Studying the Growth of Gold Nanoclusters by Sub-stoichiometric Reduction

Abstract

Summary: Sub-stoichiometric reactions are powerful tools for mechanistic analyses because they can stabilize key intermediates in chemical reactions. Here, we develop a multiple-step, sub-stoichiometric reduction platform that can precisely dope required electrons to synthesize atomically precise gold nanoclusters (Au NCs). Only a sub-stoichiometric amount of NaBH4 (equivalent to doping one valence electron into Au NCs) is introduced in each step. In 8 successive steps, we identify a series of stable intermediates whose relative abundance suggests a different growth pathway from previous reports. In addition, detailed analysis of 120 real-time mass spectra during the formation process reveals three meta-stable species. Moreover, the platform also sheds light on the structural evolution of Au NCs during the growth process. This method provides a platform for studying the molecular- and atomic-level evolution of metal NCs (in both size and structure), revealing the reaction dynamics of NC intermediates toward the formation of atomically precise metal NCs.

Keywords

• mass spectrometry
• metal nanoclusters
• Au nanoclusters
• metal nanoparticles
• sub-stoichiometric reactions
• valence electron