为了提高表面增强拉曼散射技术中基底的增强效果, 采用时域有限差分算法从理论上对不同入射光偏振方向下米状银纳米颗粒的电场增强进行了模拟分析, 分别研究了单个银纳米颗粒和不同组合的二聚体以及三聚体的形状、间距对局域电场强度的影响, 并且详细讨论了导致电场增强的原因。结果表明, 当米状银纳米颗粒长度约为300 nm时, 应控制其短轴约为36 nm, 间距约为2 nm, 且入射光偏振方向平行于长轴, 此时在颗粒的尖端处均会产生最大电场增强, 其中二聚体尖端对尖端情形下增强效果尤为明显。该结论为拉曼基底实验中纳米颗粒的制备提供了一定的理论基础。

Raman scattering and surface-enhanced Raman scattering (SERS) have attracted the attention of researchers due to the great potential applications in various research fields, including biomolecular sensing, analytical chemistry, surface science and material science. In order to improve the enhancement effect of the SERS substrate, the electric field enhancement of rice-shaped silver monomer, dimer, and trimer nanoparticles was simulated by the finite difference time domain method under different polarzation directions. The influence of the shape and spacing of the nanoparticles on local elecric field intensity were also studied and analyzed. On the above basis, the causes of electirc field enhancement were discussed in detail. The result shows that the electric field distributions of rice-shaped silver nanoparticles are different by changing the shape and spacing of the nanoparticles, as well as the polarization direction. The tip of the rice-shaped silver nanoparticle with long axis 300 nm, minor axis 36 nm and spacing 2 nm can produce maximum electric field enhancement when the incident polarization direction is parallel to the long axis. Moreover, due to the strong coupling between the nanoparticles, there is an obvious enhancement effect in the case of top to top configuration, and the obtained SERS enhancement factor (EF) is up to 2.4×1011. The conclusion provides theoretical basis for the preparation of silver nanoparticles in the SERS experiments.