2H-MoS₂/Co₃O₄ nanohybrid with type I nitroreductase-mimicking activity for the electrochemical assays of nitroaromatic compounds

A type I nitroreductase-mimicking nanocatalyst based on 2H-MoS₂/Co₃O₄ nanohybrids for trace nitroaromatic compounds detection is reported in this work. For the preparation of nanocatalyst, ultrathin Co₃O₄ nanoflakes array was in-situ grown onto 2H-MoS₂ nanosheets forming three-dimensional (3D) nanohybrid with large specific surface area as well as abundant active sites. The as-prepared nanocatalyst shows a specific affinity as well as high catalytic activity towards nitroaromatic compounds. Given the favorable nitroreductase-mimicking catalytic activity of 2H-MoS₂/Co₃O₄ nanohybrid, a sensitive and efficient electrochemical microsensor has been constructed for the detection of 2, 4, 6-trinitrotoluene (TNT). Under optimized conditions, the microsensor displayed sensitive response from μM to pM levels with a limit of detection (LOD) of 1 pM. We further employed photoelectron spectroscopy (XPS) analysis and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method to identify the nitroreductase-mimicking mechanism of 2H-MoS₂/Co₃O₄ nanohybrids towards 2, 4, 6- TNT. It was found that the abundant oxygen vacancies in ultrathin Co₃O₄ nanoflakes played an essential role in determining its catalytic performance. Moreover, the developed MoS₂/Co₃O₄ nanozyme has a lower Michaelis-Menten constant (k_m) than that of nature nitroreductase demonstrating a good enzymatic affinity towards its substrates, and further generating a high catalytic activity. This research not only proposed a new type of nanozyme, but also developed a portable electrochemical microsensor for the detection of 2, 4, 6-TNT.