Molten salt-assisted one-pot synthesis of Ag nanoparticles supported on clay minerals for enhanced antibacterial performance

Supported silver nanoparticles (AgNPs) have been extensively used as antibacterial agents in biomedicine, biotechnology, and environmental remediation. However, a facile and scalable method for preparing homogeneously dispersed AgNPs on clay minerals remains a challenge. In this study, a one-pot method was successfully developed for the synthesis of homogeneously dispersed AgNPs supported on the surface of clay minerals (e.g., montmorillonite (Mt) and palygorskite (Pal)). Typically, clay minerals were mixed with AgNO₃ (as a precursor) and NaNO₃ (as a dispersant) by thorough grinding in a mortar, and then the mixture was heated slowly. AgNO₃ undergoes thermal decomposition to generate AgNPs via a self-reduction process, without the assistance of any external reductants. The free ions dissociated by molten NaNO₃ inhibit the aggregation of AgNPs. Specifically, AgNPs were uniformly dispersed on Mt and Pal. Correspondingly, the average particle sizes of the AgNPs were determined to be 10.71 ± 2.16 nm for 6% Ag/Mt-s and 6.07 ± 3.26 nm for 6% Ag/Pal-s, respectively. The antibacterial performance of the nanocomposites was associated with both the concentration of the target materials and their stability in the medium. Specifically, the physicochemical properties of Pal facilitated the small particle size of AgNPs, which in turn enhanced their antibacterial activity. The findings of this study highlight the advantages of utilizing clay minerals as supports to realize the high antibacterial activity of AgNPs. Meanwhile, this study provided a novel and facile strategy for synthesizing silver/clay mineral nanocomposites with homogeneously dispersed silver nanoparticles supported on the surface of clay minerals, without chemical reductants or surfactants. This study provided a theoretical basis for the design and preparation of high-efficiency, low-cost antibacterial silver/clay mineral nanocomposites in the future.