A novel L-lysine-derived carbon dots as an “On-Off-On” fluorescent sensor for efficient detection of mercury (II) and glutathione

Chiral carbon dots synthesized via low-temperature one-step hydrothermal method. • Constructing an “on–off-on” fluorescence sensing mode for dual detection. • Demonstrating exceptional detection sensitivity for Hg 2 ⁺ and GSH. • Verified the recognition mechanism potentially mediated by chiral fluorescent groups. Carbon dots (CDs) are widely used in fields such as ion recognition and small molecule detection due to their unique fluorescent properties. In this study, L-CD, a “on–off-on” fluorescent sensor for highly selective detection of Hg 2+ and glutathione (GSH), was rapidly synthesized via a low-temperature one-step hydrothermal reaction. The results revealed that chiral functional groups on its surface may act as luminescent moieties interacting with Hg 2+ and GSH, leading to fluorescence switching. Hg 2+ exhibited a unique two-phase response, while GSH can rapidly and stably restore the fluorescence of the L-CD + Hg 2+ . Mechanistic analysis suggests that the process involves not only static quench, but also may include dynamic quenching. Moreover, L-CD can be used to chemically modify filter paper to enable visual semi-quantitative detection of Hg 2+ and GSH. In actual samples, L-CD exhibit excellent accuracy (RSD < 5.0%) and can serve as reliable fluorescent sensors for the detection of Hg 2 ⁺ in complex system and the efficient identification of GSH in biological samples. Conclusively, this work synthesized chiral CDs with high quantum yields at mild conditions and validated the potential mechanism involving chiral fluorescent groups, providing essential reference for in-depth investigation into the luminescent behavior of CDs. Download: Download high-res image (122KB) Download: Download full-size image