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

Uranyl ion (UO22+) pollution is a serious environmental problem, and developing novel adsorption materials is essential for UO22+ 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 UO22+ 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 UO22+ removal based on the chelation of UO22+ 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 UO22+ 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 UO22+ is 10 x 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 UO22+ analysis in real water samples.