Single Anisotropic Plasmonic Nanoparticle Three-Dimensional Orientation Determination Based on Fano-Like Resonance and Universal 3D Orientation-Dependent Scattering Trait

Abstract

Single-nanoparticle orientation determination plays a vital role in studying complex nanoscale motion. In the present paper, we systematically investigate the three-dimensional (3D) orientation-dependent far- and near-field optical properties of single (Au core)-(dielectric shell) nanorice and gold nanorod. It shows that the scattering spectrum of the single anisotropic nanoparticle with arbitrary orientation is a linear superposition of a set of basic scattered spectra. And the scattering spectra of the single nanorice show a polarization-dependent Fano-like resonance which can be well described by a model with two coupled oscillators. Furthermore, by means of coordinate transformation, a universal analytic formula for description single nanoparticle 3D orientation- and polarization- dependent scattering intensity is proposed. Then we develop a new method to detect the 3D orientation of single nanoparticle, that is, by fitting the scattering intensity under different incident polarization directions based on our analytic formula and the 3D orientations could be resolved explicitly. Both of the experimental and numerical simulation data can be well described by our analytical formula. Our method for single particle 3D orientation determination has high precision only with subdegree uncertainty. In addition, based on the Fano resonances caused by the efficient coupling between the dielectric elliptical shell and the gold nanoellipsoid core, we found that the 3D orientation of single nanorice could be confirmed from either the transverse or longitudinal plasmon mode polarization-dependent scattering trait, while it is almost impossible for single gold nanorod based on the transverse plasmon mode. It is worth noting that the transverse plasmon mode of the nanorice is mostly insensitive to the aspect ratio then it allows nanorices with different lengths to be 3D orientation sensors without altering the incident laser wavelength.