Nanocrystal Surface and Interfacial Free Energies on Vicinal Surfaces

非技术总结：本研究主要关注纳米结构材料研究中的基本挑战：如何确定其界面结构和热力学性质。提出了综合、表征和建模工作来解决这一挑战。表面和界面性质将被测量和计算支持纳米颗粒和相关的结构。预计研究结果将直接影响对技术的重要部分、化学工业的主要组成部分以及医学诊断领域令人兴奋的新发展至关重要的材料。这项研究将与拓展工作相结合，包括高中访问和本科教育。这个研究项目的结果将被纳入基于网络的教育材料中，用于教授学生有关结构和衍射的知识，这些基础设施已经到位（见http://emaps.mrl.uiuc.edu/或谷歌webmaps）。这个特别的网站现在被列为学习电子衍射的最佳网络资源之一。技术概述：提出了一种结合实验和理论的方法来测定表面和界面能以及与原子结构的关系。在氧化物上支持的外延金纳米晶体将使用PI小组开发的技术合成。像差校正扫描透射电子显微镜（STEM）和透射电子显微镜（TEM）将用于表征金纳米晶体的平衡形状及其界面结构。结构数据将用于根据第一性原理计算界面和阶跃能量，并将其与基于负载纳米晶体平衡形状的实验测量结果进行比较。实验部分利用了电子显微镜的最新发展，该技术有望通过深度切片对界面上的氧原子进行成像以及界面结构的三维成像。理论上，将使用能量密度法来计算表面和界面处的能量分布。该计划建立在在扁平金红石（110）表面上支撑的金纳米晶体上取得的进展的基础上，并将研究扩展到邻近表面，以实现阶跃能量的测量。

NON-TECHNICAL SUMMARY: This research focuses on the fundamental challenge in the study of nanostructured materials: how to determine their interfacial structure and their thermodynamic properties. A combined synthesis, characterization and modeling effort is proposed to address this challenge. Surface and interfacial properties will be measured and computed for supported nanoparticles and correlated with structure. Results are expected to have a direct impact on materials that are critical to substantial parts of technology, major components of the chemical industry, and exciting new developments in medical diagnostics. The research will be integrated with outreach efforts, including high school visits and undergraduate education. Results from this research project will be incorporated in the web-based educational materials for teaching students about structure and diffraction, infrastructure for which is already in place (see http://emaps.mrl.uiuc.edu/ or google webemaps). This particular website is now listed as one of the best web resources for learning electron diffraction.TECHNICAL SUMMARY: A combined experimental and theoretical study is proposed for the determination of surface and interface energies and correlation with atomic structure. Epitaxial Au nanocrystals supported on oxides will be synthesized using techniques developed in the PI's group. Aberration corrected scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) will be used to characterize the equilibrium shapes of Au nanocrystals and as well as their interfacial structure. The structural data will be used to compute interface and step energies from first principles, which will be compared with experimental measurements based on the equilibrium shapes of supported nanocrystals. The experimental part takes the advantage of recent developments in electron microscopy, which promise imaging of oxygen atoms at the interface as well as 3D imaging of interfacial structure by depth sectioning. For theory, an energy density method will be used to compute energy distribution at surfaces and interfaces. The program builds upon the progress that has been made on Au nanocrystals supported on flat rutile (110) surfaces, and extends the study to vicinal surfaces to enable a measurement of step energies.