Development of COF-MF-based fluorescent sensor for on-site, and portable detection of uranium in ore samples

The radioactive uranium element associated with rare earth minerals poses a significant threat to human health. Current detection of uranium relies on analysis in the lab, which cannot meet the demand for rapid on-site detection. We have developed a porphyrin-based covalent organic framework material, COF-MF, which exhibited specific fluorescent response to uranyl ion (UO22+). Based on the combination of the imino group of the hydrazone with the hexavalent uranium on the skeleton, it blocked intramolecular charge transfer, leading to fluorescence quenching, without interference from other coexisting metal cations. The fluorescence intensity of COF-MF at 680 nm gradually decreased with UO22+ concentrations ranging from 0.1 nM to 4.0 mm, and a linear relationship was observed in the concentration range from 0.1 nM to 10 nM. By integrating 3D printing technology, we developed a portable, rapid on-site detection device combined with smartphone-based app detection software. The response curve of UO22+ from 0.1 nM to 4.0 mm was studied, and the detection limit of the device for UO22+ was 0.05 nM, which was lower than the natural radioactivity limit value of non-ferrous metal mineral products. The analysis results of uranium in standard material (GWB04122) were consistent with ICP-MS. This study can be used for rapid on-site screening of uranium in imported ores by customs, providing important technical support for the quality control of imported ores.