Long-time translational self-diffusion in isotropic dispersions of colloidal rods

A dispersion of fluorescent colloidal silica coated boehmite rods with length L≈325nm and diameter D≈46nm, dispersed in dimethylformamide, is synthesized. The concentration dependence of the long-time translational self-diffusion coefficient DₛL is measured with fluorescence recovery after photobleaching up to a rod volume fraction φ=0.22. A linear dependence of DₛL on concentration is found up to (L/D)φ=1. At higher concentration DₛL levels off and decreases to 3% of its value at infinite dilution for (L/D)φ=1.5.