Eco‐Friendly Colorimetric Nanofiber Design: Halochromic Sensors with Tunable pH‐Sensing Regime Based on 2‐Ethyl‐2‐Oxazoline and 2‐ <i>n</i> ‐Butyl‐2‐Oxazoline Statistical Copolymers Functionalized with Alizarin Yellow R

Colorimetric nanofibers provide visual, easy-to-interpret sensors for personal use as well advanced applications. The potential of 2-n-butyl-2-oxazoline (B) and 2-ethyl-2-oxazoline (E) statistical copolymers a universal, versatile support platform nanofibrous halochromic sensor design is demonstrated. These polymers are electrospinnable from eco-friendly solvent systems, while wettability, moist adsorption capacity, water-solubility the membranes can be easily tuned by changing B/E monomer ratio, ensuring wide applicability. sensing functionality introduced incorporating alizarin yellow R (AYR) chromophore, which covalently modified with an ethyl ester-group or short poly(2-n-butyl-2-oxazoline) chain, demonstrated to simultaneously prevent dye-leaching allows tuning pH-sensing window. colorimetric reversibly respond toward aqueous solutions different pH, (hydrochloric) acid alkaline (ammonia) vapors, several biogenic amines detection limits low 5 ppb. Tunability responsivity, sensitivity, pKa via manipulation dye–polymer interactions, determined polymer structure semi-crystallinity, chain length AYR-modified polymer, discussed. Preliminary proof-of-principle studies indicate developed sub-ppm amine vapor detection, may serve basis future applications in food packaging breath analysis.