Enhanced reactive oxidation species generation by ligand-to-metal-charge transfer between oxygen vacancy-rich ZnO mesocrystal with ciprofloxacin pollutants

Through visible light driven ligand-to-metal charge transfer (LMCT) with organic pollutant-semiconductor is a new method to promote reactive oxygen species (ROS) generation in water treatment. This study is the first time to use ciprofloxacin (CIP) pollutants induced LMCT on ZnO mesocrystal with rich oxygen vacancies (M-ZnO-OV) to improve ROS generation for CIP self-degradation. The results show an obviously increased intensity of HO• and O2•− through the LMCT process, leading to the optimal kinetic rate constant of 0.043 min–1 for CIP degradation, which is 7.5 times that of ZnO non-LMCT process. The presence of oxygen vacancies (OVs) in M-ZnO-OV leads to an electron-deficient Zn atom nearby OVs, promoting the formation of LMCT complex, and then resulting in rapid electron transfer from OVs to oxygen in water to generate ROS. The present investigation provides a new OVs-enhanced LMCT process to improve the concentration of ROS for water treatments.