Highly Sensitive Plasmonic Au Bowtie Sensors with Extraordinary Optical Absorbance for SERS Applications

Surface-enhanced Raman spectroscopy (SERS)–based technologies have made tremendous development in biomolecule detections in recent years. In this research work, three-layered systems containing two mirrored isosceles triangular Au nanostructures named plasmonic bowties are simulated in COMSOL Multiphysics for its applications in surface plasmon resonance biosensing. The impact of geometrical parameters, i.e., size, thickness, nanogap, incident angle, TE polarization, and periodicity, is optimized in the RF module. Au bowties show well-regulated light–matter interaction employing enhanced surface plasmon polaritons along the edges of bowties when operated at 480–540 nm incident wavelength with an optimal 40-nm gap. Absorbance up to 99% for normal incidence and 88% for 45° incident angle is obtained while the return loss plots show stronger resonance behavior for normal incidence as compared to 45° angle. An outstanding value of SERS enhancement factor (EF) up to \(1.95\times {10}^{4}\) $1.95\times {10}^4$ at normal incidence is achieved which is 25 times higher as compared to \(7.8\times {10}^{2}\) $7.8\times {10}^2$ at 45° incident angle. A maximum sensitivity response of 4307.77 nm/RIU at normal incidence and 4104.44 nm/RIU at 45° incident angle is evaluated. Q value of 6.01 and figure of merits (FOM) of 49.74 are calculated for normal incidence, although for a 45° incident angle, Q value of 4.09 and FOM of 33.58 are observed. A comprehensive analysis of absorption, return loss, SERS EF, sensitivity, Q factor, and FOM of the proposed plasmonic Au bowtie indicates its suitability for highly sensitive biosensing devices, photonic devices, chemical industry, food safety, and light energy harvesting applications.