Study of Plasmonic Properties of Gold Nanoparticles of Different Shapes with emphasis on Gold Nanopyramids

We present a study of gold nanopyramids and their optical properties. A comparison with the extinction properties of gold nanorods and nanocubes is also undertaken. The Finite Difference Time Domain (FDTD) method is used for the study of optical properties. The nanopyramids display a dual plasmon resonance when excited with a perpendicularly polarized signal due to the excitation of dipole and quadrupole modes. The quadrupole modes are not strongly affected by changing the height of the nanopyramids whereas the dipole mode is redshifted with increasing the height of the nanopyramids. The quadrupole mode could be of interest in some applications where the shorter wavelength resonance is desired. The quadrupole and dipole modes are located at 620 nm and 765 nm respectively. This band is used for both intensity and wavelength modulated biosensors. Furthermore, the electric field is enhanced in the case of the nanopyramids which is considered as another advantage in sensing and surface enhanced Raman scattering (SERS) applications.