Electrochemically deposited silver particles for surface enhanced Raman spectroscopy

The interest in single molecule spectroscopy by means of surface enhanced Raman scattering (SERS) has grown enormously in the last five years. Unfortunately, the basic mechanisms leading to the giant enhancement of the Raman signals are still not understood. Almost every group working in the field of single molecule SERS uses silver or gold colloids prepared by a chemical reduction method, to which a highly diluted solution of the target molecules is added. After that, the colloids, are deposited gravitationally onto a glass cover slide. This leads to clusters of several nanoparticles with a large distribution regarding size and shape as well as the Raman efficiency, and the systematic investigation of sm-SERS suffers from this. Our aim was to develop a method to deposit silver clusters showing a high enhancement factor in a controlled way. For this purpose we used an electrochemical double-pulse method, which allows to control the particle size and density by systematic variation of the pulse parameters. We also compared measurements obtained with these surfaces to measurements made with colloids at the single molecule level.