Concentration-regulated multi-color fluorescent carbon dots for the detection of rifampicin, morin and Al³⁺

Carbon dots have many new and interesting phenomena, and the concentration dependent luminescence wavelength is an intriguing one. Herein, nitrogen-sulfur co-doped carbon dots (NSCDs) diluted to different concentrations, the high concentration of G-NSCDs (0.2 mg mL⁻¹) with green fluorescence and the low-concentration of B-NSCDs (0.01 mg mL⁻¹) with blue fluorescence were obtained. Further, it was found that the detection behaviors are different for different concentrations. The “turn-off” fluorescent sensor of G-NSCDs can specifically recognize rifampicin in a linear range of 0.2–20 μM with a detection limit of 56.6 nM employing the mutual effect of photo-induced electron transfer and dynamic quenching. Meanwhile, a “turn-off” B-NSCDs fluorescence sensor was constructed to effectively identify morin based on the internal filtration effect and static quenching, achieving a suitable linearity of 0.2–30 μM and a detection limit of 51.2 nM. Due to the strong chelation of morin and Al³⁺, a “turn-on” fluorescent probe for sequential detection Al³⁺ was fabricated based on B-NSCDs-morin system, obtaining a good linearity of 0.1–2.0 μM with a satisfactory detection limit of 45.8 nM. These interesting behaviors indicate that NSCDs are expected to become novel sensing materials for the monitoring of rifampicin, morin and Al³⁺ in organisms, which is beneficial for our health.