Dual Quenching Fluorescent Detection of Cr(VI) Using N,S,P Co-Doped Carbon Dots Prepared via Rapid Microwave Synthesis
DOI:
https://doi.org/10.48048/tis.2026.13064Keywords:
Tri-atom-doped carbon dots, Fluorescence sensing, Chromium (VI) detection, Inner filter effect, Static quenching, Environmental monitoring, Microwave-assisted synthesisAbstract
A rapid and sustainable microwave-assisted method was developed for synthesizing nitrogen-, sulfur-, and phosphorus-co-doped carbon dots (N,S,P-CDs) using citric acid as the carbon precursor, along with ethylenediamine, thioglycolic acid, and phosphoric acid as dopant sources, for the early detection of Cr(VI) in aqueous environments. The process achieved highly efficient dopant incorporation in just 30 s at 450 W, demonstrating its green, energy-saving characteristics. Beyond achieving an exceptional quantum yield of 89.64%, this study provides detailed insight into the N,S,P-CDs–Cr(VI) interaction and dual quenching mechanism, explaining the synergistic roles of IFE and SQE in N,S,P-CDs, with high selectivity confirmed in the presence of various cations and anions, an aspect rarely discussed in previous research. In-depth analysis of morphological and optical features, including UV-Vis, FT-IR, Raman, XRD, HR-TEM, zeta potential analyzer, and spectrofluorometer, confirmed effective doping and co-doping, the formation of a carbonaceous core structure, and the resulting strong fluorescence emission. The synthesized N,S,P-CDs exhibited high photostability and strong stability against pH and ionic-strength variations, with a linear detection range of 0 - 100 µM, a low limit of detection of 0.07354 µM, and a limit of quantification of 0.2451 µM. The sensor demonstrated competitive sensitivity, together with high analytical accuracy and precision. Application to real water samples verified accurate Cr(VI) detection below WHO limits, confirming the N,S,P-CDs as a sustainable and sensitive fluorescent platform for monitoring toxic metal pollutants in water.
HIGHLIGHTS
- N,S,P co-doped carbon dots were rapidly synthesized by a microwave-assisted method within 30 s at 450 W.
- Tri-atom doping promoted graphitic core formation and surface passivation, yielding a high quantum yield of 89.64%.
- Structural and optical characterizations confirmed successful heteroatom doping and graphitic core formation.
- The fluorescence response toward Cr(VI) arose from the combined contribution of the inner filter effect and static quenching.
- The N,S,P-CDs enabled highly selective and ultrasensitive Cr(VI) detection in real water samples with a detection limit of 0.07354 µM.
GRAPHICAL ABSTRACT
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