Enhanced plasmonic biosensing using SiO 2 and FASnI 3 perovskite in a multilayer SPR structure for cancer diagnostics

This study presents a high-performance multilayer surface plasmon resonance (SPR) biosensor for the label-free detection of cervical cancer cells. The proposed configuration, BK7/SiO 2 /Ag/FASnI 3 /black phosphorus (BP), utilizes the synergistic functions of a dielectric spacer (SiO 2 ) and a tin-based halide perovskite (FASnI 3 ) to improve plasmonic coupling and sensing accuracy. The transfer matrix approach models angular reflectivity at 633 nm and assesses the impact of FASnI 3 and SiO 2 thickness on resonance behavior, sensitivity, and quality factor (QF). The use of FASnI 3 over Ag significantly enhances field confinement, yielding a sensitivity of 352.5 ∘ /RIU and a QF of 92.76RIU −1 for differentiating between healthy and malignant HeLa cells. Increasing the SiO 2 layer thickness to 10 nm improves sensitivity to 363.75°/RIU, with a corresponding QF of 80RIU −1 and an angular shift of 8.73° between healthy and malignant cells. These values exceed those of many recent Au, BaTiO 3 , and ZnSe-based SPR setups, indicating an estimated 34%–50% enhancement in sensitivity. In comparison to KSnI 3 and CsSnI 3 , FASnI 3 offers enhanced optical confinement and more significant resonance dips, thus ensuring strong refractive-index discrimination. The results indicate that incorporating SiO 2 and FASnI 3 into the SPR stack is an effective approach for enhancing the performance of perovskite-based biosensors in practical cervical cancer screening and broader biochemical sensing applications.