Synthesis and Characterization of TiO 2 Nanoparticles Saira Riaz 1) , Aseya Akbar 2) , Muhammad Imran 3) , and Shahzad Naseem 4) 1), 2), 3), 4) Centre of Excellence in Solid State Physics, University of the Punjab, Lahore, Pakistan 1) saira_cssp@yahoo.com ABSTRACT The ever increasing interest in Titanium Oxide (TiO 2 , Titania) is motivated by its applications in solar cells, biomaterials, photo catalytic activities. Nanocrystalline titania is preferred in these applications due to chemical stability, mechanical hardness, high refractive index, excellent transmission in visible region. Titania exists in three different crystallographic phases i.e. anatase, rutile and brookite. Anatase and rutile crystallizes in tetragonal phase where as brookite has orthorhombic phase. Titania nanoparticles were synthesized via sol-gel method using TiCl 4 precursor. In sol-gel method ammonia was used as the gelation agent. The titania nanoparticles were then centrifuged. In order to study the effect of pH on titania nanoparticles different nanoparticles were prepared by varying the pH of the sol. As-synthesized samples were also annealed at different temperature (upto 500°C). XRD results show the formation of highly crystalline titania nanoparticles. It was found that below 400°C anatase phase dominates while annealing at high temperature results in conversion of anatase to rutile phase. With increase in annealing temperature the peak intensities corresponding to rutile phase increases. Variation in sizes of nanoparticles from 20 nm to 500 nm is observed with variation in annealing temperature and pH. Titania nanoparticles prepared in this research work were homogenous and good interconnection was formed between the particles indicating the good mechanical strength of sol-gel prepared nanoparticles. 1. INTRODUCTION During the past few years, Titania (TiO 2 ) nanoparticles has attracted worldwide attraction because of its high refractive index, high dielectric constant, excellent photocatalytic abilities, high photoelectric conversion efficiency. In addition titania is low cost, environment friendly and has chemical stability (Huang 2013, Shiba 2013, Arunmetha 2013). These advantages of titania especially high refractive index and low absorbing capability have lead to its applications in solar cells and other optoelectronic devices (Ahn 2003). Titania exist in three crystallographic phases namely anatase, rutile and brookite. Anatase (c/a >1) and rutile (c/a <1) has tetragonal structure where as brookite crystallizes in orthorhombic structure. Among these phases rutile is the thermally stable phase where as anatase and brookite both are metastable phases (Sarma 2013). It is 1) , 4) Professor 2), 3) Graduate Student 353