The inverse opals of composite ZnO/TiO2 and TiO2/ZnO bilayers

The inverse opal structure holds a lot of interesting properties that can be exploited for the use of photocatalysis. TiO2, ZnO, and composite inverse opals were synthesised with the aim of producing a photocatalytic layer and investigating the changes during the preparation of the structure, focusing the annealing of the material during the removal of the sacrificial polystyrene opal template. First, monolayers and bilayers were synthesised using atomic layer deposition on Si substrates, and their structures were explored before and after heat treatment. The composite bilayers showed deformations on the surface under electron microscopy, namely humps and holes. Second, inverse opals were prepared using vertical deposition of polystyrene nanospheres, atomic layer deposition of TiO2 and ZnO, and heat treatment. The surface and bulk (structural) properties were analysed using water wettability tests, SEM-EDX, XRD, and UV-Vis spectroscopy methods. Photocatalysis experiments were carried out using UV and visible irradiation of rhodamine 6G solution; interestingly, the performance of the ZnO, TiO2 and composite inverse opals depends on the type of irradiation.