Band-Edge Bilayer Plasmonic Nanostructure for Surface Enhanced Raman Spectroscopy

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 the Raman spectroscopy of proteins can be used to diagnose several diseases, including a few types of cancer. The development of the assays based on surface enhanced Raman spectroscopy (SERS), which are 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 SERS, 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.

Light-Directed Reversible Assembly of Plasmonic Nanoparticles Using Plasmon-Enhanced Thermophoresis

“…Exploiting the plasmon-enhanced electromagnetic field at plasmonic nanostructures, SERS is an advanced analytical technique that can detect molecules with a sensitivity down to the single-molecule level. − A number of approaches have been implemented to enhance the localized electromagnetic field and improve the SERS sensitivity, including tailoring the particle shape ,, and inducing near-field coupling. ,− The integration of optical tweezers with SERS (also known as SERS tweezers) is applied for analyzing biomolecules in their native environments and developing optofluidics-based lab-on-a-chip systems. − However, the high optical power required for nanoparticle manipulation in optical tweezers can potentially damage the biomolecules, which limits the applications of SERS tweezers.…”

Plasmonic nanohole array for enhancing the SERS signal of a single layer of graphene in water

“…In this sample the SERS signal of the SLG is enhanced through two physical processes of excitation rate enhancement and emission efficiency enhancement as follows 22 , 34 , 52 – 54 : Here γ is the SERS signal enhancement. The excitation rate enhancement Γ exc is defined as the enhancement in the light absorption in the SLG on the plasmonic nanohole array substrate covered with either air or water at the pump laser wavelength, compared with the absorption in the SLG on glass substrate, that is: where ( P abs ) g , ( P abs ) a and ( P abs ) w are the absorbed electromagnetic power in the SLG on glass substrate, in the SLG on plasmonic nanohole array substrate covered with air, and in the SLG on plasmonic nanohole array substrate covered with water, respectively.…”

“…The Raman signal of molecules is strongly enhanced when they are adsorbed on the surface of metallic nanostructures, which exhibit local surface plasmon resonances. This SERS effect originates in the giant enhancement of the local electromagnetic field at the pump laser wavelength 19 – 23 and of the local density of optical states (LDOS) at the Raman emission wavelengths 24 – 26 in hotspots, due to surface plasmon resonances of the metallic nanostructures to which the target molecules are adsorbed 14 , 27 – 34 . Owing to its ultra-high sensitivity, SERS has shown promise as a powerful tool for chemical identification with applications in biochemistry, food sciences, environmental studies and forensics 35 .…”