Integrated NIR-980-Sensitized UCNP and MoS ₂ Nanosheets for Sensitive Detection of Uranyl Ions

Uranium, a radioactive element, exists in aqueous environments primarily as uranyl ions (UO 2 2+ ), posing significant risks to human health and the environment. Detecting UO 2 2+ in such environments remains challenging. Here, an upconversion fluorescent sensor (UCDM) for the detection of UO 2 2+ in an aqueous environment was constructed based on the fluorescence resonance energy transfer (FRET) principle. This sensor utilizes upconversion nanoparticles loaded with DNAzyme (UCDA) as energy donors and molybdenum disulfide (MoS 2 ) as energy acceptors. MoS 2 exhibits a high affinity for single-stranded DNA (ssDNA), enabling the sensor to function effectively. In the presence of UO 2 2+, DNAzyme catalyzes substrate cleavage at the rA site, releasing ssDNA that binds to MoS 2 . This interaction leads to a decrease in UCDA upconversion luminescence. The unique upconversion luminescence property of an upconversion nanoparticle minimizes background autofluorescence, enhancing sensitivity. The sensor achieves a low detection limit of 5.81 nM and demonstrates robust recoveries (98.7%–102.7%) in complex aqueous matrices such as Xiangjiang water, uranium mine wastewater, human serum, and urine samples, underscoring its practical applicability.