Surfactant-Assisted Emulsion Self-Assembly of Nanoparticles into Hollow Vesicle-Like Structures and 2D Plates

The emulsion-based self-assembly of nanoparticles into low-dimensional superparticles of hollow vesicle-like assemblies is reported. Evaporation of the oil phase at relatively low temperatures from nanoparticle-containing oil-in-water emulsion droplets leads to the formation of stable and uniform sub-micrometer vesicle-like assembly structures in water. This result is in contrast with those from many previously reported emulsion-based self-assembly methods, which produce solid spherical assemblies. It is found that extra surfactants in both the oil and water phases play a key role in stabilizing nanoscale emulsion droplets and capturing hollow assembly structures. Systematic investigation into what controls the morphology in emulsion self-assembly is carried out, and the approach is extended to fabricate more complex rattle-like structures and 2D plates. These results demonstrate that the emulsion-based assembly is not limited to typical thermodynamic spherical assembly structures and can be used to fabricate various types of interesting low-dimensional assembly structures.