Optical Properties and Photostability of Microsized TiO2 Powders Modified with its Own Nano- and Hollow Particles

Comparative studies of the optical properties and photostability of pristine microsized TiO2 powder and modified with its own nano- and hollow particles have been carried out. It was established that the reflection coefficient (ρ) decreases down to 3.5% in the visible region and increases up to 3–4% in the near-IR region at a 3 wt% concentration of nano- and hollow TiO2 particles. Powders irradiation with intensive solar radiation causes an appearance of absorption bands with maxima at 420 nm and 800–1200 nm in the difference diffuse reflection spectra. In the spectra of the powder modified with hollow particles, the bands with lower intensity shift to shorter wavelengths—to 410 and 750–800 nm. An increase in irradiation time from 5 to 40 h results in the intensity increasing of such bands. It was found that a greater effect was obtained upon modification with hollow particles in comparison with TiO2 nanoparticles. Photostability of the powders modified with hollow particles is more than 4.6 times higher than for unmodified one and it was compared with powders modified with SiO2 and ZrO2 nanoparticles. An explanation of the results obtained is given.