Preparation, AIE and ESIPT behaviour, controllable solid-state fluorescence and application of Co²⁺ probe based on α-cyanostilbene

Abstract

A simple α-cyanostilbene-functioned salicylaldehyde-based Schiff-base probe, which exhibited outstanding “aggregation-induced emission and excited state intramolecular proton transfer (AIE + ESIPT)” emission in solution, aggregation and solid states, was synthesized in high yield of 87%. Its solid-states with different morphologies emitted different fluorescence after crystallization in EtOH/H2O (1/2, v/v) mixtures or pure EtOH solvent. Besides, it exhibited an obvious spectro-photometrical fluorescence quenching for highly selective sensing of Co2+ in THF/water system (ƒw = 60%, pH = 7.4), accompanied by an intense green fluorescence turn-off behavior under UV365nm illumination. The binding stochiometry between the ligand and Co2+ was found to be 2:1, and the detection limit (DL) was calculated to be 0.41 × 10-8 M. In addition, it could be applied to detect Co2+ in real water samples and on silica gel testing strip.