Synthesis Of Fe₃O₄ Nanoparticles And Fe₃O₄-GO-Ag Nanocomposites And Research On Antibacterial Properties

The issue on water environment is of great concern with the increasing development of economy in our country,of which pathogenic bacteria pollution is becoming more and more prominent.The water pollution of pathogenic bacteria mainly concentrated in two aspects.One is pollution of pathogenic bacteria in sewage,the other one is the pollution of pathogenic bacteria in drinking water.Now there are limitations that the removal of bacteria in the wastewater and drinking water treatment.In recent years,antimicrobial properties of nano materials have drawn great attention for their strong bactericidal effect and low toxicity.Fe3O4 nanoparticles have been widely used in the field of medicine for unique electrical and magnetic properties.This paper describes the synthesis Fe3O4 nanoparticles by co-precipitation method for antibacterial application.Besides,Fe3O4-GO-Ag nanocomposites were prepared,combining with the antimicrobial properties of Fe3O4 nanoparticles and magnetic separation,super strong sterilization ability of nanometer Ag and the surface structure of the GO.Specific research work and results include the following three aspects.In the first part,the magnetic Fe3O4 nanoparticles were synthesized using co-precipitation.to Magnetic Fe3O4 nanoparticles were characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD)and magnetic intensity(VSM).Results showed that Fe3O4 nanoparticles structure were spherical,the average size was 25.73 nm.And it was clear that the Fe3O4 characteristic peak appeared in X ray diffraction spectrum.The average particle size of Fe3O4 nanoparticles size was ca.30nm which was calculated using the Scherrer formula.Magnetic saturation intensity analysis showed that the experiment of Fe3O4 nanoparticles have super-paramagnetism with magnetic saturation value of 55.16 emu/g.The antibacterial properties of Fe3O4 nanoparticles were investigated under different concentration and time.Results showed that the antibacterial properties of Fe3O4 nanoparticles were strongly dependent on its concentration.When the concentration was 25 ug/mL,sterilization rate of E.coli was less than 10%,sterilization rate of staphylococcus aureus was less than 5%;When the concentration increased to 150 ug/mL,the E.coli sterilization rate reached 92%,the Sterilization rate of staphylococcus aureus was 85%.In addition,this experiment also has carried on the simple to the antibacterial mechanism of nano Fe3O4 discussion,Fe3O4 nanoparticles produced ROS,resulting in oxidative stress was the possible mechanism of the bacterial death.In the second part,graphene oxide was prepared with the improved Hummer preparation.Then Fe3O4-GO composite was synthesized using chemical co-precipitation method.And Fe3O4-GO-Ag nanocomposite was prepared using the method of surface reduction.The characterization of Fe3O4-GO-Ag nanocomposite were achieved using scanning electron microscopy(SEM)and transmission electron microscopy(TEM),X-ray diffraction(XRD),EDS energy spectrum,Raman spectrum and magnetic strength analysis.In the third part,the antimicrobial properties of GO,Fe3O4-GO and Fe3O4-GO-Ag were compared under different concentrations.Then the antibacterial properties of Fe3O4-GO-Ag were detail investigated under different time,pH,temperature and bacterium concentrations.The reusability,stability and synergistic antimicrobial properties of Fe3O4-GO-Ag were also studied.The results showed that Fe3O4-GO-Ag exhibited the best antibacterial property compared to that of GO and Fe3O4-GO.When time increased from 60 min,its antibacterial rate almost reached 100%.When the temperature was more than 37 degrees,sterilization rate reached the maximum.Under different pH and concentration of bacteria liquid,Fe3O4-GO-Ag nanocomposite sterilization rate was very high.After recycling six times,the sterilization rate of E.coli was more than 70%.The antibacterial mechanism of Fe3O4-GO-Ag nanocomposite was discussed.And through the experiment we found that the synergy of Fe3O4 nanoparticles,silver nanoparticles and graphene oxide was the important reason for the high antibacterial efficiency of Fe3O4-GO-Ag nanocomposite.