Dynamic light scattering of short Au rods with low aspect ratios

The translational and rotational diffusion of a series of gold nanorods with low aspect ratios was investigated by dynamic light scattering (DLS). It is shown that the translational and rotational diffusion coefficients can be determined because the particle shape causes an anisotropy of the polarizability. This gives rise to two clearly distinguishable relaxation modes in the time correlation function of the scattered light. The particle length and aspect ratio were determined independently by transmission electron microscopy (TEM). Using a hydrodynamic model, these geometrical parameters were converted to diffusion constants, which agree well with the values determined by DLS. Additionally, it is possible to obtain an estimate of the particles' aspect ratio from the amplitude ratio of the two relaxation modes.