A hydrophilic naphthalimide-based fluorescence chemosensor forCu²⁺ ion: Sensing properties, cell imaging and...

In this work, a hydrophilic naphthalimide-based fluorescence chemosensor (sensor 1) was synthesized for Cu²⁺ recognition, in which 2-(2-aminoethoxy)ethanol was introduced to improve the hydrophily and Schiff base acted as the multidentate ligand for Cu²⁺. The effect factors, sensing mechanism and regenerability of sensor 1 for Cu²⁺ sensing were systematically investigated. It was found that sensor 1 displayed a long emission wavelength of 532 nm upon excited in visible light region (436 nm), and the good water solubility made it utilized in aqueous media. It could selectively react with Cu²⁺ over other common metal ions to form a 2:1 complex within 1 min and result in significant fluorescence quench. The fluorescence change was linear to 0.5-10.0 μmol L^-1 of Cu²⁺ with a low detection limit of 3.74 × 10^-8 mol L^-1. Sensor 1 has been successfully utilized for analyzing Cu²⁺ in water samples as well as imaging cellular Cu²⁺. Moreover, in view of fluorescence "on-off-on" switches of sensor 1 induced by Cu²⁺ and EDTA, an IMPLICATION logic gate was constructed based on fluorescence mode with Cu²⁺ and EDTA as inputs.