A dual-responsive and highly sensitive fluorescent probe for Cu2+ and pH based on a dansyl derivative

Herein, a dansyl-based fluorescent probe bearing a glycylglycine group (GG-Dns) is reported. The probe demonstrates suitable selectivity and sensitivity towards Cu2+ in aqueous media over a wide pH range (6-13) through a fluorescence "turn-off' mechanism. The determined detection limit is 0.29 mu M (Cu2+ concentration), and the association constant is 3.09 x 10(4) M-1, with 1:1 coordinate stoichiometric ratio. The probe displays an appropriate detection performance for Cu2+ in real drinking water samples, indicating the potential applicability of GG-Dns even in complex environments. Furthermore, in aqueous environments with pH below 6, GG-Dns is sensitive toward pH changes within a narrow range and with a fluorescence "on-off' function. The sensitive detection characteristics of Cu2+ can be ascribed to the coordination performance of GG moiety to Cu2+, whereas pH responsiveness is ascribed to the protonation of Dns moiety's dimethylamine group.