Photonic spheres by microgel templating [Invited]

Abstract

We report on fabricating photonic spheres by combining submicron-sized microgels and silica nanoparticles. By emulsifying the mixture and removing water through solvent drying, we achieve spheres of packed microgels measuring from a few micrometers to tens of micrometers. The highly swollen microgels exert pressure on the surrounding silica nanoparticles, forming a foam-like network within the droplet. The polymer microgels are then removed by calcination, leaving behind a silica foam. These photonic spheres exhibit structural colors in the visible spectral range, including challenging shades like red. The versatile approach we present here can pave the way for designing photonic pigments and be a step forward in understanding inverse structures with spherical morphology.