A Turn-On Fluorescent Rhodamine-acyl Hydrazide for Selective Detection of Cu2+ Ions

We present a rhodamine-based probe that can detect Cu2+ ions via Cu2+-promoted hydrolysis in aqueous solutions. In solution, the probe is non-fluorescent and colorless, but gives a strong fluorescence at 586 nm and shows a color change to pink on the addition of Cu2+ ions. We demonstrate that the rhodamine-based probe undergoes Cu2+-promoted hydrolysis with a moderate reaction time (within 3 min) and provides a fluorescence off-on change, even in the presence of other competitive metal ions. The rhodamine-based probe shows a linear correlation between increasing fluorescence at 586 nm and the Cu2+ concentration, and can detect Cu2+ at nanomolar levels (10 nM) in CH3CN: H2O