Electron Microscopic Observation of an Icosahedral Au_{13} Core in Au_{25}(SePh)_{18} and Reversible Isomerization between Icosahedral and Face-Centered Cubic Cores in Au_{144}(SC_{2}H_{4}Ph)_{60}
R. Takahata, S. Yamazoe, Y. Maehara, K. Yamazaki, S. Takano, W. Kurashige, Y. Negishi, K. Gohara, T. Tsukuda
J. Phys. Chem. C, accepted
The atomic structures of Au_{25}(SC_{2}H_{4}Ph)_{18}, Au_{25}(SePh)_{18}, and Au_{144}(SC_{2}H_{4}Ph)_{60}, for which the crystal structures have been solved, were examined by aberration-corrected transmission electron microscopy (ACTEM). Time-lapse ACTEM images of Au_{25}(SePh)_{18} exhibited characteristic patterns for the I_{h} Au_{13} core more frequently compared to Au_{25}(SC_{2}H_{4}Ph)_{18} at a dose rate (DR) = 4 pA/cm~{2}. In contrast, time-lapse images of Au_{144}(SC_{2}H_{4}Ph)_{60} randomly showed two types of patterns for the I_{h} and fcc cores at DR = 4 pA/cm~{2}, indicating that Au_{144}(SC_{2}H_{4}Ph)_{60} can be interconverted between the two isomeric forms without fragmentation. We proposed that the I_{h} isomer is more stable than the fcc isomer in Au_{144}(SC_{2}H_{4}Ph)_{60} based on population analysis of the images of individual isomers.