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<p>The development of nitrogen-rich nanozymes is of great significance for enhancing enzyme-mimicking catalytic activity and is widely regarded as a pivotal strategy toward advancing highly sensitive colorimetric sensing platforms. In this work, Fe–N-C nanozymes featuring a high nitrogen content of 21.7 at% were synthesized via controlled pyrolysis of ZIF-8 as a sacrificial template. Owing to their well-defined porous architecture and dispersed Fe–N active sites, these nanozymes exhibited superior oxidase-mimicking catalytic activity. The enzyme kinetic analysis yielded a Michaelis constant (K<sub>m</sub>) of 0.267&#xa0;mM and a maximal initial velocity (V<sub>max</sub>) of 6.78 × 10<sup>−8</sup>&#xa0;M&#xa0;s<sup>−1</sup>. Leveraging these distinctive kinetic properties, we designed a colorimetric nanozyme assay enabling highly sensitive and quantitative determination of tannic acid. A linear correlation was observed between the assay signal and tannic acid concentration over the 0.1–4.0&#xa0;μM range, yielding the calibration equation y = 0.25x − 0.017 (R<sup>2</sup> = 0.99). Based on the 3σ/k method, the detection limit was calculated as 59.6&#xa0;nM. This concentration range falls below the tannic acid levels typically observed in commercial tea beverages, suggesting its potential for detecting real samples. Furthermore, by exploiting the pH-dependent catalytic efficiency of the Fe–N-C material and precisely tuning the pH of the reaction medium, a two-channel colorimetric sensing platform was fabricated. This array enabled accurate identification and discrimination of tannic acid from a panel of structurally related polyphenols. More importantly, the sensor array showed robust performance in the discrimination and quantification of tannic acid in real tea beverage samples. Overall, this work provides an effective strategy for engineering highly active Fe–N-C materials and highlights their practical potential for rapid and selective tannic acid detection in complex real-world matrices.</p>

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Construction of N-rich Fe–N-C nanozymes with excellent oxidase-like activity for highly sensitive colorimetric detection and precise identification of tannic acid

  • 期刊论文

  • 发表日期：

    2026年7月21日

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  • Zitong Zhou,
  • Xuke Fan,
  • Mengpan Zhang,
  • Yulan Zhang,
  • Ming-gang Chen,
  • Ying Bian,
  • Yijun Pang,
  • Binhua Luo

摘要

The development of nitrogen-rich nanozymes is of great significance for enhancing enzyme-mimicking catalytic activity and is widely regarded as a pivotal strategy toward advancing highly sensitive colorimetric sensing platforms. In this work, Fe–N-C nanozymes featuring a high nitrogen content of 21.7 at% were synthesized via controlled pyrolysis of ZIF-8 as a sacrificial template. Owing to their well-defined porous architecture and dispersed Fe–N active sites, these nanozymes exhibited superior oxidase-mimicking catalytic activity. The enzyme kinetic analysis yielded a Michaelis constant (Km) of 0.267 mM and a maximal initial velocity (Vmax) of 6.78 × 10−8 M s−1. Leveraging these distinctive kinetic properties, we designed a colorimetric nanozyme assay enabling highly sensitive and quantitative determination of tannic acid. A linear correlation was observed between the assay signal and tannic acid concentration over the 0.1–4.0 μM range, yielding the calibration equation y = 0.25x − 0.017 (R2 = 0.99). Based on the 3σ/k method, the detection limit was calculated as 59.6 nM. This concentration range falls below the tannic acid levels typically observed in commercial tea beverages, suggesting its potential for detecting real samples. Furthermore, by exploiting the pH-dependent catalytic efficiency of the Fe–N-C material and precisely tuning the pH of the reaction medium, a two-channel colorimetric sensing platform was fabricated. This array enabled accurate identification and discrimination of tannic acid from a panel of structurally related polyphenols. More importantly, the sensor array showed robust performance in the discrimination and quantification of tannic acid in real tea beverage samples. Overall, this work provides an effective strategy for engineering highly active Fe–N-C materials and highlights their practical potential for rapid and selective tannic acid detection in complex real-world matrices.