Evolution of thiolate-stabilized Ag nanoclusters from Ag-thiolate cluster intermediates

Yitao Cao,Jinheng Pan,Geoffrey I N Waterhouse,Li-Zhu Wu,Zhenxia Du,Tierui Zhang,Jianping Xie,Run Shi,Qiaofeng Yao,Chen-Ho Tung,Jiahao Guo

doi:10.1038/s41467-018-04837-x

Abstract

The synthesis of atomically precise thiolate-stabilized silver (Ag) nanoclusters is the subject of intense research interest, yet the formation mechanism of such nanoclusters remains obscure. Here, electrospray ionization mass spectrometry is successfully applied to monitor the reaction intermediates formed during the sodium-borohydride-reduction of silver 4-tert-butylbenzenethiolate (AgSPh-tBu). We demonstrate a unique evolution route to thiolate-stabilized Ag nanoclusters mediated by Ag-thiolate clusters. The Ag-thiolate clusters form in the initial stage of reduction contain tens of Ag atoms and similar number of ligands, and they are transformed into Ag17(SPh-tBu)123− and Ag44(SPh-tBu)304− nanoclusters in the later reduction process. The number of Ag atoms in the Ag-thiolate clusters determines the reaction path to each final nanocluster product. A similar mechanism is found when silver 2,4-dimethylbenzenethiolate (AgSPhMe2) is used as precursor. This mechanism differs markedly from the long-established bottom-up evolution process, providing valuable new insights into the synthesis of metal nanoclusters.

Highlights

The synthesis of atomically precise thiolate-stabilized silver (Ag) nanoclusters is the subject of intense research interest, yet the formation mechanism of such nanoclusters remains obscure
We demonstrate the successful identification of intermediates in the evolution process of atomically precise thiolatestabilized Ag nanoclusters by electrospray ionization mass spectrometry (ESI-MS), thereby allowing the establishment of a unique evolution mechanism
Our results offer a highly plausible explanation for the non-seeding properties of Ag nanoclusters, since the evolution of Ag44 nanoclusters is based on a process from discrete Ag-thiolate cluster intermediates, a pathway that prevents the growth of larger nanoclusters

Summary

Introduction

The synthesis of atomically precise thiolate-stabilized silver (Ag) nanoclusters is the subject of intense research interest, yet the formation mechanism of such nanoclusters remains obscure. We demonstrate the successful identification of intermediates in the evolution process of atomically precise thiolatestabilized Ag nanoclusters by electrospray ionization mass spectrometry (ESI-MS), thereby allowing the establishment of a unique evolution mechanism. Instead of forming monomers or oligomers followed by bottom-up evolution process as reported for Au nanoclusters[31], the reduction of the Ag-thiolate complex precursor, silver 4-tert-butylbenzenethiolate (AgSPh-tBu), generates discrete Ag-thiolate clusters containing tens of Ag atoms and similar number of thiolate ligands (i.e., a similar Ag:thiolate composition to the Ag-thiolate precursor). Our findings indicate that the size (number of Ag atoms) in the intermediate Ag-thiolate clusters plays a critical role in the reaction routes to the different thiolate-stabilized nanoclusters with the same capping ligand

Methods

Results

Conclusion