An efficient fluorescein-based fluorescent chemosensor for quick detection of Cu2+, Zn2+ and Ni2+ ions

A multi-metal colorimetric and fluorescent probe derived from 5-diethylamino salicylaldehyde and fluoresceinamine was synthesized, characterized and examined for metal ion sensing. In this probe, salicylaldehyde-derived Schiff base subunit provides an "O–N–N" coordination site for metal ion sensing, whereas fluoresceine is functioned as fluorogenic unit. The reported fluorescent probe showed fluorescence "turn-on" in response to metal ions in aqueous media with significant color changes from colorless to light green, yellow green and bright yellow upon binding with Cu²⁺, Ni²⁺ and Zn²⁺ ions, respectively. The synthesized probe simultaneously recognized these metal ions and distinguished by absorption and emission responses with detection limit of 0.25 nM for Cu²⁺, 7.76 nM for Ni²⁺ and 38.22 nM for Zn²⁺ in HEPES buffer-methanol (2:1, v/v) solvent mixture.