We show for the first time that stable fluorescent vesicles can be constructed by mixing oppositely-charged carbon quantum dots (CQDs) and simple surfactants in water, and can be potentially used as a new generation of biomarkers and drug delivery vehicles.

Carbon quantum dots (CQDs) have emerged as a new generation of photoluminescent nanomaterials with wide applications. Among the various synthetic routes for CQDs, the acid-refluxing method, which belongs to the group of "top-down" methods, offers the advantage of large-scale production of CQDs and uses cheap and abundantly available starting materials. In this study, we evaluated the potential of fullerene carbon soot (FCS), a by-product obtained during the synthesis of fullerene, as the starting material for CQD production. It was found that FCS can be successfully converted to CQDs in high production yield in mixed acids, i.e., concentrated HNO3 and H2SO4, under mild conditions. The fluorescence quantum yield (Φ) of the as-produced CQDs is in the range of 3%-5%, which is the highest value for CQDs obtained from "top-down" methods. Importantly, the CQDs prepared by this method show emission in the yellow range of the visible light, which is advantageous for their various potential applications. Further investigations reveal that the CQDs are highly photostable over a wide pH range and show good resistance against ionic strength and long-term UV irradiation. This further expands their potential use under harsh conditions.