Novel Paper-Based Fluorescent Sensor Based on N-Doped Carbon Quantum Dots (N-CQDs) and Cotton Fiber Paper (CFP) with High Selectivity and Sensitivity for the Visual Determination of Mercury (II) in Environmental Waters

Abstract

A highly selective solid-state fluorescent sensor based on N-doped carbon quantum dots (N-CQDs) and cotton fiber paper (CFP) is reported for the determination of trace mercury (II)(Hg²⁺). The N-doped carbon quantum dots on cotton fiber paper (N-CQDs@CFP) was synthesized using a facile one-step microwave hydrothermal method. Multiple approaches were employed to fully investigate the morphology and chemical structure of the paper-based fluorescent sensor. The N-CQDs were chemically bonded onto the CFP, which offers good reproducibility and stability of the sensor. The N-CQDs@CFP showed high-intensity blue emission in dark-field imaging, and the fluorescence was quenched by Hg²⁺. The Hg²⁺ in aqueous samples was easily determined and visually monitored. There was good linearity from 0 to 250 μM, and the limit of detection was 34 nM. The paper-based fluorescent sensor provided accurate and rapid determination of Hg²⁺ upon comparison with flame atomic absorption spectrophotometry (FAAS). The simple preparation, rapid detection (< 5 min), low cost, and easy-handling illustrate that the reported sensor has a significant value in environmental monitoring.

Keywords:

• Cotton fiber paper (CFP)
• in situ preparation
• mercury (II) determination
• N-doped carbon quantum dots (N-CQDs)
• paper-based fluorescent sensor

Acknowledgements

We thank LetPub for its linguistic assistance during the preparation of this manuscript.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China (grant number 21766028) and the Natural Science Foundation of Qinghai (grant number 2020-ZJ-722).