Molybdenum Oxide Nanosheet-Supported Ferrous Ion Artificial Peroxidase for Visual Colorimetric Detection of Triacetone Triperoxide

The traditional nanozymes have low atom/ion utilization efficiency and are easily influenced by the size, morphology, as well as surface composition of nanomaterials. Herein, we report a template-free and valid approach to prepare a ferrous ion (Fe2+) anchored onto the surface of the MoO3 nanosheet (Fe2+/MoO3) through coordination interaction between Fe2+ and hydroxyl groups of MoO3. The resulting Fe2+/MoO3 shows the peroxidase-like activity, and it can be utilized for catalytic decomposition of hydrogen peroxide (H2O2) to generate hydroxyl radicals (•OH) that oxidize various chromogenic substrates, generating distinct color change and strong ultraviolet–visible absorption. The Fe2+/MoO3 peroxidase mimic exhibits a good thermal stability and works well at a high reaction temperature (95 °C) and has higher affinity for substrates than for natural horseradish peroxidase. Theoretical calculation results imply that the strong electrostatic field from the polarization charges between Fe2+ and the MoO3 nanosheet improves the reaction activity, which boosts the generation of •OH from H2O2. Using the Fe2+/MoO3 peroxidase mimic-involved chromogenic system, we construct visual colorimetric assays for H2O2 and triacetone triperoxide (TATP) explosives, which realize the visual detection of H2O2 and TATP at concentrations of 40 and 60 μM, respectively.