Carbon quantum dots embedded trimetallic oxide: Characterization and photocatalytic degradation of Ofloxacin

The presence of highly toxic pharmaceutical effluents in the water system has emerged the need for the examination of various methods that could be used for their removal. Considering this, in the present study, we have designed a highly visible- light active trimetallic oxide nanocomposite, CQDs@CoO/La₂O₃/NiO TONCs using facile microwave reduction technique. Its photocatalytic efficiency was tested for the degradation of highly noxious ofloxacin (OFL) antibiotic from the aqueous solution. Maximum degradation rate of 93.8% was obtained within 75 min with 20 mg of photocatalyst dose and 20 mg/L of initial OFL concentration. The addition of CQDs to the trimetallic oxide nanoparticles helped in enhancing the light- harvesting ability of the composite and shifting it to the visible- region. Major reactive radical species involved in the OFL degradation were found to be •OH and •O₂⁻ radicals. In addition, a probable degradation mechanism was also established based the scavenging and band gap studies. The charge transfer study indicated the formation of dual Z- scheme between the 3 constituting units that helped immensely in reducing the charge recombination rate and improving the charge transfer rate.