Morphology-Dependent Antibacterial Activity of Cu_2-xS Nanostructures: Nanoplates Versus Superparticles

Non-stoichiometric copper sulfide (Cu_2-xS) nanomaterials are promising antibacterial agents, but the role of morphology in regulating their bactericidal performance remains poorly understood. Herein, we rationally design two types of Cu_2-xS nanostructures, namely nanoplates (NPs) and superparticles (SPs). Both materials were prepared via a ligand-directed synthesis method with the comparable sizes, surface ligands, and crystal phase. The antibacterial behaviors of Cu_2-xS NPs and Cu_2-xS SPs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were investigated under dark and 808 nm near-infrared (NIR) light irradiation. The results showed that under NIR light irradiation, Cu_2-xS SPs exhibit a markedly higher bactericidal efficiency against both E. coli and S. aureus than Cu_2-xS NPs, leading to almost complete eradication of bacterial colonies. Notably, S. aureus shows more sensitive than E. coli, and significant growth inhibition is observed even in the absence of laser irradiation. Mechanistic investigations reveal that hierarchical assembly of primary nanoparticles in SPs can promote multiple internal light scatterings, thereby significantly enhancing light harvesting efficiency and further improving the photothermal conversion efficiency. In addition, the SPs exhibited higher peroxidase-like activity, resulting in enhanced reactive oxygen species (ROS) generation and aggravated oxidative damage, and the accelerated Cu²⁺ release kinetics strengthens ionic toxicity.