Use of colloidal SERS for the trace detection of organic species: a survey based on pyridine as the probe molecule

In view of the reported extreme sensitivity of surface enhanced Raman spectroscopy, the potential of colloidal silver and gold sols for the purpose of semi‐quantitative trace analysis of organic molecules was investigated. High irreproducibility in Raman intensities is reported regarding most of the variables that come into play when preparing the sols, e.g. stirring rate, addition time of chloride ions and ageing. Experimental enhancement factors differ by orders of magnitude even for sols prepared from the same recipe. The value of colloidal SERS for analytical purposes, in particular when employing silver sols, therefore seems to be limited to qualitative analysis.