Structure-tunable synthesis of titanate nanotube thin films via a simple hydrothermal process

In this study, titanium metal acts as the titanium source to prepare oriented titanate nanotube thin film. The effects of preparation parameters, such as reaction temperature, duration and post-treatment conditions, on the film morphology and stability have been examined. A general formation mechanism for oriented titanate nanotube thin film is proposed on the basis of detailed observations of the products using two-dimensional surface SEM studies and TEM images. The overall formation of titanate nanotubes can be summarized as a sequence of four steps: (a) titanium dissolution and alkali titanate hydrogel formation; (b) alkali titanate hydrogel dissolution, increased TiO32−, TiO2(OH)22− or TinO2n+m2m− concentration and layered Na2Ti3O7 formation; (c) layered Na2Ti3O7 growth; (d) nanotube formation via Na2Ti3O7 splitting and the multilayer scrolling process. The Na2Ti3O7 lamellar structures split between the (010) planes into nanosheets.