Comparison of Surface Plasmon Excitation by Light and Electrons in Gold Nanorods

Surface plasmons resonance is the most prominent optical property of metal nanostructures, which consists of oscillation of the free electron cloud excited by an incident electromagnetic field. To achieve its excitation, it can be made by electromagnetic radiation incidence or through charged particles. The technique for studying electron excitation is known as electron energy loss spectroscopy (EELS), which is coupled to transmission electron microscopes. Through this research, it is desired to compare, both by numerical simulations, and by experimental techniques of UV-Visible spectrophotometry and EELS spectroscopy, the characteristics of this type of excitation in gold nanorods. Matlab software with the MNPBEM package was used to perform numerical simulations, which is based on the boundary element method to solve Maxwell's complete equations and know the spectra and charge distributions in nanoparticles under light and electron excitation. The experimental study was performed on gold nanorods samples of approximately 38 nm in length and 10 nm in diameter. The results obtained by UV-Visible spectrophotometry show a longitudinal and a transverse mode while the EELS spectra shows the excitation of the dipolar longitudinal mode and higher order modes.