Leibniz-Institut für Polymerforschung Dresden e.V., Institute of Physical Chemistry and Polymer Physics, Hohe Str. 6, 01069 Dresden, Germany.
Physical Chemistry II, University of Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany.
Nanoscale. 2017 Jul 13;9(27):9376-9385. doi: 10.1039/c7nr02952g.
Nanorattles are metallic core-shell particles with core and shell separated by a dielectric spacer. These nanorattles have been identified as a promising class of nanoparticles, due to their extraordinary high electric-field enhancement inside the cavity. Limiting factors are reproducibility and loss of axial symmetry owing to the movable metal core; movement of the core results in fluctuation of the nanocavity dimensions and commensurate variations in enhancement factor. We present a novel synthetic approach for the robust fixation of the central gold rod within a well-defined box, which results in an axisymmetric nanorattle. We determine the structure of the resulting axisymmetric nanorattles by advanced transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS). Optical absorption and scattering cross-sections obtained from UV-vis-NIR spectroscopy quantitatively agree with finite-difference time-domain (FDTD) simulations based on the structural model derived from SAXS. The predictions of high and homogenous field enhancement are evidenced by scanning TEM electron energy loss spectroscopy (STEM-EELS) measurement on single-particle level. Thus, comprehensive understanding of structural and optical properties is achieved for this class of nanoparticles, paving the way for photonic applications where a defined and robust unit cell is crucial.
纳米振子是具有核壳结构的金属粒子，核和壳由介电间隔物隔开。这些纳米振子已被确定为一类很有前途的纳米粒子，因为它们在腔体内具有非凡的高电场增强能力。限制因素是由于可移动的金属核而导致的重现性和轴对称性的损失；核的运动导致纳米腔尺寸的波动和增强因子的相应变化。我们提出了一种新颖的合成方法，用于将中心金棒牢固地固定在一个明确定义的盒子内，从而得到轴对称的纳米振子。我们通过先进的透射电子显微镜（TEM）和小角 X 射线散射（SAXS）确定了所得轴对称纳米振子的结构。从紫外可见近红外光谱获得的光吸收和散射截面与基于 SAXS 得出的结构模型的有限差分时间域（FDTD）模拟定量一致。在单粒子水平上通过扫描 TEM 电子能量损失光谱（STEM-EELS）测量证明了高且均匀的场增强的预测。因此，对这类纳米粒子的结构和光学性质有了全面的了解，为光子学应用铺平了道路，在光子学应用中，定义明确且坚固的单元至关重要。
