基于Kretschmann结构的金银合金薄膜的SERS效应

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

利用Kretschmann棱镜耦合结构和532 nm激光光源,测试了金银合金薄膜的表面增强拉曼散射(SERS)效应,并与纯金薄膜的测试结果进行了比较.结果显示,在激发光为p偏振态且入射角近似等于表面等离子体共振(SPR)角时,附着于金银合金薄膜表面的Nile Blue分子的SERS信号达到最强,比利用纯金薄膜测得的SERS信号高约2倍.实验结果还表明,在金银合金薄膜表面自组装金纳米粒子后,Nile Blue吸附层的SERS信号比自组装纳米金之前测得的信号增强了至少3倍,比利用纳米金修饰的纯金薄膜测得的信号高出2倍多.在棱镜底面沿薄膜法线收集的SERS信号是完全非偏振光,而从棱镜侧面收集的SERS信号是p偏振光,是拉曼光借助SPR效应产生的定向发射.

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 2 times 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.