Highly effective antibacterial activity and synergistic effect of Ag-MgO nanocomposite against Escherichia coli

Ag-MgO nanocomposite, synthesized by loading small-sized Ag nanoparticles on the surface of MgO nanoparticles, was firstly used as an effective antibacterial agent against Escherichia coli. The microstructure, morphology and composition of the nanocomposite were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray (EDX) analyzer, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) and flame atomic emission spectroscopy (FAES) measurements. An interfacial interaction between Ag and MgO was confirmed by XRD and XPS analyses, which could effectively inhibit the release of silver ions (Ag+) from the nanocomposite. Antibacterial tests showed that the as-prepared Ag-MgO nanocomposite exhibited stronger antibacterial activity against Escherichia coli, compared to pure MgO and equivalent Ag nanoparticles alone, indicating a synergistic effect between Ag and MgO. Based on the results of reactive oxygen species (ROS) detection, the enhanced antibacterial activity of Ag-MgO nanocomposite was attributed to the promotion of ROS production, because Ag particles on the surface of MgO are in favor of electron transfer, which could enhance ROS production via one-electron reduction of oxygen. Taking into consideration easy preparation, low cost, low release rate of Ag+, and high antibacterial activity of Ag-MgO nanocomposite, it is a very promising candidate material for bacterial disinfection.