Reconciling the monodispersity of bioinspired ZnO nanoparticles on palygorskite nanorods for a well-balanced antibacterial effect and biocompatibility

Abstract

In order to study the effect of support on the antibacterial activity of ZnO nanoparticles formed in the bioinspired process, a series of palygorskite (Pal) supported ZnO nanocomposites (ZnO/Pal) were fabricated using licorice extract and the antibacterial actions related to the structure of loaded ZnO nanocomposites was elucidated. The samples were characterized by the means of UV–vis, XRD, TEM, FTIR, TG and XPS, and the antibacterial properties were determined by the agar disk diffusion assay and colony counting assay. The structural analysis revealed that pure ZnO nanoparticles with average grain diameter of about 11 nm were formed in the green bioinspired process and anchored on the surface of Pal nanorods. And with Pal amount decreasing (ZnO loading increased from 10 % to 40 %), the ZnO NPs aggregated intensify and promoted the assembling of ZnO/Pal nanorods into bigger clusters, and four kinds of ZnO/Pal with different morphologies were formed. Among them, 20 % loading of ZnO/Pal showed antibacterial activity comparable to that of 30 % and better than that of 40 %, because ZnO nanoparticles in 20 % ZnO/Pal are monodispersed on Pal nanorods that maintained full exposure and high activity of ZnO NPs as well as better killing efficiency than those with clustered ZnO NPs. The mechanism analysis demonstrated that the bacteria-adsorbed capacity of Pal and the enhanced contact of small ZnO NPs with bacterial cells leading to intensified membrane-damage and intracellular metabolic imbalance are the main bactericidal actions of ZnO/Pal nanocomposites. This study first gave insight into the structure-related antibacterial behavior of ZnO/Pal nanocomposites, and provides an improved green way to design efficient clay-supported ZnO antibacterial nanomaterials.