Effect of MoS₂ and (phosphorene, germanene, borophene) hybrid structure on the performance of an SPR biosensor for detection of bacteria

In this paper, the effect of different structures and flakes of phosphorene (Ph), germanene (Ge), and borophene (B) sandwiched between MoS₂ layers on the surface plasmon resonance (SPR) biosensor structure is simulated and investigated in the Lumerical software environment. The main structure is based on the Kretschmann structure, utilizing the BK₇ prism, a 30 nm gold (Au) layer, and an MoS₂ and (Ph, Ge, B) hybrid structure as the top layer. The reflectance curves of the proposed SPR biosensors were obtained, analyzed, and compared for different refractive index modes, specifically n = 1.33 for a neutral aqueous medium and n = 1.339 for a bacterial medium. The results demonstrate that the minimum reflectance occurs for a 30 nm Au layer at an SPR resonance angle of θ = 71.95°. However, when different configurations of (Ph, Ge, B) with varying thicknesses are sandwiched between MoS₂ layers on the Au layer, the resonance angle increases. The minimum reflectance values for a monolayer of phosphorene, a triple layer of germanene, and a triple layer of borophene sandwiched between MoS₂ double layers on the Au layer are 0.027, 0.002, and 0.004, respectively. The triple layer of germanene exhibits the highest sensitivity of 152°/RIU for Δn = 0.009 with a detection accuracy of 0.090. The simulation results of the proposed structures present new opportunities for enhancing the sensitivity and performance of SPR biosensors.