Effect of laser and temperature treatment on the optical properties of titanium dioxide nanoparticles prepared via pulsed 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 TiO2, it is necessary to extend the spectral range of its absorption to the visible region. In this work, nanocolloids of dark titanium dioxide, initially prepared by pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) in water, are subjected to an additional laser treatment from the same source. Colloidal solutions are dried and TiO2 powders are annealed. A comparative analysis of the optical properties of the materials prepared with and without extra treatment by the methods of diffuse reflection spectroscopy, fluorescence, and Raman spectroscopy is carried out. The bandgap of the materials is estimated, and the nature of the defect states responsible for intense absorption in the visible region of the spectrum is determine