November 2020
Vol 6, Issue 48

About The Cover

Cover image expansion

ONLINE COVER For decades, scientists have explored how solids assemble at a liquid interface—a process that is central to ore purification, emulsions, and encapsulation. To better understand the mechanism by which nanoparticle surfactants attach to the interface, Chai et al. used laser scanning confocal microscopy and in situ atomic force microscopy to directly observe that early-stage attachment of nanoparticles to the interface is diffusion-limited. The researchers found that electrostatic interactions between nanoparticles and ligands result in the formation of nanoparticle surfactants that assemble at water-oil interfaces and form jammed structures, producing a solid-like layer. As the areal density of the nanoparticle surfactants increases, further attachment requires cooperative displacement of the previously assembled nanoparticle surfactants both laterally and vertically. The high spatial and temporal resolution of their observations reveals the complex mechanism of attachment and the nature of the assembly. [CREDIT: ELLA MARU STUDIO]