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Formation of Pdn(SR)m Clusters (n<60) in the Reactions of PdCl2 and RSH (R=n-C18H37, n-C12H25)
Y. Negishi, H. Murayama, and T. Tsukuda*
Chem. Phys. Lett., 366, 561-566 (2002).
Mass spectroscopic analysis revealed that Pd clusters passivated by thiolates and the stoichiometric thiolate complexes, Pdn(SR)2n (n=5, 6), are formed in the reactions between palladium chloride and n-alkanethiols (RSH: R=n-C18H37, n-C12H25) in toluene. The Pd clusters thus formed are formulated as Pdn(SR)m with m~0.6n. The cluster sizes, distributed in the range of 5<n<60, are consistent with their core diameters of ~1 nm observed by TEM. A gap of ~2 eV was observed in the optical transition of the Pdn(SR)m clusters showing the emergence of non-metallic properties as a result of size reduction.
Structural Evolution in (CO2)n Clusters (n<103) as Studied by Mass Spectrometry
Y. Negishi, T. Nagata, and T. Tsukuda*
Chem. Phys. Lett., 364, 127-132 (2002).
The mass distributions of (CO2)n- produced by electron-impact ionization of a free jet have been measured up to n~103. Several intensity anomalies observed in a small size range are ascribed to the stabilities of the negative ions. In contrast, a series of humps are clearly discernible in the range of n > 100, which reflects the abundance of neutral (CO2)n. The intensity oscillations are analyzed in the context of "geometrical shell closings". The analysis reveals that the (CO2)n clusters with n >~80 have truncated forms of an fcc crystal, most likely a cuboctahedral motif.