Rhodamine 6G hydrazone with coumarin unit: a novel single-molecule multianalyte (Cu2+ and Hg2+) sensor at different pH value

A rhodamine derivative was synthesised via the hydrazone formation of rhodamine 6G hydrazide with 7-diethylamino-3-(1-hydroxy-3-oxobut-1-enyl)-2H-chromen-2-one. As a colourimetric and ratiometric fluorescent probe, the derivative exhibited high selectivity towards Cu2+ in neutral aqueous media. Moreover, the probe sensed Hg2+ with fluorescence enhancement at pH 10. The binding process was confirmed via UV-vis absorption, fluorescence measurements, 1H NMR, mass spectroscopy and density functional theory calculation. To validate the applicability of the probe, the probe was used to detect Cu2+ and Hg2+ ions in actual water samples. The application of the fluorescent sensor in monitoring intracellular Cu2+ in Hela cells has also been demonstrated.