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<p>This study synthesized quantum dots (QDs) via a hydrothermal method at 165&#xa0;°C using citric acid and cysteine hydrochloride as precursors. A simple, rapid, and highly sensitive quantitative detection method for Co<sup>2+</sup> was established and applied to the analysis and monitoring of Co<sup>2+</sup> in water and soil. The research found that Co<sup>2+</sup> interacts with functional groups on the QDs (such as C-S, N-H, and C-O) through coordination, electrostatic, and Van der Waals forces, forming a stable, non-fluorescent ground-state complex. This leads to a significant quenching of the QDs’ fluorescence intensity at an excitation wavelength of 350&#xa0;nm. After optimizing the detection conditions, the best performance was achieved at 25&#xa0;°C, pH 9, with a mixing time of 5&#xa0;min. The method demonstrated a good linear relationship within the range of 10–150 µM, with a linear regression equation of Y = -0.0053X + 0.95923 (R<sup>2</sup> = 0.9894). The limit of detection (LOD) was calculated as 7.76 µM (based on 3σ/k). The quenching mechanism is attributed to the formation of a non-fluorescent ground-state complex between Co<sup>2+</sup> and surface functional groups of the QDs, leading to static quenching via efficient electron/energy transfer. The inherent differences in binding constants with ligand groups and electron affinities among different metal ions—embodying the principle that “structure determines function”—enable effective discrimination between target Co<sup>2+</sup> and potential interfering ions in complex aqueous matrices. Excellent recovery rates and precision obtained in real water and soil samples validated the reliability of the analytical signal.</p>

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Quantum dot fluorescence-based analysis of cobalt ions and practical environmental monitoring

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Xiaolin Wang,
  • Yilei Chen,
  • Zitong Wu,
  • Jinyang Chen,
  • Shuyu Liu,
  • Dingjiang Chen

摘要

This study synthesized quantum dots (QDs) via a hydrothermal method at 165 °C using citric acid and cysteine hydrochloride as precursors. A simple, rapid, and highly sensitive quantitative detection method for Co2+ was established and applied to the analysis and monitoring of Co2+ in water and soil. The research found that Co2+ interacts with functional groups on the QDs (such as C-S, N-H, and C-O) through coordination, electrostatic, and Van der Waals forces, forming a stable, non-fluorescent ground-state complex. This leads to a significant quenching of the QDs’ fluorescence intensity at an excitation wavelength of 350 nm. After optimizing the detection conditions, the best performance was achieved at 25 °C, pH 9, with a mixing time of 5 min. The method demonstrated a good linear relationship within the range of 10–150 µM, with a linear regression equation of Y = -0.0053X + 0.95923 (R2 = 0.9894). The limit of detection (LOD) was calculated as 7.76 µM (based on 3σ/k). The quenching mechanism is attributed to the formation of a non-fluorescent ground-state complex between Co2+ and surface functional groups of the QDs, leading to static quenching via efficient electron/energy transfer. The inherent differences in binding constants with ligand groups and electron affinities among different metal ions—embodying the principle that “structure determines function”—enable effective discrimination between target Co2+ and potential interfering ions in complex aqueous matrices. Excellent recovery rates and precision obtained in real water and soil samples validated the reliability of the analytical signal.