Tunable fano resonance-enhanced surface plasmon biosensor based on MXene/MoS₂ heterostructure

Two-dimensional materials have unique physical properties such as high electrical conductivity, excellent light absorption, and hydrophilicity, thus have been widely used as responsive materials for surface plasmon effect sensors in recent years. Here, we propose a Kretschmann configuration-based MXenes/MoS₂ heterostructure film material as an improved sensing layer for surface plasmon resonance (SPR) sensors and introduce an optical waveguide layer into the nanostructure to achieve a remarkable Fano resonance (FR). By separately adjusting the thickness and refractive index of the coupling dielectric and optical waveguide layers, the effective coupling between the surface plasmon polarization and the planar optical waveguide mode is achieved, which significantly improves the sensor's response performance to biomolecules and achieves high sensitivity (S, 86.13°/RIU) and better figure of merit (FOM, 281.74 RIU⁻¹) in the visible red range (around 632.8 nm). Benefiting from the light absorption gain of the heterostructure and the FR effect, the FOM of the MXene/MoS₂ Fano resonance sensor (FRS) is improved by 7.1 times compared to the traditional SPR sensor based on noble metal Au (50 nm thickness) thin film.