Effect of laser and temperature treatment on the optical properties of titanium dioxide nanoparticles prepared via pulse laser ablation
Nanomaterials based on titanium dioxide are of considerable interest as promising photocatalysts for water and air purification and hydrogen generation. To increase the efficiency of TiO<sub>2</sub>, it is necessary to expand the spectral range of absorption to the visible region. In this work, the nanocolloids of dark titanium dioxide which was initially prepared by pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) in water were subjected to additional laser irradiation with the same source. Colloidal solutions were dried and TiO<sub>2</sub> powders were annealed. A comparative analysis of the optical properties of materials prepared with and without extra irradiation by the methods of diffuse reflection spectroscopy, fluorescence, and Raman spectroscopy has been carried out. The optical band gap of the materials was estimated, and the nature of defect states responsible for intense absorption in the visible region of the spectrum was determined.