Smartphone-assisted sensing platform based on dual-responsive nitrogen-doped carbon dots for enzyme-free and visual quantitative detection of Cu2+ and glyphosate

Rapid and selective detection of copper ion (Cu 2+ ) and glyphosate (GLY) is crucial to environmental pollution control, especially when using a simple and portable device. In this study, an enzyme-free and visual fluorescence sensor based on nitrogen-doped carbon dots (N-CDs) is successfully designed, featuring strong blue fluorescence and excellent stability. The sensor shows a linear response to Cu 2+ over a wide detection range of 0.048 to 40 μM with a low limit of detection (LOD, 48 nM), resulting in fluorescence quenching at 435 nm. Meanwhile, the rapid enhancement in fluorescence intensity of the quenched N-CDs/Cu 2+ system can be triggered by GLY owing to the strong complexation between Cu 2+ and GLY, with a LOD of GLY as low as 0.24 μM. Furthermore, we develop a smartphone-assisted sensing platform using N-CDs/polyvinyl alcohol films, which captures and analyzes fluorescence images to detect Cu 2+ and GLY with sensitive LODs of 73 nM and 0.32 μM, respectively. Satisfactory recoveries, ranging from 94.0 % to 104.6 %, are achieved in real sample detection, implying the potential application in the field of enzyme-free and on-site pesticides detection.