Fractal colloidal aggregates with finite interparticle interactions: Energy dependence of the fractal dimension

We have studied the aggregation of colloidal gold particles with finite interparticle attraction energies with static light scattering and the combination of conventional transmission electron microscopy (TEM) and high-resolution TEM. The finite interparticle attraction energies are achieved by adding a surfactant in the suspension via adsorption. The interparticle interaction can be changed by changing the amount of the surfactant. Using a modified Derjaguin-Landau-Verwey-Overbeek theory to describe the interparticle interaction, we show that (i) the aggregates of colloidal particles can still be fractal objects with a finite interparticle attraction and (ii) the fractal dimension changes with the interparticle attraction energy, in agreement with the computer simulations of Shih, Aksay, and Kikuchi [Phys. Rev. A 36, 5015 (1987)].