Numerical Analysis of Black Phosphorus‐Assisted Copper‐Based Bimetallic‐Enhanced Surface Plasmon Resonance Biosensor

Abstract

Atomically thin black phosphorus (BP) is an emerging 2D material with excellent optical and electrical properties. Copper (Cu) and platinum (Pt) are plasmonic metals due to their outstanding electrical properties. Here, Cu–Pt as the plasmonic bimetal is used, BP as the sensing substrate combined with a composite layer of titanium dioxide–silicon dioxide (TiO2–SiO2) to achieve significant enhancement in sensitivity. All of the calculations are based on the transfer matrix method and Fresnel equations. Through systematic optimization of all parameters, the configuration of TiO2(15 nm)/SiO2 (5 nm)/Cu (26 nm)/Pt (9 nm)/BP (4 layers) is achieved, where the sensitivity of 533° RIU−1 reaches 390% of pure copper-based biosensor. There is a linear range of sensitivity with the change of refractive index for this optimal configuration. The detection limit of the refractive index change can be as low as 2 × 10−7 RIU, two orders of magnitude lower compared with that of pure copper-based sensors, indicating great potential to detect trace biomolecules.