Fluorescence turn-on detection of cysteine over homocysteine and glutathione based on ESIPT and AIE

4-Chloro-2-(((2-hydroxybenzylidene)hydrazono)methyl) phenol (1) was reported to exhibit typical aggregation-induced emission (AIE) characteristics in our previous work. Here we introduce an acryloyl group onto the hydroxyl moiety of 1 and develop 2 (4-chloro-2-(((2-hydroxybenzylidene)hydrazono)methyl) phenyl acrylate) for fluorescence turn-on detection of cysteine (Cys). H-1-NMR and mass spectrometry data of the products revealed that the reaction between 2 and Cys resulted in the formation of 1 with excited-state intramolecular proton transfer (ESIPT) and AIE properties. With fluorescence enhancement detection by 2, the linear range and detection limit for Cys were obtained to be 0-30 mu M (R-2 = 0.998) and 0.46 mu M respectively with satisfactory selectivity over homocysteine (GSH), glutathione (Hcy) and other amino acids. The method was also used for Cys detection in a serum sample.