Photodeposition synthesis of a ZnO nanoporous layer

Abstract

An original photodeposition methodology is investigated to synthesize novel ZnO nanoporous layers with high uniformity and pore density via TiO₂ nanotube substrates (annealed at 450 °C under 10⁻² Pa for 8 hours) immersed in Zn(NO₃)₂ aqueous solution (1 mol L⁻¹) and irradiated by ultraviolet (UV) light at room temperature for 12 hours. Characterization of the material highlights that the nanoporous layer is assembled by the dominant (101) crystal plane of hexagonal wurtzite ZnO with a vertical sheet thickness of about 20 nm and an aperture diameter of around 100 nm. Vacuum annealing of the TiO₂ substrate ultimately impacts the uniformity of the ZnO nanoporous layer, which can be essentially attributed to the density of the substrate oxygen vacancies. However, the concentration of the Zn(NO₃)₂ aqueous solution significantly influences the morphology and pore density of the porous layer. Furthermore, the ZnO nanoporous layer enhances the photoelectric properties of pure TiO₂ nanotubes, which may provide general application prospects in photocatalysis and photoelectric devices.