Simulation of the medium dielectric constant dependent optical properties for gold nanorods

Suspended gold nanorods were synthesized via electrochemical method. UV-Visible spectra and fluorescence emission spectra were measured at room temperature. Numerical calculations based on quasi-static and scattering theories were developed to describe these observed optical properties. Because of the anisotropy of the gold nanorods, both absorption features and scattering features show two peaks, which result from the transverse and longitudinal surface plasmon resonances respectively. Furthermore, with increasing the dielectric constant of surrounding medium from 1.5 to 2.5, these two absorption peaks increase and red shift in a nonlinear way together. However, the scattering peak at the shorter wavelength depends on the surrounding medium dielectric constant in a linear fashion, and the other scattering peak at the longer wavelength decreases and red shifts nonlinearly.