Green dyeing and functional properties of wool fiber using indigo and dihydroxyacetone system

Indigo dyeing has become one of the most widely adopted green dyeing systems in the textile industry. However, it also has limitations, such as a monochromatic spectrum and reliance on sodium dithionite for redox reactions, which have raised environmental and safety concerns. In this study, a novel indigo@DHA (dihydroxyacetone) complex dyeing system has been innovatively constructed. The DHA reacts with wool fibers through the Maillard reaction, producing a yellow color. DHA also acts as an eco-friendly reducing agent to achieve indigo dyeing of wool. This ultimately results in a yellow-blue mixed color, expanding the color spectrum into the green range. The dyed wool retains its natural scale structure and exhibits excellent UV protection performance (UPF > 1800) and antioxidant properties (ABTS⁺· scavenging rate > 70 %), with a tensile breaking strength of 1.45 cN/dtex. The color fastness to wet rubbing of indigo@DHA samples reaches grade 4-5, which is significantly higher than that of the other samples.