Advances in carbon dots: from the perspective of traditional quantum dots

Quantum dots (QDs) have been the core concept of nanoscience and nanotechnology since their inception, and play a dominant role in the development of the nano-field. Carbon dots (CDots), defined by a feature size of <10 nm, have become a rising star in the crossover field of carbon materials and traditional QDs (TQDs). CDots possess many unique structural, physicochemical and photochemical properties that render them a promising platform for biology, devices, catalysis and other applications. However, due to the complex nature of CDots, to gain a profound understanding of the physical and chemical properties of CDots is still a great challenge. Many key issues including structure, synthesis, and optical properties are unclear, leaving open arguments and nonuniform description of their basics. The achievements and experience of TQDs in the past four decades are expected to provide crucial values for further development of CDots. Here, we will compare the research outputs of TQDs and CDots and try to give a comprehensive picture of their differences and correlations in structure, synthesis, properties and applications. Along this line, further perspectives are given on future directions and key issues toward a better understanding of the basic properties of TQDs and CDots in a unified manner. We expect the researchers in the community to foresee the great potential of CDots, and focus on the critical results obtained during the development of TQDs, paying special attention to the profound principles behind the synthetic chemistry, luminescence mechanisms and applications.