Clean preparation of Ag@Au nanoparticle-modified cotton fabric with durable antimicrobial properties by adsorption

The recurrent occurrence of public health crises has significantly accelerated the development of nano-metal-based antimicrobial textiles. However, several challenges remain, including poor solution stability, low affinity and binding fastness to textiles, and the difficulty of recovering nanometal-containing wastewater in the antimicrobial treatment of fabrics. This can damage the natural microbial ecological balance and reduce the performance of the fabrics. Herein, we synthesized an amino-terminated hyperbranched poly(amidoamine) -capped core–shell structured silver /gold nanoparticles (HBPAA-capped Ag@AuNPs), which exhibited high hot water resistance, high solution stability, and strong affinity to natural textiles. These properties were dependent on the reducible cationic HBPAA. The as-prepared Ag@AuNPs exhibited a positive surface charge of + 48.06 mV and demonstrated the capacity to withstand 100 °C heating in water due to their inherent self-reducing ability. Accordingly, we devised a novel bottom-up coating strategy for cotton fabric, whereby Ag@AuNPs were adsorbed onto the cotton surface with HBPAA serving as a “molecular motor” driven by intermolecular interactions between cationic HBPAA and anionic cotton. The results demonstrated that up to 60 mg/L of Ag@AuNPs were nearly completely adsorbed by cotton, indicating that up to ~ 3 g/kg of Ag@AuNP-coated fabric could be prepared by the cleaning adsorption method. The antimicrobial cotton fabric exhibited active adsorption ability toward bacteria and demonstrated strong organic–inorganic coupling antibacterial properties (cationic HBPAA contributed approximately 30– 60% of the antibacterial activity). Even after 50 standard washes, cotton fabric with Ag@Au content as low as 0.9 g/kg was still capable of killing ~ 100% of E. coli and S. aureus.