Lattice Rayleigh Anomaly Associated Enhancement of NH and CH Stretching Modes on Gold Metasurfaces for Overtone Detection
School of Photonics, Center of Information Optical Technology, ITMO University, 49 Kronverksky pr., St. Petersburg 197101, Russia
School of Electrical and Computer Engineering, Ben-Gurion University of the Negev, Beer-Sheva 8410501, Israel
Authors to whom correspondence should be addressed.
Nanomaterials 2020, 10(7), 1265; https://doi.org/10.3390/nano10071265
Received: 25 May 2020 / Revised: 10 June 2020 / Accepted: 17 June 2020 / Published: 29 June 2020
(This article belongs to the Special Issue Electronic and Optical Properties of Nanostructures)
Molecular overtones stretching modes that occupy the near-infrared (NIR) are weak compared to the fundamental vibrations. Here we report on the enhancement of absorption by molecular vibrations overtones via electromagnetic field enhancement of plasmonic nanoparallelepipeds comprising a square lattice. We explore numerically, using finite element method (FEM), gold metasurfaces on a transparent dielectric substrate covered by weakly absorbing analyte supporting N-H and C-H overtone absorption bands around 1.5
m and around 1.67 m, respectively. We found that the absorption enhancement in N-H overtone transition can be increased up to the factor of 22.5 due to the combination of localized surface plasmon resonance in prolonged nanoparticles and lattice Rayleigh anomaly. Our approach may be extended for sensitive identification of other functional group overtone transitions in the near-infrared spectral range.