A dynamic light scattering study on aggregation of rodlike colloidal particles

The kinetics of aggregation of rodlike iron(III)hydroxide colloids in aqueous solution have been investigated by dynamic light scattering. KNO3 and K2SO4 electrolytes were used in different concentrations as controllers for the aggregation kinetics. The experimental results of the cluster growth were fitted in the fast regime to the diffusion limited aggregation (DLA) and are characterized by a power law with a fractal dimension d(f) = 1.71. Clearly, the slow aggregation shows the exponential kinetics of the reaction limited aggregation (RLA). In the growing curves of the colloid clusters, a transition to a very fast aggregation kinetic was observed. The transition occured at a typical aggregate size which was crucially dependent on the colloid concentration. This was taken as an evidence for a percolation process.