Much of current materials research is about understanding, controlling and manipulating structures of a few to hundreds nanometers in size, especially materials for energy and environment. The nanostructures are intermediate between single molecules and bulk crystals, and their properties differ from those of molecules or large crystals. Among various forms of nanostructures, nanoparticles or nanocrystals often present structural properties that vary dramatically with size. A major motivation for studying nanocrystals is that they are often used as synthetic catalysts in chemical reactions with high turnover and selectivity or cathode materials in batteries.
While significant progress has made toward to single nanoparticle diffraction using synchrotrons and free electron lasers, electrons have large scattering cross sections and can be focused into small probes that are ideal for single nanoparticle diffraction. The challenges are the quantification of electron diffraction data and 3D data collection, Using atomic resolution electron imaging, diffraction, and spectroscopy, we have studied nanocrystal surfaces, interfaces and chemical transformation. In each case, we have found surprisingly rich interfacial phenomena. We have also made progress in developing techniques for in-operando study of chemical reactions using HREM performed in an environmental TEM. The progress will be presented here. The contribution of several Ph.D. students’ research and collaborations with several research groups is greatly acknowledged. The research was supported by NSF DMR.