A cysteamine-functionalized biomimetic chromotropic hydrogel for naked-eye detection and adsorption of mercury ions

Mercury ions (Hg2+) are wreaking havoc on humans and the environment, and there is still an urgent need to develop a new method for the simultaneous detection and adsorption of Hg2+. Herein, inspired by chameleons, a cysteamine-functionalized biomimetic chromotropic hydrogel (Cys-BCH) capable of simultaneous naked-eye detection and adsorption of Hg2+ is ingeniously constructed. Benefiting from the specific recognition of Hg2+ by sulfhydryl groups on the hydrogel, the maximum adsorption capacity of the hydrogel is 0.3123 mmol g−1 at pH = 5. In addition, the adsorption kinetic model and isotherm are consistent with the pseudo-second-order and Langmuir models, respectively, indicating that the adsorption behavior is dominated by monolayer chemisorption. Furthermore, sensitive and selective detection of Hg2+ (the limit of detection (LOD) is 0.3 nM, 3σ) can be easily achieved by observing the color change of Cys-BCH with the naked eye or recording the change in the reflection peak position using a fiber spectrometer. More importantly, Cys-BCH has good regeneration performance and can be applied to detect Hg2+ in actual water samples.