Green Synthesis of TiO 2 Nanoparticles in a Deep Eutectic Solvent for High‐Performance Photocatalysis: The Role of the Cosolvent

Abstract Herein, we report a unique surfactant‐free synthetic pathway for the synthesis of anatase TiO 2 catalysts in the size range of 13 to 20 nm by solvothermal method using choline chloride‐urea deep eutectic solvent (DES) as green media and 2‐propanol as cosolvent. The composition of reline was tuned by adding 0 (pure reline), 5, 10, 20 and 50 wt % of 2‐propanol. The amount of cosolvent was found to have a significant influence on TiO 2 particle size, N 2 isotherms and the magnitude of Urbach energy formed within the band gap of mesoporous TiO 2 nanostructures. The sample obtained with 10 wt % of propanol showed the best photocatalytic activity in the degradation of Rhodamine B (RhB), which is attributed to the combined effect of Urbach tail states, specific surface area, particle size and band gap energy of TiO 2 NPs. Radical trapping experiments with scavengers revealed that OH⋅ radicals are primarily responsible for RhB decomposition.