Reusable Sensory Hydrogel Membrane for Smart Detection and Efficient Capture of Cesium from Brine

ABSTRACT With rising global cesium (Cs) demand and energy‐intensive ore processing, extraction from salt lakes and brines offers a sustainable alternative. However, selective Cs recovery remains challenging due to extremely low concentrations amid competing ions. Here, we report DTA, a novel anthraquinone‐based fluorophore functionalized with dithiothreitol as a cesium‐selective chelator. DTA exhibits distinctive turn‐on green fluorescence specific to Cs + ions, maintaining high selectivity against oceanic interferents (Mg 2 + , Na + , K + ) in aqueous media with an ultralow detection limit of 2.9 n M . DFT calculations confirm that Cs + binding disrupts hydrogen‐bond‐assisted photoinduced electron transfer (PET), restoring anthraquinone's intrinsic fluorescence. Incorporating DTA into hydrogel matrices yields high‐performance membranes for cesium extraction. The optimized DTAH4 membrane demonstrates 1.8‐fold enhanced water permeability (525.2 L·m − 2 ·h − 1 ·bar − 1 ) compared to pristine DTAH0, while achieving a remarkable 97% Cs extraction efficiency versus only 11% for the control. Importantly, we demonstrate smartphone‐based visual RGB detection, enabling portable, real‐time monitoring of cesium contamination. This integrated approach, combining ultrasensitive fluorescent detection with efficient membrane separation, presents a practical platform for sustainable cesium recovery for technological applications.