“Self‐Capped” Carbon Dots with Excellent Anti‐Bacteria Effect and an Extremely Low Cytotoxicity Applied for Hand Sanitizer

Abstract 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 −1 effectively, disrupting bacterial cell membranes. The incorporation of zinc cations (Zn 2+ ) doping further enhances the antibacterial potential of MC‐CDs, enabling substantial efficacy even in the absence of light due to improved electrostatic interactions with bacterial membranes. In comparison to commercial agents such as salicylic acid, p ‐chloro‐ m ‐xylenol, and triclosan, Zn@MC‐CDs exhibit superior antibacterial performance. When formulated into a hand sanitizer, Zn@MC‐CDs maintained over 90% efficacy, displaying excellent stability and extremely low cytotoxicity, highlighting their potential for safe and effective use in personal hygiene products. This study introduces self‐capped carbon dot as a promising antibacterial agent, addressing a critical need for advanced and reliable solutions in infection control.