Indian Gooseberry-Derived Tunable Fluorescent Carbon Dots as a Promise for In Vitro/In Vivo Multicolor Bioimaging and Fluorescent Ink

We report the synthesis of eco-friendly fluorescent nitrogen-doped carbon dots (NCDs) using the renewable resource of Phyllanthus emblica juice as a precursor by the hydrothermal process at 200 °C for 12 h. The synthesized NCDs emitted bright fluorescence without any pretreatment of the sample under the excitation of UV light and exhibited excitation-dependent fluorescence emission. The NCDs have nitrogen-containing and oxygen-containing functional groups such as amino, hydroxyl, and carboxyl on the surface of the carbon structure. Furthermore, the NCDs exhibited excellent water dispersibility with prolonging stability and good biocompatibility. On the basis of the good optical properties, the NCDs have potentially been used as a promising staining agent on HCT-116 human colon cancer cells and Caenorhabditis elegans (nematodes) for multicolor cellular imaging. In the cell cytoplasm, the NCDs showed rapid uptake and high cytocompatibility on cellular morphology with bright fluorescence emission. Furthermore, the NCDs were used as fluorescent ink for writing and drawing with anticoagulation. In addition, the NCDs were significantly utilized as a fluorescent ink for thumb impression, which glows instantly under the illumination of UV light and does not require a secondary treatment. Hence, the synthesized NCDs can be used as ideal multicolor fluorescent probes for bioimaging applications and as fluorescent ink instead of traditional fluorescent ink.