Light scattering from coupled plasmonic nanospheres on a stretchable substrate for application as a biosensor or mechanical sensor

摘要

The ellipsometric spectra (Ψ and Δ) of coupled metallic nanoparticles on a stretchable substrate have been studied via the spherical-harmonics based Green's function method. We use Au trimmer nanoparticles and dielectric substrate. The calculated ellipsometric spectra show a plasmonic resonance peak with asymmetric lineshape. For a trimmer of metallic nanoparticles on a stretchable substrate, the separation between nanoparticles in the trimmer can be varied by the applied mechanical stress. We find that both the plasmonic resonance peak position and the signal strength at the resonance frequency are sensitive to the gap distance in the trimmer, which can be controlled by the stretchable substrate. The simulation results indicate that the sensitivity of the plasmonic resonance lineshape to the inter-particle distance allows this coupled nanoparticle system to be used as a biosensor or mechanical sensor. The experimental ellipsometric spectra for closely-spaced metallic nanoparticles on a PDMS substrate are also reported.