<scp> Fe ₃ O ₄ </scp> @Polydopamine/Polylactic Acid Composite Fibers With Improved Sterilization and Air Filtration Efficiency by Surface Coating Enhanced Photothermal Stability of <scp> Fe ₃ O ₄ </scp>

ABSTRACT Air pollution and bacterial infection have become global problems, especially in the field of medical and health care. With the ever‐developing nanomaterials and photothermal sterilization technology, electrospinning photothermal nanofibers provide an effective way to solve the problem of air pollution and bacterial infection. Iron oxide (Fe 3 O 4 ) nanoparticles have been used as independent photothermal materials due to their excellent photothermal properties, and biodegradability. However, due to the nano‐effect, the surface is more easily oxidized to gamma iron (III) oxide (γ‐Fe 2 O 3 ), which in turn affects its photothermal properties. To address this, we coated Fe 3 O 4 with polydopamine (PDA) and incorporated it into polylactic acid (PLA) nanofibers via electrospinning, fabricating Fe 3 O 4 /PLA and Fe 3 O 4 @PDA/PLA composites. We found that Fe 3 O 4 @PDA/PLA fibers showed a more excellent photothermal effect. The highest temperature of 3%‐Fe 3 O 4 @PDA/PLA fibers was 74.7°C, which was 12.1°C higher than that of 3%‐Fe 3 O 4 /PLA fibers. More importantly, due to the effect of the PDA protective layer, the photothermal stability of the fibers was effectively enhanced. After 90 days of storage, the maximum temperature change Δ T of 3%‐Fe 3 O 4 @PDA/PLA fibers was reduced to 4.5°C (Δ T of 3%‐Fe 3 O 4 /PLA was 8.7°C). The photothermal sterilization rate of gram‐negative Escherichia coli ( E. coli ) and gram‐positive Staphylococcus aureus ( S. aureus ) reached 99.0% and 97.8%, respectively. Furthermore, the Fe 3 O 4 @PDA/PLA photothermal fibers had high filtration efficiency (99.58%) and low pressure drop (42.3 Pa).