| In recent years, the noble metals nanoclusters have been attracted considerable research interest as an emerging discipline in the nanoscience by scientists. Atomically precise alloy nanoclusters have recently attracted considerable research interest. These ultrasmall nanoclusters are small enough to confine their electrons and exhibit molecule-like properties. Owing to the synergistic effects in such systems, the stability and catalytic and opticalproperties are often dramatically changedThrough know about noble metals nano clusters gradually thorough by researchers, the preparation method of noble metal nano clusters has been quite mature by us. Au nano clusters protected by thiolate have been extensively studied and a number of the gold-thiolate nanoclusters have been synthetized. Due to the backward of characterization method about the gold nano clusters which protected by thiolate, the characterization method of crystal structure of the gold-thiolate nanoclusters is a difficult problem. In 2008, the gold nanocluster AU102 protected by thiolate have been synthetic and reported by Jadizinsky. It is to note that, this crystal structure of gold nanoclusters is reported for the first time in the gold nanoclusters which protected by thiolate. And then, the kinds of crystal structure of gold nanoclusters have been reported more and more. To date, a number of crystal structures of the gold-thiolate nanoclusters such as Au18, Au20, Au23, Au24, Au25, Au28, Au30, Au36, Au38, Au40, Au44, Aus2, Au102, Au130, and Au133 have been characterized. On the basis of known the crystal structure of gold nanoclusters, the properties and applications of gold nanoclusters have a wide range of research. And Au25 have been attracted more interests of scientists due to it have a particularity structure and more stability. Detailed content is as follows:1. A metal exchange method for thiolate-protected tri-metal MiAgxAu24-x(SR)180 (M = Cd/Hg) nanoclusters. In this chapter, we report the first thiolate-protected tri-metal nanoclusters (M1AgxAu24-x(SR)180, M= Cd/Hg, R= C2H4Ph) by a two-step metal exchange. Pure Au25(SR)18- nanoclusters were first reacted with an AgSR complex, which yielded AgxAu25-x(SR)18- nanoclusters. The latter was then reacted with a Cd or Hg thiolate complex to obtain the tri-metallic MiAgxAu24-x(SR)180 (M= Cd/Hg) nanoclusters. The ESI-MS spectrum indicates that the Cd atom is doped at the center of the AgxAu25-x(SR)18- nanocluster. This study also provides a new way to find the doping position of Cd atoms using silvers the alternative to Au. The absorption spectra of the as-synthesized tri-metallic nanocluster reveal that an additional third metal doping can largely affect the electronic structure of the bi-metallic nanocluster. This study also suggests that Ag atoms can be used as an alternative to gold in finding the doping position of other metals such as Cd in gold clusters.2. The catalytic property of alloy nanocluster [Ag46Au24(SR)32](BPh4)2. In this study, we present the structure-determined catalytic results of homometal and alloyed nanoclusters for styrene selective oxidation, by using tert-butyl hydroperoxide (TBHP) as the oxygen source and ethanol as solvent. Homogold Au25/CNT showed the highest conversion of styrene, whereas the selectivity for benzaldehyde is lower. The homosilver Ag44/CNT showed a much lower conversion than the homogold nanocluster did but it exhibited a better selectivity for benzaldehyde. Compared with the homometal nanoclusters, surface doping bimetallic Au24Ag46/CNT catalysts could increase the selectivity for epoxide and give much better conversion than the homosilver nanocluster does. Therefore, the advantages of both the silver (high selectivity for benzaldehyde) and the gold (high conversion) have been well reflected on the surface dopingAg46Au24/CNT catalyst. In contrast, the core-shell structured bimetallic Ag32Aui2 nanocluster shows a much lower benzaldehyde selectivity than does the surface doping catalyst. This finding is remarkable in pioneering investigations on the structure effect in atomically precise alloy nanoclusters and demonstrates a clear synergistic effect of the AgAu alloy catalysts. |
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