Twin Pathways: Discerning the Origins of Multiply Twinned Colloidal Nanoparticles

Abstract

The structure of multiply twinned particles (MTPs) provides an example of how specific crystallographic features dictate the geometric shape of finite‐sized crystals. The formation of MTPs during colloidal synthesis can occur through at least two different pathways: 1) growth from multiply twinned seeds or 2) the stepwise formation of new twin boundaries on single‐crystalline seeds (either by particle overgrowth or multiparticle attachment). By utilizing in situ transmission electron microscopy, recent studies have provided real‐time evidence for both pathways. Looking forward, the knowledge of specific evolution pathways that occur under a given synthetic condition will aid in the design of robust MTP syntheses. More importantly, further studies pertaining to the structural evolution and energetics of nanoparticles are needed to provide a complete understanding of MTP formation pathways.

Colloidal Synthesis of Metal Nanocrystals: From Asymmetrical Growth to Symmetry Breaking

“…Multiply-twinned nanocrystals, including those with decahedral ( D 5h ) and icosahedral ( I h ) shapes (section ), are remarkable structures in terms of both geometric shape and atomic arrangement due to the unique assembly of different numbers of single-crystal apex- and facet-sharing tetrahedral subunits. These nanocrystals can be formed through at least two pathways: (i) direct nucleation into 5-fold and 20-fold twinned seeds and subsequent layer-by-layer growth, or (ii) stepwise formation of new twin boundaries on single-crystal seeds via atomic growth or attachment . The latter case can be considered as a case of symmetry reduction for single-crystal seeds, which is discussed in section .…”

“…These nanocrystals can be formed through at least two pathways: (i) direct nucleation into 5-fold and 20-fold twinned seeds and subsequent layer-by-layer growth, or (ii) stepwise formation of new twin boundaries on single-crystal seeds via atomic growth or attachment. 315 The latter case can be considered as a case of symmetry reduction for single-crystal seeds, which is discussed in section 4.1. Although the actual formation pathway of these nanocrystals is still under debate, their unique symmetry is widely used in seed-mediated growth to produce asymmetrical nanostructures hard to obtain through traditional means.…”

Motif-to-Core Nucleation in a Decahedral Evolution Pattern

“…In this context, monolayer-protected metal clusters (MPCs, wherein the metallic core is protected by an organic layer) represent an intriguing category; their atomic precision (with X-ray single crystal diffraction, mass spectra, etc.) and the molecular-like physicochemical properties have provided sound proof to the traditional theories such as plasmonics and size-effect − and are pivotal to elucidating the inherent structure–property correlations at a molecular scale.…”