Surface plasmon resonance (SPR) is the phenomenon of resonantly excited collective electron oscillations at a metal surface. This can be achieved by using the evanescent field of light reflecting in a prism to excite SPR in a thin metal layer on top of that prism. If resonance conditions are fulfilled a minimum of light is reflected. The conditions for the reflecting light for which resonance occurs depend very much on the presence of optical structures in the evanescent field. Therefore, SPR can be used to image lateral heterogeneities in those structures and monitor changes in time.
A general introduction into reflectometric methods for the study of surfaces and thin layers is given in the first chapter. Fresnel’s theory can be used to describe these methods. In the second chapter SPR is used to detect immune reactions at surfaces. In this case the optical structure within the evanescent field changes in time through the formation of immune complexes. Two types of SPR sensors are described. The first one uses a differential detection technique, and is demonstrated with single and multi-channel measurements. The second one operating with a fixed angle of incidence, is used to monitor a two-dimensional array of sensor surfaces. A model describing the propagation of surface plasmons near an indexstep is described in the third chapter. Using this model one can estimate the lateral resolution obtainable with surface plasmon microscopy (SPM), where the reflecting light is imaged with a microscope objective. The fourth chapter describes an SPM setup and a number of methods used to enhance the lateral resolution. An introduction into the Langmuir-Blodgett (LB) method for the preparation of monolayers is given in the fifth chapter. The SPM is used to image domains in phase-separated lipid monolayers. In the sixth chapter a different method is used for the imaging of phase-separated monolayers. Adhesion atomic force microscopy (adhesion AFM) is used to measure the adhesive interaction between the layer and the very sharp AFM tip for every point in the resulting image. This image shows the lateral distribution within the layer of chemical groups that are exposed to the tip.