Preparation Of Silver Nanoparticels By Bio-reductants And Their Applicati On For The Antibacterial Functionalization Of Poly(lactic Acid) Non-woven Fabric

Environmental protection is one of the hottest topics.Polylactic acid(PLA)fiber,as a renewable and green synthetic fiber,has drawn more and more attention.Owning to its unique biocompatibility,biodegradability,safety and non-toxic properties,PLA non-woven fabric has found applications in many fields including medical,building materials and home textiles.However,the poor antibacterial ability of PLA fiber limits its application ranges,and consequently the antibacterial finishing of PLA fiber is of great significance.Silver nanoparticles(Ag NPs)have the characteristics of wide spectrum,high efficient and safe antibacterial performance,and are very suitable for the antibacterial finishing of non-woven fabric.Considering the fact that the biological reduction approach for the preparation of Ag NPs has the advantages of being eco-friendly,rapid and efficient,three kinds of bio-reductants(PLA hydrolysate,banana peel extract and chitosan)were used in this study to prepare Ag NPs,and then the resulting Ag NPs were applied the antibacterial finishing of PLA non-woven fabric for the purpose of enhanced antibacterial ability.In this regard,the biosynthesis conditions of Ag NPs prepared by three kinds of bio-reductants,the application of Ag NPs,and the antibacterial ability and washing durability of the treated PLA non-woven were investigated.The optical characteristics and storage stability of Ag NPs were analyzed by UV-Visible absorption spectrophotometer and Malvin particle size analyzer;the morphologies of Ag NPs and silver-loaded non-woven fabric were characterized by scanning electron microscope;the crystalline structures of Ag NPs and silver loaded non-woven fabric were studied by X-ray diffractometer;and the antibacterial performance and washing durability of the treated PLA non-woven fabric were determined by the shake flask method for the evaluation of the antibacterial activity of textiles.In the presence of polyvinyl pyrrolidone as a stabilizer,the hydrolytic degradation products of PLA fber that contain reducing hydrolyzates(lactic acid and oligomers of lactic acid)were successfully applied to prepare Ag NPs with no use of additional reductants.The Ag NPs prepared at p H 9 and 90 oC had an average size of 80 nm,and exhibited good storage stability.PLA non-woven fabric was successfully treated with Ag NPs using an impregnation technique at p H 4 and 70 oC,and the treated fabric exhibited excellent antibacterial activity against Escherichia coli and Staphylococcus aureus,even in the case of a low amount of Ag loading.In the case of the preparation of Ag NPs by banana peel extract,the size of Ag NPs decreased first and then increased with the increase in temperature and dosage of peel extract extract.The prepared Ag NPs were negatively charged,ensuring that they could still show good dispersion stability after storage for 4 weeks.The PLA non-woven fabric treated with the as-prepared Ag NPs turned yellow,and the color gradually deepened with the decrease in the p H of finishing solution.In the case of the preparation of Ag NPs by chitosan which simultaneously acted as reducing agent and stabilizer,chitosan could only produce Ag NPs under neutral condition due to the limitation of its solubility and reducing capacity.The Ag NPs prepared by the optimized process were approximately spherical,with small particle size,narrow particle size distribution and better storage stability.A layer of protective film caused by chitosan was found on the surface of the treated PLA fiber,and Ag NPs was observed on the surface by using the high power electronic microscope.The antibacterial properties and laundering durability of PLA non-woven fabric treated with the Ag NPs prepared by three bio-reductants were studied.The results showed that all of the Ag NPs were able to impart outstanding antibacterial ability to PLA non-woven fabric,and the bacterial reduction rates for Escherichia coli and Staphylococcus aureus were over 99%.Among the non-wovens treated with three Ag NPs,the fabric treated by chitosan-Ag NPs owned the best washing durability,and the bacterial reduction rates were still above 98% even after 20 washing cycles.