Sum Frequency Generation of Interfacial Lipid Monolayers Shows Polarization Dependence on Experimental Geometries
Sum Frequency Generation of Interfacial Lipid Monolayers Shows Polarization Dependence on Experimental Geometries
复制标题
界面脂质单层的和频生成显示了实验几何形状的偏振依赖性
DOI：
10.1021/acs.langmuir.6b01944
复制
发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Lu Xiaolin
中科院分区：
文献类型：
--
作者：
Li Bolin;Li Xu;Ma Yong-Hao;Han Xiaofeng;Wu Fu-Gen;Guo Zhirui;Chen Zhan;Lu Xiaolin
和频振动光谱已被广泛应用于研究生物表面和界面的分子结构，包括模型细胞膜。作为模型细胞膜的各种脂质单层或双层以及它们与许多不同分子的相互作用已经使用SFG进行了广泛的研究。在这里，我们使用不同的实验几何结构，即，棱镜几何形状（全内反射）和窗口几何形状（外反射）。使用不同的实验几何结构检测到的界面脂质单层的不同SFG光谱特征是由于不同的菲涅耳系数和不同振动模式的二阶非线性磁化率张量项之间的相互作用（即，甲基的ss和as模式），在本研究中对其进行了详细分析。因此，理解界面菲涅耳系数和χ（2）张量之间的相互作用是正确理解不同实验几何条件下SFG光谱特征的前提。更重要的是，本文中所得到的信息不应仅限于具有aC 3v对称性的甲基基团;可以期望有效扩展到具有不同分子对称性的界面官能团，甚至手性界面。
Sum frequency generation (SFG) vibrational spectroscopy has been widely employed to investigate molecular structures of biological surfaces and interfaces including model cell membranes. A variety of lipid monolayers or bilayers serving as model cell membranes and their interactions with many different molecules have been extensively studied using SFG. Here, we conducted an in-depth investigation on polarization-dependent SFG signals collected from interfacial lipid monolayers using different experimental geometries, i.e., the prism geometry (total internal reflection) and the window geometry (external reflection). The different SFG spectral features of interfacial lipid monolayers detected using different experimental geometries are due to the interplay between the varied Fresnel coefficients and second-order nonlinear susceptibility tensor terms of different vibrational modes (i.e., ss and as modes of methyl groups), which were analyzed in detail in this study. Therefore, understanding the interplay between the interfacial Fresnel coefficients and χ(2)tensors is a prerequisite for correctly understanding the SFG spectral features with respect to different experimental geometries. More importantly, the derived information in this paper should not be limited to the methyl groups with aC3vsymmetry; valid extension to interfacial functional groups with different molecular symmetries and even chiral interfaces could be expected.