Smartphone-assisted detection of mercury ion using Al-doped carbon dots for environmental water monitoring.

The monitoring of heavy metal ions, especially mercury (Hg), has become increasingly important due to their high toxicity, environmental persistence, and severe risks to human health. Herein, aluminum-doped carbon dots (Al-CDs) were synthesized via a one-step hydrothermal process using glutathione and AlCl·6HO as precursors. The resulting Al-CDs emitted strong and stable fluorescence, achieving a high quantum yield of 55.17%. The fluorescence of Al-CDs was efficiently and selectively quenched by Hg, enabling highly sensitive detection with a low limit of detection of 0.018 μM. This sensing method displayed remarkable selectivity toward Hg over other ions and biomolecules. For application in real water samples, this method delivered successful outcomes with high recovery rates. To support on-site detection, a smartphone-based sensing system and portable fluorescent test strips were developed, offering a convenient, low-cost, and user-friendly approach for mercury monitoring. This study demonstrates great potential of Al-CDs as efficient fluorescent probes for environmental analysis and offers a practical strategy for the facile and visual detection of toxic heavy metal ions.