Detection of cortisol using long range surface plasmon resonance sensor with enhance figure of merit

Long-range surface plasmon resonance (LRSPR) sensors have been designed using franckeite 2D material for the detection of cortisol. There is growing interest in the complex sulfide mineral franckeite because of its possible application in raising the detection accuracy (DA) and figure of merit (FoM) of LRSPR sensors. Hence, franckeite layer is used for attaching the biomolecules of cortisol with concentration. At minimum reflectance, the maximum FoM of 4046.42/RIU and 7831.79/RIU is attained with cortisol concentrations of 0.36 ng/mL and 4.5 ng/mL, respectively. The maximum FoM of 9126/RIU and 11903/RIU is achieved at 1200 nm and 11 nm thickness of Teflon and silver (Ag) layer, respectively using franckeite layer, with cortisol concentration of 0.36 ng/ml and 4.5 ng/ml. At same thickness and cortisol concentration, the DA of 333.33/degrees and 434.78/degrees is obtained. Moreover, the penetration depth (PD) of 3095.02 nm is achieved at 0.36 ng/mL concentration of cortisol. Franckeite high refractive index (RI) enhances the plasmonic coupling, making the SPR signal more noticeable. This can improve the sensor's DA and FoM by enhancing its ability to detect minute variations in the RI.