A luminescent lanthanide functionalized hydrogen-bonded organic framework hydrogel: Fluorescence sensing platform for copper and iron ions detection

The excessive presence of the metal ions Cu 2+ and Fe 3+ in the environment poses a serious threat to ecosystems and human health, so timely and accurate detection of them has become essential and urgent. In this paper, a novel hydrogel-based fluorescent sensor, named ME-IPA@SA-TbZn, was fabricated facilely through an in-situ cross-linking modification method and was used for the detection of Cu 2+ and Fe 3+ in water bodies. The ME-IPA@SA-TbZn is essentially a hybrid hydrogel bead that exhibits vibrant fluorescence, employing Tb and Zn functionalized hydrogen-bonded organic frameworks (HOFs) as the fluorescence functional core and sodium alginate (SA) as the hydrogel matrix. The synthesized hydrogel sensor ME-IPA@SA-TbZn exhibits remarkable capabilities in detecting and distinguishing between Cu 2+ and Fe 3+ with high selectivity and sensitivity. Specifically, it achieves limits of detection (LODs) of 1.275 μM for Cu 2+ and 0.549 μM for Fe 3+ , respectively, both are below the maximum allowable concentrations set by the U.S. Environmental Protection Agency (EPA) for drinking water . Importantly, the hydrogel sensing platform delivers intuitive and visible results under simple operating conditions, and has been successfully applied to Cu 2+ and Fe 3+ detection in river samples. In addition, it was demonstrated that disruption of the “antenna” effect, absorption competition quenching (ACQ) effect, and ion exchange (IE) effect are the main mechanisms leading to fluorescence quenching . Based on these results, ME-IPA@SA-TbZn hold promise as a fluorescent sensor for detecting Cu 2+ and Fe 3+ ions. • A Tb@HOFs-based fluorescent hydrogel sensor was developed for metal ion detection. • The sensor exhibits a high selectivity for Cu 2+ and Fe 3+ over other metal ions . • Low detection limits of 1.275 μM and 0.549 μM and wide linear ranges were achieved. • The mechanism was explored, including ACQ, IE, and disruption of “antenna” effect.