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<p>Reliable nitrite (NO₂⁻) detection is critical due to its toxicity, carcinogenic potential, and environmental relevance. In this study, MIL-101(Fe) nanozymes with dual oxidase-like and peroxidase-like activities were synthesized to develop a fluorescence-based NO₂⁻ sensing platform via DA-mediated oxidation. Mechanistic studies reveal that superoxide radicals (•O₂⁻) generated via the oxidase-like pathway are the primary reactive species (~ 80% contribution), while H₂O₂ plays an essential supporting role in regenerating Fe³⁺ active sites. Under catalytic conditions, DA reacts with 5, 7-dihydroxy-4-methyl-2&#xa0;h-benzopyrane-2-one (DHMBP) to form a green-fluorescent azocine product (λₑₘ = 498&#xa0;nm) with a high quantum yield (Φ = 78.5%) and fluorescence lifetime (τ₀ = 4.68 ns). In the presence of NO₂⁻, DA is diverted toward a deamination pathway, forming non-fluorescent 4-ethylcatechol (confirmed by HRMS) and inhibiting fluorescence. This competitive mechanism enables sensitive, selective NO₂⁻ quantification over a linear range of 0.1–320 µM with a limit of detection (LOD) of 0.033 µM (S/<i>N</i> = 3) and a limit of quantification (LOQ) of 0.11 µM. The platform demonstrated excellent recoveries (96.0–105.0%) in real-world samples, including environmental water and food, with relative standard deviations (RSD &lt; 4.5%) and strong correlation with ion chromatography (t-test, <i>p</i> &gt; 0.05). The MIL-101(Fe) nanozyme exhibited remarkable reusability (&gt; 91% activity after 5 cycles) and storage stability (&gt; 95% activity for 10 days at 4&#xa0;°C). This work presents a reliable, interference-resistant, and reusable approach for NO₂⁻ monitoring across diverse matrices, with potential for field-deployable applications.</p> Graphical Abstract <p></p>

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Competitive Dopamine Oxidation–Deamination Enables Selective Fluorescent Detection of Nitrite Using MIL-101(Fe) nanozymes

  • 期刊论文

  • 发表日期：

    2026年7月18日

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  • Ramadan Ali,
  • Abdullah S Albalawi,
  • Farah M. Alatawi,
  • Rawan A. Alanazi,
  • Ashjan M. Alruwaili,
  • Besan B. Albalawi,
  • Bayan B. Albalawi,
  • Maram M. Alkorbi,
  • Turki A. Aljuaid,
  • Yazan T. Almojmami,
  • Riyadh S. Alotibi,
  • Mohamed M. El-Wekil

摘要

Reliable nitrite (NO₂⁻) detection is critical due to its toxicity, carcinogenic potential, and environmental relevance. In this study, MIL-101(Fe) nanozymes with dual oxidase-like and peroxidase-like activities were synthesized to develop a fluorescence-based NO₂⁻ sensing platform via DA-mediated oxidation. Mechanistic studies reveal that superoxide radicals (•O₂⁻) generated via the oxidase-like pathway are the primary reactive species (~ 80% contribution), while H₂O₂ plays an essential supporting role in regenerating Fe³⁺ active sites. Under catalytic conditions, DA reacts with 5, 7-dihydroxy-4-methyl-2 h-benzopyrane-2-one (DHMBP) to form a green-fluorescent azocine product (λₑₘ = 498 nm) with a high quantum yield (Φ = 78.5%) and fluorescence lifetime (τ₀ = 4.68 ns). In the presence of NO₂⁻, DA is diverted toward a deamination pathway, forming non-fluorescent 4-ethylcatechol (confirmed by HRMS) and inhibiting fluorescence. This competitive mechanism enables sensitive, selective NO₂⁻ quantification over a linear range of 0.1–320 µM with a limit of detection (LOD) of 0.033 µM (S/N = 3) and a limit of quantification (LOQ) of 0.11 µM. The platform demonstrated excellent recoveries (96.0–105.0%) in real-world samples, including environmental water and food, with relative standard deviations (RSD < 4.5%) and strong correlation with ion chromatography (t-test, p > 0.05). The MIL-101(Fe) nanozyme exhibited remarkable reusability (> 91% activity after 5 cycles) and storage stability (> 95% activity for 10 days at 4 °C). This work presents a reliable, interference-resistant, and reusable approach for NO₂⁻ monitoring across diverse matrices, with potential for field-deployable applications.

Graphical Abstract