Differential dynamic microscopy to measure the translational diffusion coefficient of nanorods.

We explore differential dynamic microscopy (DDM) as a low angle scattering technique to determine the translational diffusion coefficients of gold rod shaped nanoparticles. The method is tested using five differently sized nanorods, and compared with results obtained from polarized dynamic light scattering. For the rods studied here, the method of DDM may be a more robust technique as obtaining the translational diffusion coefficient is more straightforward. Results obtained from DDM are then used as an input to fitting depolarized dynamic light scattering data for the determination of the rotational diffusion coefficient. The measured diffusion coefficients are compared with theoretical predictions based on rod sizes.