自组装膜/水界面水分子和氢键结构的和频光谱研究

Although self-assembled monolayers (SAMs) play an important role and have been widely applied in both science and industrial field, it is still badly in need of a deep understanding of the self-assembly mechanism and the relationship between micro-structure and macro-performance, especially the interaction of SAMs molecules and the surrounding molecules at the interface. The existing studies on the wetting properties of the SAMs interface are very limited and controversial, such as the water structure and hydrogen bond as well as the interactions between SAMs molecules and water. This project will use the sum frequency vibrational spectroscopy (SFVS) , which is a second order nonlinear technique with interfacial selectivity and sensitivity, to measure the vibrational spectra of SAMs and water molecules on the interface with the assistance of self-assembled monolayer technique and surface plasmon resonance and then obtain the orientation structure of the SAMs, the structure of the water molecules, the interactions between hydrophilic/hydrophobic tail group and water as well as the influence of the environment (humidity, ion environment, etc). These results will help us to explore the interfacial wetting mechanism of SAMs in molecular level, establish the link between the microscopic properties and functions and provide the theoretical guidance for the surface modification of SAMs.

自组装单分子膜技术（SAMs）已在多个领域得到广泛应用，但自组装机理、微观结构和宏观性能之间关系的研究还非常不足，SAMs分子与周围环境分子的相互作用机理还不明确，很大程度上限制了SAMs的设计和应用。现有研究对SAMs表面水的浸润性即SAMs表面水结构和氢键、SAMs-水相互作用的认识非常有限，仍存在许多悬而未决的问题。拟应用具有界面选择性和高灵敏度的和频振动光谱技术及其分析方法，结合自组装膜技术和金属纳米粒子的表面等离子共振效应，通过测量分析界面上SAMs分子及水分子的振动光谱，获得自组装膜分子在界面的取向结构、自组装膜/水界面上氢键及水分子的结构、亲水/憎水尾端基团与水的相互作用以及外部条件（湿度、离子环境等）对自组装膜界面上水和氢键结构的影响等信息，进而在分子层面探讨SAMs界面浸润性的微观机理、建立SAMs界面微观结构与宏观性质/功能的联系，为材料的自组装膜表面改性提供理论指导。

自组装单分子膜技术（SAMs）已在多个领域得到广泛应用，但自组装机理、微观结构和宏观性能之间关系的研究还非常不足，SAMs分子与周围环境分子的相互作用机理还不明确，很大程度上限制了SAMs的设计和应用。我们通过研究SAMs膜基底以及膜分子的和频振动光谱揭示了自组装膜分子在界面的结构等特征。首先，我们设计了新的相位测量实验装置以提高弱信号的检测能力和准确度，同时分析了相位误差的影响，研究结果为提高和频振动光谱相位测量的精度与准确性提供了指导，为界面分子表面态的检测与分析、及微小信号的探测提供了有效手段。其次，我们研究了常用自组装膜基底Si界面的信号对称性以及Si基底自组装膜分子3-氨基丙基三乙氧基硅烷（APTES）的光谱特性和结构，明确了Si（111）基底和频信号的对称性为三重对称性。对于Si（111）界面修饰的APTES分子，首次观察到NH2的反对称振动峰的和频信号（3436cm-1）。NH2的取向角约27°。加热条件下，3436cm-1峰强度减弱，在3489cm-1处（SSP）出现一个新峰，不满足C2V对称性，猜测可能是处于不同环境下的N-H振动，相关验证还在继续。最后我们还对金表面自组装硫醇（CH3、COOH、OH和CN端基）的SAMs结构进行了研究。