A colorimetric probe for thiols was developed by using a cumarin-indandione conjugate based on the Michael addition of thiol to α

β-unsaturated double bond.The Michael addition of a thiol group to Michael acceptor of 1 blocked the intramolecular charge transfer(ICT) from the electronrich diethylaminocoumarin group to the electron-poor Michael acceptor

leading to a blue shift in the absorption spectra with an evident color change from blueviolet to colorless.The probe exhibited higher selectivity toward thiols(Cys

Hcy and GSH) than other amino acids.And the detection limit for Cys was 6.9×10-7 mol/L.