Non-conjugated polymer carbon dots for fluorometric determination of metronidazole

Non-conjugated polymer carbon dots (PCDs) with a 9% fluorescence quantum yield were synthesized by a pyrolytic method using polyethyleneimine as the sole precursor. The PCDs have an average size about 2.1 nm and a blue fluorescence, with excitation/emission maxima at 380/457 nm, that is quenched by the drug metronidazole. The method has a linear response in the 0.06-15 μg mL^-1 metronidazole concentration range and a 20 ng mL^-1 detection limit. Milk samples were spiked at two levels (0.6 and 5.0 μg mL^-1), and the recoveries of metronidazole are in the range of 96.7-102.2%. Graphical abstract Schematic representation of preparation of non-conjugated polymer carbon dots (PCDs) and detection of metronidazole. Metronidazole with negative charge is easy to produce electrostatic interaction with polyethyleneimine chain with positive charge, which leads to PCDs fluorescence quenching, so as to realize metronidazole detection.