Due to its unique physical and chemical properties and promising widespread application value, graphene has been attracting intensive research interest. However, it has been limited the applications in the field of optoelectronics due to its special structure of zero bandgap. Semiconductor quantum dots (QDs) exhibit the fascinating optical properties associated with its special quantum size effect. They have been successfully applied in biological detection and optoelectronic applications. But the recombination and annihilation between the electrons and the holes greatly restrict the QDs application in optoelectronic conversion because it lowers the electron conductivity and mobility. The special electronic properties and structures of graphene make it an excellent conductive scaffolds, which would capture and transport electrons from the excited QDs and also effectively separate the electron-hole pair. Therefore, graphene-QDs composites would be an good candidate for combining the advantages of two materials. Graphene-QDs composites not only inherit the high speed electron transport property of the intrinsic graphene, but also possess the quantum size effect and edge effect origining from the special structure of QDs, suggesting the potential applications in the fields of nanodevices and optoelectronics. In this paper, we summerized the synthetic methods of graphene-QDs composites, including the phase-transfer methods, electrostatic compound strategies, hydrothermal and solvothermal methods, electrochemical template method and the microwave-assisted ways. The brief introduction of the applications has also been presented, which would provide the reference for the research and development of graphene-based nanocomposites.

Contents
1 Introduction
2 Synthesis of graphene-quantum dot composites
2.1 Phase-transfer methods
2.2 Electrostatic compound strategies
2.3 Solvothermal methods
2.4 Hydrothermal methods
2.5 Electrochemical template method
2.6 Microwave-assisted ways
3 Applications of graphene-quantum dot composites
3.1 The applications in optoelectronic devices of graphene-quantum dot composites
3.2 The applications in photocatalysis of graphene-quantum dot composites
3.3 The applications in biosensing of graphene-quantum dot composites
4 Conclusion and outlook