Browsing by Author "Chung, Chao-Yu"

Now showing 1 - 7 of 7

Detection of transient infrared absorption of SO3 and 1,3,2-dioxathietane-2,2-dioxide [cyc-(CH2)O(SO2)O] in the reaction CH2OO+SO2
(2018-02-14)
Wang, Yi-Ying
;
Dash, Manas Ranjan
;
Chung, Chao-Yu
;
Lee, Yuan-Pern
;
應用化學系
We recorded time-resolved infrared absorption spectra of transient species produced on irradiation at 308 nm of a flowing mixture of CH2I2/O-2/N-2/SO2 at 298 K. Bands of CH2OO were observed initially upon irradiation; their decrease in intensity was accompanied by the appearance of an intense band at 1391.5 cm(-1) that is associated with the degenerate SO-stretching mode of SO3, two major bands of HCHO at 1502 and 1745 cm(-1), and five new bands near > 1340, 1225, 1100, 940, and 880 cm(-1). The band near 1340 cm(-1) was interfered by absorption of SO2 and SO3, so its band maximum might be greater than 1340 cm(-1). SO3 in its internally excited states was produced initially and became thermalized at a later period. The rotational contour of the band of thermalized SO3 agrees satisfactorily with the reported spectrum of SO3. These five new bands are tentatively assigned to an intermediate 1,3,2-dioxathietane-2,2-dioxide [cyc-(CH2)O(SO2)O] according to comparison with anharmonic vibrational wavenumbers and relative IR intensities predicted for this intermediate. Observation of a small amount of cyc-(CH2)O(SO2)O is consistent with the expected reaction according to the potential energy scheme predicted previously. SO3+HCHO are the major products of the title reaction. The other predicted product channel HCOOH+SO2 was unobserved and its branching ratio was estimated to be < 5%. Published by AIP Publishing.
Evidence of preserved collagen in an Early Jurassic sauropodomorph dinosaur revealed by synchrotron FTIR microspectroscopy
(2017-01-31)
Lee, Yao-Chang
;
Chiang, Cheng-Cheng
;
Huang, Pei-Yu
;
Chung, Chao-Yu
;
Huang, Timothy D.
Fossilized organic remains are important sources of information because they provide a unique form of biological and evolutionary information, and have the long-term potential for genomic explorations. Here we report evidence of protein preservation in a terrestrial vertebrate found inside the vascular canals of a rib of a 195-million-year-old sauropodomorph dinosaur, where blood vessels and nerves would normally have been present in the living organism. The in situ synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectra exhibit the characteristic infrared absorption bands for amide A and B, amide I, II and III of collagen. Aggregated haematite particles (alpha-Fe2O3) about 6 similar to 8 mu m in diameter are also identified inside the vascular canals using confocal Raman microscopy, where the organic remains were preserved. We propose that these particles likely had a crucial role in the preservation of the proteins, and may be remnants partially contributed from haemoglobin and other iron-rich proteins from the original blood.
Infrared absorption of methanol-water clusters (CH3OH)(n)(H2O), n=1-4, recorded with the VUV-ionization/IR-depletion technique
(2017-04-14)
Lee, Yu-Fang
;
Kelterer, Anne-Marie
;
Matisz, Gergely
;
Kunsagi-Mate, Sandor
;
Chung, Chao-Yu
We recorded infrared (IR) spectra in the CH- and OH-stretching regions of size-selected clusters of methanol (M) with one water molecule (W), represented as MnW, n = 1-4, in a pulsed supersonic jet using the photoionization/IR-depletion technique. Vacuum ultraviolet emission at 118 nm served as the source of ionization in a time-of-flight mass spectrometer to detect clusters M-n W as protonated forms Mn-1 WH+. The variations in intensities of Mn-1 WH+ were monitored as the wavelength of the IR laser light was tuned across the range 2700-3800 cm(-1). IR spectra of size-selected clusters were obtained on processing of the observed action spectra of the related cluster-ions according to a mechanism that takes into account the production and loss of each cluster due to IR photodissociation. Spectra of methanol-water clusters in the OH region show significant variations as the number of methanol molecules increases, whereas those in the CH region are similar for all clusters. Scaled harmonic vibrational wavenumbers and relative IR intensities predicted with the M06-2X/aug-cc-pVTZ method for the methanol-water clusters are consistent with our experimental results. For dimers, absorption bands of a structure WM with H2O as a hydrogen-bond donor were observed at 3570, 3682, and 3722 cm(-1), whereas weak bands of MW with methanol as a hydrogen-bond donor were observed at 3611 and 3753 cm(-1). For M2W, the free OH band of H2O was observed at 3721 cm(-1), whereas a broad feature was deconvoluted to three bands near 3425, 3472, and 3536 cm(-1), corresponding to the three hydrogen-bonded OH-stretching modes in a cyclic structure. For M3W, the free OH shifted to 3715 cm(-1), and the hydrogen-bonded OH-stretching bands became much broader, with a weak feature near 3179 cm(-1) corresponding to the symmetric OH-stretching mode of a cyclic structure. For M4W, the observed spectrum agrees unsatisfactorily with predictions for the most stable cyclic structure, indicating significant contributions from branched isomers, which is distinctly different from M-5 of which the cyclic form dominates. Published by AIP Publishing.
Infrared spectral identification of the Criegee intermediate (CH3)(2)COO
(2016-10-21)
Wang, Yi-Ying
;
Chung, Chao-Yu
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
Criegee intermediates are carbonyl oxides that play critical roles in the ozonolysis of alkenes in the atmosphere. So far, the infrared spectra of only the simplest Criegee intermediates CH2OO and CH3CHOO are reported. We report the transient infrared spectrum of the next member (CH3)(2)COO, produced from ultraviolet irradiation of a mixture of (CH3)(2)CI2 + O-2 in a flow reactor and detected with a step-scan Fourier-transform spectrometer. The four observed bands near 1424, 1368, 1040, and 887.4 cm(-1) provide definitive identification of (CH3)(2)COO. The observed vibrational wavenumbers and rotational contours agree with those predicted with quantum-chemical calculations; contributions of the hot bands from excited states of the low-lying torsional modes are significant. The rapid decay yields an estimate of the rate coefficient similar to 1.6 x 10(-10) cm(3) molecule(-1) s(-1) for the self-reaction of (CH3)(2)COO. The direct IR detection of (CH3)(2)COO should prove useful for field measurements and laboratory investigations of related Criegee mechanism. Published by AIP Publishing.
Label-Free Optical Microscope Based on a Phase-Modulated Femtosecond Pump-Probe Approach with Subdiffraction Resolution
(2020-03-18)
Fathi, Amir
;
Chung, Chao-Yu
;
Lee, Yuan-Pern
;
Diau, Eric Wei-Guang
;
交大名義發表
A far-field optical microscope (OM) is a powerful noninvasive, nondestructive tool to study sub-micrometer structures and organisms, which has been used for decades to study the interactions between light and matter in the spatial domain. We report here a sophisticated label-free OM method with superspatial resolution to visualize ZnO nanoparticles. Of three femtosecond pulses, two served as pumps at 1000 nm and the other one served as a probe at 774 nm. The two pumps (one of Gaussian shape and the other of toroidal shape) were generated with a phase difference of 180 degrees. When the conventional pump-probe approach was used in the absence of a second toroidal pump, a ZnO nanoparticle was observed to show a particle size of 445 nm because of the limit of diffraction. In contrast, when the second toroidal pump was applied out of phase, the obtained OM image showed a ZnO nanoparticle down to 96 nm. We demonstrated for the first time that the reported phase-modulated pump-probe approach has an ability for spatial resolution beyond its optical diffraction limit and a potential for label-free imaging applications in nanomaterials and life sciences.
Probing the binding kinetics of proinflammatory cytokine-antibody interactions using dual color fluorescence cross correlation spectroscopy
(2011)
Wu, Chia-Yan
;
Huang, Chuan-Keng
;
Chung, Chao-Yu
;
Huang, I-Ping
;
Hwu, Yeukuang
Dual color fluorescence cross correlation spectroscopy (FCCS) was used to investigate quantitatively the binding kinetics of tumor necrosis factor (TNF alpha) with TNF alpha antibody (anti-TNF alpha) following fluorescent labeling. Through the analysis of the auto correlation curves of fluorescence correlation spectroscopy (FCS), diffusion coefficients of 100.06 +/- 4.9 mu m(2) s(-1) and 48.96 +/- 2.52 mu m(2) s(-1) for Alexa488-TNF alpha and Atto647N-anti-TNF alpha were obtained. In addition, the calculated hydrodynamic diameters of the Alexa488-TNF alpha and Atto647N-anti-TNF alpha were approximately 4.89 +/- 0.24 nm and 9.99 +/- 0.52 nm, respectively, which agrees with the values of 5.20 +/- 1.23 nm and 9.28 +/- 0.86 nm for the native TNF alpha and the anti-TNF alpha as determined from dynamic light scattering measurements. For the binding kinetics, association (k(on)) and dissociation (k(off)) rate constants were (1.13 +/- 0.08) x 10(4) M(-1) s(-1) and (1.53 +/- 0.19) x 10(-3) s(-1) while the corresponding dissociation constant (K(d)) at 25 degrees C was (1.36 +/- 0.10) x 10(-7) M. We believe this is the first report on the binding kinetics for TNF alpha-antibody recognition in the homogeneous phase. Using this technology, we have shown that controlled experiments can be performed to gain insight into molecular mechanisms involved in the immune response.
Rovibronic bands of the (A)over-tilde <-(X)over-tilde transition of CH3OO and CD3OO detected with cavity ringdown absorption near 1.2-1.4 mu m
(2007-07-28)
Chung, Chao-Yu
;
Cheng, Chi-Wen
;
Lee, Yuan-Pern
;
Liao, Hsin-Yi
;
Sharp, Erin N.
We have recorded several rovibronic bands of CH3OO and CD3OO in their (A) over tilde <-(K) over tilde transitions in the range of 1.18-1.40 mu m with the cavity ringdown technique. While the electronic origins for these species have been reported previously, many newly observed rovibronic bands are described here. The experimental vibrational frequencies (given as nu in the unit cm(-1) in this paper) for the COO bending (nu(8)) and COO symmetric stretching (nu(7)) modes in the (A) over tilde state are 378 and 887 cm(-1) for CH3OO, and 348 and 824 cm(-1) for CD3OO, respectively. In addition, two other vibrational frequencies were observed for the (A) over tilde state of CD3OO, namely, nu(5) (954 cm(-1)) and nu(6) (971 cm(-1)). These experimental vibrational frequencies for the A state of both CH3OO and CD3OO are in good agreement with predictions from quantum-chemical calculations at the UB3LYP/aug-cc-pVTZ level. The enhanced activity of the nu(5) vibrational mode in CD3OO is rationalized by mode mixing with the nu(7) mode, as supported by calculations of multidimensional Franck-Condon factors. In addition, many hot bands involving the methyl torsional mode (nu(12)) are observed for both normal and deuterated methyl peroxy. These bands include the "typical" sequence transitions and some "atypical" ones due to the nature of the eigenvalues and eigenfunctions which are a consequence of the low, but very different, torsional barriers in the (X) over tilde and (A) over tilde states. In addition, the 12(2)(2) band in CH3OO and the 12(3)(3) band in CD3OO show quite different structures than the origin bands, an effect which results from tunneling splittings comparable to the rotational contour. (C) 2007 American Institute of Physics.