Optical Fiber Sensor with Enhanced Surface Plasmon Resonance via Au Nanoparticles-Modified PbI2

This work proposes a U-shaped fiber-optic sensor with a structure of an Au film / PbI₂ & Au nanoparticles (AuNPs). This is an applicable example of using AuNPs-modified PbI₂ in surface plasmon resonance (SPR) sensors, as studies have shown that this nanohybrid material has excellent optical properties. Finite element method (FEM) simulations verify that the presence of PbI₂ could potentially enhance the evanescent wave electric field, leading to amplified resonance signals and improved sensitivity. Results show that Au/PbI₂ structure brings about a sensitivity increase of 2.39 times compared to pure Au film structure. Subsequent experimental studies introduced AuNPs-modified PbI₂ to induce SPR & local surface plasmon resonance (LSPR) coupling mechanisms. The sensor exhibits an exceptionally high sensitivity of 22666.39 nm/RIU within the narrow refractive index (RI) range of 1.36772–1.37673, while maintaining a sensitivity of 4835.61 nm/RIU in the wider range of 1.33139–1.35775. The sensor possesses good temperature stability. The relative standard deviation (RSD) of resonance wavelength under identical RI condition is 1.048% and the temperature response is about 0.661 nm/°C within 23-51°C. Repeatability test results indicate that the sensor exhibits good repeatability. RSDs of resonance wavelengths are 0.997%, 0.686%, 0.942%, 0.587%, 0.521%, and 0.949% within the RI range of 1.33139–1.37673. It is evident that the proposed sensor holds promise in the field of biomass measurement, thereby signifying that AuNPs-modified PbI2 possesses considerable application prospects in future optoelectronic devices.