Experimental Determination of the Chiral and Achiral Shape Diagrams of Tellurium Nanocrystals.

The interface between chirality and crystallization and mechanisms by which chirality propagates from crystal structure to overall shapes of crystals are a key topic in crystallography and stereochemistry. Recently, nanocrystals attracted attention as useful model systems for this kind of studies. Specifically, tellurium nanocrystals have been used to address questions on relations between chirality of the crystal structure and that of the overall shape. Previous studies of this system did not offer a comprehensive shape diagram and did not survey all the factors that determine whether shapes that form are chiral or not. In the current report, the distribution of chiral and achiral shapes in this system as a function of different physical and chemical parameters is determined experimentally. It is shown that there is a common logic for formation of chiral shapes, that is, growth at conditions that favor the growth of more reactive nuclei. The experiments also reveal more morphologies than previously encountered, suggesting that a systematic change of conditions in nanocrystal growth is key for identifying morphologies that exist only in a narrow range of conditions.