Fabrication of Photocatalytic Paper Using TiO2 Nanoparticles Confined in Hollow Silica Capsules.

TiO2 nanoparticles (NPs) encapsulated in hollow silica spheres (TiO2@HSSs) show a shielding-effect that can insulate photocatalytically active TiO2 NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO2@HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO2@HSS, which has an ample void space between inner TiO2 NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO2@HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO2@HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO2@HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO2 NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO2 and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.