Emulsion-confined self-assembly of colloidal nanoparticles into 3D superstructures

Organizing colloidal particles into 3D superstructures is a promising strategy for fabricating functional metamaterials with novel optical, electric, and catalytic properties. The rich surface properties of colloidal particles provide many ways to manipulate their assembly behavior. Emulsion droplets are ideal microspaces for confining colloidal self-assembly, offering many advantages such as versatility, scalability, and controllability over size, shape, and composition. In this review, we first introduce recently developed strategies for the emulsion-confined assembly of colloidal particles into 3D superstructures by manipulating the interfacial properties of the emulsion droplets and colloidal particles, then demonstrate the novel collective properties of the assembled superstructures and highlight some of their unique optical and catalytic properties andapplications in bioimaging, diagnosis, drug delivery, and therapy.