A structural study of (TiO2)x(SiO2)1−x (x=0.18, 0.30 and 0.41) xerogels prepared using acetylacetone

A combination of 29 Si and 17 O MAS NMR, EXAFS and FTIR spectroscopy have been used to study the atomic structure of (TiO 2 ) x (SiO 2 ) 1–x (x=0.18, 0.30 and 0.41) xerogels prepared using an acetylacetone stabilised Ti(OPr i ) 4 precursor. In the as-prepared materials, Ti is present in a distorted octahedral coordination with a significant proportion still complexed by acetylacetone. For the first time in such an amorphous solid, a 17 O NMR resonance has been observed at 110 ppm which is attributed to (O 5 )Ti-O-Si groups. Heat treatment of these xerogels tends to convert TiO 6 into TiO 4 where the Ti is substituted into the silica network. Our results are in accord with previous work which suggests that the upper limit for solubility of TiO 2 in SiO 2 is ca. 15 mol%. Clear evidence of some phase separation in the (TiO 2 ) 0.41 (SiO 2 ) 0.59 sample after heat treatment to 750 °C is presented, although the 17 O MAS NMR results show that the use of acetylacetone significantly increases the amount of Ti-O-Si bonding at this composition compared to samples prepared without it.