Facile preparation of Cu-doped carbon dots for naked-eye discrimination of phenylenediamine isomers and highly sensitive ratiometric fluorescent detection of H2O2

Changing a detection analyte into a colored material is a key challenge for visual discrimination of isomers. In this work, a novel fluorescent probe incorporating Cu-doped carbon dots (Cu-CDs), for the first time, was developed for naked-eye discrimination of phenylenediamine isomers and highly sensitive ratiometric fluorescence detection of H2O2. In this strategy, Cu-CDs were synthesized by a facile hydrothermal approach using citric acid, formamide, and CuCl2 as reactants. The prepared Cu-CDs exhibited outstanding peroxidase-like activity and stability. Consequently, a chemosensor platform based on Cu-CDs was constructed to enable naked-eye discrimination of phenylenediamine isomers through the H2O2-mediated oxidation reaction. Moreover, a Cu-CDs-based ratiometric fluorescence sensor was proposed as a means to sensitively detect H2O2 with a detection limit of 5.0 nM. The sensor was further employed for monitoring H2O2 in human serum, indicating its potential applications in other biologically related study.