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.