Surface plasmon resonance (SPR) sensors based on a silver film suffer from signal degradation due to silver oxidation in aqueous sensing environments. To overcome this limitation, we fabricated the planar plasmonic substrate employing an atomic MoS2 layer on a silver surface. Successful production of a large-area MoS2 monolayer blocks the penetration of oxygen and water molecules. In addition, we theoretically and experimentally found that MoS2 layer on the silver film can improve the SPR sensitivity and stability significantly. In this study, the proposed SPR substrate has the potential to provide highly enhanced sensor platforms for surface-limited molecular detections.

We examine the correlation between the plasmon field distribution and the sensitivity enhancement for both reflection-and transmission-type localized surface plasmon resonance (LSPR) biosensors with surface-relief gold nanogratings. In our calculation, the near-field characteristics are obtained from the finite-difference time-domain method and compared with the refractive index sensitivity as a unit target sample moves along the sensor surface. The numerical results show that the highest enhancement of sensitivity is found at the lower grating corners where an interplay between the target sample and the locally enhanced field can occur efficiently. This study suggests that, by localizing biomolecular interactions to the highly enhanced field, we can achieve a significantly improved LSPR detection with high sensitivity and a great linearity in a wide dynamic range.

Although subwavelength dielectric gratings can be employed to achieve a high sensitivity of the surface plasmon resonance (SPR) biosensor, the plasmonic interpretation verifying the resulting sensitivity improvement remains unclear. The aim of this study is to elucidate the effects of the grating's geometric parameters on the amplification of SPR responses and to understand the physical mechanisms associated with the enhancement. Our numerical results show that the proposed SPR substrate with a dielectric grating can provide a better sensitivity due to the combined effects of surface reaction area and field distribution at the binding region. An influence of adhesion layer on the sensor performance is also discussed. The obtained results will be promising in high-sensitivity plasmonic biosensing applications.

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