Quantification using SERS on a colloidal substrate

This thesis explores the practical usefulness of surface enhanced Raman spectroscopy on a colloidal substrate for quantification of organic analytes in a water matrix. The method evaluated is very simple and accessible as it utilizes a commercially available hand held Raman spectrometer and citrate reduced silver colloid substrate. Spectra of 4-mercaptopyridine (Mpy) and riboflavin (Rf) samples in distilled water were recorded. A Raman enhancement factor on the order of 108 was achieved for Mpy and its limit of detection was 0.1 nM. The standard deviation of Mpy intensity was <10% for 25 nM samples recorded at the same point in time, but significantly higher for samples recorded at different times. Mpy and Rf could be detected in parallel and both analytes had a close to linear Raman intensity to concentration relationship over a 100 times relative concentration change. We conclude that with improved substrate stability, a similar method should be practically applicable for quantification of suitable analytes down to the nM-range in samples of well defined composition. Considering the method's simplicity and the limited optimization efforts it has a large room for improvement