Preparation And Antibacterial Properities Of Ag/MgO Nanocomposites

The reproduction and variation of harmful bacterial and microorganisms are great harmful to people's health and the development of society. Therefore, in order to inactive harmful bacteria, researchers carried out a great deal of research, and a series of inorganic antibacterial agents were prepared. Among these traditional inorganic antibacterial agents, photocatalytic antibacterial agents show antibacterial activity only under irradiation of a certain wavelength light, while silver has strong antibacterial activity, but it has agglomeration, severe burst release and other shortcomings. As a new type of inorganic antibacterial material, MgO can overcome the above disadvantages, so it has becomes a hotspot in antibacterial research. However, the antibacterial properties of MgO NPs are relatively weaker which limited its applications and developments, composite and doping are effective methods to improve the physical and chemical properties of metal oxides. Therefore, Ag-loaded MgO and Ag-doped MgO nanocomposites were prepared in this paper, the mechanism and the antibacterial properties of these composites were investigated.Ag-loaded 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-loaded MgO nanocomposite exhibited stronger antibacterial activity against E. 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-loaded 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.Ag-doped MgO composite was prepared by sol-gel method, the structure and morphology of composite was analyzed and the antibacterial activity was studied as well. Compared with pure MgO, Ag-doped MgO exhibited smaller particle size and stronger antibacterial activity. On one hand, Ag doping had an effect of restraining the crystallization and crystal growth of MgO. On the other hand, Ag doping would lead to an increase of oxygen vacancy. In addition, the Ag NPs doped in the crystal of MgO formed a conductive network which could accelerate electron transfer, and facilitate one-electron reduction of adsorbed oxygen to generate ?O₂^-.The combined effect of above two aspects resulted in a better antibacterial activity of Ag-doped MgO. In addition, this composite had a relatively low silver release, which could contribute to a lasting antibacterial activity. Taking into consideration easy preparation, low cost, low release rate of Ag⁺, and high antibacterial activity of Ag-doped MgO nanocomposite, it is a very promising candidate material for bacterial disinfection.