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

在这个由化学结构，动力学和机理-化学系的一个项目支持的项目中，爱荷华州大学的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一种“动态润湿”（DW）装置，它可以产生厚度从一纳米到几微米（百万分之二十五英寸到千分之几英寸）的受控液体膜。通过测量薄膜厚度系统变化时的光吸收（特别是红外光），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。这个研究项目也是作为一个车辆的研究生和本科生在物理化学，激光技术和计算科学的培训。Shaw教授的农村学者计划是一项旨在吸引来自农村地区有抱负的本科生参与真正的实验室研究的计划。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可控的分子流体膜，厚度从大约一个单层到近10微米。这种方法通过选择性地排除不透明的体相来避免直接观察界面的困难，并允许详细描述界面的形成和行为。通过和频产生（SFG）、偏振调制红外反射-吸收光谱（PM-IRRAS）、拉曼光谱和变角椭圆偏振光谱提取流体膜的净分子取向和绝对厚度。实验光谱用于基准和验证界面分子结构的计算和流体动力学模型。最终，这项研究可能会导致分子间力和几何约束的作用的理解，在创建化学界面在定义的距离从表面，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.