A dual-dimensional fluorescent sensor for uranyl (UO22+) in complex waters based on a Tb-MOF with intensity–lifetime dual readouts

Abstract

The concentration of uranyl ions (UO₂²⁺) is a key indicator for environmental surveillance and water-safety assessment after nuclear radiation incidents, yet its on-site, real-time, and reliable detection in complex waters with high salinity and strong interference remains challenging. Fluorescence-lifetime readout offers improved robustness and anti-interference capability over intensity-only sensing, but lifetime-responsive strategies for UO₂²⁺ are rarely reported. Herein, we present ZJU-168, an aqueous-stable metal–organic framework (MOF), enabling dual-readout sensing of UO₂²⁺ via fluorescence intensity and lifetime. ZJU-168 exhibits rapid luminescence quenching and a pronounced lifetime shortening upon exposure to UO₂²⁺, arising from a synergistic quenching mechanism involving inner filter effect (IFE) and photoinduced electron transfer (PET). As a result, ZJU-168 achieves ultrasensitive detection with a detection limit of 17 nM in pure water and 14 nM in seawater, both below the U.S. Environmental Protection Agency limit for uranium in drinking water (130 nM). Moreover, ZJU-168 immobilized on filter paper, coupled with smartphone RGB analysis, enables rapid, portable, and instrument-free on-site visual detection. Overall, this work provides a stable and field-deployable strategy for real-time monitoring of UO₂²⁺ in complex aquatic environments.