In and Out-Of-Equilibrium Assembly Dynamics of Nanoparticles

In this talk, I will discuss our recent efforts on utilizing liquid-phase TEM imaging and associated machine-learning or computational simulation methods to understand the fundamental colloidal forces in both equilibrium and out-of-equilibrium assemblies of nanoparticles. Anisotropic gold nanoparticles are our model systems, with intriguing plasmonic properties and directional interactions. We study their nucleation pathway and growth habits in real-time in solution at the nanometer resolution, where colloidal interactions balance with mass transport to ultimately determine the size, shape and surface morphology of assembled superlattice. We study the phononic relaxation of the superlattices, where complex colloidal interactions act effectively as nanoscale springs to determine the collective structural reconfiguration. Going beyond equilibrium dynamics, we also study the external field driven assembly of nanoparticles, where hydrodynamic effects drive the nanoparticles into active “swarms” with rapidly-changing patterns. We will show new structural control and new functional relevance in these particulate systems, when we consider both the colloidal interactions and all the other factors such as diffusivity, many-body effects, and ionic flows.