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 μg mL⁻¹ CuWO₄ and 2 μg 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 ∼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.