制备壳厚为2~3nm，核尺寸为15、25、50nm的Au@SiO₂纳米粒子代替Au纳米粒子，用来研究电磁场耦合强度与粒子尺寸和间距之间的关系。实验结果表明处在硅衬底上核尺寸为50nm的Au@SiO₂纳米粒子增强效果更佳。为了进一步提高Au@SiO₂纳米粒子的拉曼活性，将核尺寸为50nm的Au@SiO₂纳米粒子置于光滑的金表面，结果表明罗丹明6G的信号获得了更大的增强。利用时域有限差分法分别计算了不同粒径、间距和处在不同基底材料上的Au纳米粒子二聚体的表面增强拉曼散射(SERS)活性，结果表明粒子尺寸越大，间距越小，处在金衬底上的Au纳米粒子二聚体电磁场耦合强度越高，这与实验结果完全相符。另外，粒子间的耦合方式从粒子间隙转移到粒子与衬底之间，克服了粒子间距不可控的问题。这为获得灵敏度和稳定性更高的拉曼活性基底提供了新的思路。

By synthesizing Au@SiO₂ nanoparticles with shell thickness of 2~3 nm and core size of 15, 25, 50 nm instead of Au nanoparticles, the relationship between electromagnetic coupling intensity and particle size and gap is studied. The results show that the Au@SiO₂ nanoparticles with core size 50 nm have much more enhancement. In order to further increase the surface-enhanced Raman scattering (SERS) activity, the Au@SiO₂ nanoparticles are layered on the smooth gold surface, and then stronger SERS signal is obtained than that from Au@SiO₂ nanoparticles on the silicon surface. The dimensional finite different time domain method is used to simulate the SERS activity under different size, gap and substrate conditions. The results show that the bigger of the particles are and the narrower the gaps are, the higher the electromagnetic coupling intensity of the Au nanoparticles on the smooth gold surface is. It agrees well with our experiment data. In addition, the hot spot from the gap between nanoparticles is transferred to the gap between nanoparticle and substrate. This provides a convenient way to prepare the high sensitivity and stability Raman substrate.