Green–Red Emissive Carbon Dots Interact with Lipidic Membranes: Implications for Staining and Penetrating Cellular Membranes

We report the synthesis of crystalline UreaPhen carbon dots (CDs) utilizing the hydrothermal approach followed by fractionation. Two major fractions of CDs show a graphitic core structure, and the shell is decorated with amine and carboxyl functional groups. Both fractions show a highly intense photoluminescence signal in the green-red region of the visible spectrum and can partition in an oil–water mixture. We show the application of the CD fractions for labeling purely lipidic and native membranes using giant unilamellar vesicles (GUVs) and mammalian cells. The imaging data confirm that CD fractions specifically bind to membranes, staining the membrane boundary. They can even penetrate the membranes and reach the cellular nucleolus, depending on the density of the functional groups on the shell of the CD particles.