讲座题目：Revealing Unseen Materials Dynamics in Liquids by In Situ Electron Microscopy
讲 座 人：郑海梅
Lawrence Berkeley National Laboratory (LBNL)
University of California, Berkeley (UC Berkeley)
时 间：2014年10月30日（周四） 16:00-17:00
地 点：厦门大学 同安二楼201会议室外间
郑海梅 教授
Dr. Zheng received her Ph.D degree in Materials Science and Engineering from University of Maryland (UM), College Park in 2004. Prof. Ramamoorthy Ramesh at UC Berkeley and Prof. Lourdes Salamanca-Riba of UM were her Ph.D advisors. She was a postdoc with Prof. Paul Alivisatos in Department of Chemistry at UC Berkeley and jointly at the National Center for Electron Microscopy (NCEM) of LBNL before she became a staff scientist at LBNL in 2010.
Dr. Zheng has published about 70 papers with total citation of more than 5000 times and H index of 29. So far she has 6 papers in Science, in which she was either the first author or corresponding author on 5 of them.
Her recent award includes DOE Office of Science Early Career Award in 2011 and LBNL Director’s award for exceptional scientific achievements in 2013.
欢迎广大师生踊跃参加！
能源材料化学协同创新中心
2014年10月16日
附 - 报告摘要：
Revealing Unseen Materials Dynamics in Liquids by In Situ Electron Microscopy
Haimei Zheng
1Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
2Department of Material Science and Engineering, University of California, Berkeley, California 94720, United States.
An understanding of how materials grow and transform in their working environments is essential to the development of functional materials for a variety of applications. We study a variety of physical and chemical processes of materials in situ at the nanometer or atomic scale with transmission electron microscopy (TEM). I will first present our latest work on the study of colloidal nanocrystal growth with the focus on shape control mechanisms using a liquid cell under TEM. It is known that nanoparticle catalytic and other surface-enhance properties are highly dependent on the shape of nanocrystals. An understanding of nanocrystal shape control mechanisms during synthesis is critical in order to design novel functional materials. However, nanocrystal facet development and shape evolution during growth are mostly unknown due to the lack of direct observation. With in situ liquid cell TEM we have been able to identify unique growth mechanisms by real time imaging. For example, the direct observation of Pt nanocube growth reveals the facet development drastically different from what is predicted by Wulff construction or other growth theorems. We found that the growth rates of {100}, {110} and {111} facets are similar until the {100} facets stop growth. Subsequently, the {110} facets are eliminated when two adjacent {100} facets meet. At the end, the growth of {111} facets fills the corners to complete a nanocube. Theoretical calculation suggests oleylamine ligand mobility on the facet is likely responsible for the arresting of {100} growing facets. In the second part of the talk, I will present our development of electrochemical liquid cells for in situ study of electrochemical processes for energy storage applications. Examples on the in situ study of phase transformation during electrochemical dissolution and deposition at the electrode-liquid electrolyte interfaces in a Li-S system will be provided.
1. H. G. Liao, D. Zherebetskyy, H. Xin, C. Czarnik, P. Ercius, H. Elmlund, M. Pan, L. W. Wang, H. Zheng*, “Facet development during platinum nanocube growth." Science 345, 916 (2014).
2. Z. Zeng, W. I. Liang, H. G. Liao, H. L. Xin, Y. H. Chu, H. Zheng*, “Visualization of electrode-electrolyte interfaces in LiPF6/EC/DEC electrolyte for lithium ion batteries via in-situ TEM.” Nano Lett. 14, 1745 (2014).
3. H. G. Liao, L. Cui, S. Whitelam, H. Zheng*, "Real time imaging Pt3Fe nanorod growth in solution." Science 336, 1011 (2012).
4. H. Zheng*, J. B. Rivest, T. Miller, B. Sadtler, A. Lindenberg, M. F Toney, L. W. Wang, C. Kisielowski, A. P. Alivisatos, “Observation of transient structural-transformation dynamics in a Cu2S nanorod.” Science 333, 206 (2011).
5. H. Zheng, R. K. Smith, Y. W. Jun, C. Kisielowski, U. Dahmen, A. P. Alivisatos, “Observation of single colloidal platinum nanocrystal growth trajectories.” Science 324, 1309 (2009).
6. We acknowledge the support of US Department of Energy Office of Science Early Career Research Program. We thank the facility support of National Center for Electron Microscopy (NCEM) of The Molecular Foundry at Lawrence Berkeley National Laboratory, which is funded by U.S. Department of Energy Office of Basic Energy Sciences under Contract #DE-AC02-05CH11231.
