Manipulated localized surface plasmon resonances in silver nanoshells coated with a spherical anisotropic layer

The influences of the anisotropy of the outer spherically anisotropic （SA） layer on the far-field spectra and near- field enhancements of the silver nanoshells are investigated by using a modified Mie scattering theory. It is found that with the increase of the anisotropic value of the SA layer, the dipole resonance wavelength of the silver nanoshell first increases and then decreases, while the local field factor （LFF） reduces. With the decrease of SA layer thickness, the dipole wavelength of the silver nanoshell shows a distinct blue-shift. When the SA layer becomes very thin, the modulations of the anisotropy of the SA layer on the plasmon resonance energy and the near-field enhancement are weakened. We further find that the smaller anisotropic value of the SA layer is helpful for obtaining the larger near-field enhancement in the Ag nanoshell. The geometric average of the dielectric components of the SA layer has a stronger effect on the plasmon resonance energy of the silver nanoshell than on the near-field enhancement.

Au-Ag合金纳米球壳的折射率传感特性分析与优化

基于Au纳米颗粒的稳定性、无毒性、生物相容性和Ag纳米颗粒优异的消光特性,Au-Ag合金纳米颗粒在生物传感中存在着潜在的应用价值。为了能找到传感性能更好的合金纳米颗粒,本文利用双层球Mie散射理论和介电函数尺寸修正模型定量研究了Au-Ag合金纳米球壳的尺寸参数对折射率灵敏度、半峰宽和品质因子的影响,获得了最佳品质因子和对应的优化尺寸。同时,本文研究了Au摩尔分数对最佳品质因子和优化尺寸的影响。结果发现,当Au摩尔分数x为0.5时,Au-Ag@SiO_(2)(Au-Ag@Vacuum)合金纳米球壳的最大品质因子为2.09(2.20),对应的内核半径和外壳厚度分别为22.3 nm(23.6 nm)和8.7 nm(6.9 nm)。当Au摩尔分数小于0.25时,Au-Ag合金纳米球壳的品质因子优于Au纳米球壳。随着Au摩尔分数的减小,品质因子增大,甚至是Au纳米球壳的2~3倍。此研究为Au-Ag合金纳米球壳在生物传感领域中的有效应用提供了理论指导。

Au-Ag合金纳米球壳光吸收和后向散射特性的优化

为了找到光吸收和后向散射特性更好的纳米球壳,利用双层同心球的Mie散射理论和介电函数的尺寸修正模型定量分析了Au-Ag合金纳米球壳的内核半径、外壳厚度、合金成分和周围介质对光吸收和后向散射特性的影响。结果表明,当Au的摩尔分数为50%,步距为0.01 nm,内核分别为SiO_(2)和真空情况时,Au-Ag合金纳米球壳的体积吸收系数最大值分别为93.660μm^(-1)和99.316μm^(-1)时,内核半径分别为27.89 nm和28.02 nm,外壳厚度分别为3.95 nm和3.35 nm;后向散射系数的最大值分别为5.280μm^(-1)和5.550μm^(-1)时,内核半径分别为56.08 nm和56.37 nm,外壳厚度分别为10.47 nm和8.89 nm。此外,当Au的摩尔分数小于9%时,Au-Ag合金纳米球壳的光吸收特性优于Au纳米球壳;当Au的摩尔分数小于11%时,Au-Ag合金纳米球壳的后向散射特性优于Au纳米球壳。