Eco-friendly fabrication of colorimetric cotton sensors via UV-photografting and covalent immobilization for ammonia gas detection

Colorimetric textile sensors are attract significant attention in the sensor market due to their ability to exhibit easily distinguishable color changes at low fabrication costs. Typically, conventional dyeing methods are employed to immobilize halochromic dyes onto textile surfaces. However, these methods often result in sensors with poor wash fastness and durability. In this study, to prevent dye leaching, colorimetric cotton sensors for ammonia detection were developed by forming covalent bonds between halochromic dyes and fabric. The hydroxyl groups of cellulose were substituted with three vinyl coupling agents through UV photografting. Subsequently, the modified cotton fabrics underwent chemical reactions via different pathways to produce the colorimetric cotton sensors. The color changing properties, wash fastness, rubbing fastness, and durability of the fabricated sensors were evaluated to investigate the effects of the immobilization method. The fabricated sensors demonstrated an excellent colorimetric response to ammonia gas exposure. Compared to sensors prepared using conventional dyeing methods, these sensors exhibited superior wash and rubbing fastness while maintaining gas sensing performance after repeated wash and rubbing. These improvements are attributed to the strong covalent bonds formed between the dye and the cotton fibers. The proposed method allows for the production of colorimetric cotton sensors with enhanced wash and rubbing fastness without dye modification or purification. Moreover, this approach supports the integration of various dyes and fabrics, enabling the development of versatile colorimetric textile sensors for detecting a wide range of gases. The straightforward fabrication process and compatibility with diverse dye-fabric combinations highlight the potential for industrial applications.