10-05/06 :: May/June 2010

nanotimes News in Brief

Gold Cluster // Secrets of a Chiral Gold Nanocluster Unveiled

R

esearchers from the University of Jyvskyl, Finland, Hokkaido University, Japan, University of Jyvs-

kyl, Finland, and Kansas State University, USA, studied structural, electronic, and optical properties of the thiolate-protected Au38

(SR)24 ).

ty-functional theory computations (R = CH3 and R = C6H13 C12H25

) and by powder X-ray crystallography (R =

The study demonstrates a new mechanism for the strong chiral response of thiolate-protected gold clusters with achiral metal cores and ligands.

The theoretical structure was confirmed via com- parison to experimental results obtained by X-ray diffraction from powder samples of the pure cluster material.

The synthesis of organothiolate-protected gold clu- sters of 1 to 3nm in size has been well known since the mid-1990s, but the detailed atomic structure of the most stable clusters remained a mystery until very recently. In 2007, the structure of the first cluster that contained 102 gold atoms was resolved at Stanford University using single-crystal X-ray crystallography. The cluster now resolved has exactly 38 gold atoms and 24 organothiolate molecules covering its surface and it is just about one nanometer in size. The shape of the particle is prolate (cigar-like), and 15 out if its 38 gold atoms reside on the protective surface layer

cluster by densi-

chemically bound with the thiolate molecules. The gold-thiolate layer has a chiral structure, which is re- sponsible for the observed chiral properties. The chi- ral structure has two structural forms (enantiomers), the so-called right-handed and left-handed forms, in a way comparable to a twist in a DNA molecule or to a twist in the staircase structure of a block of flats. © JACS

Olga Lopez-Acevedo, Hironori Tsunoyama, Tatsuya Tsu- kuda, Hannu Hkkinen and Christine M. Aikens: Chirality and Electronic Structure of the Thiolate-Protected Au38 Nanocluster, In: Journal of the American Chemical Society, ASAP, May 25, 2010, DOI:10.1021/ja102934q: http://dx.doi.org/10.1021/ja102934q

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