On the stability of noble-metal nanoclusters protected with thiolate ligands

Abstract

PACS 61.46.Bc -Structure of clusters (e.g., metcars; not fragments of crystals; free or loosely aggregated or loosely attached to a substrate) PACS 68.43.Hn -Structure of assemblies of adsorbates (two-and three-dimensional clustering) Abstract -Noble metal nanoclusters (NCs) protected with thiolate ligands have been of interest because of their long-term stability that makes them suitable as building blocks for diverse assembled systems with emergent and improved functions. Despite the advances in synthesis and characterization, the mechanisms that contribute to their stability are still poorly understood. In this article, we review the different criteria that have been used to explain the experimental stability of NCs with a well-defined number of atoms that are protected with thiolate ligands. We discuss why these criteria are not enough to explain the stability. We conclude that there are other physical factors that should be included when explaining the stability of these systems and could be important for the discovery of new noble-metal NCs.

Predicting absorption spectra of silver‐ligand complexes

“…Ligand protected metal nanoclusters (NCs) have gained much attention in the last decade due to their unique physicochemical properties. These metal NCs typically measure less than 2 nm . Electronic, chemical, and optical properties of NCs differ from both bulk and atomic scale materials.…”

“…The nature of the ligand seems to have a strong effect on fluorescent properties of noble metal NCs . Noble metal NCs protected with thiolate ligands have been of interest because of their long‐term stability, which allows one to use them as building blocks constructing assembled systems with novel and improved functions . Silver‐thiolate and silver‐amino acid complexes are studied in many laboratories nowadays both theoretically and experimentally .…”

Electronic structure and charge compensation in AuxAg25-xSR181− (x = 0, 12, 13, 25), AuAg12Au12SR181−, and AgAu12Ag12SR181− clusters

“…However, clusters such as Au 20 (SR) 16 , Au 36 (SR) 24 , and Au 44 (SR) 28 have been synthesized (Zeng et al 2014a(Zeng et al , 2014b despite not fulfilling the superatom rule. Within this context, it is necessary to understand the role of the ligand nature and the metal core since the above criteria do not discriminate between different thiolate ligands or metal atoms with similar electronic structures, as gold and silver atoms (Morera-Boado et al 2017).…”

Stability and Electronic Charge Compensation of [Ag44–xAux(SR)30]4– Clusters

“…For example, clusters such as Au 20 (SR) 16 , Au 36 (SR) 24 , and Au 44 (SR) 28 have been synthesized, − but they do not fulfill the above criteria. Besides, the role of the ligand nature and the metal core composition have not been widely studied, while the above criteria do not discriminate between different thiolate ligands or metal atoms with similar electronic structure as gold and silver atoms . However, there are some clusters that have been obtained experimentally only with specific ligands, such as the [Ag 44 (SR) 30 ] 4– case, where all ligands involve phenyl groups; ,− while other clusters, such as [Ag 25 (SR) 18 ] − and [Au 25 (SR) 18 ] − , have been obtained with different thiolate ligands. − …”

“…Besides, the role of the ligand nature and the metal core composition have not been widely studied, while the above criteria do not discriminate between different thiolate ligands or metal atoms with similar electronic structure as gold and silver atoms. 13 However, there are some clusters that have been obtained experimentally only with specific ligands, such as the [Ag 44 (SR) 30 ] 4− case, where all ligands involve phenyl groups; 7,14−19 while other clusters, such as [Ag 25 (SR) 18 ] − and [Au 25 (SR) 18 ] − , have been obtained with different thiolate ligands. 20−25 Now, it is possible to control the synthetic routes in the desired way by changing the reaction conditions such as the reducing agent, solvents, and ligands to obtain different stoichiometries.…”