New type of inverse opals: Titania with skeleton structure

A skeleton structure, consisting of titania cylinders connecting the tetrahedral and octahedral voids among the close-packed spheres of an opal template, was prepared by using an intra-template condensation process of titania among close-packed monodispersed polystyrene particles with a size of 270 nm. Theoretical calculations show that this kind of structure can exhibit a novel band gap in a lower frequency range than known inverse opals and even two complete band gaps. The realization of the titania skeleton is regarded as the first step toward a qualitative band structure tuning for inverse opals.