A chromatic-switching Fe₂Nb₂O₇ pyrochlore cage nanozyme for robust peroxidase-mimetic activity and selective hydrogen...

Hydrogen peroxide (H₂O₂) is a reactive oxygen species (ROS) that plays a role in various physiological processes, with abnormal levels linked to multiple diseases. Nanozymes, which are praised for their easy synthesis, stability, cost-effectiveness, and recyclability, are gaining interest for applications in cancer treatment, disease diagnosis, and molecular sensing. However, their limited catalytic activity and lack of multifunctionality restrict their sensitivity and broader applicability. Therefore, developing highly active, multipurpose nanozymes is essential for enhancing their utilization across various fields. In this work, a novel pyrochlore Fe₂Nb₂O₇ was synthesized through the co-precipitation method with a controlled combination of iron oxide and niobium oxide for H₂O₂ detection. Fe₂Nb₂O₇ pyrochlore exhibited a prominent absorption peak at 645 nm in the UV-vis spectrum. Novel pyrochlore Fe₂Nb₂O₇ exhibits strong repeatability, high selectivity, excellent stability, and reasonable reproducibility in H₂O₂ detection. Its notable peroxidase-like activity allows for the catalytic breakdown of H₂O₂, generating ˙OH radicals that oxidize colorless 3,3°,5,5°-tetramethylbenzidine (TMB) into its blue oxidized form. Its outstanding sensing capabilities are attributed to a large specific surface area, strong electrical conductivity, numerous active sites, distinctive structural features and the synergistic interaction between Fe₂O₃ and Nb₂O₅. It facilitated a rapid colorimetric assay with a detection limit of 0.62 µM and a linear range of 01-100 µM. The sensor has also been successfully applied to the detection of H₂O₂ in normal human serum. In summary, this study offers a cost-effective, sensitive and visually appealing H₂O₂ detection technology with a broad range of potential uses.