(489h) Colloidal Isomerism Via Competing Interactions

Assembly of simple two-dimensional colloidal clusters of six particles in thermal equilibrium favors the least symmetric shapes which is dictated by the free energy minima and higher entropy. However, we test this observation further by examining the assembly of clusters in magnetic nanoparticle dispersions to modulate competing attractive and repulsive interactions between the colloidal particles. The long-range dipolar repulsions can be tuned by the strength of external magnetic field and gives extended control over the assembly of the clusters. In contrast, it is observed that the particles with acquired dipoles surrounding the two-dimensional clusters effect the assembly of cluster and favors the formation of highly symmetric triangle clusters instead. We further investigate the effect of the long-range repulsions induced in the system with varying magnetic nanoparticle (ferrofluid) concentration and magnitude of external magnetic field.