Room temperature synthesis of mesoporous aggregates of anatase TiO₂ nanoparticles

The controlled hydrolysis reaction of titanium tetrabutoxide in presence of acetic acid in isopropanol, i.e. in non-aqueous media was adopted in the present work for the synthesis of nanocrystalline titania followed by aging at ambient conditions for longer duration. The powder XRD shows that the as-dried precursor (without any aging) is non-crystalline in nature. However, room temperature aging for longer duration >120 days not only helped to develop crystallinity in TiO₂ nanoparticles but also led to the formation of their self-assembly towards mesoporous aggregates creating sponge like TiO₂ nano-structure having high surface area ∼250 m² g^-1 and narrow pore size distribution of 4-5 nm. TEM observations revealed the generation of spherical TiO₂ nanoparticles (4-5 nm) assembled to form stable spongy scaffold having porous network structure with pore size 5-6 nm. Also, presence of a pronounced hysteresis loop in BET isotherm is indicative of a 3D-intersection network of the pores of size 4-5 nm. Further heat-treatment to the aged precursor at 400 °C/2 h in air modify pore network structure due to sintering of TiO₂ particles as is observed in TEM studies and lowering thereby the surface area to 125 m² g^-1.