A covalent organic polymer fluorescent probe for highly selective and sensitive UO₂²⁺ detection in water and food...

A highly sensitive, selective, and simple method for detecting uranyl ions (UO₂²⁺) is crucial for human health and environmental safety. Amidoxime-based nanomaterials have been widely employed for UO₂²⁺ detection, but their higher affinity for vanadium than UO₂²⁺ limits their practical applications. Herein, a novel covalent organic polymer fluorescent probe (TT-COP) for UO₂²⁺ detection was innovatively developed by a one-step Schiff-base condensation reaction between 3,3',5,5'-tetramethylbenzidine (TMB) and 2,4,6-triformylphloroglucinol (Tp). TT-COP not only possesses excellent thermodynamic stability, hydrophilicity, synthetic reproducibility, and fluorescence stability but also achieves outstanding sensing performance, with its interaction with UO₂²⁺ reaching equilibrium within 5 min and a detection limit of 35.75 nM. Further investigations reveal that UO₂²⁺ coordinates with the imine and hydroxyl groups of TT-COP, thereby inhibiting the intramolecular charge transfer (ICT) process and leading to fluorescence quenching. Moreover, TT-COP exhibits extraordinary selectivity and biocompatibility, enabling reliable UO₂²⁺ quantification in complex matrices including environmental waters, food, and biological samples, with recovery rates ranging from 94.54 % to 106.43 %. The detection results closely align with those obtained from high-precision ICP-MS measurements. These findings underscore the promising practical applications of TT-COP in food safety, environmental monitoring, and human health assessment.