A self-matching antibacterial coating of nano-copper oxide@dealkaline lignin/citric acid with reusable on-demand antibacterial interface protection.

The adhesion and proliferation of bacteria on object surfaces can lead to grain waste and health risks. Lignin, as a byproduct of the papermaking and biorefining industries, exhibits significant potential for the development of sustainable materials. In this paper, we utilize dealkaline lignin to green-regulate the morphology of nano‑copper oxide, enhancing its dispersion and stability, with the aim of developing a novel green antibacterial coating. On the one hand, the dealkaline lignin forms an organic protective layer on the surface of CuO NPs, effectively promoting the dispersion and stability of CuO NPs. On the other hand, the polar groups rich in dealkaline lignin and citric acid can form an antibacterial interface layer containing hydrogen bonds and coordination interactions during the rapid evaporation of ethanol. Therefore, the nano‑copper oxide @dealkaline lignin/citric acid (CDC) coating layer exhibited rapid antibacterial effects (antibacterial rate > 99% within 1 min), sustained antibacterial activity (>80% after 7 days; >85% after 7 reuse cycles). In addition, the CDC also showcased fascinating features such as adhesion, rapid photothermal response (reaching 95.7 °C within 30s), hydrophobicity and biosafety. In the application of contact sterilization and seed coat removal microorganisms, the CDC showcases promising application prospects.