Pd nanoparticle-modified TiO2-x composites as efficient visible-light active photocatalysts for tetracycline degradation and microbial disinfection

In the present work, Ti3+-self-doped TiO2 heterostructure photocatalysts were prepared by coupling with different additions of palladium quantum dots by means of deposition-reduction methodology. The electron paramagnetic resonance (EPR) analysis indicated the existence of Ti3+ in synthesized samples. The transmission electron microscopy (TEM) images presented the modification of TiO2-x nanoparticles by coupling with nano palladium. Photoluminescence (PL) results demonstrated the lowest charge carrier recombination rate in 5% Pd/ TiO2-x composites. Photocatalytic performances of photocatalysts were evaluated by degrading Tetracycline (TC) and inactivating Escherichia coli (E. coli) and Fusarium oxysporum f. sp. Vasinfectum (Fov) with the presence of visible light, in which an enhanced photocatalytic degradation and inactivation activity was found in all Pd coupled composites with the highest efficiency in 5% Pd/TiO2-x. The improved photocatalytic activity of Pd/ TiO2-x was associated to the generation of more hydroxyl radicals (center dot OH) and superoxide anions radicals (center dot O2-) during photocatalytic process which were demonstrated by the electron spin-resonance spectroscopy (ESR) technique. Moreover, 5% Pd/TiO2-x composites were found to remain high photocatalytic properties in a circulating photo-disinfection system.