Analytical Potential of Surface-Enhanced Fourier Transform Raman Spectroscopy on Silver Colloids

Although FT-Raman is becoming an increasingly popular analytical tool, it has proved to be relatively insensitive for the analysis of solutions. This is a serious problem, particularly for studies in the biochemical area. Because resonance Raman is not available for near-infrared excitation, surface-enhanced Raman spectroscopy (SERS) provides an important pathway to improved sensitivity. This study is concerned with assessing the potential of SERS with FT-Raman as an analytical tool for aqueous solutions. The SERS effect was investigated for a variety of organic molecules, both nitrogen and non-nitrogen containing, with silver colloids prepared by different literature methods. Various factors were studied: the effect of colloid preparative method, age of the colloid, addition of potassium chloride, time after addition of analyte, and concentration of analyte. In some cases, an analyte gave no SERS effect with a particular colloid, but exhibited a large SERS effect with a colloid prepared by a different method.