Synthesis of Gold nanostructure
There are many key factors besides the lattice of positive ions, that affect the plasmon absorption of nanoparticles, such as: size, shape, mutual nanoparticles’ positions, surface chemistry, and chemical environment. [18] Therefore, compared to other top-down approach, chemical synthetic method, especially colloidal synthesize method, as a bottom-up approach to the noble metal nanostructure, has many advantages which are crucial to the plasmonic nanomaterials, such as low cost, well-controlled size distribution, post synthesis separation, etc. For gold nanoparticle, typically, in aqua solution, the most common method is seed growth methods. In general, these methods use strong reductant agent to synthesize the seed nanoparticles (typically 1-10 nm), and use mild reductant agent to slowly grow the seed nanoparticles into the desired sizes (5 nm - 300 nm) or shapes (nanosphere, nanorods, nanoprisms, etc). [20-22]