Preparation Of Subnanometer Silver Colloid And Its Application In Antibacterial Packaging Film

As we all know,silver nanoparticles(Ag NPs)exhibit excellent properties in antibacterial applications,and the smaller the silver particle is,the better antibacterial eff-ect it performed.While currently,among most of the preparation method of Ag NPs it is essential to use strong stabilizer containing S or P,which could ether affect the chemical properties of Ag NPs,or influence the antibacterial effect of Ag NPs.Waterborne polyurethane(WPU)has been widely used in various fields due to its excellent properties,and it has become a hot research topic in recent years.However,there has a very important experimental material in the process of preparing WPU,which means the water of dispersed polyurethane prepolymer has received little attention.Moreover,because of hydrophilic groups in WPU,they are susceptible to attack by microorganisms in the surrounding environment,especially molds.In this paper,at first,we designed and synthesized a kind of bifunctional siloxane oligomers containing two groups as stabilizer,the Si-H groups as reducing groups,and the-NH groups as coordination groups to bond with Ag particles,which can prevent Ag NPs from agglomeration.The ratio of these two groups was control by the hydrolysis process.The ratio of the two ligands groups can control the reduction of silver at the atomic level and nucleation process.The Ag NPs whose size was 2 nm even smaller was synthesized,successfully.TEM,DLS and other tests showed that the particle size of the sample ag-90 was the smallest,which could be controlled within 2 nm,indicating that the particle size distribution of Ag NPs was smaller when the reducing group and the stabilizing group were closer.And the sample Ag-RT and Ag-90 were synthesized under normal temperature and 0? environment,respectively.Indicating that the ice bath environment was more appropriate for this method to synthesize the smaller particle size,and more evenly distributed for Ag NPs.Then,snow in nature was dispersant to prepare six groups of WPU with different soft segment.The test results mean when the polyol molecular weight was 2000 g/mol,polyether WPU(samples WPU-N220)performed better than the polyester WPU(samples WPU-PNA)in totally.Finally,we selected the sample which has the better performance of Ag NPS(sample Ag-90)to composite with WPU(sample WPU-N220),and obtain Silver nanoparticles/waterborne polyurethane(Ag NPs/WPU)composite material with antibacterial properties.The results sh ow that when the content of Ag NPs/WPU is 0,single WPU film has not antibacterial ability.When a certain amount of Ag NPs were added,the inhibition zone diameter of the composite film increased significantly.With the increase of the content of silver nanoparticles in the composite film,the antibacterial effect increased either.And this compound can not only find carrier for the silver nanoparticles but also inhibit the breeding of bacteria in waterborne polyurethane.