Band-edge Bilayer Plasmonic Nanostructure for Surface Enhanced Raman Spectroscopy

TL;DR

This paper introduces a bilayer plasmonic nanostructure that enhances surface-enhanced Raman spectroscopy (SERS) for analyzing large biomolecules, enabling more sensitive and uniform detection of proteins like streptavidin.

Contribution

The study presents a novel bilayer nanoantenna array that simultaneously adjusts lattice and localized surface plasmons to achieve high, uniform SERS enhancement for large biomolecular analysis.

Findings

Achieved high SERS enhancement with the bilayer nanostructure.

Demonstrated selective protein detection at low concentrations.

Provided uniform enhancement across the sensing area.

Abstract

Spectroscopic analysis of large biomolecules is critical in a number of applications, including medical diagnostics and label-free biosensing. Recently, it has been shown that Raman spectroscopy of proteins can be used to diagnose some diseases, including a few types of cancer. These experiments have however been performed using traditional Raman spectroscopy and the development of the Surface enhanced Raman spectroscopy (SERS) assays suitable for large biomolecules could lead to a substantial decrease in the amount of specimen necessary for these experiments. We present a new method to achieve high local field enhancement in surface enhanced Raman spectroscopy through the simultaneous adjustment of the lattice plasmons and localized surface plasmon polaritons, in a periodic bilayer nanoantenna array resulting in a high enhancement factor over the sensing area, with relatively high uniformity. The proposed plasmonic nanostructure is comprised of two interacting nanoantenna layers, providing a sharp band-edge lattice plasmon mode and a wide-band localized surface plasmon for the separate enhancement of the pump and emitted Raman signals. We demonstrate the application of the proposed nanostructure for the spectral analysis of large biomolecules by binding a protein (streptavidin) selectively on the hot-spots between the two stacked layers, using a low concentration solution (100 nM) and we successfully acquire its SERS spectrum.