Nitrogen-Doped Carbon Dots Prepared via Microchannel Method for Visual Detection of Copper Ions

Copper ions (Cu²⁺) play a crucial role in biological processes; however, excessive intake can result in severe health problems. Current methods for detecting copper ions are both expensive and complex. Therefore, there is a need for efficient and straightforward visual detection methods. In this study, novel nitrogen-doped carbon dots (N-CDs) were synthesized via a microchannel method using diethylenetriamine and citric acid as precursors and were characterized by TEM, XRD, and IR, among others. The N-CDs demonstrated high selectivity and strong fluorescence, showing a linear quenching response to copper ions with a detection limit of 46 nM, whereas other common metal ions, such as Ca²⁺ and Mg²⁺, exhibited negligible interference even at higher concentrations. These N-CDs were subsequently applied to test paper, allowing for on-site visual and quantitative detection of copper ions via a colorimetric method. This approach provides a novel solution for the rapid detection of copper ions, with significant potential in environmental monitoring, public health, and industrial applications.