Enhancing the photostability of curcumin on silk through baicalin modification: A sustainable approach to addressing the critical challenge of poor lightfastness in bio-colorants

A fully bio-based photo-stable CCM is fabricated via ‘zero-length’ coupling strategy. • The exhaustion of CCM Mod on silk descends with pH due to ion−ion interaction. • The lightfastness of dyed silk follows: CCM Mod  > BCL/CCM blends > CCM. • The K/S loss of CCM Mod dyed silk is 42.74% less than half of that of CCM dyed silk. • Silk fabric dyed with CCM Mod attains a UPF value of 50+. Utilizing low-cost bio-resources for developing textile dyestuffs promotes the progress of sustainable textile industry. Curcumin (CCM) stands out as one of the most promising yellow bio-colorants owing to its high color value and bioactivities; however, its application in large-scale dyeing industry is significantly hindered by issues of photo-fading and hydrophobicity. Although mordant dyeing, chemical modification, and compound dyeing have demonstrated their effectiveness, notable but unavoidable drawbacks persist, including substantial color changes, the introduction of hazardous moieties, and dyeing competition. In this study, a fully bio-based, photo-stable, and water-soluble CCM derivative (CCM Mod ) is synthesized through a ‘zero-length’ coupling strategy employing baicalin (BCL) as dual functional UV absorber and antioxidant. The structure of CCM Mod is verified using FTIR, UV-Vis absorption spectroscopy, and HPLC-MS. The investigation of adsorption kinetics reveals that CCM Mod initially undergoes rapid adsorption onto fiber, followed by a gradual diffusion into fiber until an equilibrium is reached. The pseudo-second-order kinetic model provides a superior description of the adsorption behavior compared to the pseudo-first-order kinetic model, indicating that chemical interactions predominantly govern the process. Silk fabric dyed with CCM Mod exhibits a significantly enhanced light fastness, improving from level 1.5 to 3, along with improved washing and rubbing fastness, in comparison to fabric dyed with CCM. After 20 h of exposure to artificial light, the K/S loss for silk dyed with CCM Mod is 42.74%, which is less than half of that observed for silk dyed with CCM (87.16%). The UPF value of silk dyed with CCM Mod (5% owf) reaches 50+. The proposed facile coupling strategy not only addresses the photo-fading limitations of CCM but also offers a transferable approach for modifying other bio-colorants, thereby expanding their applications in food, cosmetics, etc. Download: Download high-res image (427KB) Download: Download full-size image