Chromogenic ‘Naked Eye’ and ‘Turn‐On’ Fluorescent Sensor for Detection of Al ³⁺ Ion Based on Naphthalene Carbohydrazide: Mimicking Logic Gate Applications

The naphthalene carbohydrazide colorimetric and fluorimetric chemosensor (E)‐N′‐(4‐(diethylamino)‐2‐hydroxybenzylidene)‐1‐naphthohydrazide (MKG‐12) was designed, synthesized and evaluated for cation sensing via excited state intermolecular proton transfer (ESIPT) mechanism. The chemosensor MKG‐12 shows a high sensitivity and selectivity to Al 3+ ion detection in 10% aq.‐DMSO solution (HEPES buffer, pH 7.4) with a 1:1 binding stoichiometry. The emission intensity of chemosensor MKG‐12 was selectively enhanced by Al 3+ ion, and an observable change in colour from colourless to fluorescent green was observed. Chemosensor MKG‐12 shows limit of detection 8.79 × 10 −8 μM and K abs = 1.32 10 4 M −1 and K em = 3.08 10 4 M −1 binding constant with Al 3+ ion. Further, the interaction between the chemosensor MKG‐12 and the Al 3+ ion was supported by mass spectroscopy and DFT. Additionally, the chemosensor MKG‐12 has been utilized as a small colorimetric kit for Al 3+ ion on paper test strips and is also accomplished for detection of Al 3+ ion in real water samples from different sources. Chemosensor MKG‐12 was constructed as INHIBIT logic gate based on reversibility behaviour with EDTA.