"Dynamics and Emergent Complexity in Functional Nanocrystals and Nanocrystal Superstructures"
Assistant Professor Xingchen Ye - Department of Chemistry, Indiana University
Host: David Masiello and Brandi Cossairt

Functional materials built from nanocrystals and nanocrystal superstructures are enabling new applications in energy conversion and storage, 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 techniques. 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 interaction potential between nanocrystals can be readily tuned by changing the solvent, which enabled observation and quantitative analysis of nonclassical crystallization pathways for nanocrystal superstructures. In the second part of this talk, I will introduce our work on creating shape-controlled dilute metal alloy nanocrystals by establishing distinct synthetic pathways during seeded-mediated growth. These well-defined nanocrystals are promising electrocatalysts for high-rate, selective conversion of chemical feedstocks into value-added products.

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