A selective and sensitive “naked-eye” rhodamine-based “turn-on” sensor for recognition of Hg2+ ion in aqueous solution

Abstract A selective and sensitive “naked-eye” rhodamine-based “turn-on” chemosensor for detection of Hg 2+ ion over other metal ions such as Ni 2+ , Ca 2+ , Ba 2+ , Cs + , Fe 3+ , Mn 2+ , Cd 2+ , Zn 2+ , Mg 2+ , K + , Ag + , Hg 2+ , Co 2+ , and Pb 2+ in aqueous solution was prepared. Meanwhile, a new method for the synthesis of rhodamine amide directly from rhodamine hydrazide in the presence of NaH was reported for the first time. It was observed that once Hg 2+ ion was added to the sensor 4 , a 91.4-fold enhancement of the absorption at 570 nm was observed. Its selectivity toward Hg 2+ ion was very high, and little interference was detected for other commonly coexistent metal ions. The fluorescent intensity was almost a constant minimal value when pH = 5–8 in aqueous solution. It demonstrated that Hg 2+ could be detected at least down to 3 × 10 −8  M. Moreover, the Hg 2+ -promoted selective desulfurization reaction was further confirmed by MS spectra. The present probe could be used to determine Hg 2+ ion concentrations in aqueous environments.