Design and numerical evaluation of a high sensitivity plasmonic biosensor based on MISM nanoring for versatile virus detection.

Recent advancements in nanotechnology have positioned plasmonic optical sensors as powerful tools for biosensing applications. These sensors utilize the interaction of electromagnetic waves with metallic nanostructures to enable rapid, label-free detection of biological analytes. In this study, we propose and optimize a plasmonic optical biosensor based on nanohole arrays and metal-insulator-semiconductor-metal (MISM) nanorings for detecting various viruses. The sensor structure incorporates gold and silver layers on a silver substrate, with the nanohole and nanoring elements engineered to enhance sensitivity to refractive index variations in the surrounding medium. The finite-difference time-domain (FDTD) method evaluates the sensor's performance, which numerically solves Maxwell's equations for frequency-dependent optical behavior. Simulation results demonstrate the sensor's capability to detect minute refractive index changes induced by viruses such as HSV, HIV-1, Influenza A, and M13 bacteriophage. The design achieves a high sensitivity of 811 nm/RIU, attributed to Fano resonance effects and optimized geometrical parameters. Furthermore, the sensor exhibits a figure of merit (FOM) of 3.38 RIU⁻¹ and a limit of detection (LoD) of 0.268 RIU, outperforming many previously reported plasmonic biosensors. These findings underscore the potential of nanohole-MISM nanoring-based plasmonic sensors for rapid, label-free, and highly sensitive virus detection. With further development in structural design and fabrication techniques, this platform could be widely applicable in medical diagnostics and point-of-care biosensing.