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  • AIP Publishing  (146)
  • Asia - CrossAsia  (146)
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  • AIP Publishing  (146)
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  • Asia - CrossAsia  (146)
  • 1
    Online Resource
    Online Resource
    AIP Publishing ; 2017
    In:  Chinese Journal of Chemical Physics Vol. 30, No. 3 ( 2017-06-27), p. 303-311
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 30, No. 3 ( 2017-06-27), p. 303-311
    Abstract: The photoionization and dissociation photoionization of toluene have been studied using quantum chemistry methods. The geometries and frequencies of the reactants, transition states and products have been performed at B3LYP/6-311++G(d,p) level, and single-point energy calculations for all the stationary points were carried out at DFT calculations of the optimized structures with the G3B3 level. The ionization energies of toluene and the appearance energies for major fragment ions, C7H7+, C6H5+, C5H6+, C5H5+, are determined to be 8.90, 11.15 or 11.03, 12.72, 13.69, 16.28 eV, respectively, which are all in good agreement with published experimental data. With the help of available published experimental data and theoretical results, four dissociative photoionization channels have been proposed: C7H7++H, C6H5++CH3, C5H6++C2H2, C5H5++C2H2+H. Transition structures and intermediates for those isomerization processes are determined in this work. Especially, the structures of C5H6+ and C5H5+ produced by dissociative photoionization of toluene have been defined as chain structure in this work with theoretical calculations.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 2381472-X
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  • 2
    Online Resource
    Online Resource
    AIP Publishing ; 2022
    In:  Chinese Journal of Chemical Physics Vol. 35, No. 2 ( 2022-04-01), p. 289-294
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 35, No. 2 ( 2022-04-01), p. 289-294
    Abstract: The excited-state double proton transfer (ES-DPT) properties of 1,5-dihydroxyanthraquinone (1,5-DHAQ) in various solvents were investigated using femtosecond transient absorption spectroscopy and the DFT/TDDFT method. The steady-state fluorescence spectra in toluene, tetrahydrofuran (THF) and acetonitrile (ACN) solvents presented that the solvent polarity has an effect on the position of the ESDPT fluorescence emission peak for the 1,5-DHAQ system. Transient absorption spectra show that the increasing polarity of the solvent accelerates the rate of excited state dynamics. Calculated potential energy curves analysis further verified the experimental results. The ESDPT barrier decreases gradually with the increase of solvent polarity from toluene, THF to ACN solvent. It is convinced that the increase of solvent polarity can promote the occurrence of the ESDPT dynamic processes for the 1,5-DHAQ system. This work clarifies the mechanism of the influence of solvent polarity on the ESDPT process of 1,5-DHAQ, which provides novel ideas for design and synthesis of new hydroxyanthraquinone derivatives.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2381472-X
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  • 3
    Online Resource
    Online Resource
    AIP Publishing ; 2022
    In:  Chinese Journal of Chemical Physics Vol. 35, No. 1 ( 2022-02-01), p. 77-85
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 35, No. 1 ( 2022-02-01), p. 77-85
    Abstract: Adsorption and activation of dinitrogen (N2) is an indispensable process in nitrogen fixation. Metal nitride species continue to attract attention as a promising catalyst for ammonia synthesis. However, the detailed mechanisms at a molecular level between reactive nitride species and N2 remain unclear at elevated temperature, which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system. Herein, the 14N/15N isotopic exchange in the reaction between tantalum nitride cluster anions Ta314N3− and 15N2 leading to the regeneration of 14N2/14N15N was observed at elevated temperature (393−593 K) using mass spectrometry. With the aid of theoretical calculations, the exchange mechanism and the effect of temperature to promote the dissociation of N2 on Ta3N3− were elucidated. A comparison experiment for Ta314N4−/15N2 couple indicated that only desorption of 15N2 from Ta314N415N2− took place at elevated temperature. The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species. This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2381472-X
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  • 4
    Online Resource
    Online Resource
    AIP Publishing ; 2019
    In:  Chinese Journal of Chemical Physics Vol. 32, No. 1 ( 2019-02-01), p. 99-106
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 32, No. 1 ( 2019-02-01), p. 99-106
    Abstract: The laminar flame propagation of 1-heptene/air mixtures covering equivalence ratios from 0.7 to 1.5 is investigated in a constant-volume cylindrical combustion vessel at 373 K and elevated pressures (1, 2, 5, and 10 atm). Laminar flame speed and Markstein length are derived from the recorded schlieren images. A kinetic model of 1-heptene combustion is developed based on our previous kinetic model of 1-hexene. The model is validated against the laminar flame speed data measured in this work and the ignition delay time data in literature. Modeling analyses, such as sensitivity analysis and rate of production analysis, are performed to help understand the high temperature chemistry of 1-heptene under various pressures and its influence on the laminar flame propagation. Furthermore, the laminar flame propagation of 1-heptene/air mixtures is compared with that of n-heptane/air mixtures reported in our previous work. The laminar flame speed values of 1-heptene/air mixtures are observed to be faster than those of n-heptane/air mixtures under most conditions due to the enhanced exothermicity and reactivity.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 2381472-X
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  • 5
    Online Resource
    Online Resource
    AIP Publishing ; 2008
    In:  Chinese Journal of Chemical Physics Vol. 21, No. 2 ( 2008-04-01), p. 156-162
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 21, No. 2 ( 2008-04-01), p. 156-162
    Abstract: The mixed monolayer behavior of bilirubin/cholesterol was studied through surface pressure-area (-A) isotherms on aqueous solutions containing various concentrations of calcium ions. Based on the data of -A isotherms, the mean area per molecule, collapse pressure, surface compressibility modulus, excess molecular areas, free energy of mixing, and excess free energy of mixing of the monolayers on different subphases were calculated. The results show an expansion in the structure of the mixed monolayer with Ca2+ in subphase, and non-ideal mixing of the components at the air/water interface is observed with positive deviation from the additivity rule in the excess molecular areas. The miscibility between the components is weakened with the increase of concentration of Ca2+ in subphase. The facts indicate the presence of coordination between Ca2+ and the two components. The mixed monolayer, in which the molar ratio of bilirubin to cholesterol is 3:2, is more stable from a thermodynamic point of view on pure water. But the stable 3:2 stoichiometry complex is destroyed with the increase of the concentration of Ca2+ in subphase. Otherwise, the mixed monolayers have more thermodynamic stability at lower surface pressure on Ca2+ subphase.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2008
    detail.hit.zdb_id: 2381472-X
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  • 6
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 26, No. 6 ( 2013-12-01), p. 739-746
    Abstract: β-Crystallins are the major structural proteins existing in the vertebrate lens, and their conformational stability is critical in maintaining the life-long transparency and refraction index of the lens. Seven subunits of β-crystallins naturally assemble into various heterogeneous oligomers with different sizes. Here, we systematically investigated the thermal stability of the different secondary structures present in β-crystallins and then the dynamic process for the thermal-induced unfolding of β-crystallins by Fourier transform infrared spectroscopy-monitored thermal titration and temperature-jump nanosecond time-resolved IR difference absorbance spectra. Our results show that the N-terminal anti-parallel β-sheets in β-crystallin are the most unstable with a transition midpoint temperature at 36.0±2.1 °C, leading to the formation of an intermediate consisting vastly of random coil structures. This intermediate structure is temporally assigned to that of the monomer generated by the thermal-induced disassembly of β-crystallin oligomers with a transition midpoint temperature of 40.4±0.7 °C. The global unfolding of β-crystallins that leads to denaturation and aggregation indicated by the formation of intermolecular anti-parallel β-sheets has a transition midpoint temperature determined as 72.4±0.2 °C. Temperature-jump time-resolved IR absorbance difference spectroscopy analysis further reveals that thermal-induced unfolding of β-crystallins occurs firstly in the anti-parallel β-sheets in the N-terminal domains with a time constant of 50 ns.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
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  • 7
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 30, No. 4 ( 2017-08-27), p. 389-394
    Abstract: The mixture of graphene oxide (GO) and dye molecules may provide some new applications due to unique electronic, optical, and structural properties. Methylene blue (MB), a typical anionic dye, can attach on GO via π-π stacking and electrostatic interaction, and the molecule removal process on GO has been observed. However, it remains unclear about the ultrafast carrier dynamics and the internal energy transfer pathways of the system which is composed of GO and MB. We have employed ultrafast optical pump-probe spectroscopy to investigate the excited dynamics of the GO-MB system dispersed in water by exciting the samples at 400 nm pump pulse. The pristine MB and GO dynamics are also analyzed in tandem for a direct comparison. Utilizing the global analysis to fit the measured signal via a sequential model, five lifetimes are acquired: (0.61±0.01) ps, (3.52±0.04) ps, (14.1±0.3) ps, (84±2) ps, and (3.66±0.08) ns. The ultrafast dynamics corresponding to these lifetimes was analyzed and the new relaxation processes were found in the GO-MB system, compared with the pristine MB. The results reveal that the functionalization of GO can alter the known decay pathways of MB via the energy transfer from GO to MB in system, the increased intermediate state, and the promoted energy transfer from triplet state MB to ground state oxygen molecules dissolved in aqueous sample.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 2381472-X
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  • 8
    Online Resource
    Online Resource
    AIP Publishing ; 2018
    In:  Chinese Journal of Chemical Physics Vol. 31, No. 4 ( 2018-08-01), p. 457-462
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 31, No. 4 ( 2018-08-01), p. 457-462
    Abstract: Dissociation of molecular hydrogen (H2) is extensively studied to understand the mechanism of hydrogenation reactions. In this study, H2 dissociation by Au1-doped closed-shell titanium oxide cluster anions AuTi3O7− and AuTi3O8− has been identified by mass spectrometry and quantum chemistry calculations. The clusters were generated by laser ablation and mass-selected to react with H2 in an ion trap reactor. In the reaction of AuTi3O8− with H2, the ion pair Au+−O22− rather than Au+−O2− is the active site to promote H2 dissociation. This finding is in contrast with the previous result that the lattice oxygen is usually the reactive oxygen species in H2 dissociation. The higher reactivity of the peroxide species is further supported by frontier molecular orbital analysis. This study provides new insights into gold catalysis involving H2 activation and dissociation.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 2381472-X
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  • 9
    Online Resource
    Online Resource
    AIP Publishing ; 2018
    In:  Chinese Journal of Chemical Physics Vol. 31, No. 4 ( 2018-08-01), p. 537-546
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 31, No. 4 ( 2018-08-01), p. 537-546
    Abstract: We report the investigation on the low-temperature oxidation of cyclohexane in a jet-stirred reactor over 500−742 K. Synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) was used for identifying and quantifying the oxidation species. Major products, cyclic olefins, and oxygenated products including reactive hydroperoxides and high oxygen compounds were detected. Compared with n-alkanes, a narrow low-temperature window (∼80 K) was observed in the low-temperature oxidation of cyclohexane. Besides, a kinetic model for cyclohexane oxidation was developed based on the CNRS model [Combust. Flame 160, 2319 (2013)] , which can better capture the experimental results than previous models. Based on the modeling analysis, the 1,5-H shift dominates the crucial isomerization steps of the first and second O2 addition products in the low-temperature chain branching process of cyclohexane. The negative temperature coefficient behavior of cyclohexane oxidation results from the reduced chain branching due to the competition from chain inhibition and propagation reactions, i.e. the reaction between cyclohexyl radical and O2 and the decomposition of cyclohexylperoxy radical, both producing cyclohexene and HO2 radical, as well as the decomposition of cyclohexylhydroperoxy radical producing hex-5-en-1-al and OH radical.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2018
    detail.hit.zdb_id: 2381472-X
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  • 10
    Online Resource
    Online Resource
    AIP Publishing ; 2013
    In:  Chinese Journal of Chemical Physics Vol. 26, No. 1 ( 2013-02-01), p. 77-82
    In: Chinese Journal of Chemical Physics, AIP Publishing, Vol. 26, No. 1 ( 2013-02-01), p. 77-82
    Abstract: Dimethyl ether carbonylation to methyl acetate was comparatively investigated over mordenite supported copper (Cu/HMOR) catalysts prepared by different methods including evaporation, urea hydrolysis, incipient wetness impregnation and ion-exchange. The results showed that Cu/HMOR prepared via iron-exchange method exhibited the highest catalytic activity due to the synergistic effect of active-site metal and acidic molecular sieve support. Conversion of 95.3% and methyl acetate selectivity of 94.9% were achieved under conditions of 210 °C, 1.5 MPa, and GSHV of 4883 h−1. The catalysts were characterized by nitrogen absorption, X-ray diffraction, NH3 temperature program desorption, and CO temperature program desorption techniques. It was found that Cu/HMOR prepared by ion-exchange method possessed high surface area, moderate strong acid centers, and CO adsorption centers, which improved catalytic performance for the reaction of CO insertion to dimethyl ether.
    Type of Medium: Online Resource
    ISSN: 1674-0068 , 2327-2244
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 2381472-X
    SSG: 6,25
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