A turn-off fluorescent probe for the detection of Cu2+ based on a tetraphenylethylene-functionalized salicylaldehyde Schiff-base

Abstract

A non-planar tetraphenylethylene-functionalized salicylaldehyde Schiff-base fluorescent probe (TPE-An-Py) with aggregation-induced enhanced emission (AIEE) characteristics was synthesized via a classical Knoevenagel condensation reaction, and exhibited a high sensitivity towards copper ions in aqueous media with a “turn-off” fluorescence mechanism; the limit of detection is 2.36 × 10⁻⁷ mol L⁻¹. Importantly, the coordination mode of the probe towards copper was further evaluated by UV-vis and NMR spectroscopy and a 1 : 2 stoichiometry was identified. A single crystal X-ray diffraction study confirmed the binding mode. In addition, the AIEE fluorescent probe can be applied to the detection of Cu²⁺ in practical samples with satisfactory recoveries in a range of 106–111% in lake water and 97–108% in tap water.