Green Synthesis of Nitrogen–Doped Carbon Dots from Fresh Tea Leaves for Selective Fe3+ Ions Detection and Cellular Imaging

In this research, we successfully developed a green, economical and effective one-step hydrothermal method for the synthesis of fluorescent nitrogen-doped carbon dots (N-CDs) by utilizing fresh tea leaves and urea as the carbon and nitrogen sources, respectively. The obtained N-CDs were characterized by TEM, XPS and FT-IR. We found that the N-CDs were near-spherical with an average size of about 2.32 nm, and contained abundant oxygen and nitrogen functional groups. The N-CDs exhibited bright blue fluorescence under ultraviolet illumination, with the maximum emission at 455 nm. Meanwhile, the as-prepared N-CDs could be selectively quenched by Fe