Near-infrared surface plasmon resonance sensing on a Si platform with nanoparticle-based signal enhancement

A Si-based surface plasmon resonance (SPR) system is examined in conditions of the nanoparticle-enhanced sensing. The system is equipped with near IR pumping light and a silicon coupling prism, used with SPR-supporting gold film in the Kretschmann-Raether geometry. Using Maxwell-Garnett (MG) effective medium theory, we modeled the SPR-related response of the system to the absorption of colloidal nanoparticles of different materials (Au, Cu, Pt, Ag, Al, Ti, Pd) on gold. We show that this response strongly depends on the nanoparticle fill factor, associated with a relative volume of nanoparticles in the absorbed layer. For low fill factors (fm ∼ 0.1), corresponding to relatively low concentrations of small nanoparticles, the absorption of nanoparticles of different materials leads to almost identical angular shifts of the SPR dip, but to a quite different intensity damping at the dip point. In contrast, the increase of the fill factor results in quite different angular and intensity SPR characteristics for the materials used, with the most pronounced sensing responses for Pt, Pd and Ti. The proposed analysis enables to estimate the efficiency of nanoparticles of different materials as markers in nanoparticle-enhanced SPR sensing.