Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117585 (Singapore).
Angew Chem Int Ed Engl. 2014 Apr 25;53(18):4623-7. doi: 10.1002/anie.201311177. Epub 2014 Mar 24.
We report a NaOH-mediated NaBH4 reduction method for the synthesis of mono-, bi-, and tri-thiolate-protected Au25 nanoclusters (NCs) with precise control of both the Au core and thiolate ligand surface. The key strategy is to use NaOH to tune the formation kinetics of Au NCs, i.e., reduce the reduction ability of NaBH4 and accelerate the etching ability of free thiolate ligands, leading to a well-balanced reversible reaction for rapid formation of thermodynamically favorable Au25 NCs. This protocol is facile, rapid (≤3 h), versatile (applicable for various thiolate ligands), and highly scalable (>1 g Au NCs). In addition, bi- and tri-thiolate-protected Au25 NCs with adjustable ratios of hetero-thiolate ligands were easily obtained. Such ligand precision in molecular ratios, spatial distribution and uniformity resulted in richly diverse surface landscapes on the Au NCs consisting of multiple functional groups such as carboxyl, amine, and hydroxy. Analysis based on NMR spectroscopy revealed that the hetero-ligands on the NCs are well distributed with no ligand segregation. The unprecedented synthesis of multi-thiolate-protected Au25 NCs may further promote the practical applications of functional metal NCs.
我们报告了一种 NaOH 介导的 NaBH4 还原方法，用于合成单、双和三硫醇保护的 Au25 纳米团簇（NCs），可以精确控制 Au 核和硫醇配体表面。关键策略是使用 NaOH 来调节 Au NCs 的形成动力学，即降低 NaBH4 的还原能力并加速游离硫醇配体的蚀刻能力，从而导致快速形成热力学有利的 Au25 NCs 的平衡可逆反应。该方案简便、快速（≤3 h）、多功能（适用于各种硫醇配体）且具有高扩展性（>1 g Au NCs）。此外，还可以轻松获得具有可调比杂硫醇配体的双硫醇和三硫醇保护的 Au25 NCs。这种在分子比、空间分布和均匀性方面的配体精度导致 Au NCs 表面具有丰富多样的功能基团，如羧基、胺基和羟基。基于 NMR 光谱的分析表明，NCs 上的杂配体分布均匀，没有配体分离。多硫醇保护的 Au25 NCs 的前所未有的合成可能会进一步推动功能金属 NCs 的实际应用。
