Thermo-responsive polymer–black phosphorus nanocomposites for NIR-triggered bacterial capture and elimination

Water contamination by pathogenic bacteria is a major challenge to human health. The conventional disinfection methods produce disinfection by-products that may be carcinogenic, while the recently-developed nanotechnologies face the difficulties of low efficiency and rate, secondary pollution, and tedious processes. To solve these problems, we designed a thermo-responsive poly(N-isopropylacrylamide)-functionalized black phosphorus (named BP–PNIPAM) to capture and eliminate bacterial cells under the stimuli of near-infrared (NIR) irradiation. PNIPAM is covalently linked to the surface of BP nanosheets by aryl diazonium reaction and in situ atom transfer radical polymerization (ATRP). Under short-time NIR irradiation, bacterial cells are captured and co-precipitated with BP–PNIPAM due to the thermally induced hydrophilic-to-hydrophobic phase transition of PNIPAM. If the irradiation time is prolonged, the wrapped bacteria are disinfected due to hyperthermia. More than 80% of E. coli and S. aureus are captured by 100 μg mL−1 BP–PNIPAM within 5 min-NIR irradiation, while the elimination efficiency towards E. coli, S. aureus, and anti-ampicillin E. coli reaches 100% in the presence of 50 μg mL−1 BP–PNIPAM within 20 min-NIR irradiation. Moreover, BP–PNIPAM exhibits no obvious toxicity to Caco-2 cells up to 100 μg mL−1 within 24 h. Therefore, BP–PNIPAM offers an efficient, biocompatible, and convenient approach for the capture and sterilization of pathogenic bacteria in water.