Abstract
Fine metal clusters have attracted much attention from the viewpoints of both basic and applied science for many years because of their unique physical/chemical properties and functions, which differ from those of bulk metals. Among these materials, thiolate (SR)-protected gold clusters (Aun(SR)m clusters) have been the most studied metal clusters since 2000 because of their ease of synthesis and handling. However, in the early 2000s, it was not easy to isolate these metal clusters. Therefore, high-resolution separation methods were explored, and several atomic-level separation methods, including polyacrylamide gel electrophoresis (PAGE), high-performance liquid chromatography (HPLC), and thin-layer chromatography (TLC), were successively established. These techniques have made it possible to isolate a series of Aun(SR)m clusters, and much knowledge has been obtained on the correlation between the chemical composition and fundamental properties such as the stability, electronic structure, and physical properties of Aun(SR)m clusters. In addition, these high-resolution separation techniques are now also frequently used to evaluate the distribution of the product and to track the reaction process. In this way, high-resolution separation techniques have played an essential role in the study of Aun(SR)m clusters. However, only a few reviews have focused on this work. This review focuses on PAGE, HPLC, and TLC separation techniques, which offer high resolution and repeatability, and summarizes previous studies on the high-resolution separation of Aun(SR)m and related clusters with the purpose of promoting a better understanding of the features and the utility of these techniques.
Highlights
Fine metal clusters smaller than ∼2 nm (≲100 atoms) exhibit different geometrical/electronic structures than those of bulkYuichi Negishi: Professor at the Department of AppliedChemistry at Tokyo University of Science
This review focuses on polyacrylamide gel electrophoresis (PAGE), high-performance liquid chromatography (HPLC), and thin-layer chromatography (TLC) separation techniques, which offer high resolution and repeatability, and summarizes previous studies on the high-resolution separation of Aun(SR)m and related clusters with the purpose of promoting a better understanding of the features and the utility of these techniques
This review summarized previous research on the high-resolution separation of Aun(SR)m and related clusters by focusing on PAGE, HPLC, and TLC
Summary
Fine metal clusters smaller than ∼2 nm (≲100 atoms) exhibit different geometrical/electronic structures than those of bulk. Separation techniques that relied on the differences in the solubility of solvents were mainly used.[34,35,36,37,38] atomiclevel separation techniques, such as polyacrylamide gel electrophoresis (PAGE) and liquid chromatography (LC) were developed These methods made it possible to isolate a series of Aun(SR)m clusters and obtain knowledge on the correlation between the chemical composition and the fundamental properties (e.g., stability,[39,40] electronic structure,[41] and physical/ chemical properties42,43) of Aun(SR)m clusters. The use of high-resolution separation techniques remains indispensable for understanding the correlation between the chemical composition and structure/physical properties of SR-protected metal clusters. PAGE is useful for evaluating the product size and shape because the mobility of each metal cluster varies depending on the particle size and shape as well as the charge and the interaction with the solvent
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