Fiber colorimetric sensors with ambient humidity tolerance for NH3 sensing

Colorimetric sensors with visual color changes toward toxic gas have been investigated to prevent potential hazardous accidents caused by leakage. The sensitivity of most colorimetric sensors in practical applications is interfered with ambient humidity. This work introduced a hygroscopic substance lithium chloride (LiCl) to be used as humidity compensation to alleviate humidity interference to colorimetric sensor. Cellulose-based colorimetric fibers were prepared from waste cotton using chlorophenol red as an indicator dye in a LiCl/DMAc solvation system. The obtained colorimetric fibers responded quickly to NH3 within 30 s at 50% RH. At the same time, this colorimetric fiber has excellent selectivity and excellent reusability, which could maintain 82% of the original colorimetric response over several cycles. Because of the flexibility, this NH3 sensing colorimetric fiber can be sewn into patterned textiles for manufacturing wearable toxic gas sensors with visual output.