MXene Quantum Dot-Modified Flower-Like FeOOH for Dual-Mode Nitrite Sensing

Nowadays, the rational design of high-performance simulated nanozymes applied to environmental detection has become a current research hotspot. Herein, we employ a urea/ethanol solution synergistic-mediated approach to prepare MQDs@FeOOH nanozymes with significant peroxidase activity. The steady-state fluorescence analysis and density-functional theory calculations (DFT) investigated that the MQDs@FeOOH nanozymes possess remarkable catalytic activity. This is attributed to the active sites of the Fe-Ti dimer, which effectively adsorb H₂O₂ and activate its decomposition into reactive •OH. We have developed a dual-mode assay combining colorimetric and electrochemical methods for the determination of nitrite in the environment. The detection limits are 1.58 and 2.99 μM, achieving a facile determination in the range of 50–300 μM. It also demonstrates the advantages of high sensitivity, anti-interference, and reliability. This work provides an idea for the preparation of nanomaterials with high-performance peroxidase activity and demonstrates their wide application in environmental monitoring.