Room-temperature chitosan-assisted in situ formation of silver nanoparticles on citric-acid-functionalized cotton for wash-durable antibacterial activity

Antibacterial textiles are increasingly investigated to mitigate microbial proliferation and improve hygiene, particularly in healthcare and protective applications. Here, a simple water-based, partly bio-based three-step strategy is presented to fabricate laundering-durable antibacterial cotton via citric-acid pre-functionalization and chitosan-assisted in situ formation of silver nanoparticles (AgNPs). Cotton fabrics were first grafted with citric acid to introduce carboxyl-binding sites, then loaded with Ag+ from AgNO3, and finally treated with chitosan, which served as a bio-based reducing and stabilizing agent enabling the formation of AgNPs at room temperature. CIE L*a*b* colorimetric analysis revealed formulation-dependent variations in lightness and chromaticity consistent with optical effects associated with AgNPs. SEM-EDX confirmed a homogeneous distribution of Ag-rich surface domains on the fibre surface, while FTIR and Raman spectroscopy indicated preservation of the main cellulose fingerprints, suggesting limited alteration of fibre chemistry. The functionalized fabrics exhibited >99% antibacterial activity against Staphylococcus aureus and Escherichia coli in the unwashed state, with selected formulations retaining >95% efficacy after 10 standardized laundering cycles. Overall, this bio-based approach, enabling AgNPs formation at room temperature, offers a practical route to durable antibacterial cotton with high wash fastness, making it a promising candidate for a wide range of applications across fields such as health and medicine.