Fabrication of oxygen vacancy-rich BiO2− x/multi-walled carbon nanotubes with enhanced photothermal catalytic antibacterial performance†

Photothermal catalytic sterilization technology is a promising approach due to its high efficiency, environmental friendliness, and stability. Herein, the composites of oxygen vacancy-rich BiO_{2− x} and multi-walled carbon nanotubes (BiO_{2− x}/CNTs) were prepared, and their photothermal bactericidal ability under near-infrared (NIR) light was investigated. The experimental results showed that the photothermal response of BiO_{2− x} was significantly improved after CNT combination. And the surface of the catalyst reached nearly 60 °C in a short time under NIR light irradiation. The photothermal catalytic activity of BiO_{2− x}/CNTs was tested with Escherichia coli as the target pathogen. It was observed that BiO_{2− x}/CNTs exhibited excellent sterilization effects, killing 99% of E. coli within three hours, which was attributed to the reactive oxygen species produced by the lattice oxygen release of BiO_{2− x}. The results of radical quenching experiment and electron paramagnetic resonance (EPR) indicated that the main active substance was a superoxide free radical (˙O₂⁻), which caused the complete irreversible death of E. coli K-12 by destroying the cell membrane function. The BiO_{2− x}/CNT catalyst showed excellent photothermal and bactericidal properties under NIR light, which provided a new idea for the application of solar-driven photothermal catalysis in bactericidal processes.