One-pot synthesis of nitrogen-doped carbon dots for sensing of Co2+ and tetracycline antibiotics, biological imaging, and fluorescent inks

Novel fluorescent nitrogen-doped carbon dots (N-CDs) derived from aloe vera and ethylenediamine were synthesized. The synthesized N-CDs emit bright blue fluorescence (lambda em = 450 nm) when the excitation wavelength is 370 nm. Owing to the obvious response to Co2+/tetracycline antibiotics (TCs), N-CDs can be designed as a "signal-off" fluorescent probe for sensitive detection of Co2+ in water samples and TCs (taking chlortetracycline (CTC) as an example) in water/milk samples with linear ranges of 1.48-243 mu M and 0.49-257 mu M. The limit of detection (LOD) of Co2+ and CTC are 39.3 nM and 17.7 nM (3 sigma/m). The recoveries of Co2+ and CTC were 94.00-104.46% and 94.00-105.33%, respectively, which are in an acceptable range. Taking into consideration the masking effect of ethylenediaminetetraacetic acid (EDTA) to Co2+, the selective detection of CTC can be realized. Furthermore, owing to the outstanding biocompatibility and optical performance, N-CDs have also been applied in biological imaging and fluorescent ink. In conclusion, the prepared N-CDs are expected to be widely used in environmental monitoring, food safety, and disease diagnosis.