Figure 4. Schematic illustration of synthetic process of vertically aligned TiO₂ TNAs and HNTs film on Ti foil substrate.

In this process, the original H-titanate can act as a template to facilitate the shape conversion, while the one-dimensional orientation was still maintained. In the NH₄F system, the TNAs consisting of TiO₂ nanocrystals with exposed {001} facets were obtained. While in the pure water, HNTs with walls made up of numerous octahedrons were formed.