Gold nanorods have caused much attention due to their unique physical properties. Nowadays, gold nanorods have created a great promise for their use in nanoelectronic, optical and biomedical applications. By adjustment of experimental conditions, the morphology, size and aspect ratio of gold nanorod can be finely controlled, which finally affect the physical properties of gold nanorods. In this review, the various synthesis methods of gold nanorods, such as template method, electrochemical synthesis method, seeded growth method and even recently developed seedless growth method are summarized. The effects of experimental conditions on the crystal structures and physical properties of gold nanorods are discussed in detail, along with the recent research progress on the growth mechanism of single-crystalline and pentahedrally-twinned nanorods. Finally, general strategies to improve the purity of product are provided.

Contents
1 Introduction
2 Synthesis of gold nanorods
2.1 Template method
2.2 Electrochemical synthesis
2.3 Seeded growth method
2.4 Seedless growth method
3 Crystal structure and growth mechanism
3.1 Crystal structure
3.2 Growth mechanism
4 Purification
5 Conclusion