Carbon dots are the most popular nanomaterials in recent years among the nanocarbon family, including fullerene, the carbon nanotube and graphene. This kind of nanomaterial has successfully overcome some defects of traditional semiconductor quantum dots. It is highly evaluated not only for the excellent optical performance and small size effect, but also the great biocompatibility and ease to achieve surface functionalization. Carbon dots can be widely used in the field of biochemical sensing, fluorescent probes, environmental testing, photocatalytic technology, drug carriers and so on. In this review, the progress made in the field of carbon dots in recent years, especially in latest developments of applications are reviewed, the characteristics of carbon dots are outlined, the problems remaining to be solved are summarized and the further advances are prospected.

Contents
1 Introduction
2 Properties of the carbon dots
2.1 Optical property
2.2 Low toxicity and biocompatibility
3 Preparation of carbon dots
4 Application of carbon dots
4.1 Detection probes
4.2 Bioimaging
4.3 Light-emitting element
4.4 Photocatalysis
4.5 Drug carriersis
5 Conclusions and perspectives