Relative Stability of Crystal and Amorphous States for Tetrahedrally Coordinated Particles and Nanostructures

DNA nanotechnology has blossomed in the last decade, with applications including the creation of biosensors, targeted drug delivery using DNA “packaging”, and the selfassembly of optical materials. Much attention has recently focused on using DNA as a linking agent to engineer nanoparticle (NP) lattices with specific geometries. There has been success generating a broad range of crystal lattices, but the formation of a one of the most basic symmetry types, the tetrahedral or diamond lattice, has been particularly challenging. We use molecular simulations to examine a combination of NP uniformly coated with DNA that connect via linking units that incorporate tetrahedral structure. We find that the nonspecific interactions can play an important role in the stabilization of the diamond structure. We test the stability of spherical NP-DNA complexes with tetrahedral linkers in a 1:1 ratio, which allow for a variety of lattices, including a diamond structure. Interestingly, this scheme can result in a diamond ordering of NP by an interpenetrating network of DNA, each with diamond connectivity. The possibility of such interpenetrating structures was recently postulated by research from Wesleyan. Finally, we examine a simplified model for NP with highly directional interactions to provide a general framework to understand the balance between diamond and more densely packed lattice structures.