A simple fluorescent probe for detecting mercury(II) ion in aqueous solution and on agar gels

A novel coumarin-based nonsulfur probe, 7-(propargylamino)-4-methyl-2H-chromene-2-one (CNP), for selective detection of Hg2+ was synthesized by one-step substitution reaction. In the probe, alkyne was exploited as the specific recognition unit, which would be transformed into ketone in the presence of mercuric ion with a catalytic amount. The intramolecular charge-transfer (ICT) process was modulated and thus the fluorescence of CNP was quenched. The detection limit of mercury (II) was in the nanomolar range and the probe can be used to accurately quantify the ion spiked in river water specimens. Moreover, agar gels based on CNP were fabricated, which could be acted as a solid optical sensor to detect Hg2+ conveniently and efficiently.