In recent years, nanomaterials have made an important impact on diverse science, engineering, and commercial sectors due to their high catalysis, low cost, and good stability. Acting as a class of 'zero-dimensional' carbon nanomaterials, carbon dots(CDs) possess unique optical properties of high photostability against photobleaching, tunable excitation and emission wavelength, as well as low cytotoxicity and good biocompatibility. Therefore, CDs have become a hot subject of carbon nanomaterial in the past decade, not only for its unique properties but also for its applications in various fields such as bioimaging, biolabeling, sensors, photocatalysis, solar cells, light-emitting element and so on. This article reviews the different synthetic methodologies(including two classes: top-down and bottom-up) to achieve good performance of CDs. At the same time, the applications of CDs are also reviewed in the article.

Contents
1 Introduction
2 Synthesis methods of carbon dots
2.1 Top-down methods
2.2 Bottom-up methods
3 Applications of carbon dots
3.1 Bioimaging and Biolabeling
3.2 Sensors
3.3 Photocatalysis
3.4 Solar cells
3.5 Light-emitting diodes
4 Conclusion