Tough Porous Hydrogels\nfor Ultrasensitive Naked-Eye\nand Fluorescence Dual-Mode Detection of Iron(III)

Iron\nions (Fe<sup>3+</sup>) play a crucial role in a\nvariety of\nenvironmental, industrial, and biological processes. However, elevated\nconcentrations of iron ions can lead to significant issues, such as\nenvironmental pollution, health risks, and accelerated material degradation,\nincluding metal corrosion. Therefore, the ability to rapidly and accurately\ndetect Fe<sup>3+</sup> ions at low concentrations is essential to\nensure environmental safety, public health, and industrial stability.\nIn this study, a series of tough luminescent porous hydrogels were\nfabricated through the cryogelation method by introducing 4′-(<i>N</i>-propenyl-4-pyridinio)-2,2′:6′,2″-terpyridine\nperchlorate (PPTP) into a hydrogel network featuring multihydrogen\nbonding. The obtained porous hydrogels exhibit not only outstanding\nfracture strength but also rapid highly sensitive detection of low\nconcentrations of Fe<sup>3+</sup> ions. Notably, the hydrogel sensors\nachieved a theoretical limit of detection (LOD) of 0.34 μM within\njust 10 s, which is acceptable within the limit of the Minister of\nHealth of the People’s Republic of China. Additionally, a distinctive\nfeature of this porous hydrogel is its ability to visually detect\niron ion content through a color change from white to light green,\nproviding a simple and effective method for real-time monitoring of\nearly-stage stainless-steel corrosion. This combination of ease of\nfabrication, high sensitivity in fluorescence detection, colorimetric\nresponse, and convenient usage makes the P(MNAGA-<i>co</i>-HEMA-<i>co</i>-PPTP) hydrogel a highly effective fluorescent\nchemosensor for Fe<sup>3+</sup> ions.