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Chinese Journal of Chemical Physics 2008年第4期21卷 314-323页

作者： Jun Feng Dan Wu Jia Wen Shi-lin Liu Hong-fei Wang Hefei National Laboratory for Physical Sciences at Microscale Department of Chemical Physics University of Science and Technology of China Hefei 230025 China Beijing National Laboratory for Molecular Sciences State Key Laboratory of Molecular Reaction Dynamics Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China

The C-H stretch vibrational spectra of the trisiloxane superspreading surfactant Silwet L-77 （（CH3）3Si- O-Si（CH3）（C3H6）（OCH2CH2）7-8OCH3）-O-Si（CH3）3） at the air/water interface are measured with the surface sum frequency generation vibrational spectroscopy （SFG-VS）. The spectra are dominated with the features from the -Si-CH3 groups around 2905 cm^-1 （symmetric stretch or SS mode） and 2957 ^-1 （mostly the asymmetric stretch or AS mode）, and with the weak but apparent contribution from the -O-CH2- groups around 2880 ^-1 （symmetric stretch or SS mode）. Comparison of the polarization dependent SFG spectra below and above the critical aggregate or micelle concentration （CAC） indicates that the molecular orientation of the C-H related molecular groups remained unchanged at different surface densities of the Silwet L-77 surfactant. The SFG-VS adsorption isotherm suggested that there was no sign of Silwet L-77 bilayer structure formation at the air/water interface. The Gibbs adsorption free energy of the Silwet surfactant to the air/water interface is -42.2±0.8kcal/mol, indicating the unusually strong adsorption ability of the Silwet L-77 superspreading surfactant.

关键词： Trisiloxane surfactant Superspreader Surface adsorption sum frequency generation vibrational spectroscopy

Surface of room temperature ionic liquid [bmim][PF_6] studied by polarization- and experimental configuration-dependent sum frequency generation vibrational spectroscopy

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Science China Chemistry 2015年第3期58卷 439-447页

作者： Ganghua Deng Youqi Guo Xia Li Zhen Zhang Shilin Liu Zhou Lu Yuan Guo Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China Nanjing University of Aeronautics and Astronautics Beijing National Laboratory for Molecular Sciences State Key Laboratory of Molecular Reaction Dynamics Institute of Chemistry Chinese Academy of Sciences

Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface.

关键词： ionic liquid sum frequency generation vibrational spectroscopy interface orientation

Absolute Orientation of Molecules with Competing Hydrophilic Head Groups at the Air/Water Interface Probed with sum frequency generation vibrational spectroscopy

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Chinese Journal of Chemical Physics 2009年第2期22卷 197-203页

作者： Feng Wang Zhi Huang Zhi-feng Cui Hong-fei Wang Department of Physics Anhui Normal University Wuhu 241000 China Beijing National Laboratory for Molecular Sciences State Key Laboratory of Molecular Reaction Dynamics Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China

The constructive or destructive spectral interference between the molecular groups oriented up and down at the interface in the sum-frequency generation （SFG） spectra provides a direct measurement of the absolute orientation of these molecular groups. This simple approach can be employed to interrogate absolute molecular orientations other than using the complex absolute phase measurement in the SFG studies. We used the -CN group in the p-cyanophenol （PCP） molecule as the internal phase standard, and we measured the phases of the SFG fields of the -CN groups in the 3,5-dimethyl-4-hydroxy-benzonitrile （35DMHBN） and 2,6-dimethyl-4-hydroxy-benzonitrile （26DMHBN） at the air/water interface by measuring the SFG spectra of the aqueous surfaces of the mixtures of the PCP, 35DMHBN, and 26DMHBN solutions. The results showed that the 35DMHBN had its -CN group pointing into the aqueous phase; while the 26DMHBN, similar to the PCP, had its -CN group pointing away from the aqueous phase. The tilt angles of the -CN group for both the 35DMHBN and 26DMHBN molecules at the air/water interface were around 25°-45° from the interface normal. These results provided insights on the understanding of the detailed balance of the competing factors, such as solvation of the polar head groups, hydrogen bonding and hydrophobic effects, etc., on influencing the absolute molecular orientation at the air/water interface.

关键词： sum frequency generation vibrational spectroscopy Air/water interface Molecule orientation p-cyanophenol

A Highly Sensitive Femtosecond Time-Resolved sum frequency generation vibrational spectroscopy System with Simultaneous Measurement of Multiple Polarization Combinations

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Chinese Journal of Chemical Physics 2017年第6期30卷 671-677,I0002页

作者：谈军军罗毅叶树集中国科学技术大学合肥微尺度物质科学国家研究中心合肥230026

Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interracial molecules function. It requires to develop surface-sensitive, fast-identification, and time-resolved techniques. In this study, we employ several key technical procedures and successfully develop a highly sensitive femtosecond time-resolved sum frequency generation vibrational spectroscopy （SFG-VS） system. This system is able to measure the spectra with two polarization combinations （ssp and ppp, or psp and ssp） simultaneously. It takes less than several seconds to collect one spectrum. To the best of our knowledge, it is the fastest speed of collecting SFG spectra reported by now. Using the time-resolved measurement, ultrafast vibrational dynamics of the N-H mode of α-helical peptide at water interface is determined. It is found that the membrane environment does not affect the N-H vibrational relaxation dynamics. It is expected that the time-resolved SFG system will play a vital role in the deep understanding of the dynamics and interaction of the complex molecules at surface and interface. Our method may also provide an important technical proposal for the people who plan to develop time-resolved SFG systems with simultaneous measurement of multiple polarization combinations.

关键词： Femtosecond time-resolved sum frequency generation vibrational spectroscopy Ultrafast vibrational dynamics Multiple polarization combination measurement Chiral

sum frequency generation vibrational Spectra of Perovskite Nanocrystals at the Single-Nanocrystal and Ensemble Levels

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Chinese Journal of Chemical Physics 2022年第5期35卷 738-746,I0001-I0003,I0011页

作者： Renlong Zhu Quanbing Pei Junjun Tan Xiaoxuan Zheng Shuji Ye Hefei National Research Center for Physical Sciences at the Microscale and Department of Chemical PhysicsUniversity of Science and Technology of ChinaHefei 230026China

Determination of molecular structures of organicinorganic hybrid perovskite(OIHP)nanocrystals at the single-nanocrystal and ensemble levels is essential to understanding the mechanisms responsible for their size-dependent optoelectronic properties and the nanocrystal assembling process,but its detection is still a bit *** this study,we demonstrate that femtosecond sum frequency generation(SFG)vibrational spectroscopy can provide a highly sensitive tool for probing the molecular structures of nanocrystals with a size comparable to the Bohr diameter(∼10 nm)at the single-nanocrystal *** SFG signals are monitored using the spectral features of the phenyl group in(RMBA)PbBr_(3) and(R-MBA)_(2)PbI_(4) nanocrystals(MBA:methyl-benzyl-ammonium).It is found that the SFG spectra exhibit a strong resonant peak at 3067±3 cm^(−1)(ν2 mode)and a weak shoulder peak at 3045±4 cm^(−1)(ν_(7a) mode)at the ensemble level,whereas a peak of theν2 mode and a peak at 3025±3 cm^(−1)(ν20b mode)at the single-nanocrystal *** nanocrystals at the single-nanocrystal level tend to lie down on the surface,but stand up as the ensemble number and the averaged sizes *** finding may provide valuable information on the structural origins for size-dependent photo-physical properties and photoluminescence blinking dynamics in nanocrystals.

关键词： Perovskite Single nanocrystal sum frequency generation vibrational spectroscopy Size-dependent property

sum frequency spectroscopy Studies on Cell Membrane Fusion Induced by Divalent Cations

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Chinese Journal of Chemical Physics 2022年第6期35卷 883-892,I0072页

作者： Xiao-feng Han Wen-hua Sun Shu-jing Wang Xiao-lin Lu State Key Laboratory of Bioelectronics School of Biological Science and Medical EngineeringNational Demonstration Center for ExperimentalBiomedical Engineering EducationSoutheast UniversityNanjing 210096China

Cell membrane fusion is a fundamental biological process involved in a number of cellular living functions. Regarding this, divalent cations can induce fusion of the lipid bilayers through binding and bridging of divalent cations to the charged lipids, thus leading to the cell membrane fusion. However, the elaborate mechanism of cell membrane fusion induced by divalent cations is still needed to be ***, surface/interface sensitive sum frequency generation vibrational spectroscopy(SFG-VS) and dynamic light scattering(DLS) were applied in this research to study the responses of phospholipid monolayer to the exposure of divalent metal ions ***^(2+)and Mg^(2+). According to the particle size distribution results measured by DLS experiments, it was found that Ca^(2+)could induce inter-vesicular fusion while Mg^(2+)could not. An octadecyltrichlorosilane self-assembled monolayer(OTS SAM)-lipid monolayer system was designed to model the cell membrane for the SFG-VS experiment. Ca^(2+)could interact with the lipid POO_(2)^(-)head groups more strongly, resulting in cell membrane fusion more easily, in comparison with Mg^(2+). No specific interaction between the two metal cations and the C=O groups was observed. However, the C=O orientations changed more after Ca^(2+)-PO2-binding than Mg^(2+)mediation on lipid monolayer. Meanwhile, Ca^(2+)could induce dehydration of the lipids(which should be related to the strong Ca^(2+)-PO_(2)^(-)interaction), leading to the reduced hindrance for cell membrane fusion.

关键词： Cell membrane fusion sum frequency generation vibrational spectroscopy Dynamic light scattering Lipid monolayer

Methanol Perturbing Modeling Cell Membranes Investigated using Linear and Nonlinear vibrational spectroscopy

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Chinese Journal of Chemical Physics 2013年第1期26卷 27-34,I0003页

作者：田康振李红春叶树集中国科学技术大学物理系合肥230026 中国科学技术大学化学物理系合肥230026 中国科学技术大学合肥微尺度国家实验室合肥230026

Cell membranes play a crucial role in many biological functions of cells. A small change in the composition of cell membranes can strongly influence the functions of membrane-associated proteins, such as ion and water channels, and thus mediate the chemical and physical balance in cells. Such composition change could originate from the introduction of short-chain alcohols, or other anesthetics into membranes. In this work, we have applied sum frequency generation vibrational spectroscopy （SFG-VS）, supplemented by attenuated total reflectance Fourier transform infrared spectroscopy （ATR-FTIR）, to investigate interaction between methanol and 1,2-dimyristoyl-d54-sn-glycero-3-phosphocholine （d54-DMPC） lipid bilayers. Lipid＇s hydrocarbon interior is deuterated while its head group is hydrogenated. At the same time, CH3 symmetric stretch from methanol and lipid head amine group has different frequency, thus we can distinguish the behaviors of methanol, lipid head amine group, and lipid hydrocarbon interior. Based on the spectral feature of the bending mode of the water molecules replaced by methanol, we determined that the methanol molecules are intercalated into the region between amine and phosphate groups at the lipid hydrophilic head. The dipole of CH3 groups of methanol and lipid head, and the water O-H M1 adopt the same orientation directions. The introduction of methanol into the lipid hydrophilic head group can strongly perturb the entire length of the alkyl chains, resulting that the signals of CD2 and CD3 groups from both leaflets can not cancel each other.

关键词： sum frequency generation vibrational spectroscopy Cell membrane Methanol Interaction Mechanism