CuS nanoparticles anchored to g-C₃N₄ nanosheets for photothermal ablation of bacteria

Antibiotic resistance has already been recognized as one of the greatest threats to human beings' health, and thus it is highly desirable to develop new bactericidal approaches. The photothermal antibacterial process based on the photo-to-thermal conversion using semiconducting materials is currently extensively studied owing to its high efficiency, long durability and environmental benignity. In this study, we fabricated copper sulfide (CuS) nanoparticle-decorated graphitic carbon nitride (g-C₃N₄) nanosheets, denoted as the PEG-CuS@g-C₃N₄ nanocomposite, via a simple hydrothermal process. Materials characterization showed that CuS nanoparticles were uniformly distributed on the surface of g-C₃N₄ without agglomeration. Moreover, the nanocomposite exhibited excellent photothermal conversion efficiency (up to 59.64%) due to its strong near-infrared (NIR) absorption characteristics. The antibacterial efficiency evaluation indicated that the PEG-CuS@g-C₃N₄ nanocomposite could effectively kill the Gram-positive Staphylococcus aureus (S. aureus) and the Gram-negative Escherichia coli (E. coli). We found that up to 99% of both S. aureus and E. coli could be killed in a 200 μg ml^-1 PEG-CuS@g-C₃N₄ suspension within 20 min of NIR irradiation. Moreover, the cytotoxicity of the PEG-CuS@g-C₃N₄ nanocomposite was evaluated using the mouse skin fibroblast NIH-3T3 cells, and the nanocomposite was found to display acceptable biocompatibility. We believe that the PEG-CuS@g-C₃N₄ nanocomposite is of significant interest for rapid bacteria-killing, and would gain promising applications for sterilization.