Shegai Timur, Li Zhipeng, Dadosh Tali, Zhang Zhenyu, Xu Hongxing, Haran Gilad
Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
Proc Natl Acad Sci U S A. 2008 Oct 28;105(43):16448-53. doi: 10.1073/pnas.0808365105. Epub 2008 Oct 16.
The interaction of light with metal nanoparticles leads to novel phenomena mediated by surface plasmon excitations. In this article we use single molecules to characterize the interaction of surface plasmons with light, and show that such interaction can strongly modulate the polarization of the emitted light. The simplest nanostructures that enable such polarization modulation are asymmetric silver nanocrystal trimers, where individual Raman scattering molecules are located in the gap between two of the nanoparticles. The third particle breaks the dipolar symmetry of the two-particle junction, generating a wavelength-dependent polarization pattern. Indeed, the scattered light becomes elliptically polarized and its intensity pattern is rotated in the presence of the third particle. We use a combination of spectroscopic observations on single molecules, scanning electron microscope imaging, and generalized Mie theory calculations to provide a full picture of the effect of particles on the polarization of the emitted light. Furthermore, our theoretical analysis allows us to show that the observed phenomenon is very sensitive to the size of the trimer particles and their relative position, suggesting future means for precise control of light polarization on the nanoscale.
光与金属纳米颗粒的相互作用会引发由表面等离子体激元激发介导的新现象。在本文中，我们使用单分子来表征表面等离子体激元与光的相互作用，并表明这种相互作用能够强烈调制发射光的偏振。能够实现这种偏振调制的最简单纳米结构是不对称银纳米晶体三聚体，其中单个拉曼散射分子位于两个纳米颗粒之间的间隙中。第三个颗粒打破了双粒子结的偶极对称性，产生了与波长相关的偏振图案。实际上，散射光变成椭圆偏振光，并且在第三个颗粒存在的情况下其强度图案会发生旋转。我们结合对单分子的光谱观测、扫描电子显微镜成像和广义米氏理论计算，以全面了解颗粒对发射光偏振的影响。此外，我们的理论分析使我们能够表明，观察到的现象对三聚体颗粒的大小及其相对位置非常敏感，这为未来在纳米尺度上精确控制光偏振提供了方法。
