Compositionally Tuned FeNiMnCuNbAg x High‐Entropy Alloy Nanoparticles With Enhanced ROS Generation and Photothermal Antibacterial Activity

ABSTRACT The development of multifunctional antibacterial nanomaterials is of considerable interest in combating antibiotic resistance and marine biofouling. Herein, Ag‐containing FeNiMnCuNbAgx high‐entropy alloy nanoparticles (HEA‐NPs) with tunable composition were synthesized through a non‐equilibrium arc‐discharge plasma strategy. By introducing Nb to stabilize Ag within the alloy matrix, homogeneous HEA‐NPs with adjustable Ag content were successfully obtained. The resulting nanoparticles exhibited broad‐spectrum antibacterial activity, efficient photothermal conversion, and strong biofilm‐removal capability. In particular, FeNiMnCuNbAg 0.25 HEA‐NPs achieved 99.99% elimination of planktonic Pseudomonas aeruginosa bacteria at a low dosage of 15 µg·mL −1 (15 ppm), while under simulated solar irradiation (1 sun), the biofilm removal efficiency at 50 µg·mL −1 increased from 86% to 98%, demonstrating a pronounced photothermal enhancement effect. Mechanistic investigations combining electron spin resonance (ESR), density functional theory (DFT) calculations, and transcriptomic analysis revealed that the Ag incorporation altered the thermodynamic evolution of oxygen reduction intermediates and modulated reactive oxygen species (ROS) generation behavior. Meanwhile, transcriptomic results indicated that HEA‐NP treatment induced redox imbalance, respiratory dysfunction, and translational suppression in the bacterium. These findings highlight the potential of Ag‐containing HEA‐NPs as multifunctional antibacterial materials for biofilm control and antimicrobial protection in marine‐relevant environments.