Chaffin Elise Anne, Bhana Saheel, O'Connor Ryan Timothy, Huang Xiaohua, Wang Yongmei
Department of Chemistry, The University of Memphis , Memphis, Tennessee 38152, United States.
J Phys Chem B. 2014 Dec 11;118(49):14076-84. doi: 10.1021/jp505202k. Epub 2014 Jul 18.
Gold-coated iron oxide core-shell nanoparticles (IO-Au NPs) are of interest for use in numerous biomedical applications because of their unique combined magnetic-plasmonic properties. Although the effects of the core-dielectric constant on the localized surface plasmon resonance (LSPR) peak position of Au-shell particles have been previously investigated, the impact that light-absorbing core materials with complex dielectric functions have on the LSPR peak is not well established. In this study, we use extended Mie theory for multilayer particles to examine the individual effects of the real and imaginary components of core refractive indices on Au-shell NP plasmonic peaks. We find that the imaginary component dampens the intensity of the cavity plasmon and results in a decrease of surface plasmon coupling. For core materials with large imaginary refractive indices, the coupled mode LSPR peak disappears, and only the anticoupled mode remains. Our findings show that the addition of a nonabsorbing polymer layer to the core surface decreases the dampening of the cavity plasmon and increases LSPR spectral intensity. Additionally, we address apparent discrepancies in the literature regarding the effects of Au-shell thickness on LSPR peak shifts.
金包覆的氧化铁核壳纳米粒子（IO-Au NPs）因其独特的磁等离子体组合特性而在众多生物医学应用中备受关注。尽管先前已经研究了核介电常数对金壳粒子的局域表面等离子体共振（LSPR）峰位置的影响，但具有复介电函数的吸光核材料对LSPR峰的影响尚未明确。在本研究中，我们使用多层粒子的扩展米氏理论来研究核折射率的实部和虚部对金壳NP等离子体峰的单独影响。我们发现虚部会抑制腔等离子体的强度，并导致表面等离子体耦合的降低。对于具有大虚折射率的核材料，耦合模式LSPR峰消失，仅剩下反耦合模式。我们的研究结果表明，在核表面添加非吸收性聚合物层可减少腔等离子体的衰减并增加LSPR光谱强度。此外，我们解决了文献中关于金壳厚度对LSPR峰位移影响的明显差异。
