Ligand-Induced Incompatible Curvatures Control Ultrathin Nanoplatelet Polymorphism and Chirality

TL;DR

This study reveals how ligand interactions induce incompatible curvatures in nanocrystal surfaces, enabling control over nanoplatelet shapes and chirality, advancing the rational design of dynamic nanostructures.

Contribution

It introduces a fundamental framework linking ligand-induced curvature to nanoplatelet polymorphism and chirality, enabling predictive design of nanostructure shapes.

Findings

Ligand adsorption causes incompatible curvatures leading to chiral shapes.

A transition between helicoids and helical ribbons occurs at a critical width.

Effective curvature parameter encodes ligand-surface interaction details.

Abstract

The ability of thin materials to shape-shift is a common occurrence that leads to dynamic pattern formation and function in natural and man-made structures. However, harnessing this concept to design inorganic structures at the nanoscale rationally has remained far from reach due to a lack of fundamental understanding of the essential physical components. Here, we show that the interaction between organic ligands and the nanocrystal surface is responsible for the full range of chiral shapes seen in colloidal nanoplatelets. The adsorption of ligands results in incompatible curvatures on the top and bottom surfaces of NPL, causing them to deform into helico\"ids, helical ribbons, or tubes depending on the lateral dimensions and crystallographic orientation of the NPL. We demonstrate that nanoplatelets belong to the broad class of geometrically frustrated assemblies and exhibit one of their hallmark features: a transition between helico\"ids and helical ribbons at a critical width. The effective curvature $\bar{\kappa}$ is the single aggregate parameter that encodes the details of the ligand/surface interaction, determining the nanoplatelets' geometry for a given width and crystallographic orientation. The conceptual framework described here will aid the rational design of dynamic, chiral nanostructures with high fundamental and practical relevance.