Tuning of Plasmonic Response in High Aspect-Ratio Au Nanowires through Laser Irradiation: A TEM-EELS Study

Surface enhanced infrared absorption mechanism and modification of the plasmonic response

“…The electromagnetic response of the gold nanorods in the IR is due to the plasmon resonance that can be described, for an infinite nanorod, by the azimuthal number m and the wavevector along the nanorod axis [30]. For finite nanorod of length L, the wavector is quantified (k = nπ /L) and the m = 1 mode is excited by light polarized perpendicular to the nanorod axis and the m = 0 mode for parallel polarization [31].…”

“…For the gold nanorod, we derived the local polarizability from lattice dispersion relation, which is a correction of Clausius-Mossotti's formula [26], from the experimental bulk refractive index [29]. The simulations have been performed with the DDSCAT code [26] In our simulations, we consider nano-rods with a 30 nm diameter and a length of 900 nm, modeled by 199 680 dipoles placed on a cubic grid with a periodicity of 1.875 nm, ensuring the convergence (see also [30] for an investigation of the response of similar nano-object by DDA).…”

“…For practical reasons, the metallic plasmonic system will be kept fixed in the following, while the molecular mode will be tuned. Note that the optical resonance of a nanorod can be modified thanks to LASER engraving [30]. The molecules are modeled by 88 dipoles dispersed in the gap with a distance of at least 3.25 nm with their closest neighbor which diminishes self-interacting phenomenon.…”