First fluorescence sensor for simultaneous detecting four rare earth metal elements (Y³⁺, Yb³⁺, Sc³⁺ and Ce³⁺)

This paper reports the first fluorescent sensor that can simultaneously detect multiple rare earth metal ions (Y³⁺, Yb³⁺, Sc³⁺ and Ce³⁺) in a variety of rare earth metal ions. The Schiff base TPE-A was synthesized in 85% yield by the condensation reaction of formyltetrastyrene with 4-aminoantipyrine. Long wavelength fluorescence of TPE-A was observed at 500-650 nm in both MeOH and MeCN solutions. In methanol, it showed a highly selective response to Y³⁺ with a fluorescence color change from red to yellow-green, while it exhibited fluorescence quenching for Yb³⁺. Additionally, it exhibited a selective sensing ability for Sc³⁺ in MeCN solution with a fluorescence color change from red to yellow, and a fluorescence quenching effect for Ce³⁺. In addition, it can detect these four rare earth metal ions simultaneously by fluorescence changes with the assistance of EDTA-2Na. It can be used as a fluorescence sensor for MeOH (Y³⁺ and Yb³⁺) and MeCN (Sc³⁺ and Ce³⁺), respectively. The ICT effect of the TPE-A probe on Y³⁺ was investigated using femtosecond transient absorption spectroscopy and quantum chemical calculations. The detection limits of Y³⁺, Yb³⁺, Sc³⁺ and Ce³⁺ were 1.6 × 10^-8 mol/L, 1.04 × 10^-7 mol/L, 8.35 × 10^-8 mol/L and 1.31 × 10^-8 mol/L, respectively, as deduced from Job's plots, spectral titrations, and ESI-MS. And the detection of measured water in MeCN was realized by TPE-A-Sc³⁺ hybrid system. This implies an efficient and simple method for the simultaneous analysis of trace rare earth metal elements (Y³⁺, Yb³⁺, Sc³⁺ and Ce³⁺) in complex environments.