Fluorescence and colorimetric-based sensing of Hg2+ and Cu2+ using rhodamine derivative

Effective and simultaneous detection of multimetal ions has been achieved by a colorimetric and fluorometric sensor (RA), which was fabricated between rhodamine hydrazide and 9-anthraldehyde through a simple Schiff base reaction. Sensor RA provided an effective platform for reliable detection of Hg2+ with a detection limit as low as 9.978 x 10(-9) and displayed fabulous sensitivity for Cu2+ with a low limit of detection (LOD) of 4.81 x 10(-8) M of detection limit toward Cu2+. Among them, the detection limit for heavy metal mercury ions has reached the ultrasensitive level. The sensing mechanism between RA and metal ions was further confirmed by H-1 NMR and IR titration experiments and high-resolution mass spectrometry and discussed from a theoretic level based on crystal structures and density functional theory (DFT) calculations. The switch in turn-on signaling was attributed to the spiro-lactam and ring-opened form of RA and was accompanied by significant changes in ultraviolet spectroscopy and fluorescent spectrum.