Photocatalysts made of earth-abundant elements using simple fabrication methods are highly desirable for bacterial inactivation in practical applications. This study proved that the carbon-based g-C3N4 could act as an effective antagonist to the ubiquitous plant-pathogen Rhizobium radiobacter with good photostability and reusability under visible light. The applying of g-C3N4 efficiently improved the survivability of tobacco seedlings under the stress of R. radiobacter and showed no adverse effect on tobacco growth compared with the common metal-based TiO2 and CdS photocatalysts. The systematic mechanism studies revealed that the photoinduced reactive species (RSs) were strongly involved in the photocatalytic bacterial inactivation process, with an effectiveness of h+ >radical dotO2− >radical dotOH > H2O2 > e− > 1O2. The direct contact between g-C3N4 and bacterial cells was also essential for the effective bacterial inactivation. Although bacterial self-protection system (SOD and CAT enzymes) functioned in the initial period, the accumulated RSs damaged cell membrane structure as well as membrane-associated respiration and ATP synthesis ability, finally leading to the leakage of cellular building blocks (K+, TOC, DNA and RNA) and irreversible cell death. This study illustrated that the g-C3N4 could be used as an ideal photocatalytic bactericide towards agriculture application to improve the plant resistance to pathogens with good biocompatibility and low-cost.
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