Optimizing the synergistic effect of CuWO4/CuS hybrid composites for photocatalytic inactivation of pathogenic bacteria

Abstract

Herein, we report an effective strategy to maximize the antimicrobial activity of CuWO4/CuS hybrid composites, prepared by simply mixing CuWO4 and CuS nanopowders with varying weight ratios in phosphate buffered saline solution by ultrasound. The tested bacteria included Gram negative (G(-)) pathogenic bacteria Salmonella typhi, Gram positive (G(+)) pathogenic bacteria Staphylococcus aureus, and G(+) bacteria Bacillus subtilis. The as-prepared composites exhibited much enhanced antibacterial efficiency compared with individual CuWO4 and CuS nanopowders under white light irradiation. The checkerboard array analysis revealed that the combination of 8 mu g mL(-1) CuWO4 and 2 mu g mL(-1) CuS was the most efficient and generated the optimal synergistic effect, showing a complete killing effect on all the tested bacteria from 3 strains with similar to 5.8 log cell reduction. The significantly enhanced catalytic efficiency can be ascribed to the formation of a type-II heterojunction between CuWO4 and CuS, which can effectively improve the charge separation efficiency and increase the light absorption. Moreover, the hybrid composites prepared by ultrasound-assisted physical mixing can effectively increase the interface area, which greatly facilitates the charge mobility and transfer in the interfaces between CuWO4 and CuS. This study offers new insights into the integration of different semiconductors to optimize their synergistic effect on antimicrobial activities for water disinfection.