Decoupling of structural evolution and Cu-driven antibacterial performance in Se-substituted CuS powders

Copper-based materials have been widely investigated for antibacterial applications due to their strong antimicrobial activity and relatively low toxicity. Among them, copper sulfide (CuS) has attracted attention owing to its metallic conductivity and sustained release of copper ions. However, the relationship between structural modification and antibacterial performance in CuS remains unclear. In this study, Se-substituted CuS (CuS₁₋ ₓ Se ₓ , x = 0–0.1) powders were synthesized via high-energy ball milling, and their structural evolution and antibacterial properties were investigated. X-ray diffraction revealed lattice expansion with increasing Se content, while Raman spectroscopy confirmed modification of chalcogen bonding from S–S to S–Se and Se–Se configurations. X-ray photoelectron spectroscopy indicated the coexistence of Cu⁺ and Cu²⁺ states, suggesting redox-active surface characteristics. Despite these structural changes, all samples exhibited consistently high antibacterial activity (>99.99%) against both Gram-positive and Gram-negative bacteria. These results suggest that antibacterial performance is relatively insensitive to chalcogen substitution, indicating an apparent decoupling between structural evolution and functional activity. The findings imply that Cu-related surface processes are likely the primary contributors to antibacterial behavior, providing direct evidence for the decoupling between structural evolution and antibacterial performance in CuS-based materials.