Preparation of SERS-active substrates with large surface area for Raman spectral mapping and testing of their surface nanostructure

Abstract

Surface-enhanced Raman scattering (SERS) is a powerful technique of Raman signal detection of substances at a low concentration level. It allows observation of structural details of films with very small thicknesses. It is possible to achieve the enhancement of Raman signal of species located on the surface of properly prepared SERS-active substrates of up to ca 106. One of the main requirements for the substrate to be SERS-active is the proper roughness of the surface. In this work different SERS-active Au and Ag substrates suitable for spectral mapping were prepared using procedures which consisted of electrochemical deposition of metal layer and further roughening with oxidation-reduction cycles (ORC) treatment. The nanostructures of the metal surfaces were tested using atomic force microscopy (AFM). Monolayers formed both by covalent and noncovalent linkages to the metal surface were detected and Raman spectral maps were then measured. Roughening procedure of the substrates was optimized and its effect on the SERS enhancement was discussed. The relations among the surface nanostructure, optimal roughening, type of linkage of the analyte to the surface of the substrate and the Raman signal enhancement for the experimental conditions were studied. Copyright © 2008 John Wiley & Sons, Ltd.