Effects of montmorillonite on phase transition and size of TiO2 nanoparticles in TiO2/montmorillonite nanocomposites

Abstract Nanostructured TiO 2 /montmorillonite (TiO 2 /Mt) materials have many applications in a variety of fields such as plastic degradation, photocatalysis, antibacterial agent development and water purification. In order to homogeneously disperse TiO 2 nanoparticles within the interlayer space of montmorillonite, an in-situ interlayer reaction method was developed to prepare nanostructured TiO 2 /Mt materials. Briefly, cetyl trimethylammonium (CTA + ) was first intercalated into the interlayer of the montmorillonite structure. Then tetrabutyl orthotitanate (TBOT) was introduced into the interlayer space of the CTA + /montmorillonite (CTA + /Mt) nanocomposites by solvation. TBOT in the nanocomposites underwent in-situ hydrolysis, de-hydroxylation and annealed at different temperatures. During annealing, CTA + was burnt off and TiO 2 formed in the interlayer space of montmorillonite. The average crystal size of TiO 2 in TiO 2 /Mt was compared with that of both the pure TiO 2 nanoparticles and the mixture of pure TiO 2 and montmorillonite. The intermediate and final products were characterized by X-ray diffraction, FT-Raman spectroscopy and transmission electron microscopy. The results showed that the phase-change temperature for transformation of TiO 2 nanoparticles in TiO 2 /Mt nanocomposites from anatase to rutile phase was higher than that for pure TiO 2 nanoparticles and the mixture of pure TiO 2 and montmorillonite. Pure TiO 2 nanoparticles were all converted to rutile when the annealing temperature was increased to over 800 °C. However, the anatase-TiO 2 still existed in TiO 2 /Mt, even though the annealing temperature reached a much higher temperature of 1200 °C. In addition, at the same annealing temperature, the average crystal size of TiO 2 in TiO 2 /Mt nanocomposites was smaller than that of either the pure TiO 2 or the mixture of pure TiO 2 and montmorillonite.