Optimization of copper and tin disulfide based surface plasmon resonance for the detection of brain tumor tissues

In this study, a surface plasmon resonance (SPR) sensor, including SF5 prism, copper (Cu), Tin Disulfide (SnS₂), Molybdenum Ditelluride (MoTe₂), and sensing medium (SM) layers, was designed for the detection of brain lesions. With the remarkable sensitivity of 142.15°/RIU found at 33 nm of Cu, 8 nm of SnS₂, a monolayer of MoTe_2, and refractive index (RI) of SM 1.33-1.50. To obtain the sensitivity of the proposed sensor, different brain lesions, including cerebrospinal fluid (CSF), gray matter, oligodendroglioma, low-grade glioma, lymphoma, and metastasis, were used as SM, while the thickness of the Cu layer was varied from 25 to 60 nm. A sharp SPR dip with a minimum reflectance (R_min) of 3.9 × 10⁻⁷ a.u. was obtained at a thickness of 33 nm, which also yielded the highest sensitivity (S = 136.47°/RIU) and figure of merit (FoM = 15.01/RIU). The low full width at half maximum (FWHM) at this thickness and the SPR angle shift (Δθ_res) further confirmed the improved detection capability of the sensor. According to these results, the proposed SPR sensor is very useful for detecting brain abnormalities in real time and without labels.