Enhanced Molecular Infrared Spectroscopy Employing Bilayer Graphene Acoustic Plasmon Resonator

Abstract

Graphene plasmon resonators with the ability to support plasmonic resonances in the infrared region make them a promising platform for plasmon-enhanced spectroscopy techniques. Here we propose a resonant graphene plasmonic system for infrared spectroscopy sensing that consists of continuous graphene and graphene ribbons separated by a nanometric gap. Such a bilayer graphene resonator can support acoustic graphene plasmons (AGPs) that provide ultraconfined electromagnetic fields and strong field enhancement inside the nano-gap. This allows us to selectively enhance the infrared absorption of protein molecules and precisely resolve the molecular structural information by sweeping graphene Fermi energy. Compared to the conventional graphene plasmonic sensors, the proposed bilayer AGP sensor provides better sensitivity and improvement of molecular vibrational fingerprints of nanoscale analyte samples. Our work provides a novel avenue for enhanced infrared spectroscopy sensing with ultrasmall volumes of molecules.

Recent advances in nanostructured substrates for surface-enhanced infrared absorption spectroscopy

“…Here, tetraethyl orthosilicate, triethyl phosphite, and calcium nitrite were used as precursors to obtain a stable and uniform sol, which is the key of the sol-gel process. The electrospun silica-hydroxyapatite fibers [183]. Reproduced from [183] with permission from MDPI, copyright 2021.…”

“…The chemical vapor deposition method is a commonly used approach to make thin film materials; this method refers to a preparation process where gaseous reactants are chemically reacted on the surface of a solid substrate at high temperatures, and then deposited into a solid material. As reported in Wen et al's study, monolayer graphene deposited on copper foil was prepared by a chemical vapor deposition method and subsequently used in a SEIRA spectroscopy study [183] (figure 5(e)). This method also plays an important role in the preparation of semiconductor nanostructured substrates; for instance, Baldassarre et al deposited an epitaxial Ge layer on a silicon wafer by a chemical vapor deposition method, then combined with electron-beam lithography and reactive ion etching processes to prepare Ge nanoantenna arrays.…”

“…Reproduced from [212] with permission from De Gruyter, copyright 2018. (e) Schematic diagram showing chemical vapor deposition preparation of graphene for MIR plasma resonator research[183]. Reproduced from[183] with permission from MDPI, copyright 2021.…”

“…(e) Schematic diagram showing chemical vapor deposition preparation of graphene for MIR plasma resonator research[183]. Reproduced from[183] with permission from MDPI, copyright 2021. (f) Schematic illustration showing the preparation of bow tie-shaped Au nanoantennas using nanosphere lithography with two different deposition angles[213].…”