Selective synthesis of TiO2 single nanocrystals and titanate nanotubes: a controllable atomic arrangement approach via NH4TiOF3 mesocrystals

Abstract

Nanostructured titania and titanate have been considered as very important materials used in photocatalysis, photovoltaics, gas sensing and other electronic industries. In principle, their common structural feature is that the precursor phase involving TiO₆ octahedra or similar building units may be converted to any of the nanostructured titania and titanate forms in a controllable way. Based on the atomic arrangement of ionic liquid-mediated NH₄TiOF₃ mesocrystals, TiO₂ nanocrystals and titanate nanotubes were selectively obtained in H₃BO₃ and NaOH media, respectively, by using a simple hydrothermal method. Interestingly, the titanate nanotubes were successfully formed by extraction of NH₄⁺ and F from NH₄TiOF₃ in a milder alkaline environment as low as 1 M NaOH, rather than conventional treatment of TiO₂ in 10 M NaOH. The as-prepared TiO₂ nanocrystals with exposed {001} facets exhibit a high photocatalytic activity and sedimentation rate as compared to commercial TiO₂. Upon further doping or ion-exchange, the newly prepared TiO₂ nanocrystals will show potential applications in the environment.