Organic acid participation strategy for the synthesis of highly fluorescent carbon dots and their application in dual-mode determination of copper ions

In-depth research on surface functionalization of carbon dots (CDs) has opened new horizons for their application in chemosensing and biosensing. However, the practicability of CDs is still limited due to their unmanageable fluorescence properties. In this study, organic acid was employed to regulate and control the fluorescence performance of CDs. A remarkable enhancement of fluorescence and redshift of the fluorescent band of CDs was observed via organic acids' participation in the water phase preparation process. Furthermore, a colorimetric and fluorescent dual-readout strategy was constructed for the analysis of copper ions (Cu2+) based on ethylenediaminetetraacetic acid (EDTA)-regulated carbon dots. The proposed sensing system can be used in the fast detection of Cu2+ via an obvious solution color change from yellow to brown under natural light, and the trace analysis of Cu2+ can be realized by quenching the green fluorescence band with detection limit of 21 nM. The designed sensor has been employed to the analysis of Cu2+ in water and urine samples successfully, and cell imaging experiment was performed to evaluate the feasibility of biomedical applications.