Cobalt-Doped Zinc Oxide Nanoparticle–MoS₂ Nanosheet Composites as Broad-Spectrum Bactericidal Agents

The design and engineering of high-performance antimicrobial agents is critical for combating antibiotic resistance. In the present study, a rapid and broad-spectrum bactericidal agent is developed based on nanocomposites consisting of cobalt-doped zinc oxide (CoZnO) nanoparticles and MoS₂ nanosheets. The CoZnO/MoS₂ nanocomposites are prepared by a facile chemical precipitation method at controlled CoZnO and MoS₂ feeds. Scanning and transmission electron microscopic measurements show that CoZnO nanoparticles (ca. 10 nm in diameter) are clustered on the MoS₂ nanosheet surface, which facilitates the charge separation of the photo-generated electron–hole pairs, leading to enhanced photodynamic antimicrobial activity. Antibacterial assays in the dark show that the CoZnO/MoS₂ nanocomposite prepared at 30 μg of MoS₂ feed (CoZnO/MoS₂-30) exhibits the best performance among a series of samples, with minimum inhibitory concentrations of 0.25, 0.8, and 1.8 mg mL^–1 toward the Gram-negative bacterium Escherichia coli, Gram-positive bacterium Staphylococcus aureus and fungus Aspergillus flavus, respectively. The antibacterial performance is markedly enhanced under photoirradiation, where 94.0% inactivation of E. coli is achieved with 20 μg mL^–1 CoZnO/MoS₂-30 nanocomposite under photoirradiation (15 W, 360 nm) for 5 min. The high antibacterial activity can be ascribed to peroxidase-like photocatalytic activity that is conducive to the generation of reactive oxygen species, as evidenced in transmission electron microscopy, electron spin resonance, and intracellular glutathione oxidation measurements. The results of the present study highlight the significance of CoZnO/MoS₂ nanocomposites as potent photodynamic antibacterial agents.