Coordination Effect Of L-Methionine/Silver On Antibacterial Durability Of The Cotton Fabrics With A Silver Nanoparticle Coating

Cotton fabrics provide an ideal medium for the growth of bacteria.The microbial pathogens living on the fiber surface frequently make the cotton textiles deteriorate and even had potential health risk.Therefore,the development of antibacterial textiles has received widespread attention,and the antibacterial textile market is also growing rapidly.Silver nanoparticles(Ag NPs)have outstanding antimicrobial effect,but their weak adhesive force onto cotton fiber surface often causes undesired silver loss from the antibacterial fabrics.It not only diminishes antibacterial durability,but also leading to environmental and health risks.To improve adhesion of the Ag NPs,numerous strategies have been tried,but long-term antibacterial effectiveness still remains challenging.Here,L-methionine(Met)was proposed as a binder reagent because it has low toxicity towards mammalian cells and has the methyl group may enhance adhesion force of the Ag NPs on cotton fiber surface via its coordination ability.In the first part of this thesis,an antibacterial cotton fabric was fabricated via a very simple pad-dry-cure process:dipping a cotton fabric in an L-methionine solution,heating for esterification,and forming Ag NPs via a reaction of silver nitrate with sodium borohydride.The resulting cotton fabric exhibits an excellent antibacterial property and a remarkable laundering durability.Its bacterial reduction rates(BR)against both S.aureus and E.coli are remained over 97%even after 90 consecutive laundering cycles.These results are contributed to the coordination effect between Met moieties and the silver atoms on the surface of Ag NPs.Moreover,the modification gives insignificant damages on the cotton natures such as tensile breaking strength,water absorptivity,and vapor permeability.Basing on the results,in the second part of the thesis,we added carboxymethyl chitosan(CMC)to the binder formula to further improve laundering durability of the antibacterial function.The surface modification on the fabric was carried out by using a mixed solution of CMC and Met,and Ag NPs were formed via a redox reaction of silver nitrate and sodium borohydride on the fabric surface.The chemical structure and composition of the fabric surface were examined,and the antibacterial effect and its washing durability were evaluated.It was found that the amidation'reactions between CMC and Met make more Met molecules grafted on the fiber surface,further enhancing the adhesion stability of Ag NPs through the coordination bonds with Ag NPs,and leading to the improved washing resistance of the antibacterial cotton fabrics.Compared with first part in the work,this approach achieved better antibacterial durability even the silver ion concentration used to synthesize Ag NPs was reduced to 1%.After 150 consecutive laundering cycles,the antibacterial rate against S.aureus and E.coli could be remained at above 98%.Cytotoxicity tests cleared that the antibacterial fabric is safe to human skin.Moreover,important cotton properties such as breathability,water absorption and flexibility were largely preserved when comparing with the original cotton fabrics.This research successfully confirmed that coordination effect between Met moieties and Ag NPs greatly enhances antibacterial durability of cotton fabric,showing an effective way to fabricate antibacterial cotton fabrics with little silver dosage.It has good theoretical significance and practical application potential for the development of production in antibacterial textiles.