CAREER: Crossing and Controlling the Bulk to Interface Transition: Chemical Profiles of Fluids Near Surfaces

在这个由化学系化学结构、动力学和机理a项目支持的项目中，爱荷华大学的Scott Shaw教授和他的学生正在使用各种光学工具（包括基于激光的技术）来表征吸附在固体材料表面或表面附近的分子的结构和动力学。这项研究的一个关键工具是“动态润湿”（DW）装置，它可以制造厚度从单纳米到几微米（2500万分之一英寸到几千分之一英寸）不等的液体薄膜。通过测量随着薄膜厚度系统变化的光（尤其是红外光）的吸收，可以推断出最接近表面的分子的化学和结构信息。从这项研究中获得的信息和见解对化学研究的其他领域以及催化、腐蚀、润滑和半导体加工等应用技术产生了影响。这个研究项目也作为训练研究生和本科生在物理化学、激光技术和计算科学方面的工具。外展活动包括肖教授的农村学者计划，该计划邀请来自农村地区的有抱负的本科生参加真正的实验室研究经验。Shaw实验室采用的实验策略是围绕动态润湿（DW）技术开发的，该技术可以创建厚度从大约一层到近10微米不等的分子流体膜。这种方法通过选择性地排除不透明的体相，避免了直接观察界面的困难，并允许对界面形成和行为进行详细描述。利用和频产生法（SFG）、偏振调制红外反射吸收光谱法（PM-IRRAS）、拉曼光谱法和变角椭圆偏振光谱法提取液膜的净分子取向和绝对厚度。实验光谱用于对界面分子结构的计算模型和流体动力学模型进行基准测试和验证。最终，这项研究可能会导致理解分子间力和几何约束在距离表面一定距离的化学界面中的作用，推进润滑、摩擦学和多相催化的基础研究。

In this project supported by the Chemical Structure, Dynamics and Mechanisms-A Program of the Division of Chemistry, Professor Scott Shaw and his students at the University of Iowa are employing a variety of optical tools (including laser-based techniques) to characterize the structure and dynamics of molecules adsorbed onto or near the surfaces of solid materials. A key tool in this research is a "dynamic wetting" (DW) apparatus, which can create films of liquids of controlled thicknesses from single nanometers to several microns (25 millionths of an inch to a few thousandths of an inch). By measuring the absorption of light (especially infrared light) as the film thickness is systematically varied, chemical and structural information about the molecules nearest the surface can be deduced. The information and insights gained from this research have impacts in other fields of chemistry research, as well as applied technologies such as catalysis, corrosion, lubrication, and semiconductor processing. This research project is also serving as a vehicle for the training of graduate and undergraduate students in physical chemistry, laser technology, and computational science. Outreach activities include Professor Shaw's Rural Scholars Program, which engages aspiring undergraduate students from rural areas in genuine laboratory research experiences.The experimental strategy employed in the Shaw laboratory is developed around the dynamic wetting (DW) technique, which creates molecular fluids films with controlled thicknesses from about one monolayer to nearly 10 microns thickness. This approach circumvents difficulties in direct observation of the interface by selectively excluding opaque, bulk phases, and allows detailed descriptions of interface formation and behaviors. The net molecular orientation and the absolute thickness of the fluid films are extracted by sum-frequency generation (SFG), infrared reflection-absorption spectroscopy (IRRAS) with polarization modulation (PM-IRRAS), Raman spectroscopy, and variable angle spectroscopic ellipsometry. The experimental spectra are used to benchmark and validate computational and fluid dynamic models of interfacial molecular structure. Ultimately, this research may lead to an understanding of the roles of intermolecular forces and geometric confinement in creating chemical interfaces at defined distances from surfaces, advancing fundamental research in lubrication, tribology, and heterogeneous catalysis.