Advances in the syntheses, mechanisms and applications of room-temperature phosphorescent carbon dots†

Research works on carbon dots (CDs) have been increasing at an impressive speed since their discovery in 2004. These carbon nanomaterials possess diverse photochemical/physical properties and favorable attributes, like good biocompatibility, unique optical properties, low cost, abundant functional groups and high stability. Among these properties, room temperature phosphorescence, as a conspicuous property of CDs, has attracted attention from researchers recently. However, compared to those of well-researched organic luminophores and colloid quantum dots, the phosphorescence quantum yield and lifetime of RTP-CDs still have room for improvement. Thus, herein, we offer a forward-looking perspective on this field to comprehend the fundamentals of the phosphorescence in CD systems and propose new opportunities based on the discussion of the inherent structures and luminescence mechanisms of CDs. Considering that the existing reviews on RTP-CDs rarely focus on their phosphorescence mechanisms, we specifically discuss the development of emerging RTP-CDs, focusing on their design strategies, syntheses, fundamental photochemical/physical mechanisms and possible applications. In this review, we highlight the role of the structures of CDs on their optical properties and ways to regulate their essential parameters, including phosphorescence quantum yield, wavelength and lifetime required for their applications. This review will potentially provide some inspiration for future research on RTP-CDs and other luminescent materials.