Atomically dispersed Eu(III) sites in natural deep eutectic solvents based fluorescent probe efficient identification...

Heavy metal ions in wastewater have brought serious environmental pollution. To improve the detection efficiency, it is important to find useful fluorescent probes. The emerging green natural deep eutectic solvents (NADESs) offer attractive option for "green" detection for its good biocompatibility, easy preparation, and high sensitivity. In this study, a multi-functionalized fluorescent probe with atomically dispersed EuCl₃·6H₂O in amino acid-based NADESs (l-Glutamic acid/Glycerol, l-Glu/Gly) was synthesized by metal-ligand coordination interactions with a mass ratio of 15:1. Combined with the NADESs and rare earth metal, the l-Glu/Gly/EuCl₃·6H₂O could form the amino site and Eu²⁺ site fluorescent centers. Under the excitation wavelength of 370 nm, it had dual emission peaks at 425 nm and 470 nm with efficient resonance energy transfer. The stable optoelectronic properties of l-Glu/Gly/EuCl₃·6H₂O under external factors, such as mass ratio (13,1 to 18:1), temperature (30-50 °C), pH (1 to 14) and storage time ( >42 days), approved l-Glu/Gly/EuCl₃·6H₂O an excellent fluorescence probe. In the application of water-quality monitoring, Fe³⁺ and Cu²⁺ could react with l-Glu/Gly/EuCl₃·6H₂O in different reactive patterns. The blue fluorescence was quenched by Fe³⁺ and enhanced by Cu²⁺, thus metal ions could be distinguished with high sensitivity. The detective process was determined and the fluorescent mechanism was also proposed. l-Glu/Gly/EuCl₃·6H₂O fluorescent probe was demonstrated to be an efficient fluorescent probe for metal detection avoiding the hydrothermal process, and the cumbersome of ilter, dialysis, freeze drying.