Overview
Zheng and Zhou (2025) synthesize nitrogen-doped carbon dots (N-PCDs) via a one-step hydrothermal method using Pueraria (kudzu) root residue as the carbon precursor and urea as the nitrogen source. The resulting high-quantum-yield (42.96%) fluorescent nanomaterial is applied as a probe for hexavalent chromium Cr(VI) detection in water via fluorescence quenching through photoinduced electron transfer (PET). DFT calculations confirm the PET mechanism.
Key numbers
LOD: 0.078 µM Cr(VI) (equivalent to approximately 4.1 µg/L = 4.1 ppb in the measured solution).
LOQ: 0.26 µM Cr(VI) (approximately 13.5 µg/L = 13.5 ppb).
Recovery rates in real water matrices: 98.7% to 101.5% across river water, lake water, and tap water. These recovery values indicate good matrix performance in real environmental water samples.
Quantum yield of N-PCDs: 42.96% — high for biomass-derived carbon dots.
CC BY license.
Methods (brief)
Hydrothermal synthesis of N-PCDs from Pueraria residue + urea. Fluorescence quenching by Cr(VI) via PET mechanism confirmed by DFT. Validated in real water matrices (river, lake, tap water). LOD of 4.1 ppb Cr(VI) approaches regulatory limits for chromium in drinking water (WHO: 50 µg/L total Cr; EPA MCL: 100 µg/L total Cr). While the sensor detects Cr(VI) specifically — the more toxic and HMT&C-relevant species — the LOD in the single-digit µg/L range is meaningful for environmental monitoring.
Note: This sensor detects Cr(VI) specifically, not total chromium. Total chromium ≠ Cr(VI); the HMT&C analyte is Cr(VI).
Implications
Testing: LOD of ~4 ppb Cr(VI) in water matrices is analytically relevant and exceeds the performance of some competing colorimetric platforms. The PET mechanism provides specificity. This approach could be applicable to food leachate or food processing water monitoring. Not validated in food matrices directly.
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| Commit | Date | Change | Description |
|---|---|---|---|
| a8052bb | 2026-08-09 | major | 6 sections added; narrative text revised |