Controlling Nanoparticle Orientations in the Self-Assembly of Patchy Quantum Dot-Gold Heterostructural Nanocrystals

Abstract

Self-assembly of nanocrystals is a promising route for creating macroscale materials that derive function from the properties of their nanoscale building blocks. While much progress has been made assembling nanocrystals into different superlattices, controlling the relative orientations of nanocrystals in those lattices remains a challenge. Here, we combine experiments with computer simulations to study the self-assembly of patchy heterostructural nanocrystals (HNCs), consisting of near-spherical quantum dots decorated with regular arrangements of small gold satellites, into close-packed superlattices with pronounced orientational alignment of HNCs. Our simulations indicate that the orientational alignment is caused by van der Waals interactions between gold patches and is sensitive to the interparticle distance in the superlattice. We demonstrate experimentally that the degree and type of orientational alignment can be controlled by changing ligand populations on HNCs. This study provides guidance for the design and fabrication of nanocrystal superlattices with enhanced structural control.

Dictating Nanoparticle Assembly via Systems-Level Control of Molecular Multivalency

“…Rather, these structures are indeed an example of a systems-level design process, where the morphology at each length scale (molecular, nano, and meso) is both an effect and a cause of behavior at the others. It is important to again note that this system-derived change in NCT coordination environment is different than prior particle assembly schemes that use "patchy" particles 23,25,38 . These methods typically control particle coordination numbers by breaking the overall symmetry of the ligand shell around a particle.…”

Supercrystallography-Based Decoding of Structure and Driving Force of Nanocrystal Assembly

“…In the case of materials development, a designable processing approach can be executed by application of an external stimulus on the pre-defined superlattice orientation of supercrystal to develop advanced materials with a new type of mesoscale architectures. As witnessed in recent pressure-processing studies on NC supercrystals [34,61,62,63,64,65,66], it can be foreseen that this superlattice-based designable processing of materials will be certainly opening up a window for the designable fabrication of the next generation of advanced materials with an increased structural complexity and improved functionality [67,68].…”

Patchy Nanoparticle Synthesis and Self-Assembly

“…The tip-patched nanoprisms could assemble into large-scale 2D lattice if the directional repulsion introduced by patches is controlled to render specific angle between the particles. Zhu et al [93] achieved the fcc superlattices from near-spherical quantum dots patched with gold satellites (Figure 4f and j), in which the orientations of individual nanoparticles are aligned. Using both small-angle X-ray scattering (SAXS, Figure 4g and k) and wide-angle electron diffraction (Figure 4h, i, l and m), they showed that by varying the ligand thickness; the degree of alignment can be controlled through the distance-dependent vdW attraction.…”

“…From finite-element calculations, they confirmed the most favorable alignment of two nanodumbbells is the cross-stack of the particles by their patches, consistent with the unit structure of the lattice. Zhu et al [93] reported quantum dots decorated with gold patches and assembled them into close-packed structures. The molecular dynamics simulation not only reproduced their superlattices but also suggested a means of tuning the orientational alignment of the building blocks in the superlattice by varying distance-depended vdW force between the gold patches.…”