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MM10.02 - Enantioselective Control of Lattice and Shape Chirality in Inorganic Nanocrystals Using Chiral Biomolecules 
April 9, 2015   1:45pm - 2:00pm

In the last decade there has been a lot of interest in inorganic nanosystems that exhibit chirality and chiroptical activity.1 Three different approaches have been demonstrated for that purpose. First, induction of weak chiroptical effects in the plasmon or exciton resonances of nanocrystals of achiral materials with achiral shapes (such as gold, silver and cadmium/zinc chalcogenides), when these are capped with chiral surfactant molecules. Second, formation of chiral shaped nanostructures, mostly by lithographic or vapor deposition methods. Third, assembly of achiral nanocrystals into chiral superstructures. In all these systems the lattice symmetry is high and the crystal structure itself is achiral. More recently we have demonstrated an alternative approach for realization of chirality and stronger chiroptical effects in inorganic nanostructures. In our work we study inorganic materials that crystallize in chiral space groups, such as mercury sulfide,2 tellurium and selenium.3 The handedness of the crystal can be controlled when nanocrystals of these materials are grown in the presence of strongly binding chiral biomolecules. Furthermore, in the case of tellurium, the lattice chirality can be translated to the overall shape, on a 100 nm scale. Hence, control over chirality at two different size hierarchies is achieved. This is a unique demonstration of formation of chiral shapes in colloidal synthesis of inorganic nanocrystals. The chiral inorganic systems evolve by initial formation of very small clusters followed by a unique self-assembly process. As a result, interesting analogies to molecular crystals could be looked at. Different stages of nucleation and growth can be conveniently monitored by spectroscopic measurements in solution (as opposed to bulk crystals where this is more challenging). The shape and crystal structure are also easily imaged on the nanometer scale by electron microscopy (as opposed to organic crystals where this is more challenging). These new materials should be useful for a range of applications such as metamaterials fabrication, optics and asymmetric catalysis. On a more fundamental level, we believe that these are excellent model systems for studies of chiral crystallization and separation, and the interaction of chiral biomolecules with chiral crystals. 1.Ben-Moshe, A.; Maoz, B. M.; Govorov, A. O.; Markovich, G. "Chirality and Chiroptical Effects in Inorganic Nanocrystal Systems with Plasmon and Exciton Resonances" Chem. Soc. Rev. 42, 7028-7041 (2013). 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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