Spectroscopic Studies of Hydrogen Bond Structures, Dynamics, and Relaxation Mechanisms at Aqueous Interfaces

在这个由化学系化学结构、动力学和机制（CSDM）项目资助的奖项中，南加州大学的亚历山大·V·本德斯基教授和他的研究生、本科生和博士后研究生将使用表面选择性非线性光学光谱技术来了解液体界面的分子结构和动力学，特别是氢键的性质。 从概念上讲，正是界面环境的不对称性和由此产生的各向异性相互作用使得界面与本体液体有着根本的不同。 本研究的目的是了解界面水的氢键网络的动力学行为和弛豫机制。 为了实现这一目标，光谱研究将使用振动的水分子本身（OH拉伸和弯曲模式），报告的氢键环境的动态，以及旋转松弛测量的小探针分子，报告的局部微观摩擦和粘度的分子起源。 薄界面区域中的水的性质是重要过程的基础，例如溶剂化、水合、水动力阻力、润湿和两亲性自组装。 这在生物学、生物医学科学、生物工程中具有深远的意义，其中“生物水”薄层的分子性质严重影响界面区域中发生的生物化学和生物物理过程。 松弛过程的机械方面和粘度的分子起源在流体力学和微流体学中有直接的应用。 这项研究将刺激理论发展，并导致更好的计算模型的水和生物界面。 教学和培训各级学生，本科生，研究生和博士后将是这个项目的一个组成部分。 教育、培训和外展活动将包括大洛杉矶都市区代表性不足的少数民族，以及博士后研究生指导。

In this award, funded by the Chemical Structure, Dynamics and Mechanisms (CSDM) Program of the Chemistry Division, Prof. Alexander V. Benderskii of the University of Southern California and his graduate, undergraduate, and postdoctoral research students will use surface-selective nonlinear optical spectroscopy techniques to learn about the molecular structure and dynamics at liquid interfaces, in particular the nature of the hydrogen bonding. Conceptually, it is the asymmetry of the interfacial environment and the resulting anisotropic interactions that make interfaces fundamentally different from bulk liquids. The goal of this research is to understand the dynamic behavior, and relaxation mechanisms of the aqueous H-bond network of the interfacial water. To achieve this goal, spectroscopic studies will be performed using vibrations of the water molecule itself (OH stretch and bend modes) that report on the dynamics of the H-bonding environment, as well as rotational relaxation measurements of small probe molecules that report on the local microscopic friction and the molecular origins of viscosity. The properties of water in the thin interfacial region underlie important processes such as solvation, hydration, hydrodynamic drag, wetting, and amphiphilic self-assembly. This has profound implications in biology, biomedical sciences, bioengineering, where the molecular properties of the thin layer of 'biological water' critically affect biochemical and biophysical processes occurring in the interfacial region. The mechanistic aspect of the relaxation processes and the molecular origins of viscosity have direct applications in hydrodynamics and microfluidics. The research will stimulate theoretical developments and lead to better computational models for aqueous and biological interfaces. Teaching and training students at all levels, undergraduate, graduate, and postdoctoral will be an integral part of this project. The educational, training, and outreach activities will include underrepresented minorities in the greater Los Angeles metropolitan area, as well as postdoctoral research student mentoring.