Highly sensitive and selective turn-on fluorescent probes for Cu2+ based on rhodamine B.

A new rhodamine B-based fluorescent probe RL for Cu2+ has been designed, synthesized, and characterized. It exhibits a very high selectivity and sensitivity for the detection of Cu2+ in CH3CN : H2O = 1 : 9 (v/v) buffered with Britton-Robinson (pH = 7.02), the detection limit can reach 0.739 nM, which is the lowest reported. Furthermore, the probe RL can be made into test papers to detect the cupric ions in drinking water by the naked eye. RL can also be used for imaging Cu2+ in living cells and is almost non-toxic.