A Novel AIE Plus ESIPT Fluorescent Probe with a Large Stokes Shift for Cysteine and Homocysteine: Application in Cell Imaging and Portable Kit

The application of fluorescent probes is limited due to the small Stokes shifts and aggregation-caused quenching (ACQ) effect when accumulated in cells. Herein, a novel colorimetric and turn-on fluorescent probe based on salicylaldehyde azine with both aggregation-induced emission (AIE) and excited-state intramolecular proton transfer (ESIPT) properties for Cys/Hcy is proposed to solve these issues. This probe showed a large Stokes shift (148 nm), low cytotoxicity as well as outstanding photostability upon recognition and the response mechanism was confirmed by fluorescence spectroscopy, High performance liquid chromatography (HPLC), thin layer chromotography (TLC), and transmission electron microscope (TEM). In addition to being used for cell imaging, a simple and user-friendly portable kit based on this probe was proposed as a new tool for the on-site inspection of more than ten microsamples simultaneously, which could effectively prevent the occurrence of false positives and visual errors.