Plasmon-Enhanced Dynamic Depolarized Light Scattering

Nanomolar suspensions of Au nanorods were analyzed by photon correlation spectroscopy (PCS) complemented by optical absorption spectroscopy. We observed a wavelength-dependent enhancement of the anisotropic scattering as a consequence of the excitation of a longitudinal plasmon mode. The strong scattering intensity near the longitudinal surface plasmon resonance (LSPR) frequency for rods oriented parallel to the excitation optical field allowed the resolution of the translational anisotropy in an isotropic medium. Estimations of lengths and thicknesses of the Au nanorods from both translational and rotational diffusion coefficients were in qualitative agreement with values from transmission electron microscopy images. This wavelength-dependent anisotropic light scattering opens up new applications such as probing dynamics in complex environments at a single-particle level by depolarized PCS and sorting plasmonic nanoparticles according to their size/shape by polarized microscopy.