粒径分布、偏斜度和粗糙度对胶体等离子体纳米粒子光学性质的影响
Effect of size distribution, skewness and roughness on the optical properties of colloidal plasmonic nanoparticles
摘要：
普遍接受的观点是，粒径分布强烈影响胶体等离子体纳米颗粒的光谱。它经常被引用的主要原因之一，而解释的理论和实验光谱的纳米粒子之间的不匹配。在这项工作中，这些方面进行了严格的分析，通过自下而上的统计方法，认为变量，如平均值，标准偏差和偏度的纳米颗粒尺寸分布相互独立。通过假设粒径分布为正态分布和对数正态分布，研究了统计参数对胶体纳米粒子Mie分析光谱的影响。形态的影响也进行了数值研究，以了解它可以发挥作用的程度。我们发现，颗粒的多分散性、偏斜度和表面形态实际上仅微弱地影响光谱。然而，关于纳米颗粒的结晶度的合适的光学常数的选择对于在光谱的理论模拟中正确预测等离子体激元带位置和等离子体激元带宽是更有影响力的因素。结果表明，平均粒径可以正确地估计直接从等离子体激元带的位置，因为它是平均值，确定的共振波长。另一方面，标准偏差可以根据从动态光散射实验获得的强度分布数据来估计。本文报道的结果明确了胶体等离子体纳米颗粒的粒度分布和光学响应的模糊性。
英文摘要：
It is a generally accepted idea that the particle size distribution strongly affects the optical spectra of colloidal plasmonic nanoparticles. It is often quoted as one of the main reasons while explaining the mismatch between the theoretical and experimental optical spectra of such nanoparticles. In this work, these aspects are critically analyzed by means of a bottom up statistical approach that considers variables such as mean, standard deviation and skewness of the nanoparticle size distribution independently from one another. By assuming normal and log-normal distributions of the particle size, the effect of the statistical parameters on the Mie analytical optical spectra of colloidal nanoparticles was studied. The effect of morphology was also studied numerically in order to understand to what extent it can play a role. It is our finding that the particle polydispersity, skewness and surface morphology in fact only weakly impact the optical spectra. While, the selection of suitable optical constants with regard to the crystallinity of the nanoparticles is a far more influential factor for correctly predicting both the plasmon band position and the plasmon bandwidth in theoretical simulations of the optical spectra. It is shown that the mean particle size can be correctly estimated directly from the plasmon band position, as it is the mean that determines the resonance wavelength. The standard deviation can on the other hand be estimated from the intensity distribution data obtained from dynamic light scattering experiments. The results reported herein clear the ambiguity around particle size distribution and optical response of colloidal plasmonic nanoparticles.
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