Which Forces Control Supracrystal Nucleation in Organic Media?

Here, two mechanisms of fcc Au supracrystal (assembly of Au nanocrystals) growth are proposed. The sizes of the Au nanocrystals and the solvent in which they are dispersed are major parameters that determine the final morphology of nanocrystal assemblies; films by layer‐by‐layer growth (heterogeneous growth), characterized by their plastic deformation, or well‐defined shapes grown in solution (homogeneous growth). Experiments supported by simulations demonstrate that supracrystal nucleation is mainly driven by solvent‐mediated interactions and not solely by the van der Waals attraction between nanocrystal cores, as widely assumed in the literature. With a low size distribution, gold nano­crystals can crystallize in supracrystals. These mesostructures show different morphologies. Here we show the influence of the nanocrystals size and solvent on the supracrystal nucleation, which controls the supracrystalline shape. Brownian dynamics simulations supported by experiments demonstrate that supracrystal nucleation is mainly driven by solvent‐mediated interactions and not solely by the van der Waals attraction between nanocrystal cores, as widely assumed in the literature. The plastic deformation of film made of these supracrystals is also discussed.