Photocatalytic inactivation pathways of E. coli bacteria using bismuth oxyiodide photocatalysts

In this work, a series of bismuth oxyiodide (Bi x O y I z ) photocatalysts were synthesized via a pH-controlled co-precipitation method, an energy-efficient process carried out at room temperature and in an aqueous medium. The materials were evaluated for their ability to inactivate Escherichia coli ( E. coli ) under UV and visible light. Structural, morphological, and electronic characterizations revealed that synthesis conditions critically affect phase composition, surface area, and optical properties. Among the materials studied, Bi 4 I 2 O 5 –9 demonstrated superior visible-light-driven antimicrobial activity, achieving complete bacterial inactivation within 10 min. The proposed mechanism appears to be dominated by direct interactions of photogenerated electrons and holes, superoxide radicals or even singlet oxygen, rather than hydroxyl radical-mediated pathways. The effects of possible Bi 3+ ion leaching and of the synthesis route on the bacteria inactivation were also evaluated, and the unusually high nitrogen content of Bi 4 I 2 O 5 –9 suggests that minor contributions from reactive nitrogen species cannot be fully ruled out. • pH-controlled co-precipitation enabled tailored phase composition and morphology in Bi x O y I z photocatalysts. • Bi₄I₂O₅–9 exhibited outstanding visible-light activity, achieving complete E. coli inactivation within 10 min. • Photocatalytic inactivation is mainly driven by direct charge carrier interactions and reactive oxygen species (O₂• − , 1 O₂), rather than •OH radicals. • Bi 3+ leaching under irradiation was negligible and showed no correlation with antibacterial activity. • Ammonia-assisted synthesis may influence surface chemistry and enhance bacterial interaction. • Minor contributions from reactive nitrogen species (RNS) cannot be fully ruled out.