Carrageenan-derived sulfur, nitrogen co-doped carbon dots for sequential detection of Ag+ and Lime Sulfur with “on-off-on” pattern

Heteroatom doped carbon dots have great potential in sensing field because of their good optical properties, high selectivity and sensitivity to targets. Herein, sulfur and nitrogen co-doped carbon dots (SNCDs) was synthesized by one-step hydrothermal reaction of κ-carrageenan and glutathione. The surface of the prepared SNCDs was modified by active groups, which not only enhance the optical properties, but also improve the analytical detection performance. Then, SNCDs, as a high-efficient “on-off-on” fluorescent sensor, was fabricated for sequence determination of Ag + and Lime Sulfur (LS). Furthermore, it performed good selectivity and sensitivity to Ag + and LS even with the interference of other metal ions or pesticides. The linear detection range of Ag + and LS by SNCDs was 0–100 µM and 0–1 mg/L, and the detection limit was 0.124 µM and 50 µg/L, respectively. More importantly, it has been successfully used in the detection of actual water samples with recovery rates of 98.6~107.1%. In addition, a portable, reusable and highly absorbent fluorescent resin ball was constructed to enrich the application of SNCDs. • S, N co-doped carbon dot (SNCDs) was synthesized by κ-carrageenan and glutathione in one step. • The prepared SNCDs can be applied for the sequential detection of Ag + and Lime Sulfur. • Fluorescent resin balls were prepared for further application