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.

With continuous mutations of SARS-CoV-2 virus, new highly contagious and fast-spreading variants have emerged, including Delta and Omicron. The popular label-free immunosensor based on surface plasmon resonance (SPR) technique can be used for real-time monitoring of the ligand-analyte or antibody-antigen interactions occurring on the sensor surface. In this work, an SPR-based biosensor combined with a nanodisk array was presented to enhance the sensitivity toward virus detection. The nanodisk arrays were employed to enhance the adsorption of molecules for better detection by increasing the SPR field. Four optimal sensing configurations of silver or gold nanodisks on gold thin films with different aspect ratios were achieved through systematic optimization of all parameters to yield the best sensor performance. The resonance angle can be modulated simply by the aspect ratio of nanodisk array. The sensitivity of the optimized sensors has been improved, and the detection limit is smaller than that of bare gold-based sensor. The multi-jump resonance angle curves at tiny refractive index can clearly distinguish the difference of trace concentrations, which is very important for the accurate detection of trace substances. Supplementary Information The online version contains supplementary material available at 10.1007/s11468-023-01802-3.

Copper having high electrical conductivity can be a candidate for the plasmonic metal. MXene (Ti3C2Tx) is an emerging two-dimensional material can be used in the biosensing field considering its excellent metallic conductivity and hydrophilic fictionalized surface terminations. Here, we employ copper and nickel as the plasmonic metals and MXene as the sensing interface to achieve significant improvement in sensitivity through angular interrogation. We propose three structures based on bimetallic materials of copper and nickel. Through systematic optimization of all parameters, three optimum sensing configurations from these structures have been achieved, where the highest sensitivity can be obtained is 626 º/RIU with 564% increment compared with that of pure copper-based sensor, and the limit of detection of the refractive index change can be as low as 1.5 × 10− 6 RIU.