Enhancement of side‐coupled surface plasmon resonance sensitivity by application of polymethylmethacrylate thin polymer films

Abstract

Here the theoretical and experimental investigation for enhancing surface plasmon resonance (SPR) sensitivity in a side-coupled excitation system by the application of polymethylmethacrylate (PMMA) polymer thin films is presented. Proper selection of film materials, gold layer thicknesses d Au and SPR incident angle (θ SPR) resulted in the increased effective refractive index of the sensing region, and hence of the device sensitivity, and the dynamic detection range. This work demonstrates, by first-order approximations, a characterisation scheme of SPR chips with unknown gold layer thickness d Au and uncertainty in SPR incident angle. The scheme utilised fitting theoretical calculations to measured SPR responses while varying d Au and θ SPR in equations. Device sensitivity nearly doubled following application of thin PMMA thin films on gold surfaces when sensing water-chloroform mixtures as opposed to untreated surfaces that lacked a PMMA layer. The proposed work demonstrates a facilitative balance between theoretical expectations and experimental data to develop sensors for future applications.