Prussian blue-encapsulated Fe3O4 nanoparticles for reusable photothermal sterilization of water.

Waterborne health issues continue to grow despite the large number of available solutions. Current sterilization techniques to fight with waterborne diseases struggle to meet the demands on cost, efficiency and reach. Effective alternatives are pressingly required. Here we introduce Prussian blue coated ferroferric oxide (Fe3O4@PB) composites for water sterilization. The composites exhibit superior photothermal inactivation of bacteria under solar-light irradiation, with nearly complete inactivation of bacterial cells in only 15 min. Even for the mixed bacteria in authentic water matrices, the composites show excellent bacterial inactivation performance. Moreover, the highly magnetized iron core of the Fe3O4@PB enables magnetic separation and recycling. Multiple cycle runs reveal that Fe3O4@PB composites have exceptional stability and reusability. This work demonstrates a scalable, low-cost, high-efficiency and reusable sterilization method to improve water quality and safety.