Clustering of asymmetric dumbbell-shaped silica/polystyrene nanoparticles by solvent-induced self-assembly

We report a quite simple strategy to assemble silica/polystyrene dumbbell-shaped nanoparticles into clusters with an aggregation number from two to more than 30. The polystyrene lobe serves as a patch that is made sticky and ready to merge with similar ones when the dumbbells are dispersed in an ethanol/DMF mixture. Thanks to transmission electron microscopy experiments, we describe qualitatively and quantitatively the influence of several experimental parameters such as the solvent quality, i.e. DMF fraction, and the patch-to-particle size ratio. We show that the DMF fraction range (30-50 vol%) for the sticky regime can be extended if the incubation process is completed by a centrifugation step. We also demonstrate an unexpected evolution in the average aggregation number with the patch-to-particle size ratio that may be explained by the molar mass distribution within the polystyrene core of the clusters. Lastly, we show that this assembly route may be extended to gold-coated clusters.