Tuning the unsaturated iron sites in MIL-101(Fe) nanoparticles for reactive oxygen species-mediated bacterial inactivation in the dark

In this study, reactive oxygen species (ROS)-mediated antibacterial activity with high efficiency in the dark was achieved by modulating the active sites of MIL-101(Fe) nanoparticles. The ROS production over x-MIL-101(Fe) nanoparticles was intensively enhanced by tuning the unsaturated iron sites (Fe^II/Fe^III, the ratio was marked as x%). Electron paramagnetic resonance (EPR) analysis confirmedmore ROS generation on x-MIL-101(Fe) surface than that on MIL-101(Fe), due to more electrons shifting from benzene rings to Fe^II/Fe^III sites. Among all samples, 8.9-MIL-101(Fe) displayed the highest inactivation efficiency (> 99.99%) against Escherichia coli within 2 h in the dark. ROS reacted with cell wall components to generate carbon-centered radicals via H abstraction, leading to the disruption of cell wall, intracellular ROS, and DNA damage. Antibacterial performance of 8.9-MIL-101(Fe) in air filters indicated 8.9-MIL-101(Fe) can be applied to prevent the spread of airborne pathogens. The results are promising for the ambient antibacterial application of MOF materials.