Microwave-assisted Synthesis Of Ag/rGO Composites And Their Antibacterial Activities

Bacterial infection is a serious threat to human health.Silver as a traditional antibacterial material,demonstrates an excellent antibacterial activity.And the unique two-dimensional structure of graphene materials,especially its large specific surface area,great biocompatibility,stable physico-chemical properties,can be an excellent carrier of nanoparticles.Silver nanoparticles loaded on graphenesheets(Ag/rGO nanocomposites)can effectively prevent agglomeration between nanoparticles and the overlap of graphene sheets,and have great potential as antibacterial materials.In this paper,graphene oxide(GO)was synthesized by improved Hummers method,and graphene/silver nanocomposites were prepared by microwave-assisted method with silver nitrate and GO as precursors,and sodium hydroxide solution as accelerator.The effects of different promoters,microwave power,microwave time,weight ratio of silver nitrate and graphene oxide,sodium hydroxide concentrations on Ag/rGO nanocomposites were investigated.The crystal structure and morphology of Ag/rGO samples were characterized by XRD,SEM,Raman,TEM and UV-vis techniques.The results displayed the growth process of Ag grains and the deoxygenating degree of GOunder different conditions.Finally,mouse HT22 cells,Gram-negativebacteria(E.coli and P.aeruginosa),Gram-positivebacteria(S.aureus andEnterococcus)as well white rot funguswere used as test objects to explore the antimicrobial and cytotoxicity of Ag/rGO nanocomposites and their potential application value.With five different promoters,such as sodium hydroxide(NaOH),potassium hydroxide(KOH),sodium citrate,urea and ascorbic acid,the experimental results show that the ability of deoxygenation for GO was better with NaOH,KOH and ascorbic acid,followed by sodium citrate and urea.The structural properties and phase of Ag/reduced graphene oxide nanocomposites are connected with the reaction agents.It can be found that NaOH shows the best results in terms of the crystallinity and purity of Ag grains anchored on rGO surface.AgNPs can be uniformly and compactly anchored on reduced Graphene Oxide(rGO)surface,however,Ag and Ag2 O phases coexist in the other foursamples,which will impairthe antibacterial activiteis of the obtained product.The graphene/silver nanocomposites can be obtained by microwave assisted method with NaOH solution as accelerator.In the reaction,the microwave power and the microwave time have influences on the size of the silver nanoparticles,but relatively speaking,the microwave power has a great influence.When the concentration of NaOH solution is 0.1M,the microwave power is 400 W and the effect is 2min,the Ag/rGO composites can be obtained withthe small size of silver nanoparticles at approximatedly 12 nm.GO and rGO have some antibacterial effects,but which are not obvious.With the increase of loading silver nanoparticles and the increase of the sample concentrations,the effects of samples on mice HT22 cells,Gram-negativebacteria(E.coli and P.aeruginosa),Gram-positivebacteria(S.aureus andEnterococcus)as well white rot funguswereoutstanding,and the minimum inhibitory concentration(MIC)was lower.When the silver nanoparticles with small size uniformlyloaded on the rGO sheets,the releasing amount of silver ions and the time of reaction on bacteria or cells determined the antimicrobial activities of samples.