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Title: Investigating the Synthesis of Ligated Metal Clusters in Solution Using a Flow Reactor and Electrospray Ionization Mass Spectrometry

The scalable synthesis of subnanometer metal clusters containing an exact number of atoms is of interest due to the highly size-dependent catalytic, electronic and optical properties of these species. While significant research has been conducted on the batch preparation of clusters through reduction synthesis in solution, the processes of metal complex reduction as well as cluster nucleation, growth and post-reduction etching are still not well understood. Herein, we demonstrate a temperature-controlled flow reactor for studying cluster formation in solution at well-defined conditions. Employing this technique methanol solutions of a chloro(triphenylphosphine)gold precursor, 1,4-bis(diphenylphosphino)butane capping ligand and borane-tert-butylamine reducing agent were combined in a mixing tee and introduced into a heated capillary with an adjustable length. In this manner, the temperature dependence of the relative abundance of different ionic reactants, intermediates and products synthesized in real time was characterized using online mass spectrometry. A wide distribution of doubly and triply charged cationic gold clusters was observed as well as smaller singly charged metal-ligand complexes. The results demonstrate that temperature plays a crucial role in determining the relative population of cationic gold clusters and, in general, that higher temperature promotes the formation of doubly charged clusters and singly charged metal-ligand complexes while hinderingmore » the growth of triply charged clusters. Moreover, the distribution of clusters observed at elevated temperatures is found to be consistent with that obtained at longer reaction times at room temperature, thereby demonstrating that heating may be used to access cluster distributions characteristic of different stages of reduction synthesis in solution.« less
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Publication Date:
OSTI Identifier:
Report Number(s):
39717; KC0302020
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A, 118(37):8464-8470
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
Country of Publication:
United States
Environmental Molecular Sciences Laboratory