Copper-doped cobalt‑iron layered double hydroxide nanosheets to enhance multi-enzymatic activities for antibacterial effect

Nanozymes, owing to their multi-enzymatic mimicking activities, have been widely applied in antibacterial fields. However, the effects of metal-doping elements on the structure-activity relationship of most layered double hydroxide (LDH) remain insufficiently understood. Here, we synthesized a series of Co-Fe-Cu ternary LDH nanosheets with varying Cu doping ratios, referred to as CoFeCu-LDH. These CoFeCu-LDH nanosheets exhibit four distinct enzymatic activities, including POD, oxidase (OXD), glutathione peroxidase (GPx), and glutathione oxidase (GSHOx). Notably, Cu doping produces a pronounced synergistic effect, significantly enhancing the enzymatic activities of CoFe-LDH. Specifically, CoFeCu-35 % demonstrates strong POD-like and GPx-like activities, while its OXD-like and GSHOx-like activities are comparatively weaker. Density functional theory calculations indicate that within the CoFeCu-35 % crystal structure, the energy barrier for reactions occurring at the copper site for POD and GPx is significantly lower than that at the cobalt or iron sites. Plate coating experiments further validate that CoFeCu-35 %, in conjunction with a small amount of H 2 O 2 , exhibits a stronger antibacterial effect than CoFeCu-35 % alone. The copper-doped samples effectively induce the production of reactive oxygen species more efficiently than pure CoFe-LDH, leading to enhanced antibacterial activity. Metabolic analyses provide additional insights into these underlying mechanisms. This study not only offers systematic insights into the structural doping design of multi-enzymatically active LDH materials but also presents promising strategies for the development of novel LDH-based antimicrobial agents.