The self-nitrogen-doped carbon quantum dots derived from Morus alba L. leaves for the rapid determination of tetracycline

Morus alba L. (Mulberry), one of industrial crops, have been widely cultivated in China, mulberry leaves (Folium Mori), one of the main products of Morus alba L., is high yield and rich in nitrogen element, high-value-utilization of mulberry leaves is very important for agricultural economic development. Carbon quantum dots have been attracting extensive attention because of their excellent properties including tunable fluorescence, bio-compatibility, non-toxicity, high water-solubility, and ease of functionalization. Heteroatoms doping is an effective way to improve quantum yield and fluorescence performance of carbon quantum dots. In this work, the self-nitrogen-doped carbon quantum dots was prepared from mulberry leaves, a nitrogen-rich, economic value-high and eco-friendly crops products, via a facile one-step hydrothermal method. The as-prepared self-nitrogen-doped carbon quantum dots exhibited certain stability, solubility and fluorescence intensity (quantum yield is 9.3%). With the introduction of tetracycline, the efficiency fluorescence quenching was observed, and an obvious color change can also be identified through naked eye. The fluorescence quenching mechanism is induced by internal filtering effect and static quenching. Based on this phenomenon, a rapid, naked-eye, and dual-readout assay for tetracycline detection was constructed and prepared as a fluorescent test paper. The linear range and detection limit of tetracycline were 0.158–40 μM and 158 nM, respectively. Other types of antibiotics, comment ions and chemicals show little influence on tetracycline detection. Furthermore, the constructed dual-readout assay was employed to detect tetracycline in river water with recovery range of 98.6–102.2%, relative standard deviation less than 2.54%. The constructed fluorescence probe show potential application to tetracycline detection in the real water sample.