Surface Enhanced Raman Scattering Effect of Au-Ag Alloy Films Based on Kretschmann Configuration†

Abstract

The surface enhanced Raman scattering(SERS) effect of Au-Ag alloy films was investigated,using a 532 nm laser source and the Kretschmann configuration. The experimental results indicate that when the incidence angle of the p-polarized beam meets the surface plasmon resonance(SPR) condition,the intensities of Raman peaks for Nile Blue molecules immobilized on the Au-Ag alloy film reaches maxima,being almost 2times as high as those achieved with the pure gold layer. Gold nanoparticles(GNP) modification of the Au-Ag alloy films resulted in more than 3 times increase in Raman peak intensity. With the GNP-modified Au-Ag alloy film the Raman peaks are 2 times higher than those with the GNP-modified pure gold layer. The Raman signals detected with the probe placed below the prism substrate are completely non-polarized,but those detected along the reflected light beam on the side of the prism are p-polarized due to the SPR-coupled directional emission of Raman light excited in the evanescent-field region. The work demonstrated that the Au-Ag alloy films are advantageous over the conventional gold films for surface plasmon enhanced Raman spectroscopy.