Abstract
<title>Abstract</title> <p>Surface plasmon resonance (SPR) biosensing supports label-free and real-time detection of biomolecular interactions. Infrared (IR) SPR systems enable deeper penetration into biological media and improved coupling with molecular vibrational modes. This work presents a Kretschmann-configured IR SPR biosensor with a multilayer stack composed of barium titanate (BaTiO₃), calcium titanate (CaTiO₃), lead titanate (PbTiO₃), MXene, gold (Au), and strontium titanate (SrTiO₃). The perovskite layers provide high permittivity and ferroelectric response, while MXene contributes electrical conductivity and adsorption sites for analyte interaction.Finite Element Method simulations were carried out in COMSOL Multiphysics to evaluate reflectance, resonance angle, electric field distribution, and sensitivity. Layer thicknesses were varied systematically to determine optimal structural parameters. The optimized configuration achieved a sensitivity of 538.462 °/RIU and a figure of merit of 190.378 RIU⁻¹. The resonance angle showed a linear relationship with analyte refractive index, with R² = 0.96471. The detection limit remained below 0.01 RIU for the tested range. Electric field intensity peaked within an incidence angle range of 77° to 84°, indicating stable plasmon excitation conditions.A Random Forest regression model was applied to predict sensor response across variations in gold layer thickness. The model achieved an average R² of 0.9913, supporting its use for parametric optimization. The results indicate that the proposed multilayer structure enables precise detection of refractive index changes associated with brain tumor biomarkers.</p>