Characterizing Gold Nanorods in Solution Using Depolarized Dynamic Light Scattering

The ability to custom-tailor surface plasmon resonances of metallic nanorods via their geometry has made nanorods a prominent platform for the design of novel nanomaterials with wide-ranging potential applications. Characterization of nanorod geometries within their native solution environments is essential for targeting nanorod properties to the specific application and for improved monitoring of nanorod synthesis. Here we use a custom-designed depolarized dynamic light scattering setup for measuring nanorod translational and rotational diffusion in situ. Using either straight cylinders or prolate ellipsoids as model geometries, we developed an approach to convert diffusion measurements directly into predictions of nanorod lengths and aspect ratios. Neither of these two geometrical models was able to properly reproduce real nanorod diffusion. Yet, these discrepancies mostly precluded reliable predictions of nanorod aspect ratios while derived nanorod lengths were within 10-20% of their values determined separately from transmission electron microscopy.