NNL, Istituto Nanoscienze, CNR, Via Arnesano, Lecce, Italy.
ACS Nano. 2010 Jul 27;4(7):4117-25. doi: 10.1021/nn1007918.
In this paper a theoretical study of polarization properties of a silver nanosphere touching a homogeneous silver substrate and covered by oxide layers of increasing thickness, is reported. Oxide layers are often deposited on metallic nanostructures in metal-enhanced fluorescence (MEF) or surface-enhanced raman scattering experiments to avoid nonradiative energy transfer from emitters to the metal, and to increase the nanoparticles stability against thermal processes and laser exposure. Not much has been said on the effect of the oxide on the field enhancement of such kind of plasmonic systems. This work aims at filling this gap by shedding light on the effects of the oxide coverage on the near and far field behavior: numerical simulations performed in the framework of the discrete dipole approximation show the presence of new resonances in the absorption spectra and, of major importance for MEF applications, a strong enhancement of the near field around the nanosphere.
本文报道了对一个接触均匀银衬底且被氧化层覆盖的银纳米球的偏振特性的理论研究。在金属增强荧光（MEF）或表面增强拉曼散射实验中，通常会在金属纳米结构上沉积氧化层，以避免发射器的非辐射能量转移到金属上，并提高纳米颗粒对热过程和激光照射的稳定性。然而，对于氧化层对这种等离子体系统的场增强的影响，人们并没有太多的研究。这项工作旨在通过揭示氧化覆盖层对近场和远场行为的影响来填补这一空白：在离散偶极子近似框架内进行的数值模拟显示，在吸收光谱中出现了新的共振，并且对于 MEF 应用来说，非常重要的是，纳米球周围的近场得到了强烈增强。
