Green in-situ synthesis of silver nanoparticles from natural madder dye for the preparation of coloured functional cotton fabric

Dyeing and antimicrobial finishing of cotton fabrics is generally achieved in two steps, generating significant energy consumption. In this study, we report a short process and energy-efficient dyeing process. The colour -functional cotton fabric was prepared by in-situ formation of silver nanoparticles (AgNPs) on the surface of cotton fabric with natural madder dye, which effectively solved the problem of bacterial proliferation on the surface of cotton fabric and low colour fastness of cotton dyed with natural dye. The surface microstructure and dyeing properties of mordant dyed, ethylene glycol diglycidyl ether (EGDE) crosslinked dyed, and AgNPs/EGDE crosslinked dyed cotton fabrics were compared. The Ultraviolet-visible spectroscopy and dynamic light scattering analysis indicated the formation and particle size distribution of AgNPs, respectively. Fourier transform infrared spectroscopy revealed chemical interactions between fabrics, cross-linkers, and madder dyes. Using scanning electron microscopy and X-ray photoelectron spectroscopy analysis, the morphology and surface characteristics of the fabrics before and after dyeing were investigated to reveal the chemical state of AgNPs and the deposition of AgNPs on the fabric surface. The dyeing properties of two silver-doped dyed fabrics were evaluated. The mordant dyed, and AgNPs/EGDE crosslinked dyed cotton fabrics obtained excellent dyeing effects with 9.1 and 8.2 colour depth values (K/S), respectively. The rubbing and washing fastness was about levels 4-5, and the levelness was acceptable. In addition, two kinds of silver-doped dyed fabrics had an excellent inhibitory effect on Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus), and the antibacterial rate was still above 95% after 40 washing cycles. The UV protection factor (UPF) of the three dyed fabrics reached 50 + . This silver nanoparticle one-bath finishing technology generally provides an ideal efficiency and safe, practical application for cotton fabric colouring and functionalization technology.