Enhancing the Spectral Sensitivity of Prism-Based SPR Sensors: The Role of Analyte RI

A theoretical approach is presented to significantly enhance the spectral sensitivity of prism-based SPR sensors. The spectral sensitivity of prism-based SPR sensors is derived based on the coupling conditions of SPR and might exceed 105 nm/RIU for analytes with large RI values when other sensor parameters are carefully considered, including the RI of the prism, the angle of incidence, and the SPR active material. The spectral sensitivity could be markedly enhanced, reaching up to 10,000 nm/RIU by fine-tuning the effective RI of the incident light to be slightly larger, specifically 0.01~0.02 RIU, than the RI of the analyte, which is attributed to the large dielectric permittivity of the SPR active material, the key factor for achieving high sensitivity. The dynamic range is 0.040 RIU in the case of high sensitivity, which is sufficient in most applications. Moreover, the spectral sensitivity could be pushed even higher, into the range of 106~108 nm/RIU, by positioning the effective RI of the incident light closer to that of the analyte. However, it requires a careful balance between optimizing the sensitivity and maintaining an acceptable dynamic range.