Classical and Quantum Surface Plasmon Resonance Biosensing

Figure 1

Exciting surface plasmons in prism configuration setups. (a) Krestchmann configuration setup and (b) Otto configuration setup. Figures (a) and (b) show how surface plasmons are generated in a prism-based SPR setup. There are two common configurations that can be used to excite surface plasmons, that is, the Krestchmann configuration shown in (a) and the Otto configuration shown in (b). Both configurations are practically useful, but the Krestchmann configuration tends to be easier to configure and is more commonly used. In these setups, light is sent at a varied angle of incidence towards a glass prism (BK7) that has a gold layer on its surface (or has a gold-coated slide sitting above it). This gold layer is only a few nanometers thick. At a certain angle, the incident light couples with oscillating electrons in the thin gold layer, resulting in an evanescent wave propagating on the gold surface, which is called the surface plasmon wave. When this surface plasmon wave forms, we observe a dip in the intensity of the reflected wave, which is collected by the detector. The surface plasmon wave is sensitive to changes in the dielectric properties of the analyte (with a refractive index ) on the surface of the gold. This sensitivity changing dielectric conditions on the surface of the gold is used for biosensing applications.

(a)

(b)