A novel n–p–n type ZnO/BiOI/AgI ternary heterojunction with enhanced visible-light photocatalytic performance for pollutant degradation and antibacterial applications

Abstract

In this study, novel ZnO/BiOI/AgI ternary heterojunction photocatalysts were synthesized via a facile precipitation method to address challenges in organic pollutant degradation and microbial disinfection under visible light irradiation. The composites were systematically characterized (XRD, SEM, TEM, XPS, BET, UV-vis DRS, and PL), showing significantly enhanced visible light absorption, efficient charge carrier separation, and superior photocatalytic performance, compared to binary and single-component counterparts. The optimized ZnO/BiOI/AgI-3030 sample achieved 98.1% degradation of Rhodamine B (RhB) and 59.1% degradation of Norfloxacin (NOR) within 3 hours, attributed to the synergistic effects of the heterojunction structure, which facilitated efficient charge transfer and promoted the generation of reactive oxygen species (ROS). Furthermore, the composite demonstrated remarkable antibacterial activity against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and methicillin-resistant Staphylococcus aureus (MRSA), with bactericidal rates exceeding 99.8%. Cytotoxicity assays revealed 88.79% inhibition of DLD-1 colorectal cancer cells. Mechanistic studies confirmed the formation of a unique n–p–n heterostructure, enabling effective charge carrier separation and strong redox capabilities. Additionally, the photocatalysts exhibited excellent stability and reusability over four consecutive degradation cycles, maintaining high catalytic efficiency. These findings underscore the potential of ZnO/BiOI/AgI ternary composites as efficient and sustainable photocatalysts for environmental remediation and antimicrobial applications.