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GG3.06 - Induction of Chirality and Chiroptical Activity in Inorganic Nanocrystals Using Biomolecules 
April 8, 2015   10:15am - 10:30am

Chirality is a geometric property of objects that cannot be superimposed onto their mirror images. Chiral structures also give rise to unique chiroptical effects when interacting with polarized light. These properties are fundamental in biomolecular systems, and chiroptical spectroscopy is often used for their characterization. The role of chiral surfaces of inorganic crystals and their interaction with biomolecular systems has been discussed in many different theories that relate to the generation of homochirality in biomolecules. In this talk a somewhat complementary field will be discussed. In the first type of systems that will be described, induction of chiroptical effects in nanocrystals of achiral semiconductor materials using chiral biomolecules will be described.1 This effect is interesting for fundamental studies of exciton - molecular level interactions, as well as exciton level structure characterization. However, it is generally very weak. More recently we introduced the concept of enantioselective synthesis of intrinsically chiral inorganic nanocrystals, which leads to more pronounced effects.2 Many inorganic materials such as quartz, mercury sulfide and tellurium crystallize in chiral space groups with a chiral lattice. Biomolecules can be used to induce enantioselectivity in the nucleation and growth of nanocrystals of these materials. For the case of tellurium, we show that crystal growth in the presence of the small peptide, glutathione, results in nanocrystals where the atomic scale lattice chirality translates to the overall shape chirality on a 100 nm scale.3 This is a unique example for a colloidal chemistry approach for self assembling inorganic nanocrystals, which exhibit chirality at two size hierarchies. These systems may be useful for applications in metamaterials fabrication, asymmetric catalysis, sensing and optical devices. On a more fundamental level, these are excellent model systems for studies of chiral crystallization and separation, and the interaction of chiral biomolecules with chiral crystals. The possible role of chiral inorganic crystals and surfaces in the evolution of biomolecular homochirality has been considered by many researchers. Here it is demonstrated that the opposite effect, of biomolecules affecting chiral inorganic crystallization, is also intriguing. 1.Ben-Moshe, A.; Swarczman, D.; Markovich, G. " Size Dependence of Chiroptical Activity in Colloidal Semiconductor Quantum Dots" ACS Nano 5, 9034-9043 (2011) 2.Ben-Moshe, A.; Govorov, A. O.; Markovich, G. "Enantioselective Synthesis of Intrinsically Chiral Mercury Sulfide Nanocrystals" Angew. Chem. Int. Ed. 52, 1275-1279 (2013) 3.Ben-Moshe, A.; Wolf, S. G.; Bar-Sadan, M.; Houben, L.; Fan, Z.; Govorov, A. O.; Markovich, G. "Enantioselective control of lattice and shape chirality in inorganic nanocrystals using chiral biomolecules" Nat. Comm. 5, 4302 (2014)

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