Smartphone-assisted fluorescence/colorimetric dual-mode sensing strategy for uranium ion detection using cerium-sulfonyl calix[4]arene

A novel fluorescence/colorimetric dual-mode detection strategy for uranium ions (UO 2 2+ ) is presented based on a cerium-sulfonyl calix[4]arene (SC4A) platform. The exo- and endo-rim sites of SC4A can coordinate with Ce 3+ and Ce 4+ ions, respectively, quenching Ce 3+ fluorescence and influencing the oxidase-like activity of Ce 4+ . In the absence of UO 2 2+ , the solution of 3,3,5,5-tetramethylbenzidine (TMB) remains blue, but upon UO 2 2+ binding, Ce 3+ dissociates from SC4A, restoring fluorescence, while UO 2 2+ interacts with oxTMB, turning the solution from blue to colorless. This dual-mode system provides a linear fluorescence detection range of 30–800 nM with a detection limit of 20.20 nM, and a colorimetric range of 30–800 nM with a detection limit of 27.78 nM. By combining high-sensitivity fluorescence with visual colorimetric analysis, the proposed method possesses high sensitivity, accuracy, and reliability. Notably, smartphone-based color capture facilitates rapid and convenient sample analysis, enabling straightforward quantification at varying UO 2 2+ concentrations. The method has been successfully applied to real water and urine samples, demonstrating its practical utility in environmental and biological monitoring of UO 2 2+ . Graphical abstract