A Composite of TiO2 Quantum Dots and TiO2 Nanoparticles Coated on Anti-Bumping Glass Beads (TiO2QDs-TiO2NPs/GBs), with a Very Low Content of TiO2 as a High Performance Photocatalyst

Abstract

A composite of TiO2 quantum dots (TiO2QDs) and TiO2 nanoparticles (TiO2NPs) was successfully deposited on glass beads (GBs), with a very low content of TiO2 (<0.3 wt%), by a rapid, simple, inexpensive, and scalable synthesis method. The TiO2QDs-TiO2NPs/GBs catalyst possesses an extremely high photocatalytic performance under simulated solar irradiation, with the complete degradation of the aqueous solutions of methylene blue in 60 minutes of photodegradation. There were no changes in the catalytic activity after six times of recycling. The superior performance of the catalyst should be attributed to the role of the synergistic effect between TiO2NPs and TiO2QDs to prevent the accumulation of TiO2 nanoparticles during the oxidation reaction, to improve the absorption in the visible region, to enhance the immigration of photogenerated electrons and holes in interfaces of two materials in the TiO2QDs-TiO2NPs composite, which leads to a reduced charge recombination rate, and to generate midgap states and suppress the recombination of electron-hole pairs.