An integrated system of pyrene and rhodamine-6G for selective colorimetric and fluorometric sensing of mercury(II)

A pyrene and rhodamine-6G functionalized simple chemosensor L is studied toward sensing of metal ions in solution extensively. L shows selective color change from colorless to pink in the presence of Hg2+ in acetonitrile and the UV–Vis study shows peak at 525 nm with a ε value of 5.2 × 104 M−1 cm−1 due to selective ring opening of rhodamine spirolactam moiety. The selective sensing of Hg2+ by L in the presence of other metal ions and reversible nature of “OFF–ON–OFF” functionality of L by Hg2+ and EDTA, respectively, are also established. The fluorescence study of L in the presence of Hg2+ shows emission at 550 nm when excited at 525 nm (ring opened rhodamine wavelength) or 340 nm (pyrene wavelength) in dry CH3CN. Thus L acts as a selective colorimetric and fluorometric probe (dual probe) for the Hg2+ in solution. Metal ion sensing ability of L is also carried out in water as well as in aqueous Hepes buffer. These studies suggest that the fluorescence output of L in presence of Hg2+ in aqueous environment is apparently due to the generation of acid upon addition of Hg2+ salt in water.