Colloidal crystals with diamond symmetry at optical lengthscales

Abstract

Future optical materials promise to do for photonics what semiconductors did for electronics, but the challenge has long been in creating the structure they require—a regular, three-dimensional array of transparent microspheres arranged like the atoms in a diamond crystal. Here we demonstrate a simple approach for spontaneously growing double-diamond (or B32) crystals that contain a suitable diamond structure, using DNA to direct the self-assembly process. While diamond symmetry crystals have been grown from much smaller nanoparticles, none of those previous methods suffice for the larger particles needed for photonic applications, whose size must be comparable to the wavelength of visible light. Intriguingly, the crystals we observe do not readily form in previously validated simulations; nor have they been predicted theoretically. This finding suggests that other unexpected microstructures may be accessible using this approach and bodes well for future efforts to inexpensively mass-produce metamaterials for an array of photonic applications.

Nanoparticle Superlattices as Quasi-Frank-Kasper Phases

“…Still, rigorous resolution to these questions will require additional work. Studies in µ-sized colloidal self-assembly [43], including DNA [44,45], where according to the OTM [18] particles cannot display non-hard sphere behaviour, may provide even better models to investigate the tendency towards icosahedral order than the NCs discussed in this study, as some phases with f ico = 0 become suppressed. SC REGIME SC REGIME ICOSAHEDRAL REGIME …”

Programmable Atom Equivalents: Atomic Crystallization as a Framework for Synthesizing Nanoparticle Superlattices

“…PAEs have been synthesized on both the nanoscale (2–1000 nm) and microscale with the same basic DNA design, and all follow the same design rules as particles in the ≈10–50 nm core size regime (Figure ). The key rule that governs the crystallization of different PAE sizes is that the overall hydrodynamic radius of the PAE determines its binding behavior, not the core size alone .…”

“…While the predominant driving force that dictated the thermodynamically favorable lattice structure for a given set of PAEs was initially discovered to be almost entirely an enthalpic maximization of DNA binding, it was later found that entropic effects could be increased with flexible DNA linkers, thereby inducing self‐complementary PAEs to form a bcc lattice even though this structure represents a lower packing density than the prior fcc structures that had been obtained in unary systems . Making the core–core interactions appreciable in scale, one study created the binary phase isostructural to sodium‐thallium (NaTl) . Additionally, it was discovered that higher energy unit cells could be synthesized in a kinetically trapped state under the correct conditions (e.g., hexagonal close packed (hcp) lattices form as a kinetic structure for PAEs whose thermodynamically preferred phase is fcc) .…”

Layer-by-layer assembly of patchy particles as a route to nontrivial structures

“…This structure can also be viewed as Double Diamond (DD) lattices, which enables its conversion to a regular diamond through partial particle deletion. Interestingly, self-assembly of DD lattice has been recently observed in conventional (non-patch) colloidal system with DNA-mediated interaction, but the mechanism behind its formation remains obscure [26].…”