A graphene quantum dots based dual-modal fluorometric and visualized detection of copper ions

In this study, we present a dual-modal fluorometric and visualized detection method for Cu²⁺ ion, leveraging the synergistic properties of graphene quantum dots (GQDs) and Cu²⁺ ion catalyzed Fenton-like reaction. The Fenton-like reaction of Cu²⁺ ions and ascorbate generates highly reactive hydroxyl radical (·OH), which effectively disrupt the structure of GQDs, leading to fluorescence quenching. Under optimized conditions, the fluorescence quenching degree exhibited a linear correlation with Cu²⁺ concentration within the range of 40 to 2000 nM, enabling the detection of Cu²⁺ ions as low as 40 nM. Furthermore, we demonstrated the feasibility of semi-quantitative visual detection of Cu²⁺ ion concentrations in water using a portable ultraviolet instrument. The method achieved a minimum detectable concentration of Cu²⁺ ion as low as 10 μM, surpassing the maximum contaminant level goals of 20.47 μM set by the EPA and the guideline value of 31.47 μM recommended by the WHO. As such, this approach holds promise as a point-of-care testing (POCT) method for Cu²⁺ ion detection during copper pollution emergency events in water. Additionally, this method can be adapted for the detection of ascorbic acid. Our findings showcase the potential of this dual-modal detection approach, offering a sensitive, rapid, and efficient means for detecting Cu²⁺ ion, thereby contributing to environmental monitoring and public health applications.