Facile and Green Synthesis of Carbon Dots from Melia Azedarach Leaves for pH Sensing and Cell Imaging

Carbon dots (CDs) have preeminent application prospects as a new star in the nanomaterials field. In this work, a green and facile method to synthesize the blue-emitting CDs was proposed with Melia azedarach leaves as the carbon precursors. Using nature materials without other expensive reagents and instruments, the processes were simple and environmental-friendly. The CDs had high fluorescence quantum yield (11.8%) and excellent luminescence properties. The size of them were among 1.5–2.5 nm and the emission spectrum exhibited a strong peak at 460 nm when excited at 380 nm. Additionally, the CDs were stable in most ions but sensitive to different pH values. As a result, a pH sensor was established for the detection of pH with a linear range of 3–10 pH. Moreover, it was demonstrated that the synthesized CDs had extremely low cytotoxicity. Due to their low toxicity and good biocompatibility, they entered into the A549 cells successfully for cell imaging.