Correlation of anatase particle size with photocatalytic properties

The influence of the anatase TiO ₂ particle size on the photocatalytic properties was systematically investigated on the nanometer-size scale. The anatase TiO ₂ crystallite size estimated using the Scherrer equation was varied from 8.0 to 16.4 nm, and the photocatalytic properties were significantly deteriorated with decreasing crystallites size. The photocurrent measurements showed that the charge generation diminished with decreasing TiO ₂ particle size. The bandgap energies were measured as a function of the particle size using UV-Vis spectroscopy in order to investigate the origin of the lowered charge-generation characteristics. The absorption band edge shift was found in the anatase nanocrystallites, which was attributed to the quantum size effect. Therefore, the increased bandgap energy induced the low light absorption capability, which was responsible for the low photoactivity of the very tiny anatase nanoparticles. These findings demonstrated that the particle-size reduction was not the best way to maximize the photocatalytic properties of TiO ₂ because of the diminished light absorption.