Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089, USA.
Nano Lett. 2010 Aug 11;10(8):2749-54. doi: 10.1021/nl904170g.
We demonstrate a method for fabricating arrays of plasmonic nanoparticles with separations on the order of 1 nm using an angle evaporation technique. Samples fabricated on thin SiN membranes are imaged with high-resolution transmission electron microscopy (HRTEM) to resolve the small separations achieved between nanoparticles. When irradiated with laser light, these nearly touching metal nanoparticles produce extremely high electric field intensities, which result in surface-enhanced Raman spectroscopy (SERS) signals. We quantify these enhancements by depositing a p-aminothiophenol dye molecule on the nanoparticle arrays and spatially mapping their Raman intensities using confocal micro-Raman spectroscopy. Our results show significant enhancement when the incident laser is polarized parallel to the axis of the nanoparticle pairs, whereas no enhancement is observed for the perpendicular polarization. These results demonstrate proof-of-principle of this fabrication technique. Finite difference time domain simulations based on HRTEM images predict an electric field intensity enhancement of 82400 at the center of the nanoparticle pair and an electromagnetic SERS enhancement factor of 10(9)-10(10).
我们展示了一种使用角蒸发技术制造等离子体纳米粒子阵列的方法，其分离距离约为 1nm。在薄 SiN 膜上制造的样品使用高分辨率透射电子显微镜（HRTEM）进行成像，以分辨纳米粒子之间实现的小分离。当用激光照射时，这些几乎接触的金属纳米粒子产生极高的电场强度，从而导致表面增强拉曼光谱（SERS）信号。我们通过在纳米粒子阵列上沉积 p-氨基苯硫酚染料分子，并使用共焦微拉曼光谱对其拉曼强度进行空间映射，从而定量这些增强。当入射激光平行于纳米粒子对的轴偏振时，我们的结果显示出显著的增强，而对于垂直偏振则观察不到增强。这些结果证明了这种制造技术的原理验证。基于 HRTEM 图像的有限差分时域模拟预测在纳米粒子对的中心处电场强度增强 82400，电磁 SERS 增强因子为 10(9)-10(10)。
