A Indole-Trizole-Rhodamine Triad as Ratiometric Fluorescent Probe for Nanomolar-Concentration Level Hg(2+) Sensing with High Selectivity.

A new type of ratiometric fluorescent probe capable of detecting Hg(2+) ions at nanomolar-concentration level with high selectivity was developed based on an indole-trizole-rhodamine triad and its practicability for intracellular Hg(2+) sensing was verified. The as-prepared fluorescent probe is capable of detecting Hg(2+) over other competing metal ions including Ag(+) with high selectivity. The synergistic effect of Hg(2+)-assisted conversion of the nonfluorescent ring-closed rhodamine moiety to the highly fluorescent ring-open form as well as the fluorescence signal amplification originating from the Förster resonance energy transfer (FRET) from indole-trizole conjugate to rhodamine moiety contributed to a detection limit of 11 nM of the probe for Hg(2+) sensing.