A dual-site controlled fluorescent sensor for the facile and fast detection of H2O in D2O by two turn-on emission signals.

Currently, fluorescent sensors for the detection of H2O in D2O are still quite rare. Herein, we present a dual-site controlled fluorescent sensor (CF-D2O) for the detection of H2O in D2O. As the H2O content in D2O decreases (namely, the purity of D2O increases), sensor CF-D2O provides two turn-on fluorescence signals. The response mechanism of sensor CF-D2O to H2O is based on the deprotonation of the two hydroxyl groups, as well as the FRET process between coumarin and xanthene units.