On the study of phase and dimensionally controlled titania nanostructures synthesis at sub-zero temperatures

Highlights: • Nanotitania with controlled morphology and phases synthesized at sub-zero temperatures (− 40 to − 10 °C). • At > − 20 °C, high lattice strain at grain boundaries forms the rutile dominating rod-shaped nanostructures. • Oval-shaped structures formed at − 40 and − 30 °C with major anatase when nucleation rate is higher than the growth rate. The present studies are about surfactant free simple synthesis for titania (TiO₂) nanostructures, by which morphology and phase can be tuned through temperature variation. The formation of oval shaped nanocrystals and nanorods at different temperatures are attributed to the phase transformation between anatase and rutile by one-step chemical reaction involving titanium tetraisopropoxide and aqueous ethyl alcohol. Categorically, two different morphologies of TiO₂ were observed with respect to variation in temperature with nanorods formation at − 20 °C and − 10 °C and oval shape formation at − 40 °C and − 30 °C with higher surface area. Crystalline nature and size of nano-TiO₂ were determined by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The energy gap of TiO₂ nanoparticles were determined by optical absorption measurement and found to be in the range of ~ 2.92 to 3.02 eV with an indirect band nature.