| Bacterial infection has always been a major threat to public health and safety.Protective textiles with self-purification and long-term antibacterial activity,such as masks and protective clothing,have become the first barrier against bacteria,protecting vulnerable populations from bacterial attack.Silver nanoparticles(AgNPs)are widely used in the antibacterial field because of their excellent antibacterial activity and low drug resistance.However,AgNPs are highly agglomerated and susceptible to environmental factors such as oxygen and UV radiation,resulting in poor durability of bacterial inhibition.Lignin is a renewable aromatic polymer of natural plant origin,second only to cellulose in terms of reserves.Its unique three-dimensional network structure,polyphenolic groups,and aromatic backbone give the material good dispersibility and excellent resistance to UV oxidation.Therefore,the effective compounding of lignin with AgNPs is important for the development of new antimicrobial agents with high efficiency,broad spectrum and safety,the construction of textile protection products with durable antimicrobial performance,and the prevention of various pathogenic bacteria.In this work,the microstructure of AgNPs/lignin composite particles was adjusted to enhance the size and morphological effects by modulating the electrostatic and chelating interaction forces between lignin molecules and Ag~+through chemical modifications,thus improving the antibacterial activity of AgNPs/lignin composite particles.On this basis,AgNPs/lignin composite particles were sprayed onto the surface of viscose fabrics using liquid-phase spray deposition method to prepare coated viscose fabrics with excellent durable antibacterial properties.Nuclear magnetic resonance spectroscopy(NMR),scanning electron microscopy(SEM),and inductively coupled plasma emission spectrometry(ICP)were used to characterize the chemical structure and solution aggregation behavior of lignin derivatives.The electrostatic and chelating interaction forces between lignin and Ag~+were studied by kinetic and thermodynamic models.Secondly,characterization means such as SEM,transmission electron microscopy(TEM),and X-ray diffraction(XRD)were taken to characterize the composition and structure of the composite particles,and the antibacterial properties of the composite particles were evaluated and the antibacterial mechanisms were revealed by characterization means such as the twofold dilution method,plate counting method,electron paramagnetic resonance spectrometry(EPR),and SEM.Finally,the antimicrobial durability performance of coated viscose fabrics after physicochemical treatment was evaluated using the inhibition circle method.The main conclusions are as follows:(1)Carboxymethylated lignin with different grafting rates(EHL-CM-0.5 and EHL-CM-1.5)was prepared by carboxymethylation modification of enzymatic lignin(EHL)using sodium chloroacetate based on nucleophilic substitution reaction.The grafting rates of EHL-CM-0.5 and EHL-CM-1.5 were 0.17 mmol/g and 0.53 mmol/g,and the zeta potential increased to 63.12 m V and the water contact angle decreased to 21.9°compared to EHL.SEM results showed that with the continuous introduction of carboxylic acid groups,the interaction with Ag~+was enhanced and a large amount of Ag~+intercalated between lignin molecules,resulting in the gradual transformation of lignin molecules from disordered blocks to ordered layers.Meanwhile,adsorption kinetic and thermodynamic studies showed that the Ag~+adsorption by lignin derivatives was in accordance with the quasi-secondary kinetic model and the Langmuir model.With the increase of carboxylic acid groups in lignin molecules,the adsorption of Ag~+by lignin derivatives could reach up to 3058.04 mg/g,and the adsorption rate constant K_c could reach 3256851.The thermodynamic parametersΔG were all less than 0 andΔH were greater than 0,indicating that the adsorption process is a spontaneous endothermic reaction.(2)Flower-like AgNPs/lignin composite particles(Ag/EHL-CM-0.05)were prepared by simply regulating the initial concentration of lignin using EHL-CM-1.5 as a reducing,stabilizing,and dispersing agent.The TEM results show that the AgNPs in the composites have a particle size of 20-40 nm and a lattice spacing of 0.23 nm,which are uniformly distributed in the lamellae.The results of antibacterial experiments showed that the minimum inhibitory concentration(MIC)of flower-like Ag/EHL-CM-0.05 was 7.8μg/m L for both E.coli and S.aureus,and the bactericidal rate reached 99.9%,which was higher than the antibacterial performance of existing AgNPs/lignin composite particles and comparable to that of cationic antibacterial agents.The results of atomic absorption spectroscopy,EPR,and SEM tests proved that the antibacterial mechanism can be attributed to the synergistic effect of the release of a large number of hydroxyl radicals and Ag~+from the composites as well as the sharp and irregular edged flower-like structures.In addition,the flower-like Ag/EHL-CM-0.05 exhibited good UV oxidative stability with no significant change in crystalline structure after 10 h of UV illumination and a high scavenging efficiency of 18.06%for DPPH·free radicals.Finally,the above antimicrobial agents were loaded onto the viscose fabric,and the antimicrobial experiments showed that the modified viscose fabric had a significant inhibition circle(2.0 cm)against E.coli and S.aureus.However,after rubbing and soaping treatments,the inhibition circle decreased by an average of 0.16 cm and 0.32 cm,respectively.(3)To further improve the antibacterial durability of viscose fabrics,based on the principles of electrostatic adsorption,physical adhesion,and ion mineralization,antibacterial coated viscose fabrics were prepared using three typical biodegradable materials(chitosan CS,polyvinyl alcohol PVA,and sodium alginate SA)as binders and a liquid-phase spray deposition method with flower-like Ag/EHL-CM-0.05 as the antibacterial agent.SEM and EDS results showed that the antimicrobial coating was uniformly wrapped on the surface of viscose fabric fibers,and the flower-like Ag/EHL-CM-0.05 was uniformly distributed in the coating.Fabric Stylus test results show that coated viscose fabrics still maintain excellent comfort.The air permeability test results show that Ag/CS coated viscose fabrics are three times more breathable than pure viscose fabrics.The antibacterial test shows that Ag/CS coated viscose fabric can inhibit 99.9%of bacteria,which is better than Ag/PVA and Ag/SA coated viscose fabric.The average inhibition circle diameter of coated viscose fabrics against E.coli and S.aureus increased by 3.7%and 2.6%after the friction treatment.However,the antibacterial activity of Ag/CS-coated viscose fabrics against E.coli and S.aureus decreased by 13.6%,20.2%,and 20.8%on average after soaping,acid,and alkali treatments,respectively.Subsequently,Ag/CS coated viscose fabric was selected and cross-linked with glutaraldehyde(GA)to further enhance the antibacterial durability of the coated viscose fabrics.The results showed that the antibacterial activity of the Ag/CS/GA coated viscose fabric increased by an average of 7.4%and 0.6%against E.coli and S.aureus,respectively,after soaping,acid and alkali treatments. |
PDF Full Text Request