Synthesis and Control of Physical Properties of Titania Nanoparticles as a Function of Synthetic Parameters

TiO₂ nanoparticles were prepared by a two step acid-base catalyzed sol–gel method. The effects of key synthetic parameters, including water/alkoxide ratio, pH, reaction time, and calcination temperature on the physical properties of the final product were investigated. The current study revealed that the desired properties can be inherited in to TiO₂ by controlling the key parameters to the optimized values. It was found that the grain size decreased with an increase in water/alkoxide ratio and reaction time, increased with calcination temperature while remained unaffected by variation in pH. The longer reaction time not only increases surface area but also anatase phase formation can be accomplished even under high pH. Band-gap was also found to reduce with reaction time >48 h. Change of pH during synthesis to high value resulted into mesoporous TiO₂ with anatase as a sole phase. The TiO₂ nanoparticles were also doped by first row transition metals in order to investigate their effects on the photophysical properties. The photoluminescence characteristic of the TiO₂ was altered differently by different doping metals. Doping with first row transition metals reduces the band-gap of TiO₂ in the following order: Cr > Mn > Fe ∼ V > Co ∼ Ni > Cu ∼ Zn.