Solar-light-driven photodegradation and antibacterial activity of hierarchical TiO ₂/ZnO/CuO material

Inspired by the highly efficient hierarchical structure of plants that use natural light, the hierarchical "forest-like" TiO ₂ nanofiber/ZnO nanorod/CuO nanoparticle ternary material 2 is synthesized by a stepwise process: electrospinning of TiO ₂ nanofibers, hydrothermal growth of ZnO nanorods, and photodeposition of CuO nanoparticles. Material 2 has a higher photodegradation rate of acid orange (AO 7) and stronger antibacterial capability under irradiation with solar light in comparison to that of the hierarchical "tree-like" TiO ₂ nanofiber/ZnO nanorod material 1 and one dimensional as-spun TiO ₂ nanofibers. These en-hancements result from the unique hierarchical forest-and tree-like features of materials 1 and 2, which enhance the light absorption capability, increase the specific surface area for mass transfer and bacteria attachment, create more reaction sites, and retard the recombination of photogenerated electrons and holes. A proportional relationship was found between the photocatalytic activity and the hierarchy of the materials. The sizes of the hierarchical nanostructured materials are in the micron range, which provides the opportunity for using these materials in engineering applications.