An approach toward TiO2 nanostructure growth with tunable properties: Influence of reaction time in a hydrothermal process

• TiO2 thin films with different reaction time were prepared by hydrothermal method.
• The microstructure, photoluminescence, Raman and optical properties were investigated.
• The surface morphology shows obvious change with increasing reaction time.
• The optical properties, photoluminescence and Raman properties are influenced by reaction time.
• The ratio of Ti:O is 1:2.206 and close to the atom ratio of TiO2.

An approach has been developed to prepare TiO2 thin films with tunable morphology and physical properties by changing reaction time (6, 12 and 24 h) in a hydrothermal process. As the reaction time increases, anatase TiO2 (1 0 1) preferred orientation is weaken, corresponding to surface morphology changes from one-dimensional nanowire structure to two-dimensional sheet structure then to three-dimensional nuts structure. Evolution of these structural are accompanied by significant variations of optical properties, photoluminescence and Raman properties including a widening of the band gap from 3.21 to 3.24 eV, strong luminescence in the visible area, increase of Raman characteristic peak intensity and frequency shift phenomenon of Raman characteristic peaks. Compositional analysis indicates that TiO2 surface layer contains Ti and O elements, the ratio of Ti:O is 1:2.206 which is close to the atom ratio of TiO2. These findings help to grow specific TiO2 thin films with desired structure and properties for device applications.