Spectral Tuning of Gold Nanoparticles Embedded in Dielectric by Changing Anisotropy and Interparticle Interaction: A Mathematical Correlation between the Shape and Interaction

The theoretical studies of optical absorption (OA) properties of anisotropic non-interacting Au nanoparticles (NPs) and the spherical interacting Au NPs embedded in dielectric matrix have been carried out separately. For the studies we have considered a modified Garcia et al. model depend on Maxwell-Garnett (MG) theory where anisotropy of the particles are represented by a parameter β known as shape parameter and interaction is represented by the parameter K. For calculation of OA spectra of anisotropic particles, the values of β is varied from 0.05 to 1.0, considering K = 0 and keeping particle radius fixed at R = 2 nm. The OA spectra of anisotropic Au NPs in the above range of β exhibit a large redshift of surface plasmon resonance (SPR) from 500 - 832 nm in contrary to what is observed for spherical non-interacting particle of same size at an around 520 nm. An exponential type decay of SPR peak position with increase of β has also been observed. The almost similar nature of OA spectra and the decay behavior of the SPR peak with decrease of K have also been observed for interacting spherical Au NPs by varying the interaction parameter K from 20 to 80 of same particle size. The observation gives a correlation between the parameter β and K which was not established. This correlation is essential and helpful for different applications of anisotropic Au nanoparticles in plasmonic, surface enhanced Raman scattering (SERC), photonics, optoelectronics, and others.