Engineering of monodisperse mesoporous titania beads for photocatalytic applications.

The properties of monodisperse mesoporous TiO2 beads were readily tuned by varying the temperature (500-800 °C) and time (2-24 h) of calcination for solvothermally treated hexadecylamine/TiO2 hybrid assemblies. The crystal properties (crystal phase, crystallite size, and crystallinity), surface and pore properties (surface hydroxyl groups, surface area, porosity, and pore size), and diameter of the beads were significantly altered with these changes in calcination conditions. These properties played an important role in determining the photocatalytic activity of the materials, which was assessed by monitoring the photodegradation of a methylene blue solution under ultraviolet light. The maximum activity was achieved with the materials that were calcined at 650 °C for 2-8 h with a bead diameter around 700 nm. High activity was attributed to the balance of high crystallinty of the anatase phase, high porosity and large surface area. The size of the beads made separation easy for the reuse of the material after reaction. The synthesis-properties-photocatalytic activity relationships of these monodisperse mesoporous TiO2 beads have been established.