Preparation and plasmon resonance properties of Au nanorods and Aunanorods@SiO2

Au nanorods were prepared through seed growth method. Their lengths and diameters were controlled by adjusting Ag⁺ content in the growth solution. Ethyl orthosilicate were hydrolyzed in alkali solutions to obtain SiO₂-coated Au nanostructures. Au nanorods with ideal morphologies and sizes could only be obtained under the presence of a certain Ag⁺ concentration in the growth solution. Without Ag⁺, only some irregular nanoparticles were generated without nanorods. Longitudinal plasma absorption of Au nanorods shifts first to red shift and then to blue with the increase of Ag⁺ in the growth solution, while transverse plasma absorption hardly changes. However, longitudinal plasma absorption of silica-coated Au nanorods has a blue shift with the increase of the thickness of silica, while the transverse plasma has a slight red shift. Therefore, by coating Au nanorods with silica and by adjusting their aspect ratio by using different Ag⁺ concentration in the growth solution, Au nanoparticles can be synthesized for applications requiring absorption in specific UV regions.