Binary supercrystal

An alternative route to particle arrangements beyond dense packings are binary supercrystals. Such structures contain two particle populations, each of which is monodispersed with a different mean particle size. Complex crystals can be formed from such mixtures by concurrent sedimentation [63,64], butthis process is slow and unreliable. Convective particle assembly that exploits convective forces and capillary interactions has been shown to yield large, ordered domains [65] (Figure 9.9). The small particles fill the interstices between the larger ones, with the detailed structure depending both on the particle size ratio Y = s/ t and the ratio of the particle concentrations. Local fluctuations in the concentration ratio lead to domains of different structure [66]. Mixtures with y > 0.3 do not assemble into binary crystals in... 

Figure 9.9 Binary supercrystals assembled from polystyrene and silica particles having different diameters. Panels (a-c) are micrographs obtained with different diameter ratios. (Reproduced with permission from [65]. Copyright (C) (2003) Wiley-VCH Verlag GmbH Co. KCaA.)...

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