Surface and Interface Free Energies of Epitaxial Nanocrystals

点击翻译按钮获取中文摘要

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.