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Thermostability of TiO2 nanoparticle and its Photocatalytic Reactivity at Different Anatase/Rutile Ratio

Thermostability study of commercial P25 TiO2 nanoparticles was carried out by ascending annealing temperature from 400 to 1100 C. The thermostability of TiO2 structure was measured by X-ray diffraction (XRD). Anatase-Rutile phase transition occurred only when temperature exceeds 600C. Rutile weight fraction increased from 25 to 100 % between 400 to 840 C. Phase transition activation energy was calculated by using Arrenhius plot to be 27 kJ/mol. Transmission electron microscope (TEM), Brunauer-Emmett-Teller (BET), and dynamic light scattering (DLS) techniques were applied to determine the size of grown particles. Results of particle size analysis using TEM imaging method were the same as those using BET instruments up to 840 C. BET measurements tend to overestimate the particle size at temperature greater than 840 C. In contrast, DLS overestimate the size of TiO2 particles due to agglomeration in solution. Mean TiO2 particle sizes grew from 25 to 450 nm when temperature increased from 400 to 1100 C. Furthermore, the photocatalytic reactivity in the degradation of dye decreased with the increase of particle size and rutile fraction.