Ultrafine Ag–Fe alloys with graphene-based cellular monolith as a novel antimicrobial material

Bimetallic silver–iron nanoparticles (Ag–Fe NPs) are an attractive antimicrobial material because of their multifunctional properties. The antimicrobial performance of Ag–Fe NPs is affected significantly by alloying structure, particle size and composition, but the preparation is a challenge due to the large difference in lattice constants of the two elements. An ultrasonic-assisted in situ reduction method was used here to prepare Ag–Fe/graphene-based cellular monolith (Ag–Fe/GCM) materials with well-defined alloy structure, ultrafine size and abundant hierarchical structure. We found that the antimicrobial activity of such materials decreased but the stability of Ag improved with the increase of Fe content within a certain range. The more active Fe in alloys can protect the Ag from oxidation, which reduces the release of Ag+. However, the release of Fe ions led to more generation of reactive oxygen species compared with Ag/GCM, which maintained a high antibacterial activity. By adjusting Fe content, an Ag–Fe/GCM material with optimal performance was achieved. This work not only provides a method for preparing Ag–Fe alloys but is also useful for understanding its antimicrobial mechanism. Moreover, Ag–Fe/GCM material also performs well in filtering of bacterial pathogens, and is a highly promising material for advanced antimicrobial and water-treatment applications.