报告人：Dr. WU Liheng, Department of Chemical Engineering, Stanford University, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory
Synthesizing nanocrystals with precisely controlled size, shape, and structure is of great importance for understanding their properties, especially catalysis. Although significant developments have been achieved in colloidal synthesis in the past two decades, it remains challenging to synthesize nanocrystal catalysts in a predictive way due to a lack of mechanistic understanding of the synthesis. In this seminar, I will discuss my recent research efforts on using synchrotron-based X-ray scattering to investigate the formation mechanisms of nanocrystals in real time under typical colloidal synthetic conditions in order to accelerate their rational synthesis for catalytic applications.
The first part of this talk describes using in situ small angle X-ray scattering (SAXS) to elucidate the formation kinetics of monometallic Pd nanocrystals in the presence of different ligands. The quantitative understanding provides the basis for precisely synthesizing a broad library of monodisperse Pd nanocrystals with 1 nm size control for studying their size-dependent catalysis. In the second part, I will discuss an unprecedented rapid crystallization of nanocrystals into three-dimensional superlattices at high temperatures and their continuous growth within the superlattice structures observed using in situ SAXS, which provides new insights on interparticle interactions during colloidal synthesis. Finally, by coupling the SAXS with wide angle X-ray scattering (WAXS), I will demonstrate real-time probing the formation of bimetallic PtSn nanocrystals at the atomic scale with high temporal resolution using the synchrotron X-ray scattering. This type of in situ characterization can be readily extended to other multimetallic systems to advance their synthetic design.
Liheng Wu received his B.Sc. in Materials Science from University of Science and Technology of China (USTC) in 2009. He obtained his Ph.D. in Chemistry from Brown University in 2015, working with Prof. Shouheng Sun on precise synthesis and self-assembly of monodisperse nanocrystals for magnetic and catalytic applications. During his Ph.D., he received the Sigma Xi Award for Excellence in Graduate Research from Brown University. Since November of 2015, he has been working as a postdoctoral fellow at Stanford University and SLAC National Accelerator Laboratory. His current research focuses on in situ synchrotron X-ray characterization of nanocrystals for catalytic applications. During his academic training, he has published over 20 research papers, including several first-authored papers published in Nature, JACS, Nano Letters, and Chemical Reviews. He has also served as a reviewer for many journals, including Advanced Materials, Advanced Energy Materials, Advanced Functional Materials, Nanoscale, Small, Nano Research, and Catalysis Science & Technology.