Establishing the Rules for the Organization and Crystallization of Colloidal Anisotropic Nanoparticles

Colloidal assembly of nanoscale objects enables the synthesis of a wide range of hierarchical structures simply by changing the size, shape, and surface chemistry of the nanomaterials. Over the past decade, advances in colloidal nanoparticle synthesis have provided access to a library of well-defined nanoscale building blocks. The organization of isotropic nanoparticles, i.e., uniformly functionalized nanoscale spheres or pseudo-spheres, has been extensively studied and design rules have been empirically set or theoretically explained. In contrast, very few design rules exist for anisotropic nanoparticles, i.e., convex, concave, and hollow polyhedra. Herein, we report synthetic methodologies for the assembly of designer 2D and 3D nanoparticle superlattices using DNA-functionalized polyhedral nanoparticles and a series of geometry-inspired strategies. For, example, in an effort to develop methods for arbitrarily arranging polyhedral nanoparticles on flat substrates with nanometer precision, we created a customized series of surface-bound templates that guide the particles to their intended positions through a combination of shape complementarity and DNA ligand complementarity. We show that tunable nanoparticle-based metasurfaces made in this manner can rapidly respond to changes in solution polarity, a promising route to reconfigurable 2D optical devices. To achieve the designer 3D nanoscale architectures, we have developed a series of polyethylene glycol-DNA ligands that enabled the assembly of polyhedral nanoparticles into ordered and dense-packed superlattices. Taking advantage of the highly customizable nature of oligonucleotides and geometry-inspired designs, polyhedral nanoparticles of different sizes and shapes were densely assembled/co-assembled. Using these design strategies, we have discovered eleven new structures to the DNA-engineered colloidal crystal family, including the first colloidal quasicrystal engineered with DNA. Moreover, we have shown the ability to inversely design and experimentally produce ordered superlattices based on polyhedral complementarity. Importantly, these colloidal organization platforms will enable the systematic exploration of structure-function relationships, as well as the on-demand design and fabrication of highly ordered nanoscale architectures for optical and mechanical metamaterial applications.