Covalent Immobilization of Phytosynthesized Silver Nanoparticles and Quaternary Ammonium Chitosan on Cotton Fabrics: Enhanced Antimicrobial Durability, Antioxidant Capacity, and Natural Dye Affinity

This study developed a green multifunctional modification strategy for cotton fabrics through covalent coimmobilization of phytosynthesized silver nanoparticles (AgNPs) and N-(2-hydroxy)-propyl-3-trimethylammonium chitosan (HTCC) using dimethyloldihydroxyethyleneurea (DMDHEU). AgNPs were synthesized using <i>Aloe vera</i> extract with an average size of 81.96 nm (PDI 0.191) and integrated with HTCC via a pad-cure process. The cotton fabric modified with DMDHEU, HTCC, and AgNPs (Cotton-DHA, where "DHA" denotes the three modifying agents: DMDHEU, HTCC, and AgNPs) demonstrated synergistic antibacterial activity against <i>Escherichia coli (E. coli)</i> (99.81%) and <i>Staphylococcus aureus (S. aureus)</i> (99.29%), with over 90.00% inhibition retained after 20 washing cycles, indicating robust durability. The Cotton-DHA also exhibited significantly enhanced antioxidant capacity, with an ABTS free radical scavenging rate of 72.51%, in stark contrast to the 4.20% rate of pristine cotton. Natural dye affinity was substantially improved, as evidenced by the increase in <i>K</i>/<i>S</i> value from 0.30 to 2.58. The covalent bonding mediated by DMDHEU ensured durable immobilization, where HTCC provided primary antibacterial action (>94.00%) and AgNPs enhanced the efficacy to >99.00%. This synergistic system provides a sustainable approach to developing high-performance textiles with integrated antibacterial, antioxidant, and dyeing properties.