Sørensen Lasse K, Utyushev Anton D, Zakomirnyi Vadim I, Ågren Hans
Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
Phys Chem Chem Phys. 2021 Jan 6;23(1):173-185. doi: 10.1039/d0cp04854b.
Using the extended discrete interaction model we investigate the tunabilty of surface plasmon resonances in alloys and core-shell nanoparticles made from silver and gold in the small (1-15 nm) nanoscale regime where classical models based on the bulk dielectric constant may not apply. We show that the surface plasmon resonance of these alloys and core-shell particles to a large extent follow Vegard's law irrespective of the geometry of the nanoparticle. The evolution of the polarizability with size demonstrates a highly non-linear behaviour of the polarizability with the ratio of the constituents and geometry in alloys and core-shell nanoparticles, with the exception of the longitudinal surface plasmon resonance in nanorods and, partly, nanodisc alloys. We here show that the non-linear behaviour can be explained in terms of the difference in polarizability of the mixing constituents and local effects causing a quenching of the dipoles for geometries with a low aspect ratio. A thorough statistical investigation reveals that there is only a small dependence of the surface plasmon resonance on atomic arrangement and exact distribution in a nanoparticle and that the standard deviation decreases rapidly with the size of the nanoparticles. The physical ground for the random distribution algorithm for alloys in discrete interaction models is explained in detail and verified by a statistical analysis. For nanoparticles below 4 nm a sampling strategy is recommended.
利用扩展离散相互作用模型，我们研究了银和金制成的合金及核壳纳米颗粒在小尺寸（1 - 15纳米）纳米尺度范围内表面等离子体共振的可调谐性，在该尺度下基于体介电常数的经典模型可能不适用。我们表明，这些合金和核壳颗粒的表面等离子体共振在很大程度上遵循维加德定律，而与纳米颗粒的几何形状无关。极化率随尺寸的演变表明，合金和核壳纳米颗粒中极化率与成分比例和几何形状之间存在高度非线性行为，但纳米棒中的纵向表面等离子体共振以及部分纳米盘合金除外。我们在此表明，这种非线性行为可以通过混合成分极化率的差异以及局部效应来解释，这些局部效应会导致低纵横比几何形状的偶极子猝灭。全面的统计研究表明，表面等离子体共振对纳米颗粒中原子排列和精确分布的依赖性很小，并且标准偏差随着纳米颗粒尺寸的增大而迅速减小。详细解释了离散相互作用模型中合金随机分布算法的物理基础，并通过统计分析进行了验证。对于尺寸小于4纳米的纳米颗粒，建议采用抽样策略。
