A turn-off fluorescent probe for the detection of copper(II) ion based on a salicylaldehyde derivatives Schiff-base

• Schiff base fluorescent probes with “turn-off” fluorescence mechanism can effectively detect Cu 2+ ions. • Probe SY is a fluorescent probe with aggregation induced emission (AIE) characteristics. • Probe SY recognizes Cu 2+ selectively in aqueous solution. • Probe SY can applied to detect Cu 2+ in tap water samples. • Probe SY has been good reversibility and recoveries. A highly selective Schiff-type fluorescent probe (SY) with aggregation-induced emission (AIE) characteristics was synthesized based on salicylaldehyde derivatives. With increasing water content, it exhibits good sensitivity and interference resistance for the detection of Cu 2+ in mixed solvents (DMSO/H 2 O, v/ v = 3:2), and uses a fluorescence burst mechanism to rapidly analyze Cu 2+ ions in aqueous media with a detection limit as low as 3.98 × 10 −8 M, which is well below the permissible standard for Cu 2+ (∼20 µM) in drinking water (WHO). Importantly, the probe has been successfully applied to the determination of Cu 2+ in real water samples with good reversibility and recoveries ranging from 99.3% to 106.6% in tap water, and can also be used for the detection of Cu 2+ ions under 365 nm UV light. In addition, the coordination pattern of the probe with Cu 2+ was evaluated by mass spectrometry and working curves, and the stoichiometry of the probe and Cu 2+ ions was determined to be 2:1. In addition, density functional theory (DFT) was performed to help understand the electronic nature of SY and Cu 2+ complexation and chelation induced quenching mechanism. A Schiff-type fluorescent probe (SY) was synthesized based on salicylaldehyde derivatives. It exhibits good selectivity and sensitivity to Cu 2+ ions in mixtures of solvents (DMSO/H 2 O, v/v = 3:2) and has a “off” fluorescence mechanism. The detection limit was 3.98 × 10 −8 M −1 . Importantly, the coordination pattern of the probe to Cu 2+ ions was evaluated by mass spectrometry and working curve, as well as DFT calculation, the stoichiometry of the probe and Cu 2+ ions was determined to be 2:1. Additionally, the fluorescent probe may be utilized to detect Cu 2+ ions in real water samples.