Generation of reactive oxygen species by promoting the Cu(II)/Cu(I) redox cycle with reducing agents in aerobic aqueous solution.

This study investigated the generation of reactive oxygen species (ROS) (O-2(-)center dot, H2O2,and HO center dot) by promoting the Cu(II)/Cu(I) redox cycle with certain reducing agents (RAs) in aerobic aqueous solution, and benzoic acid (BA) was employed as indicator for the hydroxyl radical (HO center dot). Hydroxylamine (HA) can reduce Cu(II) to Cu(I) to induce chain reactions of copper species resulting in the generation of the superoxide radical (O-2(-)center dot) and hydrogen peroxide (H2O2), and the intermediate Cu(I) can further activate H2O2 via a Fenton-like reaction to produce HO center dot, creating the remarkable BA degradation. O-2 is indispensable, and unprotonated HA is the motive power in the O-2/Cu/HA system. Moreover, pH is a crucial factor of the O-2/Cu/HA system due to the protonated HA not being able to reduce Cu(II) into Cu(I). The oxidation of HA can be effectively induced by trace amounts of Cu(II), and both a higher HA dosage and a higher Cu(II) dosage can enhance H2O2 generation and BA degradation. In addition, some other RAs that can reduce Cu(II) into Cu(I) could replace HA in the O-2/Cu/HA system to induce the generation of these ROS in aerobic aqueous solution.