Plasmonics ( IF 3 ) Pub Date : 2021-08-18 , DOI: 10.1007/s11468-021-01525-3 Qing-Wei Sun 1 , Qi Sun 1 , Qing-Yu Zhang 1 , Nan Zhou 1 , Xi-Na Li 1
The optical properties of nanostructures are rather important for designing plasmonic devices. In this work, the plasmonic properties of Ag-coated spherical dielectric nanoparticles (NPs), namely, Ag-SiO2-NPs, Ag-ZnO-NPs, and Ag-TiO2-NPs, were studied using a method of finite-difference time-domain calculations. It was found that the Ag-coated dielectric NPs start to exhibit unique plasmonic properties different from Ag-NPs as the thickness of Ag shells is reduced to be less than a critical value, which is basically determined by the penetration depth of light in silver. On the other hand, the core–shell structures of Ag-coated dielectric NPs were found to be of benefit to the plasmonic resonance high-efficiently coupled with the incident light. In the extinction spectra of Ag-coated dielectric NPs with sufficient thin Ag shells, the dipole plasmonic resonance is predominant and exhibits a pronounced red-shift up to infrared band with increasing the NP sizes. In addition to the electromagnetic waves of emission towards the outside, the electromagnetic field in the dielectric NP inside is uniformly enhanced as well and both of dipole and quadrupole plasmonic resonances are identified. The Ag-coated dielectric NPs are suggested to have great potential in the plasmonic devices working in infrared band, such as the light emitters and SERS substrates for biosensing.
Graphical abstract
中文翻译:
用有限差分时域计算研究银包覆球形介电纳米粒子的等离子体性质
纳米结构的光学特性对于设计等离子体装置相当重要。在这项工作中,Ag 包覆的球形介电纳米粒子 (NPs),即 Ag-SiO 2 -NPs、Ag-ZnO-NPs 和 Ag-TiO 2的等离子体特性-NPs,使用有限差分时域计算方法进行研究。结果发现,随着银壳的厚度减小到小于临界值,镀银的介电纳米颗粒开始表现出不同于银纳米颗粒的独特等离子体特性,该临界值基本上由光在银中的穿透深度决定。另一方面,发现Ag包覆电介质NPs的核壳结构有利于与入射光高效耦合的等离子体共振。在具有足够薄 Ag 壳的 Ag 涂层电介质 NP 的消光光谱中,偶极等离子体共振占主导地位,并且随着 NP 尺寸的增加,显示出明显的红移至红外波段。除了向外发射的电磁波,电介质 NP 内部的电磁场也均匀增强,偶极子和四极子等离子体共振都被识别。银涂层电介质纳米粒子被认为在红外波段的等离子体器件中具有巨大的潜力,例如用于生物传感的光发射器和 SERS 基板。