Plasmonic resonances and hot spots in Ag octopods

TL;DR

This paper investigates silver octopod nanoparticles, revealing their tunable plasmonic resonances and hot spots, which are promising for enhancing surface Raman spectroscopy and can serve as a shape spectroscopy tool.

Contribution

It introduces a detailed analysis of plasmonic resonances in silver octopods, demonstrating their tunability and potential for SERS applications using the discrete dipole approximation.

Findings

Three major resonances can be tuned by geometrical parameters.

Field hot spots exhibit up to 50-fold enhancement.

Resonance behavior is moderately dependent on orientation.

Abstract

New type of plasmonic nanoparticles - silver octopods that can be synthesized with a variety of shapes - have been demonstrated to show versatile optical response using the discrete dipole approximation. The octopods show a complex behavior at optical (visible, IR) wavelengths, with three major resonances that can be tuned up to a desired response that makes them especially attractive to use in e.g. high-performance surface enhanced Raman (SERS) detectors. The excited resonant modes strongly depend on the geometrical parameters of the stars, while dependence on their orientation with respect to an incident radiation is moderate, owing to cubic symmetry. The field "hot spots" are formed with the local field enhancement up to 50 times compared to an incident field. They are usually localized at the surface between the arms and may be both "electric" and "magnetic". While the former are of primary importance for SERS, the latter may be identified by trapping magnetic nanoparticles in their vicinity. The results are in very good agreement with the data where available and may be used as a type of a "shape spectroscopy" for the nanoparticles.