Designing eco-friendly pH-responsive Azo dyes for sustainable textile fabrics

Invention of high-performance, environmentally friendly disazo acid dyes (D₁-D₄) intended for sustainable textile coloring and pH-responsive sensing applications is reported in this study. Sulphanilic acid and other aromatic derivatives were used in simplified diazotization-coupling procedure to create dyes. Effective integration of azo and sulfonate groups, guaranteeing superior water solubility, was verified by structural characterization. Dyes created bright, high-affinity orange and red colors with remarkable wash and light fastness (ratings: 4-5) when applied to wool and nylon. λ_max values in UV-vis spectra varied according to substituent location, from 479 to 485 nm. Notably, protonation-deprotonation balance drives Dye D₁'s reversible, "smart" color shift from brown to pink in response to pH changes. Among synthesized dyes, D₁ showed a clear and reversible pH-responsive color change, going from brown to pink under increasingly acidic conditions, while D₃ showed mild pH sensitivity and dyes D₂ and D₄ remained color-stable throughout tested pH range of 2-4, displaying distinct chromatic stability profiles. Compared to nylon, the K/S and fastness qualities of wool materials were higher. These results show that synthesized dyes have great promise for creation of novel, pH-sensitive smart fabrics in addition to offering excellent technical performance and high fixing, which reduces environmental leaching.