Hollow carbon dots labeled with FITC or TRITC for use in fluorescent cellular imaging.

Hollow carbon dots (HCDs) were prepared by a solvothermal method and conjugated to either tetramethyl rhodamine isothiocyanate (TRITC) or fluorescein-5-isothiocyanate (FITC). This resulted in HCDs with bright red or green fluorescence, with excitation/emission peaks at 550/580 and 491/520 nm, respectively. The nanocomposites are well water-soluble, remarkably photostable and biocompatible. In addition, the fluorescence of the composites is more stable in a reactive oxygen environment than the free dyes. Confocal images indicate that the nanoparticles quickly enter A549 cells and mainly accumulate in the cytoplasm. The wavelength of functionalized HCDs can be regulating via coupling the HCDs to different dyes. These results demonstrate that these composite materials can be very promising reagents for biological labeling and imaging. Graphical abstract Schematic of the preparation of hollow carbon dots conjugated to tetramethyl rhodamine isothiocyanate (RHCDs) by solvothermal method. The material is water-soluble, remarkably photostable and biocompatible. It was applied to cellular labeling and imaging.