Study of TiO2 Nanoparticles Irradiated by IR Laser

Flame spray pyrolysis (FSP) is currently used for massive production of oxide nanoparticles with specific properties, which are related to the surface-to-volume ratio. TiO2 nanoparticle synthesis is of the particular interest due to the material catalytic properties. As it is well-known, these catalytic properties are related to a disorder due to the defect states in the forbidden band. In this work we study the light emission from the IR irradiated flame and infer the temperature from the obtained spectra. The anomalous temperature dependence on the laser fluence was found, which was related to the laser effect on the particle disorder. With further comprehension, the found phenomenon may become a basis for the development of a powerful tool for in-situ analysis of nano-oxide produced in flames. Besides its importance for the characterization of materials produced by the gas-phase synthesis, our results may shed light on the long-existing puzzle relating to the laser-induced incandescence (LII) fundamentals. We discuss that another our finding, which reveals a significant drop in the radiation intensity at the short wavelengths, can be interpreted as the thermal isolation between electrons and phonons inside the nanoparticle after the laser pulse. The latter hypothesis was recently introduced as a way to revisit the current LII practice.