Mesoporous silica-protected silver nanoparticle disinfectant with controlled Ag⁺ ion release, efficient magnetic separation, and effective antibacterial activity

Ag is the most effective metal disinfectant against pathogenic microorganisms and thus, various approaches have been exploited to enhance the dispersity and control the release of Ag⁺ ions from Ag nanoparticles. In this study, a superparamagnetic Fe₃O₄@SiO₂@Ag@porous SiO₂ disinfectant with a double-layer core-shell structure was developed. Its superparamagnetic Fe₃O₄ nanosphere core ensured its good dispersity in water and allowed its easy magnetic separation after treatment. Its dense SiO₂ inner shell protected the Fe₃O₄ nanosphere core and allowed a good loading of Ag nanoparticles. Its mesoporous SiO₂ outer layer effectively protected the Ag nanoparticles from detachment, and its mesoporous channels resulted in lower silver oxidation and dissolution for the controlled release of Ag⁺ ions. Thus, a highly efficient, silver-based disinfectant was developed, as demonstrated by its effective disinfection of <i>Escherichia coli</i> bacteria with good recycle performance, while the silver concentration in the treated water met the MCL of silver for drinking water.