Preparation of high-yield and ultra-pure Au25 nanoclusters: towards their implementation in real-world applications

TL;DR

This paper develops purification methods for Au25 nanoclusters, significantly improving yield and purity, and analyzes synthesis factors to enable their practical application in real-world scenarios.

Contribution

It introduces three purification techniques for Au25 nanoclusters and identifies critical synthesis parameters, including residual water and etching duration, to enhance yield and purity.

Findings

Purification methods effectively separate Au25 NCs from byproducts.

Optimized synthesis yields up to 40%.

Residual water and etching time are critical factors.

Abstract

Colloidal approaches allow for the synthesis of Au nanoclusters (NCs) with atomic precision and sizes ranging from a few to hundreds of atoms. In most of the cases, these processes involve a common strategy of thiol etching of initially polydisperse Au nanoparticles into atomically precise NCs, resulting in the release of Au-thiolate complexes as byproducts. To the best of our knowledge, neither the removal of these byproducts nor the mass spectra in the relevant mass region were shown in previous studies. A thorough analysis of inorganic byproducts in the synthesis of Au25 NCs reveals that published protocols lead to Au25 NCs in vanishingly small quantities compared to their byproducts. Three purification methods are presented to separate byproducts from the desired Au25 NCs which are proposed to be applicable to other promising Au NC systems. Additionally, critical factors for a successful synthesis of Au25 NCs are identified and discussed including the role of residual water. An important finding is that the etching duration is very critical and must be monitored by UV-Vis spectroscopy resulting in synthetic yields as high as 40%.