A naphthalimide-based highly selective colorimetric and ratiometric fluorescent probe for the fluoride ion displayed both one-and two-photon ratiometric changes. Upon reaction with the F−(TBA+ and Na+ salts) anion in CH3CN as well as in aqueous buffer solution, probe 1 shows dramatic color changes from colorless to jade-green and remarkable ratiometric fluorescence enhancements signals. These properties are mechanistically ascribed to a ...