Semicarbazide-based naphthalimide as a highly selective and sensitive colorimetric and “turn-on” fluorescent chemodosimeter for Cu2+

A semicarbazide-based naphthalimide was designed and synthesized as a colorimetric fluorescent probe. Upon reaction with Cu2+ in a buffer solution of pH 7.4 (buffer water/acetonitrile = 80:20, v/v), the probe exhibits color changes from colorless to jade-green accompanying remarkable enhancement in its fluorescence, which could be mechanistically ascribed to the Cu2+-promoted hydrolysis of the semicarbazide moiety leading to the release of the green fluorescent 4-amino-1,8-naphthalimide fluorophore. The probe also displayed excellent performance in high sensitivity as well as good selectivity for Cu2+ over other metallic cations.