Synthesis, characterisation, and effect of pH on degradation of dyes of copper-doped TiO2

Copper-doped TiO2 nanoparticles were synthesised using an ultrasonic-assisted sol–gel method with various doping concentrations from 0 to 2.5 at.%. The samples were characterised by X-ray diffraction, UV–vis diffuse reflectance spectroscopy (UV–vis), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area determination, and zeta potential. The presence of copper in TiO2 crystal structure was revealed by UV–vis spectra, and the TEM analysis showed that particles are mainly spherical around the size range of 15–20 nm. In addition, doping copper into TiO2 lattice caused a decrease in the surface area due to the aggregation of nanoparticles and a shift of isoelectric point towards lower pH when the dopant concentration increased. The photocatalytic reactivity of these materials was evaluated by the degradation of methylene blue and methyl orange under the UV light. The effect of the initial solution pH on the adsorption capacity and the photocatalytic behaviour of the Cu-doped TiO2 in the decolourisation of these dyes were also studied.