Precise control of alloying sites of bimetallic nanoclusters via surface motif exchange reaction

Qiaofeng Yao,Victor Fung,Jun Yang,Yong Yu,Yan Feng,Jianping Xie,De-En Jiang

doi:10.1038/s41467-017-01736-5

Abstract

Precise control of alloying sites has long been a challenging pursuit, yet little has been achieved for the atomic-level manipulation of metallic nanomaterials. Here we describe utilization of a surface motif exchange (SME) reaction to selectively replace the surface motifs of parent [Ag44(SR)30]4− (SR = thiolate) nanoparticles (NPs), leading to bimetallic NPs with well-defined molecular formula and atomically-controlled alloying sites in protecting shell. A systematic mass (and tandem mass) spectrometry analysis suggests that the SME reaction is an atomically precise displacement of SR–Ag(I)–SR-protecting modules of Ag NPs by the incoming SR–Au(I)–SR modules, giving rise to a core-shell [Ag32@Au12(SR)30]4−. Theoretical calculation suggests that the thermodynamically less favorable core-shell Ag@Au nanostructure is kinetically stabilized by the intermediate Ag20 shell, preventing inward diffusion of the surface Au atoms. The delicate SME reaction opens a door to precisely control the alloying sites in the protecting shell of bimetallic NPs with broad utility.

Highlights

Precise control of alloying sites has long been a challenging pursuit, yet little has been achieved for the atomic-level manipulation of metallic nanomaterials
Ag NCs are a promising class of functional materials with potential applications in the biomedical field, e.g., as efficient broad spectrum antimicrobial agents[51]
Ag NCs with Au heteroatoms is an efficient way to address this stability issue[38]; if the Au atoms could be placed on the surface of Ag NCs, it could largely prohibit the interactions of Ag atoms inside the bimetallic

Summary

Introduction

Precise control of alloying sites has long been a challenging pursuit, yet little has been achieved for the atomic-level manipulation of metallic nanomaterials. We describe utilization of a surface motif exchange (SME) reaction to selectively replace the surface motifs of parent [Ag44(SR)30]4− (SR = thiolate) nanoparticles (NPs), leading to bimetallic NPs with well-defined molecular formula and atomically-controlled alloying sites in protecting shell. Nm regime possess strong quantum confinement effects and exhibit some intriguing molecular-like properties, such as highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) transition[11,12], quantized charging[13], intrinsic chirality[14,15], strong luminescence[16,17,18,19,20], and enhanced catalytic activity[21,22,23] These properties are inherently (and sensitively) dictated by the size and composition of metal NCs24–29. Bootharaju et al.[46] developed an efficient way to dope a single-Au heteroatom into the center of [AAgg1235(ScRo)r1e8]−o. fIn [Ag25(SR)18]− by reacting these successful attempts, Au

Methods

Results

Conclusion