Tuning of spectral and angular distribution of scattering from single gold nanoparticles by subwavelength interference layers.
Tuning of spectral and angular distribution of scattering from single gold nanoparticles by subwavelength interference layers.
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DOI：
10.1021/nl4037438
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发表时间：
2014-01
期刊：
影响因子：
10.8
通讯作者：
J. Wirth;F. Garwe;J. Bergmann;W. Paa;A. Csáki;O. Stranik;W. Fritzsche
中科院分区：
文献类型：
--
作者：
J. Wirth;F. Garwe;J. Bergmann;W. Paa;A. Csáki;O. Stranik;W. Fritzsche
局部表面等离子体共振（LSPR）作为金属纳米结构中传导电子在光照射下的共振振荡，广泛应用于传感和纳米级操作。光谱共振带的位置主要受纳米粒子的组成、尺寸和几何形状的控制，受近场环境局部折射率的影响较小。这里我们介绍了另一种调谐方法，基于纳米结构散射光的干涉调制。因此，通过在纳米颗粒和金膜之间的亚波长间隔层的干涉，入射电场在强度和方向上是波长相关的调制。因此，散射最大值的波长相对于原始纳米粒子的LSPR进行了调谐。散射波长可以通过距离纳米粒子100-200纳米的金属反射层来调节，而在纳米粒子环境中，近场间隙模式技术的工作距离可达50纳米。因此，我们首次在单纳米粒子水平上证明，依赖于干涉间隔层的厚度，散射信号的不同分布可以被观察到，如钟形或甜甜圈形的点扩散函数（PSF）。将干涉调谐效应进一步应用于具有多个共振峰的各向异性粒子（二聚体），以及从空气中移动到聚合物间隔层的粒子，研究与金膜距离结合周围折射率变化的影响。
Localized surface plasmon resonance (LSPR) as the resonant oscillation of conduction electrons in metal nanostructures upon light irradiation is widely used for sensing as well as nanoscale manipulation. The spectral resonance band position can be controlled mainly by nanoparticle composition, size, and geometry and is slightly influenced by the local refractive index of the near-field environment. Here we introduce another approach for tuning, based on interference modulation of the light scattered by the nanostructure. Thereby, the incoming electric field is wavelength-dependent modulated in strength and direction by interference due to a subwavelength spacer layer between nanoparticle and a gold film. Hence, the wavelength of the scattering maximum is tuned with respect to the original nanoparticle LSPR. The scattering wavelength can be adjusted by a metallic mirror layer located 100-200 nm away from the nanoparticle, in contrast to near-field gap mode techniques that work at distances up to 50 nm in the nanoparticle environment. Thereby we demonstrate, for the first time at the single nanoparticle level, that dependent on the interference spacer layer thickness, different distributions of the scattered signal can be observed, such as bell-shaped or doughnut-shaped point spread functions (PSF). The tuning effect by interference is furthermore applied to anisotropic particles (dimers), which exhibit more than one resonance peak, and to particles which are moved from air into the polymeric spacer layer to study the influence of the distance to the gold film in combination with a change of the surrounding refractive index.