A novel SPR sensor sensitivity-enhancing method for immunoassay by inserting MoS2 nanosheets between metal film and fiber

In this work, we proposed a novel surface plasmon resonance (SPR) sensitivity-enhancing method by adding MoS2 nanosheets between gold film and fiber (fiber-MoS2-gold film). And we apply it to the detection of human IgG protein. The sensor was fabricated by attaching MoS2 nanosheets to the U-shaped fiber surface and then covering a layer of gold film. The refractive index sensitivity of 6184.4 nm/RIU was achieved by the fiber-MoS2-gold film sensor which is 59 percent higher than the gold film SPR sensor and 25 percent than the fiber-gold film-MoS2 SPR sensor.The presence of MoS2 increases the absorption of light energy and excites a stronger SPR phenomenon. M the same time, since the monolayer MoS2 is a direct bandgap semiconductor, the absorbed light energy promotes the transfer of electrons, generates strong coupling on the gold film surface, enhances the surface electric field, and improves the sensitivity of the sensor. Biofunctionalized sensor detect human IgG with the limit of detection as low as 19.7 ng/mL. This work proposed a novel method for enhancing the sensitivity of SPR sensor, it owns a higher sensitivity and a lower LOD which has broad application prospects in measuring low concentration biological analytes.