The water/oil interface: The emerging horizon for self-assembly of nanoparticles

This article highlights our recent achievement on directing nanoparticles to self-assemble at the water/oil interface. We demonstrate that the contact angle of 90° is prerequisite for nanoparticles to localize at the interface, which is determined by the terminal groups of the capping ligands. With this peculiar surface wettability, nanoparticles of different sizes and chemical composition may self-assemble into homogeneous or composite thin films at the water/oil interface. The interfacially active nanoparticles may be employed to stabilize water-in-oil or oil-in-water droplets, creating the microcapsules whose shells are composed of randomly close packed nanoparticles. The permeability of the resulting microcapsules is defined by the sizes of the nanoparticles used.