Plasmonic biosensor based on an effective medium theory as a simple tool to predict and analyze refractive index changes

Abstract Surface plasmon resonance was used for the detection of different kinds of organic molecules, which was achieved employing a Kretschmann configuration. A simple theoretical model based on effective medium theory was used for estimation of the SPR angle. The employed model considers an effective refractive index, which has some advantages in comparison to other effective medium theories. This model depends on the surface coverage, size of the sample and also considers the scattering by molecules deposited on the surface of the thin film. Using an effective refractive index as a tool to predict the behavior of the SPR signal offers a significant advantage for the development of new biosensors, providing a deeper physical insight on the behavior of such phenomena, since inferring the behavior of SPR signals is of great importance for chemical analysis and bio-sensing. Therefore, in this work, an effective medium model was compared with experimental SPR measurements as a function of angle incidence of different molecules deposited onto thin films, specifically Bovine Serum Albumin (BSA) and carbamazepine attached to BSA, in order to validate the theoretical model. Evaluation of the proposed model for SPR signal was in good agreement with the experimental results. Statistical tests were obtained, with a 99% of correlation between the experimental data and the theoretical predictions around the resonance.