Efficient Simulation for Light Scattering from Plasmonic Core-Shell Nanospheres on a Substrate for Biosensing

Abstract

We have developed an efficient numerical method to investigate light scattering from plasmonic nanospheres on a substrate covered by a shell, based on the half-space Green's function approach. We use this method to study optical scattering from DNA molecules attached to metallic nanoparticles on a substrate and compare with experiment. We obtain fairly good agreement between theoretical predictions and the measured ellipsometric spectra. The metallic nanoparticles were used to detect the binding with DNA molecules in a microfluidic setup via spectroscopic ellipsometry (SE), and a detectable change in ellipsometric spectra was found when DNA molecules are captured on Au nanoparticles surface. Our theoretical simulation indicates that the coverage of Au nanosphere by a submonolayer of DNA molecules, which is modeled by a thin layer of dielectric material, can indeed lead to a small but detectable change in ellipsometric spectra. Our studies demonstrated the ultrasensitive capability of SE for sensing submonolayer coverage of DNA molecules on Au nanospheres.

Generalized Mie Theory for Full‐Wave Numerical Calculations of Scattering Near‐Field Optical Microscopy with Arbitrary Geometries

“…In contrast, if the resonance frequency of the Lorentzian of the inner sphere is shifted to 1358 cm −1 (see Figure 4b) which approximately coincides with a (C 60 ) 3 trimer vibration mode [ 31 ] and is outside of the Reststrahlen band, this effect disappears (the TO phonon mode does not mask this small peak, since it comes from a separate calculation of an hBN layer). The results show that the field enhancement in the inner sphere predicted by Mie's theory of a core–shell spherical system [ 32 ] is enough for a significant enhancement of the near‐field signal. In a more realistic configuration, the additional field confinement due to the hyperbolic nature of the nanotube can result in even higher electric field amplitude which can explain the amplitude of the detected peaks in ref.…”

Adapting Bobbert-Vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells

“…Different models have been proposed to describe this scattering, including the quasistatic approximation, small particle broadening, effective medium theories, anisotropic particle resonance effect, and Green's functions [14][15][16]. An exact solution of Maxwell's equations for the scattering problem of a core-shell particle placed on a substrate was studied by Bobbert and Vlieger [17,18].…”