Pressure-Driven Interplay between Soft and Hard Components and Resultant Anisotropic and Topological Responses in a Pt Nanocube Assembled Rhombohedral Superlattice

Synchrotron-based in situ pressure small- and wide-angle X-ray scattering and associated strain analysis reveal a pressure-driven anisotropic strain distribution across a Pt nanocube (NC) assembled supercrystal that has an obtuse rhombohedral superlattice. This strain anisotropy is largely controlled by the rational interplay between soft organic molecules and hard NC cores localized at various ratios in the four types of decoded NC arrangements. Upon compression below 10 GPa, the strain appears as a superlattice shrinkage, which is developed mainly at molecule-rich regimes in the facet-facet and nondirect-contact configurations of NC arrangement. Above 10 GPa, an anisotropic strain enhances and accordingly starts an apparent superlattice shrinkage at molecule-poor regimes in the corner-corner and edge-edge configurations, whereas an unusual superlattice expansion is simultaneously triggered in molecule-rich regimes. Upon the release of pressure, a normal superlattice expansion arises only at molecule-rich regimes, but a constant superlattice remains at molecule-poor regions, and below 2 GPa, a discontinuous jump occurs. In situ electrical resistance measurements of single supercrystals under pressure and electron microscopy imaging of harvested samples further reveal a pressure-induced phase switching between the insulator and conductor in a low dimension (1D or 2D) as defined at 10 GPa under compression and 2 GPa under decompression. This typical phase switching originates from a pressure-driven NC attachment and weak fusion and subsequently a decompression-induced NC detachment. This consequence is largely controlled by the development of a stable 2D Maxwell-like topological lattice through a small fraction of facet-facet and edge-edge attachments between slightly deflected NCs. These results provide insights into the anisotropic interplay between soft and hard components in nanobased architectures with response to the enhancement and manifestation of material properties.

Automated summary

Synchrotron-based in situ pressure small- and wide-angle X-ray scattering and strain analysis revealed a pressure-driven anisotropic strain distribution across a Pt nanocube assembled supercrystal, with the strain anisotropy largely controlled by the interplay between soft organic molecules and hard nanocube cores.