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<p>Accurate monitoring of thiol-containing biomolecules is crucial for understanding redox balance in biological systems. However, conventional luminol-based electrochemiluminescence (ECL) systems rely on unstable H<sub>2</sub>O<sub>2</sub> or suffer from low dissolved O₂ solubility and sluggish kinetics, leading to insufficient reactive oxygen species (ROS) generation and competitive side reactions that compromise sensitivity and reproducibility. To overcome these limitations, we synthesized EuTb nanoparticles/N-doped carbon nanosheets (EuTb/NCSs) as a bimetallic valence relay catalysis (BVRC) platform for H<sub>2</sub>O<sub>2</sub>-free luminol ECL detection of L-cysteine (L-Cys). By engineering mixed-valence Tb³⁺/Tb⁴⁺ and Eu³⁺ active centers within the carbon framework, the system decouples cathodic oxygen reduction reaction (ORR) from anodic luminol oxidation, maximizing ROS utilization efficiency and avoiding competitive consumption pathways. The thiol groups of L-Cys scavenge the generated ROS, producing a concentration-dependent decrease in ECL intensity. The sensor achieved a broad linear range of 0.01–1000 ng mL⁻¹, a lower detection limit of 4.52 pg mL⁻¹, and reliable quantification of L-Cys in milk samples (97.7–101.9% recovery). This BVRC-mediated “ORR-first” strategy eliminates the kinetic bottleneck of luminol–O₂ systems, providing a transferable design principle for bioanalysis and food quality evaluation.</p> Graphical Abstract <p></p>

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Bimetallic valence relay catalysis in EuTb/N-doped carbon nanosheets: temporal decoupling of oxygen reduction resolves competitive kinetics for ultrasensitive electrochemiluminescence detection of L-cysteine

  • 期刊论文

  • 发表日期：

    2026年7月9日

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  • Yuan-Yuan Chen,
  • Ai-Jun Wang,
  • Jiu-Ju Feng,
  • Mingjiang Dan,
  • Tuck-Yun Y. Cheang

摘要

Accurate monitoring of thiol-containing biomolecules is crucial for understanding redox balance in biological systems. However, conventional luminol-based electrochemiluminescence (ECL) systems rely on unstable H2O2 or suffer from low dissolved O₂ solubility and sluggish kinetics, leading to insufficient reactive oxygen species (ROS) generation and competitive side reactions that compromise sensitivity and reproducibility. To overcome these limitations, we synthesized EuTb nanoparticles/N-doped carbon nanosheets (EuTb/NCSs) as a bimetallic valence relay catalysis (BVRC) platform for H2O2-free luminol ECL detection of L-cysteine (L-Cys). By engineering mixed-valence Tb³⁺/Tb⁴⁺ and Eu³⁺ active centers within the carbon framework, the system decouples cathodic oxygen reduction reaction (ORR) from anodic luminol oxidation, maximizing ROS utilization efficiency and avoiding competitive consumption pathways. The thiol groups of L-Cys scavenge the generated ROS, producing a concentration-dependent decrease in ECL intensity. The sensor achieved a broad linear range of 0.01–1000 ng mL⁻¹, a lower detection limit of 4.52 pg mL⁻¹, and reliable quantification of L-Cys in milk samples (97.7–101.9% recovery). This BVRC-mediated “ORR-first” strategy eliminates the kinetic bottleneck of luminol–O₂ systems, providing a transferable design principle for bioanalysis and food quality evaluation.

Graphical Abstract