Rapid and Selective Detection of Cyanide Anion by Enhanced Fluorescent Emission and Colorimetric Color Changes at Micromole Levels in Aqueous Medium

One main source of cyanide (CN−) exposure for mammals is through the plant consumption; thus, the sensitive and selective cyanide detection in plant tissue is a significant and urgent work. Here, a simple sensor N′‐(2,4‐dihydroxybenzylidene)naphtha[2,1‐b]furan‐2‐carbohydrazide (Q1‐3) was designed and synthesized for selective and sensitive dual‐channel detection of cyanide in aqueous medium (DMSO/H2O, 1:9, v/v). Acylhydrazone and phenolic hydroxyl groups on Q1‐3 are the recognition sites, and naphthofuran group is the signal report group. The intramolecular charge transfer between the benzene group and naphthofuran group was impeded because of the electron‐withdrawing groups (hydroxyl) on sensor Q1‐3. Interestingly, the sensor Q1‐3 exhibited an intramolecular charge transfer absorption band at 400 nm and emission band at 500 nm, respectively, directly realizing an “OFF–ON” response after the deprotonation process induced by cyanide anions in aqueous medium (DMSO/H2O, 1:9, v/v). Notably, this sensor was successfully applied to detect cyanide anions in food samples, which proves a very simple and selective platform for on‐site monitoring of cyanide in agriculture samples. In addition, the test strips and silica gel plates based on Q1‐3 were also fabricated, which could act as test kits and silica gel plates for convenient and efficient detection of cyanide anions.