A comparison of electrochemical and colloidal surface enhanced resonance Raman scattering (SERRS) from two analytes designed to chemisorb to silver surfaces

Abstract

Recent advances demonstrate that surface enhanced resonance Raman scattering (SERRS) obtained from suspensions of colloidal silver can be used quantitatively to detect specific substances at extremely low concentrations. The molecular specificity this confers is particularly useful for the development of new single step multiple analysis methods. These advances prompted a re-investigation of the relative merits of colloidal SERRS and electrochemical SERRS as detection techniques. Two dyes with different surface attachment chemistries were used. At the lowest concentrations (10 −6 M and below) the greater sensitivity of colloidal SERRS makes it the preferred technique. However, at intermediate concentrations between about 10 −4 and 10 −5 M, electrochemistry gave a higher precision and was simple to use. The conclusion reached is that if semi-quantitative analysis is required and the concentration is sufficiently high, then electrochemical SERRS would have advantages in terms of simple repeatable detection. It could be used in conjunction with the expanding range of SERRS derivitisation chemistries. With one dye, the electrochemical signal was time dependent. This suggests that the freshly prepared structured electrochemical surface is less stable to chemisorption than colloidal suspensions where this problem has not been encountered.