Theoretical Calculations Of The Nearly Guided-wave And Nanoparticle-enhanced Surface Plasmon Resonance Spectrum

The novel detection technology, Surface Plasmon Resonance (SPR) which has received increasing widespread attention in the past few years, offers several advantages including high sensitivity, real time monitoring and label-free detection. The development of new coupling schemes for SPR focuses on improving the resonance intensity or the sensitivity of SPR spectrum, which has widely used as analytical tools in chemical, biological and food industries. However, the reasons for the influence of coupling schemes on SPR spectrum and its sensitivity are still not very clear. With multilayer model, we discussed the nearly guided-wave and nanoparticle-enhanced SPR spectrum by theoretical calculations. And the conclusions have received support by experiment results from other researchers.In the thesis, the excitation condition of SPR was analyzed firstly. Based on the Kretschmann configuration, we made a comparison between the gold and silver substrates of SPR spectrum in the three characteristics of SPR.According to Fresnel formula, transmission matrix and dispersion relation, the influences of the dielectric layer's refractive and thickness on SPR spectrum were discussed. The calculation results showed that the dielectric layer's real and imaginary parts of the refractive index have different effects on SPR spectrum, for they had different influence on surface plasmon wave. The causes of cut-off thickness by dispersion relation are also explained.In this thesis, a modified MG equation is used to calculate the effective dielectric constant of gold nanosphere composite film based on effective medium theory. The influence of the metallic substrate on the gold nanosphere's dipole moments was taken into account. The result demonstrated that the sensitivity of gold nanoshpere enhanced SPR spectrum was improved by localized electrical field enhancements of gold nanoshperes. The sensitivity also affected by the ratio between gold nanosphere"s diameter and intermediate dielectric layer's thickness, besides the gold nanoshpere's volume ratio.