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

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 Cu2+ in mixed solvents (DMSO/H2O, v/v = 3:2), and uses a fluorescence burst mechanism to rapidly analyze Cu2+ ions in aqueous media with a detection limit as low as 3.98 × 10−8 M, which is well below the permissible standard for Cu2+ (∼20 µM) in drinking water (WHO). Importantly, the probe has been successfully applied to the determination of Cu2+ 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 Cu2+ ions under 365 nm UV light. In addition, the coordination pattern of the probe with Cu2+ was evaluated by mass spectrometry and working curves, and the stoichiometry of the probe and Cu2+ ions was determined to be 2:1. In addition, density functional theory (DFT) was performed to help understand the electronic nature of SY and Cu2+ complexation and chelation induced quenching mechanism.