Electrochemical Study of DPPH Radical Scavenging for Evaluating the Antioxidant Capacity of Carbon Nanodots

Carbon nanodots (CNDs) have become one of the potential candidates for antioxidants due to their excellent luminescence, biocompatibility, and lower cytotoxicity. While CNDs have experienced some research on radical scavenging activity via UV–vis spectroscopy, the relationship between reserved 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) concentration and CNDs’ incubation concentration remains unclear. This work describes an electrochemical study on the changes of redox peaks of the oxidation of DPPH• at gold electrodes with addition of different concentrations of a type of microwave-synthesized CND (U-dots). The result is consistent with a UV–vis absorption dose-dependent study used to quantify the antioxidation activities. Combined with standard heterogeneous electron-transfer rate constant analysis, electrochemical study gives a coupled hydrogen atom transfer (HAT) mechanism for DPPH• scavenging by the U-dots. This work provides a new perspective on the antioxidative study of the U-dots, which may aid their development for practical use in biomedicine.