Nanocrystal Surface and Interfacial Free Energies on Vicinal Surfaces

非技术综述：这项研究集中在纳米结构材料研究中的根本挑战：如何确定它们的界面结构和热力学性质。为了应对这一挑战，提出了一种综合的合成、表征和建模工作。将测量和计算负载型纳米颗粒的表面和界面性质，并将其与结构相关联。预计结果将对材料产生直接影响，这些材料对技术的重要部分、化学工业的主要成分以及医疗诊断领域令人兴奋的新发展至关重要。这项研究将与推广工作相结合，包括高中访问和本科教育。这一研究项目的成果将被纳入网络教育材料，用于教授学生关于结构和衍射的知识，基础设施已经到位(见http://emaps.mrl.uiuc.edu/或谷歌网站地图)。这个特殊的网站现在被列为学习电子衍射的最好的网络资源之一。技术摘要：提出了一项实验和理论相结合的研究，以确定表面和界面能以及与原子结构的关联。以氧化物为载体的外延Au纳米晶将使用PI‘s组开发的技术来合成。用像差校正的扫描电子显微镜(STEM)和透射电子显微镜(TEM)表征了Au纳米晶的平衡形状及其界面结构。结构数据将用于从第一性原理计算界面能和台阶能，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，它承诺通过深度切片对界面上的氧原子进行成像，并对界面结构进行3D成像。在理论上，将使用能量密度方法来计算表面和界面的能量分布。该计划建立在金红石(110)平面上负载的Au纳米晶所取得的进展的基础上，并将研究扩展到邻近表面，以实现对台阶能量的测量。

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.