Two highly sensitive and selective colorimetric "off-on" rhodamine-based fluorescent chemosensor for Hg(II) in aqueous media.

Two novel rhodamine derivatives were designed and synthesized. They were successfully characterized by HR-MS, (1)H NMR and (13)C NMR. They were found to exhibit a reversible colorimetric response and exhibit high selectivity and sensitivity for Hg(II) ion over other commonly coexistent metal ions. Their selectivity is excellent, and the detection of Hg(II) at ppb level is possible. The colorimetric and fluorescent response to Hg(II) can be conveniently detected even by the naked eye, which provides a facile method for visual detection of Hg(II).