Simultaneous detection of molecules with the surface-enhanced infrared absorption sensor platform based on disk antennas with double spacer

Biomolecule detection has become important in many applications such as medical diagnosis, forensic analysis, basic biological studies, and food quality assessment. In particular, the Mid-infrared range offers an important opportunity for biomolecular sensing as it covers the molecular vibrational spectra of vital biochemicals such as Deoxyribonucleic acid, Ribonucleic Acid, and proteins. In this study, a double band absorbing plasmonic nanoantenna array with two gold disk resonators is proposed. The biosensing ability of this structure was investigated using the protein-goat anti-mouse immunoglobulin G model and Polymethyl methacrylate film. The basic structural bonds of protein monolayer, namely Amide-I, Amide-II, and Amide-III showed vibrational signatures at 6010 nm (similar to 1664 cm(-1)), 6496 nm (similar to 1539 cm(-1)), and 6989 nm (similar to 1431 cm(-1)) wavelengths, respectively. In addition, the spectral response of the proposed antenna structure was investigated using a Polymethyl methacrylate film by detecting the C=O and the C-H bonds. The strong dipole moment at C=O showed a strong absorption deep at 5782 nm (similar to 1730 cm(-1)) while the C-H bond has shown a relatively low absorption deep at 3350 nm (similar to 2985 cm(-1)) and 3395 nm (similar to 2946 cm(-1)). Our findings indicate that the double spacer disk configuration detects the spectral signature of the protein monolayer and Polymethyl methacrylate film in each band, simultaneously. The dual-band can be tuned independently by carefully engineering the radii of the double disks without making an effect on the other band. The proposed structure can be used as a characterization tool for identifying unknown complex molecules by simply detecting their spectral fingerprints in each mode of the dual-band, independently. Also, this design strategy can be insight to multi-mode SEIRA platforms, where more complex chemical molecules are needed to be detected or identified in biology, chemistry, and defense areas.