One-Pot Synthesis of Highly Fluorescent Carbon Dots from Spinach and Multipurpose Applications

Highly fluorescent carbon dots (CDs) have been prepared from natural spinach by a hydrothermal method. In this work, we have demonstrated that the CDs have a high quantum yield of 53%, and exhibit special responses to 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP). Solutions of the CDs showed clear fluorescence quenching in the presence of 2-NP and 4-NP; the detection limits of 2-NP and 4-NP were 1.06 and 0.50 mu m, respectively. Simultaneously, the color changed from colorless to yellow, visible to the naked eye. More importantly, spinach, as a carbon source, is much more eco-friendly than other organic dyes and organic solvents used for biosensors. Biological studies indicated that the CDs exhibit high fluorescent contrast and low toxicity in cells. Overall, the CDs prepared in this work can be used for fluorescent ink, biosensors, and bioimaging.