Highly Photoluminescent Carbon Dots with pH-Dependent Switchable Fluorescence and Sensitivity to Tetracycline

In this paper, multifunctional nitrogen-doped carbon dots (N-CDs) were synthesized from 3,5-diaminobenzonitrile by a simple one-step hydrothermal method. The N-CDs have a high quantum yield of 67.0% in ethanol with great water solubility, temperature stability, light stability and resistance to ion interference. Experiments showed that pH has an effect on the fluorescence intensity and emission wavelength of N-CDs. Especially, the switchable fluorescence of N-CDs caused by changes of pH value could be distinguished to the naked eye. Additionally, the multifunctional N-CDs also showed a selective response to tetracycline. We studied the influence of tetracycline on the luminescence intensity of N-CDs in the concentration range of 0–1000[Formula: see text][Formula: see text]g/L. A linear equation was established in the range of 10–80[Formula: see text][Formula: see text]g/L with a limit of detection (LOD) of 3.5[Formula: see text][Formula: see text]g/L. Based on the above excellent characteristics, N-CDs are expected to be applied in the field of sensing.