N, S co-doped carbon dots for fluorescent and colorimetric dual-mode detection of Co(II) in actual water

This study focuses on the synthesis of nitrogen and sulfur co-doped carbon dots (N, S-CDs) using a hydrothermal method, and its application as a fluorescence and colorimetric dual-mode probe for simple and rapid detection of Co(II). When Co(II) reacts with N, S-CDs, metallic bonds are formed, leading to a static quenching effect (SQE). The electrostatic interaction between positive-charged cobalt complexes and negative-charged N, S-CDs induces the aggregation of metal complexes, increasing the particle size from 5.44 nm to 258.72 nm and resulting in a noticeable visual color change ultimately. N, S-CDs exhibited excellent potential for application in actual water samples, with the low detection limit (LOD) of 2.64 µM and 1.57 µM via fluorescence and colorimetric methods, respectively, and the recovery rate ranged from 94 % to 103 %. As far as we consider, the cross-referenced dual-mode platform proposed here may be an attractive strategy for the construction of high-performance sensors available for metal ion detection in actual aquatic environments.