Abstract: Narrow bandgap semiconductor MgIn₂S₄ has been readily grown onto In₂O₃ nanofibers by an in situ growing method. The so-formed MgIn₂S₄-In₂O₃ hybrid nanofibers are characterized by strong visible light absorption and intimate MgIn₂S₄/In₂O₃ heterointerfaces. Under visible light illumination (λ ≥ 400 nm), the hybrid nanofibers demonstrate an exceptionally high photocatalytic activity for Escherichia coli (E. coli) disinfection, outcompeting pristine MgIn₂S₄, naked In₂O₃ nanofibers, and many other photocatalytic systems reported. Specifically, the hybrid nanofibers achieve a 7 log reduction in viable cells for merely 20 min illumination while pristine MgIn₂S₄ and naked In₂O₃ nanofibers alone are almost inactive. Further analysis indicates that the hybrid nanofibers essentially form a type-II semiconductor heterojunctions which enable spatial separation of photocarriers. Owing to the intimate heterointerfaces, photocarriers can be promptly separated and accumulated respectively in In₂O₃ and MgIn₂S₄ thereby allowing continuous generation of copious reactive species for disinfection. This work signifies the usefulness of heterointerfaces in promoting photocarrier separation and provides a useful strategy to upgrade photocatalytic performance from otherwise almost inactive semiconductors.

Key words: Photocatalyst, Disinfection, Semiconductor fiber, Heterostructure, Antibacterial activity