Electrolysis‐Mediated Rapid Synthesis of Highly Fluorescent and pH Responsive Congo Red Carbon Nanodots for Cu2+ Sensing

Abstract Copper ion (Cu 2+ ) is a highly toxic environmental pollutant with bioaccumulative properties, making its rapid and selective detection important for environmental and health monitoring. In this study, highly fluorescent carbon nanodots by the electrolysis of Congo Red are developed, which are denoted as CR‐CDs and exhibit high quantum yield and pH‐responsive character. The pH response behavior is applied for pH test in soft drinks with high accuracy. Cu 2+ causes dramatic fluorescence quenching due to the formation of cupric amine complex and the occurrence of inner filter effect. The signal changes in fluorescence spectroscopy allow a detection limit of Cu 2+ at 0.13 μM. The response is highly specific toward Cu 2+ over other metal ions. In addition, the practicability of the sensor is validated by accurate Cu 2+ examination in running water samples.