A nanomolar detection of mercury(II) ion by a chemodosimetric rhodamine-based sensor in an aqueous medium: Potential applications in real water samples and as paper strips.

A new promising rhodamine based colorimetric and fluorometric chemosensor, RDV has been designed and synthesized for specific detection of Hg ion. It acts as highly selective "turn-on" fluorescent chemosensor for Hg ion without interference from other competitive metal ions in aqueous acetonitrile medium. The drastic color change with addition of Hg, from colorless to pink, indicates RDV can acts as "naked-eye" indicator for Hg. The Hg promoted selective hydrolysis of appended vinyl ether group in RDV followed by Hg chelated complex formation with concomitant opening of spirolactam ring is the plausible sensing mechanism. The detailed absorption, fluorescence, H NMR, C NMR and mass spectrometry confirms the proposed sensing mechanism. The limit of detection (LOD) of Hg by RDV is 136 nM indicating the high sensitivity towards Hg. The RDV shows consistent spectroscopic response in biological pH range 4-10. In addition to explore practical applicability of RDV, its paper strips have been made and used to detect Hg in pure water solution up to 10 ppm level. Furthermore, the potential application of RDV for the sensing of Hg in real water samples (tap water and drinking waters from different sources) were also monitored and demonstrated.