金纳米环双体尺寸和耦合效应对表面等离子体共振特性的影响

采用离散偶极子近似方法系统地研究了金纳米环双体的消光光谱及其电场分布. 计算结果表明, 金纳米环双体在耦合作用下的共振消光峰对应着不同振动模式, 改变金纳米环双体的排列方式、 间距和尺寸大小, 其表面等离子体共振消光峰发生红移或蓝移. 因此可以通过对金纳米环双体结构参数和排列方式的设定, 调节其表面等离子体共振消光峰的位置. 电场分布表明, 水平排列的金纳米环双体较单个金纳米环产生更强的局部表面增强电场. 适当的小间距, 较大的内外半径的金纳米环水平阵列更适合做表面增强拉曼散射的衬底, 在生物分子检测等领域具有潜在的应用.

Effects of size and electric field coupling on the surface plasmon properties of gold nanoringdimer structures

The extinction spectra and the electric field distribution of the surface plasmon coupling of gold nanoring dimer in horizontal and vertical arrangements are calculated by the discrete dipole approximation method. It is found that the peaks of extinction spectra and electric field distribution of the surface plasmon coupling are sensitive to the size and the separation gap between gold nanorings. It is demonstrated that the peaks of extinction spectra will be red-shifted or blue-shifted due to the different structure parameters of gold nanorings. Because of the effect of the polarization charge coupling between adjacent gold nanoring, the local electric field distribution is found to be stronger for the gold nanoring dimer and trimer in horizontal arrangement than for the single gold nanoring. The horizontal gold nanoring trimer has stronger enhancement of local electric field than the dimer. It shows that the greater separation gap has the weaker local electric field distribution for the gold nanoring dimer and trimer in horizontal arrangement. Therefore the gold nanoring horizontal array is predicted to be an ideal surface enhanced Raman scattering substrate and is expected to have potential applications in biological and chemical detections.