A novel rhodamine-based optical probe for mercury(II) ion in aqueous medium: A nanomolar detection, wide pH range and real water sample application.

Abstract

In present work, we designed and synthesized new chemosensor RPy, containing the rhodamine and 2,6-pyridinedicarboxaldehyde functionality, for the selective detection of mercury (II) (Hg2+) ion in aqueous DMSO solvents. The RPy acts as "turn ON" probe for Hg2+ ion with high selectivity and sensitivity over the series of other competing metal ions based on colorimetric and fluorimetric techniques. Due to the incorporation of two rhodamine moieties enhance the chelation sites for mercury binding, which reflects in the lowering of the detection limit up to 26 nM. The Job plot method confirms the 1:2 stoichiometric interactions between the RPy and Hg2+ ion. The formation of the chelation complex between RPy and Hg2+ ion with spirolactam ring opening was thoroughly investigated by absorption, emission, 1H NMR, and mass analysis. The detection of Hg2+ ion by RPy is retained at broad pH range 4-9. Further, the probe RPy is successfully explored to measure the contamination of Hg2+ ion in the real water samples using spike and recovery method.