Fabrication of nitrogen and sulfur co-doped carbon dots for antioxidant applications
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Abstract
Carbon dots (CDs) have attracted attention because of their unique optical properties, biocompatibility, and ease of synthesis. Recently, CDs have demonstrated significant antioxidant activity due to their high surface functionalization, which enables them to effectively interact with reactive oxygen species (ROS) and free radicals. In this study, we aimed to synthesize nitrogen and sulfur co-doped carbon dots (NS-CDs) using a microwave-assisted pyrolysis method, incorporating varying concentrations of nitrogen and sulfur. The particle size, polydispersity index (PDI), zeta potential, and antioxidant activity were evaluated. The optimal formulation, 20-NS-CDs, was further assessed for total phenolic content and intracellular ROS. Finally, biocompatibility was evaluated using an MTT assay. The results revealed that the 20-NS-CDs had a particle size of 4.35 ± 1.84 nm and demonstrated the highest antioxidant activity, as indicated by the lowest half-maximal inhibitory concentration (IC₅₀) value of approximately 0.96 ± 0.03 mg/mL. The total phenolic content was 21.1 ± 1.27 mg of gallic acid equivalent per gram (mg GAE/g), consistent with previous studies, and the antioxidant activity was confirmed by a reduction in intracellular fluorescence in a dose-dependent manner. Therefore, the ability of 20-NS-CDs to scavenge free radicals holds significant potential for applications in health and environmental sciences.
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