Surface and Interface Free Energies of Epitaxial Nanocrystals

技术概要：建议研究外延金属纳米晶体的表面能和界面能，并将它们与它们的原子结构相关联。在TiO 2上外延的Au纳米晶体将被用作研究的模型系统。外延提供界面均匀性，并且还提供对纳米晶体形状的更好控制。选择TiO 2是因为其作为催化剂载体的可还原氧化物的功能以及文献中关于其表面的广泛知识。Au纳米晶体将使用PI小组开发的沉积和退火技术合成。像差校正扫描透射电子显微镜和透射电子显微镜将用于表征Au纳米晶体及其界面的结构。的结构数据将被用来测量的表面和界面能的Au纳米晶体的大小的函数。 在理论上，界面和三线的几何形状，局域电子态密度，和能量的Au在不同的外延TiO 2将从第一性原理计算。实验与理论相结合，预计将导致显着提高理解的结构和性能的关系，在表面和interfaces.Non-Technical摘要：材料技术的重要组成部分，化学工业的主要组成部分，以及令人兴奋的新发展，在医疗诊断和治疗依赖于支持的金属纳米粒子的属性。金属纳米粒子的特殊功能来自于纳米粒子与载体表面和界面的协同作用。然而，现代研究在很大程度上避免了负载纳米粒子的复杂性;纳米粒子太小，无法进行实验表征，太大，无法进行严格的理论研究。本计画系利用透射电子显微镜之像差校正在原子解析成像上之最新进展，结合电子显微镜合成与理论，研究电子显微镜之表面与界面。这项研究将与外展工作相结合，包括高中访问和本科教育。该研究项目的结果将被纳入基于网络的教育材料，用于教授学生原子结构和衍射，其基础设施已经到位（见http://emaps.mrl.uiuc.edu/或谷歌网络地图）。这个特别的网站现在被列为在标准透射电子显微镜工作场所学习电子衍射和电子衍射图案索引的最佳网络资源之一。

TECHNICAL SUMMARY: It is proposed to investigate the surface and interfacial energies of epitaxial metal nanocrystals and correlate them with their atomic structure. Epitaxial Au nanocrystals on TiO2 will be used as a model system for study. Epitaxy provides interfacial uniformity and also provides better control of nanocrystalline shapes. TiO2 is selected because of its function as a reducible oxide for catalyst support and the extensive knowledge about its surfaces in the literature. The Au nanocrystals will be synthesized using the deposition and annealing technique developed in the PI's group. Aberration-corrected scanning transmission electron microscopy and transmission electron microscopy will be used to characterize the structure of the Au nanocrystals and their interfaces. The structural data will be used to measure the surface and interfacial energies of the Au nanocrystals as a function of size. On the theoretical front, the interfacial and triple-line geometries, the local electronic density of states, and the energy of Au on TiO2 for different epitaxies will be computed from first-principles. The combination of experiment with theory is expected to lead to significantly improved understanding of the structure and property relationships in nanocrystal surfaces and interfaces.NON-TECHNICAL SUMMARY: Substantial parts of materials technology, major components of chemical industry, and exciting new developments in medical diagnostics and treatments rely on the properties of supported metallic nanoparticles. The unusual functions of metallic nanoparticles come from the synergistic interactions of surfaces and interfaces of nanoparticles and their support. However, modern studies have largely avoided the complexity of supported nanoparticles; nanoparticles are too small for experimental characterization and too big for rigorous theoretical investigations. This project is to study nanocrystal surfaces and interfaces by taking advantage of the recent progress in atomic resolution imaging using aberration-correction in transmission electron microscopy and combining it with nanocrystal synthesis and theory. 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 atomic 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 and electron diffraction pattern indexing in the standard transmission electron microscopy workplace.