Figure 2. SEM images of a) mesoporous pure TiO2 films (sample A) calcined
at (a-1) 450 8C, (a-2) 5508C, and (a-3) 6508C; and b) mesoporous TiO2/SiO2
hybrid films prepared with the molar ratio of PVP/TTIP/TEOS 1.0:4.0:1.0
(sample B) calcined at (b-1) 450 8C, (b-2) 550 8C, and (b-3) 650 8C.