MoS2 Nanosheets Modified Surface Plasmon Resonance Sensors for Sensitivity Enhancement

Benefiting from the unique properties of MoS2 nanosheets including high electron mobility, quantum confinement, nanoscale thickness, etc., an effective way is proposed and demonstrated to enhance the refractive index sensitivity of surface plasmon resonance (SPR) sensors, which is strongly desired all the time in the field of biochemical sensing. The SPR sensors are modified by the physical deposition of MoS2 nanosheets, and the sensitivity dependence on the number of deposition cycles is investigated experimentally. It is found that the sensitivity first increases and then declines with the increase of the number of deposition cycles, meaning an optimal thickness thus existing. By depositing MoS2 nanosheets for two cycles, the maximal sensitivity of 2793.5 nm RIU-1 (RIU: refractive index unit) can be achieved, which shows an enhancement of 30.67% compared with the case without any modification. Taking into account the evanescent field intensity and the propagation length, the experimental results can be well analyzed and explained. Simulation results show that the increase of MoS2 overlayers can enhance the intensity of electrical field penetrating into the analyte solution while reducing the propagation length, which collectively results in the nonmonotonic change of the sensitivity depending on deposition cycles.