Design and fabrication of green and sustainable vapochromic cellulose fibers embedded with natural anthocyanin for detection of toxic ammonia.

Exposure to colorless ammonia gas may lead to damage in human organs or even death. Herein, we describe facile fabrication of an environmentally-friendly, portable, reversible, and sensitive solid-state colorimetric cellulose (Cell)/anthocyanin (Anth) vapochromic sensor that exhibits instant visual color change to both gaseous and aqueous phases of ammonia. The naturally occurring anthocyanin can be easily extracted from the red-cabbage plant and applied as a direct dyestuff onto viscose fibers in the presence of potassium aluminum sulfate as mordant to generate nanoparticles of mordant/anthocyanin coordinated complex. Thus, upon exposure to aqueous ammonia, an instant color change of the smart (Cell-Anth) diagnostic assays, from purple to colorless, was noted and quantitatively probed via both CIE Lab coordinates and UV-Vis spectral measurements. Importantly, the fabricated (Cell-Anth) viscose fabric showed rapid responses, fraction of second, with a good limit of detection (LOD) in the range of 200-1200 mg L. This receptor also demonstrated ratiometric changes in the UV-Vis absorbance spectra, giving a hypsochromic shift from 611 to 375 nm upon increasing the total content of ammonia in an aqueous media. The morphologies of Cell-Anth fabrics as well as particle size of the generated mordant/dye complex on the fabric surface have been characterized by transmission electron microscopic (TEM), scan electron microscopy (SEM), energy-dispersive X-ray patterns (EDX) and Fourier-transform infrared spectroscopic (FT-IR). The comfortability of the dyed cellulose fibers was also investigated in terms of their bend length, air-permeability and colorfastness properties. Significantly, the present study offers a promising onsite vapochromic device that enables detection of ammonia in either aqueous or gas phase in various environments and products.