The goal of transforming SERS from an interesting novelty into a viable quantitative analytical technique has been pursued for many years, but it is only recently that the first indications that quantitative SERS could be generally achievable have appeared. Up to this point, the challenges of preparing sensitive and reproducible enhancing media and the need to develop a deep understanding of the fundamental mechanisms of the effect (or at least to have a working knowledge of the relationship between the microstructure of the enhancing materials, their surface chemistry and the enhancements that they provide; see also Chapter 1) have been sufficient to occupy the attention of researchers who were interested in using SERS for quantitative measurements. However, many of these issues have now either been fully resolved or at least brought to the stage where they are no longer impediments. For example, new generations of enhancing media have been developed; the links between microstructure, plasmon resonances and enhancements have been established; and the role of the media's surface chemistry is being addressed. This chapter discusses these new developments and also considers the extent to which the separate strands can be combined to create standard, generally applicable methods for quantitative SERS. In addition, it highlights the need to begin the process of judging the success of new SERS methods against competing technologies, rather than against previous SERS results.
SERS MediaThe choice of enhancing media for SERS studies has grown to an extraordinary extent, although they can still be broadly divided into solution-phase suspensions of nanoparticles and micro-textured solid substrates. This division dates back to the earliest work in the area, which used either colloidal suspensions of silver or gold nanoparticles [1] or the surfaces of roughened noble-metal electrodes [2]. Since this