An AIE-active “turn-off” fluorescent sensor for highly selective and sensitive detection of Cu2+ions

Developing highly selective and sensitive sensor for Cu2+ ions is very important in the fields of chemical, biological and environmental. Herein, a novel Cu2+ions sensor based on tetraphenylethylene (TPE) derivative with aggregation-induced emission (AIE) property was designed and synthesized. It was prepared by introducing four Cu2+ ion chelating centers onto TPE core, which exhibited a sensitive fluorescent "turn-off" behaviour and highly selective responses to Cu2+ions in the present of various interferential cations. It also showed a visible colour change from bright yellow to colourless at the addition moment of Cu2+ions. The responses mechanism was revealed by 1H NMR spectrum, dynamic light scattering (DLS) analysis and density functional theory (DFT) calculation. The results showed that the coordination of the sensor's N, O atoms with Cu2+ions induced the TPE-Schiff base's structure planarization, and formed a very tight Cu2+ complex in nano-size aggregation state, which led to the fluorescent emission " turn-off ". This study provides a valuable approach to design and prepare AIE-active fluorescent sensor for the detection of Cu2+ ions.