CAREER: Discovering the Mechanisms of Liquid Phase Epitaxy and Bringing Intermolecular Forces to the Physics Curriculum

介观材料的最新突破使固液界面科学重新焕发活力，并将其重点从体热力学描述转移到分子间力。该项目的目标是建立一个中心设施，通过原子力显微镜（AFM）测量和绘制分子间和表面力，并通过学生的研究，发现固体表面在指导相邻液相（液相外延）界面有序形成中的作用。首先，将通过亚稳溶液中的原位成像研究不同衬底上固相的成核和过度生长。研究将集中在生长形态的差异上（湿润型、岛形核型、针状生长型），作为衬底和覆盖层之间相容性的函数。其次，力测量和软接触成像将探索表面活性剂溶液的界面自组装和界面胶束对溶致相的模板化。观察到的界面形态将与基于优化胶束晶格和衬底的净相互作用能的理论计算相关联。温度在结构相变中的作用将利用现有的温度控制单元在水的温度范围内进行探索。参与这项研究的学生将接受凝聚态物理当代领域的培训，从而为进入科学/技术劳动力做好准备。与固体表面接触的液体膜的部分有序是从晶体生长到介观材料合成到边界层润滑等界面过程的核心。本项目的目标是通过原子力显微镜（AFM）测量和绘制分子间作用力来揭示界面有序形成的机制。这项技术使用亚微观尖端或触针来测量分子间的作用力，并通过绘制表面上的力变化来在原子尺度上对表面进行成像。学生实验人员将在液体环境中使用力测量和成像来研究固体表面在从溶液中成核的固体和液晶相中的作用。在过饱和溶液中，一种矿物在第二种紧密匹配的固体上的晶体生长将以分子分辨率实时成像。研究将集中在生长形态的差异以及衬底和覆盖层原子结构之间的不匹配程度。表面活性剂或洗涤剂的液晶相在固体表面的成核也将被研究。在优化表面与表面活性剂聚集层净相互作用能的基础上，将观察到的界面层结构与理论计算相关联。温度对这些相的影响将使用当前运行的特殊样品池进行研究。这些结果有望为界面过程（如去污剂和先进材料的自组装合成）提供新的线索。本研究将由准备在学术界、工业界和政府从事科学/技术工作的学生进行。

Recent breakthroughs in mesoscopic materials have reinvigorated the science of solid-liquid interfaces and shifted its emphasis from bulk thermodynamic descriptions to intermolecular forces. The goals of this project are to establish a central facility for the measurement and mapping of intermolecular and surface forces by atomic force microscopy (AFM) and, through student research, to discover the role of solid surfaces in directing interfacial order formation in an adjoining liquid phase (liquid phase epitaxy). First, the nucleation and overgrowth of a solid phase over a different substrate will be investigated by in-situ imaging in metastable solutions. Studies will focus on differences in growth morphology (wetting vs. island nucleation vs. needle growth) as a function of compatibility between substrate and overlayer. Second, force measurements and soft contact imaging will explore the interfacial self-assembly of surfactant solutions and the templating of lyotropic phases by interfacial micelles. Observed interfacial morphologies will be correlated with theoretical calculations based on optimizing the net interaction energy of the micelle lattice and substrate. The role of temperature in structural phase transitions will be explored using an existing temperature-control cell that operates over the aqueous range of temperatures. The students participating in this research will be trained in a contemporary area of condensed matter physics and will thereby be prepared to enter the scientific/technical workforce.%%%The partial ordering of a liquid film in contact with a solid surface is central to interfacial processes ranging from crystal growth to mesoscopic materials synthesis to boundary layer lubrication. The goals of this project are to uncover the mechanisms of interfacial order formation by the measurement and mapping of intermolecular forces by atomic force microscopy (AFM). This technique uses a sub-microscopic tip or stylus to measure intermolecular forces and to image surfaces at atomic scales by mapping force variations across the surface. Student experimentalists will use force measurements and imaging in liquid environments to investigate the role of solid surfaces in nucleating solid and liquid crystalline phases from solutions. Crystal growth of one mineral on a second, closely matched solid will be imaged in real time and at molecular resolution in supersaturated solutions. Studies will focus on differences in growth morphology versus the degree of mismatch between the atomic structure of substrate and overlayer. The nucleation of liquid crystalline phases of surfactants or detergents by solid surfaces will also be investigated. The observed structures of interfacial layers will be correlated with theoretical calculations, based on optimizing the net interaction energy of the surface and surfactant aggregate layer. The effects of temperature on these phases will be investigated using a special sample cell currently under operation. These results are expected to shed new light on interfacial processes such as detergency and the synthesis of advanced materials by self-assembly. This research will be conducted with students who will be prepared for scientific/technical employment in academia, industry, and government.