Synthesis and Photocatalytic Property of ZnO/TiO2 Inverse Opals Films with Controllable Composition and Topology

A novel method to fabricate composition- and topology-controlled ZnO/TiO₂ inverse opals (IO) films using a positive sacrificial ZnO IO template has been developed. This method includes a two-step process, preparation of ZnO IO by a simple electrochemical deposition using a self-assembly polystyrene colloidal crystal template and preparation of ZnO/TiO₂ IO by a liquid phase deposition (LPD) process at room temperature. The composition and topology of ZnO/TiO₂ IO can be easily controlled by changing the duration of the LPD. After 20 min LPD process, a ZnO/TiO2 composite IO with non-close-packed face-centered cubic air sphere array was obtained. Prolonging the duration to 60 min, a pure TiO₂ IO (TIO-LPD60) with obviously thickened walls was formed. The formation mechanism for the compositional and topological variation was discussed. A preliminary study on UV photocatalytic property of the samples for degradation of methylene blue reveals that the composition and topology significantly influenced the photocatalytic activity of the IO film. The ZnO/TiO₂ composite IO demonstrates a higher degree of activity than both pure ZnO and pure TiO₂ IO, although they have a similar IO wall thickness. Moreover, with increasing IO wall thickness from ～52 nm to ～90 nm, TIO-LPD60 exhibits the highest level of photocatalytic performance.