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 mu M and 1.57 mu M 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.