Portable ratiometric fluorescence sensor based on CuNCs@EuMOFs for visual detection of Hg(<scp>ii</scp>) in water samples

Mercury ions (Hg²⁺) are highly toxic and bioaccumulative, posing a serious threat to the environment and human health. Traditional analytical techniques are limited by cost, portability and real-time monitoring capabilities, and there is an urgent need for sensitive and portable detection methods. In this study, copper nanoclusters (CuNCs) were encapsulated in red-emitting europium metal-organic frameworks (Eu-MOFs), and a ratiometric fluorescence probe based on CuNCs@EuMOFs was constructed and used for the detection of Hg²⁺ in water extracts of traditional Chinese medicine samples and river samples. In the presence of Hg²⁺, the fluorescence of this probe is enhanced at 450 nm and weakened at 618 nm. Visual quantification can be performed using a smart phone based on the color change. The linear range is 0-360 μM (<i>R</i> ² = 0.9986), and the detection limit is 0.94 nM. The sample recovery rate was 94.43-106.43% (RSD < 4.37%). This study provides a new strategy for the portable visual detection of Hg²⁺ in complex matrices.