Dual Naked-Eye Optical Sensor Based on Imidazolium Cation and Napthalamide for Specific Detection of Fluoride

A novel naked eye fluorescence sensor (ANI) based on naphthalimide and imidazolium moieties for fluoride detection has been designed and synthesized by multiple step synthesis. The fluorescence response of ANI sensor was significantly quenched in the presence of fluoride ion upon the interaction between an acidic amide proton and acidic C2 proton (-C(2)H-) of imidazolium compound. The binding behavior of ANI and F- ion was extensively explored by using NMR titration. Comparison of binding ability of ANI and AN sensors addressed the dominant electrostatic and hydrogen bonding interaction with F- ion. Consequently, ANI sensor highlights a strong binding with F- ions with a high selectivity over AN. Interestingly, ANI demonstrated a naked-eye response with colorimetric and fluorometric assay.