In Fig. , FTIR spectroscopy provides information on the formation of Si-O-Ti bonds at ~960 cm -1 band . This band becomes stronger with increased Ti loadings, indicating more substitution of Si 4+ ions by tetrahedral Ti 4+ ions in the matrix of Ti-SiO2 materials. The pristine SiO2 (without Ti) exhibits only the main bands at ~1080 and 800 cm -1 ascribed to the asymmetric and symmetric Si-O-Si vibration, respectively, and a weak band at ~975 cm -1 related to the symmetric stretching of silanol Si-O-H groups .