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OPTICALLY ACTIVE INTRINSICALLY CHIRAL INORGANIC NANOSTRUCTURES

Optical activity in inorganic nanostructures can be made much more intense than in chiral molecules. It may be the result of forming nanostructures with chiral shapes made of metals or semiconductors, but also arise from interaction of achiral inorganic nanostructures with chiral molecules.

We have recently shown that it is possible to perform an enantioselective synthesis of inorganic nanostructures made of intrinsically chiral crystals, such as a-HgS [1], Te and Se [2]. These crystals, belonging to the P3₁21 (or P3₂21) chiral space group, were grown as nanocrystals in the presence of thiolated chiral molecules, such as cysteine, penicillamine or glutathione. This led to a preference in the growth of the nanocrystals towards a certain handedness and consequent strong optical activity.

Furthermore, in the case of Te nanostructures particular synthesis conditions led to overall chiral shape of the elongated nanostructures, expressed as a twist on the scale of the size of the nanostructures of the order of 100 nm. These nanostructures behaved as nanoscale chiral optical resonators, with tunable optical response, depending on their length [2]. Finally, the Te could be easily converted to other materials, such as gold or silver telluride [2], while preserving the chiral shape, opening the way to the formation of strongly optically active nanostructures made of various plasmonic or semiconductor materials.

[1] Ben-Moshe, A.; Govorov, A. O.; Markovich, G. Angew. Chem. Int. Ed. 2012, 52, 1275.

[2] Ben-Moshe, A.; Grayer Wolf, S.; Bar Sadan, M.; Houben, L.; Fan, Z.; Govorov, A. O.; Markovich, G. Nature Comm. 2014, 5, 4302.