Brief history of SPRI1:
In 1902, Wood, observing the spectrum of a continuous source of white light using a diffraction grating in reflection, noticed thin dark bands in the diffracted spectrum2.
Theoretical analysis undertaken by Fano3 in 1941 led to the conclusion that these anomalies were associated with surface waves (surface plasmon) supported by the network.
It was in 1968 that Otto4 showed that these surface waves can be excited by using attenuated total reflection. In the same year, Kretschmann and Raether5 obtained the same results from a different configuration of the attenuated total reflection method.
Following this work, the interest for surface plasmons has increased considerably, in particular for characterizing thin films and for studying processes taking place on metal interfaces. Marking a turning point in surface plasmon applications, Nylander and Liedberg, for the first time in 1983, exploited the Kretschmann configuration for gas and biomolecules6 detection. The different possible exploitations in this field, and the need for more and more robust and reliable devices allowing the understanding of biomolecular phenomena, gave birth to companies specialized in the development and the sale of SPR devices.
Between 1902 and 1912, R.M. Wood (1868-1955) at Johns Hopkins University (Baltimore, USA) noticed that when he shined polarized light onto a metal-backed diffraction grating, a pattern of unusual dark and light bands appeared in the reflected light. Although he speculated about how the light, gratings and metal interacted, a clear answer to the phenomenon was not provided.
In the 1950s more experimentation was done on electron energy losses in gasses and on thin foils. Pines and Bohm suggested that the energy losses were due to the excitation of conducting electrons creating plasma oscillations or plasmons. Further research revealed that the energy loss resulted from excitation of a surface plasma oscillation in which part of the restoring electric field extended beyond the specimen boundary. Therefore, the presence of any film or contaminant on the specimen surface affects the surface plasma oscillation. This effect was described in terms of excitation of electromagnetic ‘evanescent’ waves at the surface of the metal, and in the 1970s evanescent waves were described as a means to study ultra-thin metal films and coatings.
In the late 1960s, optical excitation of surface plasmons by means of attenuated total reflection was demonstrated by Kretschmann and Otto.
In the 1980s, surface plasmon resonance (SPR) and related techniques exploiting evanescent waves were applied to the interrogation of thin films, as well as biological and chemical interactions. These techniques allow the user to study the interaction between immobilized ligands and analytes in solution, in real time and without labelling of the analyte. By observing binding rates and binding levels, there are different ways to provide information on the specificity, kinetics and affinity of the interaction, or the concentration of the analyte.