Dual Fluorometric and Colorimetric Chemosensor Based on Poly(Arylene Ether Nitrile)s Functionalized Zn(II)Porphyrins for Selective Detection of Cyanide

Poly(arylene ether nitrile)s (PAENs) appended with Zn(II)‐porphyrin in varied molar percentages (5% and 10%) are developed as dual colorimetric and fluorometric sensors for highly sensitive and selective cyanide (CN − ) detection. The materials, DP‐5%PAEN@Zn and DP‐10%PAEN@Zn, exhibit significant Soret band shifts at 420 ± 2 nm, accompanied by the appearance of a new absorption band at 436 ± 2 nm, indicating strong CN − binding with high association constants of 1.3 × 10⁴ M − ¹ and 2.3 × 10⁴ M − ¹, respectively. A prominent color change from purple to green allowed for naked eye detection. Spectrofluorimetric studies revealed turn‐off fluorescence with Stern‐Volmer constants (K sv ) of 99.85 × 10 3 M − ¹ for DP‐5%PAEN@Zn and 121.08 × 10 3 M − ¹ for DP‐10%PAEN@Zn, achieving limit of detection (LOD) of 0.177 and 0.099 ppb, respectively. DP‐10%PAEN@Zn demonstrated excellent sensitivity and selectivity toward CN − , and also reusability, as it remained functional after ten TFA treatment cycles. The mechanistic investigation, supported by photophysical, electrochemical, and DFT analyses, revealed a photoinduced electron transfer process via static quenching. Material stability is confirmed through photodegradability, prolonged time, temperature, and humidity testing. Prototype test kits are developed for real‐time visual CN − detection in remote and environmental samples (tap, lake, sewage, and soil). Additionally, a smartphone‐based color recognition assay is implemented for qualitative and quantitative analysis.