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

Abstract

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