Carbon-based quantum dots for fluorescence imaging of cells and tissues

Carbon dots (or carbon quantum dots in some literature reports), generally small carbon nanoparticles with various surface passivation effects, have attracted widespread attention in recent years, with a rapidly increasing number of research publications. The reported studies covered many aspects of carbon dots, from the development of many new synthetic methodologies to an improved mechanistic elucidation and to the exploration of application opportunities, especially for those in the fluorescence imaging of cells and tissues. There have also been significant advances in the establishment of a shared mechanistic framework for carbon dots and other carbon-based quantum dots, graphene quantum dots in particular. In this article, representative recent studies for more efficient syntheses of better-performing carbon dots are highlighted along with results from explorations of their various bioimaging applications in vitro and in vivo. Similar fluorescence properties and potential imaging uses of some graphene quantum dots are also discussed, toward a more consistent and uniform understanding of phenomenologically different carbon-based quantum dots.