Shape evolutions of nanocrystals

Abstract

While the shape of the nanocrystals plays a critical role in determining their properties, the controllability of their shapes is underdeveloped. Hence, rational synthetic strategies for nanoscale building blocks with well-defined shape remain issues to be solved for undiscovered novel properties. In this study, a solution based method for the development of new architectures of PbS has been successfully explored for semiconductor nanocrystals. We demonstrate the discovery of transient novel nanostructures such as well-defined stars and their shape evolutions in between anisotropic (i.e. rods) and isotropic (i.e. cubes) systems. A variety of nanostructures of colloidal PbS including monorods, multipods, stars, and truncated cubes are obtained and the crucial shape guiding factors involved in determining their shapes are elucidated via systematic approaches. We show that various features of the final nanostructures including shape, size, and aspect ratios are ultimately determined by sensitive variables in our synthetic route such as the type of molecular precursor for PbS, capping molecule, the ratio of capping molecule to molecular precursor, and the overall growth conditions (kinetic vs. thermodynamic).