Study On Magnetic And Antibacterial Nanocomposites With Dual Action Mechanism

With the continuous improvement of people’s living standards,people’s desire for healthy living surroundings is becoming stronger and stronger.As people communicate more and more frequently,it also provides the convenience for the spread of bacteria.Super bacteria also appeared and traditional antibacterial material has been difficult to play effective role.To make response to the potentially daunting complexity of the microbial population and microbial antibiotic resistance,efforts made to prepare environmentally benign powerful antibacterial are becoming crucial.In this article,we report a facile and green technology called " layer by layer self-assembly " to fabricate multilayers on MNPs with quaternized chitosan and sodium alga acid.Then,AgNPs were decorated on MNPs with L-ascorbic acid as reducing agent and multilayers on the surface of MNPs as stabilizer.After that,we got a kind of dual-antibacterial and recyclable magnetic nanocomposite（CG7@Ag）.We also studied different assembly conditions and immobilization of Ag nanoparticle under disparate situations.Specific research process is as follows:1.Iron oxide nanoparticles（Fe₃O₄）were prepared through an improved chemical coprecipitation method.Then the surface of Fe₃O₄ were modificated with polyacrylic acid.By the alternating adsorption of oppositely charged polyelectrolytes,multilayers were assembled on Fe₃O₄.Finally,L-ascorbic acid was used as reducing agent to reduce Ag+ to Ag nanoparticle.The assembly process and chemical composition of the composites were characterized by fourier transform infrared spectra（FT-IR）,X-ray photoelectron,thermogravimetric analysis（TGA）,transmission electron microscope（TEM）,zeta potential and dynamic light scattering（DLS）.The kinetics of silver ion release was monitored by inductively coupled plasma mass spectrometry（ICP）.E.coli and S.aureus was used as model to test the antibacterial properties of the dual-antibacterial agent including manufacture of inhibition zone;time-killing assay and regenerability antibacterial test.CG7@Ag exhibited rapid and efficient biocidal abilities against both E.coli and S.aureus.And high bactericide efficiency still remained after five cycles.2.We investigated the influence of the four factors:addition amount of polyacrylic during surface modification of Fe₃O₄;the charging sequence of magnetic nanoparticle dispersion and polyelectrolyte solution;the concentration of polyelectrolyte solution and the duration of the assembly on the process of assembly.We tracked and analysed the assembly process by zeta potential and dynamic light scattering（DLS）to determine the best assembly conditions.3.TEM was carried out to observe the size of the silver nanoparticle immoblized on magnetic nanocomposite and analyze the influence of the concentration of AgNO3 on the size of silver nanoparticle.Then we tested the antibacterial property of the samples by manufacture of inhibition zone and time-killing assay to confirm the influence of the size of the silver nanoparticle.We found that smaller particle size is benefit to the improvement of the antibacterial properties.