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<p>Nitrite (NO<sub>2</sub><sup>−</sup>) is a well-known pollutant and carcinogen, making point-of-care (POC) detection an urgent concern. In this study, Fe<sub>3</sub>C/Mo<sub>2</sub>C hollow spheres (<b>Fe</b><sub><b>3</b></sub><b>C/Mo</b><sub><b>2</b></sub><b>CHS</b>) were successfully synthesized. As a nanozyme, <b>Fe</b><sub><b>3</b></sub><b>C/Mo</b><sub><b>2</b></sub><b>CHS</b> exhibits superior peroxidase-like (POD-like) activity compared with Fe<sub>3</sub>C and Mo<sub>2</sub>C. For H<sub>2</sub>O<sub>2</sub>, K<sub>m</sub> is 0.0683 mM with V<sub>max</sub> 3.87 × 10<sup>− 5</sup> M·min<sup>− 1</sup>. Within <b>Fe</b><sub><b>3</b></sub><b>C/Mo</b><sub><b>2</b></sub><b>CHS</b>, strong d-d coupling between Mo and Fe induces charge redistribution at the Fe<sub>3</sub>C/Mo<sub>2</sub>C heterointerface. In the presence of <b>Fe</b><sub><b>3</b></sub><b>C/Mo</b><sub><b>2</b></sub><b>CHS</b> and H<sub>2</sub>O<sub>2</sub>, colorless 3,3,5,5-tetramethylbenzidine (TMB) is oxidized to blue ox-TMB, which subsequently reacts with NO<sub>2</sub><sup>−</sup> to produce a yellow diazotization product. Based on this reaction, a POC digital image colorimetric method was developed for NO<sub>2</sub><sup>−</sup> detection using a smartphone. The method demonstrates an excellent linear response over the 2-300 µM range. The limit of detection (LOD) for <b>Fe</b><sub><b>3</b></sub><b>C/Mo</b><sub><b>2</b></sub><b>CHS</b> is 2.09 µM. Interference studies with various ions confirm the high selectivity of this approach for NO<sub>2</sub><sup>−</sup>. Moreover, the method exhibits reliable performance and reproducibility for practical NO<sub>2</sub><sup>−</sup> detection in food and water samples.</p> Graphical abstract <p></p>

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Hollow nanozyme with improved peroxidase-like activity for nitrite detection

  • 期刊论文

  • 发表日期：

    2026年7月4日

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  • Kequan Yao,
  • Junjun Lu,
  • Xinjiao Wang,
  • Xinxin Xu

摘要

Nitrite (NO2−) is a well-known pollutant and carcinogen, making point-of-care (POC) detection an urgent concern. In this study, Fe3C/Mo2C hollow spheres (Fe3C/Mo2CHS) were successfully synthesized. As a nanozyme, Fe3C/Mo2CHS exhibits superior peroxidase-like (POD-like) activity compared with Fe3C and Mo2C. For H2O2, Km is 0.0683 mM with Vmax 3.87 × 10− 5 M·min− 1. Within Fe3C/Mo2CHS, strong d-d coupling between Mo and Fe induces charge redistribution at the Fe3C/Mo2C heterointerface. In the presence of Fe3C/Mo2CHS and H2O2, colorless 3,3,5,5-tetramethylbenzidine (TMB) is oxidized to blue ox-TMB, which subsequently reacts with NO2− to produce a yellow diazotization product. Based on this reaction, a POC digital image colorimetric method was developed for NO2− detection using a smartphone. The method demonstrates an excellent linear response over the 2-300 µM range. The limit of detection (LOD) for Fe3C/Mo2CHS is 2.09 µM. Interference studies with various ions confirm the high selectivity of this approach for NO2−. Moreover, the method exhibits reliable performance and reproducibility for practical NO2− detection in food and water samples.

Graphical abstract