Dual BaTiO3 layer-cavity assisted enhancement of copper-based surface plasmon resonance biosensor

Studies have shown that the two-dimensional transition metal dichalcogenides, graphene and MXene (Ti3C2Tx), and other materials not only can effectively improve the sensitivity of the surface plasmon resonance (SPR) biosensor but also reduce the detection accuracy. A SPR sensor based on dual barium titanate (BaTiO3) layers forming Fabry-Pérot (F-P) cavity was proposed to achieve this goal. Specifically, we employed a copper/nickel (Cu/Ni) bimetal as the plasmonic metal, two layers of BaTiO3 wrapped Cu/Ni bimetal to form a F-P cavity structure, and PMMA as the sensing layer. By optimizing the thickness of each film layer, the sensitivity reached 554.6 º/RIU, 6.2% higher than Cu/Ni/PMMA structure, and the corresponding full width at half maximum (FWHM) decreased by 15.4%. In addition, we used seven two-dimensional materials to replace PMMA but keeping other parameters unchanged, the obtained FWHM of the reflection spectrum was also reduced. These findings may benefit the application of the Fabry-Pérot cavity in biosensors and spectral modulation.