Numerical Calculation of Surface-Enhanced Raman Scattering Nanostar Structures Based on FDTD

复杂形状的纳米星一直是认识等离子体现象的主要障碍。本文通过时域有限差分(FDTD)方法，对纳米星形结构进行模拟分析。我们对不同几何参数(如粒子直径、金星分支尖角的粗细和金星分支的数量)下的光谱响应进行了数值研究，以阐明纳米星的光学特性与几何结构之间的关系。另外，还在金纳米星的基础上耦合了银，发现可以通过调整银的不同含量来调谐纳米星的消光峰，而且能提升纳米粒子的电场增强。我们的结果为确定选择不同激发波长的SERS应用中纳米星的几何形状提供了理论指导。这项工作为开发具有宽吸收光谱增强电磁场的等离子金属晶体结构铺平了道路。此外，这项研究还为医学成像和农药残留检测提供了一种有效的SERS基底。The complex shape of nanostars has been a major obstacle to understanding plasma phenomena. In this paper, the finite difference Time domain (FDTD) method is used to simulate and analyze the nanostar structure. Numerical studies of spectral responses under different geometric parameters such as particle diameter, the thickness of Venusian branches, and the number of Venusian branches are carried out to clarify the relationship between the optical properties of nanostars and their geometric structure. In addition, silver is coupled to the gold nanostars, and it is found that the extinction peak of the nanostars can be tuned by adjusting the different content of silver, and the electric field enhancement of the nanoparticles can be improved. Our results provide theoretical guidance for determining the geometry of nanostars in SERS applications where different excitation wavelengths are selected. This work paves the way for the development of plasma metallic structures with a wide absorption spectrum enhanced electromagnetic field. In addition, this study provides an effective SERS substrate for medical imaging and pesticide residue detection.