Free-standing gold elliptical nanoantenna with tunable wavelength in near-infrared region for enhanced Raman spectroscopy

Abstract

The purpose of this work is to present a surfaceenhanced Raman scattering (SERS) amplifying antenna for the possible usage in the near-infrared region. Instead of the visible-light range amplifying antenna such as a bowtie, the finite-difference time-domain (FDTD) simulation results indicate that elliptical antenna could provide large electromagnetic field enhancement at near-infrared wavelength by combining the free-standing enhancement property with large aspect ratios of the ellipse geometry. The simulation results consist with the enhancement factors characterized by SERS measurements at the excited wavelength of 785 nm for different aspect ratios and periodicities. In addition to the redshift of the resonance wavelength as the aspect ratio of ellipse increases, the freestanding structure modifies the resonance behavior and the dielectric environment of antenna by elevating the elliptical disk from the substrate. To interpret the simulation results, the analytical solution of resonance wavelength for ellipsoid dimmer is derived based on Lorentz-Mie theory, and comparisons are made between the analytical solution and simulation results. The quasi-static analytical solution provides a way to characterize the resonance behavior of two ellipsoid particles as a function of the gap distance, aspect ratio, and dielectric environment. The electrodynamic analysis for the periodic structure was performed in our FDTD simulations.

Optical Fiber, Nanomaterial, and THz-Metasurface-Mediated Nano-Biosensors: A Review

“…Bowtie antenna has shown highly encouraging results in terms of biological sensing and nano-optic applications [ 144 ], bioinspired surfaces and dielectric metamaterials [ 145 ], and polarimetric optical biosensing [ 11 ]. Elliptical nano shaped antennas showed promising results for near-field scanning optical microscopy [ 22 , 146 ]. Researchers have also designed a gold nano star for a number of applications, such as HeLa cells transfection with PGFP under optimized conditions [ 147 ], singlet oxygen production [ 148 ], early cancer detection [ 149 ], tumor detection and killing [ 150 ], and photothermal therapy/targeted drug delivery and anti-tumor/anti-bacterial devices [ 151 ].…”

All-Opto Plasmonic-Controlled Bulk and Surface Sensitivity Analysis of a Paired Nano-Structured Antenna with a Label-Free Detection Approach

“…The above discussions show the promising results of strong resonance and field confinement through numerical modelling and experimental investigations. Recently, the numerical design and simulation of gold nanoantennas was modelled by a computationally efficient Finite Element Method (FEM) [8,11,18,19,30,31] and the versatile Finite Difference Time Domain method (FDTD) [32][33][34][35][36].…”

Sensitive SERS detection at the single-particle level based on nanometer-separated mushroom-shaped plasmonic dimers

“…The key technique in the fabrication of such kinds of elevated plasmonic dimers is the preparation of three-dimensional (3D) templates for the followed metal deposition. Currently, a common fabrication approach is achieved by combining electron-beam lithography (EBL) with isotropic reactive ion-etching (RIE) techniques [19,[22][23][24][25][26][27]. However, this 3D fabrication process is complicated and time-consuming because it evolves RIE process which is difficult to control and has to be carefully optimized for customized applications.…”