A Unique Disintegration–Reassembly Route to Mesoporous Titania Nanocrystalline Hollow Spheres with Enhanced Photocatalytic Activity

A novel disintegration–reassembly route is reported for the synthesis of mesoporous TiO₂ nanocrystalline hollow spheres with controlled crystallinity and enhanced photocatalytic activity. In this unique synthesis strategy, it is demonstrated that sol–gel-derived mesoporous TiO₂ colloidal spheres can be disintegrated into discrete small nanoparticles that are uniformly embedded in the polymer (polystyrene, PS) matrix by surface-induced photocatalytic polymerization. Subsequent reassembly of these TiO₂ nanoparticles can be induced by an annealing process after further coating of a resorcinol–formaldehyde (RF) resin, which forms self-supported hollow spheres of TiO₂ at the PS/RF interface. The abundant phenolic groups on the RF resin serve as anchoring sites for the TiO₂ nanoparticles, thus enable the reassembly of the TiO₂ nanoparticles and prevent their sintering during the thermal crystallization process. This unique disintegration–reassembly process leads to the formation of self-supported TiO₂ hollow spheres with relatively large surface area, high crystallinity, and superior photocatalytic activity in dye degradation under UV light irradiation.