The isocyanate groups (–NCO) derived from –NC– bonds in the organic ligands enables the thermally treated ZIF-8 to act as wide-spectrum photocatalyst.
A novel and efficient 3D biohybrid photocatalyst, defective
MoS2 nanosheets encapsulated carbonized rape pollen, was
fabricated
and applied to water disinfection. The rape pollen-MoS2 (PM) biohybrid showed excellent dispersibility, high stability,
and efficient charge-carrier separation and migration ability, resulting
in the highly enhanced photocatalytic inactivation performance toward
various waterborne bacteria under different light sources. The inactivation
mechanisms were systematically investigated. Reactive species (RSs),
including electrons, holes, and reactive oxygen species (•O2
– and •OH), played major roles in
inactivating bacteria. The antioxidant system of bacteria exhibited
a self-protection capacity by eliminating the photogenerated RSs from
PM biohybrid at the early stage of inactivation. With the accumulation
of RSs, the cell membrane and membrane-associated functions were destroyed,
as suggested by the collapse of cell envelope and subsequent loss
of cell respiration and ATP synthesis capacity. The microscopic images
further confirmed the destruction of the bacterial membrane. After
losing the membrane barrier, the oxidation of cytoplasmic proteins
and lipids caused by invaded RSs occurred readily. Finally, the leakage
of DNA and RNA announced the irreversible death of bacteria. These
results indicated that the bacterial inactivation began with the membrane
rupture, followed by the oxidation and leakage of intracellular substances.
This work not only provided a new insight into the combination of
semiconductors with earth-abundant biomaterials for fabricating high-performance
photocatalysts, but also revealed the underlying mechanisms of photocatalytic
bacterial inactivation in depth.
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