Publication

Abstract : Fano resonance (FR) offers sharp asymmetric line shapes with steep spectral gradients, enabling highly sensitive refractive-index (RI) detection. In this work, we present a plasmonic FR-based progesterone sensor that integrates a circular metal–insulator–metal (MIM) cavity with a cerium oxide nanoparticle (CEN) layer. The incorporation of CEN introduces a distinct novelty: its high dielectric constant, oxygen-vacancy–driven charge transfer, and exceptional chemical and thermal stability significantly enhance near-field confinement, resonance sharpness, and environmental robustness compared to conventional sensors that rely solely on noble metals or graphene. Finite-difference time-domain (FDTD) simulations demonstrate an intensity sensitivity of 300%/RIU, a figure of merit of 30 RIU⁻¹, and excellent linearity (R² = 0.9935), confirming the strong RI responsiveness of the proposed design. The enhanced FR profile enables detection of minute RI variations relevant to hormone-level monitoring. With its compact footprint, fabrication-feasible dimensions, and compatibility with surface functionalization, the CEN-enhanced FR–MIM sensor provides a pathway for stable, miniaturized, and reliable hormonal diagnostics, establishing a foundation for next-generation plasmonic biosensing platforms.