Uranium contamination in water poses a serious challenge because uranyl ions, the most stable form of uranium in many aquatic environments, combine chemical toxicity, radioactivity, and high mobility. Researchers have now developed a fluorescent sensing platform that can detect these ions at very low concentrations while producing a color change that can be analyzed with a smartphone. The study was published in Sustainable Carbon Materials.
The new sensor, called EuZn-PMA, combines europium and zinc within a metal-organic coordination polymer. The two metals perform different but complementary roles: europium acts as the fluorescence signaling center, while zinc helps regulate the material's structure and strengthens its luminescence. Pyromellitic acid, or PMA, serves as the organic ligand and provides sites that can recognize uranyl ions.
"Our goal was to create a sensing system that is not only highly sensitive but also produces an intuitive optical signal that can be interpreted without relying on sophisticated laboratory instruments," said corresponding author Suhua Wang of Guangdong University of Petrochemical Technology. "The red-to-green fluorescence transition provides a straightforward way to visualize changes in uranyl concentration and creates opportunities for portable environmental monitoring."
When the probe is illuminated, PMA normally transfers absorbed energy to europium ions, producing a characteristic red fluorescence at 616 nanometers. When uranyl ions are introduced, however, they preferentially bind to carboxylate groups in PMA. This interaction disrupts the energy transfer to europium and weakens the red emission. At the same time, ligand-to-metal charge transfer associated with the uranyl complex generates a new green fluorescence signal at 513 nanometers. The combination produces a clearly visible shift from red toward green as uranyl concentration increases.
Because the method measures the relationship between two fluorescence signals rather than relying on a single intensity value, it provides ratiometric detection with built-in self-calibration, helping reduce errors caused by changes in probe concentration, excitation intensity, or environmental conditions.
In laboratory measurements, EuZn-PMA achieved a detection limit of 51 nanomolar and a linear detection range from 0 to 60 micromolar. The researchers also tested common ions that could interfere with uranium sensing and found that the probe maintained favorable selectivity and anti-interference performance.
Importantly, the team evaluated the sensor using lake water and seawater spiked with known concentrations of uranyl ions. Recoveries ranged from 94.5% to 102.5%, with relative standard deviations between 1.9% and 3.9%, indicating promising accuracy in these tested environmental samples. The study notes, however, that more complex mixtures of interfering substances were not fully simulated and should be investigated in future practical applications.
To make the system more suitable for field use, the researchers photographed the fluorescent samples under UV excitation and analyzed their red, green, and blue values using a smartphone-based platform. The green-to-red intensity ratio showed a strong relationship with uranyl concentration, allowing the color change to serve as a portable quantitative readout.
The researchers say the dual-metal strategy could provide a broader framework for designing lanthanide-based fluorescent sensors for environmental contaminants.
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Journal reference: Yuan Z, He C, Liu Z, Qiu H, Zheng Q, et al. 2026. Dual-metal synergistic coordination enables ultrasensitive and ratiometric multicolor fluorescent detection of uranyl ions. Sustainable Carbon Materials 2: e030 doi: 10.48130/scm-0026-0025
https://www.maxapress.com/article/doi/10.48130/scm-0026-0025
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About Sustainable Carbon Materials :
Sustainable Carbon Materials (e-ISSN 3070-3557) is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.
