Vapochromic wool fibers for hazardous ammonia detection using xanthohumol biomolecule from natural extract of common hop (Humulus lupulus L.).

Ammonia is a colorless gas, yet it can be fatal if inhaled or ingested in high enough concentrations. Herein, a solid-state colorimetric smart wool (WL) sensor for ammonia was developed. Common hop (Humulus lupulus L.) is a natural resource of spectroscopical dyestuff known as xanthohumol (XN). Wool fabrics were dyed with different concentrations of xanthohumol extract using the high-temperature high-pressure method in the presence of a mordant. The coloration parameters and absorption spectra were employed to explore the yellow-to-white colorimetric shift of the wool fabric after it was exposed to aqueous ammonia. The wool fabric showed an excellent detection limit of 5 to 125 ppm. When the ammonia concentration was increased, the absorbance spectra demonstrated a hypsochromic shift from 498 nm to 367 nm. This could be attributed to changes in the molecular structure of xanthohumol that happen owing to intramolecular charge delocalization. Using transmission electron microscopy (TEM), the mordant/xanthohumol nanoparticles were measured to have diameters of 15-40 nm. The xanthohumol-finished wool fabrics showed good colorfastness properties. The incorporation of mordant/xanthohumol nanoparticles into wool fabrics showed no negative effects on their stiffness or air-permeability.