Browsing by Author "Jiang, Jyh-Chiang"

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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
;
Chang, Shu-Chieh
;
Hung, Tzu-Chieh
;
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.
Association structures of ionic liquid/DMSO mixtures studied by high-pressure infrared spectroscopy
(2011-01-28)
Jiang, Jyh-Chiang
;
Lin, Kuan-Hung
;
Li, Sz-Chi
;
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]
Effects of water and methanol on the molecular organization of 1-butyl-3-methylimidazolium tetrafluoroborate as functions of pressure and concentration
(2008-07-28)
Chang, Hai-Chou
;
Jiang, Jyh-Chiang
;
Liou, You-Chang
;
Hung, Chao-Hsin
;
Lai, Ting-Yun
The structural organization in mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF(4)])/water or methanol was studied by infrared spectroscopy. No drastic change in the concentration dependence of the alkyl C-H band frequency was observed at high concentration of the ionic liquid. This behavior indicates a clustering of the ionic liquid in alkyl regions. Nevertheless, the presence of methanol significantly perturbs the ionic liquid-ionic liquid associations in the imidazolium region. On the basis of the responses to change in pressure and concentration, two different types of O-H species, i.e., free O-H and bonded O-H, were observed in the O-H stretching region. For [bmim][BF(4)]/water mixtures, the compression leads to loss of the free O-H band intensity. It is likely that free O-H is switched to bonded O-H as high pressures are applied. For [bmim][BF(4)]/methanol mixtures, the free O-H is still stable under high pressures. (C) 2008 American Institute of Physics.
Interactions of Silica Nanoparticles and Ionic Liquids Probed by High Pressure Vibrational Spectroscopy
(2011-06-23)
Chang, Hai-Chou
;
Hung, Tzu-Chieh
;
Chang, Shu-Chieh
;
Jiang, Jyh-Chiang
;
Lin, Sheng Hsien
Gel-like ionic liquid/nanosilica mixtures have been prepared with the addition of 10 wt % nanosilica to 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide (EMI(+)TFSA(-)), but no changes in C-H spectral features of EMI(+)TFSA(-) were observed in the presence of nanosilica under ambient pressure. As the gel-like mixture of EMI(+)TFSA(-)/nanosilica was compressed, a new alkyl C-H band at ca. 3017 cm(-1) arose. This new spectral feature at ca. 3017 cm(-1) may be attributed to the structural reorganization of alkyl C-H groups induced by the interactions between ionic clusters and nanosilica. The imidazolium C-H bands display nonmonotonic shifts as the pressure is elevated. They blue shift slightly initially, but red shifts occur upon further increase of the pressure. The compression also leads to an increase in the relative intensity of the imidazolium C-H band at ca. 3105 cm(-1). This observation suggests that some associated species are switched to the isolated form due to the presence of nanosilica under high pressures. In contrast to EMI(+)TFSA(-)/nanosilica, the band frequencies and band shapes of 1-butyl-3-methylimidazolium (BMI(+)TFSA(-))/nanosilica are similar to those of pure BMI(+)TFSA(-). These results indicate that the length of alkyl C-H groups plays a nonnegligible role in isolated-associated equilibrium.
Local Structures of Water in 1-Butyl-3-methylimidazolium Tetrafluoroborate Probed by High-Pressure Infrared Spectroscopy
(2008-10-01)
Chang, Hai-Chou
;
Jiang, Jyh-Chiang
;
Liou, You-Chang
;
Hung, Chao-Hsin
;
Lai, Ting-Yun
We have investigated the aggregation behaviors of water molecules in 1-butyl-3-methylimidazolium tetrafluoroborate/water mixtures using high-pressure methods. Under ambient pressure, the IR spectra indicate that two types of O-H species: free O-H and bonded O-H, existing in ionic liquid/water Mixtures. As samples were compressed, a continuous loss of the free O-H band intensity was observed. This observation may have arisen from changes in the local structures of water molecules, and the geometrical properties of the hydrogen-bond network are likely to be perturbed as the pressure is elevated. A complementary insight of the O-H spectral features is obtained by measuring the concentration-dependent variation in the mid-infrared spectra under high pressure. A sharp O-H stretching band was observed in a diluted mixture corresponding to the high order in an ice VII-Iike structure. Nevertheless, a very broad O-H feature was measured in a concentrated mixture, which may be attributed to the presence of more than one stable cluster.
Pressure-enhanced surface interactions between nano-TiO2 and ionic liquid mixtures probed by high pressure IR spectroscopy
(2015-01-01)
Chang, Hai-Chou
;
Jiang, Jyh-Chiang
;
Kuo, Meng-Hsiu
;
Hsu, Ding-Tsai
;
Lin, Sheng Hsien
The pressure-dependent interactions between the ionic liquid mixture ([MPI][I-1.5]) and nano-TiO2 surfaces have been studied up to 2.5 GPa. The results of infrared spectroscopic profiles of [MPI][I-1.5] and [MPI][I-1.5]- nano-TiO2 indicated that no appreciable changes in the C-H stretching bands with the addition of nano-TiO2 were observed under ambient pressure. As the pressure was elevated to 0.7 GPa, the C-H stretching absorption of [MPI][I-1.5] underwent band-narrowing and red-shifts in frequency. In contrast to the results of [MPI][I-1.5], the spectra of [MPI][I-1.5]- nano- TiO2 do not show dramatic changes under high pressures. A possible explanation for this observation is the formation of certain pressure-enhanced C-H...nano-TiO2 interactions around the imidazolium C-H and alkyl C-H groups. As imidazolium C-H...I- is replaced by the weaker imidazolium C-H...polyiodide, the splitting of the imidazolium C-H stretching bands was observed. The experimental results indicate that both nano-TiO2 and polyiodides are capable of disturbing the self-assembly of ionic liquids. This study suggests the possibility to tune the efficiency of dye-sensitized solar cells via a high pressure method.
Solvation and microscopic properties of ionic liquid/acetonitrile mixtures probed by high-pressure infrared spectroscopy
(2009-12-21)
Umebayashi, Yasuhiro
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Jiang, Jyh-Chiang
;
Lin, Kuan-Hung
;
Shan, Yu-Lun
;
Fujii, Kenta
The microscopic features of binary mixtures formed by an ionic liquid (EMI(+)TFSA(-) or EMI(+)FSA(-)) and a molecular liquid (acetonitrile or methanol) have been investigated by high-pressure infrared spectroscopy. On the basis of its responses to changes in pressure and concentration, the imidazolium C-H appears to exist at least in two different forms, i.e., isolated and associated structures. The weak band at approximately 3102 cm(-1) should be assigned to the isolated structure. CD(3)CN can be added to change the structural organization of ionic liquids. The compression of an EMI(+)TFSA(-)/CD(3)CN mixture leads to the increase in the isolated C-H band intensity. Nevertheless, the loss in intensity of the isolated structures was observed for EMI(+)FSA(-)/CD(3)CN mixtures as the pressure was elevated. In other words, the associated configuration is favored with increasing pressure by debiting the isolated form for EMI(+)FSA(-)/CD(3)CN mixtures. The stronger C-H center dot F interactions in EMI(+)FSA(-) may be one of the reasons for the remarkable differences in the pressure-dependent results of EMI(+)TFSA(-) and EMI(+)FSA(-).
Specific interactions between the quaternary ammonium oligoether-based ionic liquid and water as a function of pressure
(2013)
Chang, Hai-Chou
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Jiang, Jyh-Chiang
;
Chen, Tsai-Yi
;
Wang, Hsing-Sheng
;
Li, Leo Yuxiu
The interactions between Ammoeng 100 and water are probed using high-pressure infrared measurements and DFT-calculations. The results of infrared absorption profiles suggest that the energetically favored approach for water molecules to interact with Ammoeng 100 is via the formation of anion-water interactions, whereas the alkyl C-H groups play much less important roles. After comparison with pure Ammoeng 100, it appears that no appreciable changes in band frequencies of alkyl C-H vibrations occurred as Ammoeng 100 was mixed with D2O. The presence of D2O has a red-shift effect on the peak frequency of the S-O stretching vibration under the pressures below 1 GPa in comparison to the absorption frequencies of pure Ammoeng 100. This observation is likely related to local structures of the S=O groups interacting with D2O molecules. DFT-calculations indicate that the most energetically favored conformation of ion pairs should be the species having only one hydrophilic hydrogen bonding. The results of calculations reveal that water addition may induce the partial replacement of C-H center dot center dot center dot O interactions with strong hydrogen bonding between anions and water molecules.
Structural change of ionic association in ionic liquid/water mixtures: A high-pressure infrared spectroscopic study
(2009-03-28)
Umebayashi, Yasuhiro
;
Jiang, Jyh-Chiang
;
Shan, Yu-Lun
;
Lin, Kuan-Hung
;
Fujii, Kenta
High-pressure infrared measurements were carried out to observe the microscopic structures of two imidazolium-based ionic liquids, i.e., 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [EMI(+)(CF(3)SO(2))(2)N(-), EMI(+)TFSA(-)] and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide [EMI(+)(FSO(2))(2)N(-), EMI(+)FSA(-)]. The results obtained at ambient pressure indicate that the imidazolium C-H may exist in two different forms, i.e., isolated and network structures. As the sample of pure EMI(+)FSA(-) was compressed, the network configuration is favored with increasing pressure by debiting the isolated form. For EMI(+)TFSA(-)/H(2)O mixtures, the imidazolium C-H peaks split into four bands at high pressures. The new spectral features at approximately 3117 and 3190 cm(-1), being concentration sensitive, can be attributed to the interactions between the imidazolium C-H and water molecules. The alkyl C-H absorption exhibits a new band at approximately 3025 cm(-1) under high pressures. This observation suggests the formation of a certain water structure around the alkyl C-H groups. The O-H stretching absorption reveals two types of O-H species, i.e., free O-H and bonded O-H. For EMI(+)TFSA(-)/H(2)O mixtures, the compression leads to a loss of the free O-H band intensities, and pressure somehow stabilizes the bonded O-H configurations. The results also suggest the non-negligible roles of weak hydrogen bonds in the structure of ionic liquids.