Antimicrobial Finishing Of Cotton Textiles Via Room Temperature Electron Reduction Of Silver Ions

Natural cotton textiles are the most widely used materials in clothing and health care/hygienic products due to their outstanding properties such as softness,hygroscopic,affinity to skin,bio-degradation and renewable.Nevertheless,cotton textiles may act as a nutrient media for the growth of microorganisms under certain conditions of humidity and temperature because of their large surface area and ability to retain oxygen,moisture,dust,spilled food and drink stains,sweat,oil secretions of skin gland and skin dead cells.It may result in deterioration or undesirable changes in aesthetic value of cotton textiles,or even cross-transmission of infectious pathogens.Consequently,imparting antimicrobial activity to cotton textiles has aroused wide concern.Silver nanoparticles?Ag NPs?are believed to have strong inhibitory and bactericidal effects on a broad spectrum of bacteria,fungi and virus.The advantages of Ag NPs as an antimicrobial agent are safe,non-toxic,non-pollution and non-tolerant disinfectant,which make them of great application value in antimicrobial finish of cotton textiles.Generally,the preparation of Ag NPs loaded cotton textiles should satisfy the requirements as follows:easy operation,quick process,low cost,environmentally friendly,non-toxic byproducts and no side effects on the properties of cotton textiles.Therefore,we employed a simple,rapid,green and efficient room temperature electron reduction procedure to fabricate Ag NPs on cotton.Instead of using chemical reducing agents,the electron reduction procedure takes energetic electrons,which are provided by non-hydrogen glow discharge,as the reducing agents.In order to realize the process above,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?and X-ray diffraction?XRD?analyses were firstly conducted to investigate the influence of argon glow discharge on the chemical composition,microstructure and crystal structure of cotton textiles.The results show that plasma has no effect on the crystal structure,while it can change the surface element content and roughness to some extent by excitation and re-deposition of C atoms,result in the modification of hydrophilic properties.Subsequently,we chose an appropriate treating time,which had no influence on the cotton nature,to deposit Ag NPs on cotton textiles.The color of synthesized Ag NPs loaded cotton textiles changes from light yellow to dark yellow,brownish yellow and black,as a result of their localized surface plasmon resonance?LSPR?property,upon the increase in Ag loading amount.Transmission electron microscopy?TEM?shows the silver nanoparticles to be predominantly spherical in morphology,ranging in average size from 4-6 nm,while scanning electron microscopy?SEM?reveals the tendency of Ag NPs to form spheroidal aggregates with dimensions in the range of 40-200 nm,indicating the change in color is due to the size of Ag aggregates rather than the size of a single Ag NP.This theory is further demonstrated by UV-vis absorption spectra.The functionality of Ag NPs imparting to cotton textiles is further measured by studying the antibacterial activity,which turns out exhibiting significant antimicrobial effect toward both Gram-negative bacterium E.coli and Gram-positive bacterium B.subtilis,with 100%microbial death for Gram-negative bacterium E.coli.Higher silver loading leads to an increasing antimicrobial activity.Wash fastness of the Ag loaded cotton textiles was also estimated according to the ISO 105-C02?1989?standard.The result shows that nearly 80%of silver is still remained in fibers after 20 washings when the concentration of AgNO₃ precursor is low,suggesting the possibility of applying Ag/Cotton textiles with a relatively low loading number for wearable devices.