Dual luminescent lanthanide coordination polymers for ratiometric sensing and efficient removal of Hg2+

Abstract

In this work, we report a new fluorescence ratiometric method for Hg²⁺ assay based on the dual-ligand fluorescent probe GMP–Tb–luminol coordination polymers (CPs), which can be excited at the same wavelength and reveal characteristic luminescence of Tb³⁺ and luminol with spectrally distinguishable emission peaks. The addition of Hg²⁺ leads to the decrease of Tb³⁺ luminescence due to the higher coordination between Hg²⁺ and GMP, which inhibits energy transfer from GMP to Tb³⁺. Meanwhile, the fluorescence of luminol increases because of the aggregation-induced emission phenomenon. Therefore, a ratiometric fluorescent sensor for Hg²⁺ assay can be constructed by measuring the ratio of fluorescence intensity of luminol at 430 nm (I₄₃₀) to that of Tb³⁺ at 548 nm (I₅₄₈). Under the optimal conditions, the fluorescence intensity ratio I₄₃₀/I₅₄₈ exhibits a good linear relationship versus the concentration of Hg²⁺ in the range from 5 nM to 130 μM with a low detection limit of 1.3 nM. Additionally, the probe can also adsorb Hg²⁺ in water with high efficiency, which makes Hg²⁺ removal in water possible. The proposed method has been successfully used for the determination of Hg²⁺ in tap water, indicating its potential applications in the detection of Hg²⁺ pollution in environmental water.