Perparation And Antibacterial Properties Of Nano-MgO₂ And Its Nanocomposite

The increasingly serious problem of the spread of pathogenic microorganisms has aroused widespread concern among researchers.The development of new antibacterial agents is imperative and promising.Nano magnesium peroxide(Nano-Mg O₂),as a kind of metal peroxide with good biocompatibility and non-toxicity,has great application potential in the field of antibacterial.In this study,different methords are used to prepare nano-Mg O₂and study its antibacterial properties.The silver/magnesium peroxide nanocomposite is prepared by compound modification,aiming to further improve the antibacterial performance of Nano-Mg O₂.The main research process and results are as follows:(1)Two typical process methods are used to prepare Nano-Mg O₂.The phase structure,microscopic morphology,active oxygen content and corresponding purity of the products are analyzed and characterized.The experimental results show that the prepared sample is Nano-Mg O₂ with high active oxygen content(greater than 25%)and high purity(greater than 88%).Microscopic morphology analysis shows that Nano-Mg O₂ is nano-particles assembled from nano-discs with a particle size about 15-100 nanometers.(2)Using ATCC 25922 Escherichia Coli(E.Coli)as the experimental strain to test the antibacterial properties of the samples.The experimental results show that the antibacterial performance of nano-magnesium oxide decreases significantly in the continuous antibacterial experiment.Nano-Mg O₂ can completely kill 7-log E.coli in all three cycles of the continuous antibacterial experiment,and has excellent continuous antibacterial performance.Research on the antibacterial mechanism shows that nano-Mg O₂ has slow release of active oxygen,which means nano-Mg O₂ can slowly release active oxygen with bactericidal ability in a long period of time.After 48 hours,the release rate of active oxygen is less than 50%of the total content.It is the key to the sustained antibacterial properties of nano-Mg O₂.(3)Prepare silver/magnesium peroxide(Ag/Mg O₂)nanocomposites by one-step method and two-step method respectively,and analyze and characterize the silver content,phase structure,and microscopic morphology of the nanocomposites.The one-step method is easy to operate and the process is simple,but the synthesis efficiency is low,about 14%.The prepared nano-composite has a microscopic morphology of 15-30 nanometers of nano-silver particles compounded on the one-pot precipitation magnesium peroxide(OP-Mg O₂).The two-step process is relatively complicated,and the silver composite efficiency is high(greater than 69%).Experiments show that the composite efficiency of the nanocomposites prepared by the two-step method is relatively higher(greater than 69%).The microscopic morphology of the prepared nanocomposites is that 3-15 nanometer silver nanoparticles are uniformly composited on OP-Mg O₂.It is worth noting that the silver nanoparticles are evenly distributed on the surface of OP-Mg O₂ without obvious agglomeration.(4)The antibacterial performance of the Ag/Mg O₂ nanocomposite is significantly better than that of pure magnesium peroxide,and it has sustained antibacterial performance.The 3%Ag/Mg O₂ synthesized by one-step method can completely kill 7-log E.coli in 40minutes.In the continuous antibacterial experiment,it can kill 7-log E.coli in 40 minutes in three consecutive times.The 3%Ag-Mg O₂ sample synthesized by the two-step method has the best antibacterial performance,which can completely kill 7-log E.coli within 15 minutes,and it can completely kill the 7-log E.coli for three consecutive times in the continuous antibacterial experiment.With the same reactant input ratio(3%),the antibacterial performance of the two-step product is better than that of the one-step product.The conversion experiment of nitrotetrazolium blue chloride(NBT)proves that the efficiency of the nanocomposites to generate active oxygen is several times that of pure nano-magnesium peroxide(OP-Mg O₂),and the efficiency of 3%Ag-Mg O₂to produces activity oxygen is higher than that of the 3%Ag/Mg O₂.In the electron paramagnetic resonance(EPR)experiment,compared to OP-Mg O₂which did not produce obvious characteristic peaks of active oxygen,the silver/magnesium peroxide nanocomposites can generate characteristic peaks of superoxide radicals,and the intensity of the characteristic peaks did not decrease significantly after the sample was dispersed for 2 hours,indicating that the nanocomposites have the ability to continuously generate active oxygen,which further explains theirs'long-lasting antibacterial effect.The electrochemical impedance spectroscopy(EIS)experiment shows that the interfacial electron transfer resistance of the samples after compounding silver is greatly reduced.The reduction is conducive to the formation of superoxide radicals by electron transfer,which further explains the excellent antibacterial properties of the silver/magnesium peroxide nanocomposite.