The increasing challenge of antibiotic resistance necessitates the development of novel antibacterial strategies. In this study, a novel kind of self-capped carbon dots is synthesized from methylene blue (MB) and cetyltrimethylammonium chloride (CTAC), and named as MC-CDs that are specifically designed for enhanced photodynamic antibacterial activity. Under 660 nm laser irradiation, MC-CDs demonstrate high inactivation rates of Escherichia coli (96.83%) and Staphylococcus aureus (94.44%) at 14 and 18 µg mL