Mechanochemical Synthesis of a Fluorescein-Based Sensor for the Selective Detection and Removal of Hg2+ Ions in Industrial Effluents

Environmentally benign mechanochemistry-assisted high-yielding synthesis of fluorescein-phenylalaninol (FPA) conjugates as a Schiff base receptor is reported herein. This newly synthesized fluorescent probe is found to be most exciting and efficient because of its simultaneous detection and removal of mercury ions (Hg 2+ ) in aqueous medium and industrial effluents through precipitate formation. The receptor successfully worked as a chemosensor in selectively sensing the Hg 2+ ion through the rapid transition from yellow to pink in the colorimetric as well as quenching of fluorescence intensity in the fluorometric assay. The removal of mercury ions was confirmed by the inductively coupled plasma analysis of the supernatant. The lower detection limit of Hg 2+ ions for the receptor FPA is 1.65 and 0.34 μM as determined through absorption and fluorescence spectroscopic methods, respectively. The high removal efficiency (∼98%) of the mercury ions is promising and could be achieved via the formation of the complex in a 1:1 stoichiometric ratio of receptor to Hg 2+ ions. Furthermore, this probe may be a practical alternative for use in a paper-based portable device for achieving on-site detection of mercury ions in solid, solution, and vapor phases.