Superdiffusive-like motion of colloidal nanorods.

In recent experiments, the temporal average C(t) of the mean square displacement for nanorods moving through a chemical monolayer was explored. The results showed a scaling C(t) approximately t(1.6), which suggest the existence of superdiffusive motion for these particles. In this paper, we interpret these results by means of a continuous-time random walk (CTRW) model from which we can reproduce the exponent 1.6 and the curve C(t) versus time found in the experiments. We show that the behavior observed arises as a consequence of the superposition of different transport mechanisms: directional propulsion plus translational and rotational diffusion. Our model reveals that this superdiffusive-like scaling may also be found in other systems as in chemotactic biological motion, provided that the characteristic times for translational and rotational diffusions are very different.