ABSTRACT An intramolecular charge transfer (ICT) fluorescent sensor 1 using a dansyl moiety as the fluorophore and an azathia-crown ether as the receptor was designed, synthesized and characterized. The ions-selective signaling behaviors of the sensor 1 were investigated in CH 3 CN-H 2 O (1: 1, v/v) by fluorescence spectroscopy. It exhibited remarkable fluorescence quenching upon addition of Hg 2+, which was attributed to the 1: ...