Laboratoire de Physique des Solides, Batiment 510, CNRS UMR 8502, Universite Paris Sud XI, F 91405 Orsay, France.
Nano Lett. 2010 Mar 10;10(3):902-7. doi: 10.1021/nl903653x.
We report on the nanometer scale spectral imaging of surface plasmons within individual silver triangular nanoprisms by electron energy loss spectroscopy and on related discrete dipole approximation simulations. A dependence of the energy and intensity of the three detected modes as function of the edge length is clearly identified both experimentally and with simulations. We show that for experimentally available prisms (edge lengths ca. 70 to 300 nm) the energies and intensities of the different modes show a monotonic dependence as function of the aspect ratio of the prisms. For shorter or longer prisms, deviations to this behavior are identified thanks to simulations. These modes have symmetric charge distribution and result from the strong coupling of the upper and lower triangular surfaces. They also form a standing wave in the in-plane direction and are identified as quasistatic short range surface plasmons of different orders as emphasized within a continuum dielectric model. This model explains in simple terms the measured and simulated energy and intensity changes as function of geometric parameters. By providing a unified vision of surface plasmons in platelets, such a model should be useful for engineering of the optical properties of metallic nanoplatelets.
我们通过电子能量损失光谱法报告了单个银三角棱柱体内部表面等离激元的纳米级光谱成像，并进行了相关的离散偶极近似模拟。实验和模拟都清楚地表明，所检测到的三种模式的能量和强度随边缘长度的变化而存在明显的依赖关系。我们表明，对于实验中可用的棱柱体（边长约为 70 至 300nm），不同模式的能量和强度随棱柱体的纵横比表现出单调的依赖关系。对于较短或较长的棱柱体，通过模拟可以识别出这种行为的偏差。这些模式具有对称的电荷分布，是由于上下三角面的强耦合产生的。它们也在面内方向形成驻波，并在连续介电模型中被确定为不同阶数的准静态短程表面等离激元。该模型以简单的术语解释了测量和模拟的能量和强度随几何参数的变化。通过为血小板中的表面等离激元提供统一的视角，这种模型应该有助于金属纳米板光学性质的工程设计。
