Mediation of Colloidal Encounter Dynamics by Surface Roughness

Rigorous understanding of assembly in colloidal systems is crucial to the development of tailored nanostructured materials. Despite extensive studies, a mechanistic understanding of the dynamics governing encounters of colloidal particles remains an ongoing challenge. We study colloidal encounter dynamics by inducing assembly through optical tweezers that impose an external attractive field for cubic-phase sodium yttrium fluoride nanocrystals. We show that surface roughness of the nanocrystals is a decisive factor for contact leading to assembly between the nanocrystals, manifested by the roughness-dependent hydrodynamic resistivity. This provides direct evidence that dynamics are equally important to energetics in understanding assembly.