In this study, composite nanoparticles of TiO2–CuO(TC)were synthesizedusing the sol–gel method. Tetra butylorthotitanate and copper (II) nitrate trihydrate were used as precursors to titanium dioxide and copper oxide, respectively. Ethanolwas used as a solvent.Dynamic light scattering, X-ray diffraction, UV–Vis spectroscopy, nitrogen adsorption–desorption isotherm, field emission scanning electron microscopy and transmission electron microscopy were used to characterize the nanoparticles. The synthesized photocatalytic nanoparticles were used to degrade methylene blue dye solution as a model of organic pollutant under UV and visible light irradiation. The TC sample calcined at 550 ◦C has the highest photocatalytic percentage under visible light (33.14 %) and the best photocatalytic activity at 650 ◦C under ultraviolet light (40 %). The pure TiO2 sample has an adsorption edge of 365 nm with a band gap energy of 3.39 eV and the mesoporous TiO2–CuO sample with an absorption edge wavelength of 375 nm has a band gap energy of 3.30 eV at 350 ◦C. According to the X-ray photoelectron spectroscopy study, Ti was predominantly chemically present as Ti 4+. Cu was found to be a cation with a capacity of two (Cu 2+).
