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

A combination of Si-29 and O-17 MAS NMR, EXAFS and FTIR spectroscopy have b een used to study the atomic structure of (TiO2)(x)(SiO2)(1-x) (x = 0.18, 0 .30 and 0.41) xerogels prepared using an acetylacetone stabilised Ti(OPri)( 4) precursor. In the as-prepared materials, Ti is present in a;distorted oc tahedral coordination with a significant proportion still complexed by acet ylacetone. For the first time in such an amorphous solid, a O-17 NMR resona nce has been observed at 110 ppm which is attributed to (O-5)Ti-O Si groups . Heat treatment of these xerogels tends to convert TiO6 into TiO4 where th e Ti is substituted into the silica network. Our results are in accord with previous work which suggests that the upper limit for solubility of TiO2 i n SiO2 is cn. 15 mol%. Clear evidence of some phase separation in the (TiO2 )(0.41)(SiO2)(0.59) sample after heat treatment to 750 degrees C is present ed, although the O-17 MAS NMR results show that the use of acetylacetone si gnificantly increases the amount of Ti-O-Si bonding at this composition com pared to samples prepared without it.