Smart Photonic Crystal Hydrogel Material for Uranyl Ion Monitoring and Removal in Water

Uranyl ion (UO 2 2+ ) pollution is a serious environmental problem, and developing novel adsorption materials is essential for UO 2 2+ monitoring and removal. Although some progress is achieved, it is still a challenging task to develop an adsorption material with indicating signal for real‐time evaluation of the adsorption degree and the UO 2 2+ concentration. Herein, this paper describes a smart photonic crystal hydrogel (PCH) material, which not only can be used for real‐time monitoring function but also can be utilized for UO 2 2+ removal based on the chelation of UO 2 2+ with ligand groups in PCH material. The working principle is based on the binding of a uranyl ion to multiple ligand groups, which results in the shrinkage of PCH material and triggers a blue‐shift of diffraction wavelength. Consequently, the adsorption degree and the UO 2 2+ concentration can be sensitively evaluated by measuring the diffraction shift or observing the color change with naked eye. With this PCH material, the lowest detectable concentration for UO 2 2+ is 10 × 10 −9 m , and the maximum adsorption capacity at 298 K is 169.67 mmol kg −1 . In addition, this material also holds good selectivity and regeneration feature, and shows desirable performance for UO 2 2+ analysis in real water samples.