The Synthesis And Properties Of Noble Metal Nanoclusters

The noble metal materials have attracted attention due to their properties. Mostly, the noble metal is used as catalyst in industry and organic reaction. Therefore more and more chemists focus on the catalytic mechanisms of nanoparticles. Preparing the monodisperse and atom level nanoparticles is in favor of understanding the process of catalysis. The nanoclusters have unique properties due to quantum effect, which are widely used as catalyst. The catalyst can attain the good result of organic reaction and catalytic reaction of CO. Recently, chemists pay attention on gold nanoclusters and synthesizing different size of nanoclusters, but it is hard to figure out what factors affect the growth of nanoclusters. To the platinum nanoclusters, chemists try to synthesize monodisperse and atom level nanoparticles. But it is still a challenge. My thesis focuses on two aspects about nanoclusters materials. First, it is important to understand the growth process of nanoclusters and to study what kind of factor will affect the growth of nanoclusters. Second, we explore the structure of nanoclusters in order to explain the relationship between the size of nanoclusters and their properties.1、We report an finding that the reaction medium plays a major role in influencing the final nanoclusters size. Specifically, we focus on the one-phase synthetic process that leads to predominant formation of Au25(SR)18or Au144(SR)6o-two ubiquitous nanoclusters in nanocluster synthesis. When THF, acetone or ethyl acetate was used as the reaction solvent, we found that Au25was formed as the major product, while in methanol or acetonitrile, predominant Au144and some larger nanoparticles were formed. We mapped out some details of the underlying growth mechanism of nanoclusters, in which the reaction medium was found to affect the Au (I) intermediate, which subsequently affects the final size of gold nanoclusters.2、We prepare gold nanoclusters using "sizing focus" method. This gold nanocluster is atom level monodispersed with38gold atoms. It noted that we obtained the crystal of gold nanolcusters. The structure of crystal was determined. Au38contains Au6core and Au32shell. It was the first time to report that the gold nanoclusters have Au6as core. The crystal has unique absorption spectra and strong fluorescence. The crystal structure of gold nanoclusters helps us to further study the mechanics of metal catalyst and its catalytic application.3、Platinum nanoclusters with a mass at8kDa were synthesized for the first time using an one-phase organic solvent method. By controlling the reaction parameters, we identified the optimal reaction conditions to obtain the Pt nanoclusters with mass focused on8kDa. The results show that the Pt nanoclusters are unstable when they are etched, oxidized and thermally processed. The structure of Pt nanoclusters is still the face center cubic structure even ultrasmall size is about1nm.4、We selected the platinum nanoclsters with a few atoms as catalyst that was prepared with modified Burst method. The catalyst was applied in catalyzing CO. The catalyst has high catalysis efficiency for CO. The platinum nanoclusters start to work when the reaction temperature was rise to460K. Compared to lnm nanoclusters, the catalysis temperature of2nm nanoparticles rise to500K, the catalyst starting work. We are still studying the mechanics of noble metal nanoclusters.