Abstract
Surface enhanced infrared absorption (SEIRA) spectroscopy and surface plasmon resonance (SPR) make possible, thanks to plasmonics nanoantennas, the detection of low quantities of biological and chemical materials. Here, we investigate the infrared response of 2,4-dinitrotoluene deposited on various arrays of closely arranged metal-insulator-metal (MIM) resonators and experimentally show how the natural dispersion of the complex refractive index leads to an intertwined combination of SEIRA and SPR effect that can be leveraged to identify molecules. They are shown to be efficient for SEIRA spectroscopy and allows detecting of the dispersive explosive material, 2,4-dinitrotoluene. By changing the in-plane parameters, a whole spectral range of absorptions of 2,4-DNT is scanned. These results open the way to the design of sensors based on SEIRA and SPR combined effects, without including a spectrometer.
Highlights
Spectroscopy is a widely used technique to identify molecules thanks to their absorption wavelengths, which, each associated with a given bandwidth, are a unique and recognizable fingerprint of the molecules [1]. These absorption bands can be further increased if the molecules are placed in the neighborhood of a metallic surface or a resonant nanostructure that increases the electric field surrounding the targeted molecules [2]. This is referred in the community as surface enhanced infrared absorption spectroscopy (SEIRA), and its sensitivity depends on the molecule absorption peak and bandwidth, and on its amplitude [3]
We study the infrared response of 2,4-dinitrotoluene deposited on various arrays of closely arranged MIM resonators, and experimentally show how the natural dispersion of the complex refractive index leads to an intertwined combination of Surface enhanced infrared absorption (SEIRA) and surface plasmon resonance effects (SPR) effect that can be leveraged to identify molecules
We demonstrate the use of closely arranged MIM resonators to detect 2,4-DNT
Summary
Spectroscopy is a widely used technique to identify molecules thanks to their absorption wavelengths, which, each associated with a given bandwidth, are a unique and recognizable fingerprint of the molecules [1]. We study the infrared response of 2,4-dinitrotoluene deposited on various arrays of closely arranged MIM resonators, and experimentally show how the natural dispersion of the complex refractive index leads to an intertwined combination of SEIRA and SPR effect that can be leveraged to identify molecules. This specific resonator geometry exhibits a high and homogeneous enhancement factor in the whole volume of its slits, which can be increased as well as the resulting SEIRA signal without significant change of the enhancement factor. We take advantage of the ability to adjust the resonant wavelength by changing the in plane parameters of the MIM resonator to introduce a multiple resonator device, which could be used in a more sophisticated sensor to increase the specificity of detection, decreasing false alarms
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