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The structure of colloidal clusters formed by long-range attractive interactions under diluted conditions is studied by means of Monte Carlo simulations. For a not-too-long attraction range, clusters show self-similar internal structure with lower density than that typical for diffusive aggregation. For long-range interactions, low kappa, nonfractal clusters are formed (dense at short scales but open at long ones). The dependence on the volume fraction shows that more-compact clusters are grown the higher the colloidal density for diffusive aggregation and attraction-driven aggregation in the fractal regime. The whole trend is explained in terms of the interpenetration among aggregates. In attraction-driven aggregations, the interpenetration of clusters competes with aggregation in the tips of the clusters, causing low-density clusters. more...

The objective of this work is to test the very recent Levin's theory for charged colloids (Levin, Y.; Barbosa, M. C.; Tamashiro, M. N. Europhys. Lett. 1998, 41 (2), 123). To accomplish this, the fraction of condensed ions has been experimentally obtained from electrophoretic mobility data and surface charge values. Latexes with different functionalities, surface charges, and sizes were selected in order to support the universality of the ion condensation effect. The good agreement between charge and fraction of condensed ions confirms Levin's theory and makes ion condensation a clear candidate for explaining the observed insensitivity of the electrophoretic mobility to surface charge variations, for sufficiently large charge. more...