixtures. (C) 2011 American Institute of Physics. [doi:10.1063/1.3526485]
C/B codoping effect on band gap narrowing and optical performance of TiO2 photocatalyst: a spin-polarized DFT study
(2013)
Lin, Yanming
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Jiang, Zhenyi
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Zhu, Chaoyuan
;
Hu, Xiaoyun
;
Zhang, Xiaodong
The electronic and optical properties of several possible C/B-codoped models of anatase and rutile TiO2 have been investigated systematically using spin-polarized density functional theory calculations. Our calculated results show that the synergistic effect of C/B codoping can induce some hybridized energy states appearing in the forbidden gap and the band gap has a narrowing in anatase and rutile TiO2, which can lead to a decrease of the photon excitation energy and an obvious red-shift of the optical absorption edge. These results lead to an excellent photocatalytic activity in C/B-codoped TiO2. Moreover, with the increase of C and B impurities' concentration in anatase and rutile TiO2, we find that the intensity of impurity states has a strengthening in the band gap, the position of impurity states changes, and the visible-light absorption performance improves gradually.
Coherent ring currents in chiral aromatic molecules induced by linearly polarized UV laser pulses
(2013)
Kanno, Manabu
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Kono, Hirohiko
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Mineo, Hirobumi
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Lin, Sheng Hsien
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Fujimura, Yuichi