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

A selective and sensitive naked-eye rhodamine-based turn-on chemosensor for detection of Hg2+ ion over other metal ions such as Ni2+, Ca2+, Ba2+, Cs+, Fe3+, Mn2+, Cd2+, Zn2+, Mg2+, K+, Ag+, Hg2+, Co2+, and Pb2+ 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 Hg2+ ion was added to the sensor 4, a 91.4-fold enhancement of the absorption at 570 nm was observed. Its selectivity toward Hg2+ 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 Hg2+ could be detected at least down to 3 x 10(-8) M. Moreover, the Hg2+-promoted selective desulfurization reaction was further confirmed by MS spectra. The present probe could be used to determine Hg2+ ion concentrations in aqueous environments. (C) 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.