Toyota Physical and Chemical Research Institute, Japan
Scientific Tracks Abstracts: J Astrophys Aerospace Technol
The evolution of geometrical structures of thiolate (SR)-protected gold clusters, Au n(SR)m, in a n=10-55 size range, was studied by means of 197Au M├?┬Âssbauer spectroscopy. Successful analysis of the Au25 (SR)18 spectrum, based on the crystallographically determined structure, enabled us to estimate quantitatively the numbers of gold atoms coordinated by different numbers (0, 1, and 2) of SR ligands for all the Aun(SR)m clusters. In Au10(SR)10, all the gold atoms are bonded to SR ligands, indicating ├ó┬?┬?Au├ó┬?┬?S(R)├ó┬?┬? cyclic structures. A catenane structure was proposed for Au10(SR)10. At n = 15, gold atoms bonded to a single SR ligand appeared, suggesting the formation of small clusters. At n = 25, a single Au atom without the SR ligation appeared, consistent with the formation of an icosahedral Au13 core protected by six staples, ├ó┬?┬?S(R)├ó┬?┬?[Au├ó┬?┬?S(R)├ó┬?┬?]2. At n = 39, the number of Au atoms without the SR ligation increases from one to two, and the 197Au M├?┬Âssbauer spectrum is consistent with the face-fused bi-icosahedral Au23 core. These results demonstrate that 197Au M├?┬Âssbauer spectroscopy will provide detailed information on the structures of thiolate-protected gold clusters whose single crystals are difficult to make.
Norimichi Kojima has completed his PhD from Kyoto University, Japan. In 1994, he was appointed as a full Professor, and the Vice-President between 2009 and 2011, the University of Tokyo, and became the Emeritus Professor in 2015. After retiring from the University of Tokyo, he moved to Toyota Physical and Chemical Research Institute, as a fellow. His current interests include the electronic and structural properties of nanoparticles by means of Mössbauer Spectroscopy.
Email: [email protected]ken.jp