Tunable and Sensitive Detection of Cortisol using Anisotropic Phosphorene with a Surface Plasmon Resonance Technique: Numerical Investigation

Tunable and ultrasensitive surface plasmon resonance (SPR) sensors are highly desirable for monitoring stress hormones such as cortisol, a steroid hormone formed in the adrenal glands in the human body. This paper describes the detection of cortisol using a bimetallic SPR sensor based on highly anisotropic two-dimensional material, i.e., phosphorene. Thicknesses of bi-metal layers, such as copper (Cu) and nickel (Ni), is optimized to achieve strong SPR excitation. The proposed sensor is rotated in-plane with a rotation angle around the z-axis to obtain phosphorene anisotropic behavior. The performance parameters of the sensor are demonstrated in terms of higher sensitivity (347.78 degree/RIU), maximum angular figure of merit (1780.3), and finer limit of detection of 0.026 ng/ml. Furthermore, a significant penetration depth (203 nm) is achieved for the proposed sensor. The obtained results of the above parameters indicate that the proposed sensor outperforms the previously reported papers in the literature on cortisol detection using the SPR technique.