Optical Anisotropy and Excitons in MoS2 Interfaces for Sensitive Surface Plasmon Resonance Biosensors

Abstract

The use of ultra-thin spacer layers above metal has become a popular approach to the enhancement of optical sensitivity and immobilization efficiency of label-free SPR sensors. At the same time, the giant optical anisotropy inherent to transition metal dichalcogenides may significantly affect characteristics of the studied sensors. Here, we present a systematic study of the optical sensitivity of an SPR biosensor platform with auxiliary layers of MoS2. By performing the analysis in a broad spectral range, we reveal the effect of exciton-driven dielectric response of MoS2 and its anisotropy on the sensitivity characteristics. The excitons are responsible for the decrease in the optimal thickness of MoS2. Furthermore, despite the anisotropy being at record height, it affects the sensitivity only slightly, although the effect becomes stronger in the near-infrared spectral range, where it may lead to considerable change in the optimal design of the biosensor.

Performance Comparison of Lossy Mode Resonance Refractive Index Sensors on Structures Based on Graphene and MoS2

“…The extinction coefficient (κ) is directly related to the absorbance of light in the material. 30,32 This was confirmed from the results of absorbance calculations on GM chips where the higher the value of the extinction coefficient (κ), the higher the resulting absorption (Fig. 4c).…”

“…MoS 2 is characterized by the presence of excitons A, B, C 1 and C 2 which are responsible for the strong absorption and high refractive index in the visible and near infrared ranges. 30 The refractive index of the BK7 prism at various wavelengths is obtained from the following equation: 28 μ − For MoS 2 , the monolayer thickness is 0.65 nm, and the refractive index is 5.445 + 0.5751 i. This value was obtained from research conducted by Hsu et al in 2019.…”