Sulfur-doped carbon dots derived from cabbage leaves for the determination of alizarin

Sulfur-doped carbon dots (S-CQDs) in the light of cabbage leaves were suggested through using a one-pot hydrothermal strategy. The cysteine was used as a sulfur dopant. Transmission electron microscope (TEM) suggested that the morphology of S-CQDs was highly dispersed and the particle size distribution range was located at 3.2–3.8 nm. Four elements (C, N, O and S) could be observed through X-ray photoelectron spectroscopy (XPS). Some oxygen-containing and amino-containing groups could also be indicated by using Fourier transform infrared spectroscopy (FT-IR). The S-CQDs suggested bright blue fluorescence under UV light. At the same time, the S-CQDs displayed exceptional anti bleaching property and salt resistance under UV light and NaCl solution, respectively. Moreover, the S-CQDs could be applied as excellent fluorescent nanoprobes to detect alizarin based on the fluorescence quenching strategy. The linear detection range was 0.5–100 μM with the detection limit of 0.14 μM. The fluorescence quenching principle was thoroughly studied based on the related characterizations. The behavior of the detection platform was studied in actual samples by using tap water, Yili milk and iced black tea samples. Finally, the S-CQDs could be applied for the sensing of temperature.