21 The past year has been amazingly productive for Dr. Assaf Ben Moshe. Marking his first year as faculty at Bar-Ilan’s Institute of Nanotechnology & Advanced Materials, Ben Moshe is flush with his first ERC grant that will enable him to study the chirality of crystals; and he is the proud “abba” to a second child born in June 2023. Ben Moshe is pursuing answers to questions about crystalline forms that were first articulated by Louis Pasteur in 1848. While investigating paratartaric acid, Pasteur discovered that it generated two types of crystals. One resembled the crystals found in tartaric acid, while the other was a mirrored version. These crystals were later termed “chiral,” derived from the Greek word “kheir,” meaning hand. To grasp chirality, imagine holding up two things in front of a mirror: a white golf ball and your hand. The mirror reflection of the ball looks just like the ball itself. If you take out that reflection and put it against the ball, they match perfectly. However, if you try the same with your hand, no matter how hard you try, the mirror image won’t fit into your real hand; they will always remain mirror images. Pasteur’s observations gave rise to the birth of modern stereochemistry and topics in crystallography that deal with the propagation of symmetry across length scales. Ben Moshe works with inorganic metallic and semiconducting materials that have beneficial applications in science and technology. “We focus on questions that relate to how these materials form, how they develop their shapes,” he explains. “We’re interested in the crystal growth mechanisms.” Using advanced nanotech tools to peer at crystals the size of a few nanometers to a few hundred nanometers allows Ben Moshe to approach the vital and historical question of how crystals form with a new perspective. “By working with nanoscale model systems, we have the ability to look at details of crystals at a very high resolution,” continues Ben Moshe. “Meaning, we can look at the crystal as it grows and eventually, as an end goal, we’ll understand where every atom is positioned at every point in time.” Ben Moshe’s upcoming research will focus on a nanoscale system using advanced electron microscopy to explore a unique phenomenon that he first observed as a postdoc at the University of California, Berkley. Unlike conventional cases, chiral crystals emerge from a system composed of chiral molecules, driven not by their inherent chirality, but rather by common imperfections present in crystals. The significance of these imperfections in shaping chiral forms has not been previously considered. The ERC project aims to delve extensively into the role of imperfections in the formation of chiral shapes which may potentially reevaluate Pasteur’s experiment and its interpretation. The primary objectives are twofold: • To gain a comprehensive insight into the broader relevance and significance of the newfound mechanism in the realm of scientific history. • From a synthetic perspective, the project seeks to harness the understanding of these imperfections to exert control over the growth of chiral-shaped crystals across a diverse range of materials. This manipulation of growth directionality—left or right—holds substantial promise for contemporary applications spanning asymmetric catalysis, optoelectronics, spintronics, and various other scientific domains. As Ben Moshe humbly clarifies, “We are trying to answer old questions with new tools.” “By working with nanoscale model systems, we have the ability to look at details of crystals at a very high resolution”
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