Controllable preparation of TiO2 nanoparticles using deep eutectic solvents and their photocatalytic degradation of dyeing wastewater

Titanium dioxide nanoparticles (TiO₂ NPs) have garnered considerable attention within the materials science community due to their superior availability, high photocatalytic activity, remarkable thermal stability, and cost-effectiveness. Recently, a growing interest has emerged in their potential applications within scientific research. Therefore, the development of more efficient and controllable preparation methods has been concentrated in current studies. This study uses deep eutectic solvents (DESs) as solvents and structure-directing agents to provide a gentle and environmentally friendly process for the controlled synthesis of TiO₂ NPs. Furthermore, it examines their photocatalytic degradation performance on dye wastewater under full-spectrum light sources. The findings reveal that by introducing TiCl₄-DESs in a mass ratio of 1:10 in a hydrolytic solution of PEG-H₂O with a mass ratio of 1:1, and subsequently, calcining the mixture at 550 ℃ in a muffle furnace, uniform spherical pure anatase–type TiO₂ NPs with good dispersion and an average particle size of approximately 14.01 nm can be obtained. After 60 min of exposure to a full-spectrum light source, the removal rate of methylene blue reached 99.2 %. After 180 min, the degradation rates of rhodamine B and methyl orange were found to be 97.0 % and 80.7 %, respectively. These results demonstrate that the application of DESs facilitates the green and mild modulation of the nanostructures and grain sizes of TiO₂ NPs, effectively enhancing their photocatalytic activity.