Kretschmann

Fig. 4 The effect of proteins on cell adhesion, (a) Kretschmann configuration for SPR. (b) Reflectance (R) as a function of incident angle (9), before (black) and after (red) the adsorption of substances, (c) Left. Time course of SPR angle shift during exposure to culture medium supplemented with 2% FBS (solid line) and the fraction of adherent cells determined by TIRFM (circles) on NH2-SAM. The dashed line is a manual fit to the symbols, included simply as a guide [42]. Right The concentrations of serum proteins in FBS...

The immune biosensor analysis was carried out in the SPR-4 M device produced by the Institute of Physics of Semiconductors of the Ukrainian National Academy of Sciences. SPR spectroscopy was carried out in the Kretschmann configuration using He-Ne laser ( i=632.8 nm), goniometer (G-5 M), glass prism (the angle at the basis 68°) and photodiode (FD 263). The optical contact between the prism and the metallic layer was achieved by the application of polyphenyl ether (refractive index n= 1.62). 

It is important to realize that for the plasmon resonance to occur the condition of two matching plasmons at the opposite interfaces of the thin metal must be met. In other words there must be a dielectric/metal interface at which an evanescent field is created. In the Kretschmann geometry that interface is created by having the metal coated on the glass prism. Likewise, the SPR condition can also be realized in a fiberoptic format with a thin metal layer deposited on a flattened single-mode optical... 

Figure 9. ATR method for exciting surface electromagnetic waves by using a single prism with the metal film serving as a gap as developed by Kretschmann and Raether (12)...

Kretschmann and Raether.H In order to have the needed total internal reflection at the prism-metal interface, one is limited (approximately) to wavelengths shorter than 3 ym. With gold, silver, or copper films and a prism with large refractive index (e.g. Ge), it is possible to reach 5 or 6 ym. 

Figure 13. (a) Wavelength vs. coupling angle for S-120 dye on a Ag substrate (b) the minimum reflectivity vs. wavelength for the same system. The measured points are shown as open circles and the solid curves calculated from bulk values of the dielectric function for S-120 dye. The measurements were made using the Kretschmann—Raether arrangement (19). 

Fig. 2 Surface plasmon resonance device in the Kretschmann configuration, so is the refractive index of prism, ei is the refractive index of thin metal film (usually Au or Ag), 62 is the refractive index of air, and 0 represents the critical angle...

Combination of Surface Plasmon Resonance (SPR) and Optical Waveguide Spectroscopy (OWS) was used for the simultaneous determination of refractive index and film thickness of the hydrogel layers in the Kretschmann configuration [24], The resulting angle scans from the SPR instrument were fit to Fresnel calculations and different layers were represented using a simple box model. A detailed description of this process has been published previously [18]. 

Fig. 2. (Left) Excitation of SPR via the Kretschmann geometry. (Right) (A) Fresnel simulation of angular dependence of reflected light intensity and the corresponding relative field intensity. (B) Experimental data of an angular scan of the reflected light intensity and the corresponding fluorescence emission from surface attached Cy5-DNA molecules.

The SPR, as well as the SPFS and the SPDS set-ups are built in the Kretschmann-Raether configuration depicted in Fig. 5. A detailed description can be found in a more specific publication [25]. Briefly, the modulated and polarized beam of a laser is reflected off the base of the coupling prism and fed into a photo-diode detector. The prism/sample and the photo-detector are mounted on two co-axial goniometers, respectively, allowing for an independent tuning of the respective angular positions. 

The diffraction experiments can be performed on the same Kretschmann SPR set-up (cf. Fig. 6). To resolve the diffraction orders, the angular acceptance of the photo-diode detector is defined by a 1 mm slit to be At 0.08°. The coaxial goniometers enable an independent tuning of the incident angle of the laser and/or the detection angle. Both motors rotate in a 0/20 fashion for the usual SPR angular scans, whereas only the detector motor rotates when performing diffraction scans. 

Fig. 1 Kretschmann configuration in SPR depicting the conversion of energy from light waves to surface plasmons via a gold/dielectric interface...

---