In this work optical properties of titanium dioxide nanoparticles were studied.Titanium dioxide nanoparticles were synthesized by the sol-gel method followed by a hydrothermal treatment using tetraisopropyl orthotitanate (TIOT) and 2-propanol.The synthesized samples were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (UV/DRS) and nitrogen adsorption-desorption methods.The bandgap energy was obtained using the Kubelka-Munk reemission function.The catalyst synthesized with a molar ratio of R 1 (water/TIOT) = 3.5 and R 2 (2-propanol/TIOT) = 15 has a predominately anatase phase.It also has a high photo degradation of methyl orange compared to TiO 2 Degussa P-25.A shift band gap energy of 3.27 was observed.