Design and analysis of BiFeO3/WS2/TiO2 heterostructure-based surface plasmon resonance biosensor with enhanced performance

Biosensors based on surface plasmon resonance (SPR) have emerged as an important part of modern optical sensing platforms because of their high sensitivity, and ability to detect in a label-free manner. However, most reported SPR sensors solely rely on conventional plasmonic materials or integrate only a single 2D materials or dielectric over layer, which limits further improvement of sensitivity. In contrast, this work presents a novel heterostructured multilayer SPR biosensor that uniquely incorporates dual plasmonic layers of silver (Ag) and nickel (Ni), a 2D tungsten disulfide (WS₂) layer, and two dielectric layers consisting of bismuth ferrite (BiFeO₃) and titanium dioxide (TiO₂). The proposed BK7/Ag/BiFeO₃/WS₂/TiO₂/Ni heterostructure enhances sensitivity by leveraging the synergistic multiferroic properties of BiFeO₃, along with the field-enhancing effects of the WS₂ and TiO₂ layers, enabling superior plasmonic coupling compared to previously reported SPR configurations. The structure is excited with 633 nm monochromatic light, and its optoresponse is analyzed and optimized utilizing the finite-difference time-domain (FDTD) method. Numerical analysis demonstrates substantial improvement in sensing performance, exhibiting a maximum sensitivity of 443 deg/RIU, a detection accuracy (DA) of 0.45905, and a quality factor (QF) of 91.81 RIU⁻¹. The suggested sensor reveals a 3.2-fold enhancement in sensitivity relative to a typical SPR setup. The sensor has remarkable detection efficiency within the refractive index (RI) range of 1.330–1.335, pertinent to biomolecular sensing contexts. The results suggest that the proposed sensor offers high precision and ultrasensitive detection for diverse biomolecular targets, which proves its capability to be a potential candidate in biomedical diagnostics.