Optical assembly of nanostructures mediated by surface roughness

TL;DR

This paper investigates how surface roughness influences the optical self-assembly of nanocrystals, revealing that contact dynamics driven by surface texture are crucial for assembly processes.

Contribution

It provides the first direct evidence that nanocrystal surface roughness affects assembly via hydrodynamic resistivity, highlighting the importance of dynamics alongside energetics.

Findings

Surface roughness determines contact and assembly behavior.

Hydrodynamic resistivity depends on nanocrystal surface texture.

Dynamics play a key role in non-equilibrium self-assembly.

Abstract

Rigorous understanding of the self-assembly of colloidal nanocrystals is crucial to the development of tailored nanostructured materials. Despite extensive studies, a mechanistic understanding of self-assembly under non-equilibrium driven by an external field remains an ongoing challenge. We demonstrate self-assembly by optical tweezers imposing 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 self-assembly. These results have implications in a wide variety of different fields, such as in understanding the factors that mediate oriented attachment-based crystal growth or in interpreting the structure of binding sites on viruses.