Deep eutectic solvent-assisted synthesis of Artemisia argyi-derived carbon dots for smartphone-based Hg2+ determination

Mercury ion (Hg 2+ ) contamination poses a serious threat to the environment and human health, highlighting the need for sensitive and sustainable detection strategies. Herein, we proposed an eco-friendly and low-cost fluorescent detection platform for Hg 2+ using N-doped carbon dots (N-CDs) synthesized from Artemisia argyi-derived cellulose extracted via deep eutectic solvent (DES) technology. The N-CDs showed strong fluorescence quenching toward Hg 2+ , achieving a low detection limit of 1 nM with a wide linear range of 0.05 to 20 μM. Detailed investigation confirmed that the quenching behavior mainly originated from the specific interactions between Hg 2+ and surface functional groups of N-CDs. To enable on-site and real-time applications, a smartphone-based fluorescence sensing system was developed. The quantitative signal was extracted using the (G + B)/G parameter, where G and B represent the green and blue intensity components obtained from Red-Green-Blue images under UV illumination. A clear linear correlation was observed between Hg 2+ concentration and the (G + B)/G response. The method was successfully applied for Hg 2+ detection in real water samples, confirming its practicality. Overall, this green and effective sensing approach offers significant potential for water quality assessment and environmental monitoring.