Abstract: Silver nanoparticles (Ag NPs) have been widely applied in various antibacterial fields. However, their preparation generally requires additional reducing agent and suffers from complicated procedures, high production costs, and severe aggregation. In this study, carbon dots (CDs) with intrinsic reducing capability were employed to achieve the in-situ reduction of AgNO₃ and subsequent anchoring of Ag species onto the surface of CDs through a facile one-step water bath method. As a result, silver-loaded CDs (Ag-CDs) with excellent dispersibility, uniform particle size (<10 nm), and negatively-charged surface were successfully synthesized. This negatively charged feature is beneficial for alleviating potential toxicity toward normal cells, suggesting high biosafety. The Ag content in Ag-CDs was calculated to be 9.2% (in mass), mainly existing as Ag⁰ and Ag₂O. The sustained Ag⁺ release was found in aqueous solution which endows Ag-CDs with long-term antibacterial activity. Moreover, the obtained Ag-CDs exhibited excellent photothermal performance in the second near-infrared (NIR-II) window with a photothermal conversion efficiency of 32.43%. Further antibacterial investigations demonstrated that Ag-CDs possessed remarkable antibacterial and biofilm eradication capabilities against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Upon near-infrared irradiation with 980 nm laser, the CDs mediated photothermal effect in synergy with Ag⁺ release, further enhanced antibacterial and antibiofilm performances. This study provides a valuable insight into the design of low-cost, multifunctional, and highly efficient antibacterial materials, showing a promising potential for their applications in infected wound healing, antibacterial medical dressings, and other biomedical antibacterial applications.

Key words: carbon dot, silver nanoparticle, photothermal effect, antibacterial