Anisotropic nanocrystal shape and ligand design for co-assembly

Abstract

The use of nanocrystal (NC) building blocks to create metamaterials is a powerful approach to access emergent materials. Given the immense library of materials choices, progress in this area for anisotropic NCs is limited by the lack of co-assembly design principles. Here, we use a rational design approach to guide the co-assembly of two such anisotropic systems. We modulate the removal of geometrical incompatibilities between NCs by tuning the ligand shell, taking advantage of the lock-and-key motifs between emergent shapes of the ligand coating to subvert phase separation. Using a combination of theory, simulation, and experiments, we use our strategy to achieve co-assembly of a binary system of cubes and triangular plates and a secondary system involving two two-dimensional (2D) nanoplates. This theory-guided approach to NC assembly has the potential to direct materials choices for targeted binary co-assembly.

Shape-Directed Co-Assembly of Lead Halide Perovskite Nanocubes with Dielectric Nanodisks into Binary Nanocrystal Superlattices

“…Similar packing, driven by the strong face-to-face interactions, has been reported for LaF 3 triangular plates sandwiched between PbTe cubes. 20 With the smallest LaF 3 disks (6.5 nm), the space-filling in the ReO 3 lattice is compromised. Additional voids that emerge in the ReO 3 -lattice can be occupied by the additional disks (Figures 10i,j and S11g-i).…”

“…11−13 Although dozens of periodic and quasicrystalline SL structures were reported for binary mixtures of spherical NCs, examples of multicomponent SLs comprising nonspherical NCs were reported only for mixtures of spherical NCs with triangular nanoplates, 14 nanorods, 15 octapods 16 and nanocubes, 17 rhombic nanoplates with tripodal nanoplates, 18 nanodisks with nanorods, 19 and nanocubes with triangular nanoplates. 20 To this end, a range of shape-engineered and size-uniform NCs are synthetically accessible as building blocks for SLs; 21 for instance, rod-shaped or polyhedral metallic NCs, 22 faceted lanthanide fluoride nanoplates, 23 rod-and prism-shaped lanthanide-doped fluoride NCs, 24 diverse Cd chalcogenide morphologies (nanotetrahedra, 25 nanorods, 26,27 nanoplatelets 28,29 ), and lead halide perovskite nanocubes. 30,31 NC self-assembly into SLs is driven by both energetic interactions and entropic contributions.…”

“…Inorganic nanocrystals (NCs) bridge the gap between bulk solids and atoms or molecules due to their size- and morphology-dependent properties, such as optical, plasmonic, and magnetic properties. , Self-assembly of NCs into long-range ordered superlattices (SLs), comprising one or more kinds of NCs, holds great promise for creating metamaterials with functionalities, which arise from the addition or synergy of the properties of individual building blocks (i.e., electronic, plasmonic or magnetic coupling, etc . ). , Collective properties could be tunable through the interparticle distance, relative NC orientation, and interparticle medium, as it was demonstrated for band-like charge transport in SLs of semiconductor NCs, − dipolar interactions in arrays of magnetic NCs, − or near-field couplings in SLs of plasmonic NCs. − Although dozens of periodic and quasicrystalline SL structures were reported for binary mixtures of spherical NCs, examples of multicomponent SLs comprising nonspherical NCs were reported only for mixtures of spherical NCs with triangular nanoplates, nanorods, octapods and nanocubes, rhombic nanoplates with tripodal nanoplates, nanodisks with nanorods, and nanocubes with triangular nanoplates . To this end, a range of shape-engineered and size-uniform NCs are synthetically accessible as building blocks for SLs; for instance, rod-shaped or polyhedral metallic NCs, faceted lanthanide fluoride nanoplates, rod- and prism-shaped lanthanide-doped fluoride NCs, diverse Cd chalcogenide morphologies (nanotetrahedra, nanorods, , nanoplatelets , ), and lead halide perovskite nanocubes. , …”

Mismatched ligand density enables ordered assembly of mixed-dimensional, cross-species materials

“…Many existing works on multicomponent ordered self-assembly have focused on colloidal nanocrystals (NCs) (8)(9)(10)(11), mainly because of the ready access to various NC building blocks (12,13). As one of the most notable examples, coassembly of two different-sized NCs has led to binary superlattices with a rich array of structures (14)(15)(16)(17)(18)(19)(20)(21)(22). As the field of colloidal assembly continues to advance, there is an increasing need to integrate mixed-dimensional, cross-species materials in a predictable and controllable manner, as this provides tremendous opportunities to access emergent properties that are not otherwise presented in pure-NC assemblies (23)(24)(25).…”

Structural Diversity in Multicomponent Nanocrystal Superlattices Comprising Lead Halide Perovskite Nanocubes

“…These are binary lamellar SL of shape-complementary nanoplates, 33 several columnar SLs from the mixtures of nanodisks and nanorods, 36 , 37 and, very recently, thin-film SLs from PbTe cubes coassembled with triangular nanoplates. 38 …”