A reusable P, N-doped carbon quantum dot fluorescent sensor for cobalt ion

In this work, phosphorus, nitrogen co-doped carbon quantum dots (P,N-CQDs) as highly selective fluorescent probe for cobalt ion (Co2+) detection were designed and synthesized via a one-step hydrothermal protocol by employing pyridoxal 5-phosphate and ethanediamine. This probe enables selective detection of Co2+ with a linear range of 0–60 μM and a limit of detection of 0.053 μM through variation in fluorescence with respect to target concentration and electron-transfer from P,N-CQDs to Co2+. Furthermore, ethylenediaminetetraacetic acid-modified Fe3O4@SiO2 (Fe3O4@SiO2-EDTA) was tailor-designed and prepared to successfully realize the recovery of P,N-CQDs/Co2+ fluorescence for the first time. The reusable P,N-CQDs as fluorescent sensors for Co2+ also show good linearity and sensitivity. Ultimately, this fluorescent probe was applied in the analysis of real river water samples.