An In Situ look at Interfacial Structure and Dynamics during Nucleation and Self-Assembly

Interfaces play a critical role in nucleation and growth from solutions by altering the distribution of water and ions from that of the bulk, introducing an interfacial free energy that largely determines the free energy barrier to nucleation, and creating an entropic repulsion that acts as a volume exclusion force to drive colloidal assembly. The origin and characteristic length scales of these phenomena are inherently atomic-to-molecular but are manifest in ensemble dynamics and outcomes. Moreover, processes like nucleation and self-assembly arise from fluctuations, making the events that must be probed transient in nature. Consequently, in situ imaging techniques that can capture structure and its evolution, particularly at high speed and atomic-to-nm resolution, are required to build a quantitative picture of such processes. Here I use examples from and <i>in situ</i> TEM, high-speed AFM, and fast force mapping studies of interfacial structure, nucleation, and particle assembly to elucidate the mechanisms by which interfaces direct these processes, leading to unique pathways, materials, and morphologies. The results reveal the importance of surface charge, chemical gradients, and solvent organization near interfaces in determining how ordered materials emerge from the solution.