Analysis of Biological Liquids by Metal Enhanced Fluorescence from Gold Nanoparticles

Gold nanoparticles have high sensitivity to environmental changes. This property results from phenomena of surface plasmon resonances in gold nanoparticles. While surface plasmon resonance wavelength and resonantly enhanced scattering depend strongly on nanoparticle shape and size, they also depend on properties of external environment. Thus, slight change in dielectric permittivity of environment leads to shift of surface plasmon resonance wavelength. Since surface plasmon resonances of gold fall in visible part of electromagnetic spectrum, it is possible to notice the change of surface plasmon resonance wavelength due to the change of the color of resonantly enhanced scattered light. It is possible to analyze such a change based on calculations using Spectral Fourier-Galerkin Boundary Integral Equation method with analytical regularization based on Singularity Subtraction improved by Fast Fourier Transform, which is reliable tool to study scattering characteristics solving Electromagnetic Transmission Problem for gold nanoparticles. However, the dielectric permittivity of gold depends on excitation wavelength. Because of that, calculation of scattering characteristics over some range of wavelength must be done updating permittivity parameter at each step depending on the wavelength parameter. At the same time dielectric permittivities of biological liquids may be also wavelength dependent. In this work novel numerical simulation algorithm was developed to take into account complex valued wavelength dependent dielectric permittivities of gold and biological liquids for analysis of biological liquids by metal enhanced fluorescence from gold nanoparticles.