Solvent extraction-assisted pyrolysis synthesis of N doped citric acid-based carbon dots for ciprofloxacin detection and anti-counterfeiting applications

In this study, citric acid-based N-doped carbon dots (N-CDs) were rapidly synthesized via open pyrolysis. A facile extraction strategy was proposed to promote the separation of N-CDs by orderly addition of toluene and water. The prepared N-CDs exhibited a high quantum yield (0.53) and excellent dispersibility in solvents of various polarities. The bright blue N-CDs were applied as a fluorescence sensor for ciprofloxacin (CIP) detection due to inner filter effect (IFE) and static quenching. The N-CDs sensor exhibited a good two-phase linear relation with CIP with a low detection limit of 0.14 µM. The sensing platform for CIP detection in milk and eye drops was further developed successfully, indicating its potential for CIP detection in real samples. N-CDs-based fluorescent ink was also prepared for anti-counterfeiting. Furthermore, the polyvinyl alcohol/N-CDs film had comparable bright fluorescence with ∼80 % color purity, which further expands the application of N-CDs as photovoltaic materials. The extraction strategy of using different-polarity solvents may open a new way for preparing amphipathic nanomaterials.