Abstract: Functional materials built from nanocrystals and nanocrystal assemblies are enabling new applications in renewable energy conversion, optoelectronics, nanomedicine, among others. Essential to the realization of materials-by-design is to elucidate synthetic pathways and understand the kinetics of structural transitions. The process of nanocrystal assembly, analogous to a chemical reaction, usually traverses a complex free-energy landscape before reaching the final state. Therefore, we must begin to think of assembly as a reaction pathway connecting multiple nonequilibrium intermediates. Fully understanding these pathways requires real-space, real-time characterization with meaningful spatiotemporal resolution, which is not by possible with existing ex-situ characterization or scattering-based methods.

In the first part of this talk, I will discuss our recent advances on direct imaging of nanocrystal assembly using in-situ liquid cell transmission electron microscopy. The nanocrystal interaction potential can be readily tuned by changing the solvent, which enabled observation and quantitative analysis of nonclassical crystallization pathways for nanocrystal superstructures. Next, I will discuss our work on the design of Cu-based multimetallic nanocrystals by establishing distinct synthetic pathways during seeded growth. These well-defined nanomaterials are promising electrocatalysts for high-rate, selective conversion of chemical feedstocks into value-added products.

Bio: Xingchen Ye is an Assistant Professor in the Department of Chemistry at Indiana University Bloomington (IUB). He earned his PhD in Chemistry from University of Pennsylvania and a B.S. in Chemistry from University of Science and Technology of China.