To elucidate the mechanism of hydrogen peroxide generation by the synthesized SPs, EPR spectroscopy was performed to detect radicals formed during the reaction. The EPR spectroscopy results revealed clear spectral differences when comparing UV light illumination alone with simultaneous illumination of both UV and visible light. Although this provides evidence of a synergistic effect from the simultaneous illumination, it does not yield detailed mechanistic insights into radical formation. To that end, radical trapping experiments were performed, using probe molecules: 2,3-bis-(2-methoxy-4-nitro-5-sulphenyl)-(2H)-tetrazolium-5-carboxanilide (XTT) and terephthalic acid, which acted as electron and hydroxyl radical scavengers, respectively. These probes provided clearer evidence of the electron-mediated oxygen reduction reaction, leading to increased H2O2 production. The detailed analysis of the radical trapping experiments using both techniques is discussed below.