Photocatalytic properties and antibacterial mechanisms of microbial-derived ZnS/CuS nanocomposites

Abstract

The urgency to combat antibiotic-resistant bacterial infections requires new antibacterial materials and methods. Utilizing Shewanella onesidensis metabolism, biological zinc/copper sulfide (bio-ZnS/CuS) composites with excellent visible-light photocatalysis effects and broad-spectrum antibacterial activity were synthesized. During synthesis, over 95% of heavy metal ions were recovered from wastewater through co-precipitation to form metal sulfides. The biocomposite with Zn/Cu ratio at 1/9 (Zn1S/Cu9S) showed the best photocatalytic performance. Under visible-light catalysis of Zn1S/Cu9S, 98.02 ± 0.13% of methylene blue and 81.74 ± 2.12% of rhodamine B were rapidly removed, while sterilization rates exceeded 99.99% against Escherichia coli and 99.98% against Staphylococcus aureus. The biocomposite showed a nanostructure with sizes between 5 and 20 nm. Characterizations including X-ray photoelectron spectroscopy, UV-Vis absorption spectra, and photoluminescence spectra proved its excellent visible light response capacity (>400 nm) and energy utilization efficiency. Scavenging experiments demonstrated photogenerated holes and hydrogen peroxide as the major reactive oxygen species (ROS) that induce bacterial death. Toxicological studies revealed that ROS attacked bacterial cells by damaging membranes, inhibiting energy metabolism, breaking the antioxidant defense system, and compromising DNA integrity. This research presents innovative solutions for tackling bacterial infections and heavy metal contamination through the advancement of microbial synthetic functional nanomaterials.