A general strategy towards controllable replication of butterfly wings for robust light photocatalysis

Abstract

Large-scale replication of the hierarchical microstructure of bio-template is a long-standing challenge due to the large shrinkage when the bio-templates are burned off. In this work, TiO2 based biomimetic metamaterials have been successfully synthesized by sputtering technique, followed by tape assisted transferring and thermal oxidation process. Tile-like arrays of the scale replicas with ridge-lamellae hierarchical microstructures have been obtained and exhibit bright blue-purple structure color. More interestingly, they exhibit significantly enhanced photocatalytic activity to decompose methylene blue under solar light illumination, with the degradation rate of methylene blue almost five times that of TiO2 thin films with the same sample area. The enhancement on the visible light photocatalytic activity in TiO2 replicas can be attributed to a synergy effect of the presence of Ti3+ doping, the air-TO2 interaction, and hierarchical microstructure. The controlling factors that affect the microstructure, structural color and photocatalytic activity of the TiO2 replicas have been discussed in detail. This work offers a scalable and precise approach to replicate various bio-templates based on transition metal oxides, such as ZnO, Fe3O4, CoO, and VO2, thereby providing the new opportunity for infrared sensing, photocatalytic and photonic applications.