Surface plasmon resonance spectroscopy based on evanescent field treatment
Surface plasmon resonance spectroscopy based on evanescent field treatment
复制标题
DOI：
10.1021/ac035042v
复制
发表时间：
2004-02-01
影响因子：
7.4
通讯作者：
Knoll, W
中科院分区：
文献类型：
--
作者：
Ekgasit, S;Thammacharoen, C;Knoll, W
表面等离子体共振（SPR）曲线中的反射率可以用渐逝电场与所有吸收介质的介电常数的虚部之间的乘积的积分来表示。金属薄膜中的倏逝场由两个场组成，一个场起源于棱镜/金属界面，另一个场起源于金属/电介质界面。在谐振角附近，金属/介质界面处的倏逝场强度远大于棱镜/金属界面处的倏逝场强度。电介质中的倏逝场在金属/电介质界面处具有单一起源。由于界面处的光学增强，介质中的倏逝电场的幅度远大于金属膜中的倏逝电场的幅度。然而，该领域并没有被利用在传统的SPR中，其中非吸收性电介质的折射率的变化是感兴趣的。在具有吸收电介质的系统中，介质的吸收被强倏逝电场增强。吸收介质显著改变了金属膜和介质中的倏逝场分布，导致共振角移动，反射率增加，SPR曲线展宽。由于吸收介质的吸收贡献可以通过倏逝场分布的知识从金属膜的吸收贡献中分离出来，因此可以深入分析吸收介质的SPR曲线及其与材料特性的关系。
The reflectance in a surface plasmon resonance (SPR) curve can be expressed in terms of the integration of the product between the evanescent electric field and the imaginary part of the dielectric constant of all absorbing media. The evanescent field in the metal film consists of two fields, one originating at the prism/metal interface and the other at the metal/dielectric interface. Near the resonance angle, the evanescent field strength at the metal/dielectric interface is much greater than that at the prism/metal interface. The evanescent field in dielectric medium has a single origin at the metal/dielectric interface. Due to the optical enhancement at the interface, the amplitude of the evanescent electric field in the dielectric medium is much greater than that in the metal film. This field, however, is not being utilized in conventional SPR where changes in the refractive index of the nonabsorbing dielectric media are of interest. In a system with an absorbing dielectric medium, the absorption of the medium is enhanced by the strong evanescent electric field. The evanescent field distributions in the metal film and in the dielectric medium are significantly altered by the absorbing dielectric, which results in shifting of the resonance angle, increasing of the reflectance, and broadening of the SPR curve. Since the absorption contribution from the absorbing dielectric can be separated from that of the metal film via knowledge of evanescent field distribution, an in-depth analysis of the SPR curve of an absorbing medium and its relationship with the material characteristics are possible.