Abstract: A uniform square shaped IrO₂@MnO₂ nanocomposite with a particle size of about 136 nm was prepared by the in-situ integration method. Results show that the nanocomposite has synergistically improved oxidase mimic activity, and its K_mvalue is 6.50 × 10^-3 mmol/L which is better than that of IrO₂ NPs (K_m = 9.73 × 10^-2 mmol/L) and MnO₂ NPs (K_m = 2.41 × 10^-1 mmol/L), respectively. In addition, the optimal sensing conditions of IrO₂@MnO₂ nanocomposite for AA detection are obtained through experiments, which include the reaction system at pH 4, the reaction temperature at 37 ℃, the reaction time at 5 min, and the concentration of IrO₂@MnO₂ nanocomposite at 71.43 μg/mL. Finally, the IrO₂@MnO₂ nanocomposite is used for sensitive detection of AA, the detection range is 0~312.5 μmol/L, thequantification limit is 14.2 μmol/L and the detection limit is 1.42 μmol/L.

Key words: oxidase-like nanozyme, ascorbic acid detection, iridium dioxide, manganese dioxide