Fabrication of double inverse opals via binary colloidal crystals of inorganic-organic core-shell particles and inorganic nanoparticles

A new type of double inverse opals (DIOs) in which a single inorganic sphere was embedded within each inorganic compartment formed by nanoparticles was fabricated via binary colloidal crystals (BCC) composed of submicron-sized core-shell spheres and the nanoparticles. In the fabrication of BCC, submicron-sized silica cores coated with a polystyrene shell and silica nanoparticles with sizes one-tenth smaller than that of core-shell particles were employed as the core-shell spheres and the nanoparticles, respectively. The BCCs fabricated were heated at 550°C for 5 h to selectively remove the polystyrene shell from the BCCs, resulting in mono-layered silica cores embedded in each hemispherical compartment without any overlayers preventing the submicron-sized cores from being optically and physically interacted with the outside. The present work provides a facile fabrication method for inorganic DIOs that will be used for new colloidal architectures.