Preparation of AucoreAgshell Nanorods and Characterization of Their Surface Plasmon Resonances

The surface of gold nanorods is coated with thickness-controlled silver by reducing AgCl 4 3- exclusively on the metallic surface to form Au core Ag shell nanorods and then restored by selectively removing the silver coating. Au core Ag shell nanorods show much sharper, stronger, and shorter-wavelengthed surface plasmon absorption than gold nanorods. However, the absorption wavelength is much longer than the one calculated for pure Ag nanorods. This means that the core−shell structure of Au core Ag shell nanorods must be explicitly taken into account in these calculations.