A new layered nanocomposite, which is one-to-one interstratified with a montmorillonite layer and a mixed SiO 2 /TiO 2 sol particle one, has been prepared by ion exchange reaction of the Na + ion in montmorillonite with the positively charged SiO 2 /TiO 2 sol particles. The ion exchange reaction was performed at three different temperatures of 45, 60, and 75°C by mixing an aqueous suspension of 1 wt % Na + montmorillonite with SiO 2 /TiO 2 sol solution where the molar ratio of Si/Ti was selected as 20/2. According to the powder X-ray diffraction analysis, the basal spacings of layered nanocomposites calcined at 400°C were found to increase from 35.4 Å, to 47.3 Å, and to 60.0 Å as the ion exchange reaction temperature was raised from 40°C, to 60°C, and to 75°C. Their BET and Langmuir specific surface areas and porosities, estimated from nitrogen adsorption-desorption isotherms, become larger with the increment of basal spacing, and the highest BET specific surface area and the largest porosity are found to be 683 m 2 /g and 0.50 mL/g, respectively. Despite the large increment of the basal spacing, the porous properties such as specific surface areas, porosities, and pore sizes, those which are calculated from t-plots and chemical shift of 129 Xe NMR, respectively, are determined to be almost constant. From the UV/vis spectra, the blue shift of the absorption edge was observed, indicating that the TiO 2 sol particles in the interlayer are quantum sized. It is therefore proposed that the products are intercalation-type nanocomposites with the multistacked structure of the SiO 2 /TiO 2 nanoparticles in the interlayer space of montmorillonite.

The structural characterisation of SiO 2 /ZrO 2 nano-sol particles, prepared by mixing SiO 2 sol and aqueous solution of ZrOCl 2 8H 2 O, has been carried out by in-situ XAS measurement at the Zr K-edge during condensation reaction. The detailed XANES features at the Zr K-edge of the mixed sol of SiO 2 /ZrO 2 are compared with those of other references such as ZrO 2 , ZrOCl 2 8H 2 O, BaZrO 3 , and ZrSiO 4 , and it becomes obvious that the Zr 4+ ions are stabilised in an octahedral symmetry. The EXAFS result also indicates that each Zr atom is coordinated with six oxygen ones as the first nearest neighbour, where two oxygen atoms are from the linkage of (Si-O-Zr) at short distance, and four ones are from water molecules at long distance. As the condensation reaction proceeds, it is found that the number of oxygen atoms due to the formation of (Si-O-Zr) bond at short distance and the second neighbour of silicon atoms increase simultaneously. From the above EXAFS and XANES results, the structural and gelating models could be proposed, which is based on the octahedrally coordinated but distorted zirconium species attaching on the SiO 2 sol surface.

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