Enantioselective screw-dislocation-mediated growth of chiral nanocrystals

Ziel

In many scientific disciplines structural symmetry considerations are key. Specifically, mechanisms by which symmetry translates from atomic and molecular building blocks to crystal structures and shapes attract a great deal of attention. A fascinating aspect of this is related to chirality. Louis Pasteurs monumental work, reported in 1848, on formation of chiral shapes in crystals made from chiral molecules, led to an intuition that chiral building blocks naturally lead to chiral shapes in crystals. Yet, after countless observations ever since of crystals with chiral shapes, mechanisms of their formation are understood to be often more complex and elusive than first imagined. In work proposed here, nanocrystals will serve as convenient model systems for studies of the interplay between crystallization and chiral shape formation. They are beneficial for this purpose as they can mimic embryonic stages of crystal growth, exhibiting structural details that can be retrieved at remarkable resolution, that are often hidden in macroscopic crystals. Specifically, I will focus on a universal mechanism by which crystals grow at low concentrations of building blocks, assisted by a common type of imperfections, namely, screw dislocations. I will tackle key unresolved questions on the interplay between chirality, screw dislocations and crystallization. First, how does screw-dislocation-mediated growth proceed in the presence of chiral additives that can bind to growing crystals, and how do these dislocations even come to be? Second, how general is this mechanism, and how often was it overlooked throughout history? The results obtained in this work, on the one hand, will lead to a general design principle to control nano-scale chirality in many inorganic materials, beneficial for novel applications. On the other hand, they have the potential to elucidate a missing piece of crystal growth theory and lead to a paradigm shift in our understanding of shape chirality in crystals.