New rhodamine-based turn-on and colorimetric probe for copper(II) ion with high selectivity and sensitivity

A new rhodamine-based derivative fluorescent probe (L) was synthesized as a highly selective and turn-on fluorescent probe for quantitative detection of Cu2+ exhibiting an almost 200-fold fluorescence increase. Moreover, the X-ray single crystal structure of the probe had also been measured. Besides, the fluorescent probe can also be considered as a good OFF–ON switch for Cu2+ with naked-eye colour change from colorless to pink. The 1:1 binding ratio between chemosensor L and Cu2+ was investigated using Job’s plot method, 1H NMR titration and ESI-MS. The probe exhibited excellent selectivity and sensitivity toward Cu2+ with little interference, meanwhile the detection limit of Cu2+ was at a quite lower micromolar level.