Angular-dependent polarization-based plasmon light scattering for bioaffinity sensing

We describe an approach to affinity biosensing based on the depolarization of plasmon scatter of biotinylated-bovine serum albumin coated 20 nm gold colloids crosslinked by streptavidin. Our model system employs nanoparticles which initially scatter incident light with P≈ 1, in a Rayleigh-like manner, However, upon aggregation, the nanoparticles show a decreased polarization and an increased forward scatter, consistent with both plasmon near-field coupling and Mie like scatter, enabling large changes in polarization detectable at angles approaching 180°.