Abstract
Diamond-structured crystals, particularly those with cubic symmetry, have long been attractive targets for the programmed self-assembly of colloidal particles, due to their applications as photonic crystals that can control the flow of visible light. While spherical particles decorated with four patches in a tetrahedral arrangement-tetrahedral patchy particles-should be an ideal building block for this endeavor, their self-assembly into colloidal diamond has proved elusive. The kinetics of self-assembly pose a major challenge, with competition from an amorphous glassy phase, as well as clathrate crystals, leaving a narrow widow of patch widths where tetrahedral patchy particles can self-assemble into diamond crystals. Here we demonstrate that a two-component system of tetrahedral patchy particles, where bonding is allowed only between particles of different types to select even-member rings, undergoes crystallization into diamond crystals over a significantly wider range of patch widths conducive for experimental fabrication. We show that the crystallization in the two-component system is both thermodynamically and kinetically enhanced, as compared to the one-component system. Although our bottom-up route does not lead to the selection of the cubic polytype exclusively, we find that the cubicity of the self-assembled crystals increases with increasing patch width. Our designer system not only promises a scalable bottom-up route for colloidal diamond but also offers fundamental insight into crystallization into open lattices.
Highlights
Including even- and odd-member rings [15]
A two-component system of tetrahedral patchy particles with specificity of interactions to allow for only interspecies binding appears as a propitious route to a diamond crystal
To explore whether this is the case, we carried out Monte Carlo simulations of one-component and two-component systems of N = 1000 tetrahedral patchy particles in the canonical (NVT) ensemble
Summary
Including even- and odd-member rings [15]. As diamond crystals comprise exclusively even-member rings, the tetrahedral patchy particles become dynamically arrested due to frustration between the local order of the fluid and the global order of the crystal [16]. Recent studies have demonstrated that a two-stage selfassembly scheme for triblock patchy particles via tetrahedral clusters promotes crystallization into open crystals, where each particle has a coordination number of six, by suppressing the formation of five- and seven-member rings [17, 18]. Much effort has been placed in devising fabrication routes to diamond-structured colloidal crystals, driven by their applications in visible photonics [1, 2] In this context, the selfassembly of submicrometer colloidal particles has long been recognized as a promising scalable bottom-up approach [3,4,5,6]. The formation of the diamond lattice from tetrahedral patchy particles is hampered by the propensity to form competing open periodic structures for narrow patches or dynamically arrested states for wider patches, leaving a narrow window in design space where diamond crystals may be realized. Our two-component system of designer tetrahedral patchy particles supports a significantly wider range for patch sizes for programmed self-assembly, facilitating experimental fabrication, and offers fundamental insight into crystallization into open lattices
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