Tough Porous Hydrogels for Ultrasensitive Naked-Eye and Fluorescence Dual-Mode Detection of Iron(III)

Abstract

Iron ions (Fe³⁺) play a crucial role in a variety of environmental, industrial, and biological processes. However, elevated concentrations of iron ions can lead to significant issues, such as environmental pollution, health risks, and accelerated material degradation, including metal corrosion. Therefore, the ability to rapidly and accurately detect Fe³⁺ ions at low concentrations is essential to ensure environmental safety, public health, and industrial stability. In this study, a series of tough luminescent porous hydrogels were fabricated through the cryogelation method by introducing 4′-(N-propenyl-4-pyridinio)-2,2′:6′,2″-terpyridine perchlorate (PPTP) into a hydrogel network featuring multihydrogen bonding. The obtained porous hydrogels exhibit not only outstanding fracture strength but also rapid highly sensitive detection of low concentrations of Fe³⁺ ions. Notably, the hydrogel sensors achieved a theoretical limit of detection (LOD) of 0.34 μM within just 10 s, which is acceptable within the limit of the Minister of Health of the People’s Republic of China. Additionally, a distinctive feature of this porous hydrogel is its ability to visually detect iron ion content through a color change from white to light green, providing a simple and effective method for real-time monitoring of early-stage stainless-steel corrosion. This combination of ease of fabrication, high sensitivity in fluorescence detection, colorimetric response, and convenient usage makes the P(MNAGA-co-HEMA-co-PPTP) hydrogel a highly effective fluorescent chemosensor for Fe³⁺ ions.