Phthalimide‐Based Off‐On‐Off Fluorosensor for Cascade Detection of Cyanide Ions and Picric Acid

Abstract Novel methods that can be utilized to identify and detect harmful environmental pollutants still need to be proposed. This article describes the effective design and development of a turn‐on photoluminescence probe, T1 [(E)‐5‐((2‐hydroxybenzylidene) amino) isoindoline‐1, 3‐dione], which is selective and sensitive towards CN − ions having detection limit nM to μM range. When exposed to CN − ions, Probe T1 displays a strong fluorescence response under a 365 nm UV light irradiation with a noticeable low to high intense cyan color photoluminescence visible to the naked eye. For the practical utility of the present probe T1 , a paper strips‐based test kit experiment has been demonstrated as a portable and displayable photonic device for on‐site detection of CN − ions. Furthermore, the T1‐ CN − adduct has been applied for detecting explosive nitroaromatic compounds, especially PA, based on the photoluminescence quenching mechanism. Using CN − ions, and PA as chemically encoded inputs and corresponding optical output, a molecular logic gate has been constructed. Further, probe T1 has been employed as a bio‐analytical tool to map intercellular CN − ions in live cells. This study invokes a novel approach for designing and developing efficient and selective sensors employing well‐known fluorescent probes as signaling units with prior photophysical knowledge.