Controlled crystallization of nanoporous and core/shell structure titania photocatalyst particles

Poly(ethylene oxide) (PEO)-titania (TiO₂) organic-inorganic hybrid particles were synthesized using sol-gel chemistry and crystallized at 600, 800, and 900 °C. Anatase/rutile core/shell-structured titania particles were obtained through partial phase transformation (∼70%) of anatase to rutile at 800 °C. The mechanism of core/shell structure formation was proposed as the shrinkage during anatase-to-rutile phase transformation, the difference in the thermal expansion coefficient (TEC) of two crystals, and further decomposition of remaining organic components trapped in the core. The core/shell particles showed enhanced photodecomposition rates compared to spherical shape particles and other commercially available particles most probably due to the increased surface area by the nanoporous and nanocrystalline structure of the anatase core.