U-shaped optical fiber SPR sensor based on GeS sensitizing film layer

With the urgent demand of low concentration molecular detection, an innovative solution is presented to improve the sensitivity of surface plasmon resonance (SPR) sensors through germanium sulfide (GeS) nanosheets on a U-shaped optical fiber structure, and successfully applied to the detection of environmental refractive index (RI). GeS, as a novel sensitizing film layer, has higher electron mobility and a high absorption coefficient compared with previous 2D materials, which can enhance the coupling strength of the surface electric field and thus effectively improve the sensitivity. Finite element simulations and refractive index experiments are performed to test the sensing characteristics of Au film-GeS sensors with different thicknesses. The test results show that the sensitivity of the proposed Au film-GeS sensor (optimal parameters: Au film 50 nm and GeS film 30 nm) is 7410.15 nm/RIU, which is about 2.14 times greater than that of a pure gold film sensor in the same structure. The sensor has advantages of high stability and good reproducibility in practical applications, exhibiting a relative standard deviation (RSD) of 0.0062% and 2.3445% respectively in stability and reproducibility experiments. In addition, the sensor boasts high economic efficiency, straightforward fabrication, and real-time monitoring capabilities, thus presenting significant potential for development in biochemical, environmental sustainability monitoring, and food quality detection.