A new polymerizable fluorescent PET chemosensor of fluoride (F−) based on naphthalimide–thiourea dye

A novel N-allyl-4-amino-substituted 1,8-naphthalimide dye, containing thiourea functional group with intense yellow-green fluorescence was successfully synthesized. Copolymerization was done with styrene. The photophysical characteristics of dye and its copolymer in solution and solid film were investigated in the presence of halide ions. The results reveal that the fluorescence emissions of the monomer dye and also its polymer were ‘switched off’ in the presence of fluoride ions. The dye showed spectral shifts and intensity changes in the presence of more fluoride ions which lead to detect certain fluoride concentrations of 10–150 mM at visible wavelengths. By adding the fluoride ions, green-yellow to purple color changes occurs and the green fluorescence emission quenches, all of which easily observed by naked eyes. These phenomena are essential for producing a dual responsive chemosensor for fluoride ions. The polymeric sensor, in the film state exhibited a fast response to the fluoride ions.

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► We synthesize a novel N-allyl-4-amino-1,8-naphthalimide dye containing thiourea functional group with intense yellow-green fluorescence which acts as anion site of sensor.
► We examine polymerizable characterization of the dye which is very important for construction of high usage reversible fluorescence polymerizable senor with high mechanical and chemical stability.
► On the addition of fluoride ion, obvious change of green-yellow to purple color and green-yellow-to-quench emission.
► Provides to construct a dual responsive chemosensors for fluoride ion.