However, at an elevated temperature of 600 1C, the calculated crystal size of UH-600 increases dramatically to 27.5 nm. The heat treatment induced crystallization and growth of grains have remarkable effects on the textural properties of mesoporous TiO2, which is proved by the low-angle XRD patterns as shown in the inset of Fig. 1. The broad peaks at 2y=2.21 in curve a and 2y=2.41 in curve b indicate the mesoporous structures of UH-350 and UH-450, respectively.