Synthesis Of Polyethylenimine (PEI) And Chitosan Functionalized Silver Nanoparticles By A Hydrothermal Method And Their Antibacterial Activity Study

In this study, we report a facile, one-step hydrothermal method to synthesize PEI-functionalized Ag nanoparticles in which no extra reducing agent is needed and PEI serves as a reducing agent and a stabilizing agent. The obtained Ag colloids have been characterized by TEM, UV absorption spectra and laser particle size analyzer.In a typical experiment,50%of PEI stock solution was diluted to5%with pure water, then2mL as-prepared solution was added into a1mL1%AgNO3solution in a beaker, followed by the addition of37mL of pure water. The obtained solution was stirred for at least30min, then concentrated hydrofluoric acid solution was gradually added to adjust the solution pH to4.0. Finally, appropriate volume pure water was added to obtain a40ml solution. The mixed solution was transferred into a Teflon-lined autoclave of50mL, and then sealed and maintained at140℃for4hours.The obtained PEI-Ag nanoparticle have a average diameter of23.5nm. In addition, we found that the size of Ag nanoparticles can be tuned through the alteration of the temperature and growth mode. We can prepare Ag nanoparticles with diameter of81.9nm by using this strategy.. Under an acidic condition, PEI-functionalized Ag nanoparticles are positively charged. More importantly, the Ag colloids exhibited stronger antibacterial activity in the bactericidal test. Its bactericidal efficiency exceeds the commonly used antibacterial agents such as Erythromycin, chloramphenicol and penicillin as well as AgNO3solution. These results prove that our synthesis method is very efficient to produce a stable PEI-functionalized Ag colloid with excellent antibacterial activity. The Minimum inhibitory concentration (MIC) of PEI-Ag colloid against for S. aureus was0.62μg/mL.Then, we try to synthesis of silver nanoparticles capped with chitosan by the above mentioned method. Chitosan was considered to be the only reducing agent and stabilizer in the reaction. We found the morphology and size of silver nanoparticles can be changed according tothe initial temperature and the ratio of reactants by using TEM and UV absorption spectra to characterize the characteristics of the products. This reaction can be summarized as follows: more rod-shaped Ag nanoparticles can be obtained when use the lower concentrations of chitosan in reaction solution,whereas more spherical Ag nanoparticles can be produced when use high concentration of chitosan in the reaction solution;The Low pH promote more Ag nanoparticles with the shapes of rod or triangle,and the high pH condition can produce spherical Ag nanoparticles.