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EXAFS Study on Interfacial Structure between Pd Cluster and n-Octadecanethiolate Monolayer: Formation of Mixed Pd-S Interlayer
H. Murayama, N. Ichikuni, Y. Negishi, T. Nagata,
and T. Tsukuda*
Chem. Phys. Lett., 376, 26-32 (2003).
The geometrical structure of the Pd cluster (diameter of ca. 3.1 nm) protected by n-octadecanethiolate monolayer has been investigated by high-resolution TEM (HRTEM), XRD, and EXAFS spectroscopy. The HRTEM and XRD measurements have revealed that the cluster core is comprised of an fcc single crystal of Pd. The mean coordination numbers of the Pd-Pd and Pd-S shells determined by the Pd K-edge EXAFS analysis suggest that the surface of the Pd core is sulfurized to form a mixed Pd-S layer between the thiolate monolayer.
One-Pot Preparation of Subnanometer-Sized Gold Clusters via Reduction and Stabilization by meso-2,3-Dimercaptosuccinic Acid
Y. Negishi and T. Tsukuda*
J. Am. Chem. Soc. (communications), 125, 4046-4047 (2003).
We report herein a simple method to prepare subnanometer-sized gold clusters by the reactions between hydrogen tetrachloroaurate (HAuCl4) and meso-2,3-dimercaptosuccinic acid (DMSA; HO2CCH(SH)CH(SH)CO2H) in water. It is demonstrated that DMSA molecules efficiently reduce the Au(III) species and stabilize the resultant gold clusters. The Au:DMSA clusters, which tend to aggregate into assemblages in water, can be well-isolated each other by ion-pair formation between the carboxyl groups of DMSA and tetraoctylammonium (TOA) cations. This surface modification enables us to examine the core size distributions of the individual clusters by mass spectrometry and TEM. It is revealed that the gold clusters comprised of 10-13 atoms (ca. 0.8 nm) are the main products of the reactions.
Self-Assembly of Si Clusters into Single Crystal Arrangements: Formation of Si10 Cluster Crystals
S. Sato, N. Yamamoto, K. Nakanishi, H. Yao, K.
Kimura, Y. Negishi, and T. Tsukuda
Jpn. J. Appl. Phys., 42, L616-L618 (2003).
Single crystals of Si clusters were created at an air/solution interface or a hydrogen-terminated Si substrate/solution interface using a self-assembly process, which originated from the hydrophobic nature of Si clusters. Mass analysis indicated that the components of the cluster crystals were partially oxidized hydrogenated Si10 clusters. At the interfaces the nearest-neighbor distances between lattice points in the Si cluster crystals were 0.53 nm and 0.60 nm, which are consistent with the diameters of the Si10 clusters. The slight difference in these values seems to be due to variations in the surface passivation of the component Si10 clusters.