Polarized interference imaging of dense disordered plasmonic nanoparticle arrays for biosensor applications

We report on light scattering by dense short-range ordered gold and silver nanoparticle arrays with 25 nm diameter and 50 nm center separation produced by masked deposition through anodized aluminum oxide membranes. Local resonant regions are formed, which scatter light with polarization components perpendicular to the incident wave due to electromagnetic coupling between particles at random angles. The observed cross-polarized far-field images have a granular structure that morphs in response to environmental variations in the article near field. We quantify the changes in the recorded images by 2D correlation matrix calculation and demonstrate the application of this approach to biomolecular sensing by using various concentrations of cysteine solution as a model system. The presented method may potentially compete with colorimetric sensor techniques since the detection setup does not require any spectroscopic instruments.