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 (UO22+), posing significant risks to human health and the environment. Detecting UO22+ in such environments remains challenging. Here, an upconversion fluorescent sensor (UCDM) for the detection of UO22+ 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 (MoS2) as energy acceptors. MoS2 exhibits a high affinity for single-stranded DNA (ssDNA), enabling the sensor to function effectively. In the presence of UO22+, DNAzyme catalyzes substrate cleavage at the rA site, releasing ssDNA that binds to MoS2. 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.