No abstract

Hierarchical nanostructures have attracted increasing interest due to their exceptional properties and widespread potential applications. In this paper, anatase TiO2 hollow nanoboxes (TiO2-HNBs) are formed by assembly of nanosheets with exposed {001} facets by solvothermal treatment of TiOF2 cubes in alcohols (tert-butanol and ethanol) at 180 °C. It was found that phase transformation of TiOF2 to anatase TiO2 begins at corners and edges of TiOF2 cubes due to in situ hydrolysis of TiOF2, where water was produced by dehydration of alcohol molecules. With extension the reaction time, TiO2-HNB assemblies from nanosheets with exposed high-energy {001} facets were formed due to the steady inside-outside dissolution-recrystallization process. However, the resulting hierarchical TiO2-HNBs are unstable, which can decompose to discrete high-energy TiO2 nanosheets if the reaction time is further extended. The hierarchical TiO2-HNBs show higher photocatalytic activity than discrete high-energy TiO2 nanosheets and P25 TiO2 due to the unique structures of TiO2-HNBs.

A novel hierarchical anatase TiO 2 hollow microsphere (TiO 2 -HMS) assembly synthesised from TiO 2 hollow nanoparticles (TiO 2 -HNP), denoted TiO 2 -HMS-HNP, was rapidly fabricated by a simple hydrothermal route in a Ti(SO 4 ) 2 -NH 4 F-H 2 O 2 mixed solution at 180 uC for only 3 h. The influence of NH 4 F and H 2 O 2 on the formation of TiO 2 -HMS-HNP was studied. A novel mechanism for the formation of TiO 2 -HMS-HNP based on a H 2 O 2 -assisted fluoride-induced self-transformation (FIST) process is proposed. The prepared TiO 2 -HMS-HNP showed much higher photocatalytic activity than TiO 2 -HMS, when the activity was evaluated both by the photocatalytic degradation rate of brilliant red X-3B (an anionic azo dye) and by the rate of formation of photo-induced hydroxyl radicals ( ? OH) under UV irradiation.