Magnetically separable MXene@Fe₃O₄/Au/PDA nanosheets with photothermal-magnetolytic coupling antibacterial performance

Harmful bacteria are common substances in water that endanger human health, so it is urgent to establish a simple system that can tackle these hazardous substances simultaneously. In this work, a novel magnetic MXene@Fe₃O₄/Au/polydopamine (PDA) nanosheet with excellent photothermal-magnetolytic coupling antibacterial performance is developed. MXene, Au and polydopamine all have good photothermal properties, so the photothermal conversion efficiency of the MXene@Fe₃O₄/Au/PDA nanosheet reaches as high as 48.7%. After 6 min of 808 nm laser irradiation, the MXene@Fe₃O₄/Au/PDA nanosheets (120 μg·mL⁻¹) can achieve nearly 100% antibacterial effect against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In comparison to the sole photothermal treatment, the nanosheet at lower concentration (80 μg·mL⁻¹) also exhibit stronger antibacterial properties against both Gram-negative and Gram-positive bacteria during the photothermal-magnetic coupling treatment. The result is mainly because the heat generated by the photothermal effect of the nanosheet is directly transferred to the cell membrane, and the edge of the nanosheet cuts the cytomembrane similar to a magnetic “hot nanoblade”, resulting in subsequent shrinkage, deformation and even rupture.