Fe/Ni Ratio Engineering Enhances the Colorimetric Detection of Glutathione by FeNi LDH Nanozymes

FeNi layered double hydroxides (LDHs) have attracted considerable interest as peroxidase-like nanozymes owing to their tunable bimetallic composition, abundant metal active sites, and structurally designable layered architectures. In this study, a series of FeNi LDH nanozymes with different Fe/Ni feeding ratios were constructed using MIL-88A as both a sacrificial template and an Fe source. The effects of Fe/Ni ratio on surface growth behavior, H 2 O 2 activation capability, and glutathione (GSH) colorimetric sensing performance were systematically investigated. The results show that the Fe/Ni ratio plays a critical role in regulating LDH growth on the MIL-88A-derived framework. With increasing Ni content, the surface morphology gradually evolves from particulate coverage to a nanosheet-dominated architecture. Among the prepared samples, FeNi 2 -LDH achieves an optimal balance among structural integrity, nanosheet uniformity, porous features, and accessible Fe-Ni synergistic sites, thereby exhibiting the highest peroxidase-like activity. Steady-state kinetic analysis and ESR measurements further reveal that FeNi 2 -LDH possesses favorable apparent affinity toward H2O2 and enhanced ·OH generation capability, which efficiently promotes TMB oxidation. Based on the FeNi 2 -LDH-TMB-H 2 O 2 chromogenic system, sensitive colorimetric detection of GSH was achieved with a linear range of 1-30 μM and a detection limit of 0.8 μM. This work provides a useful strategy for enhancing the catalytic performance of LDH-based nanozymes through bimetallic ratio engineering and offers a feasible platform for the colorimetric detection of reductive biomolecules.