Impact of Metal-Optical Properties on Surface-Enhanced Infrared Absorption

Abstract

Surface-enhanced infrared absorption (SEIRA) spectroscopy using resonant metallic nanostructures is increasingly attracting interest during the last decade. Nevertheless, the impact of the metals' intrinsic properties on SEIRA is still little studied. We present an experimental work on this topic, examining the infrared-optical resonance spectra of linear nanoantennas made of five of the most common metals (gold, silver, copper, aluminum, and iron) with respect to the intrinsic and radiation damping. Highly material-and sizedependent ratios of the two damping contributions were found and discussed. Using layers of organic probe molecules, we obtained SEIRA enhancement factors for the different nanoantennas and experimentally verified the predicted relationship between the plasmonic damping mechanisms and the SEIRA enhancement. The multitude of our experimental data for the ratio between the intrinsic electronic damping and the radiation damping is compared with the measured SEIRA enhancement of the various nanoantennas and therefore deliver the proof that the best SEIRA enhancement is achieved when both damping mechanisms equally contribute. Furthermore, it is shown that for a given nanoantenna geometry, the red-shift away from the plasmonic extinction maximum is strongly dependent on material parameters.

Self-Organized Nanorod Arrays for Large-Area Surface-Enhanced Infrared Absorption

“…Under this assumption, we found that the characteristic enhancement factor of the resonant nanorod antennas (sample B) reads EFeff ≅ 55000. We stress that this figure is competitive with the efficiency of lithographic nanoantenna arrays, [ 62,63 ] even though EFeff is here underestimated.…”

Present and Future of Surface-Enhanced Raman Scattering

“…This maximum enhancement is the highest possible if the absorption cross section of the plasmonic structure is equal to the cross section for radiation scattering . Such a situation can be reached with geometrically optimized structures and low electronic damping (perfect crystallinity) of the metal, as shown by measurements and simulations for linear nanoantennas (Figure ). Then, in SEIRA based on IR extinction measurements, extraordinarily enhanced vibrational signals show up, because the vibrational absorption strongly modulates the IR light scattering of the plasmonic system …”

“…Bigger enhancement with Cu, Ag, and Au antennas is attained because of the lower electronic damping. Reproduced from ref . Copyright 2018 American Chemical Society.…”

Silver Amalgam Nanoparticles and Microparticles: A Novel Plasmonic Platform for Spectroelectrochemistry

“…Each of them is dominated by a broad peak at mid-infrared (MIR) wavelengths, the distinctive evidence of MIR plasmonic resonances. 47,48 With the increasing average AgA particle size, there is also a characteristic gradual red shift of the resonance frequency, in accordance with the theoretical expectations. 49 Note that the resonances with the highest quality factors can be observed on the samples with intermediate growth times (samples b−d).…”